Question on gas checked cast bullets; sizing, weight, and more...

[Blackhawker]

For starters, I am NOT a caster but I shoot and purchase a LOT of cast bullets from mainly two suppliers.  I have recently purchased some 30 cal bullets which were inteneded for use in the 30 M1 carbine cartridge but not an M1 rifle so bullet shape and length need not conform to magazine confines.  

The bullet that was chosen and that is in question is the Lyman #311359.  The bullets I received from the caster are supposed to be .310", as specified by the caster and which I don't know why he chose that size over .309?  Nonetheless, I measured several bullets from the lot and each measure .311 to .312 on the gas check and .310 to .3105 on the actual bearing surface of the bullet.  Which is the correct place to measure when checking sizing...on the gas check or on the bearing surface of the bullet?  For that matter, shouldn't these measurements be the same?  Not being a caster and not knowing the actual processes, I assume that a gas check is placed on a bullet as it is being sized and therefore both areas/surfaces should measure the same....is that correct?

A second question is in reference to the weight of the bullets.  According to the mould, this bullet should weigh 115 grains yet these bullets (with lube and gas check) are weighing 127.5 grains.  Is this acceptable being that alloy densities can vary and that the bullet is being weighed with lube and gas check or should the bullet be closer to the listed 115 grains with lube and a gas check?

Lastly, I plan on shooting these bullets from a Thompson Contender pistol and carbine as well as an old model Ruger Blackhawk and I may use them in my 30-30 T/C pistol as well...or at least was planning on doing so.  I'm now second guessing these bullets however, since the diameters seem far from 0.309".  Am I correct in my thoughts here?

Thanks,
Blackhawker

[hornady]

Hi new on this form but have been casting for a while, I will try to answer some of your questions, in the 30 cal rifles .001 over bore is the standard size, some will go up too .002, having said that the only way you will know what bullet diameter to shoot in your rifle would be to slug the barrel, it could be anywhere from the .309 to .313.
Yes gas checks are now pressed on in the sizing die, years ago we would glue them on with epoxy, what a mess, but I don’t think anyone dose that anymore,
As to bullet weight, most mold makers set the weight and diameter a bullet will drop from the mold when an alloy known as Lyman #2 is used, the alloy used will greatly effect not only hardness but also weight and diameter of the Bullet.

[Blackhawker]

Thanks for your reply hornady.  The bores on my T/C's are all .308.  With that, I believe that the .311's and .312's are much too large for these barrels and will generate high pressures, wouldn't you agree?  At this point I'm not sure what to do with the bullets.  Since they're 127 grains, they'd probably lend themselves to being a good bullet in a 32-20 or a 7.62X39 since they're gas checked, but I don't have either. 

Thanks for the other info on the casting/sizing techniques. 

[Larry Gibson]

Blackhawker

It is commonly believed that a cast bullet should be .001" over the groove diameter of the barrel.  While that works out "ok" it is best if the bullets diameter fits the chamber throat.  I regularly use .311 sized cast bullets regardles of the groove size for most all .30 cals with 2 exceptions; the .30 Carbine and the .30-30 in my Contender.  I use .309 in both of those.  The reason is that the chamber neck areas are to tight to allow easy chambering with bullets of .310 or larger.  I shot cast bullets (including thousands of 311359s) in many, many M1 Carbines and they bat about 50% on chambering anything larger than a .309 bullet.  The Chamber on my 21" Contender barrel has a very tight chamber so it is what it is.  I've not found a M94 or M336 in 30-30 that would not take a .311 sized bullet on the other hand.

If the 311359s are to large for your rifle/handguns chambers then simply get a Lee .309 sizer and push the bullets through.  It will nicely size them with little trouble. As to the .311 bullets increasing pressures they do not.  I measure pressures BTW with an Oehler M43 PBL.  The bullet will travel it's first bearing length very early in the time/pressure cycle.  After that first bearing length it is sized down to fit the barrel and during the rest of the barrel trip the pressure is the same as if it were groove diameter.  I have measured the pressures in the Contender and in a M94 30-30s with cast bullets of .308, .309, .310, .311 and .312 withe identical load and could discern no difference in pressure (PMAP: Peak Maximum Average Pressure) between them.  I have also done the same experiment with other calibers/cartridges and the result was the same; no dicernable difference in the PMAP.

As to the 127 gr weight of the bullets that is a little on the heavy side but not unusual.  Most 311359 moulds I've delt with cast bullets (GC'd and lubed) between 120 and 125 gr when cast of wheel weights or #2 alloy.  With good pure linotype you can get the weight down but its not necessary. 

Larry Gibson

[Blackhawker]

Larry,
Thanks for all of the very valuable info. 

I just checked Midway's website and it appears that their bullet sizers can be used on a regular press for loading ammo.  What I don't see is a bullet holder.  Will I have to buy a bullet holder and the die to do this?  Second question; the instructions I read on the Midway site say that I'll have to lube the bullets with alox, however, the bullets I have are already lubed....will I be able to skip the lube step and just run them through the sizer?

Thanks again Larry,
Chris

[Drilling Man]

Thanks for your reply hornady.  The bores on my T/C's are all .308.  With that, I believe that the .311's and .312's are much too large for these barrels and will generate high pressures, wouldn't you agree?  At this point I'm not sure what to do with the bullets.  Since they're 127 grains, they'd probably lend themselves to being a good bullet in a 32-20 or a 7.62X39 since they're gas checked, but I don't have either. 

Thanks for the other info on the casting/sizing techniques. 

  How do you know your TC's are .308"?  Did you actually slug them, or are you assumeing that?

  Personally, i'd try them as they are before i got too worried about it all.  I just wouldn't "start out" with a full power load...

  DM

[leadman]

I would make up a dummy round (no powder or primer) for each firearm you want to use these bullets in. If the cartridge will not chamber and you want to size the bullet down to .309" use the Lee push thru sizer as Larry suggested. The sizer comes with the die and the post that goes in the shell holder slot in the press ram. Since your cases are lubed you will not have to do this.

I do as Larry does, size the bullet to the throat dimensions of the barrel just in front of the chamber. If the bullet is smaller than the throat dimensions the gases can blow-by and cause problems.

[Blackhawker]

I bought the Lee sizer and sized a few bullets just to give it a try.  It's as easy as can be to do!  However, I'm going to take the advice given by most and check the throat of the barrel.  I know the T/C's bores are all four ( 30 carbine's and 30-30's) very close to .308 as I have slugged them in the past.  I've never slugged the Blackhawk however, and I'll have to do that. 

Thanks for the info on the throating and the lube question Leadman.  Thanks to all!
Chris

[jsh]

I have been shooting CB's in TC's for about the last 10 years. Larry states his barrel has a tight chamber. I have had maybe two factory TC barrels that had tight chambers in the last 25 years, but all of them had generous throat in them, tapered like a forcing cone. CB's have caused me to cuss and discuss a couple of the TC's, but I worked through it fairly easy. After I made it no harder than it should have to begin with,lol.
I have one TC barrel that slugged at .308 the rest slugged at .309+. I have ran from .310-.312 in most of them. Distances past 100 show a lot more than anything under that.
The first TC barrel I tried slugged the throat at .308+. But a fired case and a chamber cast showed it would shoot and chamber a .312 easily. So, make sure you check the neck area of the chamber. I did swap around some brass and found some 30-30 brass that was a bit thicker than some, seems like it was PMC, I don't recall for sure as I have slept since then
As to large chambers. I only partial size the necks, then run them through an M die. ABout half of the neck length centers the case and the rest holds the CB.
jeff

[Reverend Recoil]

You will also need an expanding die to load your 30 cal bullets.  The Lyman M-die and Lee universal expanding die both work well.