362 .25 conversion

[Psipumper]

Getting started on this but it will be some time before I can complete.
I have a regular 362 and an anniversary 362 so I am thinking of converting them both to .25
Originally I was going to just build extra parts while converting the standard model and just go through the AE leaving the barrel on it stock  but now it is on the chopping block. So now there is only 2022 of them I suppose. I haven’t even shot a pellet in it .
I had pretty good results with my first 362 in .22 caliber and these two will share the same modifications with some changes to suit the .25 caliber.
The changes will be a slightly larger valve volume and the barrel will be shorter and extend just past the stock. The breech hole and bolt enlarged for .25
In .22 the 362 was good for over  23 fpe without testing any higher so should expect these to be near that.
I didnt think through the anniversary edition breech enough. I ordered a Baker aluminum breech I was going to use but the production number is on the steel one. I could ream the hole in it or modify the aluminum one . Probably ream the steel one that is on it to keep the number intact.
Although originality is good, I feel like an anniversary edition in .25 that shoots dime sized groups at 30 yards is better.
Photo is steel breech reamed for a.265” bolt along with the insert I made to support the loading port.

[Mzq284]

Very cool, I finished my 25 conversion last month. They make a decent 25, that anniversary edition should be sweet. I took a different path, if I were to start today I would do it the same as you. I still have to mod an old Crosman stock and fit it up. I put my first 362 in a 114 stock that I slendered up, this one will be the same. Then I'll have a pair of retro pumpers. The one mod I did that I found worthwhile, and will do to the original 362, was to replace the breech screw with an 8-40 from Ace hardware. It really solidified it. If in doubt, do it, you won't be disappointed.
My 362-25, the original 362, and my 3622.

[Psipumper]

Very cool, I finished my 25 conversion last month. They make a decent 25, that anniversary edition should be sweet. I took a different path, if I were to start today I would do it the same as you. I still have to mod an old Crosman stock and fit it up. I put my first 362 in a 114 stock that I slendered up, this one will be the same. Then I'll have a pair of retro pumpers. The one mod I did that I found worthwhile, and will do to the original 362, was to replace the breech screw with an 8-40 from Ace hardware. It really solidified it. If in doubt, do it, you won't be disappointed.
My 362-25, the original 362, and my 3622.

Nice collection. I do need to do something with that 8-40 screw . Seems I will make major changes to every part on a build and have yet to address that.
Seeing that 3622 reminds me that I
Have an idea to buy the tube and try to adapt it to the 362 pumper to increase the pump stroke using a 392 pump lever I have laying around.
If you would, could you measure the overall length of the 3622 tube?

[Tack Driver 10]

My 3622 tube measures 22 5/8".

[Psipumper]

My 3622 tube measures 22 5/8".

Thanks
That tube is 2 inches longer. I will do some measuring. Would seem to be enough length.

[Mzq284]

If you can't get the tube, what about using a 2100/2200/766 valve, they're shorter than the 362/13xx valve and make good power with the shorter stroke of the 2100/2200 family? I know you're looking at a larger volume valve, but putting more pressure in the same valve equates to more pumps.
Another thing to think about is how are you going to dump all that extra air? Mine uses the stock hammer spring and without a spring guide for more preload and added weight in the hammer, it would retain air over 8 pumps. I used a 5mm Allen bolt cut to length and polished, now it dumps 11 pumps without retaining air. You can go with a heavier spring, but mine is hard enough to cock and with the light valve spring I have to cock the gun before I pump or it burps out the barrel.

[Psipumper]

The valve will need to be as large as possible . To get the valve to 30% of the barrel volume may be impossible. The stock valve is only 1.5 cc , more suited for .177 caliber. I haven’t tried to bore a max sized valve but have gone up to 2.2 cc. Not a fan of the skeleton type valve but for .25 cal it may be best. Will take a few more pumps to up.
I had a theory about headspace as a percentage of the swept volume being a factor in efficiency at higher pressures. Part of the need of the longer tube .
I have got quite a few things to improve the hammer strike .
Along with a .200” transfer port, the retained air should happen at extreme pressure at the structural limits of the 362.
I may have been a little conservative with the power estimate at 23 fpe .
Revise that to 33 to 40 fpe.

[Mzq284]

The valve will need to be as large as possible . To get the valve to 30% of the barrel volume may be impossible. The stock valve is only 1.5 cc , more suited for .177 caliber. I haven’t tried to bore a max sized valve but have gone up to 2.2 cc. Not a fan of the skeleton type valve but for .25 cal it may be best. Will take a few more pumps to up.
I had a theory about headspace as a percentage of the swept volume being a factor in efficiency at higher pressures. Part of the need of the longer tube .
I have got quite a few things to improve the hammer strike .
Along with a .200” transfer port, the retained air should happen at extreme pressure at the structural limits of the 362.
I may have been a little conservative with the power estimate at 23 fpe .
Revise that to 33 to 40 fpe.

Sounds like you're getting serious! I was after 600 fps with 27gr pellets and got close enough for conversation. . I could've gone further but didn't want to get too wrapped up in the project. Looks like I might be going back in, depending on your results. This is going to be interesting!
I modded my piston to be adjustable with an oil wiper, .166 transfer port and barrel port. Exhaust passage is huge, don't remember the diameter but the Marauder stem just covers it, and the corners were blended into the port. I would've liked to go
3/16" on the ports but didn't want to get crazy with it till I tried what worked in .22. I may rethink that.
A picture of my piston:

[Mzq284]

The breech screw in my gun. I still have to stop shooting it for a bit and blue the screw.

[Psipumper]

I ordered the 3622 tube. The extra length will allow the use of the extended stroke and also will be able to add a 1.5” longer valve as well. The two will still share some common parts but the anniversary edition will still use the original tube    and be completed first. The other one will be on the back burner for some time. I may complete my overdue 392 conversion first. I had gotten to the soldering part and lost interest.
Photo of .22 FX barrel on my original 362. The .25 will be the same but won’t require epoxy between the carbon and barrel.
Other is the incomplete 392.

[Psipumper]

362

[Mzq284]

I had thought of doing a 397 to 25 conversion myself. I'm curious as to how well it works. I bet a steroided 392 would make some serious power! Cool projects, thanks for sharing those, you have my full attention!

[Psipumper]

I had thought of doing a 397 to 25 conversion myself. I'm curious as to how well it works. I bet a steroided 392 would make some serious power! Cool projects, thanks for sharing those, you have my full attention!

The 392 had some extreme power before. During some testing of the upper limits of it , made 45 fpe .
Got 1130 fps with CPHP pellets.
Didn’t reach my goal of 50 fpe though. Longer barrel would have done it.
Definitely will be a better with a longer more accurate 25 barrel.

[Habanero69er]

45fpe out of a 392 is pretty impressive. Interested in seeing how your latest project turns out, Charles.

[Mzq284]

Hey Charles, how is your air rifle project coming? You've got me curious, I'm chomping at the bit for more info

[markjs]

A really cool project. I don't see how one of these guns is hitting over 30 foot pouunds, seems fishy to me, but I could be wrong.

If it were me, I'd leave the anniversary edition alone, just cuz of it's collectable value, but it's your gun.

Will be interesting to see the results.

[Psipumper]

Hey Charles, how is your air rifle project coming? You've got me curious, I'm chomping at the bit for more info

I have been studying the 392 pump  fit to the 362 tube. It may be too difficult with the smaller tube diameter .625 vs the larger .778 392 tube. I may try to modify the 362 tube to take advantage of the full stroke available using the 362 linkage. Working on some other design details and drawing up parts.
I have made new hammers and pivot end plugs. Spring guides, hardened pivot pins. I had the adjustable pistons done but have now opted to remake the link end out of brass .
Of note, the hammer spring is much longer than the stock one . This would be very nice in the 3622 pcp version with a hammer adjuster to tune.
I had no problems dumping air much before with a lot of room to increase spring pressure to higher power levels. So in .22 caliber, I was getting 23 fpe and could have went to 25 or more by increasing the hammer strike using a 2.0 cc valve.
The pumper math says with a 3.7 to 4.0 cc valve would be over 30 fpe in .22 caliber. Although requiring 23 pumps to get there.
We will see but I once said that the 362 with its long pump stroke and sturdy pump linkage could set all time highs for the 13xx platform.

[Mzq284]

Cool, thanks for the update. I wonder how the 392 would work as an ACP 25 cal?  I have a 397 that could be a donor. I have enough projects that it will have to be an unanswered question for a while.
Thanks again for the update, keep us in the loop

[Psipumper]

Cool, thanks for the update. I wonder how the 392 would work as an ACP 25 cal?  I have a 397 that could be a donor. I have enough projects that it will have to be an unanswered question for a while.
Thanks again for the update, keep us in the loop

No doubt it could be done with the 392.
I hammered out the protrusion at the end of the tube slot. 1/8 inch more stroke. The pump cup goes further past the end of the slot so TIG welding a piece to the tube to shorten the slot could be done for more. 3/8  more stroke x 10 pumps = 3.75” or half a pump more.
In the photo, you can see where the slot was stamped out and then stamped again to cut the slot longer. The anniversary edition 362 tube slot is cut in one step. I think crosman has updated their tooling to cut the slot since launching the 362. Too bad they cut it a 1/4 inch too long.

[Psipumper]

Had a few other projects to attend to  but getting back on this project.
I had a machining mistake on one of the valves and accidentally removed some threads . Ordered a few spares from Crosman.
The ones they sent for the inlet half did not have the threaded hole to attach the trigger housing.
I was able to bore these out deeper to get more internal volume. Measured the newly machined assembled valve at 3.5 cc .
Stock size is 1.5 cc. Since the missing threaded hole I welded a threaded boss to the tube and counterbored the trigger housing to fit. I also pinned the valve.
I have a few more details and assembly to complete.