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What are the differences between M2/M3 and M4?


rickreno
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hi rick,welcome,,thats alot of ground to cover on all three,in brief,the m4 is the costly one of the three which is gas operated and alot of fun,,the m3 is semi auto and pump via a switch,not too bad on price,,and the trusty m2 is only semiauto mode,,go and handle some at a gun show or a gunshop and see for yourself also,,peace man.

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The M2 is semi auto, it uses the inertia from the recoil to cycle the action. If you plan on putting more than just a couple accessories that add weight to your M2 you may have problems with the M2. Those problems being you may have the gun jam often. The M3 is basically an M2 that you can select to be either semi auto or pump action. The M4 is semi auto like the M2, but it is gas operated meaning you can weigh it down with all the accessories you want and it will cycle reliably.

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My local gun dealer sold me on the M4 based on the gas system. He said that the M2 and other Inertia Drive models required the butt stock to be placed firmly against the body when fired or they may not cycle reliably. The M4 is gas operated and I can vouch that it will cycle reliably when fired from a variety of awkward, unsupported positions. You can fire off shoulder using the pistol grip with no problem. I even tried "limp wristing" it to force a failure to feed with low recoil rounds but could not induce a failure. If you are familiar with semi-auto pistols you will know that if you hold it too loosely you can soak up enough of the recoil to prevent the action from cycling. The M2 and other Inertia Drive models allegedly suffer from this problem although I cannot give you any firsthand experience on this. Hopefully one of the M2 guys can confirm or debunk this theory. As a home defense gun I could picture numerous scenarios where you may need to take a shot without getting the gun firmly planted against the shoulder.

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As I understand the Inertia system, upon firing, the gun moves back along with the locked bolt leaving the bolt carrier to remain stationary until such time the bolt compresses the inertia spring causing the bolt carrier to direct stored energy rearward to cycle the action. Thus shouldered or unshouldered, the Inertia system will cycle.

 

That said, I believe if you can lock the gun from moving rearward upon firing, the Inertia system will fail to cycle. Now that said, I can't think of a realistic way of doing this aside from putting an M2 in a vice around the receiver and stopping all rearward motion with a very large mass under the vice. Very unlikely in a real world shooting scenario. This same theory does align well with the idea that mounting a lot of extra weight to the gun can reduce cycle reliability. Add enough weight and you essentially mimick my vice grips example.

 

There is an excellent writeup on the Inertia system on Wikipedia here.

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...That said, I believe if you can lock the gun from moving rearward upon firing, the Inertia system will fail to cycle. Now that said, I can't think of a realistic way of doing this aside from putting an M2 in a vice around the receiver and stopping all rearward motion with a very large mass under the vice.

 

That does explain one scenario that never jibed with my previous understanding. I remember a warning about bracing against a tree to steady your shot. Based on your info, the tree would arrest any rearward motion and render the action stationary and cause a failure. Placing your shoulder between a 12ga shotgun and an immovable object does not sound very comfortable to me but I can definitely picture the situation.

 

Thanks for the physics lesson:o

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I can only speak from my experience, and my M2 is a SBS (14"bbl) so I don't know how it's weight (or lack of) compares to other M2s. But I've shot it from the hip planty of times, shot it from the shoulder plenty of times, even shot it one-handed like a pistol a few times, and it's never had any issues (never tried it braced against a tree, don't see any reason to try that) . And I've shot everything through it (3" and under). It ate everything and cycled like a champ no matter how I shot it. (I can confirm that my M2 is very light! Seems lighter then my MAC-10 with a full mag). Again, don't know how it's weight compares, but the short BBL sure makes it manuverable through halways and around corners IMHO.

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  • 2 weeks later...
Thanks for all the advice - this site has some folks who know their shotguns.

 

I'm still looking at them (on-line) - no place local to see them (N. Idaho). Does anyone know which one (m2 vs m4) will cycle faster?

 

Buy an M4. You want a HD shotgun right? Why not select the one the Marines tested extensively and have been using in combat for the last 8 years.

 

One of many You Tube videos

 

Edited by BigHat
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Thanks for all the advice - this site has some folks who know their shotguns.

 

I'm still looking at them (on-line) - no place local to see them (N. Idaho). Does anyone know which one (m2 vs m4) will cycle faster?

In theory the M2 will cycle faster but i still think the M4 will cycle faster than you can pull the trigger. The M4 is also heavier due to the gas operated action. If you want just a plain gun with maybe a mag extension but not any more accessories and you price is a factor go for the M2. If you plan on putting accessories on the gun or money isn't a big factor the M4 will better fit your needs.

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