i have always turned my necks for consistent thickness. my question is what is the optimal neck clearence? i mostly shoot steel at 1000-1500 but i like to tinker with things. i turn all my adg to a thickness of 0.0125. In my 6.5 PRC i have a .297 neck. At .0125 thick on the neck, i am getting almost 8 tho expansion on the neck. i am just wondering what your thoughts on how much is to much or to little.
optimal neck clearence
- Thread starter inline6power
- Start date
a couple years ago i had my first real failure with a case on my 6.5 prc. This was on the 14th firing on this adg brass. I was using 50 pieces as test pieces when adg brass first came about for the prc. i am almost certain its because i have almost 8 tho of neck clearence and the necks expand so much then get resized back down. The gun shoots lights out this way and the only way to get the adg to clean up when i ran this batch was to turn it down to 12.5 tho thick. Since the gun shot so well like this i continued to shoot all the brass turned down to 12.5 thick. The reason i am asking the question is because of this failure that popped up in my timeline this morning.
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just kissed the shoulder. Used my idod to turn all my necks. I mean it made it 14 firings but i am also thinking because the neck shoulder junction is the largest step from thin neck brass to thick shoulder brass and by having a larger neck expansion thats what did it but i am unsure. i anneal every firing and fl size. I use sac dies with a .287 bushing and a .263 mandrel and after spring back i get right at 1.5 tho neck tension so i am not overworking the neck like crazy but going from a fired case of almost .297 down to .287 and expanding back out to .2885. A loaded case is .290 so i am guessing the failure came from over expansion over time.
only turned them when they were virgins. i should have turned more but it was just the once. These are ran in a xm action using berger 156s and the bearing surface is just above the neck shoulder junction. loaded round for me is 3.115 coal
15.5 tho on avg. I got alot of them new that had a 1.5 to 2 tho variance so i turned them all to 12.5 tho thick to uniform them all. Is turning this brass needed? probably a big negative but i like to control the things i can and tinker so i turned them to uniform thickness. this is just a steel plinkin gun but also i like to get as much precision as i can. So yes i am probably way over working the necks. probably need to get a .294 neck chamber instead of the .297-.298
i dont know. thats a good question that i dont know the answer to.
Changes as the wind blow. Minimal was king for many years. We as a group understand the brass flows as we size and fire. 0.004 to 0.006 diametral with annealing is not an issue.
Thin necks might behave differently. I have some thin neck 30 br brass that makes me wonder. No solid experience just makes me wonder.
Thin necks might behave differently. I have some thin neck 30 br brass that makes me wonder. No solid experience just makes me wonder.
@inline6power This thread might be of interest.
Only had the problem with one batch of cases, put it down to cutting too deep into the neck (as others have commented above). Try putting a bent paper clip inside one of your fired cases and feel for any deformation or groove at the shoulder/neck junction where the separation occurs.
Neck Turning - Too Deep - Pics
Just for information, I thought some might like to see these pics. One batch of cases started to lose necks on firing - left pic - on the 4th reload. I sectioned a case to show what happens if the neck turning process cuts too deep on the neck shoulder junction. In the right pic you will see a...
forum.accurateshooter.com
Only had the problem with one batch of cases, put it down to cutting too deep into the neck (as others have commented above). Try putting a bent paper clip inside one of your fired cases and feel for any deformation or groove at the shoulder/neck junction where the separation occurs.
Interesting. Appreciate the link. Mine broke exactly as yours did. I use an idod for my neck turning and use a 30* cutter to match the 30* shoulder of my 6.5 and 300 prc brass. I was able to make it 14 firings before I had a failure on that batch of adg brass so not like it failed quickly but I was trying to understand exactly what caused it to fail. I am starting to believe it was cause from me overworking the thinner necks. Having a loaded round od of .290 and when I fl size with a bushing down to .285-.286 then mandrel back up to .288 and then firing and expanding them on firing to .298 that was the problem. Interesting to see mine failed exactly as yours.
I’m certainly no expert and I have CRS really bad but it seems you may be taking a shade too much at .0125 and getting 8 thousandths expansion. That’s a lot of brass work.. My finished Win brass in 308 and 6.5-06 is usually around .014 to .0145. I turn LC Match for my AR 10 to .0145 to .015. When I turn I’m basically skimming just enough to clean up thick spots And true the wall thickness. I’d say .005 +/- .001 expansion is fine. My 6.5 Grendel is also around .014 finished IIRC. I don’t have my journal in front of me but I can check these figures if need be.
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