Shotgun shell lengths and pressures. 2 3/4 vs. 3 inch magnums

[SP5315]

This question has puzzled me for a while now. I do understand the difference in shotgun barrels when it comes to shotshell lengths. If firing a 3 inch shell in a chamber for 2 3/4 inches you will have a constriction caused by the longer shell in the shorter chamber. I also understand that it acceptable to shoot 2 3/4 and 3 inch rounds chambered in a barrel labeled for three inch shells. In this scenario I'm excluding 12 gauge shotguns chambered in 3 1/2 lengths. This also hold true for 20 gauge shotguns.

My question has to do with being told many times that it is not safe to change a 2 3/4 barrel out with one chambered in 3 inches because this is considered a magnum load, and the receiver was not made to handle the magnum rounds.

Now below is the SAAMI shotshell pressure standards. Sorry, it's on the small side.


The pressures for both 2 3/4 & 3 inch shells in 12 & 20 gauge have the same maximum working pressures of 11,500 and 12,000 respectively. it seems to me that the bolt locking mechanisms since they are designed to work at these pressures it should not be a problem in chaning out a 2 3/4 chambered barrel for a 3 inch chamber barrel on say your garden variety Remington 870.

If not, what am I missing here?

[Blood Trail]

That's hogwash. Most modern shotguns have at least 4 inches of the barrel mating with the receiver. The majority of the pressure happens in the forcing cone and at the end of the barrel, depending on the construction of the choke.

You have to be really careless to blow up a barrel.


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[NSB]

The only difference between 2 3/4" and 3" shells is the amount of shot contained. The longer shells aren't higher pressure simply because they're longer. What happens when you put a three inch shell in a two and three-quarter inch chamber and fire it is that the crimp might not have room to open and let the wad and shot pass without constriction.

[Boolit_Head]

The reason swapping out is not a good idea is all receivers are made to the same length. Putting a 3 inch barrel on some receivers may result in the shell not cycling through the action due to the extra length. It all depends on the model.

[NSB]

The ejection port is smaller on the 2 3/4" barreled model. Putting a 3" chamber on a receiver with the shorter port will not allow the shell to exit the gun. Gun companies like Remington like to charge you more money for the "magnum" or 3" receiver. Most companies today produce 3" field guns instead of both 2 3/4 and 3. There are still some clays guns that are dedicated to 2 3/4" (O/U's).

[Jim atlas]

Depends on the model of course. My mid 70's 870 with a 2-3/4" receiver will cycle 3" hulls with a 3" barrel on.
I should say, it will cycle SOME 3" shells depending on actual OAL.