I have a MPX Copperhead on order. But I am really not a fan of a 4 1/2 inch barrel, shorter than some of my pistols. I threads it seems like people are either cutting 8" barrels down to 4 1/2 and changing threads OR dumping the short barrel and installing an 8" barrel. I am seriously considering hitting dead center by going for a 6 1/2" barrel. Short enough to stuff gun into a backpack or in the truck, but long enough to improve accuracy and repeatability. Question is: how come so little consideration of the 6 1/2" and why not. I especially want to hear from someone who made this change and how they feel about the revised gun. Thanks

First of all, while you do have the option to change barrels, you don’t have the option to change hand guards since you bought a copperhead. Whatever barrel you buy is just going to protrude further out from the front, but you can’t shroud it in anyway. Copperhead does not have any replaceable handguards.

Second, the 6.5” barrel makes no sense to me. The 4.5” is great for keeping it compact with a suppressor and keeping ammo subsonic. The 8” is great for those who shoot mostly unsuppressed. But the 6.5” worst of both worlds. And to boot, Sig doesn’t make a handguard for the 6.5” meaning your options are to go with a 4” and have a weird protrusion, an 8” and be forced into 100% suppressed shooting, or aftermarket.

I should have stated a Copperhead K because I wanted the sliding brace, in black and not tan, and not the 3 1/2" barrel of the Copperhead itself. I thought the option of a 2 inch longer inter-changeable barrel (the 6 1/2) would not look out of place yet add the benefits of being longer over the stock 4 1/2".

In Illinois we are denied the benefits of a suppressor, and any SBR is severely restricted in use and transport. A pistol (assuming a CCW license) can be carried loaded in a vehicle while an SBR cannot be carried loaded or across state lines. P.S. Illinois does not recognize ANY other states CCW permits.

I can give some perspective on the 8". I had two guns that were carbines 16" Kriss, and MPX. Along with BNT ghm 45 7", and PTR 9KT 5.16" When I filed the paperwork to make them SBR's I opted to take my MPX and Kriss down to 8 inches.

It is a very good size for moderate concealment. Carry and use around my property. Is it as concealable as my 9KT no, but when not shooting suppressed those extra inches give me some great velocities. If I remember correctly it is about 100-125 fps depending on ammo weight. If I am shooting subs it works just peachy with my can. I think accuracy is as good as it was with my 16" and Reliability is as good if not better.
Sig MPX

Kriss Vector

BNT GHM 45

PTR 9KT


So, the trade-off is ultimate concealability in a very compact form. AKA the PTR

Or

Slightly larger form factor with a bit less cramped shooting manual of arms for more recreational and self-defense use.


I can easily hit targets at 100 yards with my 9kt. I can do that with my other guns as well. Out past 100 yards, the extra size of the 8" guns comes in very handy. The longest shot i have on the property is 190 Yards. With the sig, kriss, and bnt that isn't a problem. I have not felt comfortable trying the 9KT at that range yet.

The carbon fiber lancer handguard I have is 6" You can find them used every so often. So, if you are set on the 6" options are out there.

If it were me, and hauling it in your car was the option you are looking for. Stick with the 4"

What is Illinois law about AOW? 5 dollar stamp for a forgrip.

I cut my 8" down to 6". I mainly did it to get rid of the retarded 13mm threads and re-thread to 1/2x28.

I haven't tried shooting 100y since the barrel chop. But the 8" barrel was about 3-4 inches low with standard loads.