Cooey Model 64 Cycling Too Early

[p-17]

I have an old Cooey Model 64 .22 semi auto from the 1970s which was my first rifle. I haven't fired it in at least 15 years because I deemed it to have become unsafe. I wonder if there is any fix for its problem.

During the firing cycle, I had begun to notice that powder was being thrown out with the brass during firing, suggesting that the action was opening prematurely before all the powder had all been burned. The chronograph also indicated that velocities were about 200 f.p.s. below where they should have been -- a further indication that not all of the the powder charge was pushing the bullet.

Finally, the ejected brass all had a large circumferential bulge in front of the rim, suggestive that the action was opening and pulling the brass out of the chamber when the pressure was still high.

Is there any fix for this? It seems to me that, for whatever reason, the bolt is not heavy enough to provide sufficient inertia for the cartridge during firing to prevent the action from cycling back open. Is it just a matter of replacing the action spring with a heavier one to put more forward pressure on the bolt (thereby effectively increasing the weight of the bolt)?

What are your thoughts? If it is a quick fix, I'll do it and sell the rifle to make space in my safe.

 

[guntech]

You can always try different ammo... often through the years just about every brand of ammo has had some hot loads... try some standard velocity ammo.

 

[mrbeil]

Try a heavier spring. Maybe over the years the spring has weakened

 

[billdick]

I had a cooey jam-o-matic doing that years ago and the bolt wasn't closing all the way. it would still fire even though it wasn't completely closed due to the fact it had lots of gummy build up on the bolt face and the rear of the barrel.

 

[bearhunter]

If you have the original plastic magazine, there is a good chance the plastic at the back of the mag is cracked. This will allow the lips of the mag to open up and allow the cartridge to tip up and jam on the top of the chamber mouth. This is a common problem with those rifles. There is no fix for the mags but there is a replacement mag assembly available that is all metal and works very well.

The model 64 is actually a very good design. The mag problem gave it a bad reputation. The model has been made under license by several different makers and works just fine.

I don't know where you can find the replacement kit but I have seen a few around so they are likely available but from a different maker. Google will be your friend.

 

[zuke]

Completely disassemble it and clean it

 

[p-17]

Thanks for the suggestions.

I was always very careful about cleaning it, so dirt/crud was never the issue.

The magazine was the original steel, and feeding was actually pretty good.

The problem was that the action would open prematurely while the pressure was still high, and the brass would bulge in front of the rim, suggesting that the bolt had moved back about 1/16 of an inch under the pressure of firing and the brass in front of the rim was expanding accordingly.

 

[Innercity]

Replace the recoil/guide rod spring.

That's where I'd start.

*The schematic show part #94 as the bolt spring. Try and source one of those.* Edit
That's from a Savage Schematic on Nurmrich

 

[camster]

I adore the 64s. They can be finicky. If you've owned it since the 70's, but not fired it in 15 years you at least know the history of the gem. As suggested, try a different ammo. If you can, try high velocity instead of hyper, with a solid round nose.

When shooting it, is only one round being fired? I have seen them run away with aggressive shimming under the trigger group. A dangerous condition, Because they cycle so quickly it sounds more like a single shot fired with a kind of echo, but it'll eventually jam.
-Look closely at your trigger group's reset and sear. Make certain there is no material between the trigger group and receiver.

Bulged around the rim indicates to me it's not completely chambered during firing. I find most .22lr ammo goes off fast enough the pressure should be dropping before the bolt starts to move.
-Make certain chamber is clean, and clear. You should see a distinct ring where chamber ends and rifling begins.
-Check overall geometry in your rifle. Make certain the barrel retaining clip isn't deformed, and seated square. A slight twist of the barrel can cause the bolt to bind on the ejector, and not close fully. Look close at the ejector itself, and make certain it's not twisted. Again, make certain the trigger group is tight to receiver.
-Cycle by hand and check for resistance. Charging a 64 takes a good pull on the tiny charging handle, and pressing in the charger to hold the bolt open can be tricky. If your's is easy/soft to cycle, the main spring is likely the culprit.(this is tricky with just one, as you can't compare) Also inspect the bolt closely, make certain the firing pin runs smooth and easy through it's channel in the bolt.

Personally I'd start with a thorough cleaning and inspection. I run my 64s without lube of any kind in the action. Cycle it by hand, and make certain the bolt closes tight (let the bolt snap ahead under spring pressure). Try a high, or standard velocity round nosed ammo when testing for function, with only 2 or 3 rounds in the magazine. I would do all this before considering part replacements. Eye n' ear protection is a good idea for shooting even with a "known good" rifle, and mandatory for testing. A bulgy case isn't nice, but once you've experienced a blown case, you'll be thankful for the hearing protection...they are crazy loud.

I'll go digging. I'm pretty sure a I have a complete, period correct, bolt here somewhere.

 

[marshall]

Have you dropped alive round in it by hand ( at the range)?
It is suprising how many time I am told that a chamber is clean on a 22RF
and a new round will not seat full length with out a push.
See it more with guns that shoot shorts, long, and L.R.
Double check the camber and the firing pin.
A 22 opening on firing is rare, but a new spring would be in order as well.

 

[zuke]

Are you sure the barrel is set back far enough? When you last removed it for cleaning and then replaced it did you move it all the way back before tightening the lock screw?

 

[BlairW]

Are you sure the barrel is set back far enough? When you last removed it for cleaning and then replaced it did you move it all the way back before tightening the lock screw?

My first thought as well

 

[weasel1]

My daughters new 64(G?) has been doing something similar. Some rounds are bulging near the room and others aren't. Not sure what brand was bulging though. Now I'm wondering if I should take it apart and check the barrel set-back. I know it's not a cleaning issue with my daughters. Don't think it has a hundred through it yet. It was torn apart for initial cleaning and again after a kaboom (Wildcat).

 

[weasel1]

Took it apart today and checked. Barrel is set perfect. But... I forgot I did do something to it...

When we first got it, it was feeding like crap. Bullets were jamming against the chamber. I filed the mag to smooth it out. I also put a slight bevel on the chamber (much like the 8-4 mod you see on SKS's so they feed hollow points). I have a sicking feeling that I shouldn't have done that...

There, I feel better. I'm an idiot. Now, can I fix it or is it new barrel time?

 

[kamlooky]

Took it apart today and checked. Barrel is set perfect. But... I forgot I did do something to it...

When we first got it, it was feeding like crap. Bullets were jamming against the chamber. I filed the mag to smooth it out. I also put a slight bevel on the chamber (much like the 8-4 mod you see on SKS's so they feed hollow points). I have a sicking feeling that I shouldn't have done that...

There, I feel better. I'm an idiot. Now, can I fix it or is it new barrel time?

Definitely new barrel time.
Trust me on this one................

 

[guntech]

I forgot I did do something to it...

I put a slight bevel on the chamber (much like the 8-4 mod you see on SKS's so they feed hollow points). I have a sicking feeling that I shouldn't have done that...

I think you just diagnosed your perceived problem.

The good news is ignore what you perceive to be a problem... if the rifle functions it is working... it matters not what the fired brass looks like... and all semi .22's spit gas all the time...

 

[weasel1]

True enough. The weird part was the fact some of the cars were bulging yesterday and some weren't. All the same ammo (Aguila subsonics). It did run really smooth and I'm grateful for that.