What sizer die to start with?

[Muddydogs]

Slugged my Win 94 30/30 this morning. Slug measured .308 to .3085 and it got easy to push a couple inches before the forcing cone for an inch or so then went back to tight. Should I start out with a .310 sizer die or maybe a .311?

Looking at the LEE 309 170 FN mold.

[HangFireW8]

Slug the throat and size to at least that.

[Firebricker]

I would go with the .310 that's one and a half to two thousands over I can't see going any more helping. FB

[Idz]

In their catalog the Lee mold C309-170-F is a gas check design which casts at 0.309 inch with a typical Lyman#2 alloy. I don't see a 309-170-FN listed, sure you got the number right?. If you size to .310 to crimp on the check the bullet is untouched and the check is .310 inch. You should do a fit check to make sure it chambers before you go into production.

[Muddydogs]

In their catalog the Lee mold C309-170-F is a gas check design which casts at 0.309 inch with a typical Lyman#2 alloy. I don't see a 309-170-FN listed, sure you got the number right?. If you size to .310 to crimp on the check the bullet is untouched and the check is .310 inch. You should do a fit check to make sure it chambers before you go into production.

Yes its the C309 170 F. From most reports the mold throws big like most Lee molds do. Guys on the forum routinely size this bullet from .311 down to .308. Some shoot it unsized in the 303 British and the 7.7 Jap.

[Idz]

My C309-170-F mold runs about 0.307-0.308 with soft (BHN 8) range scrap lead so it should be pretty close with the right alloy. The gas check should be doing most of your bore sealing so I'd think that is the important diameter.

[1Shirt]

My rule of thumb when starting with a new blt has been to go with the lyman recommendation. Load and shoot 3-5, if no leading and reasonable accuracy you are probably good. If leading w/without accuracy go up a thousands and try there. May be necessary to go even larger but it is a trial and error process. This works for me.
1Shirt!

[leadman]

The .310" should work fine for you. Like as was mentioned the throat is a critical area to fill. Try a slug from the breech end if you can or maybe seat a .310" boolit backwards long and insert it in the chamber and try to close the action. This will give you some hint as to the size and length of the throat.

[FAsmus]

Muddy;

Whenever possible avoid sizing ~ cast a bullet the right size in the first place.

For your 0.3085 +/- grove size seek a bullet of at least 0.310 and use a 0.311 die to seat the GC.

Good afternoon,
Forrest

[Larry Gibson]

Either .310 or .311 will work fine. I use .311 as my "go to" sizing for all .30 cals of .308 - .3095 groove diameter. The .311 sizer has worked great in numerous M94 30-30s I've had over the years including the 2 I have now. The .311 sizing also works extremely well in my Contender carbine barrel. Considerable testing as shown that .310 and .311 sizings in .30 cals give the best accuracy generally.

Larry Gibson

[1Shirt]

As usual agree with Larry!
1Shirt!

[ShooterAZ]

I have that mold too, and I size & seat gas checks to .311. The sizer is barely making a mark on the boolit, but the check is nice and tight. I'm using a blend of Canuaba Red and BAC for lubing it.