Pressure issues 338. Update page 2

B

bobjoe

CGN Regular
Rating - 100%
91   0   1
Location
Alberta
I'm at a loss. When I got my my 338 lapua two years ago I worked up some loads and finally settled on 91gr of h-1000 behind a 300 smk. I shot that load for a year. Then it started to show pressure signs. I had data showing that I could go as high as 92.5 most put max around 90-91. The main sign is/was a donut on the primer. So since I like my face and life I decided to reduce loads. This is where I am at a loss. I am down to 80 gr of h-1000 and I still have a donut on the primer.

To cover the questions before they are asked, The rifle is a Savage the brass is lapua primes are federal mag match. The powder is all the same lot number and I have 20+ pounds of it.

The though did come to me that I could try a different primer but mag primers all share the same thickness.

Thoughts, suggestions?

P.s. This has been all been typed on my iphone. I hope you can understand it.
 
"Pressure Signs" are notoriously unreliable. Your chrony and loose primer pockets are all that are truly reliable.
 
If all other presure signs are normal, i say its fine. When inwas previously shooting 300 winmag, i didnt weight all charges and ended up with charges 1 grain over max. Had to tap the bolt open on a few rounds. Thats a presure sign

Oh and make sure your barrel is not copper fouled too much
 
It is worth noting that as throat erosion progresses, and the throat becomes rougher, pressure will rise noticeably. [How many rounds through that barrel?]
However, 80.0 grains is a long way down from 91 grains.

The donut around the pin indentation may be caused by more than one factor.

1. The pin is smaller than the hole in the boltface, allowing primer material to extrude into that unsupported area.
2. As some have noted, Federal primers are somewhat softer than the others are. [I would try CCI 250's and see what happens]
3. The brass overall length is too great. This causes a "pinching" of the bullet, and subsequently higher peak pressures.
4. You are shooting in considerably higher temperatures recently. [Don't put too much faith in temp insensitive powder claims]

I would be checking the throat of your 338 Lapua with a borescope to see what it looks like. If it resembles alligator skin for the first 4" or so, this is definitely a factor.
Keep us posted on what you find.
Cheers, Eagleye.
 
Last edited:
put my vote in for the primers, yes they may all be the same thickness but its a BAD indicator of pressure, as other have stated some are much softer then others, hell even the same brand from lot to lot may not be the same. i run federal primers, and i get that doughnut around the fireing pin strike at starting loads.. if bolt lift feels the same / good, primer pockets arnt loose after a single fireing , and there is no indication of gas blowback on the bolt face, then id say your good to go
 
skhunter said:
Try shooting a primed empty case and see if you get the same mark on it. Pics?
Click to expand...
You would get a completely different result shooting an empty primed case vs loaded round. When you fir an empty case the primer shoots out but when. You shoot a loaded round the case will push back over the primer because of the pressures.
 
Kelly Timoffee said:
Depends on the primer, some are softer, the Federals will crater long before max loads are reached.

How is the bolt lift?
Click to expand...

I neck size only so it is a little tight because of that but not bad.

Eagleye said:
It is worth noting that as throat erosion progresses, and the throat becomes rougher, pressure will rise noticeably. [How many rounds through that barrel?]

512 rounds through down the pipe.

However, 80.0 grains is a long way down from 91 grains.

The donut around the pin indentation may be caused by more than one factor.

1. The pin is smaller than the hole in the boltface, allowing primer material to extrude into that unsupported area.
2. As some have noted, Federal primers are somewhat softer than the others are. [I would try CCI 250's and see what happens]
3. The brass overall length is too great. This causes a "pinching" of the bullet, and subsequently higher peak pressures. I keep my brass trimmed to the proper specs but I can always try a little shorter.
4. You are shooting in considerably higher temperatures recently. [Don't put too much faith in temp insensitive powder claims] That was one of the first thing suspected as I noticed increased velocity in warmer temps.

I would be checking the throat of your 338 Lapua with a borescope to see what it looks like. If it resembles alligator skin for the first 4" or so, this is definitely a factor.
Keep us posted on what you find.
Cheers, Eagleye.
Click to expand...
 
So I did as many have suggested. I ended up trying several different primer. Still the same results. I went down to 82gr. I ended up taking it to a smith and I was told that the chamber had some rough marks from the tools and almost no free bore. I should have it back in a week or so and that should fix my problems. Ill keep you guys in the loop.
 
You must log in or register to reply here.
Back
Top Bottom