Those fickle .22 WMRs!

Yesterday, I was thinking that it would be a good idea to see if I could find a better barrel for my CZ 455, .22 WMR because it won't group as well as I'd like at 100 yards. I searched the Internet and only found factory replacement barrels. Then, I re-examined my latest targets and decided that it would be folly, given the ammo available today, to try and get a sub-1" grouping barrel because it's probably the ammo limitations that's the problem.

Nevertheless, prior to cleaning the bore, I checked the muzzle and there was a very hard residue on the face. That doesn't bode well for accuracy, so I carefully cleaned it off. Then, decided to take my piloted target crowning reamer and make it better than it was, which I did. (Like that's going to make a bit of difference.) Anyway, I re-crowned the face and polished it.

Next, I examined fired shells to check the firing pin impact and noticed that there was good indentation, but that hits were also high on the rim, where there's only metal and a detriment to uniform ignition, so I took the Dremel out and carefully ground the highest part of the firing pin nose, as rifle-smith Calfee recommends for .22LR benchrest rifles. Impacts look really great...a bit deeper and where they should be.

The next relatively calm day, I intend to shoot 100 yard groups to see if there was an improvement, but am not expecting more than an eighth-inch better. That's relatively little, but every little bit helps. I'll let folks know if it worked.

Meanwhile, I stopped at Cabela's and bought more .22 Mag ammo yesterday. They didn't have any Remington, which tends to shoot best in the rifle, but have some of that on hand.

JP

RecoilRob said:

In your quest for accuracy it might be worthwhile to carefully check the ammo for size and weight. If the projectiles vary at all....which is likely....you could cull them into groups of like sizes and see if any trends jump out at you. Same goes for weights....perhaps the powder charges are slightly different round to round? Like you say...every little bit helps.

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That's a bit more fuss than I'm planning, but might be something to try. I used to do that with .22LR ammo when using some of the less expensive target ammo when shooting early benchrest. I gave that up after using some of the more expensive match ammo.

Actually, a few flyers are to be expected with WMR stuff, since it's primary use is for hunting/varmint disposal, not target shooting. I'd take a gamble to say that 99 percent of WMR ammo isn't fired beyond 75 yards. If that's true, a 1" grouping at 100 yards means that no rounds are going to miss target center by more than 1/3" at 50-60 yards...more than adequate for varmint/small game. Comparing with .22LR, there is less variation from aim point due to both trajectory and dispersion with .22 WMR than with .22LR at, say 70 yards. That, plus increased velocity/energy results in a better killing round, provided the bullet is soft enough to expand well in the quarry. IMHO

Carl N. Brown said:

Please post a range report.

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I intend to go out to shoot groups around 2:00 today (6/3/18), when the wind is expected to diminish to about 4 mph, from about a 10 o/clock direction. I'll be sure to report, but don't expect a huge improvement over the 1"-1 1/4" dispersion obtained earlier.

WMR ammo is more variable in head reaction from brand to brand and sometimes within a box of the same brand. I notices that some rounds sound much louder than others and heads expand differently. Remington ammo seems much more uniform in head appearance, after firing.

I went down back and fired a few shots this morning, but the wind is way too strong and variable. Maybe it will subside this afternoon. My target looked more like buckshot patterns than rifle shots...mirage was also bad. It's supposed to calm down this afternoon.

Fired again this afternoon, but wind was variable. Got some fair results, but hoping for better ones. Most were horizontal, due to frequent wind shifts. One was 0.4" high and 1.2" wide made with CCI-WMR. Glad the vertical was as good as it was, since that was the problem before. Maybe we'll get some more predictable wind in a few days. Tomorrow is going to be a rainy day.

I print my own targets four squares and one round circle on an 8 1/2" x 11" sheet, so like many rimfire groups at 100 yards, there is overlap from one group to another, especially when the rifle isn't zeroed perfectly for each brand/type of ammo. Centerfire is not usually a problem and at 50 yards they work fine for rimfire, but at 100, with wind blowing and not well sighted in, groups tend to mix a bit. I can tell the difference between .22 mag and .22LR, but it's not a pretty scene when wind blows across the target.

Another thing I noticed about WMR ammo is that there were a few shots that were MUCH louder than others and some cases bulged the head a bit. I'll chrono some next time, if I can fit the tripod properly near the rock wall, ahead of the bench.

Today and tomorrow, we'll be getting rain and I've got dentist and doctors' appointments for these three days, so further testing will have to keep a bit.

midland man said:

I found in my 22mag rifle that the only ammo that shot really good groups was the federal 50gr Hp ammo as I tried the 30gr,40gr and they didn't perform nearly as good so if you haven't tried the federal 50gr you might give those a try!

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Thanks. I've tried about everything but the Federal. Had my hands on some at Cabelas, but chose CCI, Winchester, and Hornady. Dispersion mirrored the .22LR, R50 ammo in my very accurate Rem 504, so I'm generally happy with the results, compared with the larger vertical dispersion obtained with other ammo, prior to tweaking the rifle.

Comparing casehead firing pin strikes, before (left) and after (rt.) re-shaping CZ 455 .22 WMR firing pin nose. Note the indentations at the rim are shallower on those to the left, while depths are greater on the right, tending to spread primer flame better around the rim. The reshaped firing pin nose better pinches the rim against the case body and spreading flame, thus improving powder ignition.

This trick was learned from Calfee, who wrote extensively on accurizing .22 LR rifles. I've used his tips a lot when accurizing 10-22s, etc.


(Sorry, about the focus, which was difficult with the camera. This was the second attempt.)

Got out under pretty good conditions this afternoon. Two mph variable wind. Cloudy. CZ 455 .22 WMR.

Remington seems to be the best in it, but it's not a target rifle. It will kill, with the right ammo, however. Remington: best group was 5 shots at 1.1" extreme spread and 0.8" vertical and horizontal. Other ammo is very disappointing. At least with that ammo, it's not stringing vertically, which is what I was trying to achieve.

I need to do something about the trigger. It's about 4 lbs and has a lot of backlash. I'd like to get it down to 2 lbs. and need to do "something" about backlash. Unfortunately, the bolt won't come out unless the trigger is pulled all the way back. DUH! It may need some sort of flip-up trigger stop.

chicharrones said:

The most accurate 40 grain .22 WMR ammo I've used is Remington PSP (pointed soft point) R22M2.

Everywhere I've checked shows it discontinued or out of stock. It will be truly sad if I can't buy that ammo anymore.

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I'd better stock up too. It's the best I've found.