Gunsmithing Pressure problems with new barrel

[Rippe321]

My first post here. I have a new gun made for me and the barrel gives high pressure signs with ejektor marks on the brassbottom. This pressure comes after abot 30-40 shots after cleaning the barrel. I can shoot the same load and even factory ammunition without any problems and then suddenly a sticky bolt and the next shot will be with with extractor marks on the brassbottom. The handload are in the middle of min-max load an factory ammo is Norma. Would be very nice with some ideas what could be the problem. Cal 6xc.

/A

 

[Swampass]

From the sounds of it your chamber throat could be a lil to short. What could be happening is after x amount of rounds your throat gets a lil carbon embedded in it and basically makes it to tight. The bullet is potentially trying to get pushed out of the brass and start spinning in the rifling at the same time causing more chamber pressures thus giving you pressure signs. Just a lil ejector Mark is probably not anything to get overly excited about but I don’t know how much pressure signs your brass is showing

 

[Thud]

Sounds like you are suffering from a carbon ring problem. Research the symptoms and the cures. It really has little to do with a short chamber. It’s learning how to clean your rifle correctly

 

[Thud]

Forgot to ask. What round are you shooting.

 

[Terry Cross]

Forgot to ask. What round are you shooting.

He noted in the opening post that it is a 6XC.

Also noted that it is a new barrel. He doesn't list how many rounds down it or how he cleans but sounds too early for a carbon ring........


./

 

[Thud]

You be surprised how early the start. Need a little more info before final call.

 

[powdahound76]

Hahahaaa.

Im pretty sure @Terry Cross isnt surprised by much at all in the world of precision rifles.

I have no idea, tuned in to see what smart folks had to say.

 

[Thud]

I know of Terry’s great reputation. But more info will help

 

[Deleted member 10043]

They may have not set the headspace correctly. Had a 260 Ft. Bragg do that. The fucking thing closed on a field gauge. Nice shooting rifle though.

 

[Rippe321]

Thank you for your interest. A cleaning of my gun looks like this; Shooters choise as discribed on the bottle after that Sweets 7,62 as discribed on the bottle. I have done a serious brake in on the barrel. The hand loade is Norma brass, Murom KVB-7M, Norma 203B 35,8 gr, Hornady 105gr BTHP. Factory ammo is Norma FMJ 95gr. I have never had this kind off problem with any other barrel or cal. The precision is absolutely on top. Shoots very well. Bullets trough the barrel 176. Any moore info you like for a solution? Just ask.

 

[Thud]

Do you use patches or a brass brush.
and a larger brush in the throat area in a rotating motion. And then several dry patches to remove all solvent.
also how many rounds fired before you get the pressure signs.

 

[Rippe321]

I start with patches wet (3-4) and then a brass brush. I dont use a larger brush rotating in the throat area. Have never heard of that. Interesting. I allways use a lot of dry patches to remove all solvent. I use a boreguide and since it was removed i use dry patches to clean out all solvent from the chamber. Just to be sure that nothing other than nothing is in the chamber. About 40 rounds fired before i get high pressure. Everything feels great until this. Precision, how i handles, i mean everything. Shoots very nice groups.

 

[Thud]

I think you are you are getting a carbon ring developing and it come to a head at the point of 40 rounds
Check into what a overbore cartridge is your 6xc is one of them and they are prone to the ring.
You'll need to clean it more often then you do or modify your charge.

 

[Rippe321]

Ok.Thank you. I start with cleaning more often. How can i modifie my charge?

 

[Thud]

Try a different powder and bullet combo.
Theres more then one load for the 6xc
Try a slower powder, the norma203b is kind a fast.

 

[Rippe321]

Ok. Thank you. I will try that. Report results later.

 

[Greg Langelius *]

A tight neck and barrel heating? It this barrel chambered to a SAAMI Chamber Spec? You may need to try turning necks.

 

[Robert Gradous]

Take a fired case see if the bullet will drop back through the case neck before sizing,,, dont let the neck get bent during ejection,,,,, also check for a donut at neck shoulder junction.
Change brass manufacturers
Turn neck .0015
Open neck in chamber
Check for donut
Remove carbon
Use virgin brass when pressure shows up with resized brass,,,,, die problems.