From: Norman Johnson <firstname.lastname@example.org>
Subject: Re: info on bullet casting needed
Date: 25 Jun 1997 15:57:11 -0400
At 02:11 PM 6/24/97 -0400, you wrote:
#> The most important cast
#> bullet characteristic is that it be properly fit the chamber.
#Norm, I have a question here. I have gone off the deep end recently and
#have decided to shoot my Vetterli M1878 Infantry Rifle, so the bolt is
#now being converted to CF. I slugged the bore last night and it
#measures 0.427" exactly. Eventually i plan to cast my own bullets for
#this gun, but for the nonce I've ordered some "tailor mades" because I
#can find them in different weights, specifically 300 grains and 320
#grains. here's the problem, if a problem it be: the one that "looks"
#best to me is by LBT, INc. 320 grain GC type, with a diameter of 0.430"
#and I'm wondering if that extra thou will matter. I slugged with a Lee
#TL-240-SWC bullet also measuring .430" at the start, and it seems to me
#there was a good deal of "obliteration" of the thin grease grooves.
#The other bullets I ordered at 300 grainers, and they are nominally
#0.429" as I have always read that one to two thou above slugged bore
#diameter is the place to start.
#What do you think? Am I being needlessly concerned here? Or is that
#three-thousands increase too much?
Oversized lead bullets, from the standpoint of swaging down to bore size is
not a problem. The problem with oversize bullets CAN be that the loaded
cartridge case neck may not be smaller than the chamber neck. Jamming a
tight fitting cartridge neck into the chamber will not allow the case neck
to expand enough to release the bullet without generating higher than normal
pressures. This is a serious consideration.
Don't know how much of this discussion that I have sent you but.......
Generally, the best bullet size is that of the diameter of the chamber's
throat (not to be confused with the neck diameter), or preferably about
.0005" under it. Where chamber neck diameter would accommodate it, I have
experimented with shooting bullets up to .005" over the slugged barrel
diameter, which so happens is just what you need, with no detectable
increase in pressure, let alone excessive pressure. This I determined using
Ken Waters' pressure comparison method.
Do a chamber cast or equivalent to accurately find your chamber dimensions
and work from there.
An alternative to the chamber cast, which I often use, goes as
1. Take a fired and NOT resized case (one fired in that
particular gun) and cut it off at the junction of the shoulder.
Fill this case to the top with lead. It is easiest to fill the
case with lead and then cut it off.
2. Make or find a pure lead slug (I usually use a HEAVY
unlubricated bullet for that caliber, or a length of bullet swag-
ing wire of appropriate diameter). It must be a little larger in
diameter than the bore.
3. Obtain a length of rod (welding rod?) that fits as close
to bore diameter as you can find. This rod should be no longer
than four inches over barrel length.
4. Having placed the modified case in the chamber (bolt closed),
drop or drive the slug down the barrel until it hits the lead
filled case. Drive the slug in with the rod and a hammer. As
the slug is driven to fill out into the neck-shoulder area the
hammer blows will be dull thuds. When the job is complete, the
hammer will bounce off the rod in a sprightly manner.
5. Open the bolt to extract the modified case. Carefully push
out the lead slug so as not to deform the soft lead. I bag and
mark these "castings" for future reference.
Keep in mind that all this bullet fitting is aimed at accomplishing two goals:
1. To align the bullet and bore axes as closely as possible for good launch
2. To minimize or eliminate gas cutting, which will destroy bullet integrety
Lets assume a two diameter rifle bullet which seems to be the most common in
use today. Ideally the cast bullet should have a nose portion which is a
snug fit in the bore lands. This can be checked by pushing the bullet nose
into the gun's muzzle. If it goes in easily, it is too small to provide
good bore riding/guiding capability. This undersized nose is, sadly,
typical of most off-the-shelf molds. One can sometimes bump up the nose in
a sizer rigged to do so.
In addition, the body section should be about .0005" under the diameter of
the chamber throat (as determined by the process explained above) and the
first driving band should be pressed against the rifling origin. If one
takes the trouble to fit his cartridge to realize these conditions, he has
effectively accomplished a breach seated condition, long recognized as the
most perfect of all launch conditions.
Getting a bullet mold tailored to one's chamber is not that much trouble
these days, with offerings by LBT and others. Last time I looked, I think an
LBT mold built to your specs and alloy preference, was only a few dollars
more than retail for a production mold from Lyman, etc.
Some CBA members use a different approach. They have their chamber
modified/cut with a reamer that is also used to produce a taper die. The
bullet is tapered in the die for a perfect chamber fit. Naturally this is a
more expensive way to do things. Which works better is a matter of endless
#> Using an old C-H Swage-O-Matic bullet swaging press
#Wow! I'd have bet my C-H #304 was the oldest press around, but a
#Swage-o-Matic...you must be as old as I am, purt' near ;-)
I have three of them. Someone on this list accused me of being 140 years
old. I explained that not only am I 140 years old, but that by the Grace of
God I have beaten cancer and intend to be around another 140. 8-)
#> NOTE: Elmer Keith was wrong!
#AIIEEEE!! A HERETIC! I bet you are going to get flak over THAT statement!
He had LOTS of worthwhile experience but we have learned a few things since
Elmer was king.