Need Tips for Reducing the FPS on the Hg-196

[Whengunswentpew]

Hello.
I need to reduce the fps on my HG-196 Mauser for a project. Don't suppose anyone knows of an adjustable valve that will fit it or of any other ways i can reduce it's power.

[Adolf Hamster]

suppose i should open with the caveat that gas pistols aren't something i mess with too much, so these are at best pointers until someone with a bit more practice at this sort of thing comes along.

 

however you could look at a couple of areas.

 

firstly is shorten the inner barrel, pretty simple and more importantly temporary (ie you can reverse it again by swapping back)

 

the other is softening the spring on the rocket valve, this is what @Wo1f did to my kwc makarov when i bought it and i can confirm it's done wonders.

[Whengunswentpew]

Nice, thanks for the advice! 

[Skara]

Try a wider diametre barrel too, reduces some of the pressure

You could cut the hammer spring, but I wouldn't do it unless I had easy access to spare parts. Best thing you can do, though, is to hand it to a decent tech

[Whengunswentpew]

I have a friend who can make a new spring if it goes wrong, so i'll be sure to give that a try. Fortunately part of the design for this project involves shortening the barrel so I need to get a new inner barrel for it either way. 
Thanks for the advice, you've been a great help.

[heroshark]

Being a nbb is more straight forward I think the barrel is proprietary , not sure if it has any similarities to any other available barrels. A softer hammer spring or tweak the existing one would be my first goto and the easiest method. Made this a good few years ago with the carbine version still fires over 350fps at this length. 

[Whengunswentpew]

The carbine version is what i'm starting with as well. I'll have it back this weekend (left it at my dad's place before the lockdown hit) so i can check the barrel then and I'll see what I can do about that spring. 
The overall goal is to get the FPS below 350 if possible so I can use it at my local cqb site, last time i put it through a chrono it was around 470 on green gas so i'm hoping with some modifications and white gas it'll run below 350.
Also your mauser looks brilliant, nice work!

[heroshark]

Ta ,sounds about right .Think it was about 380-70ish still at this length. Other advantage of a lighter hammer spring is an easier trigger pull where you still thinking of keeping it longish?

[Whengunswentpew]

Funnily enough, a lighter trigger pull was another goal of this project. As for the length, I'll probably shorten it to be slightly longer then the standard pistol version. Can't be certain till i have it back but it's definitely going to be a lot shorter.

[heroshark]

should be good then as long as your not under voluming a long barrel you'll be fine.

[Whengunswentpew]

Thanks, I appreciate the help and I'll let you all know how the project goes.

[Wo1f]

If you’re planning to shorten the barrel I’d start with that. No point getting the FPS where you want it and then chopping the inner barrel in half and having it shoot low. Once you’re happy with barrel length I’d look at the hammer spring as @heroshark suggested. If the gun isn’t a gbb then it doesn’t rely on the excess gas cycling the system so there’s no real disadvantage to a lighter hammer spring. If they don’t make one, I believe you can just shorten the ends of the original very slightly, but I’d wait for someone more knowledgable than me with NBB to confirm that. 

[Whengunswentpew]

There's a shop near me that sells springs of pretty much every size and strength so i was planning on removing the spring from the gun to take it that shop and find a weaker one of the same length.