Blown primers with no other sings of pressure.

land308

land308

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My load is 26 grains of w748 with 55 grain varmint nightmare bullets from midsouth. I worked this load up last year and fired 500+ rounds with no problems. Brass showed mild cratering which is par for the course with this gun even with mild loads.
This year I loaded them up on my dillon press. Noticed right away that the were tight in the chamber. I figured I did not get the sizing die adjusted quite right. I never experienced heavy bolt lift. I had a few flat primers which I figured was from leaving the round in a hot chamber. Out of 450 rounds I blew about 4 primers and finally had one puncture which dislodged my extractor on my savage 12fv. I just pulled the last 50 round and measured each charge. They were perfect 26 grains or slightly under. I downloaded them to 24.5 grains. So what is the deal? I would expect to get pancaked primers and heavy bolt lift before blown primers. These were new cci small rifle primers. Brass was trimmed this loading. I did switch to a different lot of powder which I usually don't worry about because I usually back off from max enough to give myself some room incase the next lot is hotter. Thanks for any input.

notflatprimers.jpg


blownprimers.jpg


 
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You sure you didn't accidently use pistol primers?

I'm loading 26.5 gr. of 748 with a 55 gr. and I've never seen any kind of pressure signs, and I get a bunch of loads out of the brass without the primer pockets loosening up.
I use 450 mag. primers, though, since Speer recommends them with ball powder like H335/W748.
I started off using 400's though, and didn't see any problems.

Even the one in your pics that pierced isn't flattened from pressure. The only one I can see that looks like it's even close to flattening is the upper right one.

Here, dissect one and see what's up:

Primerspecs.jpg


I believe pistol primer cups are .017" thick, but don't quote me on that. They're thinner than .020", though.
 
Changing lots can cause some problems. What CCI are you useing?

If you were loading them at 24.5 gr. why are you getting reloads that you checked at 26 grains and above after pulling bullets and checking powder?

Just don't understand why you say you shoot 26gr and reload them to 24.5 and then pull bullets and get 26 and slightly higher. What are you trying to keep your loads at...24.5 or 26 grains?

Just curious, or maybe I read into this too much.
 
Is it possible that CCI is using a softer metal alloy in their small rifle primers??

The reason I ask is that I'm also getting some flattening and cratering out of my latest batch of primers that I wouldn't expect to see out of some fairly light loads. Maybe I'll try to locate another brand of primer and see if I get the same result.
 
The CCI 400's have caused similar issues with H335 in hot weather for me. Go to Remington 7 1/2 or CCI BR4 that migfht help.
 
Quote:They were perfect 26 grains or slightly under. I reloaded them at 24.5 grains. So what is the deal? Don't know, but it sounds like you've discovered a new way to "make" powder.
 
You have an over sized firing pin hole in the bolt for one thing.

Go to a 7 1/2, CCI450, or CCI BR4 that all have thick cups.

There is a world of difference in pressure when comparing the top picture and the bottom picture...I wonder what's up with that?

In 14 twists, I have loaded 26.5g of 748 in many rifles with 55's with no sign of pressure at all.

I think that it may be possible that the powder measure on your dillon may be out of whack.
 
In the top pic, i see no pressure signs. Your FP hole is too large, causing that cratering(IMO).

The bottom pic however shows moderate flattening...a sure pressure sign. It's not consistent though....something's not right with the loads.

Also, i notice some sort of "gouge" on the edge of each primer. The blowouts are right in the same place as the "gouge" on the others. It looks like theres a burr on the boltface or the seater you might wanna look at.
 
After looking more at the pics....something else strikes me as odd. I dont really know how the FP strike can vary so much. Some of them are struck dead-center and some are struck many thousandths off-center. That would further indicate to me that your FP hole is EXTREMELY large or the boltface is way over-cut.
 
Sorry. I was not very clear. my original load was 26 grains. I later pulled the last 50-60 rounds and downloaded then to 24.5 grains. when I pulled the bullets, I measured the powder in each on my beam scale to make sure the dillon was throwing good powder charges. It was. All of the original loads were 26 grains or slightly under.
 
I looked at the bolt face and I can see a couple of dents where the marks are on the primers. I don't know what to make of that. I may have a smith take a look at the brass and bolt.
 
Some more picture in the daylight. These were all from the last 2 weeks.

These are the other 2 blown primers
blown2.jpg

blown.jpg



Same load in remington brass. looks pretty mild to me.
rp.jpg



Winchester brass with some 30 yr old federal primers.
These primers were flatter but not terrible.
federalprimers.jpg
 
Quote:
Noticed right away that the were tight in the chamber.

Resize a fired case, black it w/sight black or magic marker and chamber to see where it marks. May need to re-adjust your dies since it appears that you have changed presses since last year.

Another area to check would be COAL. If ogive different on your bullets or seating not quite deep enough, "freebore" or bullet jump is reduced which can increase breech pressure. Be sure bullets not contacting rifling (unless they were so seated last year).

Quote:Brass showed mild cratering which is par for the course with this gun even with mild loads.


As has been stated, firing pin hole a bit oversized in your bolt, but piercing does not seem to occur near the firing pin strike.

Quote:I blew about 4 primers and finally had one puncture which dislodged my extractor on my savage 12fv.

The pictures show pierced primers. Did any actually fall out of cases? Reason I ask is that our club once got a bad batch of primers which the manufacturer replaced. Several of our members experienced pierced primers exactly as pictured and when we returned them, Mfgr. stated they got a bad batch of metal which caused the problem. Wondering if you might have a primer problem as opposed to a pressure problem.

Quote:hikerX2:Also, i notice some sort of "gouge" on the edge of each primer. The blowouts are right in the same place as the "gouge" on the others.

There is a mark on the primers as noted by hikerX2 above that coincides with the piercing that could be weakening the primer cups. I'd check your remaining primers to see if they show this mark from factory, if not inspect your seating stem as suggested by hikerX2.

Regards,
hm
 
You really need to get the bolt face repaired so the firing pin doesn't have so much play in it... also, closely inspect your primer feed area for some kind of debris that my be damaging your primers in the loading process...

I don't use a Dillon, but there have been times when I've found a small brass sliver in the primer seating area after I've prepped the brass (trimmed, chamfered, and reamed) that causes a deformation somewhere on the primer.

I've used the same approximate load of W-748 that you are using and never had a problem with it, in any way...as it's well below published max loads...and that's with Winchester SR primers, as well as CCI magnum primers..

Either your primer pockets or your primers appear to be getting damaged by something on the ones that are blowing out..
 
Quote:I was using cci 400. I am sure they were rifle primers. I checked after the fact to confirm.

Okay. I'm still convinced it's a primer problem. The firing pin indented those a whole lot deeper than what I would be comfortable with. They may not be pistol primers, but they sure act like them.
 
I think if you've got too much headspace, the primer gets flattened. I could be wrong, though.

I'm going by pictures, it can be misleading. First thing I would do is take a cratered primer, disassemble it, and measure the cup thickness.
 
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