Chambering Reamer for 45-70 cast thrower

[Wayne Smith]

We're not quite to the point of ordering a barrel for my Martini, but I like to get information ahead of time. My gunsmith likes cast shooting but is not up on the details of building a cast boolit shooter. I get to educate him, and you guys get to educate me.

Is there available a 'best design' finish reamer available for a rifle designated as a cast boolit thrower? I'm thinking throat design here, but don't hesitate to point out other things I or he need to consider. I'll probably be printing this and giving it to him, so write to a gunsmith rather than to a psychologist!

Barrel will most likely be a Green Mountian, configured for hunting or Long Range, I'm not quite sure which.

[45 2.1]

Wayne-

I've measured about 20 chambers, they all will take a 0.462" bullet in a fired case. The chamber could be slightly tighter so a .459" would be a slip fit in a fired case and it would be good. You do not want freebore in this caliber. Ask for a 1 degree lead in the throat. You do not want the chamber length overlength either.

[Rrusse11]

Wayne-

I've measured about 20 chambers, they all will take a 0.462" bullet in a fired case. The chamber could be slightly tighter so a .459" would be a slip fit in a fired case and it would be good. You do not want freebore in this caliber. Ask for a 1 degree lead in the throat. You do not want the chamber length overlength either.

45,
1 degree throat?????? Sure you don't mean 11?? I certainly agree that a tight neck is a good approach, I'd be checking the specific barrel bore before having the reamer cut.
Cheers,
R*2

[Bass Ackward]

We're not quite to the point of ordering a barrel for my Martini, but I like to get information ahead of time. My gunsmith likes cast shooting but is not up on the details of building a cast boolit shooter. I get to educate him, and you guys get to educate me.

Is there available a 'best design' finish reamer available for a rifle designated as a cast boolit thrower? I'm thinking throat design here, but don't hesitate to point out other things I or he need to consider. I'll probably be printing this and giving it to him, so write to a gunsmith rather than to a psychologist!

Barrel will most likely be a Green Mountian, configured for hunting or Long Range, I'm not quite sure which.


Wayne,

The simple answer is that there is no simple answer.

At one time I had three different 45-70 reamers for lead. Each with a different purpose for how and what you want to shoot. Soft or hard bullets, what kind of powder, weight range of the bullets you want to shoot, the groove diameter of the barrel and action type used, which you mention, can affect that recommendation. All of this makes a difference in what " I " would want.

You are pretty much stuck with SAAMI measurements for everything but the throat. And that is as it should be. Some companies will consider what you want for throat dimensions once they get to talk to you. If you get too far out in left field, they will tell you.

But if you are considering a custom barrel, you want the correct size pilot on the reamer you are ordering too. Some of these pilots are small since there is such a wide variety in 45 caliber barrels. If you buy a floating pilot, they can fit you up right. But Green Mountain will have to tell you what their "bore" actually is. Personally, I would actually get my hands on the exact barrel and slug / measure it first. Then go from there.

Let's say that you wanted to shoot light weight bullets at moderate to high velocities. I would recommend a really short throat for deeper seating that was .003 over bore so your bullets could be +.002 to help chamber alignment and ignition with a leade angle of 2 degrees on the rifling. If your barrel comes in at .459 after you planned on .458, then your bullet will only be .001 over so it can have clearance, or .... you have to now get a throater and go back in. Because you had a custom throat cut, you will likely need a custom throater to correct the difference. Or it will affect leade angles too. The best and closet job will come from the origional reamer cut.

So all your planning can go out the window, if you are "serious" about what you want. Otherwise, save the expense and just use a standard reamer and adjust all your shooting factors to it.

Added: I forgot to mention twist rate. The twist rate and weight of slug affects my choice for the the lead angle. The faster the twist and the heavier the bullet, the less throat diameter you need and the sharper the leade angle I would want. Because you have to turn over that big slug without stripping. So you see, this can be pretty involved depending on what you want.

If you throw up your hands in discust and decide on a standard reamer, try and find a used reamer and have it sharpened. They just about always grind them smaller in body and throat.

[45 2.1]

No, I meant 1 degree! Allot of 30 caliber lead bullet bench rifles were throated between 0.75 to 1.5 degrees. There is nothing wrong with most any throat as the factories put in there rifles, from trapdoor to now. 1 degree is very gentle and will allow very soft alloy and paper patched bullets to be used. If you do that, you will need to seat the bullet out to engrave though. You don't mention what rifle you will use either. The Marlin 1895 throat form allows very good accuracy. The ruger, no leade, form needs bullet engraved in throat to shoot extremely well. The most important part to accuracy in the 4570 is getting a bullet that fits, no substitute for that.

I would opt for the slightly tighter chamber and a throat like the Marlins have for a general purpose rifle.

[Willbird]

Dave Kiff at Pacific Precision is my reamer grinder, he will make what you ask for exactly, he also makes bore reamers for many of the major mfg. so he knows what pilot sizes typically work. Dave gets $135.00 for a custom reamer with a live pilot (the live pilot is a must I think), and he gets them done in about 3 weeks.....Dave Manson has many nice things said about him from folks that ought to know, But I was with pacific before Mr. Manson set up his own shop, and I think Pacific is a bit cheaper, and a bit faster. I have been very very happy with Dave Kiff 's work.

I would think once you had the reamer you could rent her out for about what www.reamerrentals.com gets and eventually re-coup your investmant. escpeially if you keep posting little teeny groups shot from that chamber :-)

Dave Kiff also makes the reamers for Midway, and it might be a tad cheaper to buy one there and have him alter it to suit your tastes, Midway mentions that you can send the reamers Dave makes to him for sharpening and adding live pilots to ones that have solid pilot, ect.

Bill

[Leftoverdj]

I had a 1 1/2 degree throater for the .45-70 and it seemed to make an accuracy difference. Can't say for certain because bullets for the rethroated Handi needed to be seated out a bit and the charge slightly adjusted, but I did get improved accuracy when those changes were made. Were I building a custom .45-70, I would certainly go with a long leade.

[Willbird]

Also when I said "custom" what I cut/pasted below does not apply with Mr. Kiff, give him the specs and he will make it, He would advise you if you were out in left field I'm sure.

Rifles with custom chambers should of course have the bbl clearly stamped to note that fact.

Bill





>You are pretty much stuck with SAAMI measurements for everything but >the throat. And that is as it should be. Some companies will consider what >you want for throat dimensions once they get to talk to you.