Sizing question for Mosin Nagant

[Jazzcat]

After a lot of reading on different forums I am still faced with a question.

Here is my quandry:

My 2 Mosins both slugged at .3105 - .311.

I have ordered the Lee .312 155gr mold.

I will be installing gas checks made on a Freechex II so I plan to use a Lee sizer to install the gas checks.

The question is should I get the .311 sizer or the .314 sizer?

If I weren't installing gas checks it wouldn't be a problem since I could probably shoot them as cast, don't you think?

If the bullets drop small I could beagle the mold and get the diameter of the bullet up but I would have to be careful to not increase the shank size so the gas checks still fit.

If they drop over .312 it shouldn't be a problem. It is just a question of which sizer to buy for the time being.

My mold will be here tomorrow and I will cast some bullets next weekend. I just need to know which way to go on the sizer.

Any suggestions would be appreciated.

[I'll Make Mine]

I'd suggest getting the .311; you can easily lap it out a thousandth, if you find the boolits don't shoot well due to being undersize (highly probable). My experience with the two Lee molds I have (but very limited casting with either) is that they drop significantly oversize with straight clip-on wheel weights; the .309 drops about .311, while the .314 drops .317; I doubt you'll have to worry much about Lee molds dropping undersize.

[Larry Gibson]

.311, then lap out as mentioned to .312. I size my C312-180-2R at .312 and it shoots extremely well in all MNs that have .312 or less groove diameters.

Larry Gibson

[tomme boy]

Yep, get the 0.311" and lap it. Go slow and check it often. Make sure to lube the boolit to check the size after lapping. A dry boolit will give a bad reading.

[Artful]

I hone them out with emery cloth on a split dowel, and mirror polish with FLITZ or Simichrome.

[rintinglen]

I hone them out with emery cloth on a split dowel, and mirror polish with FLITZ or Simichrome.

+1. I do exactly the same thing, except I use 400 grit sand paper and a slow speed electric drill. Be sure to have a handfull of boolits to size, as you'll want to check often. Size the boolit, then measure the sized boolit. When you get the size you want, take a simichrome polish soaked patch and run it in and out a few times, until the bore is shiney smooth, then clean the die with several patches of cleaning solvent to get any left over grit out to prevent dammage to your gun's bore later.