Airspace

[OrangePwrx9]

How come airspace between powder and bullet is no big problem with smokeless but it is with blackpowder??

I know "why" it's bad to have airspace between black powder and the bullet, having already ruined a barrel due to short starting. But how come black powder is sensitive to this while smokeless isn't?

 

[Jonny2guns]

From what I understand, it's because black powder is an explosive but smokeless powder burns. Let's wait for the experts and see how far off I am.

 

[LaneP]

BP is an inefficient, low energy explosive and burns dirtier with less consistency when the grains are not tightly compacted in the powder column. I always charge through a drop tube, but then use at least 1/16" compression in .45 Colt and as much as 1/4" in .45-70. The more compression the cleaner it seems to burn. with Goex 2F, 1/4" compression using a compression die, a 405 gr cast lead bullet and SPG, I can shoot 15-20 shots through my Trapdoor and no issues with extraction.

However back when starting out and not using as much compression, 5-6 shots and cases would start sticking in the chamber.

 

[243winxb]

smokeless powder burns.

True when using published loading data.

Double based smokeless powders, with a high percentage of nitroglycerin, may detonate under certain conditions. https://www.firearmsid.com/Feature Articles/McCord_gunpowder/

Goex BP increases burn rate & pressure as it goes from 2F to 4F. I use 3F in a 45 cal T/C flintlock & get 1900 fps.
"Confined, velocities have been timed at values from 560 feet per second for very coarse granulations to 2,070 feet per second for the finer granulations."

 

[crstrode]

How come airspace between powder and bullet is no big problem with smokeless but it is with blackpowder??

It is not.
This myth is one of the most prevalent and long-lasting bits of hooey on the inter-toobs. It ranks right up there with maroons believing that a 25ACP is similar to getting poked with a pencil, but a North American Arms 22LR is a great defensive choice.

 

[243winxb]

When BP is compressed in a column by the fully seated bullet, the powder burns only on the primers side.

When there is air space, the burn rate is increased. The whole column is ignited instantly. The saltpeter, with the extra oxygen, may increase the burn rate?

It may be as simple as the barrel steel? BP barrels being softer?

A bulged or ringed barrel may be the most likely damage?