What would happen if smokeless powder were loaded like black powder

True case filler*increases pressure -- oft times quite significantly -- especially when used in a fast-powder/low case-fill setting.

While not exact, a decent parallel would be akin to seating the bullet down/onto the powder itself.
Case in point: a normal 40%-fill/14ksi load of Clays in a 45 Colt becomes a 44ksi load if the bullet is seated to the powder.

* as opposed to a simple powder positioner

And as an aside, I knew a guy who had his great grandfather's Colt SAA in .45 Colt. He was sure that black powder would be fine for it, but it turned out that one chamber had a rather large, old crack in it that the eye really couldn't pick up. It blew up, of course.


Cat

Your powder charge will push out the filler and the bullet. The same as if you loaded a much heavier bullet, much higher chamber pressure. Traditional "plastic" fillers compress easily and allow the burning powder gas to expand without a sudden increase in chamber pressure. Cream of wheat will compress to a dense solid with high surface friction with the rifle barrel. A straight wall case (357 mag, 44 mag, 45-70) will allow the cream of wheat to exit the case easily. This doesn't happen in a bottle neck case (.308, 30-06, 7 MM Rem mag). The powder gas has to push that big plug through a smaller case neck raising chamber pressure to dangerous levels.

Your gun, your hands, your eyes, please be careful about what you don't know.

The person who told you smokeless powder can be loaded like black powder is very wrong, especially with fast smokeless powders like Red Dot.

This video is about muzzle loaders. But should give the general impression needed.

Loading smokeless powder in an originally black powder cartridge is OK, as long as one pays attention to the guidelines for powder charges in their reloading manual. Many of today's popular cartridges were originally black powder, but one should not use black powder guide lines when using smokeless (the use of fillers and "fill the case to bullet base"). I started loading a black powder cartridge in '69 using fast smokeless powders (38 Special with Bullseye), and I use a few other smokeless powders in my 45 Colt reloads...

orpington said:

is some dead space absolutely necessary in a smokeless round?

Click to expand...

Orpington, I'm having a hard time understanding your question. But no, "some dead space" is absolutely not necessary "in a smokeless round." Look at most any modern day, smokeless powder reloading manual that lists percentages of case fill and you'll find quite a number of 100% case fills, and even a few "compressed" smokeless powder charges.
On the other hand, all of my black powder cartridge reloading manuals say that 100% case fill, or slightly compressed loads are "absolutely necessary." I was taught to make sure there's no "dead space" in my muzzle loader rifles and pistols too.
BTW, I have experimented with a little Dacron pillow stuffing (never cream of wheat though) in 45 Colt cases to keep small charges of fast burning powder next to the primers. I reduced the recommend powder charges by the same amount as the weight of the pillow stuffing. I couldn't tell any difference as far as accuracy, and the loads smoked worse, so I gave up on using a filler in 45 Colt cases.
I use vegetable fiber wads in my 45-100 Sharps, but that's to protect the bases of the bullets...not take up space. Because if I didn't use a wad, I'd fill the cases with enough black powder so that the charges would be slightly compressed when I seated the bullets anyway.

I remember COW loads (Cream of Wheat) were sorta popular a few years ago. Most used the COW under cast lead bullets to scrub the barrel to eliminate/remove leading. I haven't heard of the practice for quite a while...

kcofohio said:

This video is about muzzle loaders. But should give the general impression needed.

Click to expand...

Yeah, although loading 120 grains of HS6 (a pistol/shotgun powder with charge weights typically in the vicinity of 10 grains) is going to blow up just about any gun! That's up there with the 300 winmag case full of titegroup for guaranteed-kaboom approaches.

You could suggest he use trailboss, this is pretty much what that powder was invented for.

COW + BP ≠ COW + Smokeless
(Don't even think about it)

One of the fundamental differences between black powder and smokeless powder is that practically all the combustion products of smokeless powder are gasses, which contribute to propulsion, while over half the combustion products of black powder are particulates (smoke and crud) which do not contribute to propulsion.

For any given BP load, there is essentially always a "nitro for black" load that gives the same velocity for LESS pressure using nitro powder. The issue is finding that load. Often times it is a highly compressed load of a very slow powder, or else a small charge of a faster powder known to handle low load ratios well. Usually no filler is required.

denton said:

One of the fundamental differences between black powder and smokeless powder is that practically all the combustion products of smokeless powder are gasses, which contribute to propulsion, while over half the combustion products of black powder are particulates (smoke and crud) which do not contribute to propulsion.

Click to expand...

In fact they rob from it, since they have to be accelerated down the barrel along with the bullet. The weight of crud thrown down the barrel is added to the bullet weight from an interior ballistics perspective - it's sometimes called Sebert's factor.

A "new reloader" using smokeless powders in an "antique Colt revolver" is likely a recipe for disaster. If a member of the forum in which he posted his interest in using smokeless, karma and basic human decency suggest that you should warn him off. You can't fix stupid of course, but you may positively influence ignorance.

FWIW, thoughtful use of COW with smokeless was popular in the early 2000s. I tried some in my 44 Magnum lead/2400 loads and it worked as most reported. I was concerned that the COW would mix in with the powder after a while of moving, handling and only tried a few. One just has to figger out how much the COW weighs and add that to the bullet weight to determine a powder charge. Easy peasy...

You ever chronograph the COW/non-COW loads ?