Gas port size for 16in rifle length gas

[Mr. Goodtimes]

I've always been fascinated by the Colt 605 and thought it a great idea. I've wanted a KISS/iron sights rifle for some time and like the rifle length hand guards but don't really feel a 20in barrel would be the best most practical solution in my area, should the rifle ever had to see serious use.

With the great pricing that grant offers on Coly rifles to First Responders, my plan is to buy an AR-15 A4, send it to ADCO and have the barrel cut to 16.5 and the gas port opened. I would also be putting in a Geissele SSA and a Lancer systems rifle length FF tube and Surefire MB556 to finish it off as the ultimate KISS gun.

What size should I have the gas port opened up to? Rifle will be run mostly on M193 but needs to run reliably on anything.


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[MegademiC]

They will suggest not going below 17.5"... at least that's what they told my brother a few years ago.

Most people use a midlength lopro gas system with fsb in the rifle position.

Will you be shooting unsupressed or is this for a 109% supressed gun?

[Mr. Goodtimes]

They will suggest not going below 17.5"... at least that's what they told my brother a few years ago.

Most people use a midlength lopro gas system with fsb in the rifle position.

Will you be shooting unsupressed or is this for a 109% supressed gun?

Almost entirely unsuppressed.


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[tlw613sp]

I would suggest having a middy gas system with a FSB placed at the rifle position. A rifle gassed 16" barrel is finicky.

[Mr. Goodtimes]

I understand these systems are finicky, what I'm looking for is a starting point for the gas port. I don't want a dissipator. If I have to I may just buy a FN or Colt carbine and stick a middy barrel on it.


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[BFS]

I understand these systems are finicky, what I'm looking for is a starting point for the gas port. I don't want a dissipator. If I have to I may just buy a FN or Colt carbine and stick a middy barrel on it.


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You said you wanted to take an AR15A4, cut it to 16.5", and open up the gas port.

That is the exact definition of a dissipator.

[titsonritz]

You said you wanted to take an AR15A4, cut it to 16.5", and open up the gas port.

That is the exact definition of a dissipator.

A dissipator will typically have a rifle length handguard and front sight position but a shorter gas system.

1280px-Dissipator_Barrel.JPG

[BFS]

A dissipator will typically have a rifle length handguard and front sight position but a shorter gas system.

1280px-Dissipator_Barrel.JPG

What you speak of is a mock dissipator. I would know, I own one. 16" Barrel, mid .078 gas, fixed Rifle FSB, I put a KAC rifle length surplus rail on it, married it to a A2 lower... I even made it real purty with some Rustoleum flat tan...

A real dissipator is a 16" barrel with Rifle gas. Thats the actual definition. OP said he wants to take a AR15A4 and cut to 16.5". = Dissipator. Then said he doesnt want a dissipator.

[mig1nc]

There's always this: http://www.dpmsinc.com/TAC2_ep_89-1.html

Or the more basic version: http://www.dpmsinc.com/TACTICAL-16_ep_107-1.html

EDIT: Or for something higher end to meet your design, you could get this barrel: http://micromoa.com/16-rifle-gas-flu...to-1-7-barrel/

[tom12.7]

Unless its a fair weather cleaned and lube range toy using full port power 5.56 of the same type exclusively, then I would not advise doing this with a 16" 5.56 rifle gas.
If it was 100% suppressed, It can be very doable. Porting just depends on the action, ammo, and can.