Google+

GrantCunningham.com

© 2014 Grant Cunningham Click to email me!

The bullet jump controversy.


I got an email recently from a reader who asked about .38 Special accuracy when fired in a .357-length chamber. There is, as he noted, a lot of speculation on the topic: some saying they're less accurate, some saying it doesn't matter, and others saying that there is no way we'll ever know for sure.

I'm not at all convinced about that last one, but the first two opinions are both correct - under some circumstances. Some years ago I experimented with this, and what I found comes under the heading of "it depends."

The concern is that the unrestrained jump of the bullet from the shorter Special case causes instability and thus inaccuracy. A Magnum chamber is longer from the rim seat (the area at the back of the cylinder where the rim makes contact) to the chamber throat (the narrow area at the front of the cylinder that guides the projectile into the barrel.) When a Special cartridge is inserted into the longer chamber, the bullet has to travel a distance (called "jump") before it reaches the narrower throat. In this distance, it's thought, the bullet can yaw slightly.

I've done up this little graphic (greatly exaggerated and not to scale) to illustrate the situation:



Notice the area between the bullet and where the chamber mouth begins - that's the freebore area where the bullet's travel is unrestrained and, according to theory, starts to wobble to the detriment of accuracy.

A number of years back I did some experimenting by loading the same bullets in .357 Magnum and .38 Special cases, and adjusting the velocity so they matched. I found that sometimes the Specials did show a loss of accuracy, while at other times they didn't. (I had one case where accuracy with Specials actually improved.) Why the variance? If the bullet jump is responsible for accuracy degradation it should be consistent, and it certainly wasn't.

The answer is that the freebore is only part of the equation.

As I've written before, one of the most important contributors to accuracy in a revolver (and the MOST important when shooting lead bullets) is the chamber throat. Assuming that the bore diameter is correct, a throat which fits the bullet precisely will deliver greater accuracy than one which is oversized (or undersized to a great degree.)

If the throat is larger than the bullet diameter - say, .001" or better - accuracy drops off. If the throat and bullet match, accuracy will generally be at its best. If the throat is slightly (up to .001") smaller than bullet diameter, jacketed bullets will usually show a falloff in accuracy but lead bullets usually won't, at least not to the same degree. (More testing is needed in this area, however, as I don't have enough data points with smaller-than-bullet throats to reach a definite conclusion.)

When the throat diameter was the same as the bullet diameter, there was generally little to no difference in accuracy between the long and short. When the throat diameter was larger, however, the Specials were usually less accurate than the longer cases. Someone doing the same experiment but not taking into account throat/bullet diameter matching would probably reach different conclusions, which I believe is the source of the varying opinions and the reader's confusion.

More experimentation should be done, however, to eliminate other variables such as the angle of the transition between chamber and throat and any surface irregularities in that area.

I also would expect the same dynamics to apply to larger calibers such as the .44 Magnum and Special, though I have no experimental data to prove my supposition.

-=[ Grant ]=-

Comments

What happens when a competitor goes to a tactical conference?


He discovers that maybe he didn't know as much as he thought he did.
Great writeup of the NE Shooters' 2011 Summit over at The Tactical Wire.

-=[ Grant ]=-
Comments

A crowning achievement.


Occasionally someone will ask me if the muzzle crown is all that important. In the past I'd probably say something like "only if you want the bullet to go where you're aiming!", but I'm trying to reduce my percentage of flippant answers. Today I'd put it more lawyer-like: "it depends..."

The crown is the edge of the bore at the muzzle. It's important to point that out, because it's not unlike the edge of a cliff. Once you've fallen over the edge, you have no chance to change your path (unless you're Icarus, in which case I'd really like to talk to you.) The edge of the bore, where the rifling ends, is likewise the last chance for the barrel to properly direct the path of the bullet.

The edge needs to be perfectly perpendicular to the axis of the bore; if it's not, as the bullet leaves the barrel one side might be clear of the barrel, but the opposite side will still be touching. This can introduce instability to the bullet, reducing the accuracy of the shot.

Even when correctly squared, a crown with a nicked edge can have the same effect. If the last thing that touches the bullet imparts any directional friction, like a nick or burr, the bullet path will be compromised.

It's amazing now small an imperfection can affect the accuracy of a barrel. I recently had a battle of wills with a Mossberg M44US rifle. This was a target .22 that Mossberg sold on contract to the U.S. military back in the late 1940s. They have a reputation for being quite accurate, and every example I've ever shot held up that reputation - except this one.

I could not get a decent 5-shot group out of the gun to save myself. I tested 15 different loads in the gun, went over it with a fine-tooth comb, and still got flyers in every group. I looked at the crown, and it seemed perfectly fine, but still the gun wasn't accurate. After exhausting every other possibility, I decided to recrown the barrel.

The edges of the bore seemed fine, but the first pass with the crowning reamer told the story: the crown was ever so slightly crooked. We're talking perhaps a couple of thousandths of an inch, which isn't a lot. I cut a perpendicular crown, and took the gun to the range.

Night and day.

The gun now shot like a 44US is supposed to! Beautiful groups from Wolf Match Target (aka SK Standard Plus, aka Lapua SC), which had shot no better than cheap Remington bulk prior to the recrowning. The crown had seemed to be a non-issue, even under magnification, but before and after targets proved that even tiny imperfections can make a huge difference.

-=[ Grant ]=-
Comments

Still more about testing .22 long rifle ammunition.


A recent email asked about
an old article, wherein I talked about the problems with residual lube in a .22 rimfire barrel. Is it really a problem, the email asked, and if so how do I go about eliminating that variable in testing?

Yes, the effects are real. I never believed in the residual lube theory until I saw the results for myself, and to this day I can repeat them at will with that rifle and ammo.

My test protocol now is to use a standard smallbore target, the type with 6 bullseyes on a sheet. The upper left corner is used to fire 25 seasoning rounds, without regard for group size. This both burns off any residual lubricant and allows me to make any sight adjustments to bring the rounds fairly close to center. I then fire a 5-round group at each remaining bullseye, which gives a good average of the groups that ammunition will deliver. If you're counting, that's one single box of ammunition on one sheet of paper.

Rimfire purists will point out that this is not a sufficient number of rounds to really ascertain the true performance of any specific load, and I'll admit that subsequent testing will sometimes show small differences in group size (better or worse) than this. If you're a serious rimfire match shooter, you'll need to fire hundreds of rounds to truly judge what the ammunition will do. Of course, if you are that person you also won't be looking here for advice!

I've found my test procedure to be the easiest, fastest, most reliable method to obtain a decent (field-grade) indicator of relative performance of rimfire ammunition.

-=[ Grant ]=-
Comments

More on testing .22 Long Rifle ammunition.


As I've mentioned from time to time, shooting .22LR "seriously" can be a frustrating experience. It is almost expected that two identical rifles will have very different ammo preferences - and, unlike centerfire cartridges, the differences are often astounding.

For instance, I have one rifle that shoots it's favorite load into an average 5-shot group of .275" at 25 yards (from prone.) However, that same rifle shooting it's least favorite load struggles to maintain 3" at that same distance! What's more, once you find that one load that shoots well in that one gun, the next batch (lot) of that same ammo may not. It will never be as bad as the best to the worst comparison, but the variance can be enough to put the next best (or sometimes the third best) in the top spot - until you change lots again, of course!

Finding the gun's favorite load is strictly a matter of trial and error. It's not usually even a matter of the type of load; for instance, a gun might shoot one particular 36 grain high velocity hollowpoint load very well, but the next maker's similar fodder won't be even close.

Those who are serious about their rimfires, therefore, tend to do a lot of ammunition testing. When I acquire a new .22, I'll run as many as 20 different kinds of ammo through it, keeping careful notes about the results. This takes time, and if not done correctly results in meaningless data!

As you probably know, .22 ammunition is externally lubricated. That is, each bullet has a coating of some kind of lube to keep it from fouling the bore. Each maker uses a different lube, and sometimes they'll use different lubes within their own product line.

The problem is that residual lube from one load can affect the next few rounds using another load. Case in point: some time back I was testing a new rifle with a couple of different loads. I had just finished with Wolf Match Target, and loaded in some much cheaper Federal stuff. The first 5-shot group with the Federal was absolutely astounding - an honest .175" group at 25 yards! I don't know which amazed me more, the rifle or the ammo, but I wanted to do it again!

I loaded another magazine, "assumed the position", and shot another group. This one was slightly larger, which I attributed to me. I repeated the procedure, and this time the group had almost doubled in size. The next one was even worse.

What accounted for that first group? After thinking about it, and reading some information from Steven Boelter (whose rimfire experience dwarfs mine), I came to the conclusion that perhaps there was some residual lubricant from the Wolf ammunition which was "contaminating" (but in a good way) the Federal load. Testing my hypothesis was easy: I shot a few magazines of Wolf, then switched to the Federal. The first group of Federal was, again, under .200" for 5 shots. The following groups deteriorated rapidly, just as they had the first time. A repetition of the sequence duplicated the results. It seemed that the Wolf lubricant affected the Federal rounds in a good way, but as it was rapidly depleted from the barrel the groups suffered.

From this I adopted the rimfire shooter's testing procedure: when switching loads, first clean the bore (a quick brushing will suffice.) Then, shoot 1 round of the new load for each inch of barrel length to "season" the barrel to the new ammo before firing any groups that will count. This is Boelter's recommendation, and I've found it to be sage advice. Remember: only after the seasoning rounds have been fired do you shoot any for score or analysis.

Those first few rounds may group better, or worse, than the shots following. It doesn't matter, because the groups made after the seasoning process are the ones that tell you what the load really, truly does in that gun.

-=[ Grant ]=-
Comments

Systems analysis and the sighting-in of firearms


This weekend was the opening of general deer season here in Oregon. I could tell it was opening weekend, because our normally deserted gravel road, which leads into the mountains, has been turned into Interstate 5 for deer hunters! The parade of all the hopeful woodsmen (and perhaps not a few woodswomen) going after Bambi made me realize I'd missed something this year: hunter's sight-in at our gun club.

You see, last January my wife and I bought a new place. When we moved we gave up our club memberships, as a) the club is now 60 miles away, and b) we can shoot all we want on our own property. I don't miss the club, but I do miss the circus-like atmosphere of sight-in days. I actually enjoyed helping out those whose shooting skills were not, shall we say, fully developed. They needed all the help they could get!

(Sight-in days at our former club is a big event. It occupies every full weekend for a solid month; it's not unusual to have several hundred guns per day go through the system, as the club is one of the few rifle ranges within easy driving distance of the Portland, OR metro area. Working at sight-in means long days and lots of activity.)

In recent years I worked sight-in alongside my friends Georges and Maurice, who got the same kick out of the event that I did. We kept a running tally of the best, worst, and most over-gunned shooters on the line. During the lulls we'd trade stories of the unusual incidents we'd had, and not all of them were with customers!

One particularly busy day I had a run-in with one of the folks who served as Assistant Chief Range Officer for the event. I was helping a middle-aged fellow who'd arrived toting a .30-06 of unremarkable (though completely serviceable) pedigree. He showed me his gun, his ammo, and sat down at the bench. The club provided sandbags and front rests for the guns, but this fellow didn't want to use them. "My zero is different if I shoot from a bench than from my hands, so I'd just like to rest my elbows on the table." That was fine with me; this fellow had obviously been around the block more than once and thus knew what he was doing. (His target would later prove my analysis to be correct.)

He had just fired his second round when the aforementioned RO came rushing up. "He needs to use the rest", he sputtered. "He'll never know if he's properly zeroed shooting from his hands!" I told him that the customer knew his own needs, and that I admired the fellow for obviously knowing more than the average schmuck who came through the door.

This annoyed the RO to no end; he wanted to argue with me, insisting that I was a complete fool for letting the customer do this. I simply smiled, waved him away, and went back to my job.

The RO in question, like many, was confused about the reason we sight in a firearm. The goal of sight-in is to get all parts of the weapon system - the gun, ammo, sights, and shooter - in alignment so that the bullets land where desired. If we take away - isolate - any part of that system, we have removed a functioning part that will affect the outcome. The outcome is what we're testing! We're not testing the scope (which is what this RO was convinced we were doing), or the ammo, but the results that they - together with the shooter - produce. We have to test all parts of the system in concert, so that we can see if the goal is being met.

Let's say that we were to test the system using sandbags and a bench. There are very few rifles made that will have the same zero point no matter how the gun is suspended; the points at which the suspension occurs, the amount of pressure on the suspension points, the direction of that pressure, and even the resulting direction of recoil will all change when the gun is taken off the bench and shot from a field position. All of those will change the landing point of the bullet, sometimes dramatically.

Now consider the shooter's input. The head position from a bench is different than it is from standing (or even sitting or kneeling, and especially from prone.) The shooter's eye will not be in the same place relative to the sights or scope; the cheek weld point will be different; the shoulder will be further forward or backward, depending on the physique of the shooter. The shooting hand will shift position slightly, leading to a different grip pressure and direction of pull on the trigger. Think any of those might affect the outcome of the shot? You bet they will - all of 'em.

Change enough of those inputs, and you'll end up with a system that won't shoot to the same point of aim under the expected conditions. We need to check the system's alignment (gauged by the impact point of the bullet) under the conditions in which it will be used. For hunting, that means "not from a bench rest."

An extreme example of this can be found simply by looking at G. David Tubb's rifle. For those who don't know, he shoots with the rifle held at an angle, which is very different than what we were all taught to do! That doesn't matter, though, because he's set his sights to hit correctly with that unorthodox hold. Imagine we "isolated" his rifle; put it on a bench, cradled it level in sandbags, and proceeded to "zero" the gun. Guess what? It wouldn't hit the correct point, because it wouldn't be held in the position in which Tubb shoots the thing. Given his modest success at highpower competition (!), I'd say he knows what he's doing!

One day I was visiting one of the very best handgun trainers I know. I picked up her gun and was surprised to see her sights drifted quite a ways to the right. I thought that odd, but she pointed out that they were that way because that's where they had to be to allow her to hit where she wants the gun to hit. Given that she can regularly clean the clocks of just about any male shooter - some of them state and regional champions - at will, I'd say her system is working perfectly. That's all that matters!

Are there times when we want isolation? Certainly - when we're testing specific parts of the system. Comparing one load to another, for example, demands an isolated gun; we don't care exactly where the rounds hit, because we're interested in the differences between two inputs of the same type. In order to see those differences, we have to eliminate all other variables that might obscure them.

Sighting in, on the other hand, is all about the whole system. To align the system, we need all of its parts to be working as they normally do. The fellow on the line that day understood the concept; the RO didn't.

There is no substitute for thinking about what you're doing, and why you're doing it.

-=[ Grant ]=-
Comments

Unintended consequences of riflestock design


This weekend I was working around the farm on a particularly labor-intensive project. It got to be about noon, and the rapidly rising temperatures (there was no shade where I was working) convinced me to take the afternoon off and go shooting.

I decided to take my "sport utility rifle", which is a .22LR Marlin 39a. This is the gun that stays loaded all the time, as a .22 goes with farm livin' like beer goes with NASCAR. (I neither drink beer nor watch NASCAR, but
Jeff Dunham says so and that's good enough for me.) I'd recently replaced the bead front sight with a plain front post from Skinner Sights, and wanted to see if the new sight picture would significantly improve the usable accuracy.

Along with the rifle and it's usual ammunition, I took some smallbore targets and a few paintballs. (There was a recent thread over at
RimfireCentral forums about shooting "fun" targets, and paintballs were a common choice. I don't own a paintball gun, but I now own a box of paintballs!)

After setting up the bullseyes I flopped down to a solid, comfortable prone position and fired my first two groups. I've been shooting iron-sighted target rifles for the past few weeks with great success, so when I walked down to check the target I was stunned at what I saw. Both groups were about three times the size I expected, and centered about an inch-and-a-half high and about the same amount to the left. Well, at least I was consistent!

Keep in mind that this is a gun that gets shot regularly on the plinking range, and never has it shown any tendencies such as I'd just seen. I decided that it was me, and if I did something else for a little while and came back to the rifle I'd be fine.

When I picked up the rifle a half-hour later I decided on a "quick and dirty" test: I'd shoot a few of those little paintballs (which are just a tad over a half-inch in diameter) from the 25 yard line. I set up the bright spheres, took a solid kneeling position and started shooting. The first shot connected and produced a nice orange mist; I pulled the second shot, but the next connected; the last two went just as planned - two more dead paintballs.

This was odd: I could hit these half-inch balls consistently, but if they'd been paper targets I'd have missed completely! It must have been me after all. I flopped down to prone to re-shoot those groups.

Imagine my surprise when I again found two-inch groups, high and to the left! What in the world was going on? Position obviously was a factor; I reshot the groups, this time from my kneeling position. Perfectly centered, and less than half the size of the prone shots.

After thinking about it for a while, it became clear that the problem was a sight issue. The receiver peep sights I have on the gun work better the closer one's eye is to the aperture (which is true with any peep sight.) The further back the eye is from the peep, the less effective that type of sight is.

The design of the Marlin's buttstock was preventing me from getting my eye sufficiently close when prone, but not so much when my body was more upright. The comb of the stock is a bit low, and the point is quite narrow and far back; when in a normal, unstressed prone position it put my eye further back from the aperture than is optimal.

The result was that the "self centering" aspect of the peep sight was reduced, and the depth of field (sharpness about the front sight) was reduced as well. This caused my groups to open up and shift. I found that if I contorted my prone position I could get my eye a bit closer to the sight. That helped with the sight picture but the resulting muscle tension made it impossible to hold steady on target, making the situation even worse.

The ironic part of this is that, had I been using the open sights the gun came with, it wouldn't have been an issue. Eye position is not a factor with the notch-and-bead sights the factory puts on the gun. By putting on the receiver peep sight, I'd changed the interaction of the various parts of the gun's design, and the weakness appeared.

The Marlin stock is great for snap-shooting; looking at it next to a shotgun, one notices similarities in shape and dimensions. Both are designed for efficiency in upright shooting positions, but are less than optimal when the upper body moves to a horizontal plane. The folks who designed the 39a made a great gun, and by introducing a new sighting system I'd bumped into the limitations of their design.

This episode has helped me understand how the elements of a rifle stock design interact with the shooter. I already know (from hard experience) that a Monte Carlo stock design has serious problems with certain shooting positions (particularly in prone), but I hadn't stopped to consider all the other little intricacies.

Even after 40-plus years on this planet, I learn something new every single time I go to the range!

-=[ Grant ]=-
Comments

Preventing barrel leading


A reader asked me to comment on successfully shooting lead bullets in revolvers. It seems that he's been getting indifferent accuracy coupled with severe leading, and would like to know the "secret" to using lead in his gun.

I thought I'd covered this topic once before, but a thorough search of the archives failed to turn up the expected article. Guess I'll have to do this from scratch!

Please note that I'm not a "hardcore" cast bullet shooter. I don't cast my own, which means that I'm dependent on commercial sources for my projectiles. As a result, it's taken me longer to learn this stuff than it would have otherwise. Thus I'm no expert; but Ed Harris, who sometimes checks in here at the RLA, is - hopefully he'll see fit to comment. (Ed, if I get anything wrong please drop me a note - I'll make your response into it's own post.)

The first thing to understand is that your lead bullets need to fit the chamber throats of your gun. If, for example, your throats measure .358", your bullets should be no smaller than .358, and no bigger than .001" over that measurement. Smaller bullets won't be as accurate, and will let the erosive combustion gases blow past the bullet causing severe leading around the forcing cone.

(Many bullet makers will size their products to your preference; if they don't make that service obvious, just ask. A surprising number are happy to oblige, usually at no extra cost.)

The forcing cone of your gun must also be in good condition; roughness in that area will result in leading at that point.

Assuming that the gun part of the equation is in good shape, and the bullets are of correct size, the hardness of the bullet becomes the critical issue. Most bullet makers advertise really hard bullets as being the "cure" for leading. It sort of stands to reason, doesn't it? A harder lead won't smear as much as it goes down the barrel, and will leave less residue - right?

Guess what - it isn't true. In fact, it's completely off base!

Think about this: you probably have a .22 rifle hanging around. Most .22 LR bullets are plain lubricated lead - very soft lead, no less. Compared to your average hard cast bullet, a .22 slug is almost like butter - soft as can be. Yet I'll bet that if you looked at the bore of your rifle, you probably won't see much leading - if any at all. My .22 rifles will fire a thousand or so rounds between cleanings, and I've never seen lead in my bores despite the bullet traveling at 1,200 fps.

What's the reason? Obturation.

A bullet, under great pressure from the expanding gases behind it, grows in size to fit whatever hole (chamber throat, barrel bore) it is being shoved into. This phenomenon is called obturation. As the bullet obturates it seals the hole, and keeps the gases where they belong until the bullet actually exits the barrel.

If the bullet doesn't obturate, the very hot gases will rush past while it is in the bore. The lead where the gases pass is melted and deposited on the barrel's walls - producing leading. This kind of leading is the most difficult to remove, as it really "sticks" to the bore - as if it's been soldered there. In fact, it has!

It follows that we need to make sure that they bullet obturates in our bore. In order for a bullet to obturate, the metal used needs to be soft enough to deform easily under the amount of pressure being applied to it. If the bullet is too hard, it won't obturate and there will be no sealing.

So, the bullet has to be soft enough to obturate. Why not just make all bullets out of super soft pure lead - won't that cure the problem? No, it won't; a bullet that's too soft will also cause leading, as it won't be strong enough to maintain the necessary seal in the bore. It also won't be resistant to the heat generated by the friction of travel down the bore. Both result in lead left in the barrel.

The bullet has to be hard, but not too hard; soft, but not too soft! The variable is the amount of pressure generated by the firing cartridge.

The higher the pressure, the harder the bullet needs to be to resist excess deformation - but remember that it has to be soft enough to obturate properly. A mild .38 Special target load needs a softer bullet than a fire-breathing .357 Magnum in order to obturate; putting a too-hard bullet in a mild cartridge is as much a problem as a too-soft slug in a hot one.

Bullet hardness is rated on the Brinell (BHN) scale. Pure lead is 5 BHN; "hard cast" bullets can be close to 30 BHN. Somewhere in that range is the ideal bullet for any given cartridge; how do we find it?

As it happens, there is a way to determine the optimum bullet hardness. First, you need to know the amount of pressure your load develops. That's easy - your loading manual will have that information. (Pressure is listed in either CUP or PSI; they are slightly different, but for this particular question either will be close enough to get the answer we need.)

There are two formula: one for the ideal hardness, one for the maximum hardness.

Ideal hardness in BHN = Pressure / 1,920
Maximum BHN = Pressure / 1,422

Let's say it's a .38 Special using 4.5 grains of Hodgdon Universal Clays and a 158 grain SWC bullet. The pressure for this load is 16,700. Our formulae look like this:

16,700 '/ 1920 = 8.69 BHN ideal hardness
16,700 / 1422 = 11.74 BHN maximum hardness

You can (and should) round those to the nearest whole number. Thus, for this load I want a bullet of around 9 BHN, but no more than 12 BHN for best results.

For a heavy .357 Magnum load, using the same bullet, the numbers are dramatically different:

33,600 / 1920 = 18 (rounded) ideal
33,600 / 1422 = 24 (rounded) maximum

Big difference! If I buy bullets of 21 BHN for my Magnum, and use them in the light Special loads, they won't obturate properly and I'm likely to get leading.

Guess what? That's exactly what happened! It wasn't until I bought some bullets of a nice 10 BHN for my Special loads that my leading problem was solved. As I said at the beginning, it doesn't seem logical that softer bullets leave less residue behind - that is, until you understand the physics behind the problem.

With this information you can now go bullet shopping with confidence. You'll probably find that purveyors of "cowboy" bullets are your best choice to get the alloy hardness that you need to keep the lead where it belongs: on the target, not in your barrel!

-=[ Grant ]=-
Comments

On rimfire ammunition and accuracy


Serendipity, that's what it is. Last week a consistent topic kept coming up in a variety of places: the necessity (or lack thereof) for "accurate" .22 long rifle ammunition.

"I don't shoot groups, I hunt {insert favorite furry tidbit here}."
"You can't shoot really accurately in the field anyway, so better ammo isn't worth the price."
"The ammo already shoots better than I can, so I just buy whatever is cheapest."


I believe such comments to be shortsighted. First, though, a bit of information for those not intimately familiar with the vast array of rimfire ammunition.

The .22lr is the most popular (by a huge margin) cartridge in the world. It is available in a bewildering number of forms, from the very cheapest to the "ohmigod, I could buy a good steak dinner for that amount of money!" In general, the more accurate the ammo, the more it will cost.

The odd thing, however, is that not every .22 gun (be it rifle or pistol) will necessarily shoot the most expensive ammo into the smallest group. Rimfires are notoriously finicky; you can, quite literally, take two different .22 rifles, of the same model and vintage (and very close to the same serial number) and each will have very different ammunition preferences. Sometimes the most expensive will in fact shoot the best; other times, a less expensive fodder will do the deed.

In terms of consistency, however, the more costly ammunition will win out - it simply won't vary as much from group to group, even if its absolute accuracy isn't as good. In other words, a cheaper ammo may produce a smaller group occasionally, but the more expensive stuff will shoot the same size group all the time. In the aggregate, the more expensive the ammunition, the more likely it will shoot better in any given gun.

There's no guarantee that you'll set records with more costly bullets, but it's a dead certainty that you won't with WallyWorld specials!

Back to the subject at hand...let's say that you have a rifle that at its absolute best is capable of shooting the magic 1 minute-of-angle (MOA) group (which is, for all intents and purposes, 1/2" at 50 yards.) What this means is that the group it shoots with its best ammunition choice will fit into a circle measuring 1/2" in diameter. Clear so far?

Assuming that the actual center of the group is at the actual point of aim, any shot fired will fall a maximum of 1/4" from the point of aim; this is known as 1/4" radial dispersion. If one shot lands at the extreme edge of that dispersion, and the next at the opposite side of that dispersion, the distance between them will be 1/2", which is the group size. See how that works?

Now, let's say that some other ammunition shoots 4 MOA in this rifle (2" at 50 yards.) Any shot that is fired will now land within 1" of the point of aim. That's still not bad; certainly not enough to even get you in the door at an Olympic training village, but enough to nail pop cans off the fence.

Or is it?

A standard 12oz pop can has a diameter of 2.6", or 1.3" on either side of the center. Aiming dead on that center point, with our 4 MOA ammo, means that the worst shot of the bunch only has .3" to spare to knock the can off the fence. In other words, with that ammo your aim and hold has to vary no more than .3" if you expect to hit the can with any given shot!

Will the better ammo give us an edge? You tell me...with 1 MOA ammunition, the expected radial dispersion is .25". That means that any given shot, holding absolutely dead center, now has a margin of error of 1.05". In other words, your aim and hold now has a bit over an inch of leeway to hit with 100% certainty. I'd say that's a significant advantage, wouldn't you?

Shooting is all about being able to trust your skills, but you can't get to trust your skills until you first can trust your equipment. If you practice by popping cans off the fence, how will you know if that miss was because of your skills, or because of your equipment - and is it the ammo, or the gun?

Someone will no doubt be yelling at his (or her) monitor that not every shot will be at the outer edges of the variables. In other words, an ammo that shoots 4 MOA will distribute shots all over that circle; not all of them will be in the center (otherwise it would shoot better than 4 MOA), but likewise not all of them will fall on the edge of that circle. This is true.

The trouble with this line of thinking is that we don't know where any given upcoming shot will fall. We know that it may hit in the center of its expected circle, or it may hit at the edge, or somewhere in between. We don't know where it will hit until it does; if we expect to hit the target with every shot, we have to assume the worst and prepare for it, looking on anything else as a wonderful happenstance.

It's all about probabilities. Let's take our 4 MOA ammo; it's possible that, say, 80% of its shots might fall within a 2 MOA circle. This means that 80% of the time, you have a bit over 1/2" of leeway on that pop can. Put differently, if you can aim and hold within 1/2" of center, you'll hit the can 80% of the time. If you're happy with 80%, great! (Yes, I'm aware that you can increase the hit probability by simply decreasing the distance to the target. If you're going to shoot everything from 20 feet away, you may feel free to use the worst ammo in the worst gun, and never have the need to improve your skills. Everyone wins - sort of.)

Personally, I'm not enamored with those numbers. Look at it from my perspective: I like to hunt small game with my .22 rifles, both for pest control and dinner. I'm an old farm boy who has a close relationship to the animals around him; if an animal is to die by my hand, I require that death to be as humane - quick and painless - as is possible. For me, that means headshots and instant incapacitation. If you eat small game, you know that head shots are necessary simply to maximize the amount of usable meat from the ammo. Squirrels aren't all that big to begin with!

Further, a missed shot is a lost animal; unlike targets and pop cans, they usually don't wait around for you to try again. I want 100% hit probability if I can supply the necessary foundation (sighting and hold.)

A small animal's head often has a kill zone of around 1-1/2" (even less if forced to take a frontal shot.) If I were to use ammunition that only shoots 4 MOA, that would require me to have absolutely zero error in both sighting and hold to make a clean kill at 50 yards. (Actually, it has negative error - meaning that even with perfect performance on my part, I cannot expect the ammo to deliver a clean hit 100% of the time.) At 25 yards, it doesn't get a lot better - my total allowable aim/hold error for a clean kill is a whopping quarter-inch! Can you do that from a field shooting position? Really? Every time?

Switching to the better ammunition gives me a big edge. At 50 yards my self-induced error allowance is now a half inch, and at 25 yards it is almost 3/4". It means that the chances of a successful clean kill are significantly improved by using the better fodder.

Higher quality .22lr ammunition isn't just for benchresters and group junkies. If one is just starting out, it means faster and surer skill development. For the hunter, it means greater yield and more humane treatment of the animal. In my mind, it's worth the price.

The only thing left is to get a whole bunch of different kinds of ammunition and test them all in your gun. You'll learn just how much you'll have to pay to get the accuracy you really need - not the accuracy someone insists you can settle for!

-=[ Grant ]=-
Comments