Looking in to getting a Dissipator and was wondering if anyone had experience with one of the 20" barrels cut back to 16" with the port opened up(with the barrel turned to A1/A2 profile under the guards.)  Looking for as light as possible(hence not wanting 2 gas blocks,) but not at the price of reliability.

Thanks,
Jason

you are the first to post this question... today.

With port opened (big, like .100 - .110) it will function nearly all of the time, if you want better than that, get a midlength dissy. Mongo should be the guy you talk to, I built some 20 years ago and the field testing was disappointing; however, I am the first to admit that the current issued ammo will make the system work better than what we used back then, but I have never made one since to be honest... why, when you can have a midlength gas system?

A cut down gas block weighs next to nothing, and you can subtract the weight of 3.5" of gas tube from whatever it does weigh

I have one that was cut back so far the brake is directly in front of the gas block. It works fine with regular 55gr 223 fmj and the hotter mil-spec ammo. It works 50-50 with Wolf ammo, and not at all with the 45gr varmit ammo. I think that if it were cut to 16" like most dissy's it would work 100% with the wolf.

Quoted: Quoted: I have one that was cut back so far the brake is directly in front of the gas block. I hope the brake is permenant attached. If it's not, you have a short barreled rifle there...

It was done by KKF from what I understand (KKF stamped on brake) so I am sure it is. If it was not, the first thing I would do is get a Krink and have that welded on.

Quoted: A cut down gas block weighs next to nothing, and you can subtract the weight of 3.5" of gas tube from whatever it does weigh

+1  A shaved gas block only weighs 1.3 ounces (According to Forest's spreadsheet).  You're not really saving anything with the shorter gas block (.8 instead of .9 ounce), but that extra 1.2 ounces overall is a TINY price to pay for a reliable upper without "work".