Analysis of Powder, Bullet, and Barrel Interactions
 

An article I figure some here would find interesting and possibly useful, https://dsiac.dtic.mil/articles/analysis-of-powder-bullet-and-barrel-interactions/

Enjoy.

Interesting, but an awful lot of specific to his discipline "engineering speak". He may have written this for other ballistics engineers, but he certainly did not write it for lay people, or even exceedingly advanced handloaders. At that level, this paper is actually pretty useless, save for one sentence in his conclusion: These results conclusively show that propellant selection can indeed affect dispersion.

Ammunition companies and handloaders have understood this simple fact for as long as we have been making firearms go "bang". Even back in the muzzle loader days, with black powder being the only available option, shooters understood that their choice of powders would affect the accuracy and velocity they could expect from their firearms.

Smokeless powders, with their far greater variety of burn rates, only served to complicate matters further. Their introduction increased the need for us handloaders to "work up a load" in any given firearm. The factories do not have that need, or that luxury, or however you want to view it - their loads must work well and be safe in all firearms chambered for any given cartridge. As such, factory loads will always be a compromise, with the only thing they can really quantify being safe pressures and adequate velocities from their test barrels.

"Working up a load" is the fun part for those of us who handload. Depending on what we will be doing with any given firearm and load, priorities will vary. For me and most of my guns, it's all about hunting performance, so I typically choose the bullet first, and will give up some accuracy and maybe even a wee bit of velocity to use that bullet. Next it has to chamber and extract, fired or unfired, without a hitch. I will typically try three or four different powders that several loading manuals agree might provide top velocities. Each powder selection is first loaded with the lowest listed charge weight, a "starting load", shot for accuracy over a chronograph so I get velocities as well. I creep up incrementally, one grain of charge weight at a time, shooting for group size and velocity until I find a combination that I like best. It may not always be the most accurate, it may not always have the top velocity, but it will always be the best compromise of many factors. These are hunting loads, so gilt edged accuracy is not as critical as in target loads.

Target loads are far more difficult and time consuming. Here, in addition to what I do to work up a hunting load, I add several bullets, even several bullet weights to the mix. Seating depth then becomes much more important, with small variations having a dramatic affect on accuracy, where hunting loads we just need to fit the magazine and chamber and extract easily. I usually test more powders as well, further adding to the time commitment. Things like chambering and extraction may not be as important depending on the discipline. Sometimes benchrest loads will have to be fired to be extracted without sticking the bullet in the throat and dumping powder down into the action, for example. "Over the course" NRA High Power loads cannot be assembled this way, but they do chamber much more tightly than pure hunting loads.

So, yes, it has been very well understood for, dare I say, at least a couple of centuries that powder selection will affect group size. In some rifles group size will vary dramatically, but that is often an indication that there might be something wrong with the rifle.

Well said !

About 25 years ago when I first started shooting with black powder instead of that weird stuff my mentor said "do not rush". He was right as it took me 6 months to work out the correct loads for my Sharps and Rolling Blocks, as many more things affect the grouping at 300 yards or shorter distances. The I sold the cartridge rifles (3) and went with muzzle loaders and the variables affecting my target grouping went up exponentially it seems. again my mentor said try to make some of the items constant and work with what cannot be the same every shot.
1000 yard target shooters are just about the same and the 1 mile shooters are even more critical of the things that can affect shooting accuracy.
Finally it comes down to the shooter and the day they shoot and as some call it "luck".
John Rogers

Maybe a note of caution for using faster high explosive (modern) ammo in older thin-barrel weapons such as shotguns. They may require specialize loads to be safe at all.
Also harder steel-cased ammo (such as Russian Wolf brand made for Ak's) may not be the best thing for those delicate barbie dolls.

Absolutely. As a guy who shoots mainly 19th century guns and their modern continuations and reproductions, I agree - this cannot be over emphasized.

Arms designed for black powder, even modern day iterations, must be approached with caution when using smokeless powders. For some, like those pretty Damascus barreled shotguns, smokeless is entirely off limits. For others, like my Peacemakers, originals up to 1901 are black powder only due to their cast iron frames and non heat treated cylinders, but modern examples can be safely fired with appropriate smokeless loads.

Modern made Model '74 Sharps rifles from the two manufacturers in Big Timber are unbelievably hell for stout. Originals were designed with a lot of steel in the action and barrel, because it was the only way to provide the strength needed. Translate that design into modern heat treated steels and we have some of the strongest rifle actions ever made. They will readily digest some unbelievable high pressure loads. That said, I have never even tried, I have no interest in that. Black powder only for me in those rifles.

I don't shoot those rifles in those calibers, but an awful lot of the guys at my club shoot them. I've never seen an issue but, admittedly, I don't pay attention to those guys. They seem to function just fine, even if they shoot shotgun patterns (ammo, rifle, shooter, or all of the above?). Is this stuff harder on rifles? Not surprising if it is, due to that steel case.

I think it has to do with case lip expansion, and then sealing and fouling of moving internals. Powder chemistry may be involved.
Plus wear on the slides and extraction mechanisms.
IDK. Still learning.

I dislike loud noises..aka especially adverse surprises..in general..but the technology itself fascinates me. Another puzzle to figure out. For instance I was once looking into timed-delay rounds for the GAU-8 to be able to pepper an entire mountainside or remain whole as penetrative against armor. That tech already exists to my understanding. Probably stolen already.

The cartridge case is meant to act as a "gasket" of sorts. We use brass because it is soft enough to expand at the case mouth under the pressure generated when the powder burns. If it fails to fully seal, we get that burnt powder residue around the case mouth or even down the length of the case. This is never a good sign. When it happens, it usually happens pretty inconsistently, leading to variations in velocity and the attendant accuracy falloff. If we shoot enough, it will eventually foul the chamber to the point that it may become difficult to chamber and/or extract rounds. I can see where steel cases would lead to more difficulties of this nature. I guess, though, if the chamber is sloppy enough, the gun will keep shooting regardless. That's all we really want in a military small arm anyway. As a civilian, though, I would be looking for better.

And yes, I believe you are correct, in that powder chemistry is not exactly ideal in these rounds either. I bet whatever cheap, produced by the tons for military use powder they use in these is very erosive and corrosive as well. I bet it burns the throats right out of the rifles in which it is used.

They probably still use mercuric primers just to add a little icing on the cake. Cheap to make, but corrosive as hell. All in all, a pretty unholy mix that I don't think I would ever have anything to do with. Maybe if I had some cheap ass surplus sheet metal SKS or something, but I don't see one of those in my near future either. As Townsend Whelen once said, "only accurate rifles are interesting". I prefer "interesting" rifles, thank you very much.

My AR in 72x39 is more accurate with the cheap Wolf/Tula steel case ammo than my very similar .223 AR build is with PMC ball ammo. My hunting loads in my 762x39 bolt action (Howa mini) run just over 1moa consistently, using a .308 bullet in a .310 bore - I should be able to get a sub-moa load going if I ever spend the extra money on .310 bullets....

Steel cases still have the case mouth expanding while firing, etc. just they spring back closer to original spec than brass does. The biggest issue is increased wear on extractors.

None of the cheap steel case stuff has been made with corrosive powder or primers since the old stashes of Norinco, etc. dried up forever ago.

Thank you, that is great information. I know nothing about this stuff (and I can prove it). Way, way outside of my areas of interest, so I have just never owned these kinds of rifles. It's nice to hear from someone who really knows what's going on with them.

One thing I had heard was this thing with their .310" groove diameters. What a PIA, really, but I suppose there must have been some reason for it. Maybe no more than Cold War paranoia regarding interchangeability and all of that.

It is surprising to me that a .308" bullet, a jacketed one at that (I assume) could shoot well at all in a .310" groove diameter. What we think we "know" about all of this tells us that a jacketed bullet won't "bump up" to fill the rifling like a soft lead cast bullet can. I have heard, from many people, that this actually does work fairly well.

My experience is with old black powder cartridge arms. Many originals were chambered in such a way that they would only chamber a cartridge loaded with a bore diameter bullet. The modern convention is to use cast bullets about .001" larger than groove diameter, so they swage down going through the throat and the leade. They seal much better that way.

Rounds loaded with these oversize bullets will not, however, chamber in many 19th century black powder cartridge rifles. They were still learning. Muzzle loaders, by design, simply cannot be loaded with oversized projectiles, and they worked o.k., didn't they? They were all loaded with bore diameter or smaller bullets, weren't they? We counted on black powder to "bump up" soft lead bullets, and it does. So that's how cartridge rifles started.

And it works. With dead soft lead bullets wrapped in a paper patch, the precursor to the copper jacket. With dead soft grease groove bullets, yeah, still kinda works, but we get a lot of leading. We want to shoot oversize grease groove bullets to avoid all of that, but we can't. So unless we want to paper patch (a monstrous PIA, by the way), we're kind of stuck.

I have a first year (1885) Winchester Highwall chambered in .40-70 Sharps Straight that was chambered that way. I tried everything, including paper patching, which was the only thing that worked. I got tired of rolling paper onto bullets and finally sent it off to my favorite black powder gunsmith. He opened up the chamber for me so I could load groove diameter + bullets. What a difference - it now shoots extremely well with bullets cast .001" over groove diameter. Here it is, along with a round loaded with a 300 grain bullet from an RCBS mold, next to a .30-'06 round:

http://forums.pelicanparts.com/uploa...1754594959.jpg

http://forums.pelicanparts.com/uploa...1754594959.jpg

But, yeah, back to that 7.62x39 and .310" groove diameters and .308" diameter bullets. That relationship worked with black powder and soft lead bullets. It's not supposed to with jacketed bullets and smokeless powders. But it does. Sometimes everything we think we "know" goes right out the window.

So my buddies that play in teh land of smokeless powder muzzle loaders do a lot with this. Cartridge guns going .001 over groove diameter is fine, as is full engagement, or in my case partial engagement with a flat base bullet and a powder with enough kick to make it fully obturate. With a front stuffer of any type though, you gotta get that bullet down the bore first.... If not using sabots (which does make things easier...and a 195-225gr .40 cal bullet at 2600fps is nothing to sneeze at) they always use flat base bullets (boat tails won't properly obturate and engage rifling) and they size them to run down the bore with only .001 or .002 of engagement in the rifling. The other choice they go with is to use a piece of their barrel cut off when having their guns built and making a full-engagement sizing die, so they pre-engrave the bullet with the barrels rifling so it is easy to load and already has near full engagement. And to make all of this work with proper obturation, they use a few select powders that are fast enough to give a quick kick in the pressure but slow enough to be a rifle powder for a 24"+ barrel (N110, N120, and other stick powders). And to be honest, they do some absolutely amazing stuff that is competing with centerfires - and winning. Well under MOA groups at 500+ yards...

People complain that the cheap Russian ammo, due to the steel case, will prematurely wear out the bolt in an AR-style rifle. Well, a new $60 bolt every few thousand rounds is a lot cheaper than buying the same number of rounds of brass FMJ ammo. I have a ton of the Russian stuff stockpiled, have shot a lot of it, never had an issue other than it being dirtier.

It's kind of died out around here now, but up until about ten years ago we had a very active black powder cartridge rife match circuit. We typically fired two day stage matches at 200, 300, 400, 500, and 600 yards. A couple of times a year we shot at 1,000 yards on a local military base. Rules were NRA Target Rifle or Dominion of Canada Rifle Association. These rules allowed for rifles up to 15 pounds, cast lead alloy bullets only, and either straight black powder, Pyrodex, or black powder duplex loads. Interestingly, the top shooters always used straight black powder, shunning the substitutes or duplex loads.

Our scores would match those of NRA High Power competitors at similar ranges. We would actually shoot side by side with them on the military base, since they had so many firing points and neither group could fill it up. They were always stunned that our scores meet or beat theirs. It was a lot of fun showing them what these old rifles could do.

I had two main match rifles, an 1875 Sharps in .45-70, aka .45-2.1", and an 1874 Sharps in .45-100, aka .45-2.6. I used a 540 grain Paul Jones Creedmoor cast 20:1 lead/tin, fired as cast at .460" diameter in both:

http://forums.pelicanparts.com/uploa...1754667365.jpg

http://forums.pelicanparts.com/uploa...1754667365.jpg

Jeff, this might be off the topic a bit, but I was wondering if there is any or perhaps significant erosive wear to the touch holes on flintlock pieces. I have read about the problem with high use muzzle loading artillery pieces and suspect better metallurgy and smaller loads would negate such an effect. That being said, rather than assume, I thought I would ask someone who is familiar with the sport. I just geek out over a lot of technical stuff.