45 acp rifle silencer

[Morgan]

This form 1 took nearly 6 months to be approved, must have been put in the circular filing bin for a while! But finally done and am starting to build it. I've asked questions and read till I'm blue in the face. there's lots of contradictory information out there.

I ended up with a 7.5 inch 45acp barrel and a break action rifle. Due to the break action there is only about 3 inches of barrel ahead of the pivot and I want to be able to easily move it to another rifle down the road, so I think I will be avoiding a reflex design. I put 15 inch length on my form 1. My goal is lowest noise, esp. on the first shot. I can machine anything and diameter doesn't matter to me.

I read one place that says volume is king and then I read volume makes first round pop worse. I've only made rimfire silencers until this one and they have noticeable first round pop on pistols even without overly large volumes.

So my questions are how to minimize first round pop?
Should I make it coaxial or not?

If I make basically a 2in diameter screw-on with cone baffles how much blast chamber volume should I try?

If I make it coaxial how much blast chamber should I have and what diameter for the outer shell and the baffle section?

[yondering]

I can't speak to your 45 ACP application specifically, but have noticed that larger blast chambers seem to have more first round pop, but quieter subsequent shots, compared to the same baffles spaced out more evenly through the suppressor with a small blast chamber. That is with simple 60 degree clipped cones and subsonic 35 cal rifle loads.

My .22 cans have no discernable first round pop; one is a Form 1 and the other is an Outback II. Both use K baffles with a "Dater hole" in the first baffle. Perhaps that hole makes the difference? I have heard significant FRP on some other 22 cans, so it's not just my bad hearing.

Don't know if that helps you any?

[Morgan]

Sounds reasonable. I should add that I am leaning away from the coaxial so that I can adjust the blast chamber volume by adding/removing baffles and/or changing baffle spacing. A guy I work with is a sot so that's easy. I figure the coaxial design would make a much larger blast chamber that could not be easily be reduced.

I'm also curious about porting the barrel into a separate volume. Seems to me this would reduce the pressure before the bullet exits the barrel, thus reducing noise when the bullet exits the barrel. Can't get a concensus on this.

[VinnieBoomBah]

I ended up with a 7.5 inch 45acp barrel and a break action rifle. I want to be able to easily move it to another rifle down the road

I can't believe I am going be "that guy" this early on a Sunday morning, but . . .

[yondering]

I really dislike ported barrels.

But, that may be partly because I like to shoot cast bullets and am fond of accurate guns.

[Morgan]

I really dislike ported barrels..... because I ...... am fond of accurate guns.

I keep hearing this yet countless pistols, rifles, shotguns, and all gas guns have holes in the barrel with no ill effect. How do they do it?

[yondering]

I really dislike ported barrels..... because I ...... am fond of accurate guns.

I keep hearing this yet countless pistols, rifles, shotguns, and all gas guns have holes in the barrel with no ill effect. How do they do it?

By ignoring the first half of my sentence, like you did.

[T-Rex]

No reason you shouldn't be able to produce a wonderful can.
Larger, overall, volume will not increase FRP. That's a direct correlation to blast spacing and design.
If you don't plan to use this on a pistol, you should be able to keep it around, or under, 8".
I'm not sure I understand your reference to coaxial designs. Do you mean K-Baffles or some exotic, one-off, design?
K-baffles, when properly made, will offer superior suppression.
Radials (parabolic frustums), like that which are found in an Octane45, will also yield good reduction numbers.

Wanting to reflex, back over the barrel, is not a terrible idea. However, it will limit your availability to swap to different host firearms. The same goes for porting the barrel. Once the suppressor is removed, you're not likely to use that firearm, until it is returned. Yondering has a valid point, but it's negated by the use of PC cast bullets.

Here is a well made, 45acp, suppressor, from 80% baffles. It is for a pistol, but removal of the booster will facilitate shooting from a rifle or fixed bbl.

I'll shamelessly plug my own build here. While it's an integral, and thus not swappable between hosts, I think the portion with baffles suits your plan.

A couple things to remember about OD/ID.
The larger you make it, the longer your baffles will be and thus the less you can fit in a given length.
This is important, because today's designs focus on baffles which work the gases better and don't require vast amounts of volume.
The larger your OD, the greater your increase in overall material weight. Some folks don't care, some do. I prefer to go for maximum suppression, but keep weight to a minimum, within my design allowances.

[Capt. Link.]

Barrel porting is very effective but must be done with great care if not to effect accuracy.Cast bullets will cause these ports to fill with lead and null the effect.
With the dimensions given porting the barrel for a .45acp would not be required or recommended.
-CL

[Morgan]

T-Rex: I picked 45acp for cheap subsonic jacketed ammo, I Won't ever shoot lead bullets. Your build looks very nice - have you shot it with the ports blocked to see the difference(hose clamp covering them perhaps)? That would be very interesting. I really like those 80% baffles, but I envision larger diameter. The transfer to a bolt rifle is why I'd like to avoid reflex volume - reading here has made me feel ok that I won't lose significant performance without reflex.

I had planned on 2 inch diameter and making the baffles curved like octane baffles. Should I go smaller diameter? What about length - I put 15in on the firm 1 but that seems excessive for not having any reflex, I'm thinking 10-12 in. Lastly, any input on blast chamber size?

[yondering]

The same goes for porting the barrel. Once the suppressor is removed, you're not likely to use that firearm, until it is returned. Yondering has a valid point, but it's negated by the use of PC cast bullets.

+1 to everything you said except this. Powder coat helps with ported barrels and low pressure loads, but doesn't do squat when the pressures go up. I've done a LOT of work with PC bullets, that's most of my shooting for the past few years, and I've found without a doubt that gas cutting still happens, sometimes badly, even with powder coating in ported barrels.

If a guy is never going to shoot cast, it doesn't matter so much, but can still negatively effect accuracy.

[yondering]

T-Rex: I picked 45acp for cheap subsonic jacketed ammo, I Won't ever shoot lead bullets. Your build looks very nice - have you shot it with the ports blocked to see the difference(hose clamp covering them perhaps)? That would be very interesting. I really like those 80% baffles, but I envision larger diameter. The transfer to a bolt rifle is why I'd like to avoid reflex volume - reading here has made me feel ok that I won't lose significant performance without reflex.

I had planned on 2 inch diameter and making the baffles curved like octane baffles. Should I go smaller diameter? What about length - I put 15in on the firm 1 but that seems excessive for not having any reflex, I'm thinking 10-12 in. Lastly, any input on blast chamber size?

How are you going to cut those?

[Morgan]

How are you going to cut those?

Is this a serious question? A lathe.

[yondering]

Meaning, how are you going to cut the radiused cone? Radius turning attachment? Form tools? or ???

[T-Rex]

doesn't do squat when the pressures go up. I've done a LOT of work with PC bullets, that's most of my shooting for the past few years, and I've found without a doubt that gas cutting still happens, sometimes badly, even with powder coating in ported barrels.
If a guy is never going to shoot cast, it doesn't matter so much, but can still negatively effect accuracy.

I was mainly focusing on the 45acp, as was the OP's build priority.
With higher velocity rounds, I've really only used PC bullets in an SKS and a S&W 6" 686 with a Magnaported bbl.
I was able to get them to factory speeds w/o seeing negative affects.

In your testing, were all ports cut into the grooves?
Were they all cut perpendicular, to bore axis, or were angles tried?

[yondering]

No angles. AR15 gas ports, ported parrels, etc.

It really doesn't matter if the ports are in grooves or lands, or in between. Gas cutting doesn't show up as leading in the barrel at first, until it's really bad. Accuracy suffers long before leading shows up in the barrel, with powder coated bullets and ported barrels.

A copper gas check takes care of most of those issues of course.

[alordnapa]

[quote="Morgan"]This form 1 took nearly 6 months to be approved, must have been put in the circular filing bin for a while! But finally done and am starting to build it. I've asked questions and read till I'm blue in the face. there's lots of contradictory information out there.

I ended up with a 7.5 inch 45acp barrel and a break action rifle. Due to the break action there is only about 3 inches of barrel ahead of the pivot and I want to be able to easily move it to another rifle down the road, so I think I will be avoiding a reflex design. I put 15 inch length on my form 1. My goal is lowest noise, esp. on the first shot. I can machine anything and diameter doesn't matter to me.

I read one place that says volume is king and then I read volume makes first round pop worse. I've only made rimfire silencers until this one and they have noticeable first round pop on pistols even without overly large volumes.

So my questions are how to minimize first round pop?
Should I make it coaxial or not?

If I make basically a 2in diameter screw-on with cone baffles how much blast chamber volume should I try? "

First round pop seems to have a lot of contributing factors, but just the name of the phenomenon suggests the problem; A big expansion chamber filled with Oxygen-rich air suddenly filled with high temperature gasses. This causes ignition of the air in the expansion chamber, but also physically conducts that shock to the metallic suppressor tube, and sound travels faster in metal than air, so in a way, a primary expansion chamber can act as an acoustic amplifier. ( On the other hand, it keeps you from melting your first baffle to a meteoric slab of metal goo) Although its kind of "old school", filling that expansion chamber with baffling ( Lithium grease wetted felt washers, steel wool, etc.) will help absorb the sound physically and not take up too much of the actual volume. A material like copper or silver screen ( Okay, that last one may be had to come buy) will both suppress shock concussion noise and minimize "ringing" the tube like a giant bell, and since copper has a very high specific heat, it will start the process of absorbing heat quickly and re-radiating it slowly, our optimal purpose. Running the expansion chamber stuffed with copper wire screen punched to washer dimensions helps absorb the shock wave by changing its angle of propagation, disrupting air flow, and its high thermal conductivity adds oodles of efficiency and mechanical damping. Wetting the copper screen ( Water, Lithium grease, super-secret-silencer juice, etc) will increase the thermal diffusion massively, and with a low pressure, closed breech, break action like you describe, coolant splatter will not be factor, especially in a low-pressure cartridge like the .45. You can stick a piece of tape over the end of the end cap to keep drips from making a mess, or even buy a sack of plastic end-caps for the business end. ( http://www.widgetco.com I kid you not!) Lithium is less likely to drip down the tube than water. A rolled screen tube, wetted or not, through which the projectile (hopefully) passes without strikes can be almost as effective. A casting made from silver or copper to fit your expansion chamber can be made with large grain sea salt ( Like Kosher salt) poured into the mold before the metal. When the casting is dropped in water, the salt will dissolve, leaving a nice porous copper filter that when wet, can make an amazingly efficient thermal and mechanical suppressor....I doubt ATF would view that as a disposable item, like a wipe, but I am concerned only with the science here. Speaking of wipes, another old-school technique, these can help a lot with FRP ( Especially if you just happen to have a vacuum pump to evacuate your suppressor before you shoot through the end-wipe, or alternatively, to pre-charge your suppressor tube with an inert gas with excellent heat transmissive properties, like Helium)

[Morgan]

By coaxial I would make a conventional silencer about 1.5 inch diameter. The muzzle brake would vent into the space between the outside of that and inside of an outer shell about 2inch diameter.

I'm leaning towards longer and thinner now, around a foot long and 1.5 or 1.75 diameter. I will be able to ream the acp chamber out to 45colt and move it onto a lever gun then - I've already made a magazine tube that will accommodate a 1.75 inch silencer. I'm having trouble getting a magazine tube to work with a 2 inch silencer...

Any input? Is that so long that it's past the point of diminishing return?

[gunny50]

I will be able to ream the acp chamber out to 45colt

Use a bold gun
Ream it 45 WinMag and use M1 carbine magazines, make hand loads and be happy with HV and Subs.

Gunny

[Morgan]

I was looking for input on the silencer, not the gun.

[gunny50]

I was looking for input on the silencer, not the gun.

That might be the fact, but you do need to know if your going for the slow 45 ACP or HV 45 WM or fast 45LC as you need to keep this in mind with you silencer design.

45 ACP Rifle go 1,5"and 8" should do with K's
45WM 1,5" / 1,75" ca 9" and start with 2 cones rest K's as you would shoot sub and HV

Gunny

[Morgan]

That might be the fact, but you do need to know if your going for the slow 45 ACP or HV 45 WM or fast 45LC as you need to keep this in mind with you silencer design.

Goal is quietest with subsonic ammo. Don't care about supersonic noise.

[T-Rex]

There's really no need, with today's experience and designs, to go w/ a huge OD, unless you're planning to use an outdated style.
Neither of my 45 cans exhibit a very noticeable or unpleasant FRP.
Both suppress very well.
My primary design would be based off a smaller OD can w/ K-Baffles. 1.375-1.5" OD
My second design would copy the link I provided here.

[Morgan]

I am trending towards smaller diameter now - I was planning on 2 inch. The weight savings and consensus that squeezing maximum volume out doesn't help much convinced me. What about length? I need at least 9 inches to make it legal length and put 15inch on the form 1. Apart from weight what is the downside to extra length? Where is the point of diminishing return?

Would having a brake help enough to be worth the effort? It would be part of the silencer, not a QD device.

I will doing cone baffles, not K.

[yondering]

How are you going to cut those?

Is this a serious question? A lathe.

Meaning, how are you going to cut the radiused cone? Radius turning attachment? Form tools? or ???

Still wondering about this, if you've figured out a method to cut radiused or frustro cones on a manual lathe? Or are you using CNC?