In my limited semi-scientific experience, DI is the champ.

A friend recently got a MCX Spear LT 300BO pistol with ~9" barrel.

We shot his gun alongside mine. Same ammo, same silencer, back-to-back. It really was back-to-back too, because there were two available identical silencers; we didn't have to swap the can around.

The DI gun had a bit shorter barrel, advertised as 8.3", where the SIG is advertised as 9".

The DI gun was quieter as both shooter and observer. The difference was more significant as the shooter. The first round "pop" as perceived by the observer was quite significant, with the follow-ups also being louder than the DI, but less-so than the difference perceived as the shooter.

Your experience may vary, but if it wasn't at least as controlled as mine, it may not be worth much.

Both men present and involved as shooter and observer agreed on the performance described.

It's worth noting that the DI gun does not have a JP-style "captive, silent" buffer/spring assembly, which is reputed to assist in noise reduction.

Could this phenomenon that is reportedly common with piston systems have anything to do with the difference? I.e., extra gas discharge that is not moderated by the suppressor.

Almost certainly.

I have read online, however, that piston advocates in the suppressed context cite an elimination of "port pop" that DI guns are subject to.

That "pop" happens somewhere else, if it doesn't happen at the moment the gas key separates from the gas tube or when gas vents out the side of the carrier. As evidenced in your photo.

It would be interesting to see by way of condensation signature in cool, damp weather how much difference there is in the gas expelled through the ejection port between otherwise similar piston and DI guns when suppressors are used.

But even if the difference is between gas discharged at the piston or at the gas key, wouldn’t the pressure and perhaps the volume of the gas be greater in a piston system?

Something that’s very common is for fans of anything to tout its virtues and advantages while ignoring the defects and disadvantages of what they don’t prefer. I don’t have any experience with piston systems or suppressors on gas guns, but it wouldn’t surprise me in the least for someone to say, “See, no port pop,” even though higher pressure and greater volume from other part of the system might get no attention whatsoever.

If you want to eliminate port pop, you need a bolt action or other locked breech system. All gas guns, whether piston or DI need to have a place for the gas to vent. That’s part of the design, and a suppressor isn’t going to get rid of that. A suppressor also isn’t going to get rid of the noise from the bolt slamming back home with each shot. Again, bolt action is the solution.

I’m not sure that it’s a hard and fast rule that DI is quieter than piston. It probably depends somewhat on design, ammo, etc. If their 300BO is like their MPX, Sigs are gassy. That doesn’t mean every piston gun will have the same port pop noise as a Sig.

When doing internet searches like "quietest 300 blackout semi auto host rifle" the AI summary always mentions the MCX platform. It also consistently mentions things like the Honey Badger and Maxim PDX-SD. Also mentioned, but less frequently, are things like the DDM4ISR and CMMG Dissent.

So the internet at large seems more-or-less split on the matter.

I guess it depends on tee specifics of each upper. Anything that bleeds off excess gas can most likely have a "gas pop" report that might be loud I had a superlative arms gas block for a while that bleed off excess gas on a DI upper. similar issue as a "piston pop"... i changed it to a riflespeed gasblock where it does seem to have reduced that "pop" especially on the first round.

i have yet to own a "flow through" or low back pressure suppressors, not sure how that changes things, but presume it also helps alleviate that pop for piston or other bleed off gas systems.

quote:

Originally posted by Dwill104:
If you want to eliminate port pop, you need a bolt action or other locked breech system. All gas guns, whether piston or DI need to have a place for the gas to vent.

Pardon my ignorance but has anybody put a suppressor on a H&K?

MP5s have a good suppressed reputation, but they're 9mm.

I have read that the actions on rifle-caliber roller guns are quite loud. I haven't experienced it firsthand.

So incredibly relevant, but unmentioned (unless I missed it): What was the can you both shot?

Based on your comment in the other thread, I suppose you're right.

I didn't consider it important, because what mattered to me was everything was nearly equal, apart from the weapons' operating systems.

The silencer in play was the SiCo Omega 300.

Your suggestion that a LBP silencer would make the difference less noticeable may be true.

quote:

Originally posted by KSGM:
I didn't consider it important, because what mattered to me was everything was nearly equal, apart from the weapons' operating systems.

Yes, but also no. I thought the same thing until we tried two identical, brand-new Shivs on a half dozen pistol hosts and then started introducing other cans into the mix, then swapping hosts. Some hosts do better with some cans and you think you have the host figured out and then you change the can and the host does something new. I didn't expect it, but I experienced it. Performance became so host dependent that I had to mentally average out the performance of each suppressor across the hosts to really get an impression of what was going on. For the PCC's and rifles, it was just straight "this is what we found" and knowing that there are even more variables at play with individual long guns than can be realistically accounted for.

quote:

Originally posted by KSGM:
The silencer in play was the SiCo Omega 300.

That can came out in 2015. We... we are so far beyond what that can is capable of at this point. I cannot emphasize that enough. You could buy a 3D printer today, a roll of Polymaker Fiberon PET-CF17, some 1/2x28 thread adapters, and a tube of JB Weld and print yourself a far superior can to that Omega 300 that would be cured and ready to use by about Sunday. I guarantee that.

quote:

Originally posted by KSGM:
Your suggestion that a LBP silencer would make the difference less noticeable may be true.

I try to avoid saying stuff like this because I dislike stating things in terms of absolutes, but: It 100% absolutely is true. This test tells us nothing without some more suppressors in the mix. You can really only take what you learned from this and apply it to those hosts with those cans.

Look, just take a look at your calendar for some time between say, October and May this coming fall-spring, figure out a weekend, fly out here and we'll put on a big overnight event. I have a network. If you make it the weekend of an EVT range day, you can have that experience plus get to shoot a ton of suppressors, look through some really primo night vision, and try out a bunch of tuned host weapons. It'll be an eye-opening experience. I've made the invite before, but we should actually make it a thing.

quote:

Originally posted by Jim Watson:

quote:

Originally posted by Dwill104:
If you want to eliminate port pop, you need a bolt action or other locked breech system. All gas guns, whether piston or DI need to have a place for the gas to vent.

Pardon my ignorance but has anybody put a suppressor on a H&K?

Are you ansking about a MR556/MR223, or a roller delay HK like the HK93? If it’s the former, then yes. I’ve run my MR556A4 11” suppressed with both a Lazarus 6 and a Griffin Explorr.

Based on the context of the quote, I think he meant a roller gun.

The roller gun doesn't "vent" the way other systems do.

A roller delay HK isn’t a “gas” gun where gas is bled off to cycle the action. The roller guns are blowback.

Yes.

I am saying I think he knew that.

My brief internet research revealed that the action noise on roller-delayed guns is reportedly noisier than other systems. Not gas venting noise, but other noise related to the reciprocation of the action.

This message has been edited. Last edited by: KSGM,