Author Topic: Vent Liner? (Read 2327 times)

GAWI · « **on:** January 26, 2007, 06:04:35 PM »

I have drilled a vent hole, an i to understand that i need some kind of liner? Was going to shoot this weekend but maybe not. And do i have powder charge correct? 2 1/4 bore= 4 1/2 oz? Let me know. Thanks

Double D · « **Reply #1 on:** January 26, 2007, 06:21:48 PM »

GAWI,

If your barrel has a liner , yes you do need a vent tube. The vent tube keeps debris and corrosion from starting betweeen the liner and the outer barrel in the vent hole.

2 1/4 bore = 4 1/2 oz MAXIMUM charge. Follow Sitliks advice for first loads start ridiculously lower and then work up until you find a combination that gives you good accuracy and doesn't tear your carriage up.

That's some thing we haven't talked about a great deal. you can build a tube to all the recommended safety specs and load to the recommended maximum charge, but if your carriage isn't built to an equal strength it will break. Not much fun to go to all that trouble to set your gun up and fire of a max charge only to have it break...been there done that!

So vent liner if you are shooting a lined barrel and a ridiculously lower charge than maximum charge to start.

Artilleryman · « **Reply #2 on:** January 26, 2007, 06:24:56 PM »

You need a vent liner if you have a barrel with a sleeve. The vent liner then would give you a continous passageway from the bore to the outside of the barrel. Otherwise you miight have a gap between the barrel and the sleeve that could hold a spark.

If you are shooting N-SSA rules the maximum charge for a smoothbore would be 4 1/2 oz of 1fg and a 22.5 oz projectile.

DD beat me to the punch.

GAWI · « **Reply #3 on:** January 26, 2007, 06:40:41 PM »

I have cannon powder. I guess thats one below Fg. Do you use same charge for blank shots? What should the liner be made of? What should the diameter of vent hole be? Gary

GAWI · « **Reply #4 on:** January 26, 2007, 06:43:54 PM »

Forgot one thing this by wt correct?

GAWI · « **Reply #5 on:** January 26, 2007, 06:45:37 PM »

Another thing can you purchase these vent liners? Gary

GGaskill · « **Reply #6 on:** January 26, 2007, 07:42:13 PM »

Yes, the ounces are weight measure, not liquid (volume) measure.

The vent needs to be tapped and a screw drilled all the way through is then placed in the hole and threaded all the way in. There is a post on the forum that explains the procedure.

Cannon grade powder is the next coarser grade from Fg.

Double D · « **Reply #7 on:** January 26, 2007, 08:31:24 PM »

Quote from: Artilleryman on January 26, 2007, 06:24:56 PM

DD beat me to the punch.

Ah yes, Great minds think alike...that's minds not mines...although some times mine is just like a great dark hole in the ground...

Rickk · « **Reply #8 on:** January 27, 2007, 12:46:12 AM »

GAWI, what are you shooing, a cannon or mortar?

The reason that I ask is that if you shoot 4+ ounces in a mortar you need a heck of a lota "downrange".

I'm personally using about 3.6 ounces of 1F for blanks in my 2.25 inch mortar.

For ball (lead, about 34 ounces) I am using under 200 grains (about 170 actually) of cannon grade for 100 yard shooting.

I know 34 ounce projectiles are more than 22 ounces that the NSSA recommends, but I believe their loading table would let me use 4.5 ounces of possibly 1F (they don't really say) behind a 22 ounce ball. My charges are around 10% or less of the max recommended amount, and they are of cannon grade as well. I'm not loosing any sleep over it.

FYI, I tried an 18 ounce projectile once, and with the same 170 grain load (about the smallest that can be reliably loaded and ignited in my gun) it went well over 200 yards I think... not sure... never found it... just going by the amount of time my years told me it wa in fllgiht and pluging that into a spreadsheet I wrote.

If it was a cannon instead of a mortar I would up the charge quite a bit with projectiles. Still. I doubt I would have a need to go anywhere near the max recomended amount. I am thinking more like under 1-2 ounces of Cannon would be alot for 100-200 yard shooting.

4.5 ounces is a lot of powder behind a projectile.... not maybe from a pressure point of view, but from a muzzle energy point of view.

CU_Cannon · « **Reply #9 on:** January 27, 2007, 03:42:11 AM »

The original vent liners were made of copper. I’ve machined copper a couple of times. It is no fun. I would use stainless steel or even mild steel. Has anyone out there actually made one of copper before?

I’m planning on adding a liner on my 12 pdr coehorn at some point. The barrel was machined from solid but I want the flexibility of using percussion caps, fuse or friction primers. For each I can just unscrew the vent and screw in the new one.

Someone at the last reenactment I attended suggested a flare at the bottom of the vent. The idea is that it would act like a nozzle helping with ignition.

Rickk · « **Reply #10 on:** January 27, 2007, 04:37:42 AM »

I wonder if Brass is just as suitable as Copper for a vent liner. Brass threaded rod is readily available from several marine suppliers on internet.

Stainless has also been suggested. The only issue I would have with stainless is getting it out if it doesn't want to come out and needs to come out. You are supposed to grind off the square portion after assembly, so there isn't anything left to grab onto to unscrew it.

If it had to come out, a brass liner could probably be taken out with an e-z-out or, worst case, drilled out with little effort. Stainless would be a bit more work and there would be a bigger chance of messing up the barrel in the process if drilling out was needed.

Also, when you thread the barrel, do you not fully cut the threads thru (leave it tight near the bottom)? What allows you to tighten the liner so that it stays in place and doesn't move in our out? Locktite? I would hate to have to remove a stainless liner locktited in place that had been ground down flat.

I'm sure some of you vent liner users know the answers to these questions... to me they are a mystery.

Rick

Double D · « **Reply #11 on:** January 27, 2007, 05:51:13 AM »

Quote from: CU_Cannon on January 27, 2007, 03:42:11 AM

I’m planning on adding a liner on my 12 pdr coehorn at some point. The barrel was machined from solid....

You mean vent liner in the above don't you?

GAWI · « **Reply #12 on:** January 27, 2007, 07:08:03 AM »

Hey people, what i have is 1/2 scale napoleon cannon from hern. The carriage is nade out of steel with steel wheels. Have already picked up wood to make correct carriage but am slow in winter. Guess i will be working on the vent for awhile. Thanks for info. Gary

Max Caliber · « **Reply #13 on:** January 27, 2007, 07:28:57 AM »

The vent liner or vent piece, was, by the Civil War, made of wrought copper. It was beveled at the end and had a slight shoulder at the top and was square above the shoulder to allow it to be turned into the barrel. When properly seated, the beveled end would come to rest in its seat just before entering the bore and the shoulder would seat on the flat on top of the barrel.The square shank would be cut off and the vent piece would be dressed to the contour of the barrel. The reason for the beveled end was so the whole end surface of the vent piece would not be exposed to the pressure of the gasses. The idea being that only the vent hole be exposed, lessening the possibility of the vent piece being blown out.

Max

Rickk · « **Reply #14 on:** January 27, 2007, 11:27:57 AM »

Does anyone know if anyone making off the shelf vent liners in copper or brass or bronze?

Sounds like a market that needs filling.

CU_Cannon · « **Reply #15 on:** January 28, 2007, 04:40:35 PM »

Quote

You mean vent liner in the above don't you?

Yes, vent liner. I have a tendency to type what I am thinking.

The problem with copper is that it work hardens very fast making it very hard to machine. It makes sense that it would have been wrought. That would be easier than trying to machine it.

If you use high temp grease on the vent liner it shouldn’t be a problem to remove. For the most part the only reason to remove the vent piece was to replace it. If the old one was destroyed in the process it wasn’t a big deal. If you plan on removing it frequently leaving a head of some sort would be the best. (note this is from what I’ve seen others do and not from personal experience)

rusty barrels · « **Reply #16 on:** January 29, 2007, 09:00:23 AM »

Crap, just when I thought my gun was ready to fire, just waiting for the powder........it's not. So how big do I need to drill and tap a vent for a 2 1/4 bore gun, or did someone already asked that question.

Max Caliber · « **Reply #17 on:** January 29, 2007, 11:00:30 AM »

Rusty,
For a bore your size you could go with 1/2 inch diameter if you are using small fuze. 5/8x18 is about right if you use .22 blanks and probably would be better all around. Wait and see what others have to say on the subject. The vent piece is a very important part and needs to be installed with care. Something not mentioned before is that the vent piece CAN act as a safety valve like the safety plugs that were originally installed on high quality muzzle loading shotgun barrels. Better to blow out a vent piece than blow up a barrel.

Max

rusty barrels · « **Reply #18 on:** January 29, 2007, 02:49:55 PM »

I'll wait , I've got a 1/2X6" round piece of copper to start with if thats recomended?

Terry C. · « **Reply #19 on:** January 30, 2007, 06:28:46 AM »

Re: Brass or bronze vent liners.

From what I've read, copper is used because it withstands the hot jet of flame that is forced out of the vent during firing much better than bronze. That's why copper vent liners were used in bronze guns.

The hot gas leaches the tin from the alloy, causing the vent to erode rapidly. Brass might be less affected, since the zinc has a higher melting point.

If so, then brass vent liners would probably be okay for the hobbiest (especially those that don't fire their guns that much), and could be changed if/when the hole enlarges excessively.

But if I were going for longevity (or authenticity) neither would be my first choice.

Artilleryman · « **Reply #20 on:** January 30, 2007, 07:03:50 AM »

I have a stainless steel vent piece that I have been using for over 20 some years in my 10pdr Parrott. I have shot at least 50 rounds and sometimes 100 rounds per year, twenty or more of which are service rounds. This gun gets inspected on a regular basis with a fibre optic device that allows you to look right at the base of the vent piece. There is a minor amount of erosion so far in that area. I don't anticipate having to replace it anytime soon.

Santa Dave · « **Reply #21 on:** January 31, 2007, 12:20:44 PM »

Down in San Diego at the embarcadero are two napoleans who saw service in the civil war. They then stood guard over San Diego Bay and were fired at morning colors every day.
At some point they aquired a coating of bronze (badly worn) and each has a shining vent liner of stainless steel!

Dave

Artilleryman · « **Reply #22 on:** January 31, 2007, 12:25:59 PM »

Napoleons should be bronze to begin with.

GGaskill · « **Reply #23 on:** January 31, 2007, 01:20:41 PM »

Looks like they acquired either a coat of clear lacquer or bronze paint which has worn off due to handling to present the bare bronze to corrosion from many hands.

Articifer Tom · « **Reply #24 on:** January 31, 2007, 02:14:31 PM »

Get a s/s bolt 3/4 " have hole .200 or less drilled and reamed through it. Have bottom end 1/4 " machined down to 3/8" and 60 degrees tapered back to threads . Drill 3/8 " hole into chamber then drill proper size hole for 3/4" tap to within 3/16" of chamber and bottom tap it. Take and cut the neck out of a rifle casing like .338 win to make a gas check , side over vent wrench in; bring out to check seal . Finish by installing with lock-tight , cut head flush , and grind inside to match radius , flush.
This seams like lots of work .But gives you that thur liner with seal between liner and outterr metal ie.cast ,brass , bronze ect. My liners in 17 years old has shot competative and 12years of blanks re-enact'g ,hundreds of rounds and no noticible wear, or rust .

Cannonmaker · « **Reply #25 on:** January 31, 2007, 08:17:53 PM »

Dave, Are those Napoleons the ones on the bow of the Burkley, the farry boat at the maritime musium in San Diego. I haven't seen them for a couple of years, I do belive they had a a coat of lacquer on them.
The soldiers must have polished their pieces well, the markings are well worn.

Rick

Santa Dave · « **Reply #26 on:** February 02, 2007, 11:23:28 AM »

Rickk-
Sure thing!
And what I MENT to say was a BRASS plating!
And if you look the brass is gone wherever "Seagull" got on the brass

I THINK the carraiges are not original.
I have some more pics if anyone is interested. (WITH Goex can!)
Dave