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81mm Mortar barrel/tube/build info (Page 15 of 15)
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Originally Posted By Ben: Does anyone have a TDP or prints/build data for the M69B barrel And The M69B firing pin? Thanks in advance! Originally Posted By Ben: Does anyone have a TDP or prints/build data for the M69B barrel And The M69B firing pin? Thanks in advance! I think the thread pitch is somewhere in this thread.  But I'll try to get it this evening.  Thread info. Originally Posted By 7insert: Originally Posted By MHIDPA: I'm down for any info, I can make drawings for what I have, just needed the OAL, I can make a FP myself just can't turn metric threads, but I saw another thread saying they are M6x1.0 so I can get a die if need be. Absolutely M6x1.0 and here is the length we used on the new production run https://i.imgur.com/QPIlQEz.png |
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Originally Posted By MHIDPA: I've been thinking about smoke as well. Just don't want to start a fire. Originally Posted By MHIDPA: Originally Posted By walkinginadangerzone: Just another range day hopefully soon. Since I've shot spotting rounds, now I want to make a smoke round. I've been thinking about smoke as well. Just don't want to start a fire. Wait for rain season?
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| Yep, that's who I was going to base off my smoke mixture off of, if I ever get around to doing it. He's done the lords work this past year with his smoke mixture R&D for sure. Unfortunately he's had a rough few months. (blowing himself up, and a subscriber getting caught in a legal battle over "bomb making materials") |
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Bump. I drop tested my latest iteration of 3d printed 81 projectile. They passed. My initial design was modeled after my metal inert rounds and printed in PLA+. They broke at the body/tail connection consistently. The new designs have added thickness around the threads, are printed in PETG, and I shortened the threaded hole so the tail fin bottoms out in the threads. This makes the contact spot the top of the threaded post and removes any gap above the threads. I think removing this compressible area helped a ton. One prototype of the new version has metal rods glued in running the axis of the threads for added stiffness. Its super windy today but I may make a run to the desert to test fire these. |
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Here's a pic of version 2 with the cracks at the threads. Version 3 that passed has a shorter threaded hole. I initially made the hole deeper to fully seat the tail fin. My theory is this left a gap above the tail fin that was compressing on drop which caused the plastic to fail. https://flic.kr/p/2s2vatS Here's a pic of the metal rods inserted along the threaded axis. I modeled in holes slightly undersized, drilled those out to size, and superglued in metal rods that extend into the concrete filler in the body. The hope is these provide more stability to the layers where it was breaking. https://flic.kr/p/2s2ukfW ETA image links are broken. I'll fix this post and add better pictures tonight. Aiming to test these next weekend, weather permitting. |
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Originally Posted By Sonoran_Tj: Here's a better pic. https://live.staticflickr.com/65535/55151697106_24582f028f_b.jpg20260316_152445 by AB762, on Flickr Im gonna need that file as soon as you get some successful tests! |
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Originally Posted By SGT-Fish: Im gonna need that file as soon as you get some successful tests! For sure. I'm willing to put the body and fuze designs up on odysee. With @MHIDPA 's permission, seeing as the basic design of the body, fuze well, and fuze were his design. All I did was re-work the exterior dimensions of the body and interior of the fuze to make it point detonating. |
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Originally Posted By Sonoran_Tj: For sure. I'm willing to put the body and fuze designs up on odysee. With @MHIDPA 's permission, seeing as the basic design of the body, fuze well, and fuze were his design. All I did was re-work the exterior dimensions of the body and interior of the fuze to make it point detonating. Go for it. The fuze well idea was something I saw someone else do, maybe SGT-fish... I can't remember. |
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Originally Posted By MHIDPA: You can't rethread the tube, it is smaller than the minor diameter of the threads. What I did was cut the tube off above the demill, then I turned down the tube about .050 and press fit a threaded sleeve. It shortened the tube down to the length of a US 81. I think this solution is safer than a reweld but much cheaper than a new tube. Originally Posted By MHIDPA: Originally Posted By Ben: I just received a bunch of Bowman Yugo M69B 81mm sets. I haven't even opened them up yet, as I have 87,000 things happening right now- without me digging through the whole thread did anyone ever determine if there is in fact enough meat left to cut the tube above the hole and rethread for the cup? Or the consensus ended up being weld or get a new tube? You can't rethread the tube, it is smaller than the minor diameter of the threads. What I did was cut the tube off above the demill, then I turned down the tube about .050 and press fit a threaded sleeve. It shortened the tube down to the length of a US 81. I think this solution is safer than a reweld but much cheaper than a new tube. I just got my Bowman kit and after eyeballing it, I agree with your thinking, this is the way I am going to do it also. |
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I was going through some of the M880s that I bought a while back. One still has a live lift charge in it. Attached File Attached File |
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Forgot to update after my last test. Fully 3D printed bodies still don't work. The launch force shattered the plastic at the threads. I'm getting ready for a move so my development is on pause for a couple months. I'm going to work on adding a metal pipe through the center. I'm giving up on a fully 3D printed body for now. |
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Originally Posted By MHIDPA: 25 of these showed up recently. https://www.ar15.com/media/mediaFiles/60540/2866_jpg-3743994.JPG  Nice! Can you share how the firing pin and spotting charge holder work? |
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Quick breakdown of the fuse. This is the firing pin, turned from a bolt. Attached File Firing pin installed. Attached File Shell Carrier made from 1" pipe bored for 12ga. Attached File The shell carrier floates in the fuse housing that has vent holes and a welded cap on one end. Attached File Complete assembly (I know the welds are ugly), upon impact the carrier drives the spotting shell into the firing pin. Attached File |
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Be careful of people shooting 50s while your rounds are down range... Attached File |
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Attached File |
"They want you dead but will settle for your submission" - Malice
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Originally Posted By juan223: https://www.ar15.com/media/mediaFiles/137019/1000011307_jpg-3763442.JPG You starting your mortar journey? 
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Bump and a Slightly Graphic reminder to GET YOUR HANDS AWAY FROM THE MUZZLE |
META's POV is pretty cool.  81MM Mortar POV |
81mm Mortar barrel/tube/build info (Page 15 of 15)
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