This ones for Rickk

[rusty barrels]

Hi Rickk, I just got a Cohorn mortar for Hern and I've got a few questions for ya. First what is your base made of. How much powder do you use and what grade will it take to make a good report in blanks, do you wrap the charge or pour it in loose. This gun sure looks stout. I've already measured the barrel for the vent hole and it looks like if I drilled the hole straight down it will enter the chamber about .450 inches from the end. What do you think. I'll probably have more questions for ya later, hope you don't mind.

[Rickk]

My base is white oak, 31x15x9. I used Hern's hardware kit, which included the blueprints, and made it to the indicated size. I couldn't get two 7.5 inch thick pieces, so it is made of several other thicknesses glued, doweled, and then thru-bolted together.

Blanks... I use about 3.6 ounces of 1F "Skirmish Powder" (www.powderinc.com). in a plasic sandwich bag, which then goes into an aluminum foil bag. On top of the plastic bag, inside the aluminum foil bag, are two 1/8 inch thick cardboard wads that were soaked in baking soda/water solution and allowed to dry. THis makes the charge 1/4 inch longer, which is just enough to make it too long to roll as it goes down the barrel. I spraypaint a color dot on the side of the charge with the cardboard to indicate which end is up.

Im not sure about yours, but on mine if I drilled straight in it would have been even further from the base. I had it drilled on an EDM machine at a slight angle. The hole is .200 diamter and it enters the chamber at .400 from the bottom. The slight angle means that even if the charge was thinner than .400 it would get pierced someplace along the top of the bag. For shooting live charges you will be dealing with only 200-ish grains of Cannon grade for 100 yard shooting if you use a solid lead ball, so you want to be able to use a very light charge. If you use something other than solid lead it will weigh less and go even further. It is hard to get less than 160 grain charges to ignite consistantly in mine.

Feel free to ask more questions.

Rick

[rusty barrels]

DARN,I knew you where going to say that you use white oak,you would think with all the trees here in the northwest that it would not be a problem but it is, we got pine,fir,hemlock,cedar and even maple but red or white oak in thick sections is scarce to nonexsistent. I just did a rough measure to get an idea where and how much angle if any is needed to drill the vent with a machinist rule. The inside of the tube measures 9.82" from the muzzle to the end, the vent is 9.40" to the deepest part of the vent. From what you've said I probably shoot for .30" from the end. Is soaking the cardboard in baking soda a fire retardent? What is the difference in 1f goex and 1f skirmish besides price? Thanks again Rickk.

[Double D]

Some of that Pacific western maple will work just fine.  Won't be able to tell the difference under the OD paint any way.

[Rickk]

Like DD says, under the paint you can't tell. I got the oak for about a buck a board foot from the civil war re-enactor guy that owns the sawmill down the street... sorta a convinent arrangement.

The most important part is to make sure the wood is dry. Mine wasn't, and even though it was glued, and glue pegged, and bolted, the wood started to separate on the seams. This spring I will fill all the seams with auto body epoxy, sand down, and repaint.

I spent hours trying to measure and calculate the angle before I concluded that I was unsure about the outside shape and wound probably mess it up.

What they did at the machine shop with an EDM machine (this could be done with a drill press as well) was the following...

They got a piece of 2.25 OD steel rod and clamped it in the vise on the EDM machine. They adjusted it so that the machine was pointing at the end of the rod, .400 from the end. Then they slid the barrel over the rod and checked to see how close it was to lining up with the cast dimple in the outside of the barrel. After a couple of trial and errors they got it to line up with both the dimple and also the .400 mark on the end of the steel rod. Then they put the barrel back on aand started makin the .200 hole. It came out really clean that way, and there was no need to rely on math or measurement errors.

[Rickk]

Baking soda is a fire retartdent... same stuff they put in dry chemical fire extinguishers.

The difference between Goex and "Skirmish" 1F powders, and far as I can tell, is mostly the $3 a can difference in price.

In blanks you will be using a lot of it. I'm sure there is a pressure difference bewteen different brands... I keep the blank loads to 3.6 ounces... I'm pretty sure that is very safe.

[Double D]

The most important part is to make sure the wood is dry. Mine wasn't, and even though it was glued, and glue pegged, and bolted, the wood started to separate on the seams. This spring I will fill all the seams with auto body epoxy, sand down, and repaint.

This is very authentic...you go to the museums and see the originals and they all are separating at the seams and all have filler.  Clever touch there Rick!