Where does one get ammo?

Bowman just imported a bunch of demils, just need to weld up the holes. Plenty of different rounds can be found that are old surplus. Launch charge is typically a 12ga blank.

DDs aren't something you buy ammo for at Walmart or midway USA.

Unfortunately, I believe he sold out of those.

Edit: also looks like they may have a handful of these mortars back in stock.

I have a lathe... I'm going to try and come up with something of my own. I think @Ben might be working on something too.

What is the tube length on these?

About 57 1/2 inches.

Well... I ordered one. Now to decide whether I'm going to buy a barrel, or cut/rebuild/thread the original.

I don’t expect it to be like buying 5.56, if I gotta wire money and wait 18 months that’s fine. As long as it can be done.

It should be interesting to see if the 3d printed practice rounds hold up to the launching charge.

Sounds like things that could be adapted to 81mm...

http://www.buckstix.com/CoehornMortarHunt.htm

NGL I eventually wanted to do this but with wild pigs. Unfortunately, there isn't any around.

Where are some good resources for DD mortars/ammo/loads etc?

"small arms and trench warfare" section. I might have a manual on the older modern shells and ignition info but need to look for it and update this post if I do. But google 81mm mortar M3 cartridge and start clicking links.

http://www.90thidpg.us/Equipment/Weapons/81mmShells/M43/index.html

https://www.bulletpicker.com/pdf/TM%209-1904,%20Ammunition%20Inspection%20Guide.pdf

https://www.bulletpicker.com/pdf/TM%209-1300-203,%20Artillery%20Ammunition.pdf#page=285

Click through the various 81mm mortar rounds on the left menu and go to the "sources" section of the ammunition and it will link some manual that provide more info.

https://www.bulletpicker.com/cartridge_-81mm-he_-m374a2-and.html

https://www.bulletpicker.com/technical-manuals.html

I'm waiting on the kit to get here so I can take measurements and efile, but based on what I have seen here, I am planning on cutting the tube above the hole. Then making a 4140 sleeve with a .001 interference fit, pressing it on and welding it around the top and bottom. Then turning/threading it to fit the cup. Does that sound reasonable? I doubt I'll ever get above a charge 0 or 1.

Not sure if it was a stupid idea or if people are afraid of being held responsible for internet engineering.
I'll ask another question.

My understanding is that the Cup is the registered receiver. Can one make sub caliber barrels like changing uppers on an SBR?

I. E. Do a form 1 as 81mm and make a second barrel that is 60mm?

Yeah you could do that. There are surplus kits out there that are subcal to 25mm-ish. They use 22 blanks for launch charges and impact spotting. The kits have different bushings so the subcal tube will fit in different size mortars. I suppose you should be able to go from 81mm to 60mm, though your barrel will be longer than a regular 60mm. Could be an interesting product and source for cheaper ammo

I know the military had a 60mm subcaliber adapter kit for short range training with 4.2in M30 Mortar, a 60 tube with proper spacers to center it in the M30 Cannon.      My NJARNG unit accidentally hit a tree with one at Ft Dix, the crew didn't pay attention to Mask & Overhead Clearance.  That's one of the standard safety checks the Gunner is supposed to perform before live fire, you lower the tube to 0800 mills, (the lowest angle that achieves the Maximum Effective Range) then places his head on the barrel cup looking the length of the tube to ensure there is nothing in the flight path of a round at that setting, then the same is done with the tube at maximum elevation (for the particular mortar system, 60mm, 81mm  & 120mm use both charge and elevation setting to adjust range, the 4.2in mortar uses 3 fixed tube elevation settings with distance in between adjusted by fractions of the 'cheese" charges, 2 thin sheets sewn together = 1 Charge, each quarter of a single sheet is 1/8 charge).  Anyhow, the crew didn't preform their pre-fire safety checks, hit a tree top with a 60mm HE round that didn't travel far enough to arm the fuse just bounced off scared the shit out of the whole gun line.

I thought there was a 60mm insert for the 81mm M29 (and M29A1) Mortar at one point.   I know we used both the pneumatic subcaliber, miniature round training device and the 22mm sabot sleeve training systems while stationed in Berlin 1989-90 then 1992-94.   The 22mm Sabot system used a machined steel ballistic shaped sabot that had a screw on base cap that held the 22mm subcaliber cartridge in the the sabot's barrel.   You would hang then drop the round in the M29A1 or M252 Mortar like any other full sized round, it would hit the firing pin detonating a primer that would ignite the propellant charge that would push the 22mm projectile out of its aluminum casing.  The 22mm projectile would travel downrange several hundred meters (depending on which Charge 1-4 I believe) hit the ground then makes a small puff of smoke and explosion.  The propellant gases are vented between the Sabot and cup, with enough residual energy to push the entire Sabot out of the barrel, landing about 10 or 12 feet in front of the mortar.  These 22mm Sabot are extremely dangerous when loaded with the Cartridge, there was a soldier in the Brigade who dropped a loaded Sabot inside the Mortar Carrier track, it hit the turntable on the corner, striking the primer, the projectile entered the soldier's skull from under his chin, into his skull, he died while the surgeons were waiting on EOD to arrive to Safe the projectile.
Attached File


The Pneumatic Subcaliber training system, there was even a miniature village built in one corner of the training area for use of the little plastic with metal weight training rounds, so you could use the M19 binoculars with mil recticle to practice Call For & Adjust Indirect Fire.     It wasn't much benefit to the Mortar Crew because it was so much different from firing live rounds.   Inside the American Sector we had small arms ranges for Rifle, Pistol and 40mm TP, but we could not live fire the various Mortars in an Infantry BN, only the 22mm Sabot Device or the Pneumatic Training System.

Here is an excellent  document on Mortar Training Devices from the FM 23-90 2002 edition, the Bible for 81mm Mortars, that demonstrates the 22mm M1 Sabot as well as the Short Range Training Round Systems for the 81mm and 4.2in/120mm Mortars:   FM 23-90 Appendix A
The FM 23-90 1951 edition cover the WWII to Korean War era M1 81mm Mortar System.  This is probably the closest in similarity to the Yugoslavian M69 81mm Mortar in handling and safety procedures.
The FM 23-90 1972 edition is going to cover the M29 and M29A1 81mm Mortars.
The FM 23-90 1990 edition is going to cover both the M29A1 and M252 Improved 81mm Mortar Systems.

FM 23-91 is Mortar Gunnery, that's all the black magic joooo joooo that goes into calculating the firing data (Deflection Angle [left to right between cannon's direction and direction to the aiming posts] Charge placed on the round, and Elevation [angleof the mortar tube from horizontal] needed to drop the round at point not visible by the mortar crew itself.

If you are going to mess with these things with energetic projectiles you should learn the proper round handling and misfire procedures.  

Thanks for all this info. I appreciate it.

Thank you. I'll definitely be loading up some FMs.  To be clear, I'm not talking about an insert, but a separate barrel with threads that fit the cup, a wide spot for the bipod collar to clamp onto, and a 60mm appropriate bore.

No matter the configuration of your cannon tube, you still must learn :
1) Correct and Safe way to hang then drop the round;
2) Correct and Safe way to remove a misfire from the cannon tube.

You never pass any body part over the cannon muzzle.  As you release the round, both your hands follow down the length of the cannon then you pivot away to protect your face from the muzzle blast.  

Most of what folks are dealing with here will not have a mechanical, point-detonating fuse, so you just turn the cannon tube upside down then dump it directly onto the ground.
  Some of those T.R.U.M.P. rounds have a mechanical fuse with a firing pin that strikes a primer to detonate a spotting charge.     But still, if the misfire is actually a hangfire, or that T.R.U.M.P. fuse impacts your hand with enough momentum you can injure your hands and fingers trying to remove it.   When that cannon tube is being lifted above the horizontal plane to dump it out you allow only the meaty portion of your palms to protrude into the bore line to catch the round.   IF the round is a hangfire, then you may incur a flesh wound vs losing your thumb and/or finger(s).  
  This video is a pretty good demonstration of M252 81mm Mortar Misfire Procedures, starting after the 1 minute cool down period, during which the entire crew moves behind the mortar system.   There were some problems with the Marines' 60mm M224 LW Mortar Systems having HE Rounds detonate inside the cannon tube several years ago.  The

 The FM 23-90 Chapter 4 Section 14 cover Misfire Procedures on the M252 81mm, the bipod has a similar split locking collar that secures the cannon tube, the M252 using an L handle the M69B has a cast 6 point knob, but the procedure would be similar if you have to rotate the cannon tube to either access the firing pin for removal, or to release the firing pin ball from the baseplate socket.   If you have some pics of the cup assembly and firing pin I can help examine that.

1. Any member of the gun crew who notices the misfire shouts out "MISFIRE!" loud enough for the entire crew and surrounding personnel to hear (peace time at least)
2.  Gunner performs immediate action, kicks the tube several times with his heel to attempt to dislodge it.    If the round fires the mortar is relaid back on the aiming point (actual aiming posts, target if direct lay, or distant aiming point when aiming posts cannot be used) then firing resumes.  If the round  does not fire the other crew members move approximately 50 meters behind the mortar position, Gunner remains.
3.  The Gunner feels the barrel for heat.  If the barrel is cool enough, the crew removes the round by following the procedures, if too hot the Gunner can pour water on it until the outside is cool enough for handling. If not water available the Gunner joins the crew 50 meters away while the barrel cools.
4. After 1 minute the Gunner returns to the mortar, tests the barrel if cool enough to handle then calls the rest of the crew back to the gun.
5. Gunner removes the sight unit and firing pin, this ensures the mortar doesn't fire if accidentally lowered below the horizontal during handling.    Cranks the elevation down to lowest point, loosens the barrel locking collar on the bipod to allow the barrel to rotate 90 degrees to allow access to the firing pin socket then locks the locking collar.
6. Gunner stradles the left bipod leg assembly to support it during the procedure and grasps the barrel with handles top and bottom about 6 to 12 inches from the muzzle. The Assistant Gunner places his hands around the sides of the muzzle, not yet over the edge of the muzzle.  The Ammo Bearer grasps the barrel near the cup, hands on top and bottom, gently and smoothly lifts the firing pin cup ball out of the base plate socket, slowly lifting the barrel above the horizontal plane until the round slides into the AG's hands. When the barrel reaches the horizontal plane the AG moves the meaty portion of the side of his palms over the muzzle lip to catch the round then removes it from the barrel.    The AB shakes the barrel to dislodge any foreign objects or remaining portions of the last round fired.  

(sometimes a charge bag can slip off the clip, lodging between the round and barrel, either jamming it part way or slowing its movement enough there is not enough momentum for the firing pin to detonate the primer, this was particularly the case with the older M300-series rounds with the fabric charge bags that attach to the fin tube by T posts on metal clips that are screwed onto the fin tube top and bottom, later M800-series rounds use the styrofoam horseshoe shaped charges that clamp over the fin tube; sometimes part of a charge bag or clip or other piece of the previous round may be left in the barrel causing the misfire)

7.   The AG hands the misfire round to the AB who inspects it for the cause of the misfire. If the primer is dented, the AB attempts to replace the safety pin wire in the fuse, then moves the round a safe distance down range, for EOD to dispose of. If the primer is not dented the round may be reused.  The firing pin is replaced and the barrel swabbed. Sight is installed and mortar is relaid back onto the aiming point, firing resumes.

8.  If the crew is unable to dislodge the round from the barrel, the entire barrel is kept horizontal, unlocked from the bipod then moved down range to the designated Dud Pit without being allowed to move past horizontal, then carefully laid on the ground for EOD to dispose of the round.    
(My experience, the EOD will get a pick mattock handle off the Humvee HMMWV or Mortar Carrier Track (or Stryker these days, they will turn the barrel upside down the beat the heck out of the barrel with the wooden mattock handle until it falls clear which for the old 81mm and 4.2in/107mm M30 was usually enough.    I assume there is a rod tool with a claw that can grasp the fuse assembly that is used as a last resort since the EOD tech will have to place his hands within the boreline to use it)

I think it isn't reasonable to think an owner is going to have himself a full time, well-trained "gun crew" in order to practice the Misfire Procedures, but as an owner, perhaps having them written on a reference card that you can brief your helpers with prior to range use or in event of a misfire you can go over the procedures before actually doing them.      
   We were trained on these procedures, the crew would practice them during Crew Drill, then there were times the unit would be evaluated by an outside unit under simulated tactical conditions called a MORTEP Mortars Training and Evaluation Program, a crew would be picked at random to perform the Misfire Procedures or even each gun crew would be evaluated one at a time.

Got my kit in today. It has a traverse knob that is new, and it looks like I'm going to have to make a bushing to keep the traverse screw from coming out of the bipod.  It's also missing the inert round that it was supposed to come with. Overall everything else is as expected. I'll efile a form 1 soon.

I thought Comm-block mortar tubes were 82mm and western tubes were 81mm.  

Assumed anything coming out of Serbia would be of the 82mm variety.

Edited: After research conducted the M69 had both a 81mm and 82mm version the M69B was the 81mm NATO version.

Thanks for the write up. I was reading up on the misfire procedures a while back. But it's great to get a refresher course.

Here are pics of the cup assembly. The yugo M69B mortar cup has a safety built in, when placed on "Safe" it moves the firing pin down into the firing pin channel within the cup.



Safety being activated.



And in order to access the firing pin.

BTW Stoner63a, have you seen a hangfire round ignite and fire while the tube is in the horizontal plane during the misfire procedures? How bad is the wound on the meaty part of the palms?

Have you ironed out your barrel situation?
I think I'd patch and weld the large demill hole, and plug weld the smaller hole in the threaded section (of the barrel). The machine shop can clean the bore and threads, post weld. Also, cut the start of the barrel threads by ~45 degrees and/or remove a bit from the start of the barrel (where it would bottom-out). This will make sure the two holes never align again.

CDS tube, especially in the size you need, is going to be costly.
Machining said tube might cost more than the material itself.
You have options ;)

Yeah, that's my plan. Got a brass backer in order to weld in the OG "cookie" that was cut out for the demill. I just haven't had the time to go to a machine shop locally to have them weld it on. Still need to get a ring to put over the welded part tho.


But Hamilton and Son's firearms are also making a run of barrels for these yugo imports which I'm going to get.  Last update I got from dangerous bob was they may have got a final estimate price on ordering the material. So they're getting close.

Interesting thread, I have one of the M69A 82mm de-milled kits from APEX IIRC I got it in 2015. Has the bore size hole in the cup and a pin welded in the barrel.

Took it to a local paint shop, who sand blasted it and painted it in a matching green. Came out looking very nice and a made for a conversation piece in the study.


Did see this, which I thought was a neat submunition trainer and avoids much legal hassle: https://www.youtube.com/watch?v=mLkNWYtz1AQ

Nice, just ordered some paint and hoping to get the base plate done this weekend if weather permits. The sub munition trainer is a pretty cool addition to the 60mm mortar.

Finally got a sunny dry day in the weekend and was able to refinish the base plate. The top was easy to strip using a grinder and some stripping discs. The bottom on the other hand was kind of a pain because of all the welded supports and 90 degree angles. Original color was more of a "yellow olive" (according to Crosslink's color plates) but decided to go with a more Eastern Europeany lighter green, and went with "olive green". Hindsight, I should have just taken it to get sand blasted, would have been easier.


Was almost done removing most of the paint, just needed a bit more around the cup when I remembered to take a pic lol.



Primed


Re-Painted bottom


Re-painted top.


I'll see when I can get to doing the bi-pod next.

The ordnance fairy stopped at my house yesterday. Attached File

Nice, did you fab the adapter yet?

Nice score, all that gets demilled through Cap'n Crunch now.

Is that the Korean War to Vietnam M74 Sight?

We used the later M53 Sight Unit with the M109 Telescope Elbow on both the 81mm M29A1 and the 4.2in 107mm M30 Mortars.  The M224 60mm used the M64 tritium illuminated sight unit from the beginning.    Then when Big Army adopted the UK MOD  M252 Improved 81mm Mortar System it also used the M64 Sight Unit.

The M53 used a separate battery powered  Instrument Light M53E1 with one cable with a threaded light housing for illuminating the M109 Telescope Elbow (the screw cap with ball chain on yours) crosshairs and a separate squeeze button light for operating the sight unit, from indexing the Elevation and Deflection for the fire data and for checking the crosslevel bubbles.     It was also used for laying in the Gun by the M2 Aiming Circle and setting your aiming posts during night occupation of the FP.
Attached File


The earlier M74 Sight Unit I think has a dovetailed receptacle for the Instrument Light M33 or M50, which was also a component of the M2 Aiming Circle.
Attached File

Some Gunners thought it was easier to keep a AA or AAA Mini Maglight with red lense on our LBE for checking the Deflection and Elevation scales and crosslevel bubbles.

Your Mortar Section would also have a sheet steel M14 storage case for 2 D cell powered Aiming Post Lights.  The Early kits had interchangeable lense covers in Red and Green for differentiating your far post from your near and from the gun(s) next to you, the section would alternate near and far light colors to make sure you didn't align your Gun on your neighbor's posts in error.    The later aiming post lights were plastic housing, still powered by D Cells 9 (BA30's?) but had a toggle switch to change the LED from Red to Green.

It matters how you align your sight unit vertical crosshair with our aiming posts, because of the angle difference between the Gun->Target azimuth and the offset your sight unit and aiming posts are layed on (so the mortar muzzle/bipod [or Mortar Carrier Tracked Vehicle] doesn't get in between your sight and aiming posts your sight is offset to the left hand side by about 60 degrees/1066mills)

No, just got it. Haven't even looked at what I'll need to do for the Yugo.


No, it's an M53a1 with M109

Got my stamp today! 8 days from submitted to approval.

Yes.

Damn, noice! Already cleaned and refinished my base plate and bi-pod. Just waiting on the barrel now.

Did you order one from Bob?

Yeah, I think I might have been the first one to get it as he didn't know about the issue.

@walkinginadangerzone do you want me to start my own thread, or can this be a consolidated 81mm mortar thread?

Does anyone have opinions on fusing? I've seen various setback safety designs, but what about the TRUMP style PD fuses that just have a safety pin to be removed before firing. It seems that would be enough for spotter/chalk rounds. Thoughts?

I don't mind if anyone wants to expand this thread with more info or anything else they'd like to share. Totally up to you man. If you'll decide to expand this thread, I'll change the title to represent all this info for future readers.


That said, as for the spotting fuzes like a TRUMP fuze, it's a really simple design and should do well for the application. Get some cotter pins with split rings (both available in McMaster-carr) to use as the safety bar that prevents the cup from moving forward and striking the firing pin in case of an accidental drop. Then when ready to fire, just pull the ring that's attached to the cotter pin like a grenade, hang, and fire.

I was actually thinking of modding the fake fuze on the italian/french rounds that bowman had into a small spotting fuze head more similar to the Bonetti rounds instead of the TRUMP rounds. That way you can use any shells and don't have to modify them so they also keep their value. The firing pin set up would be like the Bazooka Base detonating fuze. @ 4:30 in this video.

The fake OG fuze head would house the shot shell blank (thinking of a 28gauge as there isn't much meat on the side walls to house a 20gauge blank let alone a 12 gauge blank) with the primer facing the inside of the shell, then a washer placed between the fuze head with the shotshell, and the firing pin tube/holder, these would screw on the thread adapter ring in these shells. The washer will hold the shotshell in place and it itself would be held in place between the fuze head and the firing pin tube/holder. I'll post a mock up pic of the idea later today.

There's some M751s available, but they're pretty much a one time use unless you mod them. Are yours going to be reusable/reloadable? It'd be great if we could get a couple firings out of them before needing to be replaced.

Well, looking forward to what you bring out.

Cheap because they will be inexpensive to manufacturer, or cheaper because you are subsiding them? Are you planning on designing them for 12 or 20Ga?

Side note, I'd love to have some non reusable illum/air bursting rounds for Independence day.