SMK PP700 SA tuning question

[Phil B]

Been playing with a used PP700 I bought.
It’s now Huma regulated, was set at 90 bar

No matter how much hammer adjustment, it wouldn’t go over 3.5 fpe.

So I stripped it out, set it to 100 bar, same story, but now 4 fpe.

The transfer port is backed out on the breach, the reg is fitted properley and can breath to atmosphere.

I’m a bit lost for ideas, all I want is efficient as possible at 5 fpe.
Any thoughts welcomed!

[--ped--]

try it at a lower pressure could be valve lock but at 100 bar you'd think it would have enough strike as it has a 200bar fill
problem with s/h is often you don't know what has been altered

[Phil B]

It was set lower before (90 bar) and made 3.5 fpe. I bought it used but the cylinder and reg are off another and checked/resealed by me. It has a breached original reg and is lovely and consistent at least at these lower powers on the chrono.

If I really wind the hammer spring up, the power drifts down again, could that be a clue Ped??

[krisko]

How hard is to pull the trigger when it is cocked, the reason I am asking because maybe someone fitted weak hammerspring. If too easy that’s the clue. Fill only 100, 110bar in the cylinder to check/ prevent valve lock. and verify what the pressure reducer is doing
If your reg is set too low for a pistol power will be low, if too high, power will be low again when you fill the cylinder all the way up.

The us models have bigger hole right behind towards the pellet, everything else failing I would drill the Tp out carefully the way that you can still use the restriction from the top as designed later.
Maybe you have a sliding breech off a uk .22 that’s why it is struggling to make power. Yours is a .177 right?

The best tune on these is high reg and high hammer spring and lots of choke. You work out the choke as it drifts up towards the low pressures. It will be quiet and high shotcount if you get it right.

[Phil B]

Thanks chaps, useful. Yes Krisko, it’s .177 cal.

[--ped--]

the porting may be restrictive but I have had very little to do with tuning these
I bought one just to test seals on and eventually to make a small ratter but as yet have only turned a longer barrel for it
I did turn a 177 barrel for a mate and he was getting 5-6 no issues but his was previously .22
a soft hammer spring could be the cause but why would power fall when the tensioner was fully wound up -shot count yes as it wastes air but you'd think the power would remain