Bullet size for 375 winchester?

[andym79]

Hi guys I recently got a 375 Winchester. This weekend I cast some bullets and then slug my barrel.

The mould drops the bullet at .379", the barrel slugs at .376". The alloy I am casting has a BHN of about 12, its 4/2/94!

Should I shot it sized to .377", .378" or unsized at .379"?

[Tatume]

the barrel slugs at 0.376" ... Should I shoot it sized to 0.377", 0.378" or unsized at 0.379"?

Yes. Any of those dimensions will work just fine.

[andym79]

If .379" will be fine, I might just leave it at that! I just wondered it I needed to cast a softer alloy to go .003 over?

But then I shoot a lot harder than that in the 6.5x55 at .002" over, so I guess its all relative as a percentage.

[Elkins45]

Do you already own sizer dies in those diameters? I would start with the sizes I already have and see how they fly.

[BABore]

Measure the inside diameter of a fired case with the crimp reminants removed. This should be done on a new or once fired case using a full powered load. Your maximum, safe boolit diameter will be 0.0005 to 0.0010 inches smaller than your measurement. That is what the chamber will allow without the potential of spiking pressure. Assuming this is over barrel groove diameter, you can use any size boolit between groove and this derived dimension. Which might be the best diameter will be based on alloy, velocity, powder, and a bunch of other variables that only you and your gun can determine. You need to do the work.

[andym79]

Do you already own sizer dies in those diameters? I would start with the sizes I already have and see how they fly.


I haven't yet bought any of those sizing dies! Thats why I was wondering if I could get away with unsized bullet at .379"

[MT Chambers]

You'll prolly be alright if the loaded round will chamber.

[andym79]

Well I think I better see if Buckshot can make me up a 377 Lee style sizing die!

The unsized 379 bullets are bulging the case, they do chamber. This was with a 4.5/2.5/93 mix; so after work today I casted 100 in my real soft alloy 3.5/96.5 alloy. They seat much better, so till I get an appropriate sizing die its 25:1 for me.

[Tatume]

Andy, instead of making custom sizing dies, get a Lyman M die. Your problem is not that the bullets are too big, they are not. Your problem is that your FL case sizing die is too small. The neck expander ball is dimensioned for jacketed bullets, not cast.

[andym79]

Andy, instead of making custom sizing dies, get a Lyman M die. Your problem is not that the bullets are too big, they are not. Your problem is that your FL case sizing die is too small. The neck expander ball is dimensioned for jacketed bullets, not cast.

Your probably on to something there! I use the Lyman M for my 6.5x55 and 30-30, because the Lee powder through die was not part of the set with them. It was with the 375 Winchester, but it flares rather than expanding the neck. Perhaps I shouldn't have tried to hang the expense of that die for my 375?

[Nrut]

For best results follow the instructions in post #5 and buy a custom expander and push thru sizer based on what you find..
That would be the shortest route to get to where you what to go!
Your choice..
Do it right the first time or fart in the wind..

[badgeredd]

Another vote for post #5.

Edd

[andym79]

Well they shoot fine unsized through my big bore at .379" using a nice soft alloy. I will be sizing them to .377 once I get my die from Buckshot.

[runfiverun]

I wouldn't change the diameter.
I use .379 in both my win-94 and in my marlin 375, they both like that size.