Aggie01
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Post by Aggie01 on May 21, 2009 10:04:27 GMT -5
I'm considering have a S & W ribbed barrel put on a tight chambered .45 colt (base piece - 44 mag anniversary). I have been unable to find information on twist rates, both the preffered rate of twist for heavy (300 gn+) bullets in a .45 colt, and the twist rate of S & W barrels. JL's site simply notes that he replaces the barrels with a slow twist rate barrel on tight .45 colt conversions. Do I need to be looking at reboring a Model 29 S&W barrel to optimize twist rate to my target bullet weight? I am concerned that a .45 cal S & W barrel may have a twist rate better suited to 200-250gn bullets. Anybody know the numbers? Thanks in advance. Also I already have said Model 29 S&W barrel with pulled threads. Ruined for a S&W, perfect for a Ruger.  |
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Post by Lee Martin on May 21, 2009 10:06:25 GMT -5
I use 1:22" Pac Nor for my 5-shot 45 Colts. Freedom Arms uses 1:24". I don't know S&W's twist rate offhand. -Lee www.singleactions.com |
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Post by J Miller on May 21, 2009 12:19:56 GMT -5
I "think" S&W uses a 1-16 twist rate in the .45 Colt barrels. At least that is what sticks in my mind.
Joe
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Post by Lee Martin on May 21, 2009 12:41:47 GMT -5
Joe....that sounds about right. I know Ruger uses 1:16" for both DA and SA.
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Aggie01
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Post by Aggie01 on May 21, 2009 14:45:18 GMT -5
Sounds like I need to rebore my Mod 29 barrel to 45.
I am unfamiliar with the rebore process - Do I need to wait until whoever I choose has machined off the bottom lug before reboring, or is it something I can do in advance of actually getting the project moving?
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Post by boxhead on May 21, 2009 16:17:45 GMT -5
You can rebore first which I would do as it generally takes months to get done. I have rebores from Cliff LaBounty (now Clearwater Reboring under Jim Dubell) and Al Seigrist whom Dave Clements turned me on to. Bowen uses Clearwater. That said, if Ruger uses a 1:16 and S&W's does as well I don't know if I would bother with a rebore as my Ruger's shoot every weight I have tried just fine. Same for properly throated M25's. Just my $.02...
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shorty500
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Post by shorty500 on May 21, 2009 18:53:52 GMT -5
S&W always get advertised @ 18-3/4" twist in .45Colt vs. 15-16" in their .45ACP models. haven't checked my M25-5 but eyeball guesses it at 18-20 comparing it to Ruger, Freedom Arms & S&W .45ACP guns i have on hand. twist has never mattered much to me in the .45Colt for a few reasons. #1_ have gotten great accuracy from 230 to 320g slugs in twists that ranged from a fast 15" to the slow end @ 24" in the FA .454. long & heavy slugs especially witth slower velocities normally call for faster twist rates but the .45Colt dont seem to care! have shot 400g+ slugs that were actually kind of pointy for the .45 in the FA & gotten great results even at long range with low velocity.personally think that the big .45 is very user friendly as to twist rate just have to pay ALOT of attention to throat/groove/slug diameters to make them shoot
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shorty500
.327 Meteor
too many dirty harry movies created me!
Posts: 912
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Post by shorty500 on May 21, 2009 19:01:10 GMT -5
about 5years ago i got a really WILD hair up my tail and built an oversize5shot 17-4stainless cylinder a fitted into a S&W M625 that was born in .45ACP/AUTORIM. its got the original factory 1 turn in 15" twist barrel meant for 180-230g slugs. has proven to be extremely accurate with 325gKeith slugs at an elevated velocity. won't go into load details because somebody might try it in a stock S&W!! but if you read Linebaugh's opinion of the M25-5 you can get a very close idea of where am at for performance!
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shorty500
.327 Meteor
too many dirty harry movies created me!
Posts: 912
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Post by shorty500 on May 21, 2009 19:14:18 GMT -5
just ran a Quick glance over every reference could find RE: twist rates in the big .45Colt. i found 1-15. 1-16, 1in 18-3/4, 1-20, 1-22 &1-24. am satisfied that @ sometime or another (based on manufacturer listings) that i have owned or testfired them all. firmly believe that groove/throat/slug diameters & alignment mean alot more to the accuracy of the .45Colt than twist. although i will admit that twist can affect velocity with the higher pressure loads as in RUGER ONLY & BEYOND into the 5shot HEAVY conversions
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Aggie01
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Post by Aggie01 on May 21, 2009 23:39:43 GMT -5
Thanks for doing the homework for me shorty500.
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shorty500
.327 Meteor
too many dirty harry movies created me!
Posts: 912
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Post by shorty500 on May 22, 2009 4:15:57 GMT -5
your welcome. things have been so crazy at work lately that hate to come home and go to my shop and start cutting metal allover again,so been coming online alot for some R&R, and the topic was one that interest me too
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Post by nobearsyet on May 24, 2009 11:28:58 GMT -5
I am thinking that one could use the Greenhill formula for this.
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Aggie01
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Post by Aggie01 on May 28, 2009 11:05:07 GMT -5
Just talked to Mr. Linebaugh - 1 in 18" is what he uses for .45 Colt, .475 & .500.
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Post by nobearsyet on May 28, 2009 11:49:25 GMT -5
If someone wants t opost up some bullet LENGTHS for the various cast bullets I can do the math and post in another thread and we can have a whole wealth of information on what you need for twist right here.
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