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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I don’t know if your referring to the one Cyg had or the one I have coming, but you may well be correct either way.

I bought it just to have something to play with, if I can get it shooting well it may become a loaner gun, or a gun I give to my adult daughter along with a pump. She already has the Glock 23 I killed the bear in the house with when she was a child and a old gray Colt SA 45 4 5/8 barrel and a house way the hell up in the mountains to shoot at. She has lately taken an interest in my PCP’s so it might be a perfect gun for her

I have been curious about the BAM for a long time, and from what I hear the Daystate parts do interchange on them.

As far as Chinese, everything Crosman is chinese, don’t kid yourself about MRods and Prods and all those springers they offer, some may have been assembled here, but the parts were made by the chinese. And this will be my first chinese gun.

They did have quite a following and this one has had a lot of money spent on it in the past getting a LW barrel and a shroud, and from what I learned Googling Bam 51’s it has about everything done to it that you can do to one.

I does 60 FPE the way it sets now with 32 grain EJ’s, so I might try slugs in it or I might detune it to Kings.

I like powerful PCP’s, I have no use for springers or co2 guns, I have modded my Royales and AF rifles about as far as you can go with them, so it was time for a new project.

One thing I will do for sure is take a aggressive wood rasp to that stock and refine it.

It for sure is a sows ear, first thing I will do is shoot it on a bright sunny day, set it in the direct sunlight and see if I can detect a sheen of silk shining off of it. 😆



No offense dude, but it Seems like alot of hassle for a Chinese air rifle? 😕 Maybe you should just Scrap that piece of shit 😈

It sure does look likeit doesn’t it?


quote roachcreek:

I just bought it off the Yellow and it sure looks like yours.


You bought it from me!
He already told me in a pm it was not! Although I was sure it was too!

I just bought it off the Yellow and it sure looks like yours.


The one you sold wouldn’t look something like this would it:


😯 Funny thing is the guy I bought it from said he wasn’t using it so he wanted to sell. I came here looking for cyg to ask a bit about it and talk about a trade for a .22 cal barreled one and after reading about the thing and what it can do can’t wait to get it and keep it! Thanks for doing such nice work on the gun I think I am gonna really like it.

Meanwhile I hope the new one works out for you.

Try boring a few holes in the valvebody screwin cap around the centre hole. The valvehead could very well choke the valve hole in that cap.

Hope this makes any sence. I converted my BAM to .25 a while ago and it did 24 shot’s at 65 ft.lbs. But sold it to what I kondof regretted ever since.



no pictures this time around….

i tried some different stuff to get the power up…

added hammer preload…added about 20 fps….but also brought power to max from the start…not what i wanted, as theres no powercurve to it…sped maxed at 752 fps with 42 grain EJ

bore out the delrin transferport and tried different sizes…dint change anything….speed still in the 700-750 but the transferport looked like it had taken damage…so i decided to make a new one….

WOW what a change…the new transferport featured stainless steel…whic is nice and strong, it had a collar in each end where the orings fit to seal against valvebody and reciever….that coller on the orginal is just slightly shoter than the orings are fat so it compresses the orings a bit sealing when you mount the reciever….i made the collar that mates to the valvebody longer so it actually goes into the valvebody…about 5mm, and in the other end where it mates to the reciever i made it slightly longer too…which means it comes really close to the transferport….first shot 872 fps still with 42 grain EJ that like 70 fpe….what a change…thats a jump of more than 100 fps, and the transferport is actually smaller than the plastic one i had made….but man is the rifle ever loud now, and it sucks air like you wouldnt believe it….1000 psi on 5 shots or so…

so now i had to tweak the valve return spring a bit to bring the air useage a bit under control….yeasterday i had allowed the return spring to stretch quite a bit more to lessen the preload on it…so i made a little bushing…speed came down to 86x fps…less than i thought i would….had hoped it would hit about 840 ish….

but now im about where i want it….and some hammer travel tweaking should be able to get me close to the goal.

i must say im impressed with the stiffness of the 16mm barrel, it will flex but it consistently pops right back t where it came…i tested several times, and with feeler guages…it just went right back….not sure it needs a barrel band….

for those of you who wonders how it works i grabbed some pictures of the B51 as i did mode the valve after all….i took off .02″….and popped in the original return spring that is really hard….but what i got my self is too soft…..still with the smaller valvehead…and stiffer spring the speed only went down about 50 fps….topping at 730 fps with 42 grain EJ….but it was much more consistent…producing a bunch of shots between 730 and 700 fps….but its not good enough….need more power 100 fps more and im calling it a day

during the valve tweak…i remember how much i hate that pushpin, allways such a pain to get out of the rifle because its not centered…making the tube just wanting to twist

enjoy the pictures which can be found here….

rifle is still not good….decided not do so much about the valve as im not in the mood to take it appart….

however i did get my breech riser finished, and theres no plenty of room for the 1″ shroud…might even be room for a 1.25″ tube

the long transferport takes it down from about 830-850 to 780 fps, prolly just need to open it up a bit more

valve needs some work though….gonna cut the delrin down in size, so it sould be easier to knock open….the B50’s allready got a delrin piece thats about way bigger than the hole it covering….so with that trimmer the force needed to knock it open should go down drasticly….hopefully improving power and shotcount….

well messed with it some more

read the pdf file about tweaking the rifle and thought i had found the thing that needed to be fixed….the trigger springs…someone in the pdf file on tweaks speak of replacing with lighter springs which would make less dragg on the hammer once released….

well i tried it, i even rounded the hammer sear a little…and might haven raised the power by 10 fps, not worth doing IMHO

next i found a spring to replace the return spring, and dang it…it made 1004 fps with EJ42 😯 thats about 94 fpe ! also very loud and consumed alot of air, i could feel it wasting air.

so i adjusted the hammer screw a bunch but no consistency, removed the extra hammer weight and still no consistency, was even a bit better with the weight…….but would be shooting at 960 fps…no real consistency still, but getting better…..but that kind of power and a 200cc tanks is just not a good combo

so decided to try limit it in the transfer port, and stuffed the tranferport from the original .22 BAM in there…it helped alot ! did a 15 shot string from 800 to 835 and down to 790 fps, pretty much where i want it, but as the pressure gets low its starts waisting the air getting louder and slower

im not sure whats going on…if its the transferport thats too small and letting air out too slow….or if its the hammer thats too heavy

currently i suspect the hammer to be too heavy, and hammer spring too weak

tank looks just like any other airgun i have messed with, wallthickness etc seems to be fine…i measured it long time ago and it is within safe margin, actually just a tad thicker than my AA410erb if i remember correctly….sorry i dont have the number in my head (or anywhere else for that matter)

valvebody is held in place, by a crosspin, 2 sidescrews, and one from the bottom, so even thgouh its aluminium that will stay in place for sure, i have not seen any sign of elongation of mounting holes…

the end cap is where i might worry a bit, its allso aluminium, with a coarse thread, i have tried filling is past the recommendet 200 bar…saw nothing….but maybe i should try measure it

for them to get and use the right steel should be fairly easy, its an industry standart, and calculations and tests have been done

reason i have not been filling to more than 175 or so is that im low on air in that tank….and been to lazy to switch to the 300 bar one(cant even remember if that one is full)

they might be worried of valve lock….since mine was having a hard time firing when the fill got close to 200…but i might also just have gotten a crappy one

next time the rifle is empty i will try measure it…and then see how much it streches during filling

Cyg, have you tried for a slightly higher fill to try and get a bell curve? I’m also interested in why the BAM has such strong warnings about not filling past 200 BAR. Is it down to the fact that the steel used in the Tank is not as strong as that used on other rifles? If so, do you have any safety worries?

so now it got it to do 10 shots from 175-180 bar fill where it stays around the 830 mark with EJ42 and ends around 110-120 bar….

not bad…but the old bammer could do 15 shots around the same number…but that would be with a 200 bar fill, so maybe this one can match that.

kodiaks are flying out of there at 930-950 fps, but doesnt get the same 10 consistent shots….its pretty much downhill from the get go.

i changed the way it seals in the breech, before the oring was on the probe, now theres an oring in the breech instead well actually the oring on the probe is still there….but thats just till i get the new probe made up

im not after max power…i just got a goal 😉

i wanna hit 800+ with 17-19″ of barrel and EJ42

with lighter valvespring im having a hard time finding something that is just a bit lighter like 70-80% of the current or something….i still want it to control the valve timing

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