I sold my b51 and got a b50 gotta vent a bit
and i really regret it !
i had converted it to .25 and it had a short 19″ barrel pumping out 830+ fps with 42 grain EJ, it was smooth and funtioning well
sold it…..
got a b50 in .22, from day one there has been problems, on a full fill it would only do about 400 fps with jsb ! and the bell curve was terrible…generally they should do about 28-32 fpe, the rifle had arrived cocked…so i assume it has been cocked from day one !
the the hole in which the cocking arm slides has been drilled oval by the factory so theres quite a bit of play
2 orings where squished, 1 in the transferport, and one in the check valve
check valve died on fill number 10….they use a piston in the QC nippel…when filling this pop out of the QC and is stopped by the airfilter, no problem if you only pump up the gun, but filling from scuba pops that piston out too hard, and the airfilter got messed up and….so i had to make a fix…the oring in the check valve died somewhere between fill 10 and fill 20….giving a slow leak….put a quality oring in there and all is good…my b51 was the same…only took a little longer to fail
barrel was a tiny bit off to the left, loosen some of the set screws and that fixed that
i got a new hammer srping in the mail pretty quick from the dealer…which raised the speed to about 600 fps…still not quite enough
got a hint from a tuner of the B50’s saying to try remove the screw holding the safety, and the speed went to nearly 900fps, so it was clear theres a vacume forming behind the hammer….after doing the mod so you can adjust the hammer screw from the outside it settled down at about 42 fpe with EJ not too bad…and the bell curve alot better, but great.
today the .25 barrel i ordered from LW arrived, first the .22 barrel had to come out…and BAM has changed how they mount the barrels…in the old days it was 2 orings and glue, not so today….today its glue and a pressfit barrel that is pretty darn stuck on there good…
i heated it up and i saw the glue come out and burn off…but still barrel was stuck…the reciever was starting to glow it was that hot…and i decided to cool it down…then tried heating it once more, and that apprently did the trick the barrel came loose….but the bluing had suffered badly…..
and i got .25 machined to fit…added 2 setscrews at the top of the reciever so i dont have to glue the barrel in place
the valve got the transfer port enlarged, the endcap drilled in a couple of spots, and the valveseat was enlarged just a little bit too
the reciever is allready from the factory drilled out to .25, i plunged a reamer through just to make sure….mounted the barrel and shot some kodiacs…..875 to 930 fps….not really impressive, considering its a 24″ barrel.
i left the barrel 16mm OD for now, and it freefloats very close to the tank with ever touching it….but im going to add a riser and a shroud to it, once i have solved the question of the missing power….
it might be the valvestem it self and the delrin….as on my old b51 the valvehead broke off…and i made a new one, byt heating up the stem and removing the hold plastic leftovers…then heating it just enough that it would melt into the new delrin piece, i might not have pushed the pin as far into the new delrin piece, and there for ended up with a valve that can open further, making more power….
ohh another change they have made is to the hammer…the spring guide used to be a loose insert, it is now one piece with the hammer, only a big deal if you want to lighten it
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its the new square head cut…you like it im not sure if its a keeper or not
messed a bit more with the b50
i cut off a bit of the barrel, as i had reamed it too large and unable to get the oring to seal on the probe
i drilled a smaller transferport just to see what would happen, as it slowed the setup down a bit, something in the order from 880 to 850 with kodiak
it just a bit of the front of the hammer whith gave a bit longer travel=more space to run up some speed…this took the kodiak into about 900 fps
then i made a spacer out of brass to put between the spring and hammer to add a bit of preload as well as a bit of weight this took kodiacs into 940 fps, and EJ42 did 836 fps just ever so slightly above 65 fpe…but this is still with a barrel thats 3-4″ longer ! i would have thought it would have been easy to get to about 75-80 fpe especially with that heavy pellet.
the only thing i can come to think off that could be wrong is those cheap ass crappy springs the chinese uses…maybe the return spring is too hard, and is closing everything too fast, its very quiet shooting for the power so maybe its starving for air?
Cyg,
Is that a new hair cut? Didn’t realize you had black hair 😛
how i was going to make the breech riser is simple…
i take a piece of pipe with same OD as the tank….then choose the wallthickness for how much you want to rise it all…
once the piece is cut out, i mill the inside with a 1.25″ roundnose mill i made my self, that should make curvature of both inside and out 1.25″ and then its just to drill the holes for screws and tranferport
the screw in the cocking arm has to be extended to reach down and grab the hammer but thats all
this is the rifle i sold…
has riser and carbon shroud, spitting out EJ42 between 800 and 830 fps for about 60-65 fpe, and for that kind of power it is surprisingly neighbour friendly, and no its not me in the picture….
what happens is the hammer is creating a vacume behind it, without the screw the air can be sucked in through that hole….therefor less vacume….
i tried to drill a hole through the hamme to counteract this….it removed a bit of weight, but didnt change, the power…forgot to test with the safety screw in place
im baffled at whats keeping the power back with this rifle….its 99%% the same as the .177 b51 i had, except for the transferport which is a tad larger, yet it is making much less power.
gonna try look into it today
WOW Cygnus A LOT of headaches on that sucker! sounds like your getting it sorted out though and it is shooting pretty good! REALLY interesting on the safety screw slowing the hammer down!
Going to be really cool to see how you shroud that thing too.
Post a pic or 2 of the work in progress…
Jim.
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I’ve been playing with a .177 B50, and I just replaced the valve spring. The original looked like it came out of the front suspension of my Suburban! The spring I used in it’s place was from a spring kit I picked up at the local Big Box store. Approximate specs are: free length, .94″, OD .417″, wire dia. .047″. Seems to have flattened out my curve while still giving me good power even with a smaller transfer port. I’m also using the lighter hammer spring, unlike you, I’m not after max power :-). Only downside to the lighter valve spring so far is the hammer needs to be cocked if you’re filling from zero, not an issue once there’s some pressure behind the valve. HTH.
Dave