Ogive Length Sorting

[PNW Skipper]

I found discussions of sorting rimfire ammo by the distance from the top of the rim to the ogive on Accurate Shooter, as well as a review of Mr. Gerry Gereg's tool for doing it. I wondered how much difference it might make, so I ran a little exercise that is meant to be indicative, not conclusive, to inform whether I want to invest the effort.

I sorted 3 boxes each of 2014 vintage RWS R100, and 2022 vintage Lapua Biathlon Extreme, knowing my next match was expected to be in 25-35F weather. If you are not familiar with the device, it is measuring from an arbitrary 0 reference to evaluate relative differences in ogive length, not the absolute value of length. For both ammos, each group of 150 cartridges yielded 50 cartridges that differed from each other by no more than 0.0005" and another 50 that differed from each other by no more than 0.0010". So far, so good... Mr. Gereg's advice is to group ammo by increments of 0.001", so that's pretty consistent. The surprise came at the tails.

The newer Lapua was much tighter, with the extreme values (0.0155"/0.0190") only 0.0035" different. The older RWS had a significantly wider spread (0.0155"/0.0340) with 0.0185" difference. The latter difference was readily apparent when the cartridges were stood side by side, and since that delta translates directly into a difference in bullet engagement when the shot is released, I wondered how much difference it might make on paper.

So before the match began I warmed the clean barrel on my KK-500 (previously tuned for Lapua Biathlon Extreme) with several rounds of Tenex, then shot a five shot group at 50 yards with the RWS R100 with the highest sorted lengths, followed by a second group with the lowest sorted lengths. Temp was 28F, wind 5-12 mph. See photos below.

What was noteworthy to me was that there was 0.2" vertical difference between the center of the two groups at 50 yards. There are a fair number of disciplines in which that delta could be significant if it occurred randomly out of the box during competition. I for one will add this practice to my match preps.

BTW, because I know some of you can't resist asking, the third group on the right in the bottom photo is a 5 shot group with the Lapua Biathlon Extreme the rifle was tuned with, shot immediately after the R100 groups with ammo that sorted from the 0.0185" to 0.0190".

 

[TRSR8]

Don’t know what you think this test means for you. For me it says don’t do 22 tests when it’s 28 deg, especially gusting to 12 mph.
Rule #1 in testing is knowing what conditions might yield useful results

 

[PNW Skipper]

Don’t know what you think this test means for you. For me it says don’t do 22 tests when it’s 28 deg, especially gusting to 12 mph.
Rule #1 in testing is knowing what conditions might yield useful results

I've heard that observation before, but personally consider it just so much noise. Not all of us have the luxury of only shooting indoors, or in more temperate conditions. So for us, tests at those temps make sense. I retuned the KK500 and a Stiller 2500 outdoors in January at 20F because the six card first round of the 2023 Eley Benchrest Masters competition had to be completed in February. I shot that competition in temps between 14F-38F with full value winds up to 10 mph. My 6 card composite was 1482-56X on the IR 50/50 target at 50 m. It wasn't as good as I hoped, but good enough for 5th place. Our local match season (at the notoriously windy Rattlesnake Mountain Shooting Facility in SE WA) opened in similar conditions in March.

Not relevant to the conditions you shoot in? Fine. Ignore it.

But, please spare me the snarkiness about testing in "conditions that might yield useful results." If you have to compete in cold and windy, you better test and practice in cold and windy.

 

[dutch14]

I don't know of a 50 yd indoor range in Indiana.

 

[PNW Skipper]

I don't know of a 50 yd indoor range in Indiana.

Nor one out here in the Pacific NW... I'm truly envious of those shooters who get to compete in some of the indoor ARA matches, although I understand they have a different set of issues to deal with!

 

[Hi-NV Shooter]

Here are some results sorting the new Lapua long range and super long range. this rifle has never shot this ammo before. but I know it likes lengths in the 0.710-0.725 the target was shot in left to right condition. misses were all me and not the ammo. you will find interesting my notes on the target two different lots of an ammo this rifle has never shot before. the spread in OAL difference was only 0.005 this is really good.

Lee

 

[USMCDOC]

Here are some results sorting the new Lapua long range and super long range. this rifle has never shot this ammo before. but I know it likes lengths in the 0.710-0.725 the target was shot in left to right condition. misses were all me and not the ammo. you will find interesting my notes on the target two different lots of an ammo this rifle has never shot before. the spread in OAL difference was only 0.005 this is really good.

Lee

Got caught by the pick ups didn't ya

 

[JimSC]

I messed around quite a bit last fall/winter with various sorting methods. From my centerfire experience I went into this prejudiced thinking the base to ogive was probably the most important factor. I have seen as little as .003 make a difference when developing a load for F class. Anyway I experimented sorting ammo by BTO, weight, and rim thickness and combinations of the three for a few months and never could come to a solid conclusion. That could have been due to the fact I was using a factory rifle and any differences were getting lost in the noise.

One thing that became apparent though was you get what you pay for. Lapua Midas + had a SD of .000 with a ES of .001, Center X ES of .002 and a SD of .001 compared to SK STd + with an ES of .006 and a SD of .002. Rim thickness and weight differences also followed that trend.

What you pay for with the premium ammo is consistency. What is confusing is that often mid priced ammo will shoot just as well, at least for me with factory rifles.

 

[Hi-NV Shooter]

Got caught by the pick ups didn't ya

Yeah L-R is my worst condition to shoot in.

 

[Hi-NV Shooter]

I messed around quite a bit last fall/winter with various sorting methods. From my centerfire experience I went into this prejudiced thinking the base to ogive was probably the most important factor. I have seen as little as .003 make a difference when developing a load for F class. Anyway I experimented sorting ammo by BTO, weight, and rim thickness and combinations of the three for a few months and never could come to a solid conclusion. That could have been due to the fact I was using a factory rifle and any differences were getting lost in the noise.

One thing that became apparent though was you get what you pay for. Lapua Midas + had a SD of .000 with a ES of .001, Center X ES of .002 and a SD of .001 compared to SK STd + with an ES of .006 and a SD of .002. Rim thickness and weight differences also followed that trend.

What you pay for with the premium ammo is consistency. What is confusing is that often mid priced ammo will shoot just as well, at least for me with factory rifles.

My friends I shoot with are CFBR shooters. speaking with them confirmed what I am doing is what they do in their load developments except I can't adjust the amount of engagement. so, what I have done was take my best lot and used that as the base OAL. even in a factory barreled rifle it will work. you just have to find a lot that shoots and use that as the base OAL. I found 0.015 is the most you can go from the base OAL this would be plus or minus.

Lee

 

[TRSR8]

Some might ponder why virtually zero outdoor sanctioned matches are ever shot north of the Mason Dixon line in the colder months.

 

[PNW Skipper]

Here are some results sorting the new Lapua long range and super long range. this rifle has never shot this ammo before. but I know it likes lengths in the 0.710-0.725 the target was shot in left to right condition. misses were all me and not the ammo. you will find interesting my notes on the target two different lots of an ammo this rifle has never shot before. the spread in OAL difference was only 0.005 this is really good.

Lee

Lee,
Those 0.7xx numbers appear to be actual lengths rather than the relative differences between rounds. How are you measuring those?

Phil

 

[PNW Skipper]

My friends I shoot with are CFBR shooters. speaking with them confirmed what I am doing is what they do in their load developments except I can't adjust the amount of engagement. so, what I have done was take my best lot and used that as the base OAL. even in a factory barreled rifle it will work. you just have to find a lot that shoots and use that as the base OAL. I found 0.015 is the most you can go from the base OAL this would be plus or minus.

Lee

Interesting approach to using the data Lee. I have initially been focused on making sure the ammo length was consistent, not on finding an optimal length for the particular rifle. Have you found any difference between ammo types for a given rifle, perhaps based on bullet shape? Intuitively it would make sense that the amount of engagement would be different at the same longitudinal length for a blunt Eley Tenex/Match bullet profile compared to a more conventional round nose profile.

Phil

 

[JimSC]

My friends I shoot with are CFBR shooters. speaking with them confirmed what I am doing is what they do in their load developments except I can't adjust the amount of engagement. so, what I have done was take my best lot and used that as the base OAL. even in a factory barreled rifle it will work. you just have to find a lot that shoots and use that as the base OAL. I found 0.015 is the most you can go from the base OAL this would be plus or minus.

Lee

what I ended up with was that BTO will vary widely with the brand. Lapua and SK was around .762 - .765 BTO , Eley tended to run .750 ish. The more you pay, the less variance from round to round and lot to lot.

My 452's prefer ammo that measures around 760 - .765 BTO. My 457 Varmint does not seem to be as picky and will shoot Eley Match or Lapua Center X and not complain about either. Go figure

Makes sense because I can think of five .22 reamers all with different throat dimensions. Lilja, Anshutz, Bentz, Match, and Sporting. A gunsmith friend of mine throats his .22 barrels to "engrave" his ammo back a certain distance on the ogive. Last time we talked he had seen only middling improvements using Lilja barrels on a CZ

But you are right , what you are doing is the same thing CF loading accomplishes and it is a big deal with CF. I expected more of a difference than what I found in practice with my rimfire. Shooting 25 shots with BTO differences of up to .005 or when sorting into lots of .001 variance I saw little if any change on paper. Whereas with centerfire long range that would make a great deal of difference

 

[Hi-NV Shooter]

Lee,
Those 0.7xx numbers appear to be actual lengths rather than the relative differences between rounds. How are you measuring those?

Phil

Hi Phil,

I replaced the analog dial indicator with a digital one makes reading the measurement easier and faster.
measurements are what the gauge is reading from the ogive to the rim face.

Lee

 

[Hi-NV Shooter]

Interesting approach to using the data Lee. I have initially been focused on making sure the ammo length was consistent, not on finding an optimal length for the particular rifle. Have you found any difference between ammo types for a given rifle, perhaps based on bullet shape? Intuitively it would make sense that the amount of engagement would be different at the same longitudinal length for a blunt Eley Tenex/Match bullet profile compared to a more conventional round nose profile.

Phil

Phil,

I haven't shot Eley in nearly 10 years. and all my rifles have benchmark barrels with Nevius chambers. so, for me knowing the chamber ideally shoots best with only 0.030-0.040 engagement is important.

But sorting and grouping the same lengths will give better results. I found the rounds that have a big difference from majority will be the one that gives the flier. it seems mainly the longer lengths past my base OAL will be the worst.

Lee

 

[Hi-NV Shooter]

what I ended up with was that BTO will vary widely with the brand. Lapua and SK was around .762 - .765 BTO , Eley tended to run .750 ish. The more you pay, the less variance from round to round and lot to lot.

My 452's prefer ammo that measures around 760 - .765 BTO. My 457 Varmint does not seem to be as picky and will shoot Eley Match or Lapua Center X and not complain about either. Go figure

Makes sense because I can think of five .22 reamers all with different throat dimensions. Lilja, Anshutz, Bentz, Match, and Sporting. A gunsmith friend of mine throats his .22 barrels to "engrave" his ammo back a certain distance on the ogive. Last time we talked he had seen only middling improvements using Lilja barrels on a CZ

But you are right , what you are doing is the same thing CF loading accomplishes and it is a big deal with CF. I expected more of a difference than what I found in practice with my rimfire. Shooting 25 shots with BTO differences of up to .005 or when sorting into lots of .001 variance I saw little if any change on paper. Whereas with centerfire long range that would make a great deal of difference

I am wondering the reason the tolerance in RF is bigger is because of a lead bullet versus a jacketed. lead will conform to the rifling whereas copper will have more resistance.
.
I forgot to mention that cast lead shooters do the same with the loading gauge they use. they set it so it pushes the bullet to engage to what that barrel likes.

Lee

 

[JimSC]

I am wondering the reason the tolerance in RF is bigger is because of a lead bullet versus a jacketed. lead will conform to the rifling whereas copper will have more resistance.
Lee

the average benchrest or long range handloader tries to get everything exact to .01 of a grain of powder (.65 milligrams) and .001 BTO length.

I was referring to was when developing a load I usually go up in .003 increments and have a tune go from zero to hero with that small of a change. In CF you are adjusting the "tune" by changing powder load, seating depth, and primer choice. A change in any one of the three can really affect a loads performance

I found that very strange after my centerfire experience that I could shoot two rounds that were .005 or more difference and there was virtually no change in POI. I fully expected to find the sorted ammo shooting higher scores with fewer flyers and the culled batch all over the target. My test was only 25 rounds (5 x 5's) of each sorting method using SK Pistol Match Special and my old 452's so it could have been me, the environment or the rifle or a combo of all three. I would be curious to see what others here find when they try sorting. I may even try running the tests again using my 40X this time

 

[dgeesaman]

I’m not surprised since match 22 ammo/ chambers engraves on the bands of a pure lead bullet. Similar to centerfire, where there is so much jam that more jam doesn’t change anything.

 

[TRSR8]

My friends I shoot with are CFBR shooters. speaking with them confirmed what I am doing is what they do in their load developments except I can't adjust the amount of engagement. so, what I have done was take my best lot and used that as the base OAL. even in a factory barreled rifle it will work. you just have to find a lot that shoots and use that as the base OAL. I found 0.015 is the most you can go from the base OAL this would be plus or minus.

Lee

Lee,
What many may not fully appreciate is that while you are not wrong, much of this is chamber depth/barrel configuration dependent with MI barrels requiring certain ranges of OAL.
Recall, a while back, the WLM was droning on about ELEY posting OAL numbers with their lots, especially if he chambered for good but short OAL, and you then try stuff .010” longer. More than a few of those guns had issues when the ideal lot was used up.Carbon fouling rates change substantially as a for instance.
Some guys still chamber short, some long, some sharp ones cut a mid depth chamber and then adjust as they test to see how fast leade fouling develops.
My guns, for instance seem to have a “mid depth“ chamber….. more tolerant of OAL variances, which when I shot mostly ELEY, did a fair amount of testing in this regard after I got a proper measurement gauge .