Off Topic but still a cannon - 30mm GAU - load data advice?

[mwarnick1]

I found a 30mm GAU barrel at a reasonable price.  I'm going to build a single shot 30mm GAU cannon with a screw action once my federal paperwork clears.  The cannon will fire the 30mm GAU round.  Projectiles and cases are available for reloading.

Does anyone know where I can find load data for this round?  Sorry for the off topic post.  I can't find anywhere else on the internet to ask.  The places I have asked hasn't generated any info.

Thank you,

Matt
Chugiak, AK

[Cat Whisperer]

If you'd only asked a couple of years ago!  My neighbor (then) was an engineer who set up the production line for loading that ammo.  Moved back to Illinois or Indianna a couple of years ago.

[Double D]

Okay Matt,

You are out topic.  This is the Blackpowder mortar and cannon forum.  Now that you a severly chastized, tell us more?

Do you think that ATF will give you a license to build?

Do you have a back up plan if they don't?

Give us the details.

[mwarnick1]

After that horribly chastizing reply I'm afraid to post the details!  

Just kidding!

The feds will approve the build paperwork for civilians.  I'll file a form-1 (destructive device) to build it.  The local chief law enforcement officer (Anchorage Police Department) should sign off on the paperwork.  They've been signing off on machine guns and suppressors so they should sign off on this.

Here's some info on the round:

http://www.atk.com/defense/descriptions/products/medium-cal-ammo/gau-8.htm

A friend completed a build on one of these but hasn't been succesful on the carriage mount.  I haven't seen his cannon but he said that it used some type of falling block style action.  I'll see his cannon when I see him in 2 months.  That should help me get some ideas.  I had planned on using a simple screw style action.  That would reduce the need to worry about headspacing and would also simplify the build.

My friend fired his cannon twice.  The cannon was welded onto a carriage.  Each time it fired the cannon ripped itself off the mount and launched itself backwards.  I'm hoping to negate that with a recoil dampener.  Maybe hydraulic?

The barrel is $700, the fed tax is $200.  I'm not sure how much the action will cost me to build but I can control those costs by using a more simple or more complex action.  The carriage/recoil dampener will take some work.

Reloading projectiles and cases are available (but not overly common).  The only difficulty I'm having is finding a starting point for load data.

Thanks for allowing the off topic post.  If anyone has design ideas or starting points for reloading I'd love to hear them!

Matt

[Cat Whisperer]

From what my neighbor said about it was that it is a very high pressure round.  It's fired electrically.  It may take a while but I'll inquire as to what powder is used.  They don't run the production line often though.

[mwarnick1]

That would be a great help!  Thanks for the offer.  If you hear anything please let me know.

I plan on using a simple striker fire arrangement for this build.  The electrical primers would be removed.  I'll need a primer pocket adapter for each case to fire 50BMG primers.

Thanks,

Matt

matt_warnick@hotmail.com

[Double D]

Here's a link for you if you aren't already aware of it. http://www.bigskysurplus.com/

They have ammo, might beable to provide loading info.

[mwarnick1]

Thanks for the big sky link.  They have a good selection but their prices are a little high (heck - they want $2900 for the barrel I found for $700!).  These guys are pretty good: www.rvow.com (check out their 105mm projectiles - now that would be fun!!)

Here's the load data advice I've found so far:

"As for data, if I was using the slow burning powder that Hi-Tech is selling, I’d fill the case to the bottom of the shoulder and work my way up from there. This is a slow burning powder, and with that particular projectile I suspect that you cannot get enough in the case to cause excessive pressure. I use that powder in my 25mm Hotchkiss. A .7 pound projectile with .29 pounds of powder. Sounds and acts very similar to service rounds, but without all the high pressure."

Not exactly straight out of the reloading manual but it's more than I had yesterday! <grin>

Thank for the help and again for allowing off-topic posts.

Matt

[Double D]

Hey thanks for that link.  Now point me to some one who has 25mm projo's cheap, for my parrot rifle.

I have though about getting a 20mm bbl for building a Whitworth rifle.

How much rearward thrust does that 30mm have? Could you make a slide affair and dampen recoil with a couple truck shock absorbers?

[Blaster]

Big Sky Surplus does have a lot of neat stuff for sale,  however, I personally have a difficult time figuring out why they won't answer my
e-mails or return numerous phone calls for some prices etc.  I really wonder if they are still in business.  Anyone have any recent dealings with them??  Blaster (Bob in CO)

[Blaster]

Double D... I noted you mentioned a 20 m/m bbl for a Whitworth rifle.  I will soon have access to a  recently finished  little Naval Deck type gun.  It 's made with a 12-inch piece,  chamber end of a 20 m/m bbl and the carriage is fabricated from steel plate.  Whole thing weighs only around 60 lbs.  It has some pretty heavy duty trunions and has a huge screw on cap for the chamber end of the bbl.  It's fuze fired but has yet to be tried.  This will fire inert 20 m/m projectiles.  I believe for the first shot, I'd be behind a large tree and have a camcorder running to show just how it acts as far as possibly flipping over.  Will utilize about 600 grains of WC860 (.50 BMG) powder, which is very slow burning or can use blackpowder. The powder is merely inserted loose after seating the projectile.  I have been told that these things were fired at the Knob Creek M.G. shoot and were very impressive.  Since it is fuze fired, and can use either blackpowder or the WC860, it is not considered a destructive device.  Ever hear of one of these??  Thanks, Blaster

[Double D]

Is this the gun that Big Sky sells?

I would have to look at the breeching before I would use smokeless.

Won't be much fun any way unless you make a big stinky cloud of smoke!!!

If the breech is screwed on an off each time it iload and fired.  Make sure it has some method of pinning or  locking the breech on anmd the breech seals the chamber so no gases escape. If the gases ge loose it can be Cataclysmic!

I have talked to Big Sky within the past 30 days on the telephone.

[falconet]

The GAU case is huge.  Maybe making an adapter or rechambering to use the 30mm Apache case would be more reasonable.  Here's a website with some info: http://www.atk.com/productsPrecision/descriptions/products/medium-cal-ammo/lw30mm.htm
A local scrap yard had a dumpster full of the cases.  I picked up a few to play with.  If I could justify it I'd love to make 30mm cannon.  They also had a dumpster full of 40mm grenade launcher cases.

Cannonier

[Blaster]

Double D...yes, this is the same tube that Big Sky sells.  They sell it and the customer merely fabricates the carriage and that's it.  The very large screw-on nut has numerous threads and I'll have to see just how many turns it takes to have it seat home.  There is no provision for pinning the breech nut, but from what he (Bob at Big Sky) says, it works fine and won't unscrew when firing.  The threads are quite coarse and and I really doubt if it'd blow the nut off those threads.  If the nut would always return into the identical position each and every time, I suppose it could be pinned,  and just remove the pin each time it's fired.  Any interest in an e-mail picture of it and I'll send you one.  A very experienced gunsmith in Albuquerque recently looked at it and indicated that it appeared to be perfectly safe to fire.  If you talked to Big Sky Surplus within the past month, you are much luckier than I have been.  Almost makes me wonder if they don't want to talk to me after selling me this 20 m/m bbl, that they are afraid of a  potentional liability problem and don't want to associate themselves with me now. Hey, who knows???  Blaster

[Double D]

You can post the pictures your self or send them to me and i will post them for you.

Actually I think Bob at Big Sky has a real job and the Big Sky business is done on the side.

[Blaster]

DD:  Thanks for the offer to post the pix for me.  I'll e-mail them to you later on today (they are small pix so shouldn't take much time to download them).  I still havn't figured out how to post pictures on a forum, guess the old brain just has a difficult time trying to unravel the instructions that I have received so far.  And, yes, if Bob has a "real" job, this could explain the situation.  He had asked me to come up with some prices for him and although I keep trying to furnish those prices, I can't make the connection. Thanks again.  Later, Blaster (Bob)

[Gargoyle]

try:
http://www.obscure-reference.com/cgi-bin/atr.cgi

It's not that active & is for anti-tank rifles, but someone there should know something about the 30mm.