Air Gap - rehash of a dead horse's beating

FrankenMauser · May 3, 2024, 01:28 AM

Alright, I know the conventional wisdom is that an air gap in BP loads is a pipe bomb death sentence.

But is it really?

I have recently been loading homemade BP in my .577/450 Martini Henry, which was very easy with which to eliminate air gaps, since my amateur methods resulted in rather low density BP (but fast burn rate).

I have been reading reports all over the place, from books, to forums, to discord posts, to the distant tendrils of the interwebs.
Nothing agrees.

The only commonality is:
-People that think air gap is bad have never tried it. Or, they're referencing old reports that were small granulation (3f or finer) with a notable air gap to the projectile. More often than not, the "failed" firearm is a handgun or small bore rifle.
-People regularly shooting air gap loads in cartridges with no ill effect, but almost exclusively large capacity, large bore rifles, using 1F or 1.5F BP.

It is too late (literally, I need to go to bed) for me to go digging for references, but there were supposedly 19th century standard .577 Snider and .577/450 loads that had air gaps.

Where does this "air gap danger" come from?
And is it real?

ligonierbill · May 3, 2024, 04:52 AM

The Bevel Bros in Muzzleblasts reported on this as related to muzzleloaders some months back. No, no pipe bomb. I've done it unintentionally in a front stuffer, and what you will get is lower and inconsistent velocity. I load 577/450 myself: 70 gr Black MZ (still have some) and stuffed with tow. The old cordite rounds were, I believe, filled with kapok. They work fine. No worries. All you're doing is holding the powder in place.

mehavey · May 3, 2024, 08:09 AM

No.

As noted by the fact that every Sharps carbine loads with loose powder/inherent gap(s) in the ignition chamber.

FrankenMauser · May 3, 2024, 11:08 AM

Quote:

The old cordite rounds were, I believe, filled with kapok.

Yea, kapok or cotton wool.
I am using wool roving in loads with Swiss 1F, to reduce fire danger on our range and in the field. The risk is still there, but reduced. Probably isn't going to smell very good.

Hawg · May 3, 2024, 11:55 AM

The air gap is overrated. A non issue in a revolver, cartridge or C&B. I'm not sure how much of a gap it would take to bulge a rifle barrel but I think it would have to be a gap measured in inches. I used to buy into the air gap deal until I got a 63 Sharps. The chamber held 110 grains of powder with a bullet seated. The factory recommendation was 80 grains but specified the powder had to touch the bullet. However there were countless videos of people shooting them with 60-80 grain charges and bumping the butt on the ground to get the powder against the breech.

Jim Watson · May 3, 2024, 03:15 PM

And Scheutzen shooters usually breech seat which about insures a gap between the over powder wad and the bullet.

The Swiss .41 Federal uses the Wild System ramrod with a stop to place the ball about
.10" over the the standard powder charge.

Yet there is a guy mentioned on the Shiloh board who says he can ring a chamber on demand.

A friend loaned out his TC Hawken and got it back with a bulge in the barrel. Seems the user had failed to get a ball all the way down a fouled bore and had elected to shoot it out.

I have gotten best accuracy in BPCR with the bullet down on a card wad with the Swiss powder only compressed about the thickness of the wad.

5whiskey · May 5, 2024, 07:36 PM

Interesting. I've only been shooting BP for 7 or 8 years, and I haven't jumped in on BP cartridges yet (excluding paper cartridges I've made a few of those). I've just always generally believed that an air gap is bad. Interesting if it isn't quite as dangerous as what I've believed.

deerslayer303 · May 6, 2024, 01:56 PM

https://youtu.be/icolNUAY5ig?si=-E07Fvkf89OxdDOa

Hawg · May 6, 2024, 05:09 PM

Quote:

Originally Posted by deerslayer303

https://youtu.be/icolNUAY5ig?si=-E07Fvkf89OxdDOa

Thanks for posting that. So 35 or so inches of air space won't bulge a barrel. Good to know.

Deltadart · May 7, 2024, 07:39 PM

Hawg, as long as the barrel is 32 inches long it will not.

Hawg · May 8, 2024, 01:38 AM

Quote:

Originally Posted by Deltadart

Hawg, as long as the barrel is 32 inches long it will not.

So why would 32 inches not bulge but 24 would?

ligonierbill · May 8, 2024, 05:22 AM

He's making a funny. Find the Bevel Brothers' article and enjoy.

May 3, 2024, 01:28 AM	#1
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,447	Air Gap - rehash of a dead horse's beating Alright, I know the conventional wisdom is that an air gap in BP loads is a pipe bomb death sentence. But is it really? I have recently been loading homemade BP in my .577/450 Martini Henry, which was very easy with which to eliminate air gaps, since my amateur methods resulted in rather low density BP (but fast burn rate). I have been reading reports all over the place, from books, to forums, to discord posts, to the distant tendrils of the interwebs. Nothing agrees. The only commonality is: -People that think air gap is bad have never tried it. Or, they're referencing old reports that were small granulation (3f or finer) with a notable air gap to the projectile. More often than not, the "failed" firearm is a handgun or small bore rifle. -People regularly shooting air gap loads in cartridges with no ill effect, but almost exclusively large capacity, large bore rifles, using 1F or 1.5F BP. It is too late (literally, I need to go to bed) for me to go digging for references, but there were supposedly 19th century standard .577 Snider and .577/450 loads that had air gaps. Where does this "air gap danger" come from? And is it real? __________________ Don't even try it. It's even worse than the internet would lead you to believe.

May 5, 2024, 07:36 PM	#7
5whiskey Senior Member Join Date: October 23, 2005 Location: US Posts: 3,667	Interesting. I've only been shooting BP for 7 or 8 years, and I haven't jumped in on BP cartridges yet (excluding paper cartridges I've made a few of those). I've just always generally believed that an air gap is bad. Interesting if it isn't quite as dangerous as what I've believed. __________________ Support the NRA-ILA Auction, ends 03/09/2018 https://thefiringline.com/forums/sho...d.php?t=593946

May 6, 2024, 01:56 PM	#8
deerslayer303 Senior Member Join Date: January 10, 2011 Location: Leesville SC Posts: 2,656	https://youtu.be/icolNUAY5ig?si=-E07Fvkf89OxdDOa __________________ "I prefer dangerous freedom over peaceful slavery." - Thomas Jefferson

May 3, 2024, 04:52 AM	#2
ligonierbill Senior Member Join Date: May 20, 2007 Posts: 2,467	The Bevel Bros in Muzzleblasts reported on this as related to muzzleloaders some months back. No, no pipe bomb. I've done it unintentionally in a front stuffer, and what you will get is lower and inconsistent velocity. I load 577/450 myself: 70 gr Black MZ (still have some) and stuffed with tow. The old cordite rounds were, I believe, filled with kapok. They work fine. No worries. All you're doing is holding the powder in place.

May 3, 2024, 08:09 AM	#3
mehavey Senior Member Join Date: June 17, 2010 Location: Virginia Posts: 6,918	No. As noted by the fact that every Sharps carbine loads with loose powder/inherent gap(s) in the ignition chamber.

May 3, 2024, 11:55 AM	#5
Hawg Senior Member Join Date: September 8, 2007 Location: Mississippi Posts: 16,195	The air gap is overrated. A non issue in a revolver, cartridge or C&B. I'm not sure how much of a gap it would take to bulge a rifle barrel but I think it would have to be a gap measured in inches. I used to buy into the air gap deal until I got a 63 Sharps. The chamber held 110 grains of powder with a bullet seated. The factory recommendation was 80 grains but specified the powder had to touch the bullet. However there were countless videos of people shooting them with 60-80 grain charges and bumping the butt on the ground to get the powder against the breech.

May 3, 2024, 03:15 PM	#6
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,581	And Scheutzen shooters usually breech seat which about insures a gap between the over powder wad and the bullet. The Swiss .41 Federal uses the Wild System ramrod with a stop to place the ball about .10" over the the standard powder charge. Yet there is a guy mentioned on the Shiloh board who says he can ring a chamber on demand. A friend loaned out his TC Hawken and got it back with a bulge in the barrel. Seems the user had failed to get a ball all the way down a fouled bore and had elected to shoot it out. I have gotten best accuracy in BPCR with the bullet down on a card wad with the Swiss powder only compressed about the thickness of the wad.

May 7, 2024, 07:39 PM	#10
Deltadart Senior Member Join Date: April 26, 2015 Location: Washington State Posts: 289	Hawg, as long as the barrel is 32 inches long it will not.

May 8, 2024, 05:22 AM	#12
ligonierbill Senior Member Join Date: May 20, 2007 Posts: 2,467	He's making a funny. Find the Bevel Brothers' article and enjoy.