Crosman 600 Restoration – Part 2 of 3

[WyoMan]

Reversing the order of disassembly (somewhat) I’ll install the valve in the tube first. The valve goes in from the front and needs to have the front and back halves loose (o-ring uncompressed). Also, make sure the breech gasket (square o-ring) is removed from the tube:


The back half of the valve needs to be located for the two retaining sleeves:


Install the retaining sleeves with a 6-32 screw. I’m using a 2” length so I can hold it better. Getting them both started and working them in at the same time with some light oil is probably a good idea:


Sleeves need to be flush with the tube…shown here with the breech gasket installed:


Now I can tighten the front half of the valve with the spanner tool (shown in part 1):


Next up is the hammer and cam ring installation. The inside of the hammer needs a dry lube and the outside needs something similar to moly. I also polished the cam ring and rounded the leading edges:


Slide the hammer into the tube from the back and place the cam ring in the slot like this:


Now the cam can be rotated and slid on the hammer – the square part of the smaller ring needs to be in front:


The tube goes into the frame from the rear. Positioning the breech gasket at about 2 o-clock (position) avoids the gaping cross pin hole. Once the gasket clears the hole then align for the cam ring:


Slide the tube in and stop when there is about one half inch remaining. The pawl needs to be installed next and rotated forward before the tube is all the way in:


Align cross pin holes and install the spring, buffer and pin:


Next up is the trigger group – here are the old parts:


Aside from the crusty old lubes everything except the link looks good. The link will be replaced with the top one... spare parts to the rescue again!


Rethinking things, I decided to soak all the trigger parts in some penetrating oil and move on to the slide group next.
Slide group parts:


The slide group goes in from the rear. Some grease on the spring will hold it in the recess while you try not to lose the detent ball. Start the slide in the dovetail with the spring and guide in the recess. Then press the ball in while you move the slide forward to capture everything in the dovetail. If you lose the ball bearing, a 3/32” from your 13xx or 22xx safety will work!


Back to the trigger group…I installed the components in the following order: Trigger w/ spring, Hammer Sear, Trigger Sear, Link, and then Stop Roller & Stop:









The cam and feed arm install at the same time. Two set screws (8-32) go in the same hole (one top of the other) and locate the feed arm on the cam - where the recess is drilled. I lube the cam with moly and then slide it thru the cam ring and feed arm. It’s sometimes trial and error to get the first set screw into the drilled recess:



The remaining parts are pretty simple: The barrel, the follower and knob, the magazine spring, rear cover and sight, and the grips. The rear sight has a tiny ball bearing for the “click adjustment”. Tiny as in “tiny” chance it will be found if lost. I keep it in a parts bag, on a magnet, or in the gun!


Finished:



Restoration completed... up next are mods… Part 3

Part1:  https://www.gatewaytoairguns.org/GTA/index.php?topic=121809.msg1181445#msg1181445
Part3:  http://www.gatewaytoairguns.org/GTA/index.php?topic=121811.0

Wyo

[Hare splittin]

Very nice restore. Better than factory. Especially like the ceramic coat.

Did not know there was so much inside these. Those trigger springs look like they would be hard to come by.

Saw one of these in a pawn shop w/ box asking $225, and I think it leaked. Never got serious about it, but became intrigued w/ semi-auto pellet pistol. Don't make them like this anymore.

Thanks for the concise, detailed write up.  A very good tutorial.

[Rob M]

thanks for this WYO , just got a 600 , first time.. it came with the box and works perfect.. But like you i need to tinker some.

[Roboslug]

WYO, I'm glad this thread popped up again.  I can't thank you enough for the details on it.  I've resealed two 600's since November.  The first one, rebuilt in May, still gets 36 - 38 shots per Co2 cartridge with around 1,100 pellets so far. 

Rebuilding the 600 isn't difficult, just very daunting and tedious. 

Roboslug

[Rob M]

silly question , aside from the top set screw , what else retains the barrel?

[WyoMan]

Thanks, guys.

Rob, that's not a silly question... nothing else retains the barrel other than the 10-32 setscrew on top. And as such, the barrel has a tendency to get shoved forward.
When that happens, you'll get even more blow-by out the feed arm gap and, of course, a loss of power.
This occurs (in my experience) most notably when a pellet gets skewed (jammed) in the breech.... i.e. the pellet acts like a hammer on the breech.

Ideally, the breech end of the barrel should be flush with the frame.
Feeler gauges can get you close enough by setting the barrel / feed arm gap to .002" go, .003" no-go.

Wyo

p.s. you can add more setscrews on top if you don't care about the "keep it original" thing 

[Rob M]

thanks wyo.. Ill be adding a new barrel with that knowlege tommorow.. The gun , given the time it was designed is an amazing feat of engineering and planning.. I cannot beleive crosman doesnt bring this back , even if the main frame was a polymer .

[WyoMan]

I agree 100%. And regarding the frame... it's the 60's version of polymer... zinc, aluminum, magnesium, copper... i.e. monkey metal so be gentle with the old gal 

Wyo

[Rob M]

hahaha , also true.. pot metal.. Question , since i still havent done a teardown , what actually causes the hammer to return to the cocked positon? i know  the twisted steel acts to cycle the rds, but I dont see a blowback assembly in the pics?

[Roboslug]

 ...but I dont see a blowback assembly in the pics?

There is a bleed hole in the valve body that diverts gas to the hammer.  You'll see when you disassemble the gun. 

[Rob M]

makes perfect sense , thanks for posting the diagram

[WyoMan]

Exactly, and expanding on that...The hammer cavity travels inside the turned down section of the valve and is sealed to the valve with an internal 014 o-ring:




I don't have a pic, but there is a vent in the back of the valve (just below the valve stem) that pressurizes the sealed hammer cavity when the exhaust valve is opened... i.e. blowback.
There is also a really small vent (.020") that is forward enough to vent the internal pressure (hammer cavity) when the hammer is rearward in the cocked position.
Should have taken more pics....

Wyo

[Rob M]

thanks.. hopefully ill get the courage to see it all soon 

[Roboslug]

My first 600 runs fine, but I just had to check the barrel/feed arm gap.  About 0.005", oh my.  I loosened the screw and tried to push the barrel back unsuccessfully.  I suspect it is seized in the frame the same way the tube was in the frame when I rebuilt it. 

Any ideas as to how to loosen the barrel?

Is it worth the effort?

Roboslug

[Rob M]

mine moved pretty freely , but to get it moving , i needed to grab the very tip of the barrel with a set of pliers, VERY gently.. with an 9 inch barrel i was getting 398 today with 14.3s .. slower than I expected , need to get in there and lube the action , maybe stretch the hammer spring a hair

[Roboslug]

Rob,
Check Wyo's other post:

https://www.gatewaytoairguns.org/GTA/index.php?topic=121811.0

He shows a different buffer (name?) for more spring preload.  I think a washer(s) might do the same thing.

Roboslug

[WyoMan]

edit... while I was posting, Floyd and I are on the same page with the hammer spring,,,
Rob, yours is not too far off the mark. There are some valve mods I did in part 1 that may also help... not sure because I didn't do the mods one at a time with teardowns in between.
But regarding the hammer spring... when you get it out I think you'll see that shimming is a better approach than stretching...



Floyd, If you really want to get the barrel to break free when all else fails... remove the 10-32 barrel setscrew, remove the cam and feed arm, tap the muzzle end of the barrel with a rubber mallet or use a hammer with a wood block on the muzzle. hth...

Wyo

[Roboslug]

Rob, thanks for the plier idea.  Wyo, thanks for the reminder to remove the feed arm & cam. 

How many shots are you getting from a cartridge?  I get between 35-38.

Roboslug

[Rob M]

THANKS ,  ill prob shim today and do some chrono again. Floyd , i havent counted a full to empty shot string yet..And yes , ive bookmarked all wyos threads for the big teardown    this is like the crosman 600 bible of the internet.. Shockingly , there no clear 600 teardown videos on youtube,.. theres 1 wwhere the guys hands block the gun for 30 minutes.

[WyoMan]

Floyd, I get three full mags (30 shots) with a pretty tight e.s. in each of my target guns... the ones with the scopes:



They were all built the same with the valve mods, spring preload, etc.
After the third mag is shot, I store them with whatever gas is remaining.
When I shoot them again, I dry fire to empty before installing the new cart and it usually takes 2 to 5 shots to empty the gas.

Rob, a couple more tear-down / build notes:
 - You don't have to remove the magazine follower but if you want to, there is a setscrew that retains the knob in the follower
 - Most broken pawls occur because people forget to remove them after the tube is slid about 1/2" rearward (the pawl will get jammed at the end of the tube slot)
 - In at least one variant, the valve retaining pins were different in size (o.d.) so they have to go back in their specific location (Crosman, Why would you do that?)
 - Make sure both valve vents are not blocked and do not use any kind of wet lube inside the hammer cavity
 - The cam / feed arm rotational positions (Up for Loading and Down for Firing) need to align perfectly with the center of the magazine and the center of the barrel accordingly

That's not a complete list but a few things for now...

Wyo