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  #46  
Old 10-06-2021, 01:55 PM
zukiphile is online now
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Quote:
Originally Posted by 12Bravo View Post
Hopefully my photos helped out.
Yes, and thanks for those.

I can understand why the guys with Keystone barrels might like something more tidy than a bolt through the side of the receiver.
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  #47  
Old 10-06-2021, 03:44 PM
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Glad that I could help. I know that the TacSol and Chiappa bolts are slightly different from each other and both are a different length than the CMMG bolts.

After watching the video on how to modify the CMMG bolt rails, I wonder why they decided to do things that way. I understand wanting to use the CMMG bolts since they are the gold standard of AR22s Making it so nothing holds the bolt and recoil spring assembly together seems a bit odd to me.

I'm going to have to do some research to see what can be done short of putting a screw into the side of the receiver.
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  #48  
Old 10-06-2021, 03:52 PM
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Okay after looking at one of my CMMG bolts, I don't see a good solution to hold everything together after modifying to to work with the Keystone barrel. I personally would try a set screw in the receiver versus a cap head screw.
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  #49  
Old 10-06-2021, 05:58 PM
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Quote:
Originally Posted by 12Bravo View Post
After watching the video on how to modify the CMMG bolt rails, I wonder why they decided to do things that way.
You prompted me to look for then video. I can think of much better ways to do this, but it takes more than 10 seconds and a grinding wheel. Those videos make me want to dope slap him.

A little tack or pin placed through a tiny hole in the end of the fork would hold the bolt on the frame. There would also need to be a relief cut in the breach face for the head of the tack or pin. The barrel tenon itself would retain the tack or pin.

It requires drilling one very small hole in the frame and slightly adjusting his CNC process for one of the rail end cuts in his barrel tenons.

The pin would hold the bolt and keep the recoil spring compressed. On installation, the pin head would disappear into the barrel tenon and permit the bolt to hit the breachface during cycling. The pin would not be stressed during cycling. When the bolt is removed the pin would emerge from its slot in the tenon and engage the bolt so the recoil spring stays compressed.

I don't remember exactly what he charges, but it wasn't very inexpensive. Seems as if he could have increased the value of his product with a bit of creativity.
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  #50  
Old 10-06-2021, 06:00 PM
Erik72
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Quote:
Originally Posted by 12Bravo View Post
Hopefully my photos helped out.

It looks like to remove the recoil spring assembly on the Chiappa that I have to push out the two roll pins to relieve spring tension and then unscrew the cap from the other end.
Oh yeah! Quite helpful actually. Thank you. I was looking at the CMMG bolt pretty hard last night. The Chiappa method for retaining the bolt looks similar to what I was imagining. It looks like the spring guide rod is full length from the back of the rail assembly to the front of the bolt face. This means the bolt actually reciprocates along the rails as well as the spring guide rod. The CMMG spring guide rod is only about 4.6" long. The spring guide is held in place at the rear of the assembly with spring pressure but the bolt with the spring guide housing atop reciprocates without riding along the the guide rod.

My thought was to take a piece of steel rod 0.125" diameter and thread it into the back of the guide rail plate that sits against the buffer. You'd have to shave a little material off the front of the spring guide housing so you can put a screw head or welded on nut (like Chiappa did). The trick here is to determine the correct length where the bolt is not slamming against the screw head on your guide rod but against the barrel breech as it is intended. I'd think 6" is the right number since that's where CMMG stops it now. All it is doing is keeping the bolt from shooting off the end of the rails. It's not stopping the bolt during cycling. The barrel does that.

This is not really a necessity...Just really trying to think through it. The alternative for me with the Keystone barrel is to continue to use the screw in the side of the receiver as it is now. It works. And if I did open the upper receiver without the retaining screw, the CMMG bolt does come shooting out. Just gotta pay attention.

Here's a pic of the CMMG bolt showing the overall length measurement complete with Borebuddy Weight and Heavy Spring.

The 2nd pic is the TS bolt disassembled. The spring does not extend into the guide rod housing that sits atop the bolt. The guide rod is inserted from the front retained at the rear of that piece.
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File Type: jpg IMG_4384.jpg (492.6 KB, 2 views)
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  #51  
Old 10-06-2021, 06:12 PM
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Quote:
Originally Posted by Erik72 View Post

My thought was to take a piece of steel rod 0.125" diameter and thread it into the back of the guide rail plate that sits against the buffer. You'd have to shave a little material off the front of the spring guide housing so you can put a screw head or welded on nut (like Chiappa did). The trick here is to determine the correct length where the bolt is not slamming against the screw head on your guide rod but against the barrel breech as it is intended.
Why can't the screw head or nut sit in the hole of the charge handle?

EDIT- I just looked at a CH, and the gas tube hole is far too high to act as a resting place for anything in line with the recoil spring guide rod.

Last edited by zukiphile; 10-06-2021 at 08:10 PM.
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  #52  
Old 10-06-2021, 06:49 PM
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Okay I think I figured out a solution but it will require some machining. You will have to make a new guide rod that is threaded on both ends and also will need a small cap like on the Chiappa guide rod. Then tap the back plate and machine the front of the bolt guide rod hole to accept the thread cap.
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  #53  
Old 10-06-2021, 07:00 PM
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Quote:
Originally Posted by 12Bravo View Post
Okay I think I figured out a solution but it will require some machining. You will have to make a new guide rod that is threaded on both ends and also will need a small cap like on the Chiappa guide rod. Then tap the back plate and machine the front of the bolt guide rod hole to accept the thread cap.
You and Erik are on the same page, but haven't mentioned one element: a part that allows the bolt to compress the spring when it cycles.

That why I suggested knocking out the spring pin in the spring shroud and screwing in a hollow set screw with a hole large enough to let the guide rod through, but small enough to stop the spring from popping out of the front of the shroud.

Also, I don't think the guide rod needs to be threaded into the backplate. The guide rod and spring will stay with the bolt just as on the Chiappa it stays with the frame.

In 1911 terms, this is like a conversion from a GI guide rod to a full length guide rod.

Last edited by zukiphile; 10-06-2021 at 07:18 PM.
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  #54  
Old 10-06-2021, 07:20 PM
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Quote:
Originally Posted by zukiphile View Post
You and Erik are on the same page, but haven't mentioned one element: a part that allows the bolt to compress the spring when it cycles.

That why I suggested knocking out the spring pin in the spring shroud and screwing in a hollow set screw with a hole large enough to let the guide rod through, but small enough to stop the spring from popping out of the front of the shroud.

Also, I don't think the guide rod needs to be threaded into the backplate. The guide rod and spring will stay with the bolt just as on the Chiappa it stays with the frame.
I have thought of that. And a cap like on the Chiappa guide rod will work on the CMMG bolt. On both systems the actual guide rod is recessed in some and not flush with the end of the bolt. Plus the guide rod itself does not move.

Yes it would take some machining and threading to the bolt and guide rod but it will work.

This is what you see when you push the Chiappa bolt all the way back against the back plate.
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  #55  
Old 10-06-2021, 07:40 PM
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Quote:
Originally Posted by 12Bravo View Post
This is what you see when you push the Chiappa bolt all the way back against the back plate.
Ah, I see.

The stock CMMG spring is design to extend essentially the full length of the BCG. If you begin a cycle with that spring much behind the current spring pin location, the spring will reach full compression before the bolt completes its rearward journey. I was imagining something like the picture below, a "jam screw", threaded into the spring shroud -- something to compress the recoil spring on recoil, which is what the spring pin does in the existing design.

https://www.holo-krome.com/jam-screws.html

http://slotblog.net/topic/28915-hollow-set-screws/

That would allow the retention nut or bolt to sit all the way out at the end of a six inch spring guide rod.

Last edited by zukiphile; 10-06-2021 at 07:46 PM.
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  #56  
Old 10-06-2021, 08:23 PM
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It can be done and I fully understand where you are coming from with the spring compression. We just need to figure out the best solution to keep everything together when you remove the bolt from the receiver. And a screw in the side won't do that.
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  #57  
Old 10-06-2021, 09:12 PM
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Quote:
Originally Posted by 12Bravo View Post
It can be done and I fully understand where you are coming from with the spring compression. We just need to figure out the best solution to keep everything together when you remove the bolt from the receiver. And a screw in the side won't do that.
Incredibly, I think all that screw does is keep the frame from smacking someone in the face.

Erik, if you are still reading this, maybe you'd want to raise the issue with John at Keystone. Isn't he the one who requires a customer to send in the upper parts for him to assemble?

With a jig and drill, he could execute the hole in the rail and pin idea for nearly nothing. If he ordered 100 six inch threaded guide rods, jam nuts and cap nuts, he could probably get them at a nice price, and even offer a kit to his prior customers.
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  #58  
Old 10-07-2021, 10:53 AM
Erik72
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Quote:
Originally Posted by zukiphile View Post
Erik, if you are still reading this, maybe you'd want to raise the issue with John at Keystone. Isn't he the one who requires a customer to send in the upper parts for him to assemble?
Oh I'm still here. To be honest, I'm just glad John is willing to make his barrels again. The fact that he's showing us how to alter the bolt rails ourselves tells me he doesn't want to mess with the assembly part anymore. When I first became familiar with his 22LR product, he offered just the barrel...I think. I can't recall if he offered the barrel and bolt together. I procrastinated and time passed. When I went back, his website said he'll only sell the barrel if you send him your parts for assembly. There must have been issues with customers doing the alterations on their own. Then last year in the springtime he announced to some that he wasn't even doing the AR22 barrels anymore. I thought this might be temporary because he was hot on Vudoos and RimXs a the time. Anyway, you're right...it can't hurt to raise the issue.

I appreciate this great discussion and sharing of resources (i.e. ideas and photos). I feel like I know what I need to do and what parts to get. It's the execution part that will likely stump this operation.
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  #59  
Old 10-07-2021, 11:53 AM
zukiphile is online now
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Erik, is getting the bolt into a Keystone upper difficult?

I can put together a CMMG BCG with little fuss, but it took a little learning and I have 360 degree access to the whole thing while I'm doing it. I'd imagine that getting the spring compressed without that 360 degree access would be difficult.
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  #60  
Old 10-07-2021, 01:15 PM
Erik72
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Originally Posted by zukiphile View Post
Erik, is getting the bolt into a Keystone upper difficult
Actually it is not difficult at all. Only slightly more difficult than assembling one with the collar. Even wrestling with the anti-bounce weight weight it's not that bad; especially if you've got the upper mounted in a vice. The current configuration works. I guess we've really derailed this thread trying to solve a problem that's really not a problem. Can it be improved? Sure, but I'm certainly not dead in the water.
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