new barrel

[kenbrofox]

Hi, I'm in need of good advise. Had my rem M7in 22/250 pacnored to 243,got it back a few weeks ago and fired the only 3 rounds i had, just to start barrel break in. Got some Privi (cheap) Partisan ammo yesterday and went up the field this morning. A bit stiff to get the bolt handle down on the first shot and by the seventh it was really hard, didn't fire that one,and it was really hard to open the bolt to get the live round out. No pressure signs but there is a faint bright mark the thickness of a scratch all the way round the case almost at the top of the shoulder, just before the neck starts.All comments greatly appreciated. Regards,ken. PS.Pac-Nor didn't do the work,only supplied the blank.

[jo191145]

Sounds like your smith headspaced it a little short.
Could be the cheap ammo is headspaced long.
Its not a tightneck chamber is it? Try slipping a bullet in the fired brass.
Its possible the cheap ammo has a radius at the neck shoulder junction instead of a sharp angle. Couple that with a SAAMI minimum neck and headspace and you might give you an interference fit.

Do you have any other ammo/unfired brass to try? That should be your first step.

FWIW If you plan on handloading for this tube I personally prefer a short headspace as oppossed to long.
Might need to modify a shellholder to get a FL die to work but it cuts down on the initial fireform stretch the brass undergoes.

[kenbrofox]

jo,
I forgot to state that the 'smith said it was a custom chamber, but that was all he said. I've just measured a loaded privi round and a loaded federal,as near as i can tell the federal case is .006 shorter than the privi one.The bolt will close easily on the feds. Thanks,ken.

[stevecrea]

I am no expert on this subject, but a "custom chamber" means that the tolerances are tighter, which means that ammo which is a tad long will be up against the chamber tight when you close the bolt.

I prefer a reasonable amount of resistance when I close my actions. And, when I have fireformed cases that are only neck-sized, then they are usually snug. I like this, as long as it is not too snug.

[kenbrofox]

Hi, I,ll just bin the Privi ammo and not buy any more of that make. It cost me £36 for 60 rounds of privi and £36 for 20 rounds of Federal. pound foolish, penny wise or what? Thanks for replies.ken.

[stevecrea]

Ken:

The snugness aids in consistency and accuracy, because the cartridge is being aligned more precisely in the chamber. But again, not overly tight. If you have to really crank on the bolt, then that is probably resulting in more wear on your action, chamber, etc., than is desired.

It is a bit like girls. Is there such a thing as "too tight"? Sometimes, but too loose is the more common problem, with girls and chambers.

[kenbrofox]

jo, i tried pushing the bullet of a live round into a fired case point first, it wouldn't go in past the ogive, very tight. Anyway, as the Federal ammo chambers easily i don't have a problem anymore. Thanks.
steve, all the girls i know were built to sammi spec, unless there was an under size round in there somewhere. Thanks,ken.

[jo191145]

Ken

If the bullet will not slip fit into fired brass you have a tightnecked chamber. You need to be turning necks for this type of chamber.

If your live round has the same diameter as the chamber neck the brass cannot expand and release the bullet,,,,,,,,correctly....

Basically if it chambers without resistance it will release the bullet and not blow up the gun. Accuracy will suck though.
You should have at least .002" clearance between brass and chamber in the neck area. OLD benchrest guns went tighter than that spec.
Over the years folks learned there was no degradation in accuracy if they used .002"-.003" clearance. Actually they found aggs improved with clearance. They no longer needed to measure case wall thickness down to .0001" on every piece of brass like their life depended on it.

You know what happens if the brass cannot stretch and release the bullet right

Measure your loaded Federal ammo's overall neck thickness and measure the Privi too. My bet is the Fed is just a hair smaller in diameter.

No matter what you do do this. Contact your smith and demand the neck dimensions on his custom reamer.
Over here in the states (I think) its the law that any barrel with a smaller than Sammi neck must have that dimension stamped on the barrel.
It can be on the barrel stub but it must be there somewhere.
Seems to me you have a neck tighter than Sammi specs. You need to know this dimension. Very important for the sake of life and limb.
Tight headspace is nothing of consequence, it can be worked around. Tight necks can hurt you. Both rifle chambers and girls included.

[kenbrofox]

jo, smith says the reamer measures .27815, my unfired necks measure .2715, thats both Privi and Federal. That looks like .00665 of clearance.I'm thinking it must be the extra 6 thou length of the Privi cases thats causing the problem. Would you agree? thanks for your help.ken.

[jo191145]

Ken

I quess your right then. The ring you described suggests a simple headspace discrepency.
Odd that a bullet will not slide into a fired case with that much clearence.
Either extraction dent on the case mouth or its just not expanding when fired.
Brass can get hard enough to not expand the case necks. The lighter the bullet the more pronounced this problem can be.
I just witnessed this AGAIN myself in a 243 pushing 58 V-Max.
Very odd that factory ammo would do this tho. Brass should be soft from the factory.

Try some of the Federal.
Keep a eye on neck dimensions after firing. Should be around .277-.276. Bullet should fit easy in the fired case.
If the Feds expand then its just some bad Privi brass.
If the Feds don't expand I'd ask your smith for more help.

[kenbrofox]

jo, thanks again,will post if anything unusual happens. ken.