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Gator
1 November 2009, 04:42
On the subject of midlengths generally having better pressure equalization over carbine gas systems, is there a difference in pressure between midlengths of different barrel lengths? Say a 16" over a 14.5"?
Paulo_Santos
1 November 2009, 07:33
The major difference will be the dwell time. Dwell time is the time it takes for the bullet to pass the gas port until it reaches the end of the barrel. If both gassed properly, the 14.5" barrel with the Midlength will be softer shooting. Other than that, they should be the same.
Gator
1 November 2009, 15:43
Sorry for the wrong word choice, dwell time is what I meant... [:)] So a 14.5 middy wouldnt have much difference in dwell time and handling over a 16 middy? Saying both had exactly the same config, same BCG/Buffer/FH?
Paulo_Santos
1 November 2009, 18:43
Sorry for the wrong word choice, dwell time is what I meant... [:)] So a 14.5 middy wouldnt have much difference in dwell time and handling over a 16 middy? Saying both had exactly the same config, same BCG/Buffer/FH?

Let's say you took a 16" midlength barrel and cut it down to 14.5". Your dwell time just went down since you cut the barrel down by 1.5". That will make your barrel shoot even softer than when it was 16", but you mayhave to open up the gas port since the dwell time is less.
Gator
1 November 2009, 19:59
Did you mean less softer on a 14.5? I always thought the less dwell time the harder the recoil...
Paulo_Santos
2 November 2009, 02:16
Did you mean less softer on a 14.5? I always thought the less dwell time the harder the recoil...

Yes. Softer on a 14.5".

Take a 16" barrel with a midlength and a 16" with a carbine length. The midlength is softer shooting because it has less dwell time.

Take an 18" barrel with a rifle length and an 18" with a midlength gas system. The rifle length in this case is softer shooting because it has less dwell time.
Gator
2 November 2009, 21:51
Alright. Had my initial info the other way around. [:)] thanks Paulo!
niner
3 November 2009, 05:56
Yes. Softer on a 14.5".

Take a 16" barrel with a midlength and a 16" with a carbine length. The midlength is softer shooting because it has less dwell time.

Take an 18" barrel with a rifle length and an 18" with a midlength gas system. The rifle length in this case is softer shooting because it has less dwell time.

So is there any substance to people saying you need 7" past the gas port to obtain the optimum dwell time? Looking at the 18" barrel for instance.
Paulo_Santos
3 November 2009, 10:31
So is there any substance to people saying you need 7" past the gas port to obtain the optimum dwell time? Looking at the 18" barrel for instance.

That is pretty much the golden rule, but not set in stone. You can have the Rifle length gas system with an 18" barrel, but you will have a larger gas port than you would have with a Midlength gas system. With an 18" barrel, you can use a Rifle, Intermediate or Midlength Gas system. They will all work fine if they are gassed properly.