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81mm Mortar barrel/tube/build info (Page 12 of 15)
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Just a heads up for those of you looking for an eastern european spigot style mortar sight. There's one listed on Ebay, condition looks good. https://www.ebay.com/itm/176793818733?_skw=MORTAR+SIGHT&itmmeta=01JJ7TBRV7BB65YG5EDA0HM56C&hash=item2929bb966d:g:9MsAAOSwLohniYhg&itmprp=enc%3AAQAJAAAA8HoV3kP08IDx%2BKZ9MfhVJKlBEUEH3bUyL%2Fm5IM4S8iICumiqryrcVX9wFvqGSRVWNzGdS6y6LMBjrkrHBuXfWiX58120xZrcEbtVW5MAaGCGO3i2jvWIW0%2FmnMCKOOFKbj349lC5pr%2B%2F86c5dvIG1fZm7BZ1eJYk%2FrmzY8ZsUX0PfzBarUX9BpbkS44FWpuV98Te%2Fm0MKAFc31Wdw%2BscVNyibuR1Xly5fY2pZB1LY9iKMznZcKdBychSbBS5vDTRAfb3FfDGIiW6UqeGRaB%2FH1918xVEOm129v5kNiTPb%2F6fKsbXWUP2Qjn%2BMR7z%2BgFkzQ%3D%3D%7Ctkp%3ABk9SR_CNr_qRZQ |
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Good news: Got a good system down for making cheese/increments for the shells Bad news: My steel inert shell went ?????? Ive had good luck adding longshot powder to refillable tea bags (https://www.amazon.com/dp/B07QHXXLNV) and then Z folding them so the powder is effectively stuck in a line at the bottom and there is a single layer of the eco-pulp material and the vents of the shell itself. Once Z folded I use the strings to tie around the bag for further structural integrity. Hot glue or Blue painters tape to hold the bag betwixt your fins and over the vent holes as close to the vent holes as possible. My usual "plinking" load on the 81mm steel shell trained of tar consisting of 60gr of bullseye for a 0 increment will throw it ~150-180yd @ 55deg elevation. With 2x 30gr increments/cheese for a 0+2 load the shell hit an absolutely insane apogee to the point I could nolonger see it, distance well over 180yd and currently unknown how far that went as the shell is MIA. |
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Originally Posted By 7insert: Good news: Got a good system down for making cheese/increments for the shells Bad news: My steel inert shell went ?????? Ive had good luck adding longshot powder to refillable tea bags (https://www.amazon.com/dp/B07QHXXLNV) and then Z folding them so the powder is effectively stuck in a line at the bottom and there is a single layer of the eco-pulp material and the vents of the shell itself. Once Z folded I use the strings to tie around the bag for further structural integrity. Hot glue or Blue painters tape to hold the bag betwixt your fins and over the vent holes as close to the vent holes as possible. My usual "plinking" load on the 81mm steel shell trained of tar consisting of 60gr of bullseye for a 0 increment will throw it ~150-180yd @ 55deg elevation. With 2x 30gr increments/cheese for a 0+2 load the shell hit an absolutely insane apogee to the point I could nolonger see it, distance well over 180yd and currently unknown how far that went as the shell is MIA. That is both awesome, and a little scary. |
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Originally Posted By walkinginadangerzone: Lol nice, should've put the tube at 89 degrees if just testing the increment charges. Any residue left in the tube from the increment charges and were they nitrided? In my experience with my 60, anything in the tube tends to be ejected if it's light enough. |
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Originally Posted By MHIDPA: That is both awesome, and a little scary. Originally Posted By MHIDPA: That is both awesome, and a little scary. Thankfully its backed up to thousands of acres of empty forest Unfortunately thats a lot to search. Went after it for 2 hours on the azimuth today with the dog and metal detector but no luck. Maybe ill rope wife into it tomorrow for another 2 hours. Originally Posted By walkinginadangerzone: Lol nice, should've put the tube at 89 degrees if just testing the increment charges. Any residue left in the tube from the increment charges and were they nitrided? Yeah that was my first thought as soon as the thing rocketed out of the tube. No nitriding. I know people have done that in the past but I couldnt find a way to do it that wasnt absolutely shitty bordering on HME. A good consistent fold and usage of longshot was the ticket. Bullseye was no good in the cheese and would just get blown around in the tube like you would expect. Originally Posted By SGT-Fish: In my experience with my 60, anything in the tube tends to be ejected if it's light enough. Thankfully no confetti with these. I want to recover the round so I see the aftermath but my fault for not dropping it at 89. |
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Originally Posted By walkinginadangerzone: Oh cool, what's the difference in burn rate between Longshot and bullseye? Loading bullseye into mortar launch charges is the closest thing to reloading I've done.  Unique will get you closest to accurately reflecting the firing tables based on weight of the charge, at least for a 60mm shooting M49A2 shells. |
Lightning from the Sky, Thunder from the Sea!
Twitter/Instagram: benunsuppressed
https://americanpioneercorps.org
Twitter/Instagram: benunsuppressed
https://americanpioneercorps.org
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Originally Posted By Ben: Unique will get you closest to accurately reflecting the firing tables based on weight of the charge, at least for a 60mm shooting M49A2 shells. Originally Posted By Ben: Originally Posted By walkinginadangerzone: Oh cool, what's the difference in burn rate between Longshot and bullseye? Loading bullseye into mortar launch charges is the closest thing to reloading I've done. Unique will get you closest to accurately reflecting the firing tables based on weight of the charge, at least for a 60mm shooting M49A2 shells. Ah. |
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Originally Posted By MHIDPA: @ben Are those fuses still in the works? I've been deployed overseas since early last summer, and just landed stateside less than two weeks ago...going straight to the hospital at Walter Reed. Everything is kinda on hold indefinitely. Hopefully Bowman will have more mortars soon though...60s? |
Lightning from the Sky, Thunder from the Sea!
Twitter/Instagram: benunsuppressed
https://americanpioneercorps.org
Twitter/Instagram: benunsuppressed
https://americanpioneercorps.org
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Originally Posted By Ben: I've been deployed overseas since early last summer, and just landed stateside less than two weeks ago...going straight to the hospital at Walter Reed. Everything is kinda on hold indefinitely. Hopefully Bowman will have more mortars soon though...60s? I noticed you seemed a little more active recently. Welcome home, hope everything goes well. Looks like they only got 4 81s this time. Fingers crossed on everything else. |
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Got an adapter for my sight made. This one is 3D printed out of CF, I'm interested to see how it holds up. Attached File |
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Originally Posted By MHIDPA: Got an adapter for my sight made. This one is 3D printed out of CF, I'm interested to see how it holds up. https://www.ar15.com/media/mediaFiles/60540/1000004251_jpg-3479635.JPG I would detach the sight after laying the tube and before firing. That should prevent a lot of stress on the mount and should work fine. |
 I got lucky and bought 20 of these demilled 81mm fin sets for relatively cheap. I'm going to make some 3dprinted bodies for them so I don't have to make my own fin sets. For the price I got them, it doesn't make sense to print them. I still need to get my italian tube and cup separated and work on a firing pin. I'm not really expecting to have it done before the big event. But maybe I'll at least have some rounds made for others to try out. Shameless plug https://chevtecgroup.ticketspice.com/chevtec-shoot |
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Originally Posted By 7insert: Very cool, any chance of a file for this ? Sure thing, shoot me an email. Originally Posted By Sonoran_Tj: I would detach the sight after laying the tube and before firing. That should prevent a lot of stress on the mount and should work fine. Yeah. I think it would be ok for the M4, but the M53 is pretty heavy. I'll probably break down and make one out of steel, now that I know the design works. |
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Originally Posted By MHIDPA: Yeah. I think it would be ok for the M4, but the M53 is pretty heavy. I'll probably break down and make one out of steel, now that I know the design works. Even with a metal mount it's SOP to remove the sight when seating the base plate. Reduces the risk of the recoil breaking the sight. |
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Originally Posted By MHIDPA: Got an adapter for my sight made. This one is 3D printed out of CF, I'm interested to see how it holds up. https://www.ar15.com/media/mediaFiles/60540/1000004251_jpg-3479635.JPG Nice, and cool sight. |
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Originally Posted By SGT-Fish: https://i.postimg.cc/bJY8jkrx/20250224-164616.jpg I got lucky and bought 20 of these demilled 81mm fin sets for relatively cheap. I'm going to make some 3dprinted bodies for them so I don't have to make my own fin sets. For the price I got them, it doesn't make sense to print them. I still need to get my italian tube and cup separated and work on a firing pin. I'm not really expecting to have it done before the big event. But maybe I'll at least have some rounds made for others to try out. Shameless plug https://chevtecgroup.ticketspice.com/chevtec-shoot I got lucky that I randomly stumbled upon the thread and also bought a handful for an amazing price. Another source was about $10 more expensive.
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Originally Posted By walkinginadangerzone: I got lucky that I randomly stumbled upon the thread and also bought a handful for an amazing price. Another source was about $10 more expensive.I actually bought 10 from each source. So I'll split the difference when I think about cost per round. But sir plus supply said they are interested in setting up a table at our event to sell some stuff and maybe donate to the prize table. So that's cool |
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Originally Posted By SGT-Fish: I actually bought 10 from each source. So I'll split the difference when I think about cost per round. But sir plus supply said they are interested in setting up a table at our event to sell some stuff and maybe donate to the prize table. So that's cool Originally Posted By SGT-Fish: Originally Posted By walkinginadangerzone: I got lucky that I randomly stumbled upon the thread and also bought a handful for an amazing price. Another source was about $10 more expensive.I actually bought 10 from each source. So I'll split the difference when I think about cost per round. But sir plus supply said they are interested in setting up a table at our event to sell some stuff and maybe donate to the prize table. So that's cool Oh nice. |
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Originally Posted By MHIDPA: Thanks for the heads up on the fins.  The threads are s little bit rough on some of them. So I'll have to see how I want to tackle that issue. I even thought about just cutting them off and the. Welding a 3/4in nut on to interface with the allthread of a printed round. Especially since a hole would need drilled in the end for easy reloading anyway |
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Originally Posted By MHIDPA: Just want to keep the thread alive. Has anyone made progress on a spotting fuse? So I have a new spotting fuze design. And it's super simple. I took the 40mm point detonating round made by launcherpope, and grafted it onto my 40mm chalk nose cone adapter. This design is much simpler than anything else I've seen. And honestly I am not a huge fan of it for 40mm launchers, where it's getting launched inside of an aluminum tube held in your hand. And its not as reliable for detonation in 40mm due to glancing impacts and off-angle hits. But it is about perfect for mortars. With black powder, it'd be harmless if it detonated in your tube. And the fin stabilization makes impact detonation very reliable. Another guy has already tested a bunch of these with his 60mm and had a great 100% success rate. You just fill the chamber with BP(it holds less than 1/4ounce), cap it with a 209 primer, glue the nosecone on, then thread in an m3 screw as the firing pin, but back it off 1/4-1/2 turn once it bottoms out. I've already adapted it to 50mm and I will for 81mm as well. Gotta do some drop testing from tree house and then live fire. Also sending some to another mortarman for testing in 50mm.  
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Originally Posted By SGT-Fish: I actually bought 10 from each source. So I'll split the difference when I think about cost per round. But sir plus supply said they are interested in setting up a table at our event to sell some stuff and maybe donate to the prize table. So that's cool Originally Posted By SGT-Fish: Originally Posted By walkinginadangerzone: I got lucky that I randomly stumbled upon the thread and also bought a handful for an amazing price. Another source was about $10 more expensive.I actually bought 10 from each source. So I'll split the difference when I think about cost per round. But sir plus supply said they are interested in setting up a table at our event to sell some stuff and maybe donate to the prize table. So that's cool Where did yall find the tails sections, and are there more? |
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Originally Posted By Sonoran_Tj: Where did yall find the tails sections, and are there more? Originally Posted By Sonoran_Tj: Originally Posted By SGT-Fish: Originally Posted By walkinginadangerzone: I got lucky that I randomly stumbled upon the thread and also bought a handful for an amazing price. Another source was about $10 more expensive.I actually bought 10 from each source. So I'll split the difference when I think about cost per round. But sir plus supply said they are interested in setting up a table at our event to sell some stuff and maybe donate to the prize table. So that's cool Where did yall find the tails sections, and are there more? Sent you a link. |
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As much as I'd hate to cut up these fins we got, I'm thinking I'll just cut the threaded portion off and then weld on a 3/4" nut to interface with the allthread I use in my 81mm printed bodies. That'd also leave a good size hole to punch out the spent blanks. And the threads are already demilled. So I'm only making them a little worse. I'll probably grab the ones I have with the worst threads and start with those.  I was filling a few 50mm rounds I made for a friend, and decided to go ahead and fill a few 60mm I had ready and the one 81mm I made a while back but never finished. Now I have an excuse to since I have all these fins. Though I'll probably still assemble a set of printed 81mm fins as a proof of concept. I also have thirty 50/60mm fin stems on the way from a machine shop. So I gotta make more 60s to stock up. |
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Range report/AAR I took a PD nose out to test, upon firing the fins experienced "rapid unplanned disassembly" this led to unstable flight and the round didn't land on the PD nose. Before: Attached File After: Attached File I also tried using one of the surplus Fins that I welded a nut onto (don't judge my welds) Attached File A few notes from these. The base is too loose of a fit for a 12ga. and the recess puts the primer below flush. I dropped the round twice at 75° and it wouldn't fire. My field expedient solution was to wrap a piece of paper around the hull for a tighter fit and to make it protrude a little bit. This solved the misfires. The second issue I encountered was that my rounds didn't stabilize and didn't fly as far. I'm assuming it's just an aerodynamic issue and I'm going to add a stem to see how that works. I've noticed that 81mm tails tend to have longer stems. |
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Thanks for the notes. It is interesting that you had stability problems. While I know the longer rounds do stabilize better, and that why they were developed, many countries still use the shorter round without too much issue. I'm also gonna have to see how a regular 12ga round differs from the standard M3 charge. I have one M3 charge and a dozen or so more on the way just because I got a good deal on them, I know they have the bulge in them to keep then seated, but didn't think they sat too deep. |
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Originally Posted By SGT-Fish: Thanks for the notes. Â It is interesting that you had stability problems. While I know the longer rounds do stabilize better, and that why they were developed, many countries still use the shorter round without too much issue. Originally Posted By SGT-Fish: Thanks for the notes. Â It is interesting that you had stability problems. While I know the longer rounds do stabilize better, and that why they were developed, many countries still use the shorter round without too much issue. I'm sure it is a function of my body design its center of gravity is probably wrong for the short fin. I'm also gonna have to see how a regular 12ga round differs from the standard M3 charge. I have one M3 charge and a dozen or so more on the way just because I got a good deal on them, I know they have the bulge in them to keep then seated, but didn't think they sat too deep. My fins are threaded for the M6 primer. I think it may actually be an issue of the shell moving and softening the blow, not actually a lack of protrusion I think a wrap of electrical tape over the brass will solve it without welding anything up. |
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I got to shoot in a little bit bigger area this weekend. Bumped up to 65 and 75gr loads (TiteGroup). I am a little disappointed with my performance. I only got 170ish yds @55 degrees. We did get MV reading with a Garmin 240fps. My 3D Printed, concrete filled rounds weigh just over 3lbs. And they have an OD of 3.150" (80.01mm). I'm wondering if I have too much windage, or if the round is too light and not building pressure. I'm also wondering if the "flat spot" at the maximum diameter is too short. Currently it is .528 with 3 grooves. What do you guys think? |
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I'll weigh my steel rounds when I get home. But OG shells of this type, for example, the US M43A1 with filler were around 7lbs. With the M6 ignition cartridge (upgraded from M3) containing 120grains of powder, with a FPS of 238 and max range of 565 yards with the ignition cartridge (charge 0). The only US round I could find info on that still used the M3 ignition cartridge was the 81mm M68 training round (and some flare rounds, but focus is on tear drop style mortar projos) that is just a solid projo, weighing in at about 10lbs. The M3 cartridge containing 120grains of powder, and when used with the M68 has a ballistic data of about 172FPS, with a max range of 310 yards. Referenced from the various tech manuals available. Unfortunately I don't have a chrono to get my MVs from my launch charges, but so far I'm getting 190yds with 50grs, at 50 degrees using bullseye. The last outing I went, I reached 190yds, with 60grs, at 66 degrees. I'm finally going back out to test out more cartridges this weekend, at 70grs, 80grs, and 90grs. Goal is 120grs for the launch charge to mimic the OG m3 or m6 ignition cartridge. Also note, the rounds usually have 3 bourrelet (rings), the blue one you posted has two (I'm assuming this is your standard shell). That could have something to do with it. |
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Originally Posted By MHIDPA: I got to shoot in a little bit bigger area this weekend. Bumped up to 65 and 75gr loads (TiteGroup). Â I am a little disappointed with my performance. I only got 170ish yds @55 degrees. We did get MV reading with a Garmin 240fps. My 3D Printed, concrete filled rounds weigh just over 3lbs. Â And they have an OD of 3.150" (80.01mm). I'm wondering if I have too much windage, or if the round is too light and not building pressure. I'm also wondering if the "flat spot" at the maximum diameter is too short. Â Currently it is .528 with 3 grooves. What do you guys think? I'll have to measure the rounds I have and the one I made. I usually try to size them so that they drop with just a slight slowdown in drop velocity. I have a handful of M3 and M6 charges that I thought about using just to see how far a printed round would go, and to "proof" them for full charge zeros. I need some m4 60mm shells too. |
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Well, I'm running out of degrees of angle on my tube for my 200yd range. 70 grains at 70 degrees on the tube for a 200yd splash zone. I'm gonna guess, 80 grains puts the tube at 80 degrees for a 200yd splash as well. Only thing left to play with is where rounds with various load lift charges at 89 degrees end up. Tried out a US mortar fin assembly, ended up using two pennies for spacers between the lift cartridge and the bottom of the chamber. They worked out great, kept the 12 gauge shell sitting a just a bit out but stiff enough that the firing pin still set it off. Placed a little bit of electrical tape around the brass just to keep it in place. |
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Originally Posted By walkinginadangerzone: Well, I'm running out of degrees of angle on my tube for my 200yd range. 70 grains at 70 degrees on the tube for a 200yd splash zone. I'm gonna guess, 80 grains puts the tube at 80 degrees for a 200yd splash as well. Only thing left to play with is where rounds with various load lift charges at 89 degrees end up. Tried out a US mortar fin assembly, ended up using two pennies for spacers between the lift cartridge and the bottom of the chamber. They worked out great, kept the 12 gauge shell sitting a just a bit out but stiff enough that the firing pin still set it off. Placed a little bit of electrical tape around the brass just to keep it in place. Now we are LITERALLY just sending money down range! 😄 🤣 😂 😆 |
Also if I'm not mistaken, the long boy 81mm bodies like the M374 with the obturating ring produces more pressure in the tube and flew further at a higher angle compared to the tear drop mortar bodies.  Originally Posted By SGT-Fish: Now we are LITERALLY just sending money down range! 😄 🤣 😂 😆 Originally Posted By SGT-Fish: Originally Posted By walkinginadangerzone: Well, I'm running out of degrees of angle on my tube for my 200yd range. 70 grains at 70 degrees on the tube for a 200yd splash zone. I'm gonna guess, 80 grains puts the tube at 80 degrees for a 200yd splash as well. Only thing left to play with is where rounds with various load lift charges at 89 degrees end up. Tried out a US mortar fin assembly, ended up using two pennies for spacers between the lift cartridge and the bottom of the chamber. They worked out great, kept the 12 gauge shell sitting a just a bit out but stiff enough that the firing pin still set it off. Placed a little bit of electrical tape around the brass just to keep it in place. Now we are LITERALLY just sending money down range! 😄 🤣 😂 😆 Needed a faster way to get rid of my money. |
81mm Mortar barrel/tube/build info (Page 12 of 15)
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