6BRA Heavy bolt lift

[6MMsteve]

My last step after lubing the barrel a smidge is to use patches, paper towel, with a dab of alcohol and clean the chamber 3x because I forget the other 2x, anybody else forget the chamber clean or just me

 

[tillroot1]

Have you lubed the lugs and primary extraction? a bit of GOOD grease may help if not.

 

[6MMsteve]

I clean my cases with Acetone with a fan blowing over my shoulder... squeaky clean

 

[Drewel]

Now these guys are extremely intelligent, and they bring some very good points. And all these mistakes I have made myself. But when you say bolt lift….. are you a Primers flat? Are you showing signs of pressure? Don’t be confused with trigger reset…. Which is another problem….

 

[G Liles]

Have you seen the video of Speedy cleaning where he shows to put something like a big shotgun patch over a brush to dry out the chamber as last step?
I put the patch over a bore mop.

Same here, I use a 3 inch shotgun patch over a bore mop.

 

[Clancy]

Same here, I use a 3 inch shotgun patch over a bore mop.

Me too, those shotgun patches are cheap and work well. I may even use a little brake cleaner on them now and then.

I had a friend once (and he’s probably going to read this) that would get ejector marks after a couple of rounds. Never on the first two or three. It took me about a week to figure out that he had residual imperial wax in the chamber and when he fired the gun, the barrel would rise above the ambient (and cold) temps and allow the imperial to act as a lubricant.

A little brake cleaner and some coaching on how to wipe down cases and we were good to go.

 

[Walt Schmidlin]

What is the OD of the neck of your fired brass versus the OD of the neck of a loaded round?

 

[Kracken McGraw]

I’m curious to how this turns out. Does it usually take a die change to cure this?

 

[SKWERLZ]

so is this a tight bolt handle all the way up or just at the top during primary extraction?

 

[Rehner23]

so is this a tight bolt handle all the way up or just at the top during primary extraction?

All the way up

 

[Rehner23]

What is the OD of the neck of your fired brass versus the OD of the neck of a loaded round?

What is the OD of the neck of your fired brass versus the OD of the neck of a loaded round?

I’m not sure, I will check and post back when I load my next batch. Hopefully this week and I can try some of these suggestions next week at the range

 

[mikecr]

You could remove the firing pin spring and see how the bolt turns on offending cases.
It's a good way of sneaking into clear headspace measure. Maybe see an issue otherwise.

 

[lawrence97]

Hello everyone, I’ve done a lot of reading on this forum, but this is my first post.
I recently had a 6 BRA built with an Impact precision action and Krieger barrel.
The gun shoots great so far, but I’m getting a pretty heavy bolt lift, even with loads that would be considered light… I’ve been ladder testing loads between 29.6 - 30.5 H4895, which is giving me muzzle velocities from 2760-2880 with a 105 Berger hybrid. The bolt lift always seems to be heavy, maybe a little more with the hotter loads but not significantly.
I’m shootings Lapua brass, which I did fire form, but I really didn’t pay too much attention to the bolt lift when fire forming.
At the moment I don’t know the reamer spec that was used to chamber the barrel.
Other than the bolt lift there doesn’t look to be any other signs of over pressure.
Any suggestions for me!??
Thanks!

You are using good components and when I initially read your post I immediately thought you were using Alpha brass since it tends to show heavy bolt lift prematurely.

I would focus more on accuracy. If you have heavy bolt lift bring the charge down until it is to your liking without sacrificing accuracy. You need to understand that some actions tolerate pressure less than others or may show it sooner than others.

If you are chasing velocity, you started off wrong by going with a 27” barrel. Based on your action and barrel length choice I’d assume you wanted a lighter setup or you shoot PRS where a 30”-32” barrel is not feasible.
The other variable that could show pressure signs prematurely is your bore diameter. Krieger offers a .236 and a .237. I have used both bore sizes and the .236 always seem to hit pressure sooner and velocity with less powder than the .237’s.
If the barrel is brand new, it may take up to 200rds before it speeds up so you must take that into consideration.

As for comparing your loads and speeds to what others have posted with their BRA’s, use it as a guide. Most of my BRA’s with 30”-32” barrels have shot best around 2900-2930 fps. Remember that the BRA isn’t much more capacity than the 6BR. To hit the higher nodes I think the Dasher offers the better case capacity and safety net to prevent high pressure.

With H4895 in my longer barrels I tested up to 30.3gns. Most settled between 28.6 - 29.6.

If you have Varget I would try it.

 

[linedrive301ft]

Check your 200 line. 1/1.5 thou can make a difference on hard bolt lift. How many firings on your brass?

 

[DaveTooley]

How much effort is required to close the bolt? Is the bolt closing freely? As in close with no effort required.

 

[gunsandgunsmithing]

My first guess is the die isn't sizing the bottom portion of the brass enough or possibly at all. If so, a different die will help or, there's not a thing wrong with having the chamber polished out a few tenths either.

 

[Rehner23]

How much effort is required to close the bolt? Is the bolt closing freely? As in close with no effort required.

Not hard to close, nothing more noticeable than my other rifles.

 

[Rehner23]

My first guess is the die isn't sizing the bottom portion of the brass enough or possibly at all. If so, a different die will help or, there's not a thing wrong with having the chamber polished out a few tenths either.

I guess that is possible, I’m using an LE Wilson 6BRA die, I haven’t heard too many bad things about Wilson dies..

 

[SKWERLZ]

I guess that is possible, I’m using an LE Wilson 6BRA die, I haven’t heard too many bad things about Wilson dies..

I use that same die with a chamber cut with a standard PTG 6BRA and Peterson brass with no issues

 

[DaveTooley]

I guess that is possible, I’m using an LE Wilson 6BRA die, I haven’t heard too many bad things about Wilson dies..

How many firings on the brass? Like Mike I'm leaning towards a clearance issue somewhere. There has to be room for brass to expand enough and then snap back. That can be at the base as well as the shoulder bump. Getting brass into the chamber is one thing but it doesn't always mean that all is good after firing.