3 replies [Last post]
Joined: 01/05/2013
Posts: 92
chamber casting

Ok so I was just reading a really old post back from 2009. I'm gonna do it just out of curiosity. But first I'm gonna do what Ole' Don Fisher suggested. Take bolt out, stick bullet in, stick rod down barrel, mark, take rod and bullet out, put bolt back in, put rod back in, mark.

Critter's picture
Grand Slam Challenge Winner!Moderator
Location: Western Colorado
Joined: 03/26/2009
Posts: 4423
And why do you want to do a

And why do you want to do a chamber cast? A chamber cast is actually what it says, you plug the barrel at the chamber and then poor a material such as creosote into the chamber. Let it cool and then remove it. Then you have the actual dimensions of your chamber. What is sounds like that you are doing from what Don said is to determine the over all length (OAL)for that loaded round for your rifle.

What you really need to do is to determine the free-bore of the chamber or the distance from the end of the bullet to where it contacts the rifling of the barrel. Some rifles/bullets shoot better where they are almost touching the rifling and others like a little bit of a jump but then it doesn't do any good if your bullet falls out of the case when you handle it due to the fact that the bullet is seated so far out of the case that the case can't hold it. Also if it is too far out of the case and the loaded round in in the magazine and you shoot a round there is a possibility that the recoil of the rifle will dislodge the bullet in the case that is in the magazine.

You need to purchase a reloading manual. In it it will give you the maximum OAL for the round that you plan to reload. This length can change due to the size of the magazine of the rifle. Some heaver bullets will have to be seated deeper while lighter ones can be further out of the case.

What I did when I first started to reload is to take a factory loaded round with a similar bullet and seated my reloads to the same OAL as the factory round. Then once I got a little bit more experience reloading I played around with seating depths, but for a hunting round you want enough of the bullet in the case to hold it firmly with out it moving when you fire another round in the rifle.

BleuBijou's picture
Location: Loveland , Colorado
Joined: 03/22/2010
Posts: 498
Critter is

Critter is correct! I had to do a chamber cast because I had little idea of what I had in a custom gun that I got used. I needed custom dies for reloading and all i had was 3 spent cartridges and one live round. After the chamber cast I sent it off to one of the major reloading Manufacturers with the spent rounds and they determined what I had and made me some dies. I used the live round for Cartrridge overall length. So what I had was a 30-8mm 35 degree angle improved wildcat. Basically a 300 Jarett . Or a 8mm rem mag necked down to 30 cal with steeper shoulder angles. What a pain to reload for! Best to just get a 300 ultra. Unless you like to play around alot!

Don Fischer's picture
Location: Antelope, Ore
Joined: 03/24/2005
Posts: 3206
I've never had a chamber cast

I've never had a chamber cast done, never had a reason to. If you waqnt to measure free bore, measure without a round in the chamber, to the bolt face. Then to the bullet and then seat a bullet one caliber depth into a case and measure it. Difference between the second and third measurement will be free bore, if there is a difference. Be sure when you seat a bullet to use the same bullet you dropped in to measure the length to the bullet tip. Bullet very some in overall length and that you want to eliminate. Seating one cal depth is what I've always understood to be needed to properly hold the bullet. The max depth I normally use is the base of the bullet to the junction of the neck and shoulder. I like the bullet just off the lands but won't stick a bullet to far out in the case to get it. One rifle I had, a 7mm Rem Mag, I had the chamber long throated to accept a 160gr bullet seated as above and the bullet just off the lands. Thing was a great shooter.

I like mid range bullet weight's but then I don't shoot any magnums any more. I suspect you'll find with your rifle and a bullet 200+grs that the base will intrude on the case some. Not a big deal just be sure to seat to the base of the neck. If it does put the bullet into the case and your action will handle it, you can long throat it. Don't that will give you some free bore with lighter bullet's. I also deticate one bullet for use in each rifle. Mid range for standard cartridges. Heavy for magnums when I used magnums.

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