well i am in the process of building a xm variant rifle using a superlight bbl. cut down to somewhere around 12.5 and will be attatching a moderator on the end to bring it to legal lengths and wanted to know if anyone has done the same without opeining up the gas port.

i will probably use a bbl. from bushmaster and removing the fsb is a pita, as of right now i am 2 for 3 with bushmaster's fsb and i dont really like the odds. also dont want to go through the hassle of finding a .625 fsb if i have to cut it off. so thats my reason for the question.

also wanted to know if i were to use a pigtail or fatboy gas tube would it simulate a bigger gas port.



thanks as always for any help offered

Colt's gas port sizes are:  [10.5" - .093]    [11.5" - .081]    [14.5" - .063]    [16" - .063]

May be helpful.

Mike

Quoted: Colt's gas port sizes are:  [10.5" - .093]    [11.5" - .081]    [14.5" - .063]    [16" - .063] May be helpful. Mike

thanks!


guessing there is only slight difference between 14.5 and 12.5 since its only .022difference between 14.5 and 11.5

Bushmaster also over-sizes the gas-port on there guns, so you might me alright.

Quoted: using a larger gas tube will exacerbate any short strokes. if you plan on adding the mod to it you're best bet is to do all the cutting then test fire with the can and then short stroke test it, as the can will add some small amount of function to the barrel. sned me the barrel and I'll knock of the FSB for ya the gas ports sizes are not linear as they vary with the distance to muzzle

will take up on your offer if i find that the fsb needs to come off.


kinda figured the bigger gas tube would make matters worse but noticed they offer the pigtail gastube for pistol(7.5") length bbls. and wondered about it.

thanks for the offer.

Quoted: Bushmaster also over-sizes the gas-port on there guns, so you might me alright.

not doubting your statement but is there anywhere that states that? would put me at ease if there is truth to this.

Quoted: Colt's gas port sizes are:  [10.5" - .093]    [11.5" - .081]    [14.5" - .063]    [16" - .063] May be helpful. Mike

I had no idea Colt overgassed their rifles so much!

Quoted: Bushmaster also over-sizes the gas-port on there guns, so you might me alright.

What are bushmaster size gas holes  

Quoted: ...and will be attatching a moderator on the end to bring it to legal length...

Is it a fake moderator or a real one? The reason I ask is that a real one is considered an NFA item. If it's a real one, might as well go SBR as well and not have to permanently attach it.

Quoted: Quoted: ...and will be attatching a moderator on the end to bring it to legal length... Is it a fake moderator or a real one? The reason I ask is that a real one is considered an NFA item. If it's a real one, might as well go SBR as well and not have to permanently attach it.

trying to set up a llc right not and if all goes well it will be both


but if not then it will be a non-nfa that is permanently attatched.