140 Cont'd.

[Doc Sharptail]

After 3 weeks of working with the 140, I'm beginning to arrive at some conclusions. Figured I'd better carry on with it here, as it's more nuts and bolts, than pictorial...

I like wood a lot on an airgun, especially a pumper. This 140 likes it's stock castle nut to be run up tight. It seems to make the gun more consistent that way. Pump pressure seems to run up faster with a tight stock nut.

The self cocking valve (take a hint blow-back pistols ) is pretty neat. Trigger pull on this gun seems to level out after 6 pumps. I can go 6 or 20, and the trigger weight is the same. It is heavy at 6 pumps, but not quite to the point of un-manage-ability. I learn to compensate, and get used to it. Getting a shot off takes a little longer than a hammer system, but like I said, we learn to compensate.

Gun was definitely not made for a delrin flat top piston. The one I had in there saw fairly light use, and rarely exceeded 5 pumps per shot. The length of the compression stroke is easily better than twice that of a 13-XX. No wonder the tube generates heat. At any rate, after 150 shots, that delrin piston was pretty burnt. I have a home made brass piston in there now. I had to pull a Bob Sterne and put an intake hole in the tube for the tighter-toleranced home made unit. It seems to be working well.

I've been doing a bit of reading, through a link provided on the other forum. Apparently, some later variants of this rifle had a bbl set screw through the top of the breech. Looking at my breech, there doesn't seem to be a lot of steel there. Perhaps these later variants had a heavier breech? Just wondering if this is something I should attempt... I still have it in the back of my mind to try and adapt a current SBK kit steel breech to this platform, among other things. According to the same source, the earliest variants of the 140 did not have the self-cocking valve. I wonder if that means a hammer and valve stem system?

Here's the link:

http://www.scribd.com/doc/27115892/C...rvice-Manual-1

The intermounts I have on it aren't the greatest, but for now, they work well enough for my purposes.

I think the thing I like the best about this rifle is that I simply cannot put it down

Regards,

Doc Sharptail

[rsterne]

AFAIK, the earlier variants didn't have a hammer and "knock open" valve, but some manual version of the spring returned cup.... Never had one to know how it worked.... I agree that a Delrin piston is a waste of time on a 140, you need a metal one (I used aluminum)....

I'm surprised your trigger pull doesn't go to the moon over 10 pumps.... I had several 140's plus a 1400, and on all of them the trigger pull was pretty much linear with pressure inside the valve.... Count yourself lucky on that one.... I reached a high of 845 fps with 14.3 gr. pellets at 20 pumps on a modded 140, so the potential is there.... Unfortunately, the trigger pull must have been 20 lbs.... (Ok, maybe not quite, but you could easily lift the gun with the trigger and have it not even close to firing)....

With considerable work you can fit a 2289 style valve, hammer, and trigger group to a 140/1400 tube.... I got 800 fps at 20 pumps using one.... My .22 cal "Uber-Pumper" incorporated an extended version (extra middle section) and I was able to achieve 900 fps with 14.3 gr. pellets at 20 pumps.... Here is a photo of the valve....



I don't have all the details any more of the mods required.... I do remember that I used a "breech band" to hold the trigger group in place and anchored the valve with an extra set-screw on the bottom.... It was moved back so that the distance available for the hammer travel was "normal" for a 2289.... It would be just a matter of measuring and figuring out how to do it.... I don't know if a 1400 trigger group could be used.... I used the pistol-grip style 2289 one.... However, the 2260/Disco trigger group would fit, and that means a Marauder trigger group should fit as well.... That would be my choice if I were going to repeat the exercise....

Bob

[Doc Sharptail]

I did have a steel breech on it briefly- (just out of curiosity) with the breech band holding everything together. I did not have the screw into the valve pin guide, and had some wildly fluctuating velocities as a result.

At present, I have a detent spring from an electrical transfer switch, in behind the sear block. This is a lengthy, open coiled, medium light tension s/s spring. I may have lucked out with this spring, and it's levelled off pull weight.

There appears to be a cut in the top of the tube for a hammer pin. It looks to be factory original milling to me. Not at all surprising, given Crosman's penchant for across the line use of parts interchangability. It could even be a later variant replacement tube for all I know...

Gun's very consistent with the Exact Heavy from JSB. I'm really going to have to source these somehow, and get a couple of tins in before hunting season opens.

I wish sometimes that I had more time to put into these things. Work really gets in the way of projects, but that's the reality of things for now...

Regards,

Doc Sharptail