need help building my MA 2550 carbine…
…I am putting a B/A bulk fill on and I was wondering what kind of thread sealant would be best for the bulk fill thread components??? Also, prior to disassembling it, when fired, gas would escape around the breach and hit me in the face. Rob told me to hold the bolt handle down and see if it makes a difference…No it did not, so he said either the o-ring on the bolt probe or the transfer port o ring…Well, here are some picks of Roy’s valve and custom transfer port set up:
It is a custom made piece of vinyl tubing…perhaps some of you are familiar with this…I am not, this is my first 22/25xx platform. Do I need to replace this piece??? It is rigid, and no longer flexible, and I would imagine when it was new it was softer and created a better seal (please correct me if I’m wrong). Also, any info on the origin of this valve, etc. would be appreciated.
So again, what kind of thread sealant, and please advise on this transfer port vinyl o-ring thingy 😕
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I think your valve body moved rearwards bending that screw.
How do you have your valve anchored? Look at the back of the valve and see if the screw threads are imprinted there at 12:00 o’clock.
oh yes, my comment about the breech screw is that the TP seal you pictured requires the breech screw to ‘clamp’ the assembly together for a seal. That is the too much stress for the screw I was meaning. 🙂
Walter….
Is your hammer notched for the screw?
No, it is not notched, but it looks like the screw sits far enough in front of the hammer not to be hit by it…but I am glad you asked, perhaps someone will chime in because if I had to choose between air or that heavy hammer being the cause of bending the screw I would vote for the hammer????
80,
Is your hammer notched for the screw?
If you can grind a 1/4″ drill bit flat, install teh valve into gun with a piece of dowel or somesuch to hold the valve rearwards,
then use the tube to guide the drill and counterbore it about 1/16″ deeper after it cuts full diameter. Do the same on the barrel installed into the breech.
A TP done this way seals on the end and on the walls of the counterbore when it sees firing pressure pulse. Illiminates unwanted crumpling of the TP tube and undue stress on teh breech screw.
Walter….
Walt,
I have not had a chance to mess with the valve yet, but I wanted to test fire a few shots after I put a new o ring on the bolt probe (which did solve the air blasting out the bolt probe area…) And the increase in power was very noticeable. When I went to take it back apart again…I noticed the breech srew would not turn out easily (I knew I had not stripped it).
To my surprise the breech screw was bent! 😯 I noticed you said that air leaking past the tp can put undo stress on the breech screw…Well, it sure did put some undo stress…it bent the sucker. If there is any other explanation for this, please let me know??? Thanks
Okay, thanks for the info. I can’t wait to start messing with these. Good night.
OK, I got cha…misunderstood the question..no, a valve for CO2 will work fine in a gun using regular air …it’s the same idea..more air(or CO2) and faster.!the B&A valve in my 2240 is identical to the Mountain Air valve in my 2250..didn’t come that way, but they are now 😎 😎
If you use just the stock airtube on your 2250, and use CO2 you MIGHT get 5 shots out of it..I don’t think you had that in mind, did ya? just too small….why even bother??
No, no, I have a bulkfill tube, but like I said, depending on the shot count, I may forgo co2 and go right to an HPA like yours, or with the tank hanging down like a foregrip…perhaps even incorporate the tank in the buttstock with a braided hose…
As far as I can tell, when the valve is “modified” everything that can be done to improve airflow is done….more of it and faster 😀 😀 …..
If you use just the stock airtube on your 2250, and use CO2 you MIGHT get 5 shots out of it..I don’t think you had that in mind, did ya? just too small….why even bother??
Thanks for the explanation on the difference between HPA and PCP…I kind of figured it had to do with volume and psi. That brings me to the question of what is the difference with the valves. Does each application require a different valve, or valve internals, or does one work for all??? I am glad you posted the info on your gun because I want to weigh all my options out and decide which route I want to go with this. I am actually building a 2250 and 2550.
I kind of like the look of an HPA tank in a drop tank position like a “foregrip”. I also like the look of yours.
I wonder if I decide to keep it CO2 how many shots I can expect out of that 2250 tube???? Rob should be able to answer that one 😎 (I know the volume of air output in the valve will affect shot count…just looking for an approximation)
Don’t feel “long winded”, that is what these forums are all about. I love “long winded” people when I am trying to learn. I appreciate when people take the time to explain things when time is such a precious commodity nowadays…thanks again!
Joe
My previous post, along with this one, are in regards to information relating with a 2250 in .22 caliber……since your gun is in .25 caliber, it MAY or MAY NOT even be applicable, I’m not smart enough to know stuff like that..but I THINK it wouldn’t be different …other than you using heavier pellets and getting different fps numbers??? Anyhow, thought I should point that out, like I said, don’t know if it means jack-&_{T 😯
I too, am a big fan of the 22XX series..SO MUCH you can do with it….
With your self-contained air tube,,you have a PCP,but it is small (cc-wise) compared to one like mine , that has an external air source which is what folks call HPA. Your tube only holds enough press/volume for a few shots. My 13 cu.in. bottle holds 213cc )3000psi)..compared to say a Discovery which I believe holds 130cc (2000psi). that’s the difference..you get higher pressure AND more volume..My bottle has a built in regulator(1600psi) so EVERY shot is the same,( in theory) fps deviation is loooow because it gets same amount of air every shot! This is a GOOD thing..My TSS doesn’t have tha tso it has a bellcurve..low, then high, then low. Regulated, I still have a curve but it is almost negligible….if you’re looking for high shot count, the regulator ( and use of power adjuster-tlaking about Crosman here) will stretch ’em out.
I’m in the process of finding what pellets my 2250 likes since going to HPA..this is an exampe of how many shots you can get from even such a small bottle as I am using…..it amazes me…
Pellet-17.10gr Beeman Silver Arrows…..
Start press=3000 end press 1400..
0 turns out 5 shots avg. 881.75
2 turns out 5 shots avg. 849.50
4 turns out 5 shots avg. 883.66
6 turns out 5 shots avg. 848.50
Obviously, 4 turns out is “the sweet spot”
From there I set it @ 8 turns out and just shot it until I got down to 1200psi……got 33 shots Hi=810.72 Lo= 790.29 ( high deviation due to me shooting past the set point of regulator)
For all 53 shots (all on one bottle of air) Hi-893.95 Lo= 797.48 Average fps was 831.44. Sure, my TSS will get that many shots too (or more) but is like 2 1/2 times the air volume (490cc vs 213cc)..I am not impressed that I built it..I AM impressed with the performance of the gun. Note..I didn’t figure anything out..there’s a fellow on AirGunHome that showed/taught/explained everything to me and sold me parts that he made for the 2250..that made it possible for me to get this kind of performance..I couldn’t have figured all this stuff out in 10 years…
PM me if I can help….I DO get long winded sometimes, and I apologize..better to NOT do it here 😎
Packrat,
Thanks for the info and the advise. I believe it is a MA valve and bulk fill setup. I am going to work on it as per Walter’s instruction as he is the “guru” on this platform, if not all! Besides, it sounds like allot of fun, and if I mess it up, I could always get another valve. Speaking of other valves…I am hoping to receive an education on the differences. I am not too sure what the main difference is between the HPA and the PCP. I think you said that I would get more power and shot count with the HPA over the PCP…Please elaborate on the differences between the two.
I will most likely keep these bulk fill co2. I am more concerned with shot count and accuracy more so than power for the 22xx platform. However, any advise on what would be needed (tube and valve wise, etc.) should I decide to convert from the co2 is surely welcomed!
I really like these little pistols/carbines. I am no machinist, but I have an idea to piece together a nice custom stock for one in the not too distant future. I have already begun collecting pieces as I come across them 🙂
Hi there, I also have an MA2250B fro Roy…nine was great, but I wanted more power..did some tweaking and finally got it to shooting 700FPS, which isn’t too shabby, but ya know how we are about the mo’ power thing..I converted mine to HPA with a 13 cu,in, bottle trgulated to 1600psi..I now can shoot over 900 psi..BTW, mine is .22 caliber.
I just completed the conversion 3 days ago and am still testing pellets to find the best ones!!
Any how, just because the TP tube is deformed does NOT mean it’s too long..it may have been put in a little off square, which would cause it to buckle..The one in mine isn’t soft/pliable and I think it was that way when new…with just enough resiliency to compress/seal when breech screw is tightened down…it’s more than likely where you leak was coming from.. As far as sealant on threads-I didn’t use any..if you do develop a leak, use a wrap or two of plumber’s teflon tape 😀
The O-rings are supposed to be a REALLY tight fit going in to the tube, they are what’s sealing up the tube and keeping high pressure air from leaking out..
So, you’re taking out the valve that came in your gun and replacing it with a B&A?? I have one of each of those valves..on mine one performed just as well as the other in my 2240. Only difference is that Roy does streamline the piercing end of valve stem a wee bit,for better flow.(if you use CO2) I f you haven’t already, you need to get a DISCOVERY valve stem..and before you install it you need to “lap” in (just like you would do with int/exh. valves in your car engine) use a reversible drill and go slowly one way for 10-15 seconds, then reverse and go the other way for 10-15 seconds….do this 2-3 times..DO NOT pull with a lot of pressure on it, just a little bit will lap it in fine…and you use tooth paste for lapping compound..laugh if you want, but it is just abrasive enough to make the 2 surfaces fit together good, otherwise it will leak at the stem seat. Use the stock spring. (wash toothpaste out of valve!! 😀 😀 )
I have found “diver’s silicone lube” to work really good on seals and o-rings….hold the valve “square” to the tube with one hand and apply light pressure…using you thumbnail.. Make sure it’s not sharp!! and go around the edge, lightly pushing inward on o-ring to help comp”compress” it into the tube….little more pressure, go all the way around o-ring again.TYou will be able to tell when it’s far enough in that you can gently and slowly, push it the rest of the way down to where it needs to be. I think that’s everything, please let us know if ya run into problems, together we’ll get it worked out 😯 😯
Let me ask ya this..why go to PCP stle when it’s just as easy to go HPA, and ya ge a lot more power and looooong shot strings…..just curious… good luck and have fun!
Thanks Walter, I will get on it as soon as I have my house back in order. Into day 3 on a 5 day carpet rip out and laminate flooring installation. My guns are buried somewhere beneath dozens of boxes and tupperware containers… 😥
It appears the valve has been modified with a countersunk/concave face…so what you are saying is I am to eradicate this (go deeper) and make it a counterbore surface on the valve and barrel correct?
I’ve been meaning to purchase a digital caliber…now I have an excuse.
You got it!
a taper or angle along with a piece of tubing cut too long will result in a wedging into the air passage. You don’t want that. With my method the sealing is accomplished without encroachment on the TP i.d.
Try it you’ll like it 🙂
And yes a caliper is a definite requirement for sure.
You will be able to depth the two assemblies after you flatten the bores, add the two dimensions and add say 0.005″ and prep a plastic tubing to that length. BTW my favorite tubing is the drinking straws from Pizza Hut kids plastic cups. Ask for extra straws and you will be set.
Walter….
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How do you have your valve anchored? Look at the back of the valve and see if the screw threads are imprinted there at 12:00 o’clock.
oh yes, my comment about the breech screw is that the TP seal you pictured requires the breech screw to ‘clamp’ the assembly together for a seal. That is the too much stress for the screw I was meaning. 🙂
Walter….
Walter,
you are a genius! You know what they say about having extra parts left over when you put something back together again??? Guess which part was left over??? Yes, I forgot to pin the valve down. I am lucky that screw was there. If not, perhaps that valve would have blasted a hole in my head…At least you guys would have had a great way to remember me 😳
I am hoping to get to work on countersinking the valve and barrel over the next few days as per your instructions. Today I will be stopping by pizza hut for some kids straws….Thanks again.
Joe