I recently acquired a Sig556 Patrol rifle in a trade.  I don't know too much about them, but I  have a few questions...

1.  My serial number starts with 44A and has a milled aluminum lower.  Is this a 1st gen or second generation rifle?

2.  Barrel isn't chrome lined, but looks to be nitride treated?

3.  Is the barrel HF or cut rifling?

4.  Is the rifle a mix of US parts and foreign made parts?  If so, what are the US parts?

5.  Does the rifle come in partially assembled and US parts added (similar to the SCAR's)?

It was fun dissembling and cleaning the rifle.  I was able to see similarities to the AK, FAL, FNC...

Thanks for taking the time to help answer these questions!

Some US parts, some Israeli, some from India. No one outside of SigSauer USA really knows what parts are made where.

The 556 is not imported from Switzerland. These are a wholly US product made with some US and some imported parts and without the involvement of SwissArms. Interestingly, some of the 551a1 lowers and upper receivers made their way over to Switzerland for completion. The uppers have Swiss pattern welds with the bolt-on top rail, exposed trunion of the 556/551a1, 551a1 lower, and a 551 LB barrel that has a removable flash hider. They are interesting, though they leave me with a WTF head scratching sensation, as they incorporate some of the WORST attributes of the 556 series IMO.

Thanks for the reply! Good info. I'm late into the Sig product line... especially since it's  e discontinued!  Look forward to getting out with it soon...

First gen rifles had a lower that accepted a AR type buffer tube as on a M4 type carbine.


Later ones had a collapsible side folding stock...


Latest type had a Swiss style stock.  Early ones actually had Swiss made stocks and later ones were a copy and not as heavy duty...


The lower receiver also changed as time went along.  Some had mag release fence, some didn't and the last version had ambidextrous mag release.  The A1 version's lower used original Swiss mags.

It is said the early ones had some Swiss parts in them.  Exactly which ones may vary depending on who you talk to.  A thread here speculates on the part origins.

Barrels were nitrided.

The short gas system of the patrol is totally US designed and is not Swiss, it is actually a longer gas system / piston length than the Swiss 553 (or 552).
Construction and quality has huge differences comparing side to side.

As others have said ...

US Made.

Early Sig556ER (the ugly fishgill model) may of included some SIG SAN made parts (I had one that did) but most of those parts were quickly used and US production replaced them in the assembly of ER and later guns.

The 44A lower is definitely Gen 2 but might also be Gen 2.5.  I've had 44A serial numbered Classic models with different magazine releases.

Sig went through a period of continual improvement.

ER ... massively unpopular
Classic Gen 2 ... much more popular
Classic Gen 2.5 ... lower improvements
Classic Gen 3 ... ambi lower
XI ... significant design changes

MCX ... "we gave up on the 556 in favor of this design"

From my experience with several Sig556 variants ... be aware that steel case ammo might stick in the chamber.  I had a couple with a poor record on steel case extraction.