Humm... New project 20mm Blackpowder Rifle?

[Big Richard Hertzer]

I've Noticed 20mm barrels for sale with the chambers tourch cut,
Been thinking makeing  a Black powder 20mm rifle Anyone ever done this?
I'd have to have a Nasty Muzzle break just to be a smart ass!

[Cat Whisperer]

I'd sooner build a small cannon, but hey, big bore is big bore and has it's attractions.  Muzzel brake makes sense too.  Would you be putting a bayonet lug on it?  It would be big enough to support a genuinly goliath size blade.

I've known a couple of people that have had sections of 20mm bbls.  But either they didn't follow through or they just didn't talk about it much.

Keep us posted if you develop this further - I'm sure that there are a lot of pieces of barrel of large bore caliber out there just waiting for resurrection.

[Double D]

I fired a 20mm bolt action sniper rifle....once

[Jeff B.]

Hey Richard,

You mean a 20mm cannon that looks like this?:



I've been giving some serious thought to doing much the same thing except using a M2 .50 BMG barrel instead. The 20mm sounds real nice but the barrels are WAY over my budget and are absolutely impossible to find here in Canada. On the other hand, decent .50 BMG barrels go for about $60 US here, making it a logical choice for a home made project.

I figure I'd have to have a screw on breech block made to adapt to the existing threading on the barrel. Done properly I'm GUESSING that a .50 BMG chamber full of FG or FFG shouldn't give the screw on breech block much of a problem, should it?

Afterall, there's no way that amount of black powder could generate even close to the same energy or pressure that you'd commonly see in a .50 BMG round fired out of the same barrel. Please, correct me if I'm wrong.

[Cat Whisperer]

Jeff B.

  I can see that your neighbors look to you as the defender of the neighborhood.

  I would guess too, given CAST bullets, that your ASSUMPTION of a case full of slow black powder would be relatively safe (i.e.; lower pressure than with what it came with).  This appears to be common practice amoung the black powder cartridge rifle shooters.  (Check out for yourself the BPCR boards and draw you own conclusions.)  Jacketed bullets might be a little different, especially after that first round when the fouling starts to build up.

  I've found with the 4.5" mortar that it really helps to wipe out the bore after every round - otherwise it gets difficult to load after 3 or 4 shots (there's .050" clearance on the diameter).  Longer tubes might burn cleaner, but I'd look for experience, again, to the BCPR folks.

  Keep us posted, inquireing minds want to know.

[Jeff B.]

I can see that your neighbors look to you as the defender of the neighborhood.

That's a good one, I've never heard that one before!  :lol:

Cast bullets would definitely be my first choice. I'd put Lyman Moly lube on them too. I think a minie bullet might do the job but I'm not quite sure. It may even help reduce the amount of gas pressure involved since it takes time and distance for the undersize minie to expand into the rifling.

Lee makes a .50 cal minie that has a .500" diameter. BMG barrels are .510". I'm ASSUMING the minie will adequately expand to fill out the .01" difference. However, I'll check with the other BP boards here and ask for opinions first.

ASSUMING that it will work to begin with, the 1-15" twist is really agressive for this type of bullet. I'm wondering if expanding .01" will compromise the integrity of the minie to the point where excessive roational forces due to increased twist rate will cause the minie to fly apart. I'm sure the lead will have to be cast with a decent degree of hardness. I can see this project will definitely be a trial and error type of thing.

If the minie doesn't work out perhaps once of those fancy cast bullet mould made especially for the .50 BMG will work out.

Using slower buring powders like FG & FFG will probably help keep the pressures down in comparison to the much faster FFFG at the expense of increased fouling. Clean...clean...and more cleaning. Ahhh...the joys of black powder!

For the breech block I plan to use 4130 or 4140  bar stock steel with at least .500"-.750" steel above the threaded portion of the block.

I'm now motivated enough to at least buy the barrel this week. Yippee!  :-D

[Double D]

You will have to provide pictures of the building progress.  

Forget the Moly lube, use beeswax and crisco mix.  Moly lube  made a tarry mess for me in my 45/70.  

Also try Cannon grade powder.  If you go to our resources post and click on Powder Inc link you can order 5lbs instead 25 lbs.  Easier on the wallet that way.

[shooter575]

Guys,years ago Erma werk made a gallager carbine with surplus 12.7 mm MG barrels.twist was about the same 1:12-1:15 It will not shoot lead worth a hoot.Bullet will strip.Real hard lead works a bit better.and that is with 30-35 gr ff .You try to make a cannon with that fast of twist I bet you just get keyholes unless you use jacketed bullets.
My .02 worth
JW

[Jeff B.]

Sabots are another option that I plan to consider. Ultimately, I figure the jacketed projo's are something I might try but I'm still concerned about pressure issues with the removable breech block being the weakest link.

Whether it's a success or failure is something only time and experimentation will tell.

Hell, if it doesn't work it's not like I'm going to be out a whole lot of money.

[Double D]

Use acme threads and do a screw breech with interrupted threads.  

Or you could make a Williams gun type breech.  Saw one last night on American Shooter.  A single shoot rapid fire gun.

[Story]

Any updates to this project? I have a 20mm Vulcan barrel and a Wall Gun lock (in flint).

[GGaskill]

This thread started before I joined the forum so this is the first time I have seen it.  I have built a couple of muzzle loading "Parrott" style cannons using 2 foot pieces of rifled 30 mm barrel.  I also made a Minie ball mould for it.  As a Minie, the shot weighs about 10 oz; as a flat base, it weighs about a pound. I have shot it a number of times but not conducted a thorough accuracy test.

I have designed a sliding breech breech loader for another piece of 30 mm barrel but haven't built it yet.

[Double D]

This post goes way back to the early days of this board.  We were begging for posts back then and we allowed it then although now it is kinda off topic for this forum.  This was was posted before we really had our ground rules established and is "Grandfathered in"  and can remain.