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Barrel Skirt

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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Topic: Barrel Skirt
    Posted: Jun 18 2017 at 6:45am
I understand the barrel skirt was designed to assist chambering and bolt alignment. I have two commercial carbines that don't wear the skirt and both of them feed-n-function just as well as my GI carbines. Was the skirt a case of over-design (on purpose), or does it serve some other function?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sling00 Quote  Post ReplyReply Direct Link To This Post Posted: Jun 18 2017 at 7:28am
In addition to what you stated it also supports extraction of fired cartridges.  Kuhnhausen’s Shop Manual states the skirt had two purposes: [1] to help axially align the front of the bolt as it closes and locks; and [2] to support the front of the bolt as the bolt begins to unlock and break fired cartridge case friction in preparation of case extraction. 

As to if it is really needed who knows?  I would think military service use rifles would have a touch of "extra" design over commercial. 

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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 18 2017 at 8:35am
That answers my question and obviously the weapon will function without the skirt. One would expect the commercial manufacturers to shortcut where they could and ordinance to over-build a weapon-of-war where they thought it was necessary.
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SWANEEDMB View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SWANEEDMB Quote  Post ReplyReply Direct Link To This Post Posted: Jun 18 2017 at 1:27pm
This post is what we needed to see. Somewhere we read/seen where the barrel skirt was indeed an alignment for the bolt. We have a converted carbine, 5.7 mmj (Spitfire),  barrel only,  mated up to a Winchester receiver, barrel made by Millville Ord Co. (MOCO). It has no skirt, with an empty chamber the bolt face is very sloppy, shooting it we get a  lot of light primer strikes, am thinking if it had a skirt that would not be happening. Guess we'll just have to put up with it as is, am sure their is no fix. Too bad too, fun little cartridge.
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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 18 2017 at 2:05pm
One of my commercials is an IJ 9MM utilizing a modified cal-30 bolt which has no skirt and feeds-n-functions very reliably. My other commercial is a Gen-1 Universal full of GI parts including a Winchester flat bolt, which has no skirt as well. This was part of the reason I wanted to ask about the skirt. Both of my guns that wear no skirt work wonderfully without it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sling00 Quote  Post ReplyReply Direct Link To This Post Posted: Jun 19 2017 at 10:25am
I have no experience with commercial carbines and was wondering, other than what was discussed here, are commercial carbines made identically to the USGI model such that parts are interchangeable?  Or are they made with a general appearance but significant differences in operation? 
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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 19 2017 at 11:40am
Well...it depends. Most all of the "early" commercial manufacturers utilized USGI components for as long as they lasted. The jury seems to be still out on some of the more recent entries into the market as to what is interchangeable and what's not. The Plainfield, Iver Johnson and several other examples remained true to the USGI design until they one-by-one went out of business. These early manufacturers built (or subcontracted) replacement parts that were (or close enough) to USGI specifications that they were 100% compatible. Many of these parts were cast steel and in some cast aluminum, in particular trigger housings. Universal stayed around the longest and produced over 450,000 carbines. They are categorized in generations. The early  generation 1's are practically 100% interchangeable. The percentage begins to become less-and-less as serial numbers increase and things went off a cliff beginning around serial number 95xxx-or-so with design changes that eventually relegated the gun to something only that would shoot caliber-30 and only resembled a USGI carbine. You can generally detect a USGI compatible gun by observation of the trigger housing and the slide. Generally speaking, if these look USGI...the internals are USGI compatible. You really need a Universal in your hands for closer examination to determine what's inside. The Plainfield's, Iver Johnson's and the like need no examination. They went out of business B4 they got creative and reinvented the gun.

Good read and research at  uscarbinecal30.com and select Commercial Carbines.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sling00 Quote  Post ReplyReply Direct Link To This Post Posted: Jun 19 2017 at 12:23pm
Thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote manteo97 Quote  Post ReplyReply Direct Link To This Post Posted: Jun 19 2017 at 3:45pm
I'm not sure why the barrel skirt was part of the original barrel design for USGI M1 carbines, but yes it does serve as a guide for the front of the bolt. There is an inside relief cut in a USGI receiver just behind the threads for the barrel skirt. Of course the early skirts were bigger than the later ones, where they were almost 1/2 of the circumference of the barrel threads.

Mid-WW II the size was reduced, citing damage to the skirt during shipping & handling. The skirt was a difficulty, and for the post-war commercial makers was eliminated. The relief cut for the barrel skirts on I-J & Plainfield receivers are not present, and this small area of the receiver served to function as the bolt guide.

I found this out the hard way when I first started making 19" barrels using stubs off commercial barrels (no skirt) and putting these on USGI receivers. I test fire all these barrels/receivers when done, but neglected to see what the effect of putting a loaded mag into the well and then pull back the slide. I always, up until then, pulled the slide back, then inserted the loaded mag, and let the slide go forward to chamber a round & shot 5 rounds....worked fine. However, a customer discovered if he kept the slide forward, put in a loaded mag, the upward pressure of the top round would force the bolt up putting it into a position were the bolt jammed when you attempted to pull the slide back! Hug up on the left lug.

So now, USGI receivers get USGI skirts, and I-J & Plainfields get no skirt on the 19" barrels.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sling00 Quote  Post ReplyReply Direct Link To This Post Posted: Jun 19 2017 at 4:09pm
First hand experience.  Can't beat that!

Thanks!  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 19 2017 at 5:09pm
Encouraging to hear that the commercial companies didn't just whack-off the skirt and actually may have had the foresight to modify (or leave alone) the receivers associated with the skirt-less barrels by not machining the relief-cut to serve the same purpose. I realize that manteo was not trying to be all encompassing, but I need to add that Universals are skirt-less as well. I don't have any experience with other commercials only the IJ, Plainfield and Universal gen-1.

Like I have noted....my commercials don't do a thing but shoot and shoot well without the skirt. Now I know the unmolested receiver serves to assist bolt alignment.

Good Stuff!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 19 2017 at 5:33pm
Originally posted by SWANEEDMB SWANEEDMB wrote:

This post is what we needed to see. Somewhere we read/seen where the barrel skirt was indeed an alignment for the bolt. We have a converted carbine, 5.7 mmj (Spitfire),  barrel only,  mated up to a Winchester receiver, barrel made by Millville Ord Co. (MOCO). It has no skirt, with an empty chamber the bolt face is very sloppy, shooting it we get a  lot of light primer strikes, am thinking if it had a skirt that would not be happening. Guess we'll just have to put up with it as is, am sure their is no fix. Too bad too, fun little cartridge.


SWANEE...pay close attention to manteo97's post above. If you have a skirt-less barrel in a USGI receiver, sounds like that could be part of your problem? I have no idea if (or the cost of) some sort of insert machined to fill the gap in the receiver where the skirt would have been is possible. Sounds like you have a perfect mismatch....no barrel-skirt and a receiver with the relief cut for one? I certainly would not be suggesting the destruction of a USGI receiver, but if a gen 1 Universal receiver could be found, that would work. It's forged steel, USGI compatible and has no relief cut for the skirt. Hey....it's only money.....Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SWANEEDMB Quote  Post ReplyReply Direct Link To This Post Posted: Jun 20 2017 at 12:23pm
Have been reading Kuhnhausen s-manual on the skirts, couple times but the lost brain cells won't let me really understand, but your right floydthecat, Manteo97 post makes real sense, must be the light primer hits problem, bolt just not seating properly. Well, think we just have another wall hanger, Have other nice carbines to play with. Or, just maybe will find another carbine barrel to replace the 5.7.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 20 2017 at 1:26pm
You seem to have one of those dreaded conundrums.....a Winchester USGI receiver with a very scarce barrel attached to it. It just doesn't make good sense to wreck the gun to make it work. As you say....you could replace the barrel with a caliber 30 and maybe sell the 5.7 barrel on it's own. I bet there is someone out there that would really want to convert a less expensive carbine to a 5.7.... you never know.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SWANEEDMB Quote  Post ReplyReply Direct Link To This Post Posted: Jun 20 2017 at 3:56pm
Originally posted by floydthecat floydthecat wrote:

You seem to have one of those dreaded conundrums.....a Winchester USGI receiver with a very scarce barrel attached to it. It just doesn't make good sense to wreck the gun to make it work. As you say....you could replace the barrel with a caliber 30 and maybe sell the 5.7 barrel on it's own. I bet there is someone out there that would really want to convert a less expensive carbine to a 5.7.... you never know.
 
I wouldn't / couldn't pass it along with the possibility of it that it could not work, we bought the carbine with that sort of understanding, as is--where is. I knew or at least thought I knew it was a 5.7 at the auction, others thought different BUT several did want it besides me, so, that did up the cost. Live and (hopefully) learn.
Have really enjoyed this post. Thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 20 2017 at 6:59pm
I'm pretty sure it was quite uncommon to use a USGI receiver for a 5.7 conversion and especially rare for it to be a Winchester. I was under the impression all those were made by the commercial manufacturers on their receivers, but I suppose anyone that had a barrel could do a conversion. That skirt-less barrel on a commercial receiver would likely be just fine. I get the drift that the gun was likely purchased because it had Winchester stamped on it.Big smile
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote New2brass Quote  Post ReplyReply Direct Link To This Post Posted: Jun 20 2017 at 8:30pm
Have you considered that in 1964 .30 carbine ammo was the problem, or maybe to make it more accurate.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 21 2017 at 7:28am
Now days, one wouldn't be wanting it for the cartridge itself. Not far down-the-road from 1964 came the 5.56x45. An AR, or a variety of other guns that shoot the 5.56/.223, can be picked-up now for chump-change and of course, ammo is plentiful, cheap and the round is much more powerful than the 5.7.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 21 2017 at 10:19am
I started this thread, so I guess I can muck-it-up. The subject-matter was barrel skirts. I don't want to belabor, or sing any praises for commercial carbines, but that's the very thing that prompted the thread...no barrel skirt.

I went and performed a closer examination of my carbines. Naturally, the GI's have the skirt. My Underwood happens to have a long shirt. Upon a closer look at my Iver Johnson in 9MM, I have discovered that it actually has a short skirt. IJ used surplus forged steel receivers from their buy-out of Universal and built 9MM guns on them...so I have a Universal forged steel mil-spec single-spring receiver on the IJ 9MM...which has a short skirt.

I examined my gen-1 Universal cal-30 and made sure it had no skirt, but the receiver has a gap where the skirt would nest. As previously mentioned, the gun functions flawlessly with the gap and no skirt. Maybe ALL of the Universal carbines were cut for the skirt, but the barrels are skirt-less. I have no issues at all with it including the way it acts when a loaded magazine is inserted with the bolt closed. It will rack-n-load a fresh round.

This "rambling" is for the benefit of SWANEE. Maybe your 5.7 has other issues besides a missing barrel-skirt? With the bolt closed on an empty chamber and the hammer cocked, there is some mush in the bolt. That may be normal and you may not have a wall-hanger, just something that needs fixing concerning light-strikes?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SWANEEDMB Quote  Post ReplyReply Direct Link To This Post Posted: Sep 29 2017 at 6:25pm
New to me, a unused IAI 5.7mmj barrel hopefully to exchange with the one on my 5.7mmj, this barrel is skirted, relined, am sure this barrel was made by Green Mountain Rifle barrel Co. of Conway, N.H. machined by SMI-MA Inc. Worchester, Ma. Barrel matches up with one pictured I the 'U.S. Carbine Cal. 30 under Commercially Mfg. M-1 carbines.
We have done a 'plunk' test with our ammo and it seems like it matches with the skirt as far as the chamber is proper, am sure it is not short chambered.
Is anyone here had any experience with these barrels and any pros or cons you might share with us. Have read some NOT very good reviews on IAI carbines but do believe all were on the finished product and not the barrel.
Have spent quite a few hours researching on barrel exchange, have found some real good info here, had a concern tho that their was not a witness mark on the barrel but seems that is OK cause they were not all properly marked.
Just can't give up on this project.
As always---Thanks for any and all the help we can get.
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