So I shot my new suppressor last month (Vent Spiritus). Ran a couple mags through it so let’s call it 100 rounds. No gas, very quiet. On the next two trips same deal but now it seems very gassy. Strong ammonia (?) gas smell, burns the eyes a bit. I did change ammo to Hornady Frontier (?) but that seems like solid low end ammo.

Confused. After the second trip I stripped, cleaned, and lubed gun. Didn’t do anything to can.

Third trip still gassy if I shoot any5hing other than slooooow strings. It’s like night and day from first range trip. What gives?

What ammo did you use for your third trip? You said you swapped ammo between trips one and two. Did you try the ammo that you used on the first trip again for comparison? Some ammo, especially cheap ammo, can be dirty and smoky. Were the conditions the same when shooting? If outdoor, were there changes in wing speed and direction between the trips?

The smelly stuff was the Hornady Frontier. Not sure what I was using the first trip because they were loaded mags from way back. The last two trips was this frontier stuff. Could it be the ammo? Obviously my next trip I’m trying different ammo to rule that out but I just bought 500 rounds of it so if it’s the ammo I’m screwed. Could it just be bad ammo?

If it’s the same gun, same conditions, and the only thing different is the ammo, then it’s likely the ammo. A new suppressor isn’t likely to get clogged up in only 100 rounds and suddenly become gassy, even a PTR suppressor with the PIP design. The first thing I’d to is try different, better quality ammo and see what happens.

It's the different propellants in the ammo. Ammonia can be a product of the powder combustion, more with some types of powder than others. It's often attributed to breakdown of a stabilizer compound such as DPA (diphenylAMINE). The presence of moisture can exacerbate this effect, too.

The gasiness can also have a lot do to with powder, mainly the burn rate. I've seen dramatic reductions in the amount of shit-to-the-face just by switching to a faster burning powder in my reloads.