Saturday, August 21, 2010

Rebuild of Joe's Crosman 454

Sidetracked from the 118 magazine when buddy Joe asked me to fix a leaky Crosman 454 semi-automatic BB pistol. This is a second variant due to the loop on the CO2 piercing screw at the bottom of the grip--which means it was made right around 1980. The gun uses a 12 gram CO2 cartridge housed in the grip and it holds 16 BBs. The BBs are held linearly above the barrel. A spring loaded plunger pushes the BBs backward to the breech where one is loaded with each trigger pull. The trigger is essentially double-action only with a pull that ranges from about 5-1/2 to 6 pounds of weight.

Joe told me the CO2 was leaking from the end seal.

The right side grip is clipped to the 12g CO2 cartridge and pulls right off. The left grip is held by two screws.

Joe was right. The end seal is almost non-existent.

Removed the rear sight.

Four screws hold the frame together.

Screws removed, the right-side half lifts off.

If you want to remove the barrel, there's a small screw on the underside just behind the muzzle. It retains the front sight--which in turn holds and centers the muzzle.

Of course, the safety ball bearing fired across the room when I lifted that right half. Some things never change. I scrounged a tiny replacement 3/32" ball bearing. (Nick probably still sells bags of tiny bearings for just such occasions.)

Detached the hammer and trigger springs.

Small set screw retains the barrel in the valve. It's a 3/32". Just unscrewed it a turn.

Removed the valve anchor bolt in the left side of the frame.

Pulled the trigger pivot pin, wiggled the valve around then lifted off the hammer. The entire trigger, linkage and hammer assembly comes out as one piece. It's straightforward.

Slid out the smooth bore barrel. If you look at the breech end of the barrel carefully, there's a circlip in a groove that acts as a locater stop against the valve.

The BB follower is plastic. Look at that spring! That's exactly what I need for my Crosman 118 magazine. Think Joe would notice if the gun was gravity fed?

Some valve pics. Rear. The silver protrusion is the valve stem that gets struck by the hammer.

Top. The screw holds a spring that pivots the BB shuttle (for lack of a better term).

Screw and spring removed. The shuttle slides right out. It picks up a BB from above and as the trigger is pulled, a transfer bar pivots the shuttle into alignment with the breech. It's a really simple, elegant design. Note: There are no seals on the side of the shuttle-- just an interference fit in the valve body.

Removed the cap from the front of the valve.

Valve spring and stem pulled out.

Ah, here's that bad cartridge seal. Unscrewed the threaded retaining ring.

Used a dental pick to work the crumbling seal out.

Underneath is a standard 38T/C piercing pin and screen filter.

Here's what the crumbled pile used to look like. Crosman's part # for the seal is 38-128. It's still available and used today in the Crosman 357 pistol.

Reassembled: Screen, piercing pin, seal, retaining ring.

Replaced the cap o-ring with one that looked similar in nitrile. Didn't replace the stem seal. It actually looked pretty good and it operates with 900 psi on it--that really helps keep it closed.

Greased the shuttle's sides to help pivot smoothly and seal.

A couple views.

Oh, I lubed the valve stem seal with a little Crosman Pellgun Oil. The rest of the reassembly was pretty uneventful. I did refinish four or five of the visible screw heads, removing old screwdriver marks and rebluing. The gun gassed right up and fired 60+ shots without any hiccups. I'll give it back to Joe and he can finish giving it a shake down.

If I ever find one of these (and for the right price) it would be relatively easy to turn down 8" of 1760 barrel and shoot this with 0.177 cal lead balls. I'd imagine that the accuracy might even be pretty decent but probably not the velocity.


joeengineer said...

Would McMaster Carr have that elusive spring?

derrick38 said...

McMaster probably does have one and if I hadn't been in a hurry, I'd order one (or more likely 20). Part of what I enjoy most about the blog is learning different skills. I've never needed to make a spring before, though, I sort of have a vague understanding of the basics. So, this seemed as good a time as any. Besides, music wire is a cheap way to spend half an hour learning something new.

Doug Campbell said...

Thank you for taking the time to show us the rebuild of your 454 and where to get the seal. I've had one for years but it has a gas leak at the cylinder end so I never used it. Now I'll get it working again!

Doug Campbell, Galt, California

Anonymous said...

Great blog,where can I order a few CO2 cylinder seals to get rid of the leaking problem...

derrick38 said...

order the seals directly from Crosman.

Anonymous said...

Did mine with a standard plumbing washer from Ace hardware. The flat kind that go in a kitchen faucet. Works great.

Steve Ignat said...

A friend of mine just gave me one of these today. It's in really good shape but, has the same problem with the seal. I may fix it and give it too my son. I'm wondering what velocity these originally fired at.

derrick38 said...

With the Crosman copper-plated steel bb's, the gun can peak around 375 fps for a few shots on a brand new CO2 cartridge. Most shots, realistically, will be down in the low 300 fps range, especially when firing rapidly. Substituting lead bb's for steel will bring the fps down into the 260 fps range.

Steve Ignat said...

Funny you mention lead bbs, I fire them from my co2 200 exclusively and you're right, they are noticeably more accurate than the steel variety.
I did find a possible reason for the low fps in these 454s... Notice the loading pivot is cylindrical, while the breech is squared and the beginning of the barrel is faced off square as well. I haven't taken any measurements yet to determine whether it would block entry from the feed-tube, but I think its worth looking in to.

Unknown said...

@ Steve Ignat

concerning your idea of the face of the barrel to the loading pivot. I own a 454 and i'm alwasy trying to get more power from airguns. So i stripped my 454 and had a look at the mechanism. You are right, the barrel leaves a considerable gap at the top to the loading assembly! I faced off the barrel with a grinding wheel (8mm diameter, sorry for the metric sizes, i am german ;-)) to correspond with the diameter of the loading pivot and leave a relatively tight seal. Also there is to remove the little clasp, that holds the barrel to the valve assembly, to get the barrel deeper inside the valve. As expected, there are problems with feeding the BBs, so you have to grind off quite some material inside the feeding tube, to get the BBs further inside the valve and get them around the now further inside reaching barrel end to drop into the feeding barrel. Do this with a approx. 5mm dia. milling tool with a long shaft to reach the end of the feeding tube inside the valve assembly. As i had the gun in parts anyway, i shortened the valve spring by approx. 1mm, turned down the valve stem at the point where the gas moves to the upper part of the valve and into the barrel by half (just behind the valve seat), to allow better gas flow. The results are OK, but nothing to write home about. Velocity is (with steel BBs) around 480 ft/s, with lead BBs 420 (!). I expected more from a 7.5 inch barrel. True .177 will not feed reliably, .175 will. The precision with .177 is great, but if every third shot is missing a bullet it is of no use. Maybe a rifled barrel of .173 (like used in the German Haenel rifles) turned down to the "straw barrel" diameter of the 454 might be an option, but i have no time to do this work. Anyway, a nice project, i enjoyed a lot. Thanks for the idea!

Unknown said...

forgot to say....

the gun with the new configuration (velocity wise) is shooting now 5 inches high with the sights all turned down. Not sure, if this is what i want :-)

magccsniper said...

an easy way to increase the velocity is to put a piece of wire on the hammer spring and twist it or if you want to lower the velocity use a flat blade screw driver to stretch between the coils just a very little bit then add the wire to tighten it and raise it up a little i can keep my crosman 1600 (same internals as the 454 and and uses the same seal as the 357 and possibly the gas block as well)at 300fps with swings in the area of about 10 to 15 fps depending on how fast your shooting and temperature and yes it does fatigue the spring but if your not going for the highest muzzle velocity you it will last you just fine

Anonymous said...

Just found this thread. Thanks for posting it. I'm going to use it to rebuild my 454 which I've had since I was a kid - assuming that I can still get the seal part.

John R. Siehl said...


I am having a hard time getting the retaining ring to come loose. Does anyone have any suggestions?

derrick38 said...

Heat and/or a penetrating oil.

John R. Siehl said...

Thanks! I first tried oil -- to no avail -- and then heat. That did the trick. Now I just need to find some seals and I will be all set.

Shutterbug said...

Just found this blog. Is it necessary to completely disassemble the whole gun in order to replace the seal around the puncture pin?

Shutterbug said...

I just found your blog. Is it necessary to dissemble the whole gun in order to replace the seal around the CO2 puncture pin?

Anonymous said...

Just remove the retaining ring with a long wide bladed screwdriver.

Dale Frey said...

Finger Tighten the retaining ring. The screwdriver works when needed to remove the ring, but don't use the screwdriver to torque it ...

Anonymous said...

any idea why my trigger return is weak when a CO2 cylinder is in the gun, but is good when there is no air?

Anonymous said...

Does anyone want to purchase one? I have a this same crosman 454 in pretty good condition never used for over 30 years. Clearing out attic.