Saturday, November 7, 2009

Fixing the Crosman 622, Part 2

This is one of those posts where I'm reminded how much I have to learn about working on airguns...

I set up the receiver half with the valve and tube in place.

Carefully aligned, I spotted for one of the cross pin holes with an end mill.

Then I tried to drill through before reaming to 1/8"...disaster! The tube hole started getting oblong as the drill drifted towards the outside of the tube...

I forgot to clamp the piercing assembly in place...if I had just put the piercing guts in and clamped with an empty CO2 cylinder it would have stayed put. But I didn't. At least I caught it before I was all the way through.
This highlights why I buy "beaters", guns that other guys have given up on. If (when) I do screw up I haven't caused some horrible historical loss to the world supply of collectable airguns. Chances are anyone else repairing it would have swapped out a valve assembly that didn't have a big chunk out of it. At least that's what I tell myself as I weep my self to sleep at night.

So now what? Well I do have this hole in the underside of the tube...

I reamed it to 3/16"

Spotted through the valve body to the piercing assembly.

Then removed it and drilled down shy of the gas hole and reamed to 3/16" for a slip fit (not a press fit)

Of course that dowel pin is a little long. It should provide some extra insurance for the tube and piercing assembly.

Ground to fit inside the housing.

Here's how the spring goes on the feed pawl.

Small end against the bushing.

That screw, which I thought wasn't stock, but is, in place.

Finally I returned to the reason for getting into the gun...the spring that actuates the magazine index...that is where the end goes. You cock the gun while carefully keeping all the parts together with your hand then use a screwdriver to bend the long end of the spring under that boss.

Here's another view.

Otherwise it goes together in reverse of disassembly. Use a pin to hold the trigger in place before you put the housing together and screw the trigger pivot screw in (pushing the pin out).

Well it works! I've shot through two CO2 cartridges so far and it held gas for three days in a row.
I'm getting 380-390 fps with 14.3 grain Crosman wadcutters which is about the same energy as the manual's quoted 375 fps w/ 15.5 gr. pellets. It is possibly one of the most fun air rifles I've shot. You can shoulder the rifle and "blam, click clack, blam, click clack, blam..." You get the idea. Maybe I'll work up the nerve to try porting it and using a heavier hammer spring someday for more velocity but as a plinker it's perfect.

Thursday, November 5, 2009

Benjamin Marauder Baffle Modification

Several of the first .22 cal Marauder owners had some accuracy problems traced back to the pellets clipping the baffles in the shroud. The early baffles have 0.247" holes--fine for .177 caliber pellets, but a bit on the close side for the .22 cal--unless everything is perfectly concentric. Apparently, Crosman has fixed the potential clearance issue on the new .22 rifles. Many shooters have found that the early .22 cal guns will benefit by opening up the holes in the baffles to about 0.280". This does not seem to increase the gun's discharge noise at all.

I've had no pellet clipping issues with my Benjamin Marauder, nevertheless, as I was going to be away traveling with the rifle, I thought I'd eliminate the possibility. It's such a simple job, I'd recommend it in a second.

As always, step one is make sure the rifle is unloaded. It actually took longer to download the pics than to do the modification.

Remove the fill cap that covers the Foster fitting.

Find a 5/64 allen wrench and loosen the two set screws on the barrel band.

Pull the barrel band off the front.

Unscrew the end cap from the shroud.

Tip the buttstock up in the air and the o-ring and followed by the four baffles will slide right out. (If they don't slide out, it's no big deal--just go to the next step).

Grab the shroud and unscrew it from the breech.

You'll feel some slight resistance from the o-ring on the baffle mounted on the muzzle.

Slide the shroud forward off the front of the gun. If your baffles didn't fall out earlier, use a wooden dowel rod and push them out.

Personally, I doubt that this final baffle could clip the pellets. It's so closely centered on the muzzle and a snug, press-fit, I just don't think that it could be far enough out of alignment to make pellet contact. If you don't want to drill this one out, that's probably just fine.

Appears to be covered in lead dust.

If you want to remove it, a 7/16 open-end wrench placed over the barrel helps to remove it. I gave the wrench a smack from a small dead blow hammer and the cap popped right off.

A lathe, drill press, hand drill, maybe even a tapered reamer, would probably suffice to open the holes. I used the Taig lathe with a 9/32" drill bit in the tail stock.

Each plastic piece took about 10 seconds.

The aluminum end cap took almost 20 seconds.
Reassembly is in the exact reverse: Install the press fit baffle on the muzzle first. Hand pressure alone should seat it. Mine clicked as it bottomed into place. Slide the shroud back over and thread onto the breech. Re-install the baffles. The large open ends face the rear of the gun. Drop in the o-ring and thread the shroud end cap down. Finished.

While I was tinkering, I figured I'd clean the barrel, too. 9/64" allen wrench removes the bolt.

There's a small bushing on the bolt.

Pulls right out the back.

I very carefully pried out the small o-ring that seals the bolt nose. This was a pain as there's minimal working room in the magazine opening.

Cut a piece of brass hobby tube to fit into the bolt hole.

Like so. This will ensure I don't have to clean up JB Non-Embedding Compound from the inside of the bolt channel.

Cleaning rod goes right through. The brass tube is not a press fit. I simply held it in place with my hand as I worked. Patched the barrel clean then cleaned out the o-ring groove with a nylon bristle bore brush followed by the dental pick and a the corner of a cleaning patch. Reinstalled o-ring (more fun) then lubed the ring lightly with a diver's silicone grease and called it good.

Lubed the bolt with a dive grease and reinstalled the allen bolt/bushing. Almost forgot to mention, you can just see the screw on the top rear of the breech. It's got a spring loaded ball on the end that puts pressure on the bolt. Screw it in or out to add or subtract pressure on the bolt. Adjust to your liking.

If you don't feel like messing around with the baffles in your rifle, Crosman will simply send you the new parts if you've got an early model. It should take you about five minutes or less to install them.

Tuesday, November 3, 2009

Fixing the Crosman 622, Part 1

Well I got started on fixing the problems with the Crosman 622.

The valve with the stripped out mounting holes and Helicoil stuff.

Drilling the mounting holes out.

Just deep enough to kiss the bottom of the hole.

Tapped #10-32 Helicoil (which is larger than #10-32)

The helicoil loaded in the insertion tool.


The helicoil in place.

The original holes are #8-32 I think, but I was able to go to #10-32 no problem except that I had to turn the heads of the button head cap screws down. I used Stainless screws because that was what I had on hand...

In place.

I discovered another small problem, although I doubt it will effect the functioning of the slide.

With the Halves screwed to the valve I noticed there's still a bit of a gap...

Easily pressed closed by hand. I checked and one of the frame halves is tweaked slightly so that it's not flat. There's no good fix for that. It's not a huge deal if I get the whole tube&valve mounted securely.

Checking to see how much room I have to work with for pinning the valve parts together.

I think that this is how I'll pin the valve & tube together although I may make the pins go in horizontally. That way I can assemble the valve & tube connected to one of the receiver halves which should keep everything aligned more or less. I'm taking my time as screwing this up pretty much would wreck the valve body. I'm open to any and all input in the matter...