Bought a Winchester 7mm mag at local gun show. Sent it to my Gunsmith and he checked it over and found no major problems. Bought some WW brass,loaded it to some very mild loads. Shot these and [@ 80 rounds] found a small number with split case necks & shoulders. The rest have little to no neck tension after FL resizing. Took the die apart and measured the expander ball and it was within specs. Thought maybe got a bad lot of brass so i went and bought some Hornaday brass. Loaded five rounds [mild loads again] and found the same problem. No signs of overpressure, flattened primers etc... Gun shoots small groups at the range. [Factory barrel that was hand lapped]. Kinda sounds like a chamber problem to me. But the guy who checked it over i trust. So, any thought or suggestions as to figure this one out would be most helpful. Thanks . 12-34hom
Neck tension after FL resizing.
- Thread starter 12-34hom
- Start date
what's the OD of the neck after sizing?
what's the OD of the neck after seating a bullet?
what type sizing die are you using ?
the neck spitting could be due to work hardening. Unlikely after 1 sizing.
could be a bad run of brass. Try buying some Lapua, Peterson, Alpha or some other quality brass. I have some .308 Lapua some of which have over 20 reloads on them. They were annealed 4 times by heating the necks to a dull red with a torch. Never split a neck and brass springback is as good as a new case
Actually never had a neck spit on me ever, even with cheap Hornady and Starline
what's the OD of the neck after seating a bullet?
what type sizing die are you using ?
the neck spitting could be due to work hardening. Unlikely after 1 sizing.
could be a bad run of brass. Try buying some Lapua, Peterson, Alpha or some other quality brass. I have some .308 Lapua some of which have over 20 reloads on them. They were annealed 4 times by heating the necks to a dull red with a torch. Never split a neck and brass springback is as good as a new case
Actually never had a neck spit on me ever, even with cheap Hornady and Starline
Pretty odd. I think full up Unclenick assessment needed.
Did you put powder and bullets in the cases and not sizing the first load?. The brass should be fire-able without sizing the first time.
The split necks make no sense other than a chamber issue. That would take a cast to see, head space might be fine but too large. If the original owner lapped the barrel he may have done chamber work as well.
Are you actually setup right on the sizing end?
Thinking two different problems here.
OP tried Hornady brass after WW with same result of no neck tension.
Clearly the dies is not sizing right. You can't get work hardening with one firing.
Did you put powder and bullets in the cases and not sizing the first load?. The brass should be fire-able without sizing the first time.
The split necks make no sense other than a chamber issue. That would take a cast to see, head space might be fine but too large. If the original owner lapped the barrel he may have done chamber work as well.
Are you actually setup right on the sizing end?
Thinking two different problems here.
OP tried Hornady brass after WW with same result of no neck tension.
Clearly the dies is not sizing right. You can't get work hardening with one firing.
Hounddawg is right. Some measuring is required. Not resizing to hold a bullet is usually caused by brass being work-hardened to the point it has become springy. Per some recent discussion I've been having with a metallurgist, this will occur at a hardness of about HV-195. Splitting, however, happens even higher up as it tries to exceed about HV-220. A normal factory-new neck is stress-relieved to around HV-105, though a Hornady 308 Win brass neck measurement I have came in at HV-124, the hardest among several brands. It is enough to prevent splitting for several reloads and enough for fire-forming the shoulder significantly, as happens when firing a parent cartridge in an Ackley Improved chamber. I've seen several examples now of 308 Win cases that were fired in a 30-06 chamber and the shoulder and neck just blow out until there is a rounded end with a hole in it, but nothing splits starting out at the normal commercial neck hardness.
Another possibility is having some stress-corrosion cracking near to occurring. As they come from the factory, the stress-relieved necks should be pretty immune to that. But if you resize to straighten the neck and then load them with a bullet to an interference fit, you have begun work hardening the neck and then ammonia vapor can initiate micro-cracks that can become full-on splits at firing. The lab test for this involves exposing the brass to ammonia vapors for four hours and then stressing the brass to see if it cracks or splits prematurely. Properly stress-relieved brass does not, but if you have starting re-work hardening and then expose the brass to ammonia vapor, it could begin. It's unusual but possible. We had a fellow put up a photo of some neck splits on loaded ammunition that he had left in a drawer near a kitty litter box for a year, and just that trace of ammonia was enough. Lots of ammonia and a few hours, or a little ammonia for a long time will do it.
It possible you can get a good clue by measuring a surviving as-fired (not yet resized) case to compare to a new, never-fried case. You are looking for abnormal differences. You want to measure the diameter of the case necks in the middle of the neck, the body diameter where it meets the shoulder, and, if you don't have a good way to measure from the case head to the shoulder at the SAAMI 0.420" basic dimension (datum) diameter, then use a caliper to measure from the case head to both the top and bottom shoulder corners as best your eye can determine their locations. Report all those numbers for both the unfired and fired-but-not-resized cases so we can get a sense of what the brass is experiencing.
One other odd thought: can you specify the light load you were using?
Another possibility is having some stress-corrosion cracking near to occurring. As they come from the factory, the stress-relieved necks should be pretty immune to that. But if you resize to straighten the neck and then load them with a bullet to an interference fit, you have begun work hardening the neck and then ammonia vapor can initiate micro-cracks that can become full-on splits at firing. The lab test for this involves exposing the brass to ammonia vapors for four hours and then stressing the brass to see if it cracks or splits prematurely. Properly stress-relieved brass does not, but if you have starting re-work hardening and then expose the brass to ammonia vapor, it could begin. It's unusual but possible. We had a fellow put up a photo of some neck splits on loaded ammunition that he had left in a drawer near a kitty litter box for a year, and just that trace of ammonia was enough. Lots of ammonia and a few hours, or a little ammonia for a long time will do it.
It possible you can get a good clue by measuring a surviving as-fired (not yet resized) case to compare to a new, never-fried case. You are looking for abnormal differences. You want to measure the diameter of the case necks in the middle of the neck, the body diameter where it meets the shoulder, and, if you don't have a good way to measure from the case head to the shoulder at the SAAMI 0.420" basic dimension (datum) diameter, then use a caliper to measure from the case head to both the top and bottom shoulder corners as best your eye can determine their locations. Report all those numbers for both the unfired and fired-but-not-resized cases so we can get a sense of what the brass is experiencing.
One other odd thought: can you specify the light load you were using?
Thanks all, it was a sizing adjustment that solved this problem. Turned the sizer die down to touch the shellholder. Backed the ram off, turned the sizer down another 1/2 turn. First belted magnum round i have reloaded for. Really appreciate all replies. Thanks.
I have a Springfield Armory Govt model scope gen 2 on this rifle. Its reticule is set up for 308 168 grain match round at 2600 fps. So i find loads as close to that velocity as possible. That particular load was 162 grain Hornady ELD behind 65.5 grains IMR7828 ssc. OAL 3.290. Very mild and quite accurate.
I have a Springfield Armory Govt model scope gen 2 on this rifle. Its reticule is set up for 308 168 grain match round at 2600 fps. So i find loads as close to that velocity as possible. That particular load was 162 grain Hornady ELD behind 65.5 grains IMR7828 ssc. OAL 3.290. Very mild and quite accurate.
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You weren't fully resizing by just half a turn and that initiated splitting and caused failure of the necks to resize enough to grip bullets? I don't see how that's possible. Lots of folks under-resize their belted magnums to headspace on the shoulders to extend case life. Lots of others partial resize to get better neck centering in the chamber. I think there pretty much has to be something else going on that we are missing.
Correctamundo, Unclenick. I've sized my 7mm Remington brass (after the first firing) to avoid moving the shoulder back in multiple rifles since the 70s. I get 5-7 loadings because my 7s have all been the most accurate at max listed loading. Only have neck tension/splitting problems after.
Like Uncle Nick points out a lot of us only size 3/4 of the neck to get better alignment but the neck splits still puzzle me. I am being completely honest when I say I have never had a neck split. I shot an average of 50 - 100 rounds a week the last few years, sometimes more. I have had a one case split, one head separation and two maybe three necks just separate completely at the shoulder junction but never a neck split over the course of the last ten years.
I am not using magic pixie dust or a 1500 dollar annealing machine so just the mention of a case split makes me curious. Ninety nine pointy nine percent of my cases get retired because of loose primer pocket after the seventh to tenth round. I am curious to see what you guys figure out on these splits
I am not using magic pixie dust or a 1500 dollar annealing machine so just the mention of a case split makes me curious. Ninety nine pointy nine percent of my cases get retired because of loose primer pocket after the seventh to tenth round. I am curious to see what you guys figure out on these splits
Is that based on the cartridge neck laying in the chamber neck bottom when fired?
Accuracy was not your question. You actually answered your question in your responce . If the case is being pushed hard by the bolt because the shoulder to case head length got longer . Then the neck would not be sitting at the bottom of the neck section of the chamber either . The whole cartridge should be centering it self do to the shoulder press fit do to that extra length .
Id also add that unless the body diameter is “fully” caugh caugh sized down . When that partially sized body is sitting at the bottom of the chamber that should keep the neck slightly elevated in the chambers neck section.
Id also add that unless the body diameter is “fully” caugh caugh sized down . When that partially sized body is sitting at the bottom of the chamber that should keep the neck slightly elevated in the chambers neck section.
Bart and Metal yall oughta go over and read this old thread on the LRH forum. Apparently the "small chunk of rodent fecal matter in a violin case" * argument has been debated hotly for years.
https://www.longrangehunting.com/threads/neck-tension-effect-on-accuracy.178616/page-2
Me I could give a darn, make the ammo as perfect as I can with my what skills and tools I have and let the paper be the judge
* censor did not like the T word
https://www.longrangehunting.com/threads/neck-tension-effect-on-accuracy.178616/page-2
Me I could give a darn, make the ammo as perfect as I can with my what skills and tools I have and let the paper be the judge
* censor did not like the T word
You keep saying things that make your question moot so why did you ask it ?
Original question that started us on these last few post .
Bart said:
which was to Unclenicks statement
UN said:
Bart you have shown several times now in the last few post and I have as well that the case neck is never sitting on the chambers neck bottom when fired so why ask a question you knew the answer to ? You keep making statements that answer your own question so it seems you're just writing to read what you wrote or am I not following what you are saying correctly ? I'm not trying to be combative , I really don't understand your point to this line of inquiry ? At first I thought you were looking for an answer but it seems you know it already ?
I'm making you think about the realities of case position when fired.
Sierra's rat thing in a violin case (or punch bowl, sometimes used) shot their best match bullets inside 2/10 MOA with 10 shot groups one after another after another. I've seen them and knew well the man who coined that phrase.
