Mutant Reg question... How low can you go...

I know that almost no one will share my goals but I need to reduce my collection and have a mutant that I’d really like to keep rather than sell as part of the lot.

So,, the lowest I can get the reg in stock configuration along with HST to keep the shot string over the chrony decent is just shy of 19FPE.  To make this one work going forward, I’ll need to get it down to 12 fpe (or reall close).

The basic reg adjustment will go a tad lower, the HST will also go a tad lower, both (or any combination) just yields crazy irrdicate results so I’m left with changing the reg, with shims and/or washer restacking (dont see any other option to achieve goal). 

anyone gone this route on a mutant reg??

Yes, attempting to make a major power reduction by only reducing the hammer strike will drive up the extreme spread.  It is because the valve is only barely being knocked open, accentuating any minor variations in hammer friction, poppet "stiction", etc.

If you can't reduce the regulator enough to reach your goal, you will need to restrict the transfer port.

I get all that. Even with the reg all the way down and the HST adjusted for best results, I’m still not getting near the consistency I was getting at 28fpe...

I guess my question is around reducing the reg further. The adjustment on a mutant reg is literally a vented and threaded cap on the end. I’ve hit the limit.  If there are no paths/know attempts to redo the washer stack on this reg, then my next attempt will be to sleeve out the plenum to reduce it’s volume. I’m not to the point yet of reducing the TP as I think I’d need to tap it for a helicoil or something along that line. 

The basic tuning of the gun, is the relationship between the hammer strike energy and the valve return spring. There balanced to each other, if you change the hammer strike energy, You have to make a change to the valve return spring to maintain the balance of the tune. hth

Jeff, I think you will find shrinking the plenum to be a tedious way to reduce the power level.  Also bear in mind what that does is deliberately creates a major pressure drop during the shot cycle, and that will not be good for efficiency.

Your initial plan to change the Belleville washer stack to achieve a lower setpoint is really the best option in terms of consistency and shot count.  Next best would be the transfer port restrictor.

BTW, what James says about the valve spring is important in an unregulated rifle because it plays a role in the self-regulation.  That is, the varying lift and dwell as the reservoir pressure falls which is desirable to produce a reasonably stable velocity over a wide pressure range.  However it is of no significance in a regulated rifle provided you have an adjustable hammer spring.  In fact, you could remove the valve spring altogether and the only downside would be that it may be difficult to fill from zero with a hand pump (but no problem with a tank).  

Thanks all, didn't want this thread to die without a response. I will be readjusting the reg but I'll be going back to 130 bar and will try it for a while but more than likely sell it if/when I'm comfortable speaking to its performance.  Really hoping to focus on 10m and 100y ( both for personal fun, not competition) and rekindling my FT participation (minorly competitive).  

Hi Jeff, I'm guessing that after you reduced the hammer strike, you were getting more of a bell curve, with a greater spread between shots.  If you replace the valve return spring with a lighter spring, to compensate for the lighter hammer strike, I think you can flatten your string back out. It would be a bummer to sell a gun , that you can still setup the way you want.