ZERO Freebore

[johned]

I have a 16 inch 7.62 X 39 chambered barrel on my Savage Striker. I bought it long ago and I cannot remember the details or the mfr. I am pretty sure it was a Savage take -off. It has been fired by the previous owner enough to foul the barrel pretty good as I just noticed. The bore is 308 as slugged. My problem is that the bullet gets rifling engraved for maybe 1/16 inch with the Russian surplus ammo and a little less with the PMC. "into the rifling" was always a BAD thing in my reloading "classes". My CZ 58 doesn't groove these bullets. The rifling doesn't look to have and taper as the bullet has copper piled up as though it was being "cut" rifled as oppesed to "button" rifled. I not in the SAMMI drawing that a 223 has a closely specec chamber with a specified angle for the free bore where the lands are tapered. The neck for the 223 is also different.

Am I doomed to sending this barrel out to have a chamber reamer re-seated? Should I be concerned about what else might be wrong with the chamber? Were I to rent a reamer and have my limited skills Smith chuck it up and run the reamer in a slight "tad" at a time till I get zero contact? I could do that with a bullet in hand and run the bore in till I get zero and then have the perfect chamber for setting the bullets back precisely to achieve whatever number of thousandths I chose to the set back that performs the best. Asside from this being a NO TURN NECK reamer is there any other consideratuion on which reamer to use?

This isn't a bench barrel but I want to give it every cost effective chance to perform at its max potential. I am thinking about casting the chamber to see if there are any other anomalies to the chamber I might need to correct while I have the reamer in hand if I decide to go that way.

Thoughts? Please,

John

 

[troy fairweather]

i would just rent a reamer and cut by hand, for best accuracy with the x39 a cmp chamber maybe better. at worst have the shank cut thread and rechamber it. have you shot it at all, i would give it a good cleaning.

 

[edwardware]

I have answered similar questions by making a pound-cast of the chamber; you can also use a chamber casting alloy. Short of a borescope, that's how to see what's up.

From your description, it sounds like Savage missed cutting the throat (freebore) and lead (tapered transition from no-rifling to rifling).

I would buy a reamer; your tool acquisition habits may vary.

 

[someguy2800]

I have use 4d reamer rentals to do this sort of thing in the past. Good service. Reaming a throat is quite easy and simple to do by hand

https://4drentals.com/product/30-cal-308-precision-throater/

 

[shooter1niner]

as others have said, do a cast of the chamber and see what you actually have.

 

[Reloadron]

Do a cast and see what you have. If it concerns you. Personally if the rifle were mine I would run a 7.62 X 39 headspace gauge in the chamber, if the bolt closes I see no reason to ream anything. If the lead bothers you then you use a throater reamer and not a chamber reamer. The throat is the groove diameter of the barrel less the rifling or the freebore.Actually SAAMI defines it as:

FREE BORE
A portion of the chamber, usually cylindrical, forward of the casemouth of a diameter larger than the projectile in which rifling is not present. See Bullet Jump. See Throat.

To increase the freebore in your case since you slugged the barrel as a .308 I would think what you want is a hand throater reamer and not a chamber reamer. It is easily done by hand but you just take a little at a time hand turning the tool using a good tap oil.

Ron

 

[Riomouse911]

You can use Cerrosafe to cast the chamber/throat area to show you exactly what you’re dealing with inside the chamber.

It’s sold by Brownells and others, and is a piece of cake to use.

Stay safe.