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Thread: How thin a barrel for .45 / .458 caliber sizes?

  1. #11
    Always sore, always tired Bradrock's Avatar
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    The dimensions I've got for the .50 Beowulf barrel are .906 at gas block & .980 under handguards. I think that was a Trommix rifle.
    The pressures may be similar?
    " Save a tree...........Eat A Beaver!"

  2. #12
    Gunco Regular Gunter's Avatar
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    1biggun, I also was wondering how aluminum would work for a GB. Just a machined sleeve for the piston to ride in and the tube to sit on.

    Bradrock, I could get a pic of my custom RSB on the .308 if you want. A lot like 1biggun's thinned a little and a Saiga handguard reworked a little to fit together.

    ETA: Looking at the 50-110 pic again it looks like it might be a custom GB??? Also is the front sight on backwards? The slope to the front?

  3. #13
    No Hope For Me 1biggun's Avatar
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    The AR 15 and others use aluminum for the gas block I am not sure what pressures they actually encounter. the AK piston is fairly loose fitting so I dont think the block handels any were near the chamber pressures that are in the barrel. On the one I made for my varmit build I made the hole in the bloc considerably larger than the hole in the actual barrel so not to act as a restriction and build up any pressure and possably make it flow better in hopes of being able to cycle the action with smaller port in the barrel. I am planning to use aluminum on my next varmit build (17-223) I dont think there will be any problem as long as there is enough material around the barrel. I am not sure if piston wear on the aluminum block would be a big factor or not, a sleave would not hurt for that matter, one could sleave the entire port buy pressing in a steel rod then drilling it out. I am planing on building a heavy varmit build (18 pounds aprox) and a very light weight version that I can pack. I was thinking aluminum RSB and GB.
    Another way to go for the RSB is to trim off the bottom were the barrel runs through it and weld it to the trunion as susgested else were on several other threads. then the barrel would not even touch it. I personaly dont like the idea of welding to the trunion but a couple light tacs to the other edges likely wont hurt.

  4. #14
    Happy Camper hcpookie's Avatar
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    Quote Originally Posted by Bradrock
    The dimensions I've got for the .50 Beowulf barrel are .906 at gas block & .980 under handguards. I think that was a Trommix rifle.
    The pressures may be similar?
    Thanks, that helps. I guess this is going to have to have a custom-built gas block.

    Here's a pic of that rechambered PSL. Notice the thickness of the barrel. I wonder now if that is a custom gas block on that. Looks almost like a Yugo gas block. Yes, I agree that the front sight is on backwards:





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  5. #15
    No Hope For Me 1biggun's Avatar
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    the gas block looks like a standard one cut down an welded to a sleave or a completely custom made one. I got my hands on some 45-70 ammo today to play with very interesting. I also noticed in my Midway catolog that they show barrel blanks for the 45-70 differant from the .458 blanks not sure why?? possably differant twist or is the bore not .458 on the 45-70???

  6. #16
    Happy Camper hcpookie's Avatar
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    Correct on the twist - it appears to use a specific twist barrel.

    I didn't think about a pipe that was welded on - good idea. I have an AK gas block that will be *perfect* for this.

    What kind of ammo did you get? There are about 3 different flavors of 45-70 in my reloading manuals, depending on the rifle intended. The black powder kind is the light load, usually 405 grains. Mid-weight loads are for the old falling block and Winchester rifles, and the heavy loads are for the new heavy hunting rifles only, usually the Ruger Mk1.

    Look up the pressures on the Hodgdon website, and you'll see the loads are lighter pressure than what the 7.62x54R chamber is designed for, except for one or two hot loads that are up to 50,000 CUP (the 350 grain I think). The bottom line is that the PSL action should handle any load in 45-70.


    There is a .45-70 barrel on e-gunparts.com (Numrich) that are for the Marlin IIRC, and has all the dovetails for the sights, etc. I didnt' want to use that one because the chamber is going to need some finessing to work in an AK action. Namely, the threaded section will need to be sleeved, and it will need to be thinned some.

    The barrels on Midway *appear* to be unchambered. I haven't called yet, but all the rest in that category need to be chambered.
    Last edited by hcpookie; 04-03-2008 at 12:34 PM.
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  7. #17
    No Hope For Me 1biggun's Avatar
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    I think I am getting a H&R single shot in 45-70 in a trade. the guy had some misc ammo that he gave me to play with. some lead bullets some jacketed. the other Gas bloc that may work is the FAL even though it is a little out of line it can be made to work and is adjustiable. I need to get me a bolt and carrier. to play with. all this has me thinkng of some other rimmed cartridges as well.

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