Author Topic: 40 MM Rifled Breach Loader (Read 15272 times)

Cannon Cocker · « **Reply #150 on:** April 26, 2012, 05:41:17 PM »

Moose, What if the problem with the bolt isn't that it is out of round before you shoot it but after it has gone down the bore. In some of your previous posts I saw designs showing freebore. Most accuracy buffs agree that too much freebore is bad and that it really only exists to accommodate different bullets that may be put in a gun. Do you seat the bolt up against the rifling? You could also try a bore rider design with an obturation band at the back (basically the same idea as the original 40mm projectile). The front of the bolt would already be aligned if it was seated up to the band. Seems like throwing all that lead into the big squeeze can't be as good as starting out straight in the first place.

moose53 · « **Reply #151 on:** April 26, 2012, 06:23:50 PM »

The lead shell is seated up against the rifling to start , and seems to be engaging the rifling evenly. The steel shell is a bore rider design with a copper band and boat tail , close to the 40mm design .

moose53 · « **Reply #152 on:** April 27, 2012, 03:51:50 PM »

Here is the trial steel shell . It is 1.568 inch dia with a step of 1.518 inch dia for rotating band. The threads are 42 threads/in, rotating band is 1/2 inch long by 1.625 inch dia copper pipe.Note the embossed threads on inside of cut rotating band , they keep the band from spinning on the shell.

Cannon Cocker · « **Reply #153 on:** April 27, 2012, 08:10:43 PM »

Wow. That steel shell looks great. That should be better than an original. If you don't get great accuracy with that thing I wouldn't know where to turn next. Just a little bit harder to make I guess!

Cannon Cocker · « **Reply #154 on:** April 28, 2012, 04:31:35 AM »

Moose,

Since the back end of the projectile (while seated against the rifling) is at a fixed distance from the back end of the inside of the breach, do you use an inert filler to avoid air space. If so, what do you use, and have you experimented with different ones. Also, how do you get that copper band on the shell. Is the boat tail section a separate piece.

KABAR2 · « **Reply #155 on:** April 28, 2012, 04:48:07 AM »

Moose,
Nicely designed projo, I like the bore rider a good idea with that length, I too am interested in how you swedged the copper onto it.....

moose53 · « **Reply #156 on:** April 28, 2012, 05:24:52 AM »

Thanks, Yes I am using old casting plaster (no longer active). It seems to work great , packs very nicely yet breaks up as soon as its out the bore .I will include photos of how the shells are made as I finish the rest of them. The copper band is pressed over the nose and then swedged on shell body.The band is locked on the shell when shot, by pressing into the threaded area.

michaelfreeland · « **Reply #157 on:** April 30, 2012, 03:50:24 AM »

After three years of procrastination, design change and starts/stops, I dropped my 40MM Bofors Barrel off at the machine shop that is doing my Whitworth.
I will post photos of the progress as it unfolds
Thanks to all on the board who have given valuable input

moose53 · « **Reply #158 on:** April 30, 2012, 06:04:20 AM »

Cool

, I love build posts.

moose53 · « **Reply #159 on:** May 01, 2012, 03:56:57 PM »

Redid my vent pick for the 40mm breach loader. It is made from a old porcelain faucet handle with 1/8in brass rod.

moose53 · « **Reply #160 on:** May 06, 2012, 04:21:50 PM »

I set up a manual contour tracer to finish to nose sections of my 40mm shells , very happy with how well it works . The system would be capable of contouring a 24 pounder naval cannon with a little practice .

jamesfrom180 · « **Reply #161 on:** May 07, 2012, 02:57:37 AM »

Thanks for the shop photos, this really helps guys like me see the tooling better.

The Jeff · « **Reply #162 on:** May 07, 2012, 10:56:55 AM »

Quote from: moose53 on May 06, 2012, 04:21:50 PM

I set up a manual contour tracer to finish to nose sections of my 40mm shells

Now that is slick! It's got me thinking which is a bad sign.

moose53 · « **Reply #163 on:** May 09, 2012, 04:17:09 PM »

Yes I know about the thinking part , I run into that too. Used the manual tracer to cut the boat tail , I am starting to like the tracer better then my taper attachment , its easy to use. Also cut the center section and put the threads in( 42 threads / inch , one pass at .015 inch combined depth ) x 1/2 inch long for the rotating band.

moose53 · « **Reply #164 on:** May 13, 2012, 04:50:17 PM »

Pressed the copper bands on today , now ready to fire .

Cannon Cocker · « **Reply #165 on:** May 13, 2012, 05:56:06 PM »

Its a beautiful thing. You're going to think you have a flier when the second shot doesn't increase the size of the first hole.

Cannon Cocker · « **Reply #166 on:** May 13, 2012, 06:01:15 PM »

What is the overall length and weight, and what will the charge be.

moose53 · « **Reply #167 on:** May 13, 2012, 07:06:00 PM »

I am trying to keep it the same as the Hotchkiss mountain rifle . The shell is very close to 2 lbs and starting load will be 5oz . It needs to go more then 1400ft/sec to utilize the shape it has now , if slower then I can round the nose some . I will get the shell length tomorrow .

moose53 · « **Reply #168 on:** May 14, 2012, 03:56:14 PM »

The shell length is 5 in .

Cannon Cocker · « **Reply #169 on:** May 14, 2012, 06:18:53 PM »

It should be over 1400 fps with a charge like that, unless your homemade powder is much weaker than Goex. Not sure what range you're going to be shooting but the transition back below the sound barrier as it slows down is the real accuracy killer. Put the dimensions of your projectile in this calculator to see what kind of ballistics you will be getting. After you get it to draw out your projectile, click on the ballistics button to enter a muzzle velocity and range and then it builds some great plotted ballistics data.

http://www.border-barrels.com/cgi-bin/drag_working.cgi?unit_length=inches&weight_unit=grains&bullet_name=Custom+bullet&re_calculate=yes&diameter=1.57&length=5&nose=2&meplat=0&drive_band=1.67&base_diameter=1.144&angle=12&boat_tail=1&secant_radius=&weight=0&density=7.8

The following will help build it quicker: 2 pounds is 14000 grains and steel is 7.8 specific gravity.

moose53 · « **Reply #170 on:** May 14, 2012, 06:43:17 PM »

That is a cool program , thank you very much . I will get careful measurements and try it out again.

moose53 · « **Reply #171 on:** May 18, 2012, 06:59:49 AM »

Thanks again Cannon Cocker , the ballistic program is very helpful. My cast lead shell is hopelessly over spun , no wonder it was hooking badly . After carefully running the numbers , given a twist of 1 in 40 and keeping the weight to 2 lb , the program gave me a stable design almost identical to the long military 40mm shell .

Cannon Cocker · « **Reply #172 on:** May 18, 2012, 09:06:56 PM »

I'm glad you like that program. I had spent a lot of hours researching ballistics to try to design a bolt for my 2.25" mountain rifle with a twist of only 1 in 120". No surprise that it needs a fairly short stubby round. Was also researching for information in anticipation of a 40mm I am building. When I found that program I was ecstatic....really....I can draw out my projectile, and it will tell me how much it weighs, what my twist rate should be and then plot out ballistics to 1000 yards. Holy S.

I'm not surprised about the program coming up with a design close to what they were using in WWII. I'm always amazed at what those guys did and in such a short period of time.

I got some of the same WWII bolts from the same guys I think. I wanted to see what they looked like to help in my designs. Thought I might actually be able to shoot them as a bonus too until they came with that little under sized aluminum fuse top that wouldn't thread on to a heavily de-milled main body. They neglected to tell me about the de-mil job. They were like $5 each too.

I don't have the luxury of having a machine shop like some of you guys so I will probably do some kind of zinc bore rider projectile with a drive band. You might consider this too after you work out the design bugs in steel and copper. Those things gotta take forever to make.

moose53 · « **Reply #173 on:** May 21, 2012, 03:18:59 PM »

After running the numbers for 1in 40 twist and 2lbs weight . I came up with 6.5 inchs long , 2.5 inch x 4.5 secant radius nose , 1.5inch x 4 deg rebated boat tail, and drilled out base to make 2 lbs. Will be interesting to see how well they shoot. They take about 3/4hr to turn out with the tracer setup .

Cannon Cocker · « **Reply #174 on:** May 21, 2012, 06:56:00 PM »

It really is looking a lot like the WWII originals. I would compare it to your first design which (regardless of the numbers) looked like the perfect example of all things good in a cannon projectile. This last one isn't as pretty, but if it shoots true that's what counts.

45 minutes to make isn't too bad. By the time I heat up a pot to pour lead or zinc, cut off the sprue, and sometimes swage them it's probably not much different...just inferior.

moose53 · « **Reply #175 on:** July 11, 2012, 07:04:42 PM »

Had the opportunity to shoot my cannon on the hill overlooking Oakridge this July 4 2012 . I had permission from the two closest neighbours on the hill and the Police Chief of Oakridge , very good spot to hear the shot roll down the valley. Sure was a lot of fun !

Frank46 · « **Reply #176 on:** July 12, 2012, 03:57:51 PM »

moose, thanks for sharing, that was cool. Frank

moose53 · « **Reply #177 on:** July 12, 2012, 06:08:55 PM »

A friend of mine lives just below and in line with the cannon , said that it shook his house as strong as a close thundercrack. When I get my bigger cannon going (3 inch ) i will have to shoot from farther away .

Frank46 · « **Reply #178 on:** July 13, 2012, 03:58:10 PM »

Moose, nice work. I happened to be in a local gun shop and they had some of that binary stuff that you shoot. I know the owner and said one shot and bet the sherriff will be out there in record time. Not that I'd do anything stupid. I found my little CVA cannon that shoots about 20 grs ffg and a patch round ball. That's about my limit at this time. Enjoyed your work. Frank

Cannoneer · « **Reply #179 on:** July 16, 2012, 04:48:03 PM »

Moose,

On a recent video you posted of a shoot, I mistook someone else's Whiworth for yours, now on this vid it looks like your gun is finished, paint and all; so how about posting some close-up shots?