Sizing for gas check?

[SCHUETZENBOOMER]

Looking for input on boolit size. Is it still accepted practice to size cast boolits .001” over groove even when gas checking? Boolit in question is the RCBS 257-120. I need to make a special throating reamer to accommodate the oversize bore-riding nose….my mold casts the bore ride section at .253”. I am OK with this as I want to experiment with “freebore” a bit anyway to get this bullet seated out enough in a 250Sav AI to keep the GC in the neck.

[.22-10-45]

In my Hornet, and .222 Rem...both .224 groove, I size .226" The g.c. even when annealed always seems to spring back .0005" or so over sizer dia.

[Mk42gunner]

My Husqvarna Model 26 in .25-20 slugged at .257" I size the gas checked Lyman 257420 to .258" with no problems. For my nominal .30 caliber rifles, which should have a .308" bore; my first choice of sizing diameter is .311", and I have never had to go down in size.

I am starting to believe it is more important to fit the throat than the bore.

Robert

[Screwbolts]

size your boolitz to the largest size that will alow the round to be reliably chambered. The barrel is a perfect sizing die.

[Iowa Fox]

size your boolitz to the largest size that will alow the round to be reliably chambered. The barrel is a perfect sizing die.

This gives me the best results, Thanks to Buckshot for making the dies to let us do this.

[JonB_in_Glencoe]

Looking for input on boolit size. Is it still accepted practice to size cast boolits .001” over groove even when gas checking? Boolit in question is the RCBS 257-120. I need to make a special throating reamer to accommodate the oversize bore-riding nose….my mold casts the bore ride section at .253”. I am OK with this as I want to experiment with “freebore” a bit anyway to get this bullet seated out enough in a 250Sav AI to keep the GC in the neck.
OR
you could size the nose.
Ben just did a neat thread (with photos) on nose sizing.

[SCHUETZENBOOMER]

Very informative thread on nose sizing.

My original question probably should have been stated differently. Are any of you sizing 25cal gas checked boolits to .257" instead of .258"(the accepted .001" over) with good results? I can resize the nose to .250" but that does nothing for the 1/4" of "exposed" driving band that is .001" over groove diameter. I have this much of the RCBS 257-120 boolit exposed to keep the gas check in the cartridge(250SavAI) neck. With the use of the Lyman "M" die opening the neck up, I do not have much case tension on the short neck. I am afraid of the first driving band(.125" long) creating too much resistance and forcing the boolit (cast @ 15BHN) back in the neck.