9MMand223only said:
Is there some sort of scientific proof or scientific paper to support a claim that ball powder has ignition issues? I highly doubt it.
You'd be highly wrong. Military ordnance has studied this stuff to death. They have machines that measure ignition delay, heat and energy output rates and even the infrared and ultraviolet light spectra emitted by primers. There are sensitivity tests (h-tests) where a 3.94 oz weight is dropped onto a fixed firing pin from different heights to produce different impact energies and qualifying primers have to go off or not go off within standard deviations either side of the 50% firing rate point within certain drop heights. There is a whole huge lot qualifying process that requires samples of thousands of primers before a lot is accepted as qualified, including firing tests for powder ignition down to -65°.
To get some of the flavor, Google up and read MIL-P-46610E. It's from 1967 but gives you a sense of how thorough qualification testing is. It's only gotten more comprehensive since then.
Google up and read REPORT MDC A0514, from McDonnell-Douglas. The 1970 version gives primer reconsolidation recommendations from Olin and Remington of 0.002-0.006". Then when you get to the April 1982 revision you find Naval Ordnance at Indian Head (NOIH) has revised and narrowed it to 0.002-0.004" because extensive testing showed that improved reliabiilty.
But for a first overview of the nature of the beast, the best primer on primers is probably
this article by Allan Jones who worked in primer development at CCI, and who explains they changed their magnum primer formulation in 1989 specifically to address these problems. Obviously, they had to study the matter and do testing to come up with the change. He explains a lot about the process.
locknloader said:
How do you know if a powder is "hard to ignite" and you are having ignition issues?
For the average shooter a chronograph and group size are the basic indicators. Velocity SD's are higher when ignition is irregular for any reason. Groups get larger beause the time between when the primer pressurizes the case and when the powder pressure peaks becomes variable, letting small movements and vibrations and shooter problems like poor follow-through all have more time to point the muzzle somewhere else.
I often see that ball powder for 223 is "hard to ignite" and that military rounds use a magnum primer to ensure ignition with the ball powder.
Military rounds have to function at -65°F to be operable at higher aircraft altitudes. It takes more energy to ignite powder at low temperature, and this is the primary reason, AFAIK. Military ballistically and functionally compatile ammunition is loaded to tighter velocity standards than SAAMI standards call for (±30 fps vs. ±90 fps) and has not only to stay under the familiar maximum pressure, but also has to meet gas port pressure requirements. All three have to be possible to do with a particular powder before it qualifies for use in a load, as well as the extreme temperature firing specs. If a primer let them down in any of these areas it would be disqualified. The accuracy requirements, however, are not stringent by match handloading standards, so that is not going to have the focus it does with a civilian match shooter.
Ball powders are harder to ignites because they control progressivity of the burn entirely by deterrent concentration. Where stick powders apply deterrent to the outside of a grain so it tends to burn mainly from inside perforations outward to grow the burning surface area to get progressively greater speed of gas production, the spherical grain is burning inward and always having a smaller and smaller burning surface. So the only way to get them to make gas faster as they burn is to grossly slow down the burn rate of the exterior of the grain and have the deterrent penetrate the grain in concentration that decreases with the depth of the burn so the powder grain burns enough faster to outpace the shrinking surface area and make gas at a progressively higher net rate up to the point the grain gets too small even for that strategy to work.
Note that modern spherical chemistry used in Western's Ramshot line claims to have overcome the ignitability problem high surface deterrent coating and penetration levels cause, and claim you do not need magnum primers with their producty. I would still recommend testing for yourself in your gun and chambering and with your bullet selection to be sure.
How is this trait expressed?
If you read the Allan Jones article I linked to above, you will learn something about this. The velocity spread I mentioned is one. Jones also describes a rejected formulation that caused ignition delays of tens of milliseconds that could certainly let a barrel move some. That same thing can happen with inadequate priming or if you don't seat your primers to "set the bridge" (aka, reconsolidation) by squeezing the anvil down into the pellet the 0.002-0.004" past the point of anvil contact with the floor of the primer pocket that NOIH found best. Probably 90% of ignition problems can be fixed by proper primer seating, so you want to be sure you can do that first before you spend money on different primers. If you can't measure it, try just seating the primers rather hard.
"There is some debate about how deeply primers should be seated. I don’t pretend to have all the answers about this, but I have experimented with seating primers to different depths and seeing what happens on the chronograph and target paper, and so far I’ve obtained my best results seating them hard, pushing them in past the point where the anvil can be felt hitting the bottom of the pocket. Doing this, I can almost always get velocity standard deviations of less than 10 feet per second, even with magnum cartridges and long-bodied standards on the ’06 case, and I haven’t been able to accomplish that seating primers to lesser depths."
Dan Hackett
Precision Shooting Reloading Guide, Precision Shooting Inc., Pub. (R.I.P.), Manchester, CT, 1995, p. 271.
Where's the faceplant emoji when you need it 