SpudFiles

Got myself one of these, the cheap and cheerful variation of the HW 40 PCA made of the finest Chineseium. Shoots about 410 fps with a 7.8 grain Daisy flatheads, very pleasant.




Naturally I took it apart the plan is to convert it to 0.22" and have it shooting as close to 500 fps as I can manage.



Look at that tiny transfer port, just 2.5mm diameter - less than a third of the cross-section of a 4.5mm barrel in terms of area, shameful.



The valve is of an unusual design in that it is pulled rather than pushed open, and is already somewhat balanced, but there is always room for improvement.



Original barrel alongside an externally battered but internally clean Crosman 2240 barrel I obtained, will probably keep most of the length and cover the excess with a faux suppressor.

They are surprisingly good for the dollars spent. Not a power house, but fun and fairly accurate.

Any reason to switch over to .22 caliber? Will the longer barrel/heavier pellet create less noise? I've had a beeman p17 for a while now, but shooting it in my backyard is kinda noisy.

They are surprisingly good for the dollars spent.

Given the build quality I'm honestly amazed at how little they go for.

Not a power house

Give me time seriously though if I can have it shooting .22 at the same velocity it was shooting .177 I'll be happy man.

Any reason to switch over to .22 caliber?

The same as it ever was - MOAR POWER! I'm not a paper puncher, prefer making holes in stuff, and .22 does more damage.

Will the longer barrel/heavier pellet create less noise?

For the same volume of air, it should give greater volume for expansion and cut down a little on noise with all else being equal.

Yep i would rather more impact then FPS any day.

Might have to start a .22 project next year...

Never updated this, what I had done was bore out the transfer port to 4mm and it had made no measurable difference to velocity for 0.177" pellets so I decided a 0.22" upgrade would be a lot of effort for limited gain.

Did turn a .22 barrel for one of these. Despite the fellow wanting it at stock length, it was still fun to shoot. 8) Good use for a spare 2240 barrel.

Nice. Speaking of 2240s, I have a used one on the way, perhaps a sub 500 fps big bore pistol a la Quackenbush is on the cards after all.

jackssmirkingrevenge wrote:Nice. Speaking of 2240s, I have a used one on the way, perhaps a sub 500 fps big bore pistol a la Quackenbush is on the cards after all.

Mmm .25cal...

I had given the original P17 in this thread away but acquired a new one and thought I'd give it another go, started with the following modifications:

1) cleaned up the valve stem, installed a harder o-ring and drilled out the transfer port to 3.8mm from 2.5mm

2) added a Delrin sleeve to the chamber to reduce volume and increase compression

3) machined an old Crosman barrel to fit at 9.75"





Here are the results:



Incremental increases in power except for the increased compression that actually reduced performance, contrary to some results reported elsewhere.

My original intention was to convert it to 0.22" and rather embarrassingly that's what I thought I was doing with the long barrel, in my mind it was a 0.22" I had in the scrap box and I didn't bother checking

I did however have a spare Crosman 2240 barrel and machined it to fit, here it is between the original and the long 0.177" barrels:



Test data for the 0.22" compared to the original 0.177":



25% more energy and pretty consistent.

Some final touches, I threaded the barrel to take a 14mm CCW threaded muzzle adapter that would make most airsoft accessories compatible:





I milled out the slot in the lower frame so the adapter would fit when open but of course any sort of accessory would have to be removed for every shot, so it's mostly there to stabilize the barrel in the frame, and it adds a certain je ne sais quoi to the look too ;D

Ok, this data was from a springer.
Found on internet .

Transfer ports .
Dunno if adds anything .
But here it is .

Doc j wrote: ↑

Thu Jun 29, 2023 7:15 pm

Ok, this data was from a springer.

That is from this study of springer ballistics which is an interesting read, but not really applicable to pneumatics because in a springer it is affecting compression ratio so transfer port volume is critical, more so than flow.