Bolt face cratering,,, Any thoughts--Problem Solved+++
Have 2 bolts that both have had the same problem. Bolt face cratering, Loads are not hot, 69, 55, 50 grainers in new LC brass. All per loading book info.
Anyone been there, done that, have a solution to the problem. Less that a couple of thousand rounds on each.
Did run a suppressor on about half of the rounds
what primers are you running?
poss. failed or cracked primers.
do you verify how your primer pockets look prior to popping primers for reloading?
Are you getting pierced primers? Are you somehow getting blowback around the primers?
Have you scrubbed the heck out of your boltface to be sure it is cratering and not just crud?
Gas is leaking around the primer and hitting the face of the bolt. Your's is the worst case I've ever seen. Had the same thing happen when I used Remington 6 1/2 primers...they are not built for .223 pressures and are too thin to hold in all the pressure/gas. There may be other primers that also allow this to happen, not being designed for the higher .223 pressures, but DO NOT USE REMINGTON 6 1/2 PRIMERS IN .223/5.56MM RELOADING!!!!!
The other possibility is that too much of the primer crimp from military type brass was removed prior to reloading; that would also allow gas to leak, as there would be less metal to help hold in the pressure.
One final thought...you posted "new LC brass", indicating to me never fired before. Could this be brass that was rejected due to improper primer pockets so was never loaded and somehow was sold on the open market to unsuspecting reloaders?
Solutions: Use CCI #41, Wolf KVB223M, Wolf KVB556M primers (I'm sure there are other primers also hard enough for .223 pressures). Inspect brass and toss any which show signs of having gas leaked around the primer (gas leaking can cut small grooves in the primer pocket which will allow even more gas to escape the next time. Inspect brass and toss any in which too much of the primer crimp has been removed, allowing a bevel to be obvious around the newly seated primer.
When the LC brass was proceed to remove the primer staking, looks like either the pocket was over sized, or over edge beleved, and these conditions are causing the primer to pocket not to seal off fast enough/ have excess blow by before the primer seals off to the pocket.
Furthermore, on the heaver ammo, might want to go a tad faster burning powder as well. I say this since Fed had problems with their first gold match 223 ammo with a powder that burnt a tad too slow, and caused problems in the auto as well (sooty cases and primer blow by).
Bottom line, the bolt face is being plasma cut by the gases leaking out from around the primer cup to primer pocket, and it's either being caused by the pocket, or powder not burning fast enough to pressure seal off the primer to the pocket fast enough. Also, if you unified the flash holes, may have over sized them to cause more of the problem as well. To add, make sure that you are firmly seating the primers into the primer pocket. That little extra primer seating pressure does help to compress the primer cup to the case primer pocket so the metal has less to expand to seal off to the pocket at ignition.
As for suppressed, granted that it will cause more barrel back pressure, but by the time it does that, the primer should have already sealed off to the primer pocket. So the problem that you are having is the primer blow-by back to the bolt face before the bullet has even traveled a few inches down the bore, and that boils back to how well the primer is fitting the case primer pocket to begin with (if you are sure that the ammo is not going over pressure, and should be able to read the primer to see if that is happening).
To add, double check the primer to make sure that it's not flattening out/showing signs of over pressure. Since you have LC brass, it may have only been primer pocket processed, but still not trimmed. With a case that is not trimmed to the correct over all length, this longer brass can be entering the throat of the barrel instead of stopping before the last of chamber cut, with this causing ammo over pressure problems even though you are still within the loading guide lines. So on that note, post a couple of photo's of the spent case primers still in the cases so we can confirm that the ammo is not going over max working pressures.
Primers not pierced, usual amount of pressure required when seating,, not loose feeling. Brass is new non crimped LC.
Wholebunches: switched primers years ago while shooting highpower,, from WW,, to Rem 7 1/2's. Maybe that is the problem.
The new LC brass specs out okay on length, & dimensions, head space.
Using H4895, RL15, and Varget for more years than I can remember with no problems until now.. Maybe the 7 1/2's are allowing gas to escape around them.
7 1/2's are suppose to be OK for .223 from what I have read. Please check the primer box you've been loading from to make sure not marked 6 1/2.
Checked, they are 7 1/2 benchrest
Do you have any of the fired brass?
What does the brass and the primers look like?
Looks like your have some serious leaking around the primer.
Been looking at the primer ends with a 16x loupe, can't really detect and gas blow by, but it has to be happening. Can't tell with the suppressed fired brass as it smokes them up pretty good.
Primers are nice and round with no flattening.. Maybe need to up the charges.
Will be running some tests in the next week or so with the loads been using and some new loads, primers, brass, etc. and take a good microsopic look at everything.
Thanks for all the ideas and suggestions.
Easy way to test, put a bit of scotch tape over the head of the case, and fire.
I bet it gets blown ragged around the primer annulus.
Post a photo of your spend cases, both with a spent primer intact, then a spent primer knocked out to show us the primer pocket (angle view so I can see the chaffer edge and the bottom of the pocket wall as well).
As stated, it could be either the pockets where swagged too large, or when the edge of the primer pocket was chaffer'd to break the edge, it was too deep, without leaving enough primer pocket side wall depth remaining.
Also on the powder, the slower the burn the more blow by you are going to get until the primer fire swells to seal off against the pocket side walls. With heaver bullets, you are going to have to use a slower burning powder to get the heaver round up to speed, but going to too slow of a powder will cause the blow by until primer fire form seal as well.
After lots of testing,, emails, and calls here's the problem.. Some years ago Remington made some small rifle primers (at least 7 1/2 benchrest) that were basically defective. According to them they were last produced in 94, and called bipod primers. These apparently
would leak around the primer, not sealing, allowing gas to cut the bolt face as mine did. This is the info I got from them. I bought 1k (or more) of these a few years ago during the hard to find primer crap years and loaded up my service rifle loads with them which I shoot from time to time at the range. I don't shoot service rifle anymore.
Thanks to all for you ideas and help.
In the pic below the 2 on the left are the newer tripod style,, 2 in the middle fired bipod,,, 2 on the right unfired bipods.
That's some good info .Thanks for posting.
I had some problems piercing primers in a .223 A.I. bolt gun.I kept reducing powder chare until the problem went away but then I was back to a very mild load for a standard .223 .I finally figured out that the primers were to blame.They were Rem 6 1/2 's.I switched to the Rem 7 1/2 and the problem went away.
I went through this exercise in 44mag and 30-06 cartridges. I initially thought it was loose primers and blowby etching my bolt faces (or recoil plate in the case of the revolver, which cannot be repaired). It happened when I switched to a new lot of Winchester primers, all of which were defective when fired from RP brass which has less support (more of a beveled edge) at the entrance to the primer pocket. The net result was primer piercing at the shoulder, which was *very* hard to detect, as you had to hold them up to a light to see a microscopic pinhole in the rounded shoulder region at the edge of the primer.
I no longer use RP brass in 44mag, and I'll never use a Winchester primer again. My bolt/recoil-plate faces thanked me for it. Olin (subsidiary of Winchester) acted like they were interested in the safety of their customers and customer's firearms, asked for samples, which I sent, and they never got back to me.
Switched to CCI for all my guns. Using CCI450 for 223 specifically. After 500 rounds through the AR15, my bolt face is still smooth.
Also at the risk of thread drift, is there a primer less susceptible to slamfires besides the CCI450? The partial strike on the primer when the bolt closes is disturbing to say the least. I know some people use the CCI4X (military) primers, but they're cost prohibitive imho.