New to me MK2 .25

[KevG]

could be well worth fitting a valve chamber extension (replaces valve end cap) and a shorter valve body and stem.
kevG

[Hobbyman2007]

That's the plan now Kev. I was using a top hat over the existing valve to act as an extension. What I didn't take into consideration was that the top hat would be forced in the opposite direction by the pressurized air. Completely negating the whole point of a balanced valve. I've got some 304 stainless on the way to make a new stem that will go straight through the end cap that I made from a 1/4" BSPP to #4 JIC fitting I got from the local hydraulic shop, sealed with an oring in the extended rear cap. In the first pic there's my new light weight hammer made from 7075 aluminum bar stock with an adjustable silent PIP and the short stiff spring.The second pic is the modified rear cap installed for testing. It's a work in progress and I'm getting there slowly but surely.

Ultimately, I'm after a quick lock time with easy cocking and able to reach the 40fpe.

[skagitmonster]

Have you not thought about a reverse valve and plenum ( valve chamber extension ) does away with a lot of faff , a slightly heavier hammer maybe but stock hammer can be used

[skagitmonster]

Adjust pip size to suit...8mm 8.5mm etc

[Hobbyman2007]

I'm not following the reverse valve idea. Do you happen to have a drawing or link?

[KevG]

think you will find aluminium far to soft a material for hammer.hammers need to be case harden.the sear contact on the hammer will soon chew up plus scratch were it runs along the trigger sear.
kevG

[KevG]

You cannot view this attachment.
I got great gains with this set
kevG

[Hobbyman2007]

I've been looking at a sleeve to press over the hammer for the sear wear. Option 2 would be to have it anodized. Jury is still out on that one. Didn't get much time to work on it today but I should have a couple of hours tomorrow after this evenings snow storm gets cleaned up. Late February and we've just got another foot of snow. That's life in northern Ontario , Canada.

[skagitmonster]

It's just a reverse sprung valve , does away with anything in the valve chamber extension, kev g s has a similar principal ,both work

[skagitmonster]

I did post a pick but where it's gone I have no idea .....I'm not used to this forum yet

[KevG]

I did post a pick but where it's gone I have no idea .....I'm not used to this forum yet

it's there now I have problems posting pics and ime admin😀
kevG

[Hobbyman2007]

I don't know if you guys have been told yet, what a bunch of enablers. Hahahaha. I really like that reverse spring set up. That would give me the max onboard air and give me the ability to adjust the preload on the spring.

I'm running some tests now and let me just say, this valve is EASY to open. I need to dial it back some. Getting over 1000fps from a 17" barrel at 200 bar. Looking at a solution to get the valve to close sooner. I'll post pics with dimensions of the valve stem later on when I get it sorted out.

[Hobbyman2007]

Here's a pic of the new valve stem with a sketch I used . I give up on the lightweight hammer. I just don't have the right springs here to make it work. I went back to the original hammer and inertia weight and a single spring with no preload , free flight/ slingshot hammer. Right back to 40 FPE with the JSB's even with the new shorter 17" barrel but much easier to cock. The valve stem is extending 8mm longer than the original shortening the stroke. Very fast lock time and the air release is a quick snap. Still waiting for a few parts but I'm real close to being  done with this one.

[Hobbyman2007]

While I'm waiting for the V block from RAW I figured I'd get a jump on a hole plug for the stock. I saw a few pics from what Stuart had done with a couple of his. Here's what I came up with. A short 24mm OD 7075 aluminum sleeve for the hole. Then a delrin cover that gets held in place by a 1.5mm x 15mm ID oring. I had a stainless screw with a swivel from some camera gear I had laying around that got screwed into the cap. Not the most elegant fix but functional. I wanted it to be counter sunk a little further in the stock but as you guessed it my glue set too quickly and that's where it ended up.