6BR Pressure Found Low Charge

[Dolomite]

I was looking at that spot and thinking the same thing. I’m not sure if it was like that or not. It’s an Impact Precision 737 that I just got back from Speedy blueprinting.

Ask Speedy and see what he says, he may be able to diagnose the issue better than us suggesting different possible solutions. That barrel sure is clean and no carbon ring.

PS try firing one round with 29 grains without the suppressor and see what happens.

​

 

[MikeG08]

Have you used go/no go gauges on the chamber???? Those faint marks at the .200 line could be the start of case separation??? Are you having any issues with primer strikes??? What does your shoulder bump gauge show on fired brass for spec versus virgin brass??? Can you check the concentric measurement of the brass at the rear of the case versus virgin brass all the way to the .200 line??? Just to make sure your smith cut your chamber concentric?? Your primers don't show to be pressured and there's not that much of a carbon ring in that barrel to cause a hard bolt lift like you describe. Loaded round is .268 and fired round is .271 so you should be ok on neck clearance. Sized rounds load with no resistance??
stan

No issues with primer strikes, I am not sure on the 200 line this brass has 2 firings on it. I see it on a lot of the brass though. I will have to look closer at some of the other brass put through that rifle. The comparator/bump gauge leaves marks on virgin brass also. I threw a picture up. I am scratching my head. I have a couple barrels on order now. I may just put a pin in this until new barrels come in and run those to see what happens. That way I am not potentially wasting brass.

 

[DanSavage]

.268 nk 68 grain bt. Old brass still showing sine wave.

I’ve tried to achieve sign waves over many cartridges with no success,, only factory ammo will produce a sign wave in my experience,,, what gives, I’ve tried everything from more clearance, more tension, less tension and less clearance lol

 

[Larry Koch]

I’ve tried to achieve sign waves over many cartridges with no success,, only factory ammo will produce a sign wave in my experience,,, what gives, I’ve tried everything from more clearance, more tension, less tension and less clearance lol

The only rifle calibers I shoot- 30BR, 30 major, 6mm ppc, and 6br. all show a sine wave. Now early on I had difficulties in getting there. You need a clean neck, a proper neck chamber fit, and your good to go. If the brass neck is harden annealing will help.

 

[JFrank]

I’ve tried to achieve sign waves over many cartridges with no success,, only factory ammo will produce a sign wave in my experience,,, what gives, I’ve tried everything from more clearance, more tension, less tension and less clearance lol

I always get sine wave type powder residue on my reloads.

 

[Larry Koch]

I always get sine wave type powder residue on my reloads.

That’s it.

 

[MikeG08]

I took the barrel off and put another project I was having trouble with back on. I had a 308 barrel that was very inconsistent. Long story short the dowel pin was dragging in the shroud. That action is off to Speedy and I am putting that barrel on this one and restarting that project. If I have trouble with the barrel I get back from speedy I think the trigger puller may be the issue.. .. I will come back and update this thread once I have my new barrel and do some load develop.

 

[Schippergreg]

I didn’t go back through all of the posts so sorry if this has been answered but explain your heavy bolt lift. Is it hard to raise the bolt or hard to pull the bolt back? If you have to snap the bolt open I would guess that your die doesn’t match the chamber and it’s hanging up at the base.

 

[MikeG08]

I didn’t go back through all of the posts so sorry if this has been answered but explain your heavy bolt lift. Is it hard to raise the bolt or hard to pull the bolt back? If you have to snap the bolt open I would guess that your die doesn’t match the chamber and it’s hanging up at the base.

It does it on virgin brass. On my fired brass I use a Cortina Mandrel which squeezes the base.
It’s a heavy lift up on the handle.

 

[gunsandgunsmithing]

It does it on virgin brass. On my fired brass I use a Cortina Mandrel which squeezes the base.
It’s a heavy lift up on the handle.

Are you familiar with bolt click and how it happens, etc? Is it that or is bolt lift heavy all the way through the lift?

 

[Schippergreg]

Sounds like a clicker to me. Strange that it’s happening with virgin brass.

 

[gunsandgunsmithing]

Sounds like a clicker to me. Strange that it’s happening with virgin brass.

Yes, really strange. There use to be some very tight 6BR reamers and ppc reamers. That would do it but most moved away from spec'ing around virgin brass a long time ago. Too tight is no good.