Boolit Weight, Barrel Length and FFFG v FFG, Help Me Understand

[ArizonaFlinter]

Correct me where I am wrong. I have a book that I remember saying FFFG is for 45 cal and below and FFG is for 50 cal and above. Yet folks keep talking about FFFG for 50s. It seems like the faster FFFG should work better for Lighter boolits (they accelerate faster) and shorter barrels (less time to accelerate). Is this reasonable?

[mooman76]

That was the old way of thinking. Many use fff for 54 cal and even larger now adays. You really got to work up the loads to see what works best for your guns. It was also said use dead soft lead only but many fins that WWs work fine for roundballs also.

[ArizonaFlinter]

mooman76, Thanks, much of my data is from days gone by.

[fouronesix]

A Flinter,
If you look through the different Lyman Blackpowder/Muzzleloader handbooks from the Mid 70s to present you'll find various FF and FFF loads. The rule of thumb you're thinking of is somewhat valid because FFF will generate more pressure than FF- all other things equal. Some of the FF or coarser "rule of thumb" was intended for the larger calibers simply because of the thinner barrel walls associated with the larger caliber muskets, rifles and shotguns thus they were less capable of handling the higher pressures generated by the FFF. It is still a good rule of thumb for many applications. When working on "non standard" applications I do look at the pressure data available from Lyman and others and adjust my charges accordingly. As to the shorter barrel thing with the faster powder? I don't know how valid it is with blackpowder- but it's somewhat valid of course with progressive smokeless powders.

Hard to second guess results on target and performance but one thing that may happen with the FFF vs FF is that in those loads for the bore diameter solid base conicals, there may be some advantage to getting the pressure and acceleration up quickly thus obturating the bullet quickly thus preventing undue skid when it first starts out. Just a theory on how it may work. Conversely, when working with other types of muzzleloader projectiles like patched roundballs and miniés there may be some advantage to a slightly less violent start down the bore and that may favor FF over FFF.

Also, as an example, I found it interesting and counterintuitive that a 50 gr charge of FF blackpowder under a patched roundball in a 50 cal was a little cleaner burning than a 50 gr charge of FFF under a patched roundball. Wano brand powder for both. I never have completely figured that out.

[451 Pete]

Fouronesix,

Black powder, when burnt in a barrel, burns differently than smokeless. The powder will continue to burn as it drives the projectile down the barrel. This more so distributes the pressure of the charge over a longer length of barrel rather than the bulk of the pressure only being in the breech area of the barrel. For any given bullet and caliber there is a point where too much black powder will become a part of the ejected mass along with the bullet. (Thus another old rule about checking your charge by shooting over a sheet or snow to find the maximum useable charge by backing down the charge to where no unburnt powder is found after firing the gun does have some merit. ) Don't be fooled, black powder can develop a lot of pressure. At around the turn of the 20th century the U.S. Navy did some pressure testing with black and was able to generate pressures of around 100,000 psi.

One other thought I have is that additionally the older guns ( and even some of modern manufacture today ) do not have the quality of steel in the barrels of what would be considered safe for modern smokeless barrels. These barrels are proofed for black powder and not for smokeless. They are safe for what they are designed for and should be shot using what the manufacturer deems as being a safe load in the gun. Can you substitute finer grades of powder ? Well, yes to some extent. It will work and work well in light or reduced charges. The finer grades of black powders burn more rapidly and generate higher pressures than the coarser grades but as Lyman shows in their pressure testing, the gain in velocity is not enough to outweigh the increased resultant pressure generated so the larger granulation of powder is what is generally recommended.
I cant prove this but I have a theory. I have found similar results to what you found in testing your .50 caliber and comparing fouling left from 2fg. as compared to 3fg. I noticed the same as you about the fouling difference in using the Swiss brand powder's in a .38 caliber bullet gun. My thought is that the finer granulation is more completely consumed in the barrel and therefore leaves a higher percentage of its volume in residue or soot than what the coarser grade of the same powder will do.

just my thoughts ... Pete

[fouronesix]

No question about the differences between BP and smokeless- that's one of the things I was referring to in the response to A Flinter. For those of us who do a lot of work with both BP and smokeless it requires a "mental" transition of assumptions that have to be made when going from BP to smokeless or vice versa. As to the unburned powder out the muzzle as seen on say fresh snow?? I think no matter at what pressure or granulation, it is well known that a large portion of BP is not consumed or otherwise converted to gas but is ejected as suspended solids- it varies some but on average it's about half and half, +/- 10%. So while the concept of unburned particles visible in snow out the muzzle is valid, the fact remains about the total solids ejected. In some cases the solids will be of larger particles and be more visible. In some cases the solids will be much smaller- maybe almost colloidal in nature and not be so visible.

[fouronesix]

I cant prove this but I have a theory. I have found similar results to what you found in testing your .50 caliber and comparing fouling left from 2fg. as compared to 3fg. I noticed the same as you about the fouling difference in using the Swiss brand powder's in a .38 caliber bullet gun. My thought is that the finer granulation is more completely consumed in the barrel and therefore leaves a higher percentage of its volume in residue or soot than what the coarser grade of the same powder will do.

just my thoughts ... Pete

That's as good a theory as I've heard. Probably has some validity.