Doesn't matter if its piston or DI, both are really pistons to be honest. Both systems rely on gas driving the system. The Di system reroutes the gas down the gas tube and pushes the BCG back via the gas key. The gas is then released into the upper receiver after driving the BCG.
Pistons are all a little different but work pretty much the same, driving a rod (piston) back and cycling the bcg and venting under the handguards or by the gas block.
Either system is dependant on the size of the gas port. The hole in your barrel that reroutes gas into the gas block. If sized to small, it doesn't allow enough pressure for the gas system. If sized to large, it will provide too much pressure increasing felt recoil and increasing wear and tear on your rifle's internals.
Most manufacturers err on the side of larger ports, allowing the use of cheaper underpowered ammo.
A correctly sized gas port, lets you use just about any ammo, while minimizing felt recoil and wear and tear on your parts.
An undersized gas port, won't allow your gun to cycle effectively making your AR a single shot bolt action.
Doesn't matter if its a piston system or di, if the hole's too small it won't cycle.
I've had a couple Spikes uppers and they have been overgassed. This allowed me to shoot underpowered russian steel case ammo with just about 100% reliability (only failures where ammo related (duds)). But even tho the system was a DI midlength recoil impulse was harsh, I was even able to use a 5.8oz buffer which is heavier than a h3 buffer almost twice the mass of a standard carbine buffer. The heavier buffer did help tame it a bit, but it really slowed down the timing. It also made the muzzle hard to control so I sold them looking for something else.
High end ARs by manufacturers like LaRue, Knights Armaments and others are notorious for not running the underpowered stuff. They tuned their rifles around 5.56 nato pressures, opting to make their gas ports for those higher pressures, to smooth out recoil impulses and decreasing felt recoil.
Long story short:
Everyone gun is a little different, kinda like having a personality. Try out some underpowered stuff, try some mil spec stuff. If it runs fine with everything (and most likely it will) just shoot it and enjoy it. Take your new baby out and run a few thousand rounds through her, and take lots of pics and share your experience with us! Chances are you will not run into any issues. Take a few different types of magazines, a few different types of ammo, and a shooting buddy or two.
I bet you'll have lots of fun. Don't forget the porn!
Assumption is the mother of all ****ups.
Know what you know, Know what you don't know. -Paul Pedzolt
"Jack of all trades, master of none, though oftentimes better than master of one" -Mynshul
Last edited by AgentTikki; 07-06-2013 at 05:23 PM.