arakboss

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1/2" tube fits perfect through the G21 slide barrel hole.

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arakboss

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JMHO, but the risk is low. Most "it's going blow up" predictions are based on a formula for sealed pressure vessels, but the extension isn't sealed. I would be more concerned about a bullet strike if the tube flexes under recoil.
Since I am starting with a 6" barrel that means I can cut down the bloop tube to around 12.5 inches or so. I want to have at least an inch of overlap with the tube over the barrel maybe closer to two inches. The barrel OD is .630 and the ID of copper tube is about .550. That is .080 that needs to come off the barrel OD or copper tube ID. The wall thickness of copper tube is .040 so I don't really want to thin that out much more. The barrel walls are .120 thick. If I took off .040 of the barrel walls that would get me my .080 overall diameter reduction. My barrel walls would then be .080 thick. My G22 factory barrel is a little over .090 thick. My M&P 40 barrel has about .082 thick walls. All the wall thickness measurements were taken in the grooves. That would probably be acceptable wall thickness?
 
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Once the bullet clears the muzzle the gas will expand past it dramatically lowering pressure, so if it was me I would not be concerned about it. The big variable would be how temperature would effect the coper tube. In theory I think you *could* get it hot enough for the tube to flex a bit more than normal, but I have never seen any test along those lines like with AL or TI suppressor melt downs and I think it would take a giggle switch to get it that hot
 

arakboss

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Once the bullet clears the muzzle the gas will expand past it dramatically lowering pressure, so if it was me I would not be concerned about it. The big variable would be how temperature would effect the coper tube. In theory I think you *could* get it hot enough for the tube to flex a bit more than normal, but I have never seen any test along those lines like with AL or TI suppressor melt downs and I think it would take a giggle switch to get it that hot
I will be shooting slowly, no mag dumping. I borrowed a sraight edge from the tool section and went through all the pipe pieces they had. This was the straightest of them all but not perfect over the two foot length. There will only be about 10 to 11 inches exposed to bullet travel so hopefully the tube stays straight. With an ID of .550 and a .401 bullet there isn't a lot of room to spare. If I was adding a bloop tube to a rifle I would go with bigger diameter but since I am limited by size of slide barrel hole this is the best I can do.
 

arakboss

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I have decided to cut the two foot tube in half so if I screw up one tube I will have a second tube to try again. This will result in only 1.25 inches or so of the tube overlapping the barrel. I would like to try this out before silver soldering it to the barrel. I imagine the slip fit will be pretty tight but not sure if I should rely on that to hold up during test firing. I will shoot it as a pistol prior to silver soldering the tube on. My main goal in testing is to make sure the bullets are going to travel through the tube without making contact with the tube. I do not have a lathe so grinding the barrel down is going to be ghetto job with a bench grinder, die grinder, dremel and or files.

Any ideas on temporarily securing it to the barrel are welcome?
 

arakboss

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This is my initial idea to attack the barrel grinding.

First step will be with bench grinder, I will grind down a band roughly the width of the grinding wheel next to my taped mark to achieve a .560 diameter. This should create a nice step between the newly reduced area and the full diameter area of the barrel. After that is completed I will move down towards the muzzle and continue grinding the surface to around .560. Once the .560 measurement is achieved to the muzzle I will go back over it with the die grinder and or dremel to achieve the last bit of reduction. I may decide to try and take a little bit of thickness off the ID of the copper pipe but not sure yet. Surprisingly to me, the bench grinder is very slow at removing material so I am not very worried about grinding too much off.

Grinding won't begin before Sunday night so I have time to sleep on this idea.
 

arakboss

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I was able to drop an entire 45acp cartridge through the 1/2" copper tube with room to spare. That makes me feel better about the chances of a 40cal bullet making it through without contacting the tube.
 

arakboss

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I think the barrel is ready to pound on the tube. It will be a very tight fit and the tube likely won't be able to be removed without damaging it once it's installed. I could continue filing on the barrel to make for a looser fit but I really don't want to remove much more material from the barrel. I think I can get the bloop tube installed on the barrel with a hammer. It may expand the copper tube a tad when it slips over the barrel. If that makes the copper tube too wide to fit in slide hole, I can sand the exterior of the copper tube to fit. I filed some grooves inside the copper tube and roughed it up so the silver solder will have places to flow to.


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