More on testing .22 Long Rifle ammunition.

Wednesday, October 15, 2008 Filed in: Ammunition, Rifles

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 ]=-

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