doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com British 16 ga black powder proof.

What would be the proof and service pressures for a 16 gauge black powder proofed double gun in 1860 to 1870? The gun has decent barrels but don't know what type of loads I'm looking at using. Not going to load black but I can load nitro powders to fairly low pressures. Other option is to have Briley fit a set of 28 tubes in it but I hate making any double swing like concrete on a post.

This is a conversion and I think it started out as a muzzle loader, then converted to pin fire and now center fire. Good barrels must have been prized or it was owned by one frugal owner. Needs a fair amount of work but well worth saving.

No pressures listed, but for the 16 under the rules of 1855 and also 1868, the proof load was 13 1/2 drams of black powder. Don't know how much that helps you.

Why not load BP?
Its been working fine for at least the last 3 1\2 centuries as a means to propel a load of shot down a smooth tube.
Not being critical, just wondering.

Don't know the service pressures but would assume they were pretty low The chamber walls will be thin due to the conversion to breech loading. Of course you knew that;)

I have loaded black but just rather not anymore. If I can I will find a safe nitro substitute, using powders on hand. I have about 20 different ones and should be able to find something. I was looking for a range of pressures that I should be working towards. I figure anything in the 5,500-6,500 should be fine. Due to the age I don't see the need for anything more than that.

The gun wont care if it is black or nitro. After all the gun does not know which is which. About five years ago I was using black powder in a dove field. Every time I shot you could hear people talking about it. I laughed about it being called an explosive, or that I could start a fire in the field. Sometime I think recoil has lowered a few peoples IQ.

I use BP loads on opening day of dove season on purpose!
People here seem to get a bit closer than I care for. After the first shot I seem to be given a lot more space!
I believe it scares them.

It is of course totally true the gun reacts to pressure, doesn't matter if from black or Smokeless. There is however a major difference in Black & Smokeless. A very simple little trial will show this difference dramatically. Scoop out about a teaspoon ful of each onto a dry hard non-flammable surface & light it with a "Long" match. The Black will go up with a "Whoosh", the smokeless will be hard to ignite at all & then just mostly smolder.
What does this prove, Black will burn at substantially the same rates regardless of other conditions. Smokeless on the other hand requires a certain amount of pressure for reliable burning. Many of these "Low Pressure" loads are skirting the ragged edges of their practicality.
To get loads which do not exceed that 6500 psi It is likely you will have to go with a lighter shot charge than the 1 oz which is more or less normal for the gauge. This may be acceptable for your purpose. On the + side with its smaller combustion chamber than a 12 the 16 "May" burn the powder a bit more efficiently at lower pressures as you will be using the same strength primer to ignite a smaller charge.
My "Own Personal Belief" as far as any of my guns go is "If" it does not seem capable of handling 8K psi it is either relegated for Black only or the wall.

Back to the original question. What was the normal 16 ga. black powder load for a British double in the era of 1860 to 1870? If the British 12 2 1/2" is one ounce was the 16 load less? 7/8 ounce or one ounce as well? Service pressure 7K, 8K or what?

The old British proof tables don't give a shot charge for whatever the standard 16ga load was. The only projectile weight I find is 399 grains, and that's for the proof load, not service load.

According to a table from Burrard the old standard British load for the 2�" 12 was 1 1/8oz, which was reduced by Law I believe during WWI to 1 1/16oz. As far as I know the 1oz was generally considered a "High Velocity" load in the 2�" 12 but never Standard Per Se. Standard for the 16ga 2�" was 7/8oz & for the 20 3/4oz.
Guess what 1 1/16oz in 12, 7/8oz in 16 & 3/4oz in 20 will have almost identical shot column lengths which means they have almost equal density of loading. They will thus fit into the same length shell with about the same amount of wadding etc. Wonder if that was co-incidental. If loaded to identical velocities with the same powder each step down in gage size would show slightly more pressure due to a higher percentage of the shot making bore contact, thus more friction proportionally.