25 creedmoor pressure issues

[Catalyst686]

JGS 25 krud reamer
Peterson virgin 25 cm srp brass
REM 7.5 srp br

My initial load was to form the shoulders to my specific chamber
41.5 win 748, cheap 100 gr ppu bullets
Seated .200 into case (short flat base bullet)

What I initially thought was ejector smear, turned out to be ejector stamp- severe.
Backed down 3 gr- same result
Backed down to 36.5- same result
Heavy bolt lift off and on throughout this whole process, lighter loads produced “less heavy” but still harder than normal lift.
All rounds chambered like butter.

Tried what my planned final load components would be to see if the ppu barrels were causing this or possibly the powder-
Started low at 39 gr h4350
Berger 135
Same result, bullet seated .20 off lands

I’ve been chasing this around all year, bad powder? No, ppu bullets out of spec? No. Burr in the chamber? No

Cases form to same shoulder measurement after firing no matter what load

Action is high end and reputable in the custom rifle world , I’m not mentioning the manufacturer right now as they offered to look at the rifle, I swapped out another bolt for the action as my gunsmith thought that was the issue originally. Chased around the possibility of the ejector being out of spec, no.
Gunsmith is high end and reputable

Barrel blank from xcaliber, reamed with brand new reamer mentioned above.
Load data from quick load to form the brass shoulder to my chamber before starting development with h4350 and bergers.

Just wanted to see if anyone has had a similar experience, all I can guess is the action or the chamber.

 

[CK1.0]

The primer in your pic isn't cratered at all (which is strange if you're getting heavy bolt lifts). I usually notice cratering around the primer first (IME, which is admittedly limited, since I never really load close to max pressure).

I've seen ejector imprints like that on new brass from loads that were nowhere near max a couple of times, so IDK if that's telling you the whole story (or even anything at all)...

That said, 25CM is wading into the wildcat waters a little... wonky reamer specs (like it or not, you're an early adopter) and/or brass that isn't quite right (I doubt that Perterson stuff is widely used) would be my prime suspects...

 

[Catalyst686]

The primer in your pic isn't cratered at all (which is strange if you're getting heavy bolt lifts). I usually notice cratering around the primer first (IME, which is admittedly limited, since I never really load close to max pressure).

I've seen ejector imprints like that on new brass from loads that were nowhere near max a couple of times, so IDK if that's telling you the whole story (or even anything at all)...

That said, 25CM is wading into the wildcat waters a little... wonky reamer specs (like it or not, you're an early adopter) and/or brass that isn't quite right (I doubt that Perterson stuff is widely used) would be my prime suspects...

I have zero other pressure indicators whatsoever, I was convinced the ejector was too long towards the beginning but it ended up being fine. I send the barreled action off today so we’ll see what happens. This project is 2+ years old, yes one of the early adopters, project got out on hold after the blackjack bullets fiasco, never got around to shooting it until a few months ago.

 

[Catalyst686]

I have zero other pressure indicators whatsoever, I was convinced the ejector was too long towards the beginning but it ended up being fine. I send the barreled action off today so we’ll see what happens. This project is 2+ years old, yes one of the early adopters, project got out on hold after the blackjack bullets fiasco, never got around to shooting it until a few months ago.

With the exception of the bolt lift obviously since the ejector is stamped in the case head, no visual signs is what I meant

 

[Anzac]

My guess is still excess pressure.
Would you have checked headspace with a set of gauges, verify/ measure case oal and measure case neck thickness/ for clearance? If not I’m sure they will be. You may have had a batch of hard as fuck primers. I could also be way off base.
At least you didn’t continue, played it safe and had it checked.

 

[Catalyst686]

My guess is still excess pressure.
Would you have checked headspace with a set of gauges, verify/ measure case oal and measure case neck thickness/ for clearance? If not I’m sure they will be. You may have had a batch of hard as fuck primers. I could also be way off base.
At least you didn’t continue, played it safe and had it checked.

I've used them same batch of primers with multiple other rifles without issues, different cals.
Checked HS
I get .004 of shoulder growth no matter which load it was
Neck tension was checked with all fired cases, it checked out fine

 

[Anzac]

Goodo then.
By mentioning the neck I didn’t mean neck tension, rather the case wall thickness+projectile “width” vs chamber neck “space”.
All the best with it.

 

[db2000]

I’d call that moderate ejector pressure sign. Severe will dig up the brass and your fingernail will catch it. It will be visibly raised. You know the load is hot then. Next primers will blow.

 

[Catalyst686]

Goodo then.
By mentioning the neck I didn’t mean neck tension, rather the case wall thickness+projectile “width” vs chamber neck “space”.
All the best with it.

I’d call that moderate ejector pressure sign. Severe will dig up the brass and your fingernail will catch it. It will be visibly raised. You know the load is hot then. Next primers will blow.

The picture makes it not look as bad, it'll definitely catch your nail, with light at the right angle I'm able to see height difference.

 

[Catalyst686]

Goodo then.
By mentioning the neck I didn’t mean neck tension, rather the case wall thickness+projectile “width” vs chamber neck “space”.
All the best with it.

How are you measuring chamber neck space diameter, I can measure the neck length of the chamber but not the width.

 

[iceng]

Bolt out, depress ejector pin with something, like a pen or punch or whatever. Make sure it goes marginally under flush. If it doesn't,.. found your issue.

Remove ejector, clean the hole and pin. It can get gunk behind it. Rarely your ejector pin is too long.

Lastly, is the hole that the ejector is in, is it sharp ? It should have the smallest deburr. Otherwise it acts like a knife edge on the brass, cutting / shaving it. Thus, looks like pressure signs.

 

[Chris1972]

The ejector not going below flush is a great answer but if I read it correctly he tried a second bolt with the same issues.

 

[Anzac]

It’s the constant ( two different bolts= different ejectors) Hvy bolt lift that would have me chasing pressure still, tho that primer seems unaffected…
Brass too big/ chamber too small? Custom tight neck with reamer maybe? Your GS will know. Cognisant you said new reamer but a worn reamer= undersized chamber dimension, body or neck? So will out of spec reamer.
Happy to be corrected but the allowance for spring back is 1-2 tho? Add that to your fired & unsized brass and compare to reamer print. 2x neck wall thickness( use a tubing mic) + .257 and compare to your chamber dimension.
GL having it solved. I’m sure greater minds will set you right.

 

[LR1845]

Have you checked sized VS fired case dimensions? Sized loaded neck, sized shoulder and base VS fired?

I've seen this exact same thing in a 6BRA, turns out the loaded Peterson necks measured .2735 to .2745....about 90% in the .274-.2745 range....and the reamer was .275.

 

[Catalyst686]

Bolt out, depress ejector pin with something, like a pen or punch or whatever. Make sure it goes marginally under flush. If it doesn't,.. found your issue.

Remove ejector, clean the hole and pin. It can get gunk behind it. Rarely your ejector pin is too long.

Lastly, is the hole that the ejector is in, is it sharp ? It should have the smallest deburr. Otherwise it acts like a knife edge on the brass, cutting / shaving it. Thus, looks like pressure signs.

This is the conclusion we came to about a month ago, ejector must not be going subflush, turns out it was. Took the ejector out and examined it, everything was in spec and machined properly with no rough edges. Threw in a brand new bolt just for the hell of it just in case- same result.

 

[Anzac]

After the manufacturer returns your rifle advising all in spec/ gtg, I’d have x6 cases that you’d neck turned down by 4-5tho, starting H4350 load and see how you go.
Actually, even before neck turning you can do this now; have your GS mic the reamer neck and as per LR1845 mic a loaded round then compare. You may find your loaded round exceeds the neck.

 

[iceng]

Tight neck usually is stuff bolt close. The ejector pin hole OK? No sharp edges ? You did say it was replaced, but the actual hole ?

 

[Catalyst686]

Tight neck usually is stuff bolt close. The ejector pin hole OK? No sharp edges ? You did say it was replaced, but the actual hole ?

The actual hole was fine on the original bolt, the I used an entirely new bolt as well, ejector and hole were fine in it too.

 

[Catalyst686]

After the manufacturer returns your rifle advising all in spec/ gtg, I’d have x6 cases that you’d neck turned down by 4-5tho, starting H4350 load and see how you go.
Actually, even before neck turning you can do this now; have your GS mic the reamer neck and as per LR1845 mic a loaded round then compare. You may find your loaded round exceeds the neck.

This chamber was designed for no neck turning- https://blackjackbullets.com/product/25-creedkrud150fb291nck258fbdiam/?v=ed5e635ddcfb

 

[Anzac]

Notwithstanding, I’d still actually mic the reamer and compare to a loaded round. That will take all of ~60 seconds.
I just tube mic’d my Alpha 25CM= 0.029(0.0145x2) And then for Shits&Giggles my Peterson 6CM= 0.033(0.0165x2)!
Different lot, variances etc etc…. .?? Still, too tight for this little black duck. YMMV tho.
That’s all I got wrt a tight neck.
All the best finding a solution.

 

[4O6shootist]

I have cut 3 barrels with my KRUD reamer. 291nk diameter, my Peterson srp and necked down lapua is 286 loaded, perfect. Doesn't mean your lot of brass isn't fat necked.

 

[iceng]

I agree with @Anzac .. mic the loaded rounds, and get the reamer measured, or bore mic it at an engineering shop ?

 

[Seandradamus]

Try some different brands of brass Lapua and or Hornady, my bet is for 1 reason or another the Peterson doesn’t play well with your chamber, I had a similar experience with Peterson dasher brass, was extremely well made , consistent, shot great but had firm to heavy bolt lift on even the most mild loads , I even tried neck turning them down to lapua thickness with no improvement. Went back to lapua and no heavy bolt , even when pushing it 100 fps faster.

 

[Catalyst686]

Alright, wanted to give an update, the barreled action was probed inside and out, action and chamber are the exact dims they should be. I'm leaning heavy on the brass variable. I'm going to try to get 2 unused pieces of 25crm brass, not sure how likely that'll be but we'll see. I would just use the brass and ignore the ejector smear but in a mild load with heavy bolt lift it's just not going to happen. Thankfully I didn't end up with the 1k pieces that were originally ordered. Note- this brass was purchased at least 2 years ago.

 

[Catalyst686]

Try some different brands of brass Lapua and or Hornady, my bet is for 1 reason or another the Peterson doesn’t play well with your chamber, I had a similar experience with Peterson dasher brass, was extremely well made , consistent, shot great but had firm to heavy bolt lift on even the most mild loads , I even tried neck turning them down to lapua thickness with no improvement. Went back to lapua and no heavy bolt , even when pushing it 100 fps faster.

Yea it's likely the brass, not saying it's bad brass, just on the thicker side maybe, might try cutting a few coils off of the ejector spring, going to try to source a few rounds of new 25crdm pieces of brass first though to see what happens.

 

[iceng]

I wouldnt cut coils. Just change one thing at a time, not 2 or 5.

 

[4O6shootist]

I've ran a pile of Peterson 25cm srp brass through KRUD chambers, cci450 primers, 3 barrels using 135s and 131s from 2850-2930fps. A kreiger, hawkhill and a rock creek. Two were on an origin one a Tikka. In the beginning I bought 600pcs Peterson brass and I tossed it after around 7k rounds. I don't think this is a brass/chamber issue. I'm leaning towards the idea it's a tight bore or shallow grooves causing excessive pressure. Bolt slap on vrgin brass can cause ejector marks, but this is pretty heavy for that. Measure virgin case shoulder with you bump gauge and then measure a few fired cases with the primer removed. Excessive headspace growth is what causes bolt slap, there shouldn't be any more than 0.004" between virgin and fired, 005 MAX.

 

[mbeavers1]

Any chance there is any lube left on the cases after loading? If so, the neck wont seal right and this happens.