Suppressor question

Tom

Tom

Well-Known Member
So, I finally got my first one. I haven't tried it yet and have what is probably a dumb question.
I see things recommend to eliminate first round pop ranging from using co2 or nitrogen to running it wet.
Here's my question. If o2 in the blast chamber is responsible for frp, would blowing into it work, or would there still be too much oxygen in your breath?
 
Ian

Ian

Notorious member
Intelligence has many consequences. Let me overthink a reply and wax philosophic about it for a couple of paragraphs.

First off, FRP is variable and we have no details of your system. Second, if in practice it is a problem to you and fixing it really matters, there are several practical and effective solutions.

Now, do tell us about your new toy...."inquiring minds" and so forth.
 
J

Jeff H

NW Ohio
VERY limited experience here, but directly relevant:

I just got my first one last fall - a Liberty Mystic for an 18" 357 Mag Carbine.

Having read about the "first round pop," I was worried that I'd just spent the money and was in for the wait, only to have something louder than my cat-sneeze loads.

All for naught.

Once I shot it with the loads I intended to use in it, I got no FRP. Sounds like popping a tire chuck off a compressed air hose - if that. My main/most used load is a 148 grain WC with 3.3 grains of Unique (over 2,100 loads from a pound of powder) to keep it just sub-sonic in the carbine barrel, but still be a useful load in the 3" revolvers. I've not chronographed the load in either yet, but I should be getting about 750 from the revolvers and just over 1kfps from the carbine. It's STILL a tad "too much" for close-up varmint/vermin use and will exit 'coons with enough force to put quite a gouge in the sod.

I believe that the small amount of fast(ish) pistol powder is used up way before the bullet ever clears the muzzle and there's just no fire left to consume any oxygen in the can. THAT is my GUESS, because I've never personally experienced FRP, so haven't had to experiment/deal with it to know when it will or won't happen.

I've shot some 180 and 158 grain bullets out of it at maybe 1200 fps, and I do hear the sonic crack, which is about like a 22 short in a 16" rifle barrel, noise-wise, but can't distinguish any FRP even then, but I'm still using mo more than 6 grains of Unique in that load. Haven't messed with full-house 357 Mag loads, but then the sonic crack would likely be louder at that point and FRP would be a moot point.

I let a friend shoot it in his woods a while back and he was "sawing" a small dead log in two with it (grinning like an iduit the whole time) when I suggested he put one into the wet mud bank on the other side of a nearly drained pond. We had gotten used to the "PFFU-CHUNK" sound, but when the WC hit that mud, it was LOUD, almost like someone fired a 4" 22 pistol. Left quite a hole in the mud too.
 
J

Jeff H

NW Ohio
I should add that there is one particularly concerning consequence to having a suppressor on a pistol-caliber-carbine, which I've not seen mentioned before, and this is MUCH more serious than FRP!

If that worries you, you SHOULD be worried.

This "can" has had an alarmingly deleterious effect on my primer supply. I frequently pick the danged thing up and shoot at stuff for no other reason than to have fun.
 
Spindrift

Spindrift

Well-Known Member
The difference in noise level between the first shot, and consecutive shots, is typically around 1-2 dB in tests I have read. It is not something I’ve noticed myself (all my rifles, save the Marlin carabine, are suppressed).
I hope you’ll enjoy your new suppressor!
 
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Tom

Tom

Well-Known Member
Ian said:
Intelligence has many consequences. Let me overthink a reply and wax philosophic about it for a couple of paragraphs.

First off, FRP is variable and we have no details of your system. Second, if in practice it is a problem to you and fixing it really matters, there are several practical and effective solutions.

Now, do tell us about your new toy...."inquiring minds" and so forth.
Click to expand...
Ian, lack of intelligence has its consequences in my case.
I bought a banish30 intending to put it on a 10.5" ar15 300bo I cobbled together. I'm considering a Ruger American in the same caliber.
We've got some wacky bills proposed in the state legislature that would ban threaded barrels, along with other features. Not sure how that's going to play out.
It was the "90 day turnaround" with the eforms that motivated me to buy one. Of course, by the time I did in March, that 90 day thing turned into 9 months. Anyway, I got it, but I really have no real use for it other than being one of the cool kids.
 
Tom

Tom

Well-Known Member
Spindrift said:
The difference in noise level between the first shot, and consecutive shots, is typically around 1-2 dB in tests I have read. It is not something I’ve noticed myself (all my rifles, save the Marlin carabine, are suppressed).
I hope you’ll enjoy your new suppressor!
Click to expand...
1 or 2 dbs? That's like the noise a mouse in wet foliage makes at 100 yards.
 
Tom

Tom

Well-Known Member
Jeff H said:
I should add that there is one particularly concerning consequence to having a suppressor on a pistol-caliber-carbine, which I've not seen mentioned before, and this is MUCH more serious than FRP!

If that worries you, you SHOULD be worried.

This "can" has had an alarmingly deleterious effect on my primer supply. I frequently pick the danged thing up and shoot at stuff for no other reason than to have fun.
Click to expand...
2100 rounds per lb? Doing my gazintas, that's like 1.5cents a round and 10cents a primer at current prices.
 
RBHarter

RBHarter

West Central AR
I saw a demo once with a decibel meter 3 feet off the muzzle and 3' from a fresh pig kill , under 15 min old . 6.8 spcii through a can at 2400 fps MV. 108 db at the muzzle and 115 though the ribs 118 db on a shoulder 117-121 on spine hits . So the impacts were louder than the muzzle noise and super sonic crack with SP bullets and a 2100 fps impact speed .

If the powder is fast enough and the barrel is long enough there's not a whole lot bang anyway . Something about the muzzle pressure being below super sonic 1200 psi sticks but that's probably not right .

I've been party some spirited dialogues about muzzle escape , shock waves , and air compression in front of the bullet during the acceleration. I'm still not convinced I'm wrong about the the first 10 feet of free flight .

The pop , if it is air compression caused will be recharged if there is any dwell time at all with the bolt open . IE if there's time for the smoke to chimney out the barrel will be clean air .
I'd bet it's more likely that it's super heated film oils effectively dieseling in the can when it gets all that compressed clean air that exited in front of the bullet .

The second part of this is that if there is a super sonic crack it's happening inside the can , obviously if it's gasses only , but also if the bullet cracks , instead of 3" to 5' past the muzzle . This part has zip to do with the pop .
 
fiver

fiver

Well-Known Member
and in certain cases unburnt powder will zip past the bullet at supersonic speeds even if the bullet isn't going that fast.
 
Ian

Ian

Notorious member
FRP is caused by a cold can. Powder is close to stochiometric but still on the rich side to prevent torching gun parts, plus there's modifiers like potassium carbonate IIRC that mitigate flash and retard burn somewhat. The hot gas with some white-hot embers hits that cold air and it makes more volume than normal, hence the pop. Ablatives help a lot, so does just sticking a lighter in the can for ten seconds and then screwing it on before the first shot. If you care.

It's interesting to hunt with a can and no ears, even with full-power ammunition. You'll know exactly where you hit and what the bullet did when it got there. Even at the shooter's end, the bullet impact is more audible than the report. One thing I did when shooting super-quiet loads at home, particularly at night when I wanted to play but it was winter and the time change screwed me out of daylight, was to built new traps using crumb rubber because sand and dirt berms are NOT quiet when the bullet smacks into them and everyone for half a mile knows shooting is going on even if they can't hear the rifle shot.
 
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