I picked this 551-SB upper up from Kyle @ Chitin Defense in May and have been trying to get a lower for it. Finally worked a deal for a semi-converted F/A lower from a guy who had one for sale which he got from Gatewood. I had to crib a grip from a spare grey WCA lower I have but will order one to replace it. I used a factory Sig 1913 adapter and brace.

That is purdy.

I am jealous.

That lower looks goood ... well, it all does but I really like the lower!

BTW ... is this going to be a shooter?

Looks great. Are you going to SBR?

Yep...this will be a shooter and will likely file for a stamp.

The green looks great. Dig that sling too.

That looks awesome. How much are the uppers and are they still available? A quick google doesn’t show anything.

Yes, JDI has them in SB and LB. SB are far easier to get but SAN/SwissArms/SigSauer AG are rreally a small operation so expect to wait

Interesting, I didn’t realize JDI had complete 551 uppers with receivers, I’ll have to send them a note.

That brace gives it a real HK33 / 551 mashup vibe. I like it.

They're barreled uppers with handguards. You have to add the bolt, carrier and CH. And the lower of course.

PGT since these are imported as only to be assembled into pistols, what (if anything) has to be done to SBR one?

Mechanically, just add a stock and hung pin...a 2min job. Legally, you need to do some parts swap for 922(r).

For 922r compliance I put a 556Xi lower on my P553 ... technically you shouldn’t have too because as an NFA firearm it’s no longer a sporting weapon ... but the BTAFE says it’s required because you created a new rifle, therefore is subject to 922r.

Personally I like and have a lot more “AR” mags than SiG mags. Mine came with the stock & cheekiest, I also like the ambidextrous selector and SiG logo on the magwell ...