Velocity boosting muzzle device

[RX-79G]

Hello. Been thinking about short barrels and AR15s, like the original Commando.

The history was that the 10 and 11.5" XM-177 barrels were too damn loud, so the 4.5" moderator was used to quiet them down. Later on the military shifted to simply adding that amount to the bore length to create the M4, which is much less loud than an un-moderated 11.5 or 10" barrel, yet has much more velocity.

AR15 pistol and SBRs with XM-177 barrels don't normally get moderators because the are legally silencers, so those concerned about the noise use blast cans, which are just big open ended expansion chambers that throw the muzzle blast forward. My understanding is that they are still super loud indoors.

If you're going to put a longish muzzle device on anyway (blast can, moderator style flash hider), wouldn't it be useful to have a muzzle device that simply extends the bore almost like having a 14.5" M4 barrel?

I realize that adding another section of rifled barrel would have problems, but what about having a straight section that is the inner diameter of a 5.56 silencer baffle? Something like 7mm. The point of a baffle is that it allows the least amount of gas blowby without touching the bullet, so would a 7mm tube that's 4 inches long restrict the blowby enough to boost the downrange bullet velocity while increasing velocity? Would it have a negative effect on accuracy? Does anyone make such a device?




The Retrorifle "fake moderator" on the far right is said to be "solid", and clearly tapers to a small inside diameter from the hider cuts back to the threads. How small is the bore in such devices, and do they quiet things down?

Thanks.

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[Stomper]

Ear-pro quiets down an 11.5" barrel enough….

 

[arrowshooter]

These are the closest I have seen to what you are looking for. Not a 7mm'ish hole though.

1/2-28 RH Barrel Extension (Black Steel) - 4 Inch - Fits .223 / 5.56 /.22

Introducing our line of barrel extensions that allow you to add length to your barrel. Perfect for those whose handguard is longer than the barrel, this handy adapter adds 4 inches to your barrel to clear your guard.

www.infiniteproductsolutions.com

 

[oremike]

There are no free lunches, a longer barrel allows the powder to burn under pressure for a longer time increasing velocity. As soon as you break the bullet to bore seal you stop gaining velocity.

 

[RX-79G]

There are no free lunches, a longer barrel allows the powder to burn under pressure for a longer time increasing velocity. As soon as you break the bullet to bore seal you stop gaining velocity.

Yes and no. The VP70 pistol decreased muzzle velocities by using extra deep grooves to allow some blowby. And Gemtech and others claim suppresors increase muzzle velocity. There must be a breakover point where velocity increases go to zero.

Another way to make something like this would be to make the extension the unrifled and the size of the groove diameter so there is some gas seal and yaw control without any harsh transition for the bullet.

 

[solv3nt]

Yes and no. The VP70 pistol decreased muzzle velocities by using extra deep grooves to allow some blowby. And Gemtech and others claim suppresors increase muzzle velocity. There must be a breakover point where velocity increases go to zero.

Another way to make something like this would be to make the extension the unrifled and the size of the groove diameter so there is some gas seal and yaw control without any harsh transition for the bullet.

You could use a faster burning powder.

 

[Member 34319]

Yes and no. The VP70 pistol decreased muzzle velocities by using extra deep grooves to allow some blowby. And Gemtech and others claim suppresors increase muzzle velocity. There must be a breakover point where velocity increases go to zero.

Another way to make something like this would be to make the extension the unrifled and the size of the groove diameter so there is some gas seal and yaw control without any harsh transition for the bullet.

I'd say if there are increases from suppressor use it's due to loss of initial turbulence from hitting an environment, not some sort of voodoo magic. The bullet leaves the pressure of a barrel into a sealed environment, and if you cleaned the can, it's more of a controlled environment vs the ever changing environment of shooting a gun. I doubt there are significant increases in velocity due to gases escaping around the bullet. That just seems like they wasted potential energy to push the bullet down the barrel. I've noticed changes in impact with rimfire cans. I've shot enough through them now to know the dirtier they get the worse they perform. Velocity wise, I've never noticed any data that indicates the bullet flying faster through the suppressor.

 

[RX-79G]

I'd say if there are increases from suppressor use it's due to loss of initial turbulence from hitting an environment, not some sort of voodoo magic. The bullet leaves the pressure of a barrel into a sealed environment, and if you cleaned the can, it's more of a controlled environment vs the ever changing environment of shooting a gun. I doubt there are significant increases in velocity due to gases escaping around the bullet. That just seems like they wasted potential energy to push the bullet down the barrel. I've noticed changes in impact with rimfire cans. I've shot enough through them now to know the dirtier they get the worse they perform. Velocity wise, I've never noticed any data that indicates the bullet flying faster through the suppressor.

I guess my assumption isnt voodoo but simply that there was more net pressure behind the bullet than in front. And there's no bore drag to counter it.

 

[RX-79G]

You could use a faster burning powder.

Mainly looking to quiet things down by getting a similar benefit as a longer barrel.