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Cracked Bolts, Slides and Receivers |
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sleeplessnashadow
Admin Group Joined: Nov 09 2015 Location: SoCal Status: Offline Points: 1150 |
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Posted: Sep 22 2018 at 7:46am |
Up front, the question I am about to ask your input on is not the carbines manufactured by Universal Firearms. So please, no negative opinions about Universal's carbines.
(Click on any of the following pics to see the full size version) Many of us have seen or experienced a broken GI bolt where the right lug cracked or snapped off along the path of least resistance such as the one shown below. The example below is a bolt manufactured by National Postal Meter. The bolt above is a bolt I own. I was present when the lug snapped off. The carbine was an Underwood with all GI parts in very nice condition. For a used firearm. Some of us believe one cause for this breakage is a burr or something in the path of the left bolt lug that impedes it's movement forward and/or back. A momentary delay with the left bolt lug exerts more force on the right bolt lug from the slide. Examining the path of the left bolt lug in the Underwood carbine revealed a small metal burr in the channel the left lug travels in. Experiments with another bolt confirmed the burr was slightly impeding the movement of the bolt. Not enough to break the right lug immediately. But enough that over time the extra pressure on the right bolt lug from the slide caused it to snap off. From about 1964 thru 1984 Universal Firearms carbines were drilled and tapped for a side scope mount. The side scope mount was designed and manufactured for the .30 caliber carbines by Weaver and existed before Universal Firearms. It has been available for use on, and used by owners of, any .30 caliber carbine. Both commercial and GI. There have been a number of other side scope mounts for the carbines that have required drilling and tapping the left side of the receiver. Some, like the Weaver mount, required the holes to be drilled where they would extend into the path of the left bolt lug. The example below is a Weaver side mount on a late Universal Firearms receiver. I used cross illumination to make the screws visually stand out. That improper hardening of the bolt, slide and/or receiver can cause the breakage shown below is a recognized fact. Set this aside for this discussion as there may be more than one cause. Universal used the open cam design from s/n 100,000 through end of production at over s/n 480,000. I have yet to see (just me with my experiences) a bolt used with this open cam cut have the right bolt lug snap off. What I have seen is a number of slides that have cracked extending into or out of this open cam cut as shown below. (NOTE: The slide depicted above was made for and sold by Numrich Gun Parts, not Universal Firearms) What I'm wondering is if any impediment to the movement of the left bolt lug over time would cause the slide with the open cam cut to crack instead of the right bolt lug. The pics below are for reference on the forward and rearward points of impact of the right bolt lug to the open cam cut. (yes, there's a crack in the receiver. The receiver tested at RC 42 on two tests and RC 44 on a third with a Rockwell Hardness Tester. I have a spring tube Winchester receiver with a crack in the same location.) I figured this was a good post for the general discussion forum instead of the commercial carbine sub forum given the issue with the side scope mounts and any impediment to the left bolt lug is relative to all .30 caliber carbines. Your input relative to impediment to the left bolt lug causing these slides to crack is much appreciated. Thank you Jim Edited by Lupus Dei - Sep 29 2018 at 11:08am |
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Charles
Grunt Joined: Mar 21 2016 Location: Maryland Status: Offline Points: 587 |
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A lot of good theories but I must mention an experience I had recently. After a thorough cleaning and before oiling, the slide and bolt refused to move rearward to test function, but after oiling the lugs, it cycled smooth as silk. That leads me to believe the true purpose of the oilier is to oil the lugs on the bolt. If the gun had been fired in that state, I'm sure I'd have had a broken lug or worse.
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Charles
Co B 1st Batl.115 Inf. Reg. 29th. Divi. 4.2 Heavy Mortar Co Retired Life member NRA |
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jackp1028
Hard Corps Joined: Jan 01 2016 Location: Cloudcroft, NM Status: Offline Points: 1276 |
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Jim, it is obvious that in your first picture, the scope base screws are protruding into the left bolt lug channel, potentially blocking the bolt. Not good! Even if these screws were shorter and could not possibly contact the bolt lug, the uneven surface around them could trap dirt and debris possibly causing a blockage anyway. As we discussed in our previous correspondence, that may have contributed to the bolt breakage in my Universal along with excessive wear of the piston stop allowing greater than normal forces on to be imparted on all the interconnecting parts (slide,bolt, piston block).
Again, obviously lubrication will lessen the effect of any bolt resistance. Another factor will be the round count. The more times that bolts and slides are exposed to the shock of firing the more they are likely to develop cracks that lead to failure. An area of particular susceptibility will be where there are internal corners such as the web of the bolt or the sharp corner of the slide cam. These locations, called tensors, are more likely to fail due to metal fatigue. This is why engineers try to avoid this in design by specifying radiused corners instead of sharp corners where possible. Thus the difference between Type 3 and Type 4 slides. These causes are in addition to failures due to improper heat treating, abuse (hand loads), and wear over time. Note: Regarding your NPM bolt, I have seen traffic on this and other forums commenting on the seemingly higher rate of failure of this specific (N-14) part. |
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JackP
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RClark9595
On Point Joined: Oct 30 2017 Location: WVC Utah Status: Offline Points: 136 |
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I have a late Universal that I mounted the Weaver side scope mount on, (my eyes aren't what they used to be), so I felt I needed a scope. When I took The rifle to the range, the bolt seemed to have some drag on it. I hadn't fired the rifle in some time so I didn't pay much attention to it.
The rifle has a new bolt, aftermarket high grade steel slide and I replaced the trigger housing group. I took it to a gun smith to have it inspected head space and everything else. When I came to pick it up he told me the scope mount screws were too long and he had to grind the ends down so they wouldn't interfere with the bolt. I've sense learned that the mounting bolts that come with the mount have to have the ends ground down by at least 0.02" to clear the bolt. This is not in the instructions you get with the mount. Also, the rifle's recoil acts as a great loosening wrench on these bolts, after just a few rounds these bolts are completely loose, and the scope is flopping from side to side. Best to apply Loctite 721 red thread locker on the treads then install the bolts and tighten, then let it set. JIM, Is there any chance we could get a better look at that crack in the receiver?Thanks. |
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Ron
USAF 4535 CCTS F4 Combat Crew Training Vietnam era Vet. |
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meckanic
Recruit Joined: Nov 30 2017 Location: Chicago Status: Offline Points: 21 |
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Let me know if you want to dump that broken bolt. Thanks.
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sleeplessnashadow
Admin Group Joined: Nov 09 2015 Location: SoCal Status: Offline Points: 1150 |
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sleeplessnashadow
Admin Group Joined: Nov 09 2015 Location: SoCal Status: Offline Points: 1150 |
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For comparison given this location is a fairly common one IF a .30 caliber receiver is going to crack. This is a Winchester receiver. It has a spring tube for the recoil spring instead of the deep hole for the recoil spring.
The deep hole for the recoil spring required a particular machine for this purpose as even the slightest misalignment could cause the drill bit to exit the side or bottom of the receiver towards the end of drilling the hole. This example is a commercial receiver. Commercial manufacturers have encountered the same problem with drilling the deep hole for the recoil spring. This was an acceptable way of making receivers with all made by Quality Hardware having this design. Winchester used this method to recover receivers that had been scrapped due to the hole being drilled improperly. But Winchester preferred the deep hole over the spring tube because the spring tube design weakened the receiver in the opening for the right bolt lug. The majority of the receivers with the spring tube design have not cracked. The crack tends to happen when the normal pressure placed on the receiver in the opening for the right bolt lug is exceeded significantly. This can also crack receivers with the deep hole for the recoil spring. Causes can include but are not limited too improperly reloaded ammunition and/or improper headspace. I'm not an authority on this so feel free to share your experiences. This receiver was purchased knowing it was cracked with a reduction in cost due to the crack. Click on a photo to view the full size image. |
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RClark9595
On Point Joined: Oct 30 2017 Location: WVC Utah Status: Offline Points: 136 |
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Thanks, Jim
That's a whole new failure I was unaware of, knowledge is a wonderful thing, now I have something else to watch out for, is it a very common break Jim, this is the first one I've ever seen? You say you bought it this way knowing it was cracked, was the seller saying this was still serviceable, or just charging you for junk? That's really none of my business, but I sure wouldn't want to bay one already cracked. Edited by RClark9595 - Sep 30 2018 at 6:27am |
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Ron
USAF 4535 CCTS F4 Combat Crew Training Vietnam era Vet. |
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sleeplessnashadow
Admin Group Joined: Nov 09 2015 Location: SoCal Status: Offline Points: 1150 |
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If a .30 caliber carbine receiver is going to crack there are a few locations that it happens fairly consistently. What causes them to crack in these locations is also fairly consistent.
The location above along the rear of the opening for the right bolt lug is one of them. Can happen to either a spring tube receiver or a deep hole receiver. Some of the spring tube receivers the slide stop hole goes all the way through as with the Winchester above. A crack running from side to side occasionally happens. I don't have a good pic of the other location. Hopefully someone will add a few. Forcing the trigger housing in and/or out of the two lugs on the bottom of the receiver at the rear without supporting them can crack either lug but usually the one on the left as the one on the right has more support. Jim |
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sleeplessnashadow
Admin Group Joined: Nov 09 2015 Location: SoCal Status: Offline Points: 1150 |
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The photo below isn't mine. I saved it as a good example.
This was a GI carbine. The receiver was made by S.G. This can happen to any .30 caliber carbine, GI or commercial. There are a couple things that can cause it with improper headspace being one of the more common. Over powered reloads is another. Note the cracked right bolt lug, the bulging of the receiver to the right of the right bolt lug and to the left of the left bolt lug. Notice the slide is not in the pic. This catastrophic failure can cause the slide handle to separate along the arm to the main body. This is why checking the headspace of a well used carbine, GI and commercial, is so important. This kind of failure can cause serious injuries. Click on the photo to see the full size image No, this cannot be repaired. Anyone who tries to repair this, and some do, is risking serious injury when it's fired afterwards. May not happen the first range trip so don't think it was a successful repair. It can be a heart breaker to have to scrap the most expensive parts of the carbine when this happens but it's not as expensive as an emergency room visit, hospital admission or the loss of an eye or worse. |
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manteo97
On Point Joined: Jan 15 2016 Location: Victoria, B.C. Status: Offline Points: 61 |
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I think that S.G. is one a customer brought to me to "fix". This was the second bolt that it had cracked. It had been re-barrelled, but I measured the headspace at 0.050" over the NO-GO dimension, ie it swallowed the NO-GO gauge. The chamber was way over-reamed. Ammo was factory load. Result was it had to be be de-activated, and is now a wall decoration. It was unfortunate, as it was the customer's father's all matching S.G. bring-back from WW II.
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sleeplessnashadow
Admin Group Joined: Nov 09 2015 Location: SoCal Status: Offline Points: 1150 |
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Good questions. What follows below is not all inclusive and perhaps those with gunsmith experience will chime in and add what I miss. I'm not a gunsmith. First, the word "common" isn't something that applies to cracked .30 caliber carbine receivers, bolts or slides. Especially not those made under contract to Ordnance during and after WWII. "Common" applies to where a crack or break has been found IF one exists. Most cracks and breaks are related to poor maintenance over time that should include checking the headspace occasionally the older it gets, make sure the gas piston is tight and secure and checking for wear to the metal surfaces listed below. This applies to both GI and commercial carbines. Every part has a lifespan and with repeated use over time it's wise to periodically check them. More frequently with commercial carbines and their parts but not less frequently with GI carbines and GI parts.
Commercial carbines need to be checked sooner and more often as their parts generally don't have the lifespan of their GI counterparts. Especially when buying a used one. I need to add here that reloads, especially when done by a mass reloading op like with ranges, need to be avoided. It only takes one screw up to destroy a carbine. Also, avoid use of Russian ammo that has a steel casing. The carbine extractors were not and still are not made to withstand steel casings. My experience with commercial carbines has been the research work I've continually kept doing for the commercial carbine website by buying, inspecting, learning, photographing, safety checks, firing then reselling to get another to do the same. If unsafe I scrap the unsafe part(s). Again, I'm not a gunsmith. Just have some experience with what can go wrong over time. My GI carbine experience also comes from the research I've done and do. Always more to learn. The Winchester receiver shown above was for sale by itself as a cracked Winchester spring tube receiver. I didn't buy it to fix or shoot. It's reference material. Had seen others, commercial and GI, crack in that location. I've maybe seen more than most because of the learning I do. This has been full time plus double time often for 12 years. Kids are grown, I'm retired and divorced, live by myself. The Universal receiver above was part of a Universal carbine I bought that had no mention of the crack. Even with the stock removed the crack wasn't a stand out and easily missed. When I shoot the photos I use the lighting and angles to make it obvious. I knew the fella I bought it from. I'm convinced he didn't know. The difference with me and most others is I consider it another learning opportunity and reference material. Having bought and sold so many commercial carbines they taught me what to look for on all carbines. I don't collect them. I have my one shooter I built. Only keeper was a Universal Vulcan is .44 magnum. As a shooter. I have 14 GI carbines left as reference material. Haven't shot any of them but they're safe to shoot. In the next year I'll be selling most if not all. Majority are "Bavarians" used in Austria, Bavaria and Wurttemberg-Baden. I have a set of all the Bavaria markings bought one at a time. I gotta get back on my infrared work so hope others will jump in here and answer questions. If I can find a pic of a broken receiver lug from forcing the trigger housing on and off the receiver I'll post it here. Ditto a cracked spring tube receiver with the crack at the slide pin hole. Jim |
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meckanic
Recruit Joined: Nov 30 2017 Location: Chicago Status: Offline Points: 21 |
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The crack in the receiver was caused by rotational forces (torsional or twisting) It is possible the angle cut in the receiver (right side looking back to front) is not deep enough to allow the lug to set properly when in battery. Repeated slamming of the bolt downward caused by the cam of the slide could have made this area weakened and also recoil forces acting on the lug may have added to the cracking.
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tenOCEE
Hard Corps Knows rear sights! Joined: Jan 01 2016 Location: East Tenn Status: Offline Points: 1330 |
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I have no idea what caused this. I have no knowledge of who it happened to. It's a 416766 serialed Universal receiver and was in excellent condition with very little wear. This is one of two Universals witnessed in one day with similarly grenaded condition. The other was presented for my opinions by the person who stated it blew up on him while firing. |
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manteo97
On Point Joined: Jan 15 2016 Location: Victoria, B.C. Status: Offline Points: 61 |
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Without using an NDT method to further investigate (like dye penetrant which is fairly cheap & easy to do) this looks to me like a defect in the the steel. Split runs in the direction of the forged grain structure. Possibly a non-metallic inclusion in the original 4140 steel forging.
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tenOCEE
Hard Corps Knows rear sights! Joined: Jan 01 2016 Location: East Tenn Status: Offline Points: 1330 |
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Could be. But that's gotta be a natural breaking point being the location where the receiver is at it's thinnest point running the slide cutout into the upper rail. The crack runs in the natural structure of the upper slide cutout opening corner. I don't have good equipment for photos. This is binoculars and a $14 pawn shop camera. |
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tenOCEE
Hard Corps Knows rear sights! Joined: Jan 01 2016 Location: East Tenn Status: Offline Points: 1330 |
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Per Jim's request I tipped the receiver on it's left upper corner and poured some oil into the bulged slide cut overnight. The oil DID migrate through that crack from the slide cutout to the top of the receiver showing it's cracked through. The crack and right around it is moistened with oil. See the yellow arrows. PERHAPS an indication of one event. Note that the screw hole is in between there and bluing was applied after all work. The shiny portions on each side of the hole are high spots and there appears to have POSSIBLY been an event there? See them again in pic #4 side on view. There is no bur on the left lug locking point as I've seen with other damaged receivers. The divot between the shiny points is NOT part of the event. It's a remnant of the hole drilled through and is still blued. |
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tenOCEE
Hard Corps Knows rear sights! Joined: Jan 01 2016 Location: East Tenn Status: Offline Points: 1330 |
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If everyone could please look at this location on any Universal you encounter for cracking in a similar way I'm positive it will be helpful to those doing the research. Please note the serial number and submit it to aid in this, too. This is probably specific to certain blocks. Here's a second cracked Universal spotted in our small city, so this ought to support the problems discussed in a previous thread. Was at a show yesterday and saw a Universal on a table cracked exactly as the receiver I own. The seller had $400 priced on a tag. After I showed him it was cracked and described that the slide and bolt are subject to flying out during shooting he lowered the price to $350 if anyone is interested in adding an additional thrill to their shooting day. The day I bought my cracked one I saw another one, but I'm not sure that this is the one. On that day a year or so ago the owner of that one told me on his 3rd shot ever that the gun grenaded in his hands/face and that parts actually contacted his face. Yesterday when this one was spotted the seller thankfully was agreeable to a couple of quick shots, so here they are for your consideration. Note the serials of each. Mine is 416766. This one has much more wear than mine and serial is 415948. And the two cracked Universals side by side just in case. |
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RClark9595
On Point Joined: Oct 30 2017 Location: WVC Utah Status: Offline Points: 136 |
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I own Universal Ser. # 486914 with a scope, and it has been fired a lot, enough to wear out the magazine well and required a new trigger housing. The rifle has been thoroughly inspected by a licensed gun smith, and since the posting of this thread and one other, I have inspected my receiver with a lot of scrutiny. I think it's safe to say that my gun has no cracks.
I think the idea that the cracks may be limited to a group, or manufacturing run of receivers that may be less than the best quality, is possible. It might be the impossible dream, but it would be nice if we could collect a data base of serial numbers that have been found with cracks or defects. I'll lend mine as one of the good ones, anyone else have any ideas?
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Ron
USAF 4535 CCTS F4 Combat Crew Training Vietnam era Vet. |
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sleeplessnashadow
Admin Group Joined: Nov 09 2015 Location: SoCal Status: Offline Points: 1150 |
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I've been collecting serial numbers along with markings present, parts present, design features, and noting which are known to have had problems. For Universal and a number of other commercial manufactures since 2006.
Where I've collected them from has been many different places to include the survey form I have specific to Universal Firearms carbines. Below I've listed the ones I have, divided into blocks of 10,000 serial numbers from start to finish. This is not how I index them, just how they are presented here. I do not have a complete assessment of each carbine. Data mining is a matter of get whatever info I've been able to obtain. However, if a carbine is known to have had an issue worth noting I have indicated the details along with the other info I have. I do not identify carbines as having had no problems for a number of legitimate reasons. By default, if I have no problem listed ten the carbine isn't a known problem. Which can change with each and every one of them. If that happens it's so noted. Here's Universal Firearms Vulcan 20 w/ s/n's from 1014 - 4357 X prefix .30 cal. carbines 12 w/ s/n's X035 - X623 Commemoratives 3 w/ s/n's 00204 - 000430 .30 cal carbines lowest - 9999 31 w/ s/n's 2054 - 9678 10,000 - 19,999 43 w/ s/n's 11,137 - 19,975 20,000 - 29,999 31 w/ s/n's 21,456 - 28,691 30,000 - 39,999 36 w/ s/n's 30,011 - 39,4xx 40,000 - 49,999 31 w/ s/n's 40,340 - 49,488 50,000 - 59,999 12 w/ s/n's 50,119 - 57,541 60,000 - 69,999 13 w/ s/n's 63,939 - 69,562 70,000 - 79,999 28 w/ s/n's 70,4xx - 79,911 80,000 - 89,999 53 w/ s/n's 80,0xx - 89,998 90,000 - 99,999 25 w/ s/n's 90,026 - 97,286 Hybrid .30 cal carbines 100,000 - 109.999 19 w/ s/n's 100,001 - 109,9xx 110,000 - 119.999 22 w/ s/n's 111,0xx - 119,411 120,000 - 129.999 23 w/ s/n's 121,157 - 129,902 130,000 - 139,999 19 w/ s/n's 130,986 - 139,8xx 140,000 - 149,999 19 w/ s/n's 140,287 - 149,2xx 150,000 - 159,999 8 w/ s/n's 151,833 - 157,818 160,000 - 169,999 15 w/ s/n's 160,0xx - 169,3xx 170,000 - 179,999 18 w/ s/n's 171,238 - 179,907 180,000 - 189,999 16 w/ s/n's 180,195 - 189,273 190,000 - 199,999 14 w/ s/n's 190,224 - 199,503 200,000 - 209,999 18 w/ s/n's 200,3xx - 199,503 210,000 - 219,999 19 w/ s/n's 212,047 - 219,906 220,000 - 229,999 4 w/ s/n's 220,5xx - 222,440 Seiderman purchased company and jumped to s/n 300,000 to separate his from the prior investors 300,000 - 309,999 11 w/ s/n's 300,859 - 309,708 310,000 - 319,999 11 w/ s/n's 310,593 - 319,641 320,000 - 329,999 13 w/ s/n's 320,471 - 329,98x 330,000 - 339,999 13 w/ s/n's 330,0xx - 338,780 340,000 - 349,999 16 w/ s/n's 340,988 - 349,2xx 350,000 - 359,999 8 w/ s/n's 350,2xx - 357,016 360,000 - 369,999 13 w/ s/n's 360,963 - 368,3xx 370,000 - 379,999 15 w/ s/n's 370,421 - 377,494 380,000 - 389,999 17 w/ s/n's 380,2xx - 389,946 390,000 - 399,999 14 w/ s/n's 390,541 - 399,633 400,000 - 409,999 14 w/ s/n's 400,628 - 409,611 410,000 - 419,999 16 w/ s/n's 410,1xx - 418,8xx 420,000 - 429,999 10 w/ s/n's 420,256 - 429,853 430,000 - 439,999 16 w/ s/n's 430,0xx - 439,897 440,000 - 449,999 13 w/ s/n's 440,003 - 449,023 450,000 - 459,999 13 w/ s/n's 452,1xx - 459,9xx 460,000 - 469,999 11 w/ s/n's 461,xxx - 468,6xx 470,000 - 479,999 19 w/ s/n's 470,9xx - 478,715 480,000 - to last at Hialeah, FL 2 w/ s/n's 480,0xx - 480,985 Start at Jacksonville, AR start - 489,999 25 w/ s/n's 482,143 - 488,633 Stainless Steel - all Hialeah, FL 3 w/ sn's S01120 - S01525 5 w/ s/n's SS2071 - SS3467 Given the unknowns involved in why a carbine had a significant issue I do not consider 1 reported carbine amongst many as a problem with all carbines in the vicinity of that serial number or a problem with the manufacturer. I keep track of each one and look for patterns. The two patterns that have made themselves known with carbines made by Universal have been: 165,165 - 179,907 there have been 4 carbines out of the 23 I have info on that have consistently had problems related to improper hardening of the barrel. To include damage to the barrel caused by the gas piston and/or separation of the gas piston housing. 415,948 - 416,766 there are two shown on this thread with a third reported as seen, of the 6 I have info on, that the receiver has cracked lengthwise along the top of the right side of the receiver adjacent the slide path. While I have heard and read many people say carbines by Universal were/are a problem, they saw a Universal with a problem, they heard of a Universal with a problem, etc. etc. I don't record 2nd hand or farther out information. Rumors are in no short supply on the internet. In addition to many of the problems reported have not been able to be attributed to a problem with the manufacture of the carbine. The two biggest complaints about every carbine usually involves the magazine or the carbine needs to be cleaned thoroughly. With the most dangerous problem being improper headspace, inherent with every centerfire semi-auto rifle and not just carbines. While this post is specific to Universal they were not the only commercial carbine manufacturer to encounter problems off and on over the years they were in business. Jim |
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