Pressure unexplained at barrel break in.

[acssa]

I just finished a 6XC with a 13.5 twist barrel... I used 64.25gr Bergers with 35gr IMR4320, Norma Brass and jump used .04'

According to QL the pressure is +-33 000 psi.... but the case show ejector pin marks... usually seen with pressure.

Any guru's that can share experience on this please?

Thanks.

 

[SHootSTraight22]

I just finished a 6XC with a 13.5 twist barrel... I used 64.25gr Bergers with 35gr IMR4320, Norma Brass and jump used .04'

According to QL the pressure is +-33 000 psi.... but the case show ejector pin marks... usually seen with pressure.

Any guru's that can share experience on this please?

Thanks.

I noticed you have a smudge also.. Do your cases close up easily inside the chamber or do you have to apply pressure when closing the bolt? I also see your standard ejector mark that I get when approaching max pressure... I would just back down some if 3 out of 5 cases appear this way...

 

[acssa]

T

I noticed you have a smudge also.. Do your cases close up easily inside the chamber or do you have to apply pressure when closing the bolt? I also see your standard ejector mark that I get when approaching max pressure... I would just back down some if 3 out of 5 cases appear this way...

The bolt closed easy.

 

[Dusty Stevens]

Dont use ql. Work up loads using std safe practices. Ql has no idea if your powder is on the hot end and will fool you. Just cause it says its not hot trust your lying eyes when you see pressure

 

[aussiepowderburner]

FWIW out of about the last 10 barrels I have used in 3 different caliber,
I have had two which exhibit high pressure on a clean bore for the first shot!
And it decreases quite a lot on second shot and appears stabilised by approx 4th shot?
One barrel was so bad I had to load fouling shots with significantly reduced loads after cleaning.
Really did my head in on the initial breakin of one shot then clean for the first 3 shots?! After that process and moving onto multiple shots the decreasing pressure was noticed.
APB

 

[dkhunt14]

I never run a bullet down a dry bore. After the gun is clean and dry I dry my chamber, dry my bore guide on the outside. Reinstall bore guide, then I put 3 drops of Marvel mystery oil (dime sized spot) on a patch and push through the bore. It makes the first shot closer on impact and seems to help the barrel clean easier. Matt

 

[AckleymanII]

I fire formed the brass with a load of 14g of bullseye and cream of wheat, piece of paper towel, cases came out great.

Ok, you are finding out that Quick Load can not be trusted, File that fact along with the fact that there is no Easter Bunny.

 

[AckleymanII]

FWIW out of about the last 10 barrels I have used in 3 different caliber,
I have had two which exhibit high pressure on a clean bore for the first shot!
And it decreases quite a lot on second shot and appears stabilised by approx 4th shot?
One barrel was so bad I had to load fouling shots with significantly reduced loads after cleaning.
Really did my head in on the initial breakin of one shot then clean for the first 3 shots?! After that process and moving onto multiple shots the decreasing pressure was noticed.
APB

Was the primer strike off center very much on your fired cases? This could indicate a very crooked chamber that would leade to the bullet entering the bore crooked. I don' t know if this would leade to higher pressures, but your example is one of the strangest things I have ever heard of. What caliber are you seeing this in, and what is the barrel maker?

 

[Cold Bore]

I fire formed the brass with a load of 14g of bullseye and cream of wheat, piece of paper towel, cases came out great.

It sounds like you are referring back to something you posted earlier, but I'm not seeing another post by you further up in this thread. (?)

 

[acssa]

Was the primer strike off center very much on your fired cases? This could indicate a very crooked chamber that would leade to the bullet entering the bore crooked. I don' t know if this would leade to higher pressures, but your example is one of the strangest things I have ever heard of. What caliber are you seeing this in, and what is the barrel maker?

Its a 6XC with a 13.5 twist Krieger barrel.... action is a Rem 700.... reamer from PTG.... .269 neck .038 freebore. Neck clearance .002'

 

[dkhunt14]

Check to make sure your ejector pin can go below bolt face. Maybe some brass or dirt is holding it out slightly. Looks like the pin is only swiping half the diameter like it's crooked or has a rough spot. Was the brass on the first firing? Matt

 

[acssa]

Check to make sure your extractor pin can go below bolt face. Maybe some brass or dirt is holding it out slightly. Looks like the pin is only swiping half the diameter like it's crooked or has a rough spot. Was the brass on the first firing? Matt

Thanks Matt... I will check. Brass was fired twice before.

 

[Jeff Conover]

Few things may be your problem...neck clearance my not be enough...with 6MM Dasher we found .003 to .004 to be best...a carbon ring in the neck may be an issue for you also...Case neck length in the chamber should also be checked.

 

[AckleymanII]

Few things may be your problem...neck clearance my not be enough...with 6MM Dasher we found .003 to .004 to be best...a carbon ring in the neck may be an issue for you also...Case neck length in the chamber should also be checked.

Jeff, this is what I have been thinking, also! There is a mouse in the cookie jar, somewhere, cases too long, reamer ground with a slightly shorter neck, leade angle starting off right at the case mouth, too much jam on the bullet with a hot load? A case with a slight crimp caused by a long neck jamming into the throat would create a slight crimp.

 

[918v]

I like neck clearance for this.

 

[aussiepowderburner]

AckleymanII
The worst case in my example is a 6.5 x 284 on a Krieger 1/8 put together by a very competent gunsmith using a PT&G reamer and rougher.
On a clean barrel I have to load fouler rounds a full 2 gr down on my normal load.
The second barrel is a 308 - also a Krieger but nowhere near as severe.
However my cleaning regime with has shown it to be an individual also.
After a complete clean to bare metal to rid carbon it can take up to 12 rounds to stabilise in velocity and accuracy again,
As the round count has climbed ( approx 900 rounds down tube now) this has diminished to about 5/7 rounds now.

 

[SHootSTraight22]

I never run a bullet down a dry bore. After the gun is clean and dry I dry my chamber, dry my bore guide on the outside. Reinstall bore guide, then I put 3 drops of Marvel mystery oil (dime sized spot) on a patch and push through the bore. It makes the first shot closer on impact and seems to help the barrel clean easier. Matt

Have you ever tried a graphite or other dry lube suspended in alcohol as a carrier?? Been told it work great for first round hits..

 

[dkhunt14]

Have you ever tried a graphite or other dry lube suspended in alcohol as a carrier?? Been told it work great for first round hits..

No, but lots of other guys use lock ease. Matt

 

[acssa]

As Matt suggested, I did some work on the pin and fired some of the same load... perfect!

 

[1shot]

I never run a bullet down a dry bore. After the gun is clean and dry I dry my chamber, dry my bore guide on the outside. Reinstall bore guide, then I put 3 drops of Marvel mystery oil (dime sized spot) on a patch and push through the bore. It makes the first shot closer on impact and seems to help the barrel clean easier. Matt

I do the same thing, but using colloidal graphite. A little goes a long way.
Lloyd