Author Topic: Safe charge for new salute mortar/thunder mug (Read 1891 times)

Cannon salute · « **on:** November 02, 2011, 03:48:10 PM »

Hi all, I have a new salute mortar made from 1018 cold rolled steel with the following specs: 1" bore all the way, no powder pocket, 0.70" walls, 2.3" deep bore, .70" breech wall with .50" plate welded on to a combined thickness of 1.20", overall dimensions 2.4" diameter by 3" long
That said what would be an appropriate charge for it? I have been told that the finer the better, since it is only for blank loads. Some people say use cannon powder, while others say even finer than FFFFg will work. Some say pack it with a ram rod others says don't pack it. I spoke with a guy who manufactures explosives for a living and he said finer is better and that a wad is not needed. He reccomended at least FFFg and said he uses a powder finer than 4Fg in his concussion mortars. Any advice is appreciated thanks

GGaskill · « **Reply #1 on:** November 02, 2011, 08:45:57 PM »

I am concerned about your description of the breeching process. It sounds like the bore is closed by a flat plate that is welded at the outer edge. If this is the case, it is a dangerous construct as the plate will get bent in use from the pressure and eventually allow gas pressure to operate over most of the interior plate surface. The bending of the plate will also be stressing the weld and increase the likelihood of separation.

If the above inference is correct, the problem could be corrected by drilling through the bottom plate, pressing in a breech plug that is a little oversize for the bore diameter and extends above the original joint, and welding that in place. It would be best to open up the hole in the plate so you could make sure the weld seriously connects with the barrel portion as well as the plate portion.

Mike H. · « **Reply #2 on:** November 02, 2011, 11:03:54 PM »

I read it as being a solid 3" long blank of 2.4" OD, drilled 2.3" deep, with a 0.5" plate welded to the bottom, increasing the bottom thickness from 0.7" to 1.3".

Is that correct?

Cat Whisperer · « **Reply #3 on:** November 03, 2011, 12:43:30 AM »

Cannon salute -

WELCOME tothe board!

Some coments:

1018 - GOOD!

One piece - drilled - GOOD!

Bore one inch, wall thickness of 0.7" - not good. Bore should be 1/3 of the O.D.

1.3" under the breech end - would be good if it was to the end of the tube. Is effectively 0.8" (1.7 less the 0.5" plate).

I don't like the weld being that near the powder chamber.

Powder - the finder the powder the higher the pressure. Problematic - you need a good pressure wave for noise, but that pressure peak at the beginning of the burn is a killer. If you use this at all, use a coarse powder with a cardboard wad.

For the price of steel and labor I would start over. You have to KNOW if it's a bomb or a mortar when you light the fuse.

flagman1776 · « **Reply #4 on:** November 03, 2011, 03:41:40 AM »

Cannon salute · « **Reply #5 on:** November 03, 2011, 05:10:41 AM »

Quote from: Mike H. on November 02, 2011, 11:03:54 PM

I read it as being a solid 3" long blank of 2.4" OD, drilled 2.3" deep, with a 0.5" plate welded to the bottom, increasing the bottom thickness from 0.7" to 1.3".

Is that correct?

Yes that's correct, it's has .7" breech wall plus the .50" plate welded on

Cannon salute · « **Reply #6 on:** November 03, 2011, 08:09:03 AM »

Ok let's say I make a new one we will start with a 6" diameter by 8" long 1018 cold rolled round and we will bore it 2" in diameter and 4" in depth with no powder pocket. I will attach a diagram of the design soon. Any recommendations, such as different metal or adding a pocket etc, to make the design safer and or better are welcomed.

Double D · « **Reply #7 on:** November 03, 2011, 08:55:50 AM »

Chamber not pocket.

What are you building a replica of some pre 1899 mortar or a thunder mug?

Cannon salute · « **Reply #8 on:** November 03, 2011, 10:52:17 AM »

Really a mortar, but just for blank charges no projectiles will ever be fired from it which is why I omitted the powder chamber.

Cannon salute · « **Reply #9 on:** November 03, 2011, 11:18:02 AM »

Here is the first diagram I'll get the internal view soon.

GGaskill · « **Reply #10 on:** November 03, 2011, 11:21:50 AM »

That's going to be REALLY heavy. Around 60 pounds.

Cannon salute · « **Reply #11 on:** November 03, 2011, 11:28:53 AM »

Here is the internal view.

As far as the weight at least I know it wont blow up on me. I'd rather have overkill than too little metal.

Mike H. · « **Reply #12 on:** November 03, 2011, 11:36:24 AM »

If you are only planning for salutes, I recommend stopping at 1" bore for mortars or mugs. In my experience larger than that is not "powder efficient". Side by side, I can make the same salute noise with my short 3/4" bores as with my short 1"'bores, and using much less powder in the 3/4" bores.

Try a 3" blank with a 1" bore about 6" long. Leave 1.5" thickness on the bottom and weld on the trunnion.

Cannon salute · « **Reply #13 on:** November 03, 2011, 12:01:26 PM »

Well, I will only shoot it probably twice a year so powder costs is not an issue and I do want a big boom, and it takes a large concussion to impress me. I always hear people lighting off M-80s and the like during New Years and the Fourth and it never really impresses me after being at events with explosions and cannons etc. So if a bigger bore makes a better boom it's worth the extra cost for me. You guys are probably far more experienced than me so whatever is better in your experience I will take into account.

flagman1776 · « **Reply #14 on:** November 03, 2011, 01:10:57 PM »

Soot · « **Reply #15 on:** November 03, 2011, 01:25:27 PM »

My 1" bore thunder mug is so loud I have no desire to make a bigger one.

Cannon salute · « **Reply #16 on:** November 03, 2011, 04:02:35 PM »

Quote from: flagman1776 on November 03, 2011, 01:10:57 PM

Any mortar or cannon should have some radius to the chamber to reduce stress & avoid sharp corners which might hold a spark. You will need proper tools: a worm, wet mop, dry mop, rammer, a brass vent pick to clean the touch hole. A small bore brush for the same... (Some have used 177 cal brushes).
A straight bore is easier to load... and service (clean). Personally, I'd not go huge... at least not a first attempt.
Leave somewhat more metal under the breech than the wall & you'll know you have not left a weak link. A 1" bore would see a lot of use.
PS Let the neighbor's know in advance... The neighbor's enjoy my 4th salvos... have sometimes walked out on their docks to request "a few more". Better than calling the cops. My gun is loud enough that a recent combat vet, arriving the party as we cut loose... was observed getting out from under his car! Observe all safety precautions & clear the safety zone.

As far as a radiused chamber, I will definitely include That in my design, I just forgot to put that in my plans. I want a boom not a bang if I was looking for a bang I'd fire a gun. This will probably be used at a private shooting range where there are other pyro technics used so I want to wow people

Mike H. · « **Reply #17 on:** November 03, 2011, 11:47:31 PM »

Well then get something that wows. Don't mess with a mug. Get a full size cannon.

Cat Whisperer · « **Reply #18 on:** November 04, 2011, 12:17:33 AM »

You might consider a bore diameter of 4.55" with a powder chamber in a mortar (see avitar to the left). It shoots 4" pvc pipe sections filled with concrete. Powder chamber holds about 2 film canisters full of powder. It will chuck a 7-1/2 lb projo about 400 meters on a good day. 100 yard shooting is best - time of flight 8-9 seconds of silence waiting for it to come ripping down through the trees taking off limbs before the ominous thud.

Did I say it's lots of fun? You get everyone's attention with BIG BORE. Mine's made of 4140 but 1018 is more traditional.

Cannon salute · « **Reply #19 on:** November 04, 2011, 05:55:18 AM »

What are the specs on your mortar cat whisperer? Does it have 4.55" walls so it adheres to the 1/3 rule?

Cat Whisperer · « **Reply #20 on:** November 04, 2011, 06:19:22 AM »

Quote from: Cannon salute on November 04, 2011, 05:55:18 AM

What are the specs on your mortar cat whisperer? Does it have 4.55" walls so it adheres to the 1/3 rule?

The OD is about 7", but there is a powder chamber - LOTS of thick 4140 surrounding it and below it. (So the powder chamber more than meets the 1/3 rule; and the rest is overly thick.

I will admit that I've not tried blanks; but shooting cement filled pvc pipe gives a deep mellow booooommm.

Cannon salute · « **Reply #21 on:** November 04, 2011, 09:53:37 AM »

Should I use 4140 instead of 1018, I notice a lot of people are using that.

GGaskill · « **Reply #22 on:** November 04, 2011, 10:26:47 AM »

Unhardened 4140 is about twice the strength of 1018 and costs more and is a little harder to machine. If it makes you feel better, go with it. But 1018 with the 1:1 wall rule is more than enough.

Cannon salute · « **Reply #23 on:** November 04, 2011, 11:28:48 AM »

I'm starting to wonder if it would be more cost efficient to buy one instead of get one machined. I'm starting to think the cost of paying a machinist will be exorbitant. I know a guy who owns a metal fab shop and has milling machines and a lathe, but getting it done manually rather than by CNC will probably be a lot more time consuming and a lit more money.

GGaskill · « **Reply #24 on:** November 04, 2011, 11:58:32 AM »

... but getting it done manually rather than by CNC will probably be a lot more time consuming and a lit more money.

Cost will probably be more related to how much the shop needs the business than to whether it is done on a CNC machine or a manual machine. The CNC will require at least some programming which the manual machine would not.

Cannon salute · « **Reply #25 on:** November 04, 2011, 05:20:03 PM »

I live in California and shops being hard upp for business does not seem to effect the price as much as other places.