Making a Chamber casting

Mark W. · Mar 9, 2011

Before I start developing loads for my Winchester Model 1895 in 30-40 Krag I would like to get an idea of how far from the end of the neck the rifling starts. The logical thing is to make a Chamber casting and meassure it.

That said Midway sells a low melting temp metal for this chore. But at $19.99 + shipping I would like to find a cheaper DIY method.

Can anyone see a reason a Parifin wax cast wouldn't work. I'm not looking for any critical dimentions or angles. I just want to know the distance to the rifling so I can find those bullet designs best suited for a rifle and cartridge combo known for it's long throat.

If I have 2-3 rifles to do this with the metal would be a better option. But with my other rifles its just not a worry.

cyclesurvival · Mar 9, 2011

Go to a jewley supply store and get some casting wax very little shrinkage. should be able to a realy close measurement.

Mark W. · Mar 9, 2011

There is no shrinkage with Parifin otherwise it wouldn't work to seal Jelly jars etc. Hence my question about using it for this. The 30-40 is a full tapered case so it should break free pretty easy.

RockKrawler · Mar 9, 2011

I like to use the Cerrosafe for chamber casts,it will give you a very accurate measurement if the directions are followed,and it can be reused.
RK

BillM · Mar 9, 2011

Ummm---Just "bump" a case into the sizing die and size down the end of the neck. Seat a bullet extra long. Coat the bullet with sight black, magic marker, dykem--whatever. Chamber, extract, measure from the neck to the rifling marks on the bullet? That said, buy some Cerrosafe. I use it for all sorts of stuff. It's great for holding odd shaped things to machine etc. If you don't overheat it, it will last a long time.

nrc · Mar 9, 2011

+ what BillM said.

A dummy round will tell most of what you need to know. If that doesn't satisfy; either pick up some cerrosafe from midway/brownells etc; or maybe post on the WTB forum. If I had some I'd give it to you...

AMProducts · Mar 9, 2011

I know this topic has come up before, and yes, 100% what Bill just said.

Cerrosafe has a number of principle design considerations that make it ideal for chamber casting, but not necessarily getting throat dimensions. Among them are the fact that cerrosafe contains a large quantity of antimony, one of the few materials in nature which is less dense as a solid than as a liquid (water is the other). this allows the alloy to maintain it's dimensions as it solidifies. Parrafin wax does contract very significantly as it solidifies, this is why all jars canned with wax have a depression in the middle of them, and why candles are swaged, or built up by dipping rather than just bulk cast.

If you are really interested, there are a few tools out there to do exactly this. They used to be made by stoney point, but are now manufactured by hornady.

<broken link removed>

Mark W. · Mar 9, 2011

so maybe I try the long bullet method seams the easiest. The Cerrosafe method just isn't in the budget right now.

rodell · Mar 10, 2011

As pointed out above, Hornady makes a length gauge (used to be Stoney Point) that is designed to do exactly what you do with an extra long bullet protruding from the case. They have a special case that is neck sized and held to tight tolerances. For most purposes, the dummy cartridge works just as well.

Just remember you will need to repeat the measurement for different bullet shapes as the ogive will contact the rifling at a different point.

Spitpatch · Mar 12, 2011

A little trick I learned in the Hebrew Navy:
BillM's idea, but select a bullet that has a flat base (not a boattail), and the sharper the corners on the flat base the better.

Seat the bullet upside down in an empty, resized case. Seat it extremely long. Then chamber it slowly.

The result will not be a "cast" of your chamber and throat, but it will be a very accurate representation of where your rifling will engage the true diameter of a bullet (ogive) properly seated. Calipers will measure this length for you, and then give you a reference point to begin seating experimentation with bullets right-side-up.

Each gun, each barrel will have a preference for how close it likes a certain bullet to be seated to the rifling. If you change bullets, this will change.

Having done all this work, you may have to throw it all in the garbage when you realize the magazine length of your '95 might dictate you cannot seat your bullets long enough to come close to the rifling.

Mark W. · Mar 12, 2011

I took a 220gr RN slug and seated it out as far as I could and keep it consentric with the case. I then coated it with black sharpie and chambered it. I managed to get decent marks from the lands starting just about .250 from the end of that paticular case or 2.56" from the end of the case (measured like you would OAL) I had no problem with even that lenght fitting in the magazine so I can't imagine any properly seated bullet not fitting in the magazine.

I'm reading up on this stuff and will figure out what type of test loads I'll make up for this.

A real limitation to this type of testing is going to be the bench. With the Lyman receiver mount peep site having such a large aperture (afterall it was designed for hunting not shooting groups on paper) there is a limit as to how accurately I can even sight the rifle.

I am working on making a target style aperture for the peep sight that will help. But it will never be like having a 9X-16X scope on top of the rifle for working up accurate loads.

My first test loads are going to simply be Hornady good old fashion 150gr flat base soft spire points seated to a reasonable depth. I figure I might as well start with a test to show me if I even need to get fancier.

When Construction season starts and I have some OT money I'll buy up a few boxes of various ballistic tip type 150gr bullets and see if I find any improvement.

I'm also going to load up some 180gr Round nose slugs to use as a base line.

Spitpatch · Mar 12, 2011

Mark, do not discount the precise accuracy that can be achieved with a peep sight, even if the aperture seems somewhat large. Your eye will automatically center that front bead for you, and if you give it just a bit of thought each time, your concious effort will make that centering nearly every bit as accurate as it would be with a smaller aperture. Certainly at least as accurate as any scope. One thing to keep in mind: the error (even if you try really hard to make it error) CANNOT ever exceed the actual size of that aperture. (less than a millimeter?)

If you are able to see your target, and able to see your front sight, and the target is of the type that allows you to precisely place that front sight in the same place on the target each time, there is NO reason ANY rifle cannot shoot as accurately with a peep sight as it can with a scope. Even at very long ranges. Ask the Blackpowder Silouette guys, and the military highpower guys.

When I was young and dumb, and shooting smallbore competition, I decided I'd really make my Anschutz a tackdriving sage-rat gun. I put a 10 power scope on the dovetail, and removed the big rear peep. No matter how hard I tried, I could not get that gun to shoot as accurately as it did with the rear peep/globe front: AS LONG AS I COULD SEE THE TARGET. The only advantage to a scope over peep sights is enabling you to see the target (usually only at longer ranges).

If you are uncomfortable with the size of the aperture, a solution I used on a .22 that did not have a removeable aperture was to find a very tiny plastic bead (like for indian beadwork or earring/jewelry making craft shops sell). I softened it with heat and inserted it into the existing aperture, thus "bushing" the aperture to a veritable pinhole (the hole in the bead that thread would go thru). You don't want this when you go hunting (and so it is easily removable with no damage to the gun, but you may have to use a new plastic bead when you go back to small aperture).