What are the current producers doing with the recoil system to make these? Recoil rod length? Spring coil count? Stock spring wire diameter or different? I have an old conversion by Volmer I think and it ejects but does not cock the hammer and I am looking to find some way to get it running. Thanks.

hmmm,
vector will be offering hk51s, and several of the usual hk smiths do them....rdts, orf, c. higgins, etc....
problem is that (i think) that the different mfg'rs of the hk51 have different ways of shortening the g3 bolt carrier and recoil rod.  so you'd prolly have to buy both together from the same mfg'r.

it sounds like the gun is short stroking.  check your ammo first, if its no so hot loaded (like commercial 308 rounds) that could be the cause.  military 7.62 ammo is hotter and your 51 could be tailored for that type of ammo for full blowback.
if thats not it, then you have two options: first, try a g3k locking piece...its got a different angle for the shorter barrel g3k and is supposed to unlock the bolt group a little earlier for the lesser recoil impulse on the shorter barrel g3k.
if that dont do it, and if you are brave, cut a couple of coils off the recoil rod til it don't short stroke no more.
hth

Vollmer 51's ran when they left Fred's shop.  Are you the original owner?

Vector is currently using a 'telescoping' recoil rod assembly with threaded stop pin.




I agree with mwc on the locking piece, check to see if it's a #18 (50°).

Not original owner but it looks new n ota scratch on it and the interanls were clean. The only markings on the locking piece is a W or An M not sure which way to read it. The recoil is one piece thats a little over 11" long with less coils than a full length recoil system. Gun cycled ejected and closed but left the uncocked.

So how does the Vector recoil work? Is the  stop piece inside the carrier cut shorter and the spring preload is acomplished by the rod portion that slides into the short tube at the rear? The spring preload takes up part of the rod length on mine.

On the one I have the carrier bottoms out on the spring when pulled fully to the rear and never reaches the buffer portion what does the vector bottom out on when pulled back fullyThanks.

What is the length of the Vector rod compressed?