One thing I have had happen last two trips are. Sunshine on my ammo. My range has covered roof. but last 2 trips one early morning and one late in day sun has been shinning on my bench (cover only blocks sun midday). I didnt understand what the heck was going on, 1st trip as I shot my velocities kept going higher and higher finally to point of over pressure sticky bolt and hard ejector marks (velocity increased over 75fps with just 25rds shot). All from same load session. Thinking my powder measurer must of been gone wild. So doubled measured this last load up between balance scale and digital. Same thing every shot started to speed up and pressure kept going up. I finally noticed when I picked the next round it was noticeably warmer than outside temp which was 50 and sun was directly on ammo, it was in a clear plastic reloader type box but top was off. I'm shooting 6.5 staball which is supposed to be temp stable mostly. Yet as the sun warmed up my box of ammo it changed in the hour of shooting from start velocity of 3120 to 3210 just from sun heating it up. One I would say 6.5 staball is NOT very temp stable based on this. I dont have a bore scope to check for carbon ring. But gun has only about 65 shots since a cleaning, it was a normal cleaning with hoppe benchrest to get mostly copper shooting Hammer bullets. Gun only has about 300 shots total on it and I normally do a hoppes benchrest cleaning about every 50-60 shots ( i have not done a cleaning for carbon ring specifically, just standard cleaning). I have a hard time believing sun warming rounds was only cause and maybe carbon ring buildup is also causing it. Anyone else have these issues? In these newer tighter tolerance PRC's is Carbon ring build up that fast? Thoughts? Never had this happen with my tamer rounds like 308, 6.5cm or even 7 RM. Barrel is 22" suppressed on 6.5 PRC I use staball to get 100% burn since the slower powders dont burn out in the 22" shooting the 124hh.
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Been doing a lot of shooting and load work.
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308win
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I doubt very seriously that your cartridges in the sun at 50° would change 70fps? Maybe in 100°? Carbon rings sneak up pretty fast sometimes and I'd be willing to guess thats what's happening? My experience with cans is usually performance degrades after 40ish rounds. Speeds go up and accuracy falls apart. Have a friend running a 6.5PRC with a can and his pretty much hits a wall at 40 rounds. If you don't have a boroscope, I highly recommend one....they'll give you the answers pretty quick. Good luck
PddPdd
Well-Known Member
I'm not sure what's going on, so here are a few more question to help diagnosis:
1. Was all copper removed from the barrel prior to shooting Hammer bullets? (Manufacturers recommendation)
2. How much time between consecutive shots?
3. Do you have a bore-scope to check for carbon/copper in the barrel?
1. Was all copper removed from the barrel prior to shooting Hammer bullets? (Manufacturers recommendation)
2. How much time between consecutive shots?
3. Do you have a bore-scope to check for carbon/copper in the barrel?
Gary in MD
Well-Known Member
There's been warnings in loading manuals for many years not to leave ammo loaded with ball powders in direct sunlight. Maybe you are close to a maximum load for your rifle and then leaving them in direct sunlight to heat up is enough to cause pressures to get too high.
Yeah, this load work up was only one grain under pressure sign. So that is what is happening. But this ball powder is supposed to temp stable or at least somewhat. So at 50 degrees even in sun seems 75 to 90 fps seems a bit much. Thats why I'm thinking maybe carbon ring is a factor. Maybe on this gun I just have to clean more often and with a better carbon cleaner. Several years ago I was hog hunting in box stand and it was 95 and didnt realize my gun was in direct sunlight from light shining thru window, hog came out I grabbed AR it was very hot but I could hold it, shot hog killed it but round blew primer, that was with CFE223.
Yes all copper was removed, been using the HH for a long time. I was shooting 3 shot groups waiting about 8 to 10 mins between groups. 50 degrees with head wind 10mph barrel cooled very fast.
Mikecr
Well-Known Member
I agree with 308win, but what I do to manage this is to always pull ammo from my front pants pockets.
Hot or cold, range or field, development and hunting, my ammo stays nearest testicle temp!
Hot or cold, range or field, development and hunting, my ammo stays nearest testicle temp!
waveslayer
Well-Known Member
What Chrono are you using
