Got my form 1 today just over 2 months.

 

I really don't like you. Kidding! But yeah a bit jealous. I know EXACTLY what's going to happen. I'll order the necessary part and the day it arrives, my Form 1 will be approved. I'm taking bets.

 

Correct, that is all you need.

 

I've built three MCX lowers with the use of the stock adapter. SIG sells an MCX lower parts kit for $100 plus tax and shipping. The lower kit has the dual safety levers and dual mag releases just like the MCX so that the controls are the same. The lower parts kit does NOT include a SIG two stage trigger.

Bill

PS: With a 1 in 5 twist, monolithic projectiles work best for supersonic loads. B

 

I have an ADM and POF lower which are both full ambidextrous just like my LT lower. I'll nab the adapter. If my stamp comes in, I guess I can just turn around and sell it.

10-4 on the monolithic pills, I already have a few hundred Hornady 110gr. CX and Barnes 110gr. waiting for load development. But I also have around a thousand loaded cartridges with jacketed bullets. Hornady 110gr. VMAX and Speer 125Gr. TNT's. The TNT's will likely be ok but the Hornady VMAX, likely not. I shot both already and everything held together but I haven't exactly gotten the barrel hot, broken in, etc...things could change rapidly.

I also have a bunch of the Hornday Sub-X 190 grain bullets. I've not had good luck with those in any gas gun to date, with bullet setback being the biggest issue. Hoping they work better in the Sig.

 

What twist did the PSA barrels have? The Sig will shoot them but at 1:5 twist and with supersonic rounds, it's easy to exceed 300,000 rpm above 2000fps and both are above that. You'll get away with bench shooting slowly but if you were to say do a class or train where you're shooing a higher volume quickly, you could run into issues. It's fine if you're not running a suppressor but I run one almost all the time.

My DI 300 blackout rifle with a 10.5" barrel has a 1:8 twist and I loaded the Hornady and Speer jacketed rounds for that barrel. Absolutely no issues with my hand loads and it would stabilize 220 grain bullets no problem out to 300 yards. It'd shoot S&B 200 grain subs at about 1 MOA at 100 yards. But it would not shoot the Sub-X bullets well. Correction, I'd get issues chambering the round from bullet gouging to bullet setback. Even with factory-loaded rounds. Tried two different barrels with no success.

But no idea why Sig chose a 1:5 twist. It's severely limiting with supers.

 

What twist did the PSA barrels have? The Sig will shoot them but at 1:5 twist and with supersonic rounds, it's easy to exceed 300,000 rpm above 2000fps and both are above that. You'll get away with bench shooting slowly but if you were to say do a class or train where you're shooing a higher volume quickly, you could run into issues. It's fine if you're not running a suppressor but I run one almost all the time.

My DI 300 blackout rifle with a 10.5" barrel has a 1:8 twist and I loaded the Hornady and Speer jacketed rounds for that barrel. Absolutely no issues with my hand loads and it would stabilize 220 grain bullets no problem out to 300 yards. It'd shoot S&B 200 grain subs at about 1 MOA at 100 yards. But it would not shoot the Sub-X bullets well. Correction, I'd get issues chambering the round from bullet gouging to bullet setback. Even with factory-loaded rounds. Tried two different barrels with no success.

But no idea why Sig chose a 1:5 twist. It's severely limiting with supers.

1:5 is pretty odd, the Spears with 1:5 are all in 300 Blackout right? PSA's 300 uppers are almost all 1:8

 

@rontron The form you submitted asked for an address right??

Yes I omitted my personal information and was just trying to show dated submitted 02/14/2023 and date received 04/17/2023.

 

Yeah that's what I figured, that's why I didn't do it, I feel it's an unconstitutional attempt at a registry. I just bought a 16" m400 upper and I'm gonna wrap up the pistol upper and take off all accessories and separate the BCG from it as well and store it well away from my other guns. That's an oddly quick turnaround time, I have a feeling not many people submitted those forms.

 

I believe you're right, I know there was another rifle being developed with a longer barrel, can't remember the acronym but assumed it'd be the Spear LT. But yeah the Spear LT's barrel is 9".

 

I think that was the X series, the one that incorporates that absolute INSANE optic that they can't even show or talk about besides some small details, the Optic made by another company (possibly a Sig subsidiary) also bears the XM designation so it would kinda make sense. If I was in a war and knew the other guy had one of these in 6.8 with that basically "magic" optic that lets me hit first round shots at 800 yards JUST from setting a 25 yard zero would really ruin morale. Basically turns it into a videogame style ACOG with target tracking, arrows on the side to show you where your previously tagged targets are (you can tag up to ten individual targets and get instant point of aim on ANY of them at any time without even having to think about it. It's truly some next gen stuff. I know other companies make somewhat similar optics but this thing is really a new generation of that type of active optic system

X models write up: Army Announces 2 New Rifles for Close-Combat Soldiers

Also that gun looks awesome as heck btw

 

Adapter in and installed. If a POF and a Sig had a baby...

 

James Reeves references it in a review he did on the new military PDW (Rattler) and said it had a longer barrel. I'll find the video and post a link.

And thanks for the compliment! It'll be nice when the ATF decides to approve my Form 1 for the Sig lower.