How much can you size down?

[stubert]

Good day folks, I am looking at a new mold for my .375 H&H. It is advertised as dropping a .379 diam. bullet. I have not slugged the barrel yet,(am not where the rifle is now) My bullets are 12-14 bhn. How much can I go down if I have to? If they chamber at .379 could I use them as cast (they will be lubed) without damaging my rifle? Thanks, Stu

[jimb16]

Slug your barrel. Size to .002 over bore diameter. Chances are you won't need to size down more than .002. That should be no problem.

[ascast]

I think they will be OK as is. Sizing is a good way to check for oversized bullits which would cause over pressure, but the extra weight might still get you. But cast bullits are more forgiving than jacketed in that respect. I shoot a lot of 38-55 bullits in my 375 and found it will handle them all. 379 will probably chamber fine and shoot fine. Work up loads from the low side.

[Texas by God]

I size my Lee 379250F bullets to .377" as recommended by JES for my 38-55- they also work well in my brother's Ruger .375 H&H. With Unique and IMR 4198, they make the
.375 pleasant to shoot.

Sent from my SM-A716U using Tapatalk

[stubshaft]

You're assuming that the mold will cast .379" with your alloy. My Lyman casts at .378" and I size to .377" with a .375" bore.277373

[GregLaROCHE]

Casting temperature can vary boolit diameter too.

[JonB_in_Glencoe]

mystery mold and mystery rifle, it seems like you are putting the cart before the horse?
But, to answer your questions, you can size a 14 BHN boolit down .003 or .004 easily enough...and if your .379 "as cast" boolit chambers, it will not hurt your rifle.

With that said, I would slug the barrel and order the correct mold after you know the diameter. It seems that 375 H&H rifles can vary. My foreign made Interarms Mark X had a tight chamber/throat and a .375 dia groove barrel. I've heard others say their custom and/or commercial American made Rifles measure large, hence the availability of large size molds.

I sized my boolits to .375 to fit the tight chamber/throat (.376 was too tight for that rifle).

[stubert]

Rifle is a 2018 Win. model 70 Alaskan. The mold is an NOE .379-284 gr. GC. flat nose. The rifle is in New York, I am on Vacation in Florida.

[JonB_in_Glencoe]

I have numerous NOE molds and with my casting technique and my typical alloy, I have found NOE molds typically drop .001 larger than advertised. I would be expecting a .380" boolit from that mold. I can't help with info about your Win model 70.

[rockrat]

I shoot .379" thru my H&H with great results