Rimfire Concentricity & Accuracy

[BlackWhiskey]

I found a very interesting research paper last night while exercising my google-fu that seems to contradict a lot of what I have previously come to think as fact. This research paper claims that rim thickness and cartridge weight sorting is ineffective in gaining accuracy in rimfire shooting, and that the best results come from sorting bullets based on their concentricity. The research paper seems well written and referenced, and I am worried that I have been wasting a lot of time in my sorting. What say you? Link

 

[ivanthesane]

Re: Rimfire Concentricity & Accuracy

Accuracy is dependent on consistency... could be that rim thickness or bullet weight (and charge weight, brass thickness, etc) *less* important than concentricity but they all have an effect.

 

[pjsalpine]

Re: Rimfire Concentricity & Accuracy

? sorting by concentricity or correcting concentricity.

 

[BlackWhiskey]

Re: Rimfire Concentricity & Accuracy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pjsalpine</div><div class="ubbcode-body">? sorting by concentricity or correcting concentricity. </div></div>

Your question is answered in the research paper. I included a link to it in the OP.

 

[Dylan in AZ]

Re: Rimfire Concentricity & Accuracy

Quite an interesting read if you ask me.

The overall goal in testing rimfire ammo is to be as accurate as possible. It's not something we can ourselves control like with centerfire ammo where you can roll your own and check all the variables independently as you work through your process. Rimfire ammo comes from the factory as is and there are but a few things we can check in an attempt to make it as accurate, read consistent, as possible. Those things can all go under a general category of "sorting" and the author's research on concentricity is just another sub-category to file underneath "sorting."

Weather concentricity is as important as others or will lead you to better accuracy than the rest, is up to each of us to decide on our own. I myself choose not to sort my ammo, but rather deal with whatever is given to me as a result of my laziness. If I were to use less consistent ammo for the shooting I do, then I would look into all the different types of sorting that can be done to ensure better accuracy. However, I use 'good enough' ammo during practice sessions and 'even better' ammo for shooting seriously. I did try sorting higher end stuff, didn't do me much good as it is already fairly consistent. I tried sorting mid-grade stuff, still not enough improvement to warrant continuing the arduous process. And finally I tried sorting the cheap crap, and while this improved groups greatly, it still wasn't worth shooting because my mid-grade practice ammo still shot twice as good as un-sorted ammo.

Sorting by rim thickness, bullet diameter, cartridge weight, etc, etc... are all viable ways to gain consistency from your ammo. The problem that I see is that many shooters, like me, may not see enough of an improvement to warrant doing the dirty work to get that consistency. I'm no benchrest shooter, meaning I don't want a 30lb rimfire gun bolted to a table to shoot at 50 yards. I shoot at 100 most of the time, and when conditions allow, I move to 200 for score as well. I gave 300 a try once, but even the slightest wind was having a massive effect on the slow little bullets. So for now at least all I care about is cleaning the 100Y TQ4 and moving on to work towards the same exact goal on the A-21 at 200 Yards, with hopes of moving on to the 'big boys' target (MR63) at 300 someday. Those of you who regularly do well at that range have a high respect from me because I know just how incredibly difficult it is. Hell, 200 has proven to be more than enough of a challenge for me. But at those distances, I will only use great ammo, because 'good enough' doesn't cut it at that range. And like I said, sorting great ammo doesn't yield hardly any advantage for me, so I won't bother with it unless I can prove to myself that it is worth the time and effort.

In conclusion, do not give up whatever type of sorting you currently do if in fact it works for you and you don't mind putting in the time to get the results.

To the OP, thanks for posting this article. I enjoyed reading through it and I hope it leads to some good conversation and maybe even some individual testing.

-Dylan

 

[TOP PREDATOR]

Re: Rimfire Concentricity & Accuracy

VERY interesting article, and although i'm not trying to debunk the results of their testing, but a few skeptical first impressions:

1. the testing was done with some top shelf ammo in the first place

2. impressive groups, but similiar groups have been seen (consistantly) from folks here and elsewhere using Wolf extra and stock rifles at 50 meters or yards.

3. Quote "The data from the 1994 tests for rim thickness and shell weight sorting was inconclusive" - we all know different and rather conclusively both works to some extent.

4. the writer is actually selling the guage, not really an unbiased test.


i'm sure that Concentricity plays a part and there is something to it increasing accuracy in rimfires (just as with centerfires), especially with that highest caliber of ammo used. i think for the majority of folks that use less than that caliber of ammo, weight sorting or rim thickness plays a bigger part to weed out those under or overcharged rounds as the "lesser" ammos will probably experience more extremes in those areas. i'd like to se the same done with less than olympic grade ammo and equipment.

of course this is all conjecture on my part, as i don't have a Concentricity guage handy and able to experience it myself.

but i am partial to the fact that no matter how straight everything is, if it is under or over charged, the POI will be different.

so if i were to be in the highest of competition using the best of ammo and equipment, i'd definately sort by weight, rim thickness AND concentricity to get the gold.

my other question is, and probably can't be proven without some sort of high speed photography, is that does the really soft lead bullet sort of correct itself running down the barrel and coming out the muzzle, or does it actually remain "cocked" and the lands and grooves cut into one side of the bullet more than the other?

 

[BlackWhiskey]

Re: Rimfire Concentricity & Accuracy

Thanks for the replies Terror and TP. I purchased a box of bulk Federal 22lr and I am going to do a small scale test of shell weight separation vs rim thickness separation vs thickness and weight separation vs no separation.

1. What distance should I do the test? 50yds is what I'm planning on doing.

2. How many rounds per group? I was thinking several groups of 5 rounds.

3. How often, if at all should I clean the bore? I was planing on not cleaning it at all, but what do you guys think?

I'll post results incrementally as I don't think I can do this all in one day. Your input and added data would be much appreciated.

Thanks,

Cory

 

[pjsalpine]

Re: Rimfire Concentricity & Accuracy

BlackWhiskey
Thanks for the interesting article, missed the link this morning... Got me hooked around noon,spent the rest of the day reconstructing his data and building the excel and mathCAD workbooks.

 

[TOP PREDATOR]

Re: Rimfire Concentricity & Accuracy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BlackWhiskey</div><div class="ubbcode-body">Thanks for the replies Terror and TP. I purchased a box of bulk Federal 22lr and I am going to do a small scale test of shell weight separation vs rim thickness separation vs thickness and weight separation vs no separation.

1. What distance should I do the test? 50yds is what I'm planning on doing.

<span style="color: #FF0000">try 50 and 100 yards. you'll find that rim thickness will out do weight sort at 50, but at 100 yards i'll lay money on the weight sort</span>

2. How many rounds per group? I was thinking several groups of 5 rounds.

<span style="color: #FF0000">5 is good, 10 is better. </span>

3. How often, if at all should I clean the bore? I was planing on not cleaning it at all, but what do you guys think?

<span style="color: #FF0000">if you are switching ammos, definately clean it (at least dry swab it a few times) and use 1 fouler off target. if you want clean it before each group that'll be fine, though not really neccessary - but again shoot 1 fouler before the group.

it's sort of funny too, some ammos will shoot better through a cleaner barrel than a dirty one and visca versa</span>

I'll post results incrementally as I don't think I can do this all in one day. Your input and added data would be much appreciated.

<span style="color: #FF0000">if you split them up into different sessions, try to do it on "like weather days". it would be best to try to get them in all on one day so shooter and environmentals are somewhat equal.</span>

Thanks,

Cory</div></div>

 

[671RTO9513]

Re: Rimfire Concentricity & Accuracy

Upon reading the article, I'm wondering if a more productive way to reasonably small grouping would simply be to "loosen" the bullets in the case mouth so they self center in a match chamber.

The tester's original 1413 yielded groups almost as small with the loose bullets as those with only one thou runout.

Might be worth a try.

 

[Dylan in AZ]

Re: Rimfire Concentricity & Accuracy

Cory,

1) 50 yards will be fine. At that distance, you won't encounter hardly any offset from factors such as wind, however I would still encourage you to pick a day that doesn't have any wind or at least very little. Also, if the bulk Federal ammo you bought is supersonic then you should limit your testing to distances below the transonic barrier. If it is subsonic though, I would like to see a few samples done at 75 or 100 yards as well in ideal conditions. This would show if the resuls are true at slightly longer ranges as well. But for anything much past 100 yards, I would be skeptical about any data you retrieve due to things like wind or shooter error. And speaking of which, if you want to make this truely scientific, you should consider using a really solid rest or even a sled if one is available to you. The reason for this, in case you don't know where i'm going with that, is to remove shooter error from the equation as much as possible.

2) Although the "standard" is 5-shot groups, I personally prefer to shoot 10-shot groups if conditions allow. But that being said, if I have enough ammo and time and the conditions are good, I love to shoot my preferred monthly match in a "mock session" meaning I shoot 25 rounds at the TQ4 at 100 yards. Since this is my preferred distance and my favorite target, it makes the most sense to me to shoot it with whatever ammo I happen to be testing. Being after a different goal, you may not feel that 25 shot "groups" are appropriate.

3) If you re switching between ammo you need to devise a system ahead of the time of testing to ensure that there will be as little bias in the test as possible. Since I believe you're sticking to one specific lot of ammo I feel that you're going to recieve the best results by cleaning the bore before any testing begins, thoroughly seasoning the bore (meaning 35-50+ rounds or however long it takes past that before groups are printed with a fair degree of consistency from one to the next), and then after sighting in at whichever distance you decide on, and refrain from any type of cleaning at all. In short: clean before testing, season bore thoroughly, shoot all test groups w/o any cleaning.

-Dylan

 

[RicosRevenge]

Re: Rimfire Concentricity & Accuracy

My testing was done almost 2 years ago using the Eley Orange Box ammo from Cabelas. I simply did rim gauging. I didn't clean between shoots due to it being the same lube and did 10 round groups at 50 yards.

I found that the rim thicknesses went from .028 to .039 with the Eley Orange Box. The bulk of the rounds fit between .033 and .037 and the absolute best shooting was the 0.034 which was not what I was expecting. I expected the thicker rimmed rounds to be a little tighter and therefore the winners.

I can't find my old targets but I found a data sheet the showed aggregate data of (5) 5-round groups measured Over All less 0.221"...

.028 - 0.56
.029 - 0.44
.030 - 0.34
.031 - 0.28
.032 - 0.31
.033 - 0.24
.034 - 0.21
.035 - 0.38
.036 - 0.32
.037 - 0.32
.038 - 0.37
.039 - Inconclusive but not good. Only had enough of this thickness for 2 groups both over 1" at 50 yards.

The .033 and .034 both shot sub 1/2 MOA at 50 yards and everything else with the exception of the .028 shot sub MOA.

With that said, the R50 I shoot now is too consistant for me to worry about rim gauging anymore. Now I jusy buy a brick and shoot it.

 

[pjsalpine]

Hi BlackWhisky,
I can see this is an old thread, I don't see a link to the research paper in the OP, I thought maybe when the hide did the software change the link may have been blown away, I was hoping you still had the link.
Alpine