.308/7.62 barrel question...

[lead-1]

I have an Israeli Mauser with a new barrel that I slugged and have two slugs that both measure .307-.3075 diameter depending on which device I measure with.
My question is should I size down my boolits that are .310 as cast or will they be ok to shoot as is? If I should resize them is .308 ok or .309?

[Ben]

I believe if it were me , based on the info provided, I'd start at .309 ".
If your .310 bullets will chamber smoothly, there is no problem in shooting those " as cast".

Do you plan to prep your case mouths with a Lyman M die ?

Which .30 cal. cast bullet will you be shooting ?

Ben

[lead-1]

I have not used an "M" die and I will be using the LEE 309-160-R boolit with a gas check. I have had good luck with boolit in my Model 70 '06.
If I seat that boolit so the first lube groove from the base is just inside the case mouth the COL is 2.640(IIRC) and that will keep the gas check inside the case neck and it chambers fine.

[Ben]

I'd seat out as far as I could without hvy. resistance in the closing of the bolt. ( Minimum bullet jump )

[Dutch4122]

Measure the inside of a caseneck from a casing fired in your rifle. Then subtract .001" from that measurement. The result is the largest diameter that your rifle will chamber and fire safely.

Don't be surprised if that chamber/throat measurement is quite large. Military rifles are well known for that. I have a Spanish FR-8 Mauser with a .309" bore that can easily chamber & safely fire a .314" slug.

Hope this helps,

[lead-1]

If I understand correctly what you are saying I know I can chamber a round at .310 diameter for sure and roughly by memory 2.650" COL.
I wasn't sure about firing a .310 boolit into a .307 bore as being too quick a drop to be safe.

Now that I think about it that is only .001 more than my handgun boolits get sized from firing.

[Dutch4122]

If I understand correctly what you are saying I know I can chamber a round at .310 diameter for sure and roughly by memory 2.650" COL.
I wasn't sure about firing a .310 boolit into a .307 bore as being too quick a drop to be safe.


Yes, it is safe to fire a .310" boolit into a .307" bore. I have done that and even fatter more times than I can count. The boolit will just swage down as it enters the bore and provide a good seal. The example I used above in my 7.62 Nato Spanish FR-8 a boolit is going from .314" to .309" each time I pull the trigger. I have done this with loads generating pressures well above 40,000 cup and the only side affect I have found is excellant accuracy.

As I said, just measure the inside of a fired case from your rifle before it has been resized; then subtract .001" from that measurement and that is the diameter of the fattest slug you can safely shoot through that rifle.

Hope this helps, :mrgreen:

[madsenshooter]

I don't know what brand of case sizing die you're using, but unless you do one of two things, you'll be squeezing the base of the bullet down some when you seat it in the case, perhaps not enough to effect accuracy, then again, maybe. You can get an M die, or you can get an expander for the .303 British to use in your .308 die when you know you'll be loading the cases with cast. That's what I do with my Krag cases, saves the step of resizing the neck with the M die.

[Multigunner]

I have an Israeli Mauser with a new barrel that I slugged and have two slugs that both measure .307-.3075 diameter depending on which device I measure with.
My question is should I size down my boolits that are .310 as cast or will they be ok to shoot as is? If I should resize them is .308 ok or .309?
A hair tight but that may be a good thing , many 7.62 Match grade barrels measure the same.
This is especially handy if you run across some of the European NATO ball with undersized bullets. Could be thats why they made the barrel with such a tightbore.

Does this barrel have a freebore in the leade?