Thought this might be interesting to post.
Hoping Sig will see fit to re-release civilian 9" 5.56 pistols someday...

These rounds are SS109 reloads using H335 powder:
9" MCX 5.56
Stats - Average2529.06fps (10 rounds)

For comparison:
16" SR15
Stats - Average2959.32fps (20 rounds)

14.5" ACR
Stats - Average2979.14fps (20 rounds)

Armscor 62gr ammo:
9" MCX 5.56
Stats - Average2361.34fps (22 rounds)

That’s pretty good results from a 9” barrel. I sure hope Sig makes the 9” 5.56 barrel again. Who want’s a 11.5” pistol even though most don’t but it as a “pistol.”

Both FN and LWRC make a PDW with 7.5” and 8.5” barrels, so hopefully Sig will do the same in a 9”.

Totally agree Cops.

For me it’s simple:
300blk is optimized for 9”. If I want to shoot 5.56 and 300 I don’t want to have 2 separate handguards for 2 different length barrels.
Additionally, 2500fps for 5.56 out of a 9” barrel is enough for me.

With the advent of all of these cool new braces there’s “almost” no need to SBR. Infact I probably wouldn’t have done either my MCX or MPX if these braces would have been available. Haven’t and won’t for my wife’s.

Wonder what the gas port needs to be opened up to for a barrel being cut-down?

I have a .300BO barrel that was cut down, but the previous owner never had the port opened up...

It was a wicked sweet deal though! ...For a single shot MCX .300BO 8" barrel...

~Will