Experience with very long "Reflex chambers" on AR (223) cans

[DKDravis]

Hi there!

A friend of mine has an AR-15 - 5.56/.223 (Not going into the discussion of 223 vs. 5.56 Nato -- He mostly shoots surplus or reloaded 5.56)
He runs a Colt AR Heavy Match bbl, cut to 15" .. He does not want to shorten it further, but he would like a "moderator" that goes all the way back to the rather short handguard.

Another fried of mine has a permit to build and sell firearms and parts, but has no experience in building silencers, so he has enlisted me to do the design.

The long (apprx 5-6") reflex portion of the silencer could be used to make a rather large reflex/blast chamber -- but are there any distinct disadvantages to making use of this space to increase the blast-chamber?? Will it help reduce blowback? (the AR has an adjustable gasblock)

Any thoughts! The can will be built from grade 5 Ti (+grade 9 tubing) and maybe 7075-T6 alu for the outermost baffles -- This will not be a rapid-fire silencer.

[cdakers]

Most would recommend the first and possibly second baffles be made of 17-4 stainless for strength, durability and erosion resistance.

[DKDravis]

No thoughts on the "reflex chamber length" ??

I do know that it does not contribute much to the overall reduction of noise, what I'm worried about is first round pop or other negative effects from a large "reflex chamber"-

Does anyone have experience with using wire mesh or other types of "filler" in the reflex portion of a silencer -- My thought was to use this and "wetting" it with oil?

[John A.]

I'm going to assume that the upper receiver still has the gas tube installed and isn't neutered to single shot.

If it's a semi auto, how do you plan to make a reflex chamber and still accommodate the gas tube?

Or, are you planning to just go back over the barrel a little in front of the gas block?

Regardless, most reflex cans are essentially hollow, but if you needed to reduce some of that volume if you have a lot of FRP, you can stuff it full of copper mesh if you can make some way to isolate the mesh with a ported dividing wall (from lack of better description).

[mr fixit]

I'm going to assume that the upper receiver still has the gas tube installed and isn't neutered to single shot.

If it's a semi auto, how do you plan to make a reflex chamber and still accommodate the gas tube?

Or, are you planning to just go back over the barrel a little in front of the gas block?

Regardless, most reflex cans are essentially hollow, but if you needed to reduce some of that volume if you have a lot of FRP, you can stuff it full of copper mesh if you can make some way to isolate the mesh with a ported dividing wall (from lack of better description).

Question for John from a bystander to this question...
Wouldn't filling the reflex area with mesh somewhat negate the reflex area?

[DKDravis]

@John A.

The rifle has a 15" bbl, (No SBR rules here ) so from the threaded portion to the gas-block we have around 150 mm (Metric minded individual here ) or 6 inches apprx.

The gas-block is a small adjustable type, so just for the looks we plan to cover that to the hand-guard tube with an extension on the "moderator"

The outer tube will be 40 mm grade 9 Ti tube, or high temperature Carbonfibre aerospace tube (Custom made, since that is "my thing" )

We are not worried about the heat, since this silencer will not be used in a "rapid fire" situation. We will probably make the tube itself replaceable with either T6 alu or Ti

We plan to test it with no mesh filling or liquid in the reflex chamber(s) and then see if there is a FRP problem, if thats the case we will try mesh filling and maybe wetting it with thin (low viscosity) oil --

[John A.]

Question for John from a bystander to this question...
Wouldn't filling the reflex area with mesh somewhat negate the reflex area?

No.

The mesh acts essentially the same way as eyelets in the sionics second stage cans. 223 has lots of pressure to work with at the muzzle.

DKDravis, it's a good idea to try the reflex chamber empty first. And since you're able to do more with your cans that we on this side of the ocean, you have a lot more flexibility to experiment.

[gunny50]

Hi there!

A friend of mine has an AR-15 - 5.56/.223 (Not going into the discussion of 223 vs. 5.56 Nato -- He mostly shoots surplus or reloaded 5.56)
He runs a Colt AR Heavy Match bbl, cut to 15" .. He does not want to shorten it further, but he would like a "moderator" that goes all the way back to the rather short handguard.

Another fried of mine has a permit to build and sell firearms and parts, but has no experience in building silencers, so he has enlisted me to do the design.

The long (apprx 5-6") reflex portion of the silencer could be used to make a rather large reflex/blast chamber -- but are there any distinct disadvantages to making use of this space to increase the blast-chamber?? Will it help reduce blowback? (the AR has an adjustable gasblock)

Any thoughts! The can will be built from grade 5 Ti (+grade 9 tubing) and maybe 7075-T6 alu for the outermost baffles -- This will not be a rapid-fire silencer.

Good questions. Where are you located?
Reflex will help with blowback when done right.

First round pop can be solved in several ways.

[DKDravis]

Hi!

I'm in Denmark -- Here there are no SBR rules, but AR's are almost impossible to get a permit for. (Really any Semi-auto centrefire rifle)

Only rules for "Rifle length" is: Barrel minimum 30 centimetres (11.8"), Rifle overall 60 centimetres, (23.6") - Folding stocks only allowed if they do not make the rifle shorter than 60 cm, and still allow it to function. The same goes for "take down"

The owner of the rifle does not want to shorten the barrel from the 15" it is now. (Wisely I think, .223/556Nato is not really a "short barrel effective" round IMHO, Even at 15" the muzzle-pressure is quite high)

This can will be an experiment, so I will try a lot of different options, but the rather long reflex chamber will be a constant, though I may experiment with various types of "filler" in the chamber.