What if: M1 Carbine were chambered for .30 Remington?

[Daviducus2]

230 grain "ball" is another name for standard fmj military fodder.

Thompson presently recommends only 230 grain ball for reliable function.

http://www.auto-ordnance.com/DL/WarningAmmoCard.pdf

 

[Clay_Allison]

230 grain "ball" is another name for standard fmj military fodder.

Thompson presently recommends only 230 grain ball for reliable function.

http://www.auto-ordnance.com/DL/WarningAmmoCard.pdf

I know that. That's why I use it as practice ammo in my 1911. 230 grain hollow points also cycle just fine.

 

[Daviducus2]

Do you own many firearms Clay? What's in your inventory besides that .45?

 

[Clay_Allison]

Do you own many firearms Clay? What's in your inventory besides that .45?

14:
2 .303 Enfields, (one sporterized, one all original
2 Mosin Nagants, one M44 Carbine, one 91/30 rifle.
3 1911s (Springfield Ultra Compact, Rock Island Armory GI, Grandfather's WWII issue)
1 Yugo M49 Mauser
1 Marlin .22 semi auto
1 NAA Guardian .32
1 Heritage Arms .22
1 .22 revolver of unknown parentage
1 Norinco Shotgun (Remington 870 clone)
1 Heckler Koch G3

 

[Daviducus2]

That's a very nice collection. Is the Guardian a concealed carry piece?

How do you like the G3?

 

[Clay_Allison]

That's a very nice collection. Is the Guardian a concealed carry piece?

How do you like the G3?

1: yes, I got it when I realized how little I was carrying the Springfield U-C 1911.

2: With the scope sighted in it shoots pretty well. I'd like to give it a bit of work to tighten the groups.

 

[Daviducus2]

1: yes, I got it when I realized how little I was carrying the Springfield U-C 1911.

I hear you there. I have Glock 27 which is a very potent little package yet still too large and bulky for comfortable pocket carry.

As much as I prefer the potency of the .40SW Speer Gold Dot 165gr loads, I have been thinking about a Ruger LCP in .380 because a .380 in the hand is better than a .40SW at home. The second worst thing in the world is having to kill someone. The worst thing in the world is having to kill someone but not having the means to do so.

 

[Clay_Allison]

1: yes, I got it when I realized how little I was carrying the Springfield U-C 1911.

I hear you there. I have Glock 27 which is a very potent little package yet still too large and bulky for comfortable pocket carry.

As much as I prefer the potency of the .40SW Speer Gold Dot 165gr loads, I have been thinking about a Ruger LCP in .380 because a .380 in the hand is better than a .40SW at home. The second worst thing in the world is having to kill someone. The worst thing in the world is having to kill someone but not having the means to do so.

I've heard good things about the little ruger.

 

[Ivan1GFP]

Hello Clay_Allison,

Regarding .45 ACP ammunition for the Thompson Carbine, the answer is a bit more complicated than "230 grain bullets":

What I observed was that the Thompson would not cycle reliably with commercial 230 grain FMJ (I BELIEVE it was Remington UMC brand but it has been so long I really can't remember). The gun would cycle fine with military ball (I believe it was TZZ headstamp). Nominal velocity of military ball out of a Thompson is (IIRC) 920 fps but was probably faster out of the carbine since it had a 16 inch barrel instead of little short one on NFA guns. Out of a M1911 type, military ball is nominal at 860 fps. Commercial 230 grain ball is nominally at 830 fps.

What I found out when chronographing out of a M1911 type is that the military ammunition averages very close to 860 fps. The commercial stuff only averaged 805 fps out of the same gun. Even with a 18 pound recoil spring, the 805 fps commercial stuff reliably cycles a M1911 type (Standard spring is only 16 pounds). Target loads for the M1911 (also with a 230 grain FMJ RN bullet) only averages between 700 and 750 fps. With the 18 pound spring, sometimes those won't cycle.

Folks probably expect me to be a bit longwinded, so I will try not to disappoint. Here comes a story:

A friend of mine with a Ruger P90 was having some issues with his handloads. Seems like about once every 10 shots or so, his gun would not go into battery. He diid not separate his cases by headstamp but just ran everything through in a single batch. (I think it was on a Lee Loadmaster.) After a range session, we decided to check out his gun. What we found was that most of the handloads would chamber just fine but a few would not. They would almost close, but not quite. I checked the headstamps. All the ones that would not chamber were PMC brand.

What we found was the following: The minimum case length for a .45 ACP is 0.888. The maximum is 0.898. The minimum chamber length is 0.898. The maximum chamber is 0.920. .45 ACP cases tend to run on the short side of that range. What you will find is that your typical M1911 type tends to have fairly long headspace. My sample size is small, but I am guessing about .910 to about .915. Because of the way the recoil spring pushes against the bottom of the barrel lug, the long headspace isn't obvious unless you put shim stock or feeler gauges to figure out how long a cartridge (or headspace gauge) needs to be before it doesn't close. With a lot of guns, firing pin portrusion limitations would prevent a gun with excessive headspace from firing but with the M1911, the firing pin portrusion is not really limited in a practical sense. The firing pin can stick out at least a half inch beyond the breech face, so it will always reach the primer. Also the extractor can hold the cartridge back even if the chamber is too long.

In this case, what we had was a cartridge manufacturer who made cases very near the max length (Cheers for them!!!) and a gun that had a minimum length chamber. Add a little bit of powder fouling and the gun stops working. What got me to thinking about this story is that PMC ammunition tends to be very close to military. I don't know if this is true in .45 ACP, but it is worth a try.

- Ivan.

 

[Clay_Allison]

Hello Clay_Allison,

Regarding .45 ACP ammunition for the Thompson Carbine, the answer is a bit more complicated than "230 grain bullets":

What I observed was that the Thompson would not cycle reliably with commercial 230 grain FMJ (I BELIEVE it was Remington UMC brand but it has been so long I really can't remember). The gun would cycle fine with military ball (I believe it was TZZ headstamp). Nominal velocity of military ball out of a Thompson is (IIRC) 920 fps but was probably faster out of the carbine since it had a 16 inch barrel instead of little short one on NFA guns. Out of a M1911 type, military ball is nominal at 860 fps. Commercial 230 grain ball is nominally at 830 fps.

What I found out when chronographing out of a M1911 type is that the military ammunition averages very close to 860 fps. The commercial stuff only averaged 805 fps out of the same gun. Even with a 18 pound recoil spring, the 805 fps commercial stuff reliably cycles a M1911 type (Standard spring is only 16 pounds). Target loads for the M1911 (also with a 230 grain FMJ RN bullet) only averages between 700 and 750 fps. With the 18 pound spring, sometimes those won't cycle.

Folks probably expect me to be a bit longwinded, so I will try not to disappoint. Here comes a story:

A friend of mine with a Ruger P90 was having some issues with his handloads. Seems like about once every 10 shots or so, his gun would not go into battery. He diid not separate his cases by headstamp but just ran everything through in a single batch. (I think it was on a Lee Loadmaster.) After a range session, we decided to check out his gun. What we found was that most of the handloads would chamber just fine but a few would not. They would almost close, but not quite. I checked the headstamps. All the ones that would not chamber were PMC brand.

What we found was the following: The minimum case length for a .45 ACP is 0.888. The maximum is 0.898. The minimum chamber length is 0.898. The maximum chamber is 0.920. .45 ACP cases tend to run on the short side of that range. What you will find is that your typical M1911 type tends to have fairly long headspace. My sample size is small, but I am guessing about .910 to about .915. Because of the way the recoil spring pushes against the bottom of the barrel lug, the long headspace isn't obvious unless you put shim stock or feeler gauges to figure out how long a cartridge (or headspace gauge) needs to be before it doesn't close. With a lot of guns, firing pin portrusion limitations would prevent a gun with excessive headspace from firing but with the M1911, the firing pin portrusion is not really limited in a practical sense. The firing pin can stick out at least a half inch beyond the breech face, so it will always reach the primer. Also the extractor can hold the cartridge back even if the chamber is too long.

In this case, what we had was a cartridge manufacturer who made cases very near the max length (Cheers for them!!!) and a gun that had a minimum length chamber. Add a little bit of powder fouling and the gun stops working. What got me to thinking about this story is that PMC ammunition tends to be very close to military. I don't know if this is true in .45 ACP, but it is worth a try.

- Ivan.

Perhaps your Thompson needs to have its spring replaced by a lighter one, if I am correct in understanding that the power of commercial ammo just isn't enough to fully run the bolt.

 

[Ivan1GFP]

No one ever said that it was "MY" Thompson. Besides, the gun is spec'ed out for military ball ammunition and runs fine with it, so there is no good reason to change anything. Who would have figured that commercial ammunition was so lightly loaded? The 805 fps surprised me also.

BTW, I believe there are actually two springs powering the Thompsons. Each is about the diameter of a pencil and they are not very strong if I remember right. The breech block is just really heavy and you really can't do much about that.

- Ivan.