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Post by 22boomer on Jun 5, 2011 12:19:44 GMT -5
I just got this together and have made up some brass to fire form. The dummy rounds feed smooth as silk from the Pmag. The barrel is short so I had to have a moderator installed as in pinned and welded to bring the length to 16"+. I need to make up some loads and should be able to test in a couple of weeks. this is just a test setup to see just how good the 256 Winchester Magnum rimless might be.
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Post by greywuuf on Jun 5, 2011 16:08:19 GMT -5
these the rounds you formed using .223 brass ? Can you detail the final steps it took to get here ? I know you were trying various methods, what did you settlle on ?
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Post by 22boomer on Jun 5, 2011 19:33:38 GMT -5
these the rounds you formed using .223 brass ? Can you detail the final steps it took to get here ? I know you were trying various methods, what did you settlle on ? The barrel was given to me so I had no idea as to the exact chamber dimensions. First I tried to make some cases just going by the specs of the rimed 256WM but I found, when I got the barrel back, that the cases were way too short. I kept making some a little longer till I got to the point that the bolt would not close on a case with a piece of masking tape on the end. This is how I got there -- I started the shoulder on the .223 brass with a 7.62X25 FL die (push the shoulder all the way to just about where the 256 WM die will put it) then I finished it with the 256 WM die. I cut the exess neck off with a mini chop-saw then ran it through the 256 WM FL die again but with the expander ball in place. I needed the inside neck size to match the guide on the Forster case trimmer. I trimmed the cases to 1.30" (that's what works in my chamber) and the neck length is 0.208". I can't get a true shoulder measurement since they are a bit rounded -- not fire formed yet. I guess I could probably cut the .223 brass with the chop-saw first to some pre-determined length then form in the 7.62 tok die then go to the 256 WM die with the expander ball in place to begin with then go to the case trimmer. The neck thickness comes out perfect without any turning or reaming. I just had to be careful with the neck length -- too long and the dummy cartridge will jam. The 256 WM specs say the neck is 0.208" long and I found this works perfect.
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Post by greywuuf on Jun 5, 2011 19:45:56 GMT -5
hmmmm going from memory 1.30 sounds like 1.28 plus the rim thickness sounds like the chamber is probably close to spec ...if it was relieved for the rim ... which you don't have but all in all it sounds like it is about what you would expect. I am anxiously awaiting the range report I think it is a very interesting lil round.
What twist and what bullets do you plan to try ? I THINK it is sierra that makes some half jacket soft point flat nose bullets ( kinda like a mini .357 bullet) designed for the 25-20 win that was just devastating from my little 10" barrel contender. I know a pistol bullet is not very "sexy" in a carbine but it would be just the ticket on coyotes or some such that you was not fur hunting.
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Post by 22boomer on Jun 6, 2011 4:59:04 GMT -5
hmmmm going from memory 1.30 sounds like 1.28 plus the rim thickness sounds like the chamber is probably close to spec ...if it was relieved for the rim ... which you don't have but all in all it sounds like it is about what you would expect. I am anxiously awaiting the range report I think it is a very interesting lil round. What twist and what bullets do you plan to try ? I THINK it is sierra that makes some half jacket soft point flat nose bullets ( kinda like a mini .357 bullet) designed for the 25-20 win that was just devastating from my little 10" barrel contender. I know a pistol bullet is not very "sexy" in a carbine but it would be just the ticket on coyotes or some such that you was not fur hunting. I had thought that maybe it was the difference between the original being rimed and this one being rimless but I didn't have the barrel at the time to play with overall length. Since this rifle is an AR I'm going with pointed bullets -- the Sierra 70gr blitzKing. The original barrel was 11.5" long and was the reason I had the custom 607 type moderator permanently attached to bring the barrel length to 16.1". I'm going to try Lil' Gun powder but I have not had a chance to do any loads yet. The gas system is pistol length -- that front sight/gas block is there to hold the handguards. If you look real close at the upper half of the handguards -- the 7th rib out from the delta ring -- you can just see a small hole drilled in it. I'm using an adjustable gas block and needed a hole for the allen wrench. By the way -- that barrel is Melonited.
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Post by greywuuf on Jun 6, 2011 16:48:18 GMT -5
hopefully your barrel is faster than mine. TC used I think old 25-20 blanks and had something very slow 12 or 16 if I recall maybe even slower, the result was that it handled both 60 and 86 grain flatpoints well but none of the pointed bullets I tried would stabilize. I know I have some green box ( Sierra or speer) in either 70 or 75 grain that i tried and then the 87 grain Solid base hornady boat tail nylon tips ( NICE looking bullet) that failed miserably. all from a 10" barrle and a stiff load of 2400. it was about this time that a mistake with emptying a powder measure resulted in some really exciting loads of 2400, duplex'd with unique. definately NOT recommended. ( blown primer pockets and bullet frag's on a 25 yard target..... gun and shooter survived)
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Post by 22boomer on Jun 6, 2011 19:18:11 GMT -5
I was told that the twist rate is 1:14 so I hope the bullets work. I can get round nosed bullets to feed but I don't see a great variety of light bullets, either round nosed or pointed for 25 caliber.
Edit to add: I went and did a twist rate calculation for a 70gr bullet that's 0.883" long through a 1:14 twist barrel and it came up a no go. I was now worried about the barrel so I did what I should have done when I got the barrel and checked the twist myself. The twist on the barrel is 1:10 which gives me a really good range of bullets weights to work with.
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Post by HMC710 on Jun 7, 2011 6:40:36 GMT -5
Any of those twist formulas take into account velocity? Running a 180 out of a 30-06 is much different than a Tok sub..... I remember Marty from Teppo Jutsu sharing about trying to spin .338 bullets even with a 1:7....
Nice job 22! Keep us posted.
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Post by 22boomer on Jun 7, 2011 8:39:37 GMT -5
Any of those twist formulas take into account velocity? Running a 180 out of a 30-06 is much different than a Tok sub..... I remember Marty from Teppo Jutsu sharing about trying to spin .338 bullets even with a 1:7.... Nice job 22! Keep us posted. Actually the program takes into account, Bullet diameter Bullet weight Bullet length Rate of twist muzzle velocity There is also temperature and altitude. I figured between 2000fps and 2300fps and the program gave an answer the showed the rate was perfect for the bullet I'm trying. Funny you should mention Marty, he gave me the barrel to test with.
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Post by greywuuf on Jun 8, 2011 6:28:59 GMT -5
I forgot to comment on your case forming method, I think you are doing it just right, from all the anecdotal evidence I have heard using an already necked round and then pushing the shoulder back is easier and more consistent than cutting first and then trying to form a new shoulder. I know all the brass I shoved WAY into the Tok die seem pretty round and centered, albeit REAL funny looking with dual shoulders and a inch long neck ;-)
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Post by 22boomer on Jun 8, 2011 9:22:22 GMT -5
I've got to work on the forming still. I made up some rounds to fire form and after they were shot I measured the necks and they came up 0.202" in length, not the correct 0.208". I guess I'm off a bit still in the head space area. The carbine operated really nice. First tests were with 12.5gr of Lil' Gun and the second was 12.8gr of H110. I may try to get my hands on some H4227 and see how that works.
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Post by greywuuf on Jun 8, 2011 23:22:11 GMT -5
as long as you dont mix any unique in with it, 2400 has worked pretty well for me in .256 AND .357 ( parent case)
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Post by 22boomer on Jun 9, 2011 4:44:31 GMT -5
as long as you dont mix any unique in with it, 2400 has worked pretty well for me in .256 AND .357 ( parent case) I have to keep in mind that this is a very short barrel on this carbine and I need to look more into using pistol type loads. I increased the length of the cartridge to help with the disappearing neck problem. I can only guess that the pre-fire formed shape was causing a little problem. The new overall case length is 1.33" with a 0.207" neck length. Fired cases are coming out almost like they went in -- just a much better formed shoulder and the neck stays the same. I will try not to mix my powders.
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Post by greywuuf on Jun 9, 2011 13:58:42 GMT -5
at various times, in magnum pistols I have also used 296, ( very simmilar to one h110) hs6 and hs7 ..... though I seem to recall only using these with pretty heavy bullet loads 4227 has worked pretty well for me in a number of 22 jet loadings. with such a small case and relatively light bullets ( compared to say a straight wall pistol ) I would be realy interested in something like a unique load, I have a 7 grain load for lighter bullets in a 45 long colt that I like or economy ( 1000 rounds a pound) I have not looked into a fast pistol powder in a smal case gas operated gun so i could be just blowing smoke there.......but anymore I find myself stretching the economy end more than the velocity end of things.
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Post by HMC710 on Jun 10, 2011 6:24:03 GMT -5
Unique is a bit too fast for the Tok to reliably operate the gas system.....
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