I have the option to get a Sig 516 piston upper on the cheap. Is it really worth it to make the swap from a DI gun? I use a 10.5 carbine gas upper for duty and I haven't had a bit of trouble out of it. Aside from a little gas to the face suppressed it has done everything I need out of it and has been stupid reliable. The rifle sees a high round count, but being realistic, there's not going to be a time where I shoot a lot and am unable to clean it in an LE environment. Theoretically, it should always be in near clean "ready to go" status at the beginning of each shift.

I've read reviews on the 516 and it seems like a great platform. If I was starting from zero I wouldn't hesitate to go ahead and get the 516 upper. But since I already have a proven rifle, that cash money can go a long way... new optics, ammo, whatever.

Aside from the piston equipment and the I assume additional weight, the only other difference I can see is that the Sig upper barrel is chrome lined where mine is not. I don't want to start a DI vs. piston topic. I'm trying to decide if it's an improvement for my specific job.

Anyway, I appreciate the insight.

Edit: I'll add that I have had a few parts on my DI gun that have needed replacing. Broken gas rings, one side of cotter pin sheared off, bolt was replaced when lugs started wearing heavily. None of that ever kept the gun from working. I just noticed when I cleaned the rifle. Should a quality piston upper suffer from the same stuff; I guess with the exception of gas rings?

If you shoot suppressed there are definite advantages to a piston gun.

Am I really going to see benefits of piston rifle suppressed immediately or past a few hundred rounds when a DI gun would really start getting gunked up? That's what I'm trying to get a feel for.

10-8, IMO the advantages of the piston gun are several for the less-than-operator level, of which you are not.

1.  piston guns are more "adjustable" for both suppressed and unsuppressed settings.  Since you already have your 10.5" DI dialed in and know what it does both suppresed and unsuppressed the advantages here are minimal.
2.  The recoil pulse of a piston gun is different than a DI gun.  Advantages are minimal to none
3.  You can dial the piston gun down to the point that you are not beating the components up as bad as an over-gassed DI gun (of which they almost all are, especially a 10.5" sbr).  NOTE - you do this at the risk of not having it 100% reliable both suppressed and unsuppressed if you go too far
4.  Gas to the face is less in a piston gun, especially suppressed.  This one is a definite advantage
5.  The piston upper will weigh more than a DI upper.  Negative here if you are keeping it light

To answer your question directly, I feel you would have a minor gain in adjustability, some gain in wear and tear, definite gain in less gas to face, but losing in the weight department.  Only you can weigh these and determine if it is worth it.

This isn't necessarily correct.
The PWS mod 2 upper weighs LESS than any comparable upper I have weighed.

I really appreciate the info on this topic.

I think each bullet is pretty self explanatory, but I do have one question in regards to number 3. The Sig 516 upper has a selector for the piston (normal, weak, suppressed, and off). When you speak of dialing in the piston, is this custom work such as tuning a gas port on a DI gun?

Most all piston systems have an adjustable gas setting. Think of it like having an adjustable gas block on a DI upper.

Even without a adjustable piston,

Most piston guns especially in shorty versions have less muzzle blast.
Due to excess gas expelled out piston block not burnt out barrel
So for a shorty work gun you might see a benefit from this.

Other than that... you can go from cleaning say every 1,000rds to now 3,000
from lack of gas discharge in chamber area