4 1/2" hyd cylinder mortar

[silicon wolverine]

Been working on this one a while and wanted your guys take on it.  have a 4.5" bore 40" long hyd cyclinder i had a machine shop hot weld the base onto for me.  THey also welded on truss rods to the base and they are torqued to 200 lb/ft.  six oz of Fg fits in the base cup perfectly.  this will be fuse ignited.  projectiles will be wood turned into shape that weigh about a pound or so.  the lady at the lumberyard told me the wood i bought was pressure treated birch, it was the hardest thing they had in a 6x6 for me to turn down.


the current baseplate and legs will be replaced in teh future by a T&E mechanism and a solid baseplate made from 24" agricultural disk blades.  i built them for testing so if it goes kaboom im not out much.


the comparison rounds are 38 spl and 45-70.


whats your thoughts?  too much powder?  projo will just fly apart?  light the fuse and run like the dickens? 

[bilmac]

No rifling so don't you need some fins on your bullets to keep them from tumbling?

[silicon wolverine]

i think ill hollow out the tail and use some drag streamers like some of the WWII japanese mortars did.


SW

[little seacoast]

I can not speak to the question of materials, design, or safety. I can tell you 6oz of any BP is going to be way too much of a good thing. Try a much more modest load, say 1oz, and work up from there. One of this Board's pet issues is safety, and rightly so. Work up to a powder load that works best for you. I would have to suggest also that you consider some metal banding on your turned projectiles to prevent their being fragmented since they are turned long grain and birch is a little brittle to begin with. Strapping bands from Lowe's or HD are free and about the right width and thickness. Good luck and be safe.

[dominick]

I think 4" PVC is close to 4-1/2" in diameter.  That stuff makes good re-usable projectiles and can be filled with cement.  Also, the  4.6" Coehorn mortars I built in the past use about 600 grains of powder for a practical load.  These have heavy barrels with powder chambers.

[silicon wolverine]

a clairification, im using pyrodex RS not real BP as im unable to locate any withing reasonable distance of me. ive used it with good effect in my smallbore guns and its easy for me to get around here.



ive thoughbt about banding.  are you talking about the stuff with holes all the way along it and then screwed on?


also i called the lady at teh lumberyard and double checked, it is pine not birch as she told me in the first place. 


given your advice ill start at 2oz and move upward.


THANKS A TON GUYS!


SW

[GGaskill]

Is your tube straight the whole way down or does it have a reduced diameter chamber at the bottom?  What is the wall thickness of the tube?

[little seacoast]

The banding I referred to is the half inch wide stuff they band bundles of lumber with, thin and very flexible. Some are changing over to nylon strapping. I rather thought your projectile looked like southern pine pressure treated but it's hard to tell from a picture, when fully seasoned it is quite hard but will still splinter.
FWIW Pyrodex has been a real disappointment in mortars for me, you need a really tight projectile fit in order to build enough pressure. 

[Double D]

S/W,

Tell us more about the construction of the tube.  Does it have a chamber?  What is the wall thickness over the chamber.
 

[silicon wolverine]

wall thickness is about 1/2" steel in the tube.  the base is 3/4"-7/8" inch thick cast with a 3" half round powder chamber in the bottom.  the original application was a header lift cylinder in a combine that was carrying around 12000 lbs of weight.  working pressure was 5000 psi with surge loads to 15,000 psi.

ive been using thick cardboard as a "gas check" to get pyrodex to work properly while still keeping a good windage gap on the projectile.

SW

[Double D]

After getting another inquiry off line about this style of mortar.  I did a little research on previous discussions on the Stokes mortar to see where we decide to go with this.

Please review this post:

http://www.gboreloaded.com/forums/blackpowder-mortar-and-cannon-sponsored-by-seacoast-artillery/stokes-mortars/


 

[little seacoast]

Unless I'm missing something the letter would seem to cover the design and ammo that he is proposing to make. Where is the hitch?

[Double D]

Unless I'm missing something the letter would seem to cover the design and ammo that he is proposing to make. Where is the hitch?

The letter is for my mortar not his.

He needs to get a letter for his mortar in order to post here.  That is the rule for the board.  The Stokes mortars are not really in keeping with the spirit of the board anyway.  But if ATF says the ignition is antique then it is allowed for that reason only.

[silicon wolverine]

OK if im reading this correctly, im not allowed to talk about this mortar unless i have an ATF letter specifically approving it?  Or am i reading that the wrong way?  If such discussion is verboten, sorry, didnt know it was.


Also our ATF agent stopped by the gunshop to visit with us about an unrelated topic and i asked him the regs on this type of cannon and he said as long as it was not fixed ammunition, was muzzle loading and used a "primitive" igntion system, his understanding was it is acceptable and not a DD.  He specifically asked about ammunition type, and i told him loose powder and projectile with fuse ignition. 


All of my guns follow this design to avoid the DD designation.  they are all the same design, just constructed in different ways. 


Also ive seen several threads on here discussing beer can mortars/cannons.  they didnt replicate any historic deisgn, but discussion was allowed.  Can someone explain the difference please?


This follows coehorn design (base pin mount style), do i need to take the legs off and make the base out of wood instead of steel to meet the rules?


If this tube is unnaceptable as a mortar, i can build a carrage and make a howitzer out of it.  If that is acceptable, why isnt this thread, being as nothing in the gun has changed except what its attached to?


i found several threads discussing using hyd cylinders as barrels for both mortars and cannons and no mention of the above rules was made.  Wha?

Im not trying to be a jerk, but Ya'll got me mighty confused, and given the other threads ive found here discussing similar topics, feeling a bit picked on.   


SW

[Cannon Cocker]

You are correct, and your ATF agent is correct.  No fixed ammunition, antique ignition, and muzzle loading place it solidly in antique category and completely legal.  NO letter is needed from the ATF for you to own or fire this mortar.  The rules of this board may vary. 

[Double D]

OK if im reading this correctly, im not allowed to talk about this mortar unless i have an ATF letter specifically approving it?  Or am i reading that the wrong way?  If such discussion is verboten, sorry, didnt know it was.

Not verboten, restricted a bit

But not a problem we don't see these here that often.  We originally had them banned as we weren't sure of the legality of these Stokes mortars.  We were especially concerned when we saw a couple of news stories about these being seized during drug raids.  A couple of years ago, we went through the periodic  series of post about yes they are-no  they aren't legal.  I did some research to find those news report on two such cases i was aware off.  It took me a couple days and I found both.  The stories were old enough that the case had been to court.  Both cases charge dismissed.  That is when I wrote the letter to ATF.

Also our ATF agent stopped by the gunshop to visit with us about an unrelated topic and i asked him the regs on this type of cannon and he said as long as it was not fixed ammunition, was muzzle loading and used a "primitive" igntion system, his understanding was it is acceptable and not a DD.  He specifically asked about ammunition type, and i told him loose powder and projectile with fuse ignition. 

A piece of advice from this 35 year+ retired Law enforcement Officer.  Never rely on legal advice verbally given to by a Law enforcement officer in the field.  Although is Sounds like this ATF Agent got right.  Down the road if you have to call the Officer as a defense witness he will remember your question and his response differently.

That is why I wrote the letter about the mortar.

All of my guns follow this design to avoid the DD designation.  they are all the same design, just constructed in different ways. 


Also ive seen several threads on here discussing beer can mortars/cannons.  they didnt replicate any historic deisgn, but discussion was allowed.  Can someone explain the difference please?

All of then some what replicate but not necessarily duplicate some pre 1898 cannon.  My popcan and golf ball mortra replicate the confederate pattern Coehorn.

This follows coehorn design (base pin mount style), do i need to take the legs off and make the base out of wood instead of steel to meet the rules?


If this tube is unnaceptable as a mortar, i can build a carrage and make a howitzer out of it.  If that is acceptable, why isnt this thread, being as nothing in the gun has changed except what its attached to?


i found several threads discussing using hyd cylinders as barrels for both mortars and cannons and no mention of the above rules was made.  Wha?

Im not trying to be a jerk, but Ya'll got me mighty confused, and given the other threads ive found here discussing similar topics, feeling a bit picked on.   


SW
[/quote]

[Double D]

OK if im reading this correctly, im not allowed to talk about this mortar unless i have an ATF letter specifically approving it?  Or am i reading that the wrong way?  If such discussion is verboten, sorry, didnt know it was.

Not verboten, restricted a bit

But not a problem we don't see these here that often.  We originally had them banned as we weren't sure of the legality of these Stokes mortars.  We were especially concerned when we saw a couple of news stories about these being seized during drug raids.  A couple of years ago, we went through the periodic  series of post about yes they are-no  they aren't legal.  I did some research to find those news report on two such cases I was aware off.  It took me a couple days and I found both.  The stories were old enough that the case had been to court.  Both cases charge dismissed related to the mortar.  That is when I wrote the letter to ATF.

Also our ATF agent stopped by the gunshop to visit with us about an unrelated topic and i asked him the regs on this type of cannon and he said as long as it was not fixed ammunition, was muzzle loading and used a "primitive" igntion system, his understanding was it is acceptable and not a DD.  He specifically asked about ammunition type, and i told him loose powder and projectile with fuse ignition. 

A piece of advice from this 35 year+ retired Law enforcement Officer.  Never rely on legal advice verbally given to by a Law enforcement officer in the field.  Although is Sounds like this ATF Agent got right, that isn't always the case.  Down the road if you have to call the Officer as a defense witness he will remember your question and his response differently.

That is why I wrote the letter to ATF about the mortar.  That is why we want the letter posted here first---can you say C-Y-A!  That letter is also your best evidence if you are challenged by law enforcement.  THe court will look upon in a better light if you have. 

All of my guns follow this design to avoid the DD designation.  they are all the same design, just constructed in different ways. 

Also ive seen several threads on here discussing beer can mortars/cannons.  they didnt replicate any historic deisgn, but discussion was allowed.  Can someone explain the difference please?

All of the one I have seen here some what replicate but not necessarily duplicate some pre 1898 cannon or mortar.  My pop can and golf ball mortar replicate the confederate pattern Coehorn.  Straight tube, no reinforcing bands

This follows coehorn design (base pin mount style), do i need to take the legs off and make the base out of wood instead of steel to meet the rules?

Sorry, but your cannon is no Coehorn, not even close.  It is a Stokes mortar, plain and simple originally designed in 1914.

If this tube is unnaceptable as a mortar, i can build a carrage and make a howitzer out of it.  If that is acceptable, why isnt this thread, being as nothing in the gun has changed except what its attached to?

i found several threads discussing using hyd cylinders as barrels for both mortars and cannons and no mention of the above rules was made.  Wha?

Im not trying to be a jerk, but Ya'll got me mighty confused, and given the other threads ive found here discussing similar topics, feeling a bit picked on.   

First you are not being picked on at all.  We are trying to help you learn how build a safe cannon. If we can help  you make your cannon safe so you enjoy it and don''t have an accident, that is good for you and good for us.  Every cannon accident reflects badly on all of use as a group.  If some one posts and unsafe cannon here and we say nothing, do we have a culpability...I don't think so. But I would feel kind of bad that I hadn't said anything if ther was an accident. 

So if we ask questions about your cannon it isn't to pick on you,  but to help you and to make you safe.   It also stand as a forewarning to others who may be. 

We have had a number of  discussions over the years about hydraulic cylinders as well as different type of steels to use for cannons.  One thing we  discovered early on there didn't seem to be any real guidelines on cannon construction.   Then we found the safety guidelines of the  American Artillery Association and the North-South Skirmish Association.  We have links posted at the top of this  board to both of ther websites.  Take   a look at the Safe loads and  Construction sticky.

Those standards are minimum standards. 

We haven't had much discussion on hydraulic cylinder lately, but over the years we have discussed them.  The bottom line is what type of steel are they made from and how are they made.  Some where in the past we answered those question.

I was  one of the originating moderators of this board...I (with CW) made the rules for it.  But CW and  I have passed the moderator duties to  Artilleryman and  GGaskill.   It is up to them if to let this post ride or lock it down.     

Since we have already started discussion, I suggest keep it opened.

 We have already started the first step of the discussion to get you send in for  a letter.

I am not a big fan of this particular style mortar, but there are others who are.  If I and the other folks here can help you make sure your mortar is safe, then others who are thinking about building one of these will read and be aware. 

So talk away.
 

[silicon wolverine]

OK. so were working in grey area, i can understand that. 

Now on to more details.  the cylinder i have was specifically chosen because of its size and design.  it was origianlly intended to carry loads of thousands of surge PSI with only o rings and bolts holding it together.  Mine has been welded by a professional shop plus the addition of truss rods make it at least twice as strong as the original design.  Given your sugggestion of 1-2oz of powder i feel this is well within safety standards.  nontheless test firing will take pace remotely.

also i would like some clarification on the stokes mortar.  as i understand it, the stokes used a fixed firing pin in the base and fixed ammunition.  is mine a stokes simply because of how it looks even though function and construction is only remotely connected?

SW

[Cannon Cocker]

Given your sugggestion of 1-2oz of powder i feel this is well within safety standards.  nontheless test firing will take pace remotely.

also i would like some clarification on the stokes mortar.  as i understand it, the stokes used a fixed firing pin in the base and fixed ammunition.  is mine a stokes simply because of how it looks even though function and construction is only remotely connected?

I would suggest using even less than 1-2 oz.  Not because of safety, but because of waste.  I think you may get a couple hundred yards or more from a half ounce if you don't have a lot of windage.  And with a projo that light, you don't need a lot of windage.  Increasing the charge is just going to give you a bigger foomp anyway, and the projo will be long gone.  Just the nature of a bore that big with a projo that light. 


Yes, yours is functionally nothing like a Stokes mortar, and looks more like a Stokes than a Parrot rifle. 

[Double D]

also i would like some clarification on the stokes mortar.  as i understand it, the stokes used a fixed firing pin in the base and fixed ammunition.  is mine a stokes simply because of how it looks even though function and construction is only remotely connected?

SW

If it walks like a duck and looks like a duck...

You mortar looks like a stokes, it replicates a Stokes, so it must be duck.

Stokes


Coehorn Mortar


I think this  coehorn  belongs to  George

[Double D]

Now on to more details.  the cylinder i have was specifically chosen because of its size and design.  it was origianlly intended to carry loads of thousands of surge PSI with only o rings and bolts holding it together.  Mine has been welded by a professional shop plus the addition of truss rods make it at least twice as strong as the original design.  Given your sugggestion of 1-2oz of powder i feel this is well within safety standards.  nontheless test firing will take pace remotely.
 

SW

Does your  hydraulic cylinder meet these minimum standards?

http://www.americanartillery.org/aaa/marty.html
General Information

The following safe shooting procedure presumes the crew is firing projectiles with a muzzleloading artillery piece made (or altered) to modern safety standards. (If firing blanks skip Step VII and see Safety Rule 9.) The bore should be lined with seamless steel tubing with a minimum 3/8-inch wall thickness and a yield strength of 85,000 psi or greater. The breechplug should be threaded and pinned; welded and pinned breechplugs can be equally strong but require expert installation by competent manufacturers. Sand cored bores are not recommended for shooting. The vent should be drilled in a threaded copper bolt similar to original cannon vent liners of the 1840-1865 period) in order to provide an unbroken passage through the casting and the liner, into the bore.

[GGaskill]

But CW and  I have passed the moderator duties to  Artilleryman and  GGaskill.   It is up to them to let this post ride or lock it down.     

Since we have already started discussion, I suggest keeping it opened.

It is instructive to examine the ATF's reply to the inquiry.  Although "Stokes Mortar" and "1914" are mentioned in the first paragraph, they are not mentioned again. 

Additionally, the fifth paragraph says, "Muzzle loading cannons not capable of firing fixed ammunition that were manufactured in or before 1898, and replicas thereof, are antiques and not subject to the provisions of either the Gun Control Act 0f 1968 or the NFA."

The summary paragraph (number seven) states, "It appears that the described muzzle loading mortars use an antique form of ignition system and meet the definition of an antique firearm.  Based on the cited statu[t]es, as well as the intended construction and use of these mortars, FTB has determined they would be precluded from classification as 'firearms' or 'destructive devices.'  However, if they use other projectiles, this determination would be subject to review."

It is my opinion (which would carry no weight in court or with the ATF) that the mortar of the OP is conceptually the same as the one proposed to the ATF and should get the same response should an inquiry be made to them.  The essential points are (1) not capable of firing fixed ammunition, (2) antique form of ignition system, and (3) intended construction and use.  Although 1898 is mentioned, 1914 is also mentioned and not presented as an issue.

It is also my opinion that if you asked the ATF for an opinion on your particular mortar, you would get a reply that varied little from the reply received by DD.  But then you would have an official statement that YOU are within the law which would be a stronger defense should things come to that.  Our policy has been to suggest that anyone contemplating a project which approaches the boundaries of the law should make formal inquiry of the ATF with a full description of the project before commencing with the project.  I think that remains a wise recommendation.

In the mean time, as long as "Stokes mortars" use antique ignition systems and are not intended for use as weapons, their discussion will remain a permitted subject.

[little seacoast]

Thanks for the clarification, always good to know for sure.

[silicon wolverine]

Thanks here too.  Now back to the subject at hand.


The tube material isnt stainless steel, it is modern high stregnth steel and exceedes the thickness requirements put forth in the safety rules. 


teh breech is not pinned and welded, but it is welded with high strength truss rods.  also the breechplug inserts inside the tube 3/4" and has a shoulder the tube rides on, further stregthening it.  i felt drilling it for pins would weaken it more than i gained.


given the light weight if the projectiles, i think i have a workable safety margin.


also earlier mentioned was the fact a larger powder charge wouldnt gain the projo anymore range, just make noise and smoke.  can someone explain that as my cannons have always gained speed when i increased teh charge. 


SW

[Indygunworks]

Can you elaborate a little bit more on how the breech plug is inserted 3/4 of an inch?

[Cannon Cocker]

also earlier mentioned was the fact a larger powder charge wouldnt gain the projo anymore range, just make noise and smoke.  can someone explain that as my cannons have always gained speed when i increased teh charge. 

I think you might be referring to my comments on additional powder.  The projectile will definitely go further with more powder.  What I meant was that you may find you need less powder than expected to get extreme ranges. 

[Ex 49'er]

also earlier mentioned was the fact a larger powder charge wouldnt gain the projo anymore range, just make noise and smoke.  can someone explain that as my cannons have always gained speed when i increased teh charge.

What I meant was that if you find you need less powder than expected to get extreme ranges.

That would depend on how much windage there is. Tighter windage = more distance

[silicon wolverine]

Can you elaborate a little bit more on how the breech plug is inserted 3/4 of an inch?

heres a pic of the breech design.


SW

[Double D]

If this cylinder has a 4.5 inch bore, then to meet minimum safety guidelines, it needs walls over the the breech that are also 4.5 inches thick for a total breech diameter of 13.5 inches.

This thickness of the  breech plug need to be 4.5 inches also.

The real question how is this Breech insert before welding?  Pressed?  Shrinkfit?  Or slipfit?  Slip fit will allow a place for  powder fouling to migrate and starting corrosion and  weaken the seam....

[Indygunworks]

I am have the same questions here as DD, but i thought the wall thickness was one caliber of the chamber, not the bore?  If it has a reduced size chamber could it not have a reduced size bore as well?