just tried out form 1 9mm, S&W MP9 won't cycle AT ALL with it on

Yes, it can be legal to make a silencer. For everything Form-1, from silencer designs that are easily made, to filing forms with the BATF, to 3D modeling. Remember, you must have an approved BATF Form-1 to make a silencer. All NFA laws apply.

Moderators: mpallett, bakerjw

Post Reply
rtv900
Member
Posts: 19
Joined: Wed Apr 01, 2020 4:44 pm

just tried out form 1 9mm, S&W MP9 won't cycle AT ALL with it on

Post by rtv900 »

so I'm hoping someone might have a solution.
My S&W threaded barrel MP 9 2.0 cycles fine with no suppressor, but with it on it does nothing. It isn't even misfiring mid cycle, the action doesn't even open at all. I have to hand load each round.
This is perplexing for me only because I have a walther P22 that cycles horribly with subsonic ammo un supressed but with my suppressor cycles perfectly. For the 22 I have a sparrow monocore if that matters.
I am using standard velocity in the 9 however.

My design is cone style baffles 60 degree, .410 hole double clipped, 1" blast spacer and then 9 baffles in 1.5" tube 8" long. Tube is .050 wall stainless, baffles are aluminum .040 wall thickness.

Am I just totally out of luck? Is this common? I don't understand why the weapon can't cycle. I would think a suppressor if anything would add gas pressure to cycle the action like it does in my walther.
User avatar
T-Rex
Silent But Deadly
Posts: 1865
Joined: Wed Oct 29, 2014 3:38 pm
Location: CT - The AntiConstitution State

Re: just tried out form 1 9mm, S&W MP9 won't cycle AT ALL with it on

Post by T-Rex »

Booster?
Completed Builds www.silencertalk.com/forum/viewtopic.php?t=79895
Burst Calculator www.engineersedge.com/calculators/pipe_bust_calc.htm
Silencer Porn www.instagram.com/explore/tags/silencerporn/
alordnapa
Silent But Deadly
Posts: 192
Joined: Tue Sep 30, 2014 11:01 am

Re: just tried out form 1 9mm, S&W MP9 won't cycle AT ALL with it on

Post by alordnapa »

"I would think a suppressor if anything would add gas pressure"

It will indeed add gas pressure, but the added mass hanging on the end of the barrel in other than a fixed-barrel weapon can prevent the slide from unlocking. A "Booster" also known as a LID, for Linear Inertial device may be needed to let your recoil operated slide overcome its moment of inertia. It does this by adding a spring that allows the barrel to travel a bit during recoil. The bright side is that your gun will be much quieter and less messy if you keep it as a manually operated weapon, but I can see that you must be frustrated with that idea. LID's are not controlled anywhere as far as I know, and you can buy one online from a number of sources.
rtv900
Member
Posts: 19
Joined: Wed Apr 01, 2020 4:44 pm

Re: just tried out form 1 9mm, S&W MP9 won't cycle AT ALL with it on

Post by rtv900 »

ok
admittedly I am very new to this part of the design of a good functioning suppressor so I will definitely look into a booster
I did get the impression that the mass of the suppressor was a part of the issue
Honestly it isn't that terrible manually reloading each shot once you accept that you will be manually reloading
I just really thought it would cycle auto
rtv900
Member
Posts: 19
Joined: Wed Apr 01, 2020 4:44 pm

Re: just tried out form 1 9mm, S&W MP9 won't cycle AT ALL with it on

Post by rtv900 »

so now that I am looking into booster I am finding that they seem to have a different thread on the suppressor end?
My thread fits directly to the barrel obviously so it's a 1/2-28

Does anyone know of a booster that has 1/2-28 on both ends? Or am I just going to have to make a new endcap?
User avatar
T-Rex
Silent But Deadly
Posts: 1865
Joined: Wed Oct 29, 2014 3:38 pm
Location: CT - The AntiConstitution State

Re: just tried out form 1 9mm, S&W MP9 won't cycle AT ALL with it on

Post by T-Rex »

rtv900 wrote: Mon May 04, 2020 6:46 am so now that I am looking into booster I am finding that they seem to have a different thread on the suppressor end?
My thread fits directly to the barrel obviously so it's a 1/2-28

Does anyone know of a booster that has 1/2-28 on both ends? Or am I just going to have to make a new endcap?
You can buy boosters that fit into the tube threads or the end cap. You'd, then, buy different pistons with the appropriate thread pitch to match the muzzle threads.

Did you buy a threaded solvent trap tube (w/ common threads) or make it to your own spec?
If you made it, you should be able to turn an adapter from tube female threads to booster male threads.

Not recommending either of these, but just for reference:
https://sdtacticalarms.com/product/booster/
http://www.ajguns.net/oc/9mm_booster
Completed Builds www.silencertalk.com/forum/viewtopic.php?t=79895
Burst Calculator www.engineersedge.com/calculators/pipe_bust_calc.htm
Silencer Porn www.instagram.com/explore/tags/silencerporn/
User avatar
YugoRPK
Silent But Deadly
Posts: 6318
Joined: Wed Apr 02, 2008 2:56 am
Location: South Carolina

Re: just tried out form 1 9mm, S&W MP9 won't cycle AT ALL with it on

Post by YugoRPK »

Putting the laughter in manslaughter
Post Reply