Custom barrel chambers for cast boolits

[30hrrtt]

When ordering a custom barrel for a firearm that is going to be used for shooting cast, how is the chamber/throat cut differently than that of a barrel shooting jacketed?

[leftiye]

Actually, since we've spent our lives figgerin' out how to make existing chambers shoot cast boolits, there's usually little done in the way of making chambers for cast. You should look at http://castboolits.gunloads.com/showthread.php?214329-30-XCB-wildcat-from-scratch, and http://castboolits.gunloads.com/showthread.php?207534-Malcolm-Ballistic-Tool-%28MBT%29-long-range-rifle. Two threads on accurate cast rifles.

Milder leades, special cartridges with longer necks, minimal neck clearance, freebore sufficient to guide boolit into leade (not to mention boolit seated against rifling) for a few. Oh, did I mention a cartridge friendly to cast?

[runfiverun]

there isn't a ton of differences.
the link leftiye posted on the top goes directly to gears post on the 30-xcb.
his opening post pretty much covers what is looked for.
the differences may be hard to spot unless you are familiar with how a factory chamber is actually cut versus how it's drawn, that's where the differences really are.

[Larry Gibson]

Since you are rebarreling why not have the chamber/throat cut to fit for a cast bullet?

I suggest a tight neck and minimal body diameter in the chamber. There are many such "match" reamers available and also minimal chamber reamers for pressure test barrels. This allows minimal expansion of the case body and the neck. For cast bullets minimal expansion of the case neck is best as that gives minimal room for the bullet to obturate in the case. It thus doesn't have to be swaged down in the throat again causing imbalances which adversely affect accuracy. This is important if softer alloys are used for hunting and/or you are push higher pressures in the cartridge.

If you have a particular cast bullet you plan to use the most then why not prep 3 - 5 cases with uniform turned necks and that bullet seated so the GC is at the base of the case neck and then have the chamber neck cut for .001 - .002 neck clearance and the throat cut so the leade bumps the front driving band of the bullet? An 11 degree cut on the lead is suggest also.

It's your money you are spending on a barrel so why have "ordinary" when you can have the chamber/throat cut to what your needs/wants are? I also suggest you consider a correct twist in the barrel for cast bullets and not a "generic" one twist fits all bullets.

Larry Gibson

[waksupi]

I've just used standard barrels, with nothing special done to them, and they shoot very well. Don't go with a match reamer. I consider those a foolish thing to do to any rifle other than what the stated purpose is, match. Felix may be able to put in on this, if he used match chambers in his competition rifles. I recall as a rule he does not favor them.

[felix]

Ric (Waksupi) is correct because match guns are set up to shoot one "standard" load. The guns are typically not flexible enough for a general purpose hobbyist. The gun's neck thickness, freebore length, and leade angle are very critical for a particular boolit/bullet design. The idea for a match gun is to push the gun and ammo out of the equation, in order to encourage the shooter to accept full responsibility for his scores/groups. So, all said and done, if everyone shoots the "same" thing, it's gotta' be the shooter!!! ... felix

[Larry Gibson]

There is a reason match shooters use match chambers......better scores, i.e. better accuracy.

I have several rifles with match chambers and find they all do exceptionally well with a wide variety of cast bullets......all w/o the "spent our lives figgerin' out how to make existing chambers shoot cast boolits" problems associated with "normal" chambers. The tighter spec match cambers just shoot better, with cast and jacketed bullets.

If you're spending the $s anyway then why not have the best instead of settling for "normal" is the point. Otherwise save yourself some $s and just buy another factory rifle off the shelf.

The point is made so it's up to the OP what he wants to do.

Larry Gibson

[btroj]

Difference is between a BR match chamber and a Palma or high power match chamber.
I don't want the hassle of an extremely tight chamber like a BR gun has but I sure don't want the slop of a standard chamber either.

A match chamber like a Palma or high power shooter uses fits me fine. Snug enough to keep rounds in the middle but not so tight that lots of neck turning is required.

There is too big, too small, I want just right.