Custom benjamin multi-pump. 25 cal

[GumpIsrael]

This may seem like a dumb question to the old timers.... but being that i'm stuck on multi-pump airguns I have to ask:  would it be feasible to buy a rebuilt 392/397 and have a .25 barrel made? I am aware of people who have converted disco's to .25 but I haven't seen anything about a multi-pump conversion. I would be willing to pay a good chunk for the breech and barrel conversion and I realize the valve would probably have to be extensively modified to provide enough pressure to get a decent fpe. But, to me ,it'd be worth it (if it's something that sounds feasible) if i can find professional tuners that would be willing to take on such a weird endeavor. Or if there is another thread similar to my question, could some please point me in that direction.

[longhunter]

No can do. The breech and barrel are soldered to the compression tube.

[Matt15]

http://www.gatewaytoairguns.org/GTA/index.php?topic=97509.msg911586#msg911586

I built this. I will be getting my steel breech within a week or two so I can get some chrony numbers and accuracy test.

[GumpIsrael]

http://www.gatewaytoairguns.org/GTA/index.php?topic=97509.msg911586#msg911586

I built this. I will be getting my steel breech within a week or two so I can get some chrony numbers and accuracy test.

Very nice matt! did you build your own compression tube or use one off another gun?

[Matt15]

http://www.gatewaytoairguns.org/GTA/index.php?topic=97509.msg911586#msg911586

I built this. I will be getting my steel breech within a week or two so I can get some chrony numbers and accuracy test.

Very nice matt! did you build your own compression tube or use one off another gun?

It was a crosman 1400 pump tube and it has a 7.25 inch stroke(I have a 6.5 inch stroke due to longer valve). Same ID/OD as a crosman 13xx tube.

[redlined_b16a]

Nothing is impossible,Im sure it can be done.Not saying its feesible or worthy.
Like others done custom pump tubes are the best route.

[GumpIsrael]

Sounds like you had your work cut out for ya Matt!

I'm gonna do some more research and do some pricing i'll post if it's actually a workable idea. First thing i'll do is look into getting a custom brass breech and barrel machined, because i'm fairly hopeful I can solder it myself. Famous last words: "How hard can it be?" Lol

[Matt15]

Sounds like you had your work cut out for ya Matt!

I'm gonna do some more research and do some pricing i'll post if it's actually a workable idea. First thing i'll do is look into getting a custom brass breech and barrel machined, because i'm fairly hopeful I can solder it myself. Famous last words: "How hard can it be?" Lol

I used

Custom work (Turning barrel down to 7/16, shorting 13xx valve front half, and 1.1" long valve extension) $150
.25 Mrod Barrel $50
Steel breech $36
.22 bolt $13
13xx parts $15
a bunch of 90 Mil spec O-ring from mac 1 $30
1400 piston, linkage, and pump tube $50
4-16x40 CP scope $60

Total: $400

What was expensive was the custom work. I did not have the tools to do it so I paid a guy on here do it for me.

[GumpIsrael]

That doesn't sound too hard on the wallet, matt! When I told my wife about the idea, she told me if I could keep it under a grand I could do it. I'm gon a try and stick wit brass (to keep it lookon lIke a stock benjamin), if not, i'll go the mrod route. You said ya used a .22 bolt, it still seals the breech and everything? If that's the case then I could probably get away with using a 22 bolt myself.
The thing that I think is gonna get me is all the machine work (rifling grooves and the breech being able to fit into a 392). But seriously, gotta give you props man, a gun like that would probably cost like 700 bucks if it were retailed.

[Matt15]

That doesn't sound too hard on the wallet, matt! When I told my wife about the idea, she told me if I could keep it under a grand I could do it. Since i'm gonna try and stick with brass, i'm thinkin i'll have to pay a lot more for machining. You said ya used a .22 bolt, it still seals the breech and everything? If that's the case then I could probably get away with using a 22 bolt myself.

Well, a M-rod barrel uses a #010 o-ring between the barrel and breech. The .22 bolt o-ring is small enough to go through the #010 o-ring and creates a o-ring to o-ring seal. It works great. 

[rangerfredbob]

Matt,

Is that $50 barrel from Crosman direct? I'm planning on doing something similar to yours but was thinking of the XL725 I think... haven't decided  yet.

[Matt15]

Matt,

Is that $50 barrel from Crosman direct? I'm planning on doing something similar to yours but was thinking of the XL725 I think... haven't decided  yet.

Nope. I bought it used.

[GumpIsrael]

Hmm... that sounds really good to me, I might be using an mrod barrel if machining a brass one looks too expensive.

[GumpIsrael]

Well, with these thoughts in my head I, and believe me they will stay there, I have decided to put this on the back burner until my funds are sufficient for the machine work. Especially since I just got a good deal on a PC77, so i'll be modding while I save for the .25 mod.