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Old 04-17-2011, 09:16 PM   #1 (permalink)
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Cooper T bolt fitment issue in a KP2

And now, another Cooper T related post from me ..

I recently purchased a KP2 from a member here and tried to install my Cooper T bolt (stamped KP2 on the bolt). The bearings in the bolt are about 1-2 millimeters too close to the rear of the bolt. They don't line up with the bearing holes in the KP2 upper tube that well. They can lock somewhat, but not all of the way. The rear sliding section of the bolt (that attaches to the pump rod) will, likewise, not slide shut all the way when sliding the pump arm forward. These pictures are big to show detail.

Attachment 23168

I can assure you the bolt is pushed all the way forward. The angle on these two pics makes it look like it's not.
Attachment 23169
Attachment 23170

The bolt does fire and cycle. It just doesn't lock in completely . I can see the hammer lug through the slit in the tube; it looks like the bolt is in the right place and seated in the correct forward position within the upper tube. This KP2 is an earlier model as well, so maybe the bearing holes were drilled a little closer to the breach (like maybe a millimeter or two, nothing too different).

Any ideas to make it fit?
Are these bolts adjustable in any way?
And has anyone on here run into a similar situation before?

* I do not want to modify the KP tube or do anything crazy to the bolt, as it's NOS.
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Old 04-17-2011, 09:22 PM   #2 (permalink)
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Is there a buildup of crud or dirt in the very front of the slot in the tubes that the cocking lug rides in, preventing it from going all the way forward? What kind of lug did these have? The ground down set screw or the spring loaded plunger kind?
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Old 04-17-2011, 09:32 PM   #3 (permalink)
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The bolt is clearly not as forward as it needs to be. I know you said it's all the way forward and I"m not doubting you. But it's not as far forward as it needs to be. The reason it's not cycling is probably that the air passage in the bolt isn't lined up with the air passage to the valve in the tubes. I'm gonna guess the bolt pin is hitting the part where the tubes come together in the slot. I'm not sure why though. Can you take a picture of the bolt outside the tubes...like lay the bolt on top of the top tube so we can see where the bolt sits on the tube....does that make sense.
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Old 04-17-2011, 09:57 PM   #4 (permalink)
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The tubes, and that slot specifically, are clean. The lug is a 1/2" allen set screw that threads into the bolt.

I can assure you it's all the way forward. The bolt cannot physically go any further. The back section of the bolt (the red section at the end of the bolt when it's installed) is flush and touching the brass tube. It will not slide forward any farther. You may have misread my post, but it does fire and cycle. I shot a few rounds through it and everything looked good.
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Old 04-17-2011, 10:06 PM   #5 (permalink)
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I'm out of town until tomorrow. I'll snap a few more pictures when I get back.
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Old 04-18-2011, 04:50 AM   #6 (permalink)
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Maybe thats why that bolt was still unused. The Barrel could be off also, Sheridan KP2 bolts did not have a shoulder at the back like the Cooper-T does so the stock bolts are self aligning in the bearing holes. You can use the stock bolt and put your thumb behind it to prevent blowback since it is not drilled for detent balls.
Try the Cooper-T bolt in another KP2 to see which one is off.

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Old 04-18-2011, 10:19 PM   #7 (permalink)
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Maybe thats why that bolt was still unused. The Barrel could be off also, Sheridan KP2 bolts did not have a shoulder at the back like the Cooper-T does so the stock bolts are self aligning in the bearing holes.
Good points. I'm going to tinker with it tomorrow night, when I have time, to see if I can make it work. I have a feeling there is something keeping it from sliding all the way forward.

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Try the Cooper-T bolt in another KP2 to see which one is off.
I wish I had another KP2 to test fit it into. I have a 3, but the bearing holes do not line up with the KP2 bolt...
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Old 04-19-2011, 07:49 PM   #8 (permalink)
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Ok, so I finally got a little time to tinker around with the bolt to see what's going on.

The first thing I did was remove the cocking lug. I did this to both more easily move the bolt around, and to eliminate it (at least at this point) as a factor preventing the bolt from sliding forward. I looked at the lug before removing it and it does look like there is space in the slot for more movement forward (so that's good news).

Here are two photos that show the bolt is all the way forward. The sliding/locking mechanism will not push any farther. The end, or shoulder, ring of the bolt is hitting the back of the barrel tube and preventing the bolt from fully seating. Here are the photos:

Attachment 23239
Attachment 23240

Here are two photos, with a penny being used as a gauge, that show how close the bolt is to seating.

Attachment 23241
Attachment 23242

I believe that if a small amount (around a millimeter) of aluminum was removed( from the front of the shoulder); the bolt would have enough wiggle room to slide forward and lock. What do you guys think? I would want it turned on a lathe for both accuracy and a clean finished product.
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Old 04-19-2011, 08:12 PM   #9 (permalink)
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I think I mis-understood what was going on in your original post. The first picture is clear and the rest are a little blurry so I think I just didn't get what you were getting at. I'm gonna ask some questions and give you some thoughts at the same time.

I think the red part of the bolt looks like it's not horribly seated. The black inner part of the bolt should be able to be pushed forward which it isn't. That's not a seating issue, as much as it would be a bearing depression issue. If the bearings are allowed to push outward (into the pre-drilled holes) that part can't slide forward (which I no just re-read from your OP). I don't think blowback is your issue as much as letting that part of the bolt press forward.

Maybe I'm still missing it, but from your newer pictures, it looks like the seating isn't the problem. And a millimeter would cause it to not cycle at all....you just wouldn't get maximum efficiency.

Kind of thinking backwards.....I remember you originally posting in another thread about how you wanted to take this bolt apart because it was gumming up. Here's a thought (and some problems I've had in the past with bolts)....depending on how much use this bolt has seen the little rod on the end of the black part of the bolt (the inner part that pushes the bearings outward) could have been messed up and needs to be re-squared....allowing the bolt to work properly......OR perhaps the little o-ring on the inside of the bolt (black part again) has been shreaded and is causing it not to slide foward properly. I'm almost wondering if taking the bolt apart isn't the starting place before you mill anything.
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Old 04-19-2011, 08:52 PM   #10 (permalink)
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I may try to take it apart again, but the small pin that holds the bolt together is a major pain to remove. I oiled the bolt several times and worked the oil down into the bolt and the stroke is now butter smooth (it just needed to be lubricated).

Adding onto that- I really do not think the internals of the bolt are to blame. The sliding action of the bolt works fine with it removed from the gun. Also, I can slide the black part back (releasing the bearings) and the bolt will still not slide all the way into the tube. The bearings will not line up whether the black part is pushed forward or back.

I really wish I had another KP2 to install this into. I'm pretty convinced at this point that Chauncey designed these around the late model KP2's. I think the earlier models, like mine, had their bearing holes drilled about a millimeter, or so, closer to the front of the barrel (when compared to the later models). And I think most people never realize this because (like Smiley said) the OEM bolt does not have a back cap and is self-aligning. But when you introduce a bolt with a back cap (and subsequent limited forward movement) this slight difference in bearing hole location becomes a problem.

Does anyone on here have an early model KP2 and a Cooper-T bolt they could try to install into it? I know there are more than a few collectors/hoarders on here .
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