Factory tuned, the .30 Crown with 600mm barrel comes set up to push the 44.95grn JSBs at 850FPS. That isn't supposed to be the tuned maximum at all though. I do believe that velocity was picked though because, at least at some point in time, that was what people felt produced the maximum accuracy with the combination of pellet, liner, etc out at 100 yards for competitions like EBR and RMAC. I should also add, my Crown runs 80 food pounds with the 50grn .30s, and that is the factory tune.
So no, your performance figures aren't normal. There are a wide variety of possible things going on here. The most obvious is that, having turned up your reg, you have too much pressure on the valve and the hammer can't knock it open. Part of the reason I think that is because, when you adjust your reg, it usually needs one shot to show its accurate new pressure and several more to "settle." Assuming your chrono isn't playing tricks on you, that high first shot suggests to me you turned your reg up more than the gauge showed, and so the lower plenum pressure allowed that shot to be higher.
The question is twofold: how do we go about testing that hypothesis (or figuring out where you are) and how to tune to maximize or at least increase power? (preferably while getting a less crap shot string than that)
There are a wide variety of guides out there on how to adjust the little internal screw to actually max out the HST. If what you want is more go-juice, that is the place to start so that when your hammer adjustment wheel is set to max power, you're really giving that hammer all you can.
There are a variety of different ways to tune your rifle from here to max out power, and what I'm about to recommend is FAR from the only way, but it is a way. First off, check to make sure you have one of the "newer" crowns with the AMP regulator which can be safely turned up AND down when pressurized. FX posted a serial number which was the cutoff of the old reg type which had to be degassed in order to be turned down. Also, when turning the reg down, I think FX says you should do no more than a quarter turn and then take a shot to empty the plenum and relieve pressure so the reg will sit at its new (lower) set pressure.
Anyway, so, assuming I'm correct your reg pressure is too high, assuming you have the newer AMP reg, and having maxed out your HST turn your regulator down a smidge (quarter turn if that is in fact what FX recommends and my memory isn't failing me) and take two shots. If the second shot is higher than the first, you indeed are getting valve lock. Turn your reg down another quarter turn, and keep going. What you should find is an arc where as you REDUCE plenum pressure you see an increase in velocity until you level off and then start to lose power again. This will form a bell curve if graphed, the top of which is called the "knee."
Once you've achieved max power, head off to the range and start shooting groups. Use your HST to dial back the power from there, keeping track of what velocity produces the best groups. The general consensus is that the mid-high 800s produces the best accuracy in the .30 with the JSB 44 grain pellets. (someone please correct me if I'm wrong) However that doesn't mean your particular gun, barrel, pellet, atmospherics, etc produces that for you. So test carefully and pick your preferred velocity.
From there you want to optimize your tune for velocity consistency and shot count. Remember that "knee" I mentioned above? What you want to be is on the slightly-less-hammer-force-then-required-for-max-power side of it. This is how you waste less air, produce less muzzle turbulence, have maximum velocity consistency, etc. Picture the bell curve of performance again, which every regulator pressure and pellet will have a different bell curve. You want to be on the part of it, just below the peak, but which is still relatively low slope. This way tiny changes in reg pressure will have the minimum impact on your velocity. You want to be on the low-hammer-power side of this because that will minimize your air use being both more efficient and making it so there is less turbulence at the muzzle.
There are other things you can do for even more power, including a heavier hammer and a high pressure reg to go with it. You should be able to get more out of your crown without doing that though, so I've not covered it here. I believe Chuck has a guide on his findings playing with this posted on this forum if you go looking.
Whew, that was a lot of typing. I hope all that was helpful and made sense. Feel free to fire away with questions. Someone better at explaining things than me will probably be along shortly with a simpler explanation.
