maddening 6br issues

[mattlewis]

i apparently have the only misbehaving 6br in the world!

trued rem 700, no turn 6br throated for 105's, all work done by PTG (*edit - Pacnor) bought the rifle with ~650 rounds fired in it. previous owner provided load data, 30.1 varget, wolf SMR, 108 berger jumped .015".

i receive rifle, and proceed to shoot about 100 various loads and seating depths, all with 105VLD, varget/RL15 and CCI450's, all out of lapua brass. find sticky bolt and other pressure signs around 31.7-32 grains varget jammed .010. back off, shoot several .3's and .4's as i test seating depths, etc.

all of a sudden, i get blown primers all the way down to 29.2 with bullet touching lands. i mean seriously cratered primers.

rcbs hand primer, redding micro seater, harrels custom sizer, weigh every charge on rcbs beam scales to the grain. measure to lands with hornady tool, i use mics, double check everything. same lot of varget, same brick of primers.

what can cause something like this? what can i look for? i'm seriously scratching my head and pulling out what few hairs i have left. i'm not really getting sticky bolt, just cratered primers. can primer seating depth cause something like this? chrono read 2789 today on the 29.2 load, which is slower than a bunch of loads i shot previously.

 

[mattlewis]

wonder if i can seafoam it like my outboard engines? ;D

thanks, i'll look into that possibility.

 

[bozo699]

A "carbon ring" can cause exactly what you are describing...

Donovan, these wre my exact thoughts even before I saw your reply, most likely the culprit. Scrub with a quality brush, don't drag back through the end of your muzzle nor at the throat either.
Wayne.

 

[Erik Cortina]

Check brass length and trim if necessary.

 

[WyleWD]

By blown primers, do you mean they have been pierced? If so the bolt should be taken apart and cleaned. If the firing pin hasn't been worked over this might be a time to consider that as well. Some 700's crater primers straight from the factory and always have. you may want to consider this after taking the advice of the previous posters. WD

 

[fdshuster]

mattlewis: Tried the "Seafoam" for carbon removal, as seen with my Hawkeye Borescope, in the grooves and on top of the lands, in both Krieger & Bartlein barrels.

It did nothing to remove carbon. JB Borepaste remains my choice to remove carbon fouling.

 

[fayettefatts]

My only comment is that I'm surprised you didn't find pressure signs before 31.7-32 gr. of Varget!

 

[jrm850]

If you are shooting unturned Blue Box in one of the popular .2704" PTG chambers you probably only have about .0015" total neck clearance. You may need to turn some necks after several firings.

 

[Nodak7mm]

My only comment is that I'm surprised you didn't find pressure signs before 31.7-32 gr. of Varget!

Agreed, this would be pretty dang warm in either of my 6BRs. On the same matter, Donavan's guidance is always of great value!!!!

Rod

 

[mattlewis]

Thanks very much for all the replies. It gives me somewhere to go when I was just about out of ideas.

I have trimmed length , but just short enough to cut them all square. Is there a standard length neck I should aspire to?

I have not turned necks, but will have the ability to this week.

 

[Erik Cortina]

Look for a 6BR diagram, it will give you case length and trim to length.

By trimming necks I assume you mean turn necks?

Do you know what size chamber neck you have?

 

[Multitoes]

I always check my fired brass by seeing if a bullet will slip in freely ; this also shows donuts...
Shilen told me all their 6BR reamers are 1.570 neck length.

 

[lrgoodger]

Agree with those saying your load is too hot. I have one Savage 6BR that blows primers under 31.0 grains. I run 31.0 in a couple of customs, but they are about the max.

 

[lrgoodger]

Also, as someone else said, the rem 700 is designed to crater primers, so I wouldn't worry to much about the cratering. I had that on my 700 and researched it until I found the article from Rem personnel that discussed why they did that. Can't remember where it is now. As long as they are not pierced (which will erode the tip of your firing pin, sharpen it and cause it to pierce even more readily), you should be OK.

 

[mattlewis]

Look for a 6BR diagram, it will give you case length and trim to length.

By trimming necks I assume you mean turn necks?

Do you know what size chamber neck you have?

oops, it was late and i had worked a long shift! yes, i have trimmed to length, but not turned necks yet.

i do not know, but i should be able to measure fired brass, right? all i know is it's a no-turn neck in a PTG chamber, but i can measure tonight.

 

[mattlewis]

By blown primers, do you mean they have been pierced? If so the bolt should be taken apart and cleaned. If the firing pin hasn't been worked over this might be a time to consider that as well. Some 700's crater primers straight from the factory and always have. you may want to consider this after taking the advice of the previous posters. WD

certainly most of them have been dimpled. but some have been completely pierced. i will disassemble the bolt and clean the pin, as it probably needs done even if that isn't the culprit.

thanks!

 

[mattlewis]

If you are shooting unturned Blue Box in one of the popular .2704" PTG chambers you probably only have about .0015" total neck clearance. You may need to turn some necks after several firings.

this is in fact the case, except for the most recent 29.2 attempt, which was in virgin blue box.

 

[Ackman]

i apparently have the only misbehaving 6br in the world!

trued rem 700, no turn 6br throated for 105's, all work done by PTG.

PTG makes reamers, they don't build guns. And the chamber....again they make reamers, to the customer spec's.

 

[mattlewis]

i apparently have the only misbehaving 6br in the world!

trued rem 700, no turn 6br throated for 105's, all work done by PTG.

PTG makes reamers, they don't build guns. And the chamber....again they make reamers, to the customer spec's.

sorry, Pacnor did the smithing. do you have any suggestions you'd like to add?

 

[lrgoodger]

While you have the bolt apart, inspect the tip of the firing pin with a strong magnifier. If it's not smooth and round (within reason) you may need to replace it. If it has any sharp edges at all on it, it will just aggravate further piercing.