Thread: Adapting rimfire suppressor for .38 special...

Hear me out, I know it's obvious you're not supposed to use a rimfire suppressor on a centrefire cartridge due to massive difference in pressure between the two. Ignore for a second that the diameter of the supressor is wrong and baffles would be on a collision course with the projectile,
.357 magnum is obviously gonna blow it apart just due to the very high pressure.
But .38 special has LESS chamber pressure than standard velocity .22lr ammo, not even close. Even .22 short has a greater max pressure than .38 spl.
So in theory one could adapt a .22lr supressor by changing the baffles to an appropriate diameter and it would handle the pressure just fine right?
Obviously it would need to be adapted/drilled perfectly concentric and all that but just in terms of pressure it should be ok right?
Especially subsonic hand loads.

The principal requirement of a suppressor is for it to have enough internal volume to contain and dissipate the gases produced. The gases are proportional to the amount of powder burned. A .38 Special cartridge would have at least four times more powder than a .22 LR, therefore you would need a suppressor with four times the internal volume to be effective. You could drill out a .22 suppressor to suit and it would reduce the sound a little bit, subject to staying in one piece, but the standard 1/2" UNF thread is not suitable for the .38 as the barrel wall would be too thin to be reliable.

How about a centrefire can style. I have 1 on my 7mm 08. Doesn't get much use so I can't speak to it's longevity but it does a fair job.

The reason I want to go with a flimsier suppressor is because I want to retain use of ironsights, most centrefire ones are 40mm in diameter which obscures the front sight. I've got a 28mm rimfire supressor here which doesn't obscure the sight.

Originally Posted by gundoc

The principal requirement of a suppressor is for it to have enough internal volume to contain and dissipate the gases produced. The gases are proportional to the amount of powder burned. A .38 Special cartridge would have at least four times more powder than a .22 LR, therefore you would need a suppressor with four times the internal volume to be effective. You could drill out a .22 suppressor to suit and it would reduce the sound a little bit, subject to staying in one piece, but the standard 1/2" UNF thread is not suitable for the .38 as the barrel wall would be too thin to be reliable.

That makes a lot of sense good point. I've found a 1/2 x28 .22 supressor which is the same factory thread as on my .357 rifle.

Update: having sourced a 28mm can and drilling out to 9.5mm, it does work. No keyholing or baffle strikes, however gundoc was right it is still fairly loud with .38 special, seems as though the internal volume is insufficient to contain all that expanding gas.

What thread are you using ?

Hi I did this conversion but from a 30 cal. centerfire sup
worked out really well especially using the 158 grain 38 sp lead Rn [American eagle ]

Originally Posted by AR7

Hi I did this conversion but from a 30 cal. centerfire sup
worked out really well especially using the 158 grain 38 sp lead Rn [American eagle ]

May I ask the outer diameter of the supressor? I'm keen to stay smaller than 35mm as not to obscure the iron sights

Originally Posted by dantheman

May I ask the outer diameter of the supressor? I'm keen to stay smaller than 35mm as not to obscure the iron sights

Lift the irons to allow the use of the correct suppressor? Or, failing that option maybe retrofit one of the detachable iron sight sets that clamp on and can be easily removed for use with scopes?

The main issue with drilling out a .22LR specific can is you are making the internal volume effectively less as well as the fact that the intended cartridge is producing circa 4x the expanding gasses. A lot of the earlier suppressor types were quite thin, Gunworks were 35mm if I'm correct with the older overbarrel types. The downside is the volume has to come from length forwards as with iron sights you'll need a muzzle can not an overbarrel so can't gain volume by extending rearwards over the barrel. This is bad, as the muzzle thread section is not likely long enough and robust enough to resist a decent (accidental) thwack while maintaining it's correct alignment - plus a long can projecting forwards is a pain in the arse generally.

Hi Dantherman my 38 special is 38 mm od and 210mm long
originally had it drilled out @ 10mm but increased the exit hole to 10.5 including a couple of baffles in then down to 10.25 for the next couple of baffles . BECAUSE
i forgot to have the rear bush retrued [ my bad ] AND as i was using lead projectiles there was a light skid mark on the supp. exit hole
I tried to pull this NO NAMED 30 cal suppressor apart my machinest got one end off an noted it was very well made even with O rings between the baffles
i havent tried it with any .357 ammo yet as i like shooting very quiet on the farm
cheers to all

I found suppressing a 44 mag the big hole in the end increases noise level,..

test of 38 Sp noise level across 300m valley
FED 158 grain lead RN V. Very quiet slight sound in flight easy to hear impact in grass /soft dirt
Freedom 158 grain copper coat RNFP about the same as above different flight sound
PPU 130 grain full copper jacket this surprised me that it wasnt that much louder than the above two
Fiocchi 158 grain copper jacket with lead soft point a lot louder than all the above but still pleasant to use via my rig
It seems fair to say Brand as well as weight of projectile //speed of projectile will change noise level

Rossi 38 sp / 357 used in test

check out the sonic feather weight supressor, a mate has one on his 357 mag citadel lever gun and still uses the factory iron sights