Small gas leak around primer.

[keen.on.it]

Decided to give 130gr Barnes TTSX a try in my 270 winchester to potentially use on an elk hunt in a couple of weeks, loading them behind h4831 and CCI BR2 primers in new winchester brass. Worked up the load from 55gr to 58gr in one grain increments and from there went in .3gr increments where it was started to compress the powder. All was well until I got to 59.6gr where the first shot the case looked good, primer not flattened, no cratering, no heavy bolt lift, and from the second shot, all was the same, except there was a small leak around the primer. I ended up wiping off the black soot, but I'm pretty sure it was the case on the right.
I read on an old thread that this could be from a low pressure load but I figure that is not my issue here. Inconsistent primer pockets? What's going on here?

 

[Zen Archery]

Primers and case look healthy. Did you measure primer pockets prior to loading? Looks good to me.

 

[keen.on.it]

I did not, visual inspect, neck size and load has been my go to thus far. There have been a couple of cases where the primer seemed to slip in a lot easier than most and I just tossed them. The ones for this load were all what I would consider normal from the very limited experience I have.

 

[keen.on.it]

All new brass so far, I have yet to load any once fired.

 

[DoneNOut]

Sometimes left over oils or condensation in the barrel will manifest their way to the bolt face. I found this out when I didn't have the chamber completely free of oils. Is your bolt face etched at all? A slight ring is normal, pits and such not good.

 

[keen.on.it]

I just checked that actually, bolt face not etched, a slight ring that was mostly removed by wiping it with a q-tip. I also removed the primers from the cases expecting the one to have carbon along the side of the primer but it was clean. Ahhhh, maybe condensation?? I was cooling my barrel on my dash with air con as it was hoooot as and I figured barrel heat was what was sending the third shot of each group high and right to the exact spot in relation to the first 2 shots of each group.

 

[243winxb]

Pressure Signs- Your over pressure with that lot of powder. See #3.

 

[243winxb]

Link at bottom of page.Powder Lot Variations: A Case Study with H4831 - Hodgdon Extreme.

About 10% variation in burn rate, between lots.

 

[MagnumManiac]

You may have a scratched wall on your primer pocket, or a damaged primer cup, it's rare, but does happen. I cannot see a deformation or pinhole in you pics, so maybe pop those primers and take a look at both.

Cheers.

 

[VinceMule]

Primer edges are round, lettering on case head in as new condition, no pressure indicated. I de prime with a hand deprimer to check for loose primer pockets. Check and see if the flash hole is off center on this case, rare on winchester brass unlike lake city.

Also, on fire forming the cases, there maybe some gas blow back that ended up on the bolt face, I am guessing here of course.

From what you describe, you are not having typical indicators of gas leakage from the primer pocket.

In my rifle, I am shooting the 130g ttsx seated .050 from the lands in win brass with a cci 250 primer, no problems at 60.0g of H4831, recent manufacture.

 

[roadrunner1]

In my experience gas leaks occur under high pressure. low pressure sign is usually primer backing out slightly.

 

[VinceMule]

In my experience gas leaks occur under high pressure. low pressure sign is usually primer backing out slightly.

with additional case stretching! I don't think that these primers had backed out, they are too round on the edges.

I would ask if there was any black soot on the neck/ shoulder area?

 

[roadrunner1]

In my case the primers backed out slightly until I used more powder. I another case I was close to the limit on max powder charge and did have primer gas leak right on the edge of the primer pocket with black soot, once I lowered the charge all was well. In another case I had gas leaks with medium charge so I called Winchester and they took my primers and replaced them. The primers were nice and round with gas leak, but in my case the leaks were very noticeable.

 

[RegionRat]

I you don't find pitting on the bolt face, coupled with little or no evidence near the primer on the empty cases.... then you should re-inspect the cases and proceed with an extra eyeball going forward.

Watch the primer pocket inspections, and watch the installation. Examine each and every shot on the next session and stop if you see a problem.

Normally, a primer cup rupture isn't difficult to verify, and a leak between the primer cup and the brass pocket is also easy to find.
That you got soot but are not finding evidence of a primer leak is better than finding damage to the bolt face, but you should still clean up and double inspections to be in the best position to debug that soot.