Bore sighting chromed barrel .308

[Marintime Mike]

Got a question concerning a new rifle I have ,,,chambered in 7.62 NATO which I just had a scope put on...
In order to bore sight it the fellow at the shop couldn't fit his normal 30 caliber bore sighting tool into the barrel....nor some laser gizmo sighting apparatus....
The guy asked if I was sure it was .308,,,and I told him it has 7.62 X 51 stamped on the barrel
He got the thing bore sighted using a device from bushnell that attached to the end of the barrel with a magnet...
This guy was not a real gunsmith,,,,but said he had never seen this happen before...
My question is...could this be related to the fact that the barrel is chrome lined ?
I have never fired the gun....but it accepts a .308 go guage....and will chamber .308 commercial ammo..
The Rifle in question is an Australian International Arms update of a Lee Enfield,,,with stronger action in 7.62x51 NATO.....Called an M10 B1 version...the sporterized type..
Any comments ?

 

[brian923]

well, i would not think that its chrome -ned. i may be wrong, but if its a sporterised rifle, i would say no. it could be chrome-moly steel? but that is different than chrome-lined. also, chrome-lined barrels are over-bored and over-chambered, and then built back to spec with the chrome lining, so the chamber should be exactly the same as any other .308. i would try to find a gunsmithe that could measure the chamber and tell you exactly what it is. just because it will chamber a .308 round and gage, it could be a 7.62x51 nato barrel re-chambered to a 30-06.


now, it could have been a mistake on behalf of the operator of the laser boresighter. the boresighter that i have has a laser, with pieces that screw onto it, witch match up to the chamber. if he accidentally grabbed the 30-06 boresighter, or any other size tool piece, that would have made the tool not chamber in the rifle.. make sence??

its better to be safe than sorry.

 

[rcmodel]

SO, are you asking if a .308" bore-sight muzzle-spud should fit in the barrel?
Yes it should.

Chrome lining should not reduce the bore diameter.
The barrel should have been bored & rifled oversize, to allow for the plating thickness bringing it back down to .308 again.

Only sure way to find out is to slug it with a lead bullet and measure it.


rcmodel

 

[JackOfAllTradesMasterAtNone]

Hey Brian923..

Take a look here: "chrome-lined free-floating barrel,"

http://www.marstar.ca/gf-AIA/M10-B1.shtm


I think it's time for a trip to a competent gunsmith for a bore sight job, and/or to slug the barrel and chamber to be sure of the caliber.

Brian posted:

just because it will chamber a .308 round and gage, it could be a 7.62x51 nato barrel re-chambered to a 30-06.

Uh.. That's still .308 at the muzzle. So that doesn't explain the non fitting muzzle spud.

-Steve

 

[Jim Watson]

Have you shot the rifle over iron sights to know that it works?

Barrel dimensions are not absolutely standardized. Their barrel subcontractor might have used Palma dimensions which are undersize versus commercial and military specifications.

 

[brian923]

does it look like this??

http://www.marstar.ca/gf-AIA/M10-B1.shtm

if so, i have to say... its a NICE rifle. and i take back my comment i said earlier, about the chrome lined barrel. thats cool. not many at all, ever install chrome lined barrels. i like them. i think that the accuracy issue is somewhat of a myth, but.... we wont go there.

if this is the rifle you have, i would say that the guy that was boresighting it was doing something wrong.

brian

 

[Marintime Mike]

Bore sighting...

Thnx guys..
Yes Brian....that is the rifle, and I have read reviews of people firing off .308 core loct by the hundreds without problem...
I haven't had a chance to take the thing out to a range ( few and far between around here ) but the chamber accepts .308 ammuntion with no scratching of the bullet at all....I can't imagine that the muzzel is smaller diameter then the chamber end...

 

[Bad Flynch]

This is something that one has to get familiar with when dealing with shootin' irons. The Europeans and the British sometimes have different ideas about what constitutes proper bore and groove dimensions than we do. It is not a big deal, because these dimensions are negotiable anyway.

What you have is a tight bore--for whatever reason. I have an old Sweeny Site-A-Line bore sighter and it is an excellent tool. However, it has ons-size bore spuds and I end up with many sizes for some calibers: 22s would be a good example of this, where .22 RF bores run several different sizes around the world and are all different from .22CF bores.

Another example is the bore for a .308 Win made for Palma-style shooting. The bores typically run 0.2980" and the grooves 0.3065-0.3075". Compare that to normal .308 bores of o.2995-0.3005" and grooves up to 0.3085".

Relax and get an adjustable bore spud.

 

[icebones]

dude a .308 winchester and a 7.62.51mm nato are two diffrent chamber dimensions, you can fire a .308 in a 7.62, but not vice versa, same case with .223 and 5.56mm,

also some european companies measure bore diffrent, US measures rifle bores from grove to grove, euro measure from land to land (of vice versa, im not shure which)

if your still unshure have a gunsmith in your area slug and make a cerro-safe cast of the chamber. you should be fine though.