Cooey 600... something wrong?

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kraut_wagon

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I bought my Cooey 600 less than a year ago. Didn't pay too much for it and for the last 300 - 400 rounds it and it's been a great, reliable, accurate little rifle. But I've noticed over maybe the last 50 shots I've been getting the odd one that sounds kind of muffled. One shot will be a nice loud crack and the next sounds alot quieter.
At first I thought it was a bad round, but it's been happening more and more with this gun and not with my other 22 shooing the same ammo. I though the bore could be fouling up so I cleaned it, but I put 20 shots through it earlier today and at least 2 sounded muffled.
Anyone ever come across anything like this?
I'm shooting Federal Champion 36 grain copper plated HP.
 
I have noticed this same thing before. Not with my 600 but with my old JW-25A.
Are you seeing any difference in point of impact? Or maybe verticle stringing?
One thing I did notice with my 600 was that the lower you are in respect to the bore, the quieter the rifle seems. Found this out when first getting used to the rifle
Cheers!!
 
Interesting.... The only time I've noticed the muffled sound (as far as I can remember) was shooting prone. I guess I'll experiment with some different shooting positions to see if the sound changes.
 
I have heard quite a few "muffled" or FTF carts in the bricks of federals I shot. I think that it is due to the quality control in the factory. Most factories are supplying the war effort and the home supply is suffering greatly. the same gun firing the same ammo should not vary in sound unless it is the ammo.
 
Winnipeg Toymaker said:
I have heard quite a few "muffled" or FTF carts in the bricks of federals I shot. I think that it is due to the quality control in the factory. Most factories are supplying the war effort and the home supply is suffering greatly. the same gun firing the same ammo should not vary in sound unless it is the ammo.
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x2, can't see it being the gun at all. Perhaps there are some different rounds mixed in? As long as all rounds are exiting the barrel and reaching the target in a semi-accurate fashion, I wouldn't worry too much about it.
 
I've never had that happen with the Federal 40gr solids I shoot, but all the winchester ammo I've ever tried was full of random subsonic rounds.
 
What do the fired cases look like on those that sound muffled compared to those that sound normal? It could be light firing pin strikes that aren't igniting the round as well.
 
TimberPig said:
What do the fired cases look like on those that sound muffled compared to those that sound normal? It could be light firing pin strikes that aren't igniting the round as well.
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You think the pin could be getting sticky? What would the shells look like if that was the case? Less of an indent where the pin strikes?
 
kraut_wagon said:
You think the pin could be getting sticky? What would the shells look like if that was the case? Less of an indent where the pin strikes?
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Exactly. Gummed up oil and crud in the bolt or a tired firing pin spring could reduce the strength of the firing pin strike.

This should show as light strikes with less of an indent on the rim.

You should use the instructions on here to pull your bolt down for a cleaning. It will at least eliminate the firing pin strikes as the problem. Since your other rifle fires the ammo fine, it is likely the rifle that has the issue not the ammo, unless you are just having really bad luck that all the weak rounds have made it into this rifle only.
 
kraut_wagon said:
You think the pin could be getting sticky? What would the shells look like if that was the case? Less of an indent where the pin strikes?
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This would not be the problem as the primer is still being ignited, the firing pin will not change the report of the round going off.

22 rimfire ammo is known for the sound to change, it is common because of the way the bullets are made, for instance grab a assortment of shells from the box and try to twist the lead while holding the case. When you do this you will most likely notice that you can twist the bullet on quite a few rounds, some will be harder than others, some will not twist.
 
crazydave said:
This would not be the problem as the primer is still being ignited, the firing pin will not change the report of the round going off.

22 rimfire ammo is known for the sound to change, it is common because of the way the bullets are made, for instance grab a assortment of shells from the box and try to twist the lead while holding the case. When you do this you will most likely notice that you can twist the bullet on quite a few rounds, some will be harder than others, some will not twist.
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It is well known and laboratory proven that the strength of the firing pin strike makes a bigger differnece in the heat produced by centerfire primers than does the difference between standard and magnum primers of the same size. It will be no different in a rimfire than in a centerfire. If it is striking weakly the compound will not ignite as quickly and will not produce as much heat, which will result in less efficient ignition. If it doesn't burn as well, it isn't going to sound the same as a properly ignited round.

Worst case scenario if it is indeed the ammo, at least he has eliminated the rifle from the equation.
 
TimberPig said:
It is well known and laboratory proven that the strength of the firing pin strike makes a bigger differnece in the heat produced by centerfire primers than does the difference between standard and magnum primers of the same size. It will be no different in a rimfire than in a centerfire. If it is striking weakly the compound will not ignite as quickly and will not produce as much heat, which will result in less efficient ignition. If it doesn't burn as well, it isn't going to sound the same as a properly ignited round.

Worst case scenario if it is indeed the ammo, at least he has eliminated the rifle from the equation.
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The original post made no mention of fail to fire scenarios so the firing pin would have to be hitting (reliably) hard enough to ignite the primer, but as stated the ammo is well known for the muffled/ loud phenomenon, also if it was the firing pin gummed up there should be FTF happening on a regular basis with the (compound not igniting as quickly and not getting efficent ignition).

If there is no frequent fail to fire happening then the firing pin being gummed up is not the problem, but i bet if he went to higher grade (match ammo) he would notice the rounds would sound more uniform when he fired them.

So if the rifle is working fine don't worry about it because all rimfire rifles produce the off sound once in a while just go shoot and have fun, worry about the firing pin when the rifle starts to malfunction.
 
Like suggested above try another type of ammo and then clean the bolt really well with brake cleaner , blow out and the oil lightly and try that. also check if the cocking pressure is the same every time
hope you find the answer - my 600 has been going fine for many many bricks now. All i shoot now is cci ammo seems the most reliable and accurate blazer for plinking and SV target in my handguns. Hoping to get some SK match to try in the savage mkII BV

ANdy
 
crazydave said:
The original post made no mention of fail to fire scenarios so the firing pin would have to be hitting (reliably) hard enough to ignite the primer, but as stated the ammo is well known for the muffled/ loud phenomenon, also if it was the firing pin gummed up there should be FTF happening on a regular basis with the (compound not igniting as quickly and not getting efficent ignition).

If there is no frequent fail to fire happening then the firing pin being gummed up is not the problem, but i bet if he went to higher grade (match ammo) he would notice the rounds would sound more uniform when he fired them.

So if the rifle is working fine don't worry about it because all rimfire rifles produce the off sound once in a while just go shoot and have fun, worry about the firing pin when the rifle starts to malfunction.
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If the ammo is the problem, why does it only appear in this rifle, not in his other one as well? It could well be the ammo, and trying other ammo may solve it, but a little maintenance on his bolt to ensure it isn't the gun isn't going to hurt anything is it? Especially since it is basically free (half our if time, few squirts of solvent and a rag). If it continues following cleaning with the same ammo, then yes we can conclude it is likely the ammo. Since you are advocating switching to a different ammo, what is the cause going to be if he doesn't clean the bolt and it continues to do it even with high quality ammo?
 
TimberPig said:
If the ammo is the problem, why does it only appear in this rifle, not in his other one as well? It could well be the ammo, and trying other ammo may solve it, but a little maintenance on his bolt to ensure it isn't the gun isn't going to hurt anything is it? Especially since it is basically free (half our if time, few squirts of solvent and a rag). If it continues following cleaning with the same ammo, then yes we can conclude it is likely the ammo. Since you are advocating switching to a different ammo, what is the cause going to be if he doesn't clean the bolt and it continues to do it even with high quality ammo?
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I by no means am suggesting not to clean the gun, (should be done regularily as proper upkeep anyway) and doing so is not going to hurt anything for sure. but what i am saying is with no fail to fires it is most likely the ammo, and the cooey is probably doing this more often because it is old and probably been used more than his other rifles, so tolerances are probably looser add to this inconsistant ammo and you guessed it more noticable on the cooey.

I have owned many rimfires over the years and the firing pin has to have very little gum or grit to cause ftf so if he is not experiencing those chances are it is the ammo.

By all means clean the bolt and firing pin, might make a small difference but don't be surprised when you still get off sounding shots. (22 AMMO IS WELL KNOWN FOR THIS) and yes it is more known of in old cooeys mostly due to wear.
 
I think I'll clean the bolt/firing pin real well and see if that makes a difference. As previously stated, with my other 22, (a TOZ 17) all shots sound identical out of the same brick. I have no doubt that cheap ammo misfires and is consistently in consistent, but 2 or 3 shots out of the same 10rd magazine sounding muffled seems excessive. Not only do I want it fixed if there is a potential problem, I want to find out what the issue is, just b/c I'm curious. I'll do one thing at a time, first clean the pin, then change ammo. What is good, consistent ammo that is reliable enough for testing purposes such as this kind of trouble shooting?
 
So I cleaned the bolt thouroughly, lots of brake and parts cleaner and some good penatrant/gum dissolver called deep creep. Lots of grey stuff came out.
I put 8 shots through it earlier today, all sounded the same, and all the indents on the shells look the same, here's a pic.
HPIM2594-1.jpg

I'll continue to shoot but it seems ok for now. Thanks for all the help.
 
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