Long range load development at 100 yards.

[dieselten]

Here is my AIAE with Benchmark 6.5x47L barrel. Sierra 123 with Varget, 100 yards. last 2 groups the primer center started protruding but no blown primers, no other pressure signs, easy bolt lift. From what I have read the AI bolt tends to do this with small primers. I did chrono 1 round of some of the loads. These were the first 30 rounds through a brand new barrel, 8 rounds to sight in before starting this test. First group is 4 shots (cause it was stringing so bad I threw the last one in), the rest are 3.

What is your read?

Judging by your target, your rifle is very accurate, as most of the groups look good.

I would try 37.3 gr., since it's between 37.0 and 37.5, which both shot well. Also would be tempted to try 36.3 for the same reason, but I would try the faster node first. Good luck and post results after you do seating depth testing in .003" increments.

Here is my update, I wanted to re-do the whole test because 1. The brass was brand new and not fireformed, and 2. The barrel was unfired. It now has 110 rounds on it. So the left target is the whole thing starting over with fireformed brass and -.025 seating depth, and the right target is brand new brass loaded to 37.3 with seating depth varying by .005 from -.010 to -.025. Two curious things 1. no primer problems with the fireformed brass, even up to 38.8 grains of Varget (see old post) 2. the 37.3 load hit slightly higher with the new unfired brass. Both are probably due to the fireformed brass having larger internal volume plus they also had about .0005 (half a thousandth) less neck tension.

I am thinking I want to stick with 37.3 and -.025. What do you think?

 

[Erik Cortina]

37.3 and -.025" look real good, go with it!

 

[dieselten]

Thank you Erik,

This thread is very helpful!

 

[savageshooter86]

Just curious was the wind blowing hard on the-10 thous load? It had absolutely no vertical, but it didn't group nice and tight?

 

[BoydAllen]

I believe that there is a phenomenon that has been observed where tune is such that there is no vertical but disproportionate horizontal. I am primarily aware of this as part of tuning for short range benchrest, but see no reason that it would not occur when tuning for longer ranges, with loads that are suitable for that application. If you look for the six segments on Youtube, that are all part of a presentation that Jack Neary has made at several benchrest matches, you will see that he discusses this very point. Jack is a member of the Benchrest Hall of Fame, and his discussion is worthwhile viewing for anyone who is interested in the finer points of tuning. I will leave it to Erik to comment on how it applies to longer distances.

 

[Erik Cortina]

I believe that there is a phenomenon that has been observed where tune is such that there is no vertical but disproportionate horizontal. I am primarily aware of this as part of tuning for short range benchrest, but see no reason that it would not occur when tuning for longer ranges, with loads that are suitable for that application. If you look for the six segments on Youtube, that are all part of a presentation that Jack Neary has made at several benchrest matches, you will see that he discusses this very point. Jack is a member of the Benchrest Hall of Fame, and his discussion is worthwhile viewing for anyone who is interested in the finer points of tuning. I will leave it to Erik to comment on how it applies to longer distances.

Tune will induce horizontal just as it will induce vertical. A well tuned rifle will shoot round groups and it will also shoot better in the wind. That's why it's easier to shoot a well tuned rifle in the wind at long range, because the bullet gets blown around less in the wind.

I have observed this phenomenon in F-Class. Ask the shooter that is shooting well for the day where he was holding, and he will usually tell you something like "I never held outside the 10 ring", and almost everyone else with identical or better ballistics were struggling holding out to the 8 ring trying to keep it in the center.

I believe this happens because a well tuned load will stabilize the bullet immediately, therefore giving that bullet a higher BC than an identical bullet that flew unstable for the first 100 or 200 yards before it went to "sleep".

 

[Dgd6mm]

Makes sense.

I believe that there is a phenomenon that has been observed where tune is such that there is no vertical but disproportionate horizontal. I am primarily aware of this as part of tuning for short range benchrest, but see no reason that it would not occur when tuning for longer ranges, with loads that are suitable for that application. If you look for the six segments on Youtube, that are all part of a presentation that Jack Neary has made at several benchrest matches, you will see that he discusses this very point. Jack is a member of the Benchrest Hall of Fame, and his discussion is worthwhile viewing for anyone who is interested in the finer points of tuning. I will leave it to Erik to comment on how it applies to longer distances.

Tune will induce horizontal just as it will induce vertical. A well tuned rifle will shoot round groups and it will also shoot better in the wind. That's why it's easier to shoot a well tuned rifle in the wind at long range, because the bullet gets blown around less in the wind.

I have observed this phenomenon in F-Class. Ask the shooter that is shooting well for the day where he was holding, and he will usually tell you something like "I never held outside the 10 ring", and almost everyone else with identical or better ballistics were struggling holding out to the 8 ring trying to keep it in the center.

I believe this happens because a well tuned load will stabilize the bullet immediately, therefore giving that bullet a higher BC than an identical bullet that flew unstable for the first 100 or 200 yards before it went to "sleep".

 

[dieselten]

Just curious was the wind blowing hard on the-10 thous load? It had absolutely no vertical, but it didn't group nice and tight?

Wind was the same for all testing

 

[teele1]

Eric,
It took over a month but finally had a day to shoot the seating depth test for my 6CM
3 shots at each square 5 on top and 4 on lower row

sorry bad sunburn may have indered the results

 

[Erik Cortina]

Teele, there's a few good groups I'm there. It's hard to read the seating depth numbers but I would measure all the groups and graph the group size and you should be able to tell where the accuracy window is. Or, just pick a small group and make sure it has small groups next to it on each side to give yourself some room for error.

 

[teele1]

thanks Erik

 

[kelbro]

Summary of previous 20 pages...

Or, just pick a small group and make sure it has small groups next to it on each side to give yourself some room for error.

 

[southtxhunter]

Sorry for the cut out, made it easier to see everything together....


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I took the 41 grain load and varied seating depth .003" looking like 2.119" coal is gonna be a winner. I'm going to re-shoot a few just because of user error on the last shot, and load up some of the 41 grains coal @ 2.119 and see how it does with 5 shot groups at 100 and 200 and stretch it's legs.



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Thanks for the great info Erik!

 

[dryhumor]

I had PM'd and asked Erik if he had had any time with the Lapua Scenar L 136gr bullets. He said he hadn't time yet, but did recommend I drop my 139gr Scenar load by 1 gr. I didn't see his reply before loading..... I started right under my 139gr load charge, and moved up a bit. I got close with my starting charge, but I intend to drop down a couple more .2 gr increments to see if it tightens up. I'm seated about 30 thou less than my 139 gr load.

I develop loads at 160 yds. Started with a clean bore, 1st shot fouler/sighter. 2nd shot is in the first group.

Thanks Erik.

Jim

 

[BoydAllen]

I think that there is ample evidence that it may take more than one shot to stabilize the condition of a clean bore. Given that, your first group/load is the one. I would never go to a record target with just one shot down the tube.

 

[dryhumor]

That crossed my mind as well....

 

[savageshooter86]

southtxhunter: Where did you come up with 41gr was your node? Just curious. To me it appears your node is either 40.0 gr or 40.5 gr area. As 39 and 39.5 and 40.5 hit very similar vertically. I can't tell because 41 appears to be shot at a different part of the target but it appears it hits almost same vertically too. Where is 40.0 group?

I would drop down to 40.0 and shoot for seating depth and I think you would be in the middle of a pretty large node?

 

[dieselten]

Here is another test with my Accuracy International 6.5 x 47L with Sierra 142's and H4350 from 38 to 41 grains, the top row was some other loads. I potentially see 2 nodes, one between 38.5 39.0 and another between 39.5 to 40.0. What do you guys think? I tried loading 41.5 but I couldn't seat the bullet, there was too much powder in the case. No pressure signs at 41.0.

Thanks

 

[Tim Singleton]

I would load 31.3 and 32.0 at different seating depths as mentioned, but shoot you groups further out (300) if possible. Not going to be able to tell much if all your groups are in the .1's.

Read the thread title.

I did, I've posted how this worked for me on the last page. I also believe that it has it's limits. If he shoots the next test as you instructed and he get's all one ragged hole groups (which it appears the gun is capable of), what does that tell him? He learns nothing. But if he were to shoot those same loads at 300+, he could get some valuable info on what seating depth works for that charge.

:-X

Ok Erik, this is what I AM going to do. I HAVE tested a load at 100 yards (one hole) and KNOW that it IS a good load at 300 also. I have NOT played with the seating depth though. So I AM going to vary the seating depth by .003 as you say is best and shoot the loads at 100 and 300. I will first post the 100 yard target and let you decide which load you THINK will be best at 300. Then I will post the 300 yard pics shot with the same loads at varying seating depth's on the same day. Going to put you on the spot and we can both see at the same time if 100 yard testing has it's limits or not. Sound peachy? ;D

Jsthntn247. I'm curious to see the pics from your testing.

 

[jeniusit]

Hi,Erik
this is my test with my BCM barrel block 6.5 x 47L with Lapua Scenar -L 136 and IMR 4350 from 38.5 to 41 grains. I don't see any node, but only 3 shots in one hole with 39.5.
Neck 0.012
bushing 0.286
neck tension 0.002
cci450
oal 2.023 at the land
free bore 0.005 in the land
col 2.736.
2904 fps
16.64 ES
08.30 SD

What do you think?
I tried loading 41.5 but I couldn't seat the bullet, there was too much powder in the case. No pressure signs at 41.0.

Which can I do before the next match at 600 yd on 21/07/2013?

PS: The first down target is 38.5gr,2815fps,03.93 ES,02.00 SD

Thanks,
Jenius