[fortjp500]

A couple days ago I started working on an Rhop mod for my SVD and as I was firing it I noticed the bbs would drop out of the barrel at like 50 feet. So I chronoed it at 100 fps with .36 which is very low (normally 300 fps with .36). So I think maybe I just need to file down the rubber more. I do and nothing changes. So then I put in my original bucking (with no rhop) and chrono. It reads 170 fps with .36 (hopup turned off). I relubricate all parts and refire. same thing. I remember a long while ago I would teflon tape the cylinder head to increase fps so I inspected it. There are deep scratches going from the rear of the cylinder head to the front. I believe this to be the cause of air escaping. Any thoughts on how to fix this because no replacement parts are available. I havent tried teflon taping it yet. I know this is the cause (90% sure). I own JB Weld maybe apply some into the grooves and then sand it to be flush with the outer diameter? Any thoughts?

 

[chachaseeds]

First test the compression inside the cylinder by firing the rifle with your finger on the cylinder head nozzle (to prevent air from escaping). The piston should either move forward very slowly or not at all if you don't remove your finger. If it slams forward, then you know there's a problem with the compression of your cylinder.

Then, test the overall compression of the rifle by firing the gun with the cylinder head nozzle inside the hopup/barrel assembly to imitate the position the rifle makes while firing, cover the end of your barrel with your finger, and test compression again. The piston shouldn't be able to move forward/move forward quickly until you remove your finger.

If your rifle passes both these tests, and the issue persists, then it's probably because the cylinder head nozzle isn't going far enough into the hopup unit/barrel.

Also do you have an older SVD w/ a 400 fps spring or the new one with the 480-500 fps spring?

 

[fortjp500]

newer one, it normally shoots 475 .20 gram bbs.

 

[fortjp500]

it is difficult to test compression because of the muzzlebrake and the loading nozzle both make it impossible to test.

 

[chachaseeds]

Well, if there are deep scratches, that's probably where the air is leaking out from. I would just get a new cylinder head, since teflon probably won't cut it. You could try JB Weld though.

 

[fortjp500]

Good news. I JB welded the outside and sanded it flush and replaced the bucking and now I'm shooting 400fps with .36 bbs. I think my old bucking was the problem plus the scratches on my cylinder head.

 

[chachaseeds]

Good news. I JB welded the outside and sanded it flush and replaced the bucking and now I'm shooting 400fps with .36 bbs. I think my old bucking was the problem plus the scratches on my cylinder head.

Congrats!!!! 400 w/ .36's sounds good for your 2nd gen SVD. Do a shooting test or something, I absolutely love SVD's.

 

[Scooter16]

Hi i dont mean to jump in but im having the same prob with my l96
Just got a new nozzel and it is still crap
No compression have tryed teflon tape and nothing
Have a l96 pdi hop
Mad bull 6.03 barrel
Guardder h bucking
Any advice would help so much as its sending me mad