How many rounds to wear out an M1A1 barrel?

[Doug Quaid]

My gun club has a full auto steel plate match once a month.   

This past match, I used my M1A1 instead of my UZI for the first time and shot WAY BETTER with the Thompson.  WAY WAY WAY BETTER.

The Thompson fits me real well and seems to be exceptionally accurate.

So now I'm thinking of using the Thompson more often, even though the ammo cost is high.  

I used up 500 lead 230 grain reloads during the match.  Did not have a single stoppage or jam of any kind.

I have about 2,000 rounds of jacketed CCI ammo I bought back before the pandemic, but I'm planning on mostly shooting lead reloads.

My M1A1 is a nice minty parkerized RIA-marked rebuild.   So if eventually swapped out the barrel for a NOS one, it wouldn't really affect the collector value of the gun all that much.   But I'd still like to keep the original barrel on it if possible.

The barrel looks brand new now.   The gun was a police department firearm and then went to a collector who never shot it.  

So how many rounds of lead reloads or jacketed bullets is an M1A1 barrel good for?   

 

[bug]

I'd be looking to replace between 100k and 150k.

[Rekraps]

Just like car breaks, the barrel is worn out when the lands are worn below tolerance. Each gun is different, just keep an eye on them. I would suggest you start looking around 5000 or so into the round count.

[StrangeRanger]

More like 50,000

[Rabbit57]

Doug, I am on thin ice here, but I did not think you could wear out a barrel with lead bullets.

Now there are a few points to be made. I always thought the wear on a barrel was caused by heat. Guys that like to get the most velocity out of a round, like the .22/250, push a jacketed bullet out the end of the barrel at 4,000 fps. This round generates a lot of velocity, and a ton of heat. 
Lead bullets can be pushed to some pretty impressive velocities, but this is not normal, and especially in the .45acp. The lead bullets are lubed, and not jacketed, so less friction, less heat. Most .45acp bullets are in the 850 fps range, so you are getting all of the benefits that would normally keep your barrel in good shape, plus some real economy. 

I guess it might be possible to wear out a barrel with lead bullets, but I can't imagine how many rounds it would take to do such a thing. I do think buying an extra barrel for you gun is a good idea, but not because I am concerned that you will wear it out using lead bulllets. We don't use corrosive primers like they did in WWII, and we tend to be more knowledgeable about cleaning our guns, and not damaging the crown of the barrel with a steel cleaning rod. But I would pick up an extra barrel, just in case you get a squib load and fire another round behind the squib, and ring your barrel. 

Now I am no expert, so some of you guys might know more. But in my many years of shooting, I have never had anyone show me a barrel that had used lead bullets and was worn out. I have a .22 rifle that I got for my 16th birthday, and it has had thousands of rounds through it, and it still looks pretty darn good. I would not stand in front of it, it still puts the little .22 bullet where I want it to go.

Mark

[jim c 351]

Using FMJ bullets your probably good for 15 to 20 K

Using cast lead or plate probably 1/2 million rds .

I seem to remember that one person here has a gun rental range that put 250k thru an M1A1, and it was still going strong.

Jim C

[maxfaxdude]

Here in Vegas, there are ranges with MP5s,Thompsons, etc. with a over a 1 million rounds of FMJ through them and still going.  Can't speak for accuracy though.... 

And besides the type of bullet, barrel life depends on how hot you let that barrel get.  Multiple mags dumps all at once results in a very hot barrel with much faster wear.

  

Edited November 19, 2022 by maxfaxdude

[john]

When I bought my first '28 (an AOC Bridgeport gun) from a friend, he had just replaced the barrel. Apparently, a squib load had pushed a bullet up near the comp and the last 3-4 rounds packed in behind it and couldn't be pushed out.

He had a local Minnesota gunsmith refit that plugged USGI barrel with a Numrich replacement.

He had a few hundred rounds through it when I purchased it from him and I figure I had probably 12-14k through it (all jacketed hardball) when it started to fail.

Apparently the front of the chamber wore so the round (which headspaces on the front rim if the casing) was pushed far enough into that chamber so that the firing pin was unable to pop the cap. A mallet was needed to pop the actuator rearward and free the "stuck" round.

Unfortunately, this showed up at a show and shoot in Ohio and although I was doing really well in the steel challenge, those malfunctions knocked me out of that. 😭

I replaced the barrel soon after with a USGI takeoff and the gun has run perfectly since then. And my Ceiner .22 conversion wouldn't fit that Numrich barrel, but worked perfectly in the new one.

I do my own barrel replacement now and it gets easier each time.

[reconbob]

We all have our opinions and experience. 

The thing that will cause a barrel to wear faster is how hot it gets. If the temperature of your barrel gets

up around 1000-1200 degrees oxygen will start to affect the steel.

Barrels do not last as long when fired using lead bullets. Lead bullets are frequently lubricated and lead is much

softer than FMJ and dirt and grit stick to, and/or become imbedded in the lead and have an abrasive effect on

the bore. I believe this is covered in detail in Hatchers Notebook.

You can put A LOT of rounds thru a Thompson barrel and it will look the same. You can't use accuracy as a guide

because lets face it - nobody is target shooting with a Thompson. The thing that will tell you if your barrel is shot

is when the gun starts to double or triple because you get short recoil where the bolt recoils far enough to eject

and feed, but not far enough to engage the sear.

My $0.02

 

Bob

 

[Got Uzi]

Hey I take offense to that Bob….once in awhile it’s kinda fun to target shoot and see what kind of groups I can hold off hand with one of my Thompson’s at 15 and 25 yards. (I’m joking about being offended btw)

In all seriousness tho-my AOC M1A1 has had the muzzle cut with threads to fit a blank firing adapter and you would think it wouldn’t shoot for crap given this, but it shoots amazing. 
 

Lead will plug up a barrel quick, especially when shooting full auto. I shot lead out of my Uzi one time and it was so plugged that the rifling was literally gone due to lead build up. That’s when I learned to shoot 4 and 1 if shooting lead….4 rounds lead, 1 FMJ. It cleans the bore out and makes it easier to maintain. 
 

To “shoot out a Thompson barrel” you have to look at a few things-what did the gun have on it before hand? USGI and Colt guns we will never know unless it’s a NOS gun. I can’t see how someone these days would “shoot out” a barrel just from honest wear and use but that’s just me. I was thinking there was something in a Thompson armourers manual about barrel service life but I can’t remember. I’ll have to do some digging. 

[john]

One thing I do know is the cleaner you keep a gun the longer it lasts.

Case in point:

I used to shoot a lot of prairie dogs. Others will relate.....when the dogs are "up", no ody wants to stop and swab the carbon out of the chamber and clean it off the bolt lugs and other parts.

Carbon is also abrasive.

My (since new) 700 Remington .223 varmint rifle has seen lots of dogs. Lots.

A rough estimate on the round count is between 6k and 7k. I've had several episodes where I've gone through 200 plus shots before cleaning. I do shoot moly coated bullets in a few of my rifles so copper buildup in the bore has always been nearly non-existent.

The chamber however, has worn over the years to the point that the primers were backing out of the casings (neck sized for that gun) close to .020 of an inch......I even pierced a couple. Time to fix the problem.

I had the barrel cut, threaded and rechambered to get some more out of the old gal. 1/8" took care of the excess geadspace but had to take a full 1/4" off to eliminate all the flame erosion in the throat.

I wish I'd cerrocast the chamber before doing that as I'm sure the headspace/shoulder were quite worn from shooting dirty. It would have been nice to see exactly where the wear was.

Back to the Thompson:

That Numrich barrel my friend had installed may have had a long chamber to start....many have posted here of the non-standard chambers in Numrich, Westie and Kahr barrels.

That said, I'm fairly sure that some amount of firing dirty had something to do with the wear also. Just like prairie dogs, you get somewhere you can make a joyous noise and......who wants to stop and clean?

Bob is right about heat, though.....along those lines, I used to squirt clp into the fins and shoot til the oil smoked, then it was time to let her cool a bit.

And thats probably too hot, but as I said, I'm pretty good at replacing barrels now.....and more generous with cooling time. I still oil the fins, but try to stop and let the gun cool before the oil on the barrel smokes off.