Air Gun Home :: View topic

Old Lampy · Member

Winter is back so no range time this week. I spent some time on a new project. Instead of buying a Crosman 3622 or a Beeman Chief I thought I'd spend 3X as much building my own.
I have a few odds and ends in my parts stash from the Crosman pumpers I've tinkered with over the years. Anticipating my need to build, a couple months ago I ordered some 3/4" OD seamless steel tube. I have a 1377 and shoulder stock that will donate it's pistol grip, trigger group and hammer. One of my projects will donate a steel breech kit or I'll make up a new one. I found an exhaust valve in the parts stash so it was time to start...

I started with the fill end. 3/4" Aluminum round stock turned down to fit the ID and drilled and tapped for a Foster fitting. It will be held in place with two 1/8" roll pins.

I reverse engineered the 1377 tube for all the mounting holes and slots.

I removed the check valve from the exhaust valve and drilled the inlet hole slightly oversized.

I assembled what I have so far and pumped it up to 1000 psi, it didn't blow apart so I'm taking that as a sign to continue.

AirGunEric · Site Admin

Go 'til she blows! Wink

Old Lampy · Member

The fill end is done, two roll pins hold the plug in the end of the reservoir. The Foster connector is sealed up.

One solid roll pin along with the #8 screw that holds pistol grip on should be enough to hold the exhaust valve in place.

I made up an new steel breech for the .25 cal. Lothar Walther barrel.

Assembled and ready for it's maiden voyage to the range.

I pumped it up to 3000 psi and headed to the range. Everything worked on it's first time out. It's not a tack driver but I wasn't expecting it to be on day one.
Once I got to the range I verified it still had 3000 psi in the reservoir then proceeded to sling lead. It is pretty much lobbing pellets like a mortar. I'll need to add a heavier hammer spring and a way to adjust it.
It fired about 50 pellets before the power dropped noticeably, way more than I was expecting from an approximately 100 cc reservoir.
I'll take the Chrony with me for the next session to give me a better idea of where I need to go with this.

I have a list of the things to address,
1. Add a pressure gauge to the reservoir.
2. Make the hammer spring adjustable.
3. Make a barrel band to reduce barrel harmonics.
4. A forestock at some point.

AirGunEric · Site Admin

Good work!

Any idea if you are getting any sort of barrel movement when taking a shot as a result of no barrel band?

Old Lampy · Member

Old Lampy · Member

The .25 project has been a struggle. I solved all the problems by spending money. I found a Beeman Raider in .25 at a local sporting goods store.
The Raider shoots about the same as where I ended up with my home brew PCP. Shooting 1 inch groups at 25 yards and shot gun patterns at 50 yards.
I switched the .25 barrel out for a Crosman .22 barrel and made the hammer spring adjustable. I spent the morning shooting over the Chrony and figuring out where the sweet spot is. I found that 2500 to 2600 psi is a good level to pump it up to. I can get 15 to 20 consistent shots from that fill averaging 850 fps shooting Crosman Premier 14.3 gr in the cardboard box. With that fill I'm getting 1" groups at 25 yards and 2" groups at 50 yards.
This project is working great in this version now it's time to dress it up with a fore stock.