primer do-nuts

[gcoulsey]

picked up my custom build yesterday (finally) and have just got home from the range, the gunsmith had already put 20 rounds thru the rifle helping break the barrel in, and i put a further 20 thru with normal cleaning procedure for break in..

i used some cheap (samson) isreali military rounds my gunshop gave me, but noticed on every round there was a huge do-nut ring around the pin-strike on the primer..??!!

ive never had this before on my other rifles, even when reaching max pressures, so i thought it may just be the rounds.

when i moved onto my ladder test rounds, EVERY primer has the same marking after firing.. on the start load, right up to my max load, and also on 2 sepererate ladders with different bullets.

the primers all look identical, no pressure signs between min or max, but EVERYTHING has a huge do-nut ring.

is this normal???

my 2 test ladders were 155 scenar 44grn to 46.7grn varget
and 168 smk 43grn to 46.8 grn varget.

rifle is a blue-printed remmy 700 action, 1-10 twist 26"custom barrel, AICS stock. (.308)

new lapua brass, cci br2 primers.

any ideas? should i be worried?

 

[BradfromND]

Re: primer do-nuts

My guess would be oversized firing pin hole in your bolt. You can get an oversized firing pin, or just shoot it.

 

[gcoulsey]

Re: primer do-nuts

if thats the cause, no harm done by just using it as it is then?
just makes pressure signs hard to spot..

 

[BradfromND]

Re: primer do-nuts

Post a pic up if you can. About half of my 700's leave a "do-nut" around the firing pin strike. I've never had it cause a primer burst.

 

[Victor N TN]

Re: primer do-nuts

I have a couple of rifles that do the same thing. A few years ago I had the same thing on one of my benchrest rifles. I had the firing pin hole bushed and redrilled. That took care of it. The bolt face on that particular rifle almost looked like it had bee gone over with a countersink the way the bolt face was chamfered in. But it was too irregular to have been done like that. One of the primer reasons for bolt face erosion around the firing pin hole is hot loads poping caps. When the primer blows or pierces, a stream of hot gasses will cut the same way a cutting torch does.

Make a habit of checking the bolt face and cleaning it. The only way you can tell if it's a fresh cut is if it's clean. You might want to discuss this matter with the person that built your rifle.

On the oversized firing pin. Personally, I prefer to bush the bolt and redrill to fit the original firing pin to still be used. But you might want the 'smith to polish the end of the firing pin. If it has been burned it will have rough spots on the nose.

Good luck.

 

[gcoulsey]

Re: primer do-nuts

hmm.. well the bolt face appears fine to the naked eye.. and brand new of course, but i will give him a call and see what he says.

in the mean time i will just keep on loading and testing for now.. keeping an eye on pressure signs.

its getting late here (in the UK) so i will try take some photos tomorrow of the primers.
im trying to get some more brass prepped before bed so i can charge them up for tomorrows shooting session!

 

[Grump]

Re: primer do-nuts

Remington bolts are notorious for sloppy firing pin holes.

One way I "calibrate" for safe "pressure signs" is to compare with factory loads using the same primer. Just make sure the reloads are not excessively resized, because those can give false high "signs".

Funny thing is, getting tolerance stack on a oversized hole and an undersized pin is the exact evil-opposite of making things with overly worn tools. According to some legends, BMW motorcyles used to match holes machined with <span style="font-weight: bold">new</span> tools (bigger hole) with shafts, pins, etc. made with <span style="font-weight: bold">older</span> tools (bigger piece), and vice-versa.

Maybe we need to send Remington a memo...?

 

[wfjames22]

Re: primer do-nuts

FWIW, the last three Remingtons I have bought (204, 223 and a 308) all do this. Its annoying!

 

[Bradley]

Re: primer do-nuts

http://www.snipershide.com/forum/ubbthre...127#Post1518127

You probably want have a problem with it shooting it like it is, but if it bothers you have it bushed and it will go away.

 

[gcoulsey]

Re: primer do-nuts

its not quite as bad as those pics, but thats what is happening.
no peircing though either luckily!

i started to get exctractor marks on the brass, so took that as my limit and backed off.. just ignoring the do-nuts for now, until i get a 'good-to-go' round developed and im settled in with the rifle, it can stay as it is.

thankyou for the peace of mind chaps!!

 

[sinister]

Re: primer do-nuts

You shouldn't have problems but were it my rifle I'd get the gunsmith to install a new bushing in the bolt face.

You are obviously a competent handloader. It will become annoying after a bit if you are trying to read pressure signs off your primers and case heads.

You shouldn't have problems with it where you shoot (assuming it's in cool Blighty). If you were to shoot somewhere hot in the summer like the American Southwest or North Africa I'd be concerned.