I am confused about the specs for shotguns.

 

I am comparing two Mossberg pump action 590a1 shotguns:

 

An 18.5" barrel model has an overall length of 39.5" and holds 6 shells (+ 1 in the chamber).

http://www.mossberg.com/product/590a1-7-shot-50776/

 

A 20" barrel model has an overall length of 41" and hold 8 shells (+ 1 in the chamber). It is 1.5" longer than the 18" barrel and 1.5" longer overall length.

http://www.mossberg.com/product/590a1-9-shot-51660/

 

Both magazine tubes seem to go the full length of the barrel. So how does adding 1.5" to the barrel length add 2 more 2.75" shell capacity?

 

The only thing I can think of is that the magazines have plugs to limit the number of shells but I am not sure why they would do this.

 

Thanks.

The first link has a shotgun with an extension on the tube I assume is included. The 20 inch version does not need an extension

 

 

Sent from my DROID RAZR using Tapatalk

But in both pictures the tube goes to the end of the barrel. With an overall length difference that is only 1.5" how can this hold 2 more 2.75" shells?

Very possible it is plugged to comply with ban states.  Some states do not care if semi-automatic or not.  The seven shot seems to be new this year.  The only other thing I can think of is because both have 3" chambers one is quoting 2.75 inch shells the other 3 inch.

But in both pictures the tube goes to the end of the barrel. With an overall length difference that is only 1.5" how can this hold 2 more 2.75" shells?

I'm doing the math and am equally confused. 7 rounds of 2.75" shells would be 19.25". That leaves 0.75" of extra space for a followers and compressed spring. I can't imagine how they expect to fit an extra shell in there.

If you have a shotgun shell, measure it. You will find that it is about 2.3" or there abouts. It becomes 2.75" when fired.

 

Sent from an undisclosed location via Tapatalk.

Also don't assume they count the same way for various models.

The first link has a shotgun with an extension on the tube I assume is included. The 20 inch version does not need an extension

Sent from my DROID RAZR using Tapatalk

I agree with this. It has to be something with it being a tube extension and the spring inside taking up room.