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Old May 29, 2012, 12:41 AM   #1
Jim March
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FrankenRuger MAX saga part two: we have a BARREL!

Part one started here:

http://thefiringline.com/forums/showthread.php?t=489006

So browsing on Fleabay I came across a 6.5" piece of Douglas Premium barrel in 9mm (true .355) left over from a rifle project. For $15 I was all over it.



I can't photograph the inside very well but let's just say "Premium" doesn't even begin. Mirror-finish, clean-as-hell lands and grooves, just...awesome .

Now, there's a problem here. The fattest part is just a tad bigger than it needs to be for an 11/16th-24tpi thread, which is good. But at only .5" long, it's barely long enough to form barrel threads out of.

If the cylinder was of the stock length it wouldn't work out, because it would have to poke back about 3/16ths to meet the cylinder and the remaining thread length would be pretty marginal. Not a place I'd want to go.

BUT, I'm not going to be using a stock cylinder. I'll be using a Bowen blank which is over-long, to allow chambering in long shells like the 218 Bee. So it would meet up with the barrel fairly far forward.

In this setup, a threaded end-cap at the muzzle (unknown thread type, but that's a solvable problem) would push an outer barrel shroud tube back against the frame "Dan Wesson style", so the Douglas barrel on it's own doesn't need to get "screwed in tight" in the conventional fashion.

But I don't really like that. I'm calling it "Plan A". "Plan B" is even weirder:



I don't know if the lathe I have access to can re-bore the stock barrel (shortened to 1.5" or so?) to .57" smoothbore while keeping everything concentric. I should be able to find out Thursday when I can pick the brains of the two machinists I have access to. IF that can be done then yeah, we're good to go: put the Douglas barrel inside that modified stock barrel, screw the stock barrel in tight, tension the inner barrel via a muzzle-end nut pushing a barrel shroud against the front of what's left of the stock barrel.

That remaining stub of a stock barrel can be turned on the lathe to have a slightly "pointed" forward face, so that the shroud auto-centers on it as everything is cranked down from the muzzle end.

I'll also need a way to make sure the inner Douglas barrel doesn't spin against the outer remaining stub of stock barrel. That can be solved a few ways, perhaps with a small woodruff key in a machined-in channel.

The forward muzzle nut will also double as a gas-tap chamber and a front sight base.
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Old May 29, 2012, 06:53 PM   #2
Newton24b
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ive never read or heard of anyone with a revolver chambered in 9mm complaining about any accuracy issues resulting from a long chamber throat due to short cartridge in long cylinder.

if you dont want to machine the existing barrel out while its in the frame, pull it out and center it in a lathe, and just have them pull out a set of end mill bits and just take some time and slowly ream it out to the correct diameter for the .57 barrel section.

and to just hold the new barrel in place, you can try to do the standard sw method of the 1930s, thread the new barrel exterior, thread the inside of the old barrel, insert new barrel. and PIN the new section in.
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Old May 29, 2012, 10:09 PM   #3
Jim March
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Quote:
ive never read or heard of anyone with a revolver chambered in 9mm complaining about any accuracy issues resulting from a long chamber throat due to short cartridge in long cylinder.
Well I like the idea of lightening the cylinder. I'll also get an extra half inch or so of barrel length for a given gun length.

And no, I haven't decided on a final barrel length yet. 5" is most likely...but I might go the whole 6.5" length. That would give me some velocity back lost with the 9mm conversion. Remember, this won't be as heavy per inch of barrel as a stock 357 setup, because there'll be a significant air gap between the inner core and the outer shroud tube.

I'm pondering what to do with that shroud tube. Ventilate it like a tommy gun heat shroud? Use it as a sight system mount? Hell, mounting a picatinny rail to it would be easy. Or two, top and bottom?



I keep pondering the question "what would cause the most chaotic possible freakout at a SASS loading and gun inspection table"?



This Douglas barrel should shoot fast for it's length, I hope?

Quote:
if you dont want to machine the existing barrel out while its in the frame, pull it out and center it in a lathe, and just have them pull out a set of end mill bits and just take some time and slowly ream it out to the correct diameter for the .57 barrel section.
That's my plan, my man.

Quote:
and to just hold the new barrel in place, you can try to do the standard sw method of the 1930s, thread the new barrel exterior, thread the inside of the old barrel, insert new barrel. and PIN the new section in.
Don't need anything that complex. I'll put a slight negative and positive taper in the area where the back of the original barrel is. That way as the barrel is "pulled" towards the muzzle by the muzzle cap-screw, it will auto-center. At that point it won't take much to prevent inner barrel rotation. A matching pair of dimples and a small ball bearing is one obvious answer. A woodruff key in a pair of milled slots is another. Easier than two new sets of threads, that's for sure.
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Old May 29, 2012, 10:11 PM   #4
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Quote:
ive never read or heard of anyone with a revolver chambered in 9mm complaining about any accuracy issues resulting from a long chamber throat due to short cartridge in long cylinder.
One other thing on this point: it can't be a good idea to have the bullet hit the throat and forcing cone AFTER travelling half an inch and building up a respectable head of steam. By shortening the cylinder the lifespan at those two points ought to increase?
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Old May 30, 2012, 03:14 PM   #5
Bill Akins
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Quote:
Jim March wrote:
One other thing on this point: it can't be a good idea to have the bullet hit the throat and forcing cone AFTER travelling half an inch and building up a respectable head of steam. By shortening the cylinder the lifespan at those two points ought to increase?
Have you looked at the distance the projectile has to travel from the cylinder to the forcing cone of a .45 acp S&W model 1917 or model 25 revolver? That's at least a half inch maybe a tad more. They didn't have any problems.


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Old June 6, 2012, 09:23 PM   #6
Jim March
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Have you looked at the distance the projectile has to travel from the cylinder to the forcing cone of a .45 acp S&W model 1917 or model 25 revolver? That's at least a half inch maybe a tad more. They didn't have any problems.
The 45ACP is a pretty slow round. I'll be shooting 9mm+P+. That speed difference WILL be an issue...
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Old June 6, 2012, 10:35 PM   #7
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Plan B... man that's just out there. Logically it seems like the way to go in terms of leading, but inherently it just feels wrong.

Here's the thing with plan B... you're relying on that tiny cylinder remaining rotationally true round after round even though no matter how tight you try mate the active cylinder and the barrel you're bound to get some push on the frame or the axle or somewhere. As soon as it starts getting a little more push on the top or bottom (or the left or right for that matter...) of the tail end of that barrel I honestly belive that it will quickly work things out of true and your accuracy will plummet geometrically or at least logorithmically.

So, I like Plan A in the long term but Plan B in the short term for accuracy. Theoretically Plan B should be more accurate. If the bullet enters the barrel at a straighter angle then it should spin truer and therefore 'pushing' or 'favoring' as opposed to if it's already built up some momentum and leads when it hits the barrel.

Just an opinion from a guy who's taken University Physics and fired off a few tens of thousands of 7.62 NATO out of an M240 a few hundred 120mm and a few dozen 155mm Howitzer rounds.

Then again... a super-light cylinder? Hell, Plan B is just so interesting....

---------------

Last edited by CarbineWilliams; June 6, 2012 at 10:53 PM.
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Old June 6, 2012, 10:53 PM   #8
Jim March
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Well...remember, with Plan B the "core" of the cylinder is intact, surrounding the base pin in the normal fashion. The base pin will be a Belt Mountain affair set-screwed to the barrel by the way, for max rigidity.

Second, remember this is a BEEFY gun through and through for a 9mm. This thing started life as a 357 sure but it's the same frame size as the 45LC version. And 357 specimens like mine have been successfully re-chambered and re-barreled to 41Magnum, or 44Mag as a five-shot with no issues. The cylinder wall thicknesses in 357 are just crazy - much thicker and wider in every direction than a Ruger GP100 or S&W686, neither of which are noted as being "delicate".

So...yeah, I get what you're saying about flex and all but...this thing is going to be massive overkill in every direction as a 9mm.
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Old June 6, 2012, 10:55 PM   #9
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I'm really starting to like your plan B, just cause I've never seen it explored and the lightened cylinder and it is 9mm out of a 357 frame with relatively overstrength parts...

I'd like to know a little more about the forces at work. The case has to get shoved back against the back of the frame, but does any of the explosion travel back through the cylinder around the round casing under normal conditions? If so, would that end up pushing the cylinder forward (when the gasses hit the rim)? That may create a self-sealing effect :-)

I just fired my SRH .454 for the first time tonight, and I noticed that there was a lot of carbon between the extractor and loading end of the cylinder, as well as against the back of the frame. This may be an extreme case, but maybe it tells us something about the general flow of gasses in a revolver.

Last edited by CarbineWilliams; June 6, 2012 at 11:05 PM.
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Old June 6, 2012, 11:52 PM   #10
Jim March
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Well the brass shell is supposed to expand in the chamber and form a gas seal.

The cleaner the chamber (smoother walls) the better the seal. And I'll have something else going on in my favor...actually, several things:

1) 9mmPara is a fairly small case using a small charge of fast-burn powder. This *should* result in less soot overall...that sort of charge tends to burn pretty clean. In comparison, a 454 uses a bigger charge of slow-burn powder, which tends to be "sootier".

2) I'll be headspacing on the rim, which means rather than being smooth all the way through like a 357, 454, etc. I'll have a "step" in the cylinder wall that the forward edge of the rim will hit. This is cut by any standard 9mm chamber reamer. 45ACP, 40S&W and the like all work the same way. This *should* provide a better gas-seal for powder going backwards.

Put another way: to get past the shell gas has to go out (sideways) and then make a 90deg. turn to go backwards. With a 454 the path is straight back. Follow?

So, it should be a very easily cleaned beastie .
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Old June 8, 2012, 11:11 PM   #11
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Yup. Makes perfect sense.

I can't wait to see pictures when you get done.
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Old June 13, 2012, 09:44 PM   #12
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In comparison, a 454 uses a bigger charge of slow-burn powder, which tends to be "sootier".

I'll tell you, I went back to range tonight and shot nothing but .454. Virtually no carbon on the frame wall behind the cylinder or the back of the cylinder. Not sure whether this is due to the .45 Colt cases not expanding as much and therefore letting more gas go past, or if its the Slip 2000 I cleaned the pistol with after shooting them. Remember that .454 uses a rifle primer and very high pressures. I think it's the .45 Colts that were making it so dirty. Any thoughts?

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Old June 14, 2012, 12:38 AM   #13
Jim March
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454 at higher pressure might very well seal better than 45LC. Depends somewhat on how tight the chambers are...really clean, sweet, smooth and tight chambers in 45LC can be a dream and one reason why people pay big bucks for really high-end guns from Linebaugh, Stroh, Bowen, etc.
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Old June 15, 2012, 05:47 PM   #14
CarbineWilliams
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One interesting thing is that I fired 36 rds. of BVAC reloads, and had no problem ejecting them... then I fired one cylinder's worth of Hornady XTP 240 gr that were a lot higher energy and all of those were well stuck in the chamber. So I guess those cases are actually expanding that much? Is that normal?
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Old June 15, 2012, 11:36 PM   #15
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Jim. You guys. You really shouldn't be playing with guns. You oughta be at NASA. Seriously.
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Old June 16, 2012, 02:01 PM   #16
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Lol. Yeah, I do love some physics and engineering juxtaposed with shooting stuff.
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Old June 19, 2012, 10:53 AM   #17
Jim March
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We're on the 3rd page now...

http://thefiringline.com/forums/showthread.php?t=493319
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