What to do with 3rd Gen Universal M1 Carbine

[DrAndrew47]

Hi Everyone,

First post. My father bought a 3rd Gen (serial# 28X,XXX) in the late 70's and it's had just a few rounds through it in the last ~10 years. I fired it ~10 years ago and it was firing just fine. It's in excellent condition. I just picked it up from him and added it to my own collection. I've been reading a lot about issues with it firing out of battery. The gun is free to me, so i don't really care if it's junk, i just don't want it to blow up in my face.

I'm going to strip it and it'll look at the bolt face to make sure it's not flattened, I'll look at the slide to make sure it's not cracked. I'll also make a habit of checking to make sure the bolt is closed completely before firing for the first 100 rounds. What else should i do to make sure it's safe? Do i really need to check headspace?

Andrew

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[TDH]

Have a qualified gunsmith check it out.

[phil441]

A bunch of Type 3's are still out there doing their job day in and day out.
I'm sure that a bunch of farmers have never heard of the concerns.

May I suggest you go here CMP Help: Stock Cleaning, Ammo, Mag ID Accuracy - CMP Forums Help: Stock Cleaning, Ammo, Mag ID Accuracy - CMP Forums[/url]

Or I will try to post Steve's tutorial here:

Universal Firearms Carbines

The most serious issue here is that some Universals allow a hammer strike to ignite a primer any time after the bolt is fully forward, but not one bit rotated towards locked. There is no bolt/hammer cam to help the bolt close on some Universals. If a Universal fires unlocked, the bolt lug comes right back through the slide window breaking it. Delayed blow back is not advisable at 40,000psi.

The writer had that personal experience in 1970 with a brand new Universal Carbine. It is very scary when 40,000 psi comes unglued in your face. I have always been thankful for being very near sighted. I HAD to wear some sort of glasses my whole life. Living on a farm and being active, I had a hardened form of safety glass lenses. The face of the lenses were ruined, there were surface craters caused by impact of powder grains burning and pieces of molten brass. My eyes were unhurt. The joy of getting the brass picked out of my forehead will go unmentioned.

Universal rebuilt the Carbine for free and told the writer what had happened. The writer tested it with primed cases and realized it would still fire anytime the bolt was all the way forward. Once was enough. The carbine was taken to the shop, placed on an anvil minus the stock, and a 12# sledgehammer was applied until it was forever scrap.

The problem with Universal Carbines is not that they won't usually work and not that they won't usually fire. They usually do work and usually do fire. The actual problem is that a number of them FIRE UNLOCKED. You then have 40,000 PSI unleashed in your face. Not good.

The later you go into Universal production and including probably all the latest ones with two operating springs and a stamped slide with a cam window cut into it, the machining got sloppier and sloppier and the design and manufacturing fell apart safety wise. Universal did away with the USGI design receiver bridge firing pin retraction cam surfaces, the USGI design firing pin retraction tang, and eventually the USGI design hammer camming surfaces on the rear of the bolt that also protect the firing pin from the hammer. They went to a firing pin with no retraction tang.

The mechanism for this out of battery firing is two fold.

(1) In a Universal, the firing pin retraction surface cam cut into the bottom of the receiver under the bolt is either non-existent in some cases or mis-machined in other cases. In either event, it does not properly engage the tang on the firing pin even on the bolts with a tang on the firing pin. The tang is the part that sticks down below the bolt. Without the firing pin retraction surface cam cut being properly machined, the firing pin is free to go forward and strike a primer BEFORE the bolt is rotated to full locked position. It may allow the primer to be struck when the bolt is fully forward, but completely unlocked. It may allow the primer to be struck with the bolt fully forward and only partly locked. Or some variation of less than full rotational locking.

(2) The second Universal problem is the bolt surfaces cut into the rear of the bolt as they match the hammer surfaces. In a USGI Carbine, the bolt and hammer notches and cuts and bumps only align to allow the hammer to strike the firing pin when the bolt is between partly and mostly locked.

In Universals, the bolt may be totally lacking in the machine cuts, they may be mis-cut, or the hammer may not match. The combination allows the hammer to strike the firing pin before partly to mostly rotated lockup occurs.

The combination of these defects in a Universal has allowed any number of them to fire out of battery. The bolt lug comes straight back through the rear of the metal window in slide cam and all H breaks loose in your face. Without shooting glasses on, you will not see again.

Additionally, in many cases it was not only the safety design that fell apart, but the carbine itself, quite literally. A lot of the two part slides broke where the slide body and the handle were welded together. Not a sign of high quality. The trigger housings were made of some kind of zinc based metal, and they quite often broke, in one way or another.


Simple Safety Check

A simple test is to have some primed cases with no powder and no bullet. Empty primed cases. Again, no powder, no bullet. Simply primed cases.

Chamber the primed case. Hold the slide back so the bolt is fully forward, but not rotated, simulating a long round or a jam from whatever reason. Drop the hammer. If the primer fires, you have the answer. Very bad.

Again, chamber a new primed case and hold the slide so that the bolt is only turned to lock say a 1/4 of the way. Drop the hammer. If the primer pops, you again have the answer. Repeat this at say, 1/3 of the way, 1/2 of the way, 2/3 of the way, 3/4 of the way.

At some point, the primed case will pop the primer as you drop the hammer. In theory, the primer should only fire when the bolt is fully rotated and locked in battery. Any primer popping before that would do the same with a live round. As a practical matter, we know it will fire the primer before that. How much before is what we are trying to determine by the testing. The average USGI Carbine can be expected to fire some time after the bolt is about 1/2 rotated. What the test result means to a shooter, the writer cannot express an opinion about.

And be careful with the muzzle because the burning aluminum from a fired primer ejected from the muzzle will scorch a wood floor or a carpet.

The tests should be done with the muzzle up and with the muzzle down so that the firing pin is in both positions.

Do not reuse the primed cases while testing. The primers frequently dent long before they fire. An accumulation of dentings, may let them fire where they would not have fired if it was the first firing pin strike.

The rear bolt and hammer face features of a USGI made carbine are such that if the bolt is slightly short of 100% locked, then the energy of the hammer rotates the bolt toward 100% lockup. Then the hammer hits the firing pin with whatever energy is left usually firing the round. When this test is used on a USGI carbine, the slide has to be held quite firmly to prevent the bolt's rotation when testing. If the tester lets the slide move and the bolt rotate, it makes a false impression.


Symptoms to Watch For

A common symptom of out of battery problems are the "click" upon pulling the trigger and finding a chambered cartridge and the bolt unlocked or partially locked.

In a Universal Carbine, the rear of the slide cam window breaking out is a guaranteed sign of partial out of battery firing.

Light firing pin strikes followed by a lot of extra noise is often a Carbine out of battery. The hammer falls, turns the bolt and dents the primer, the slide runs forward, but the primer does not fire. In a simple weak hammer fall, there is a click. But if the slide is not forward until the hammer falls, there is a click-clack as the hammer falls and the slide moves.

The genuine RED FLAG is the cartridge firing and a failure to cycle with the fired case fully locked in the chamber.

As a safety warning, there is an oddity of Carbine functioning that bears a small bit of discussion. There are times when a Carbine fires and the end product is a completely closed bolt on the fired cartridge case. The shooter perceives it as a failure of the gas system to thrust the gas piston/slide/bolt to the rear or as a failure to extract and/or to eject. The remedies are often thought of in terms of a low power low pressure cartridge or of bolt face component failure. In most cases with the Carbine, neither is the problem.

In this specific failure to cycle mode, begin with a cartridge firing normally. The gas pressure forces the gas piston/slide/bolt to the rear, the operating spring forces the slide/bolt to the front, a new cartridge is picked up out of the magazine, the cartridge enters the chamber, the slide/bolt go forward, the bolt partially turns toward lockup, and things stop at that point lets say 1/2 or 2/3 bolt rotated.

At this point, the slide has not overrun the bolt extension in the slide cam. At this point, the slide has not run forward to push the gas piston back to the front. The gas piston is to the rear. However, the shooter does not often notice this. Unaware, the shooter pulls the trigger again. Either from wear/tolerance design in the hammer, bolt rear cuts, receiver firing pin retraction cam, or firing pin itself, many Carbines will fire in this partially locked condition. Sometimes the hammer forces the bolt to rotate towards locking fully and sometimes not. In either event, the cartridge firing is faster than the bolt turning and the slide running forward and the gas piston being pushed to the front.

When the gas pressure hits the gas port and then the gas piston, the gas piston is already fully to the rear and there is no motion imparted to the gas piston and thus no motion to the slide. Quite often, after the cartridge has fired, the slide goes forward locking the bolt down on the fired case hiding the real cause. This is what the shooter interprets as a low pressure round or a failure to extract/eject. It is not.

The point here is that any Carbine firing and leaving a case in the chamber with the bolt locked and the slide forward should be interpreted as the end product of a partially out of battery firing. The usual suspects in partial lockup situations are overly long cartridges, dented cases, brass/dirt on the bolt face or in the chamber especially at the shoulder/throat milling, or primers that are not seated fully. All these items interfere with the bolt going forward and jam the bolt before it can fully rotate. The partially locked bolt is "usually" or "often" or "most times" locked "enough" that the cartridge pressure is contained, but it is potentially a very bad situation.

Until another exact cause is identified, any of these situations should be treated as the end product of a partially out of battery firing.

One frequent "quick fix" type solution often volunteered is the "hi-speed" operating spring. This is simply a stiffer spring that when fully compressed closes the action with more zip. This tends to mask the real problems and create new ones. The stiffer spring resists opening the action all the way creating feeding and ejection problems. The action may not open all the way or it may open slower affecting ejection by not being open long enough.

If the action is ever fully opened, the stiffer spring will help close the action, but it is not a cure for the original problem. It is better to use new condition USGI springs for the correct balance of resistance to opening and closure power. The design is intended to open, stop moving when fully to the rear, and then move to the front. The original USGI spring specs do this in the proper manner.

In the normal extraction/ejection problems, the bolt is pushed to the rear, picks up a new cartridge out of the magazine, and somewhere in the process does not extract or eject the old fired case. Or there is a classic stovepipe with a new cartridge picked up. Or the ammo is actually so low powered, the action never cycles (rare) even partially.

But when the bolt and slide are just sitting there fully locked up with a fired case in the chamber, it should be a RED FLAG. Stop shooting until you know why it is happening.


Causes and the Inherent Solutions

Anything that mechanically hinders the Carbine's operating mechanism from going into battery should be avoided.

A failure of the Carbine to terminate its operating cycle in battery is usually caused by problems with the ammunition or with dirt and crud. Dirty chambers, brass shavings at the chamber lip or in the bolt face, or reloading dirty chipped dented brass causes problems.

New Carbine ammunition is usually loaded in cases near an overall length of 1.280". A reloaded cartridge case overall length exceeding 1.280" is an invitation to problems. New brass needs to be full length resized and trimmed before loading. That is the most desirable length for trimming reloads to. It is also the common answer in reloading manuals.

There is a reason for this. Every bit beyond that factory new length is just a bit closer to keeping a bolt from running all the way forward and preventing locking up in complete battery. The closer the cases are to 1.280", the easier the Carbine mechanism goes forward and locks the bolt with the slide overriding it. Any longer length is less desirable. Trim every reloading.

These items are discussed at length in other articles about reloading for the Carbine.

Stock wood can interfering with the slide's movement causes problems.

Shooting a Carbine dry of proper lubrication is in this category. If it rotates on a pin, oil it. If it slides, grease it. The lube will stay put that way and not spray your shooting glasses.

If the particular Carbine is one of the worst designed later Universals, there is a pin holding the plug in front of the gas piston that can be driven out, the plug removed, and then the plug inverted 180 degrees. The gas passage is thus blocked. This disables the semi-automatic functioning. The carbine can be used as a straight pull bolt action. With the slide manually operated and pushed forward over the bolt lug, the Universal is no worse than any other carbine firing in battery. Pull to rear, push to front, trap the bolt lug down with the slide.



Conclusion

Shooting a late Universal two spring stamped slide Carbine semi-automatically raises the simple question of why are you doing it? The writer would suggest that risking yourself or others with a known problem is unwise.

As to USGI Carbines, the foregoing is simply a bit of knowledge, some info on how to check a Carbine if you have a concern, and things to do to stack the deck in the direction of safe operation to the limits of the inherent design. By understanding the nature of potential problems, they can be prevented from occuring.




Like you, I have concerns, but in a crunch, I wouldn't hesitate to grab it. In fact, there's one of those within arm's reach now.

[phil441]

Oh, and Andrew,

WELCOME!
Glad to have you here!

Phil

[coppertales]

I picked up an early Universal, with the GI slide, about 10 years ago for 125 bucks. It is in like new condition and has run perfect for me, both with factory ammo and handloads. Is there anything I should be aware of with these early guns? Thanks...chris3

[ShaveTail]

My dad bought one maybe fifteen years ago (haven't fired it since I was a teenager). Since you plan to strip it allow me to note the obvious (that I had to learn the stupid way): this thing doesn't look much like a normal USGI M1 inside; the springs are a bitch to get back in if you take them all out.

All and all really not deserving of the bad rep it has IMHO.

[imarangemaster]

I had an early Universal in the 80s. It was pakerized had GI stock and parts. If I remember right, everything was interchangeable. Apparently it was back when they were using GI parts like Plainfield, etc. It even had a GI barrel.