Lest we forget, the "Short-Fat" technical idea.

I'll start with context just opposite of this discussion: The 30-06 Springfield.
I'm risking offense, I know, but truly this cartridge represents everything poor in cartridge design.
It has a long powder column, high body taper, 17.5deg shoulders, overbore even while relatively large in caliber.
On firing, a significant portion of unburned powder is compacted into a slug which travels down the barrel against the bullet, adding driven mass. That powder slug ignites at muzzle release, causing a big ole flash, backfiring down the bore to cause secondary pressure spiking, and slapping the back of released bullets. There seemed nothing to stop this from happening, except to invent every improved .473 casehead cartridge for the past 113yrs. That's worked better.
But Gibb's described a counter, front ignition, to ignite the powder column at the front. This, containing powder burn inside the chamber(instead of down the bore & muzzle). Much like (and probably better than) short/fat columns with low body taper and high shoulder angles.
This was not solely for 30-06 of course,, I just needed to start somewhere..

In function, front ignition is provided by extending the flash hole ~2/3 into the powder column -with a flash tube. It would be easy enough to make, but not so easy to reload.
I'm thinking depriming would need to be done externally with a corkscrew type primer puller (like corks from wine bottles). A flash tube could be plugged to prevent powder entry using a finger rolled ball of flash paper. Stuff like that.
The tube would reduce capacity that much, so the case should be a chosen with this in consideration.
fcpg5e.jpg
 
Mike:

I thought this might be what you were talking about when you said "front ignition". I believe it is a common ignition system in large bore artillery shells.

But I think the statement needs further examination:

"That powder slug ignites at muzzle release, causing a big ole flash, backfiring down the bore to cause secondary pressure spiking, and slapping the back of released bullets."

Lotta parts of that to look at.

Is there indeed a "powder slug" that ignites at muzzle release? It sounds like you're describing unburned powder being blown out behind the bullet. With some powders, I suspect that might happen. But there are surely powders that would be consumed entirely in the barrel, so if this were an issue, changing the load would solve it.

There is indeed a flash when the bullet exits, no matter what powder is used. Would it be attenuated by igniting the front of the powder column? I would like to see a demonstration of this. I won't say I don't believe it, but given the amount of pressure driving the bullet, I would expect the hot gasses would be nearly the same no matter where the powder load is ignited. In fact I would expect the volume of hot gas that exits immediately behind the bullet would be greater if all the powder is burned before the bullet exits, which I think is what you are suggesting would happen with front ignition. Unburned powder means powder that has not turned into expanded gas, after all.

Does that overpressure indeed backfire down the barrel? Seems unlikely to me, as its pressure will not be greater than the pressure inside the barrel.

Does it slap the heel of the bullet? Well, it likely continues to push on the back of the bullet, but "slap" it? I cannot see why it would. That implies the bullet has gotten ahead of the gasses pushing it, then they catch up. I'm having a hard time seeing how that would happen.

It seems to me the pressure wave would just continue to expand outside the muzzle, dissipating over time. Again, if there is unburned powder in a rear ignition case and not in a front ignition case, there is more more pressure to expand at the muzzle.

Of course I know what seems reasonable to a layman might not be how the laws of physics work, but I'm thinking I'd like to see high speed video that demonstrates gas "backfiring" into the barrel or shows the heel of a bullet being "slapped" by the expanding gas. I just have a hard time wrapping my head around that.

Companies that produce primers and smokeless powders have had more than a century to examine the burning characteristics of a .30-06 load. I would hope they have optimized the selection of powder and primer to get the most efficiency out of the cartridge. If unburned powder is indeed following the bullet out, a hotter primer or faster burning powder would seem to address that problem.

If front ignition offered a perceptible advantage, it would not be hard to fabricate a primer similar to a shotgun primer with an elongated trunk that would move the flash further into the powder column. I would like to hear from the makers of powder and primers about whether they have ever considered or tested such a modification, and what their conclusion was.
 
As mentioned, the frontal ignition system has been around for a long time in larger cartridges like the 40 mm and up mainly because of the powder column length and powders of the time.

This is one of those theories that should work in hunting cartridges and more than one person has tried it including me. the results were mixed
and the real benefit was never proven in my testing. (Less barrel erosion from un burnt powder.

There were many problems building and using the flash tubes and any improvements in velocity and accuracy did not show up in fact velocity took a hit.

I made my tubes by threading the tube and the primer pocket (There are other ways but this seemed like the best way at the time). In order to prevent powder from entering the front of the tube and filling up (Defeating the process) I pinch the end off and used a slotted tool to unscrew the tub from the inside through the neck. I even tried to use Dacron fibers to stuff the end of the tube (It will burn up with firing) but the case capacity was to unpredictable and SDs suffered.

The back of the tube had an internal shoulder to seat the tube on the case base/web. and the inside of the tub that threaded in the primer pocket was bored to take a primer, This way i could remove the tube for cleaning the tube and the case. after cleaning and reassembling I could prime the conventional way . Decapping was another problem and I found that after the tube was removed drilling was about the only way except with a long punch.

It was a very labor intensive process and proved not to be any better
Although it was interesting to try. I wish someone else would try it or if they did post their results.

Just one of my many failures.

J E CUSTOM
 
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J E Custom:

Not a failure if you learned something from it.

Seriously, though, if anyone wants to give this idea further analysis, a good starting point would be a modified shot shell primer. They'd have to enlarge the primer pocket and drill it all the way through, plus relieve space for the flange, but they'd put the flame front a few millimeters further forward. And a shotshell primer just uses a large rifle primer plus another brass cup for it to be seated in. If you really wanted to test a deeper ignition, it might be necessary to build a replacement cup that is longer. But it would be a good place to start.
 
"I'll start with context just opposite of this discussion: The 30-06 Springfield.
I'm risking offense, I know, but truly this cartridge represents everything poor in cartridge design."

I'm certainly not offended, but these lines are absolutist when "everything poor" is included, given the factual data over history. I've done quite a bit of case analysis in the medical device field and this argument would not go too far. To invent something is one thing. It is much easier to improve an existing design, but you have to give the original design its due, if successful at all.
 
I did mean this purely w/resp to case design, in contrast to improving designs.
I'm sure millions of guns have sold in 30-06, and that as many game have been taken with them in the past 113yrs. Couldn't say anything bad about that, or in it's function in general. And it's not like small arms ballistics have evolved a whole lot beyond over this time.

You gotta know I do not want to aggravate ~50 million 30-06 users out there.
But I needed a standard to base iterations of improvement for.
 
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IMO, there have been more substantial improvements in bullet and powder technology effecting cartridge performance then have been made in cartridge/case design over the past 100 years. Superstars like the 6mmBR and it's derivatives are simply shortened/slight modifications of the 30-06/308, prior designs. This has been the case with many 'new" cartridge designs over the years. Of late, more market acceptance and success seems to be the result of effective marketing as opposed to true innovation.
 
Greyfox said:
IMO, there have been more substantial improvements in bullet and powder technology effecting cartridge performance then have been made in cartridge/case design over the past 100 years. Superstars like the 6mmBR and it's derivatives are simply shortened/slight modifications of the 30-06/308, prior designs. This has been the case with many 'new" cartridge designs over the years. Of late, more market acceptance and success seems to be the result of effective marketing as opposed to true innovation.
Click to expand...

Speaking of cartridge/case design, here's an interesting comparison:

Lay three cartridges on a table in front or you -- a .223, a .30-'06, and a .50 BMG.

Notice anything interesting? They're remarkably similar in terms of case proportions. They're not too far from being scaled-up versions of each other. In fact the .50 BMG (developed in 1911) is defined in Wikipedia as a "scaled-up version of the .30-'06," and the .223 is similarly proportioned.

IOW, the case design for those three cartridges does not appear to have been re-thought even though they were designed 60 years apart. The .308 was the first large-production military cartridge to fundamentally re-think cartridge proportions.

That sounds to me like Greyfox has hit the nail on the head. Nothing new in the world of cartridge design.

Imagine for just a moment if instead of scaling the .30-'06 cartridge design down for development of the AR-15, Eugene Stoner had instead asked Palmisano and Pindell to design a cartridge for his new military rifle. They would likely have come up with something like the 6 PPC (which they later did for bench rest shooting) -- in other words, a short, stubby case, somewhat similar to the short magnums that featured in the beginning of this discussion. Perhaps that would not have made the shoulder angle so steep, so it would feed more reliably in a military rifle and machine gun. But they would most likely not have kept the .30-'06 proportions.

Perhaps they would have gone a little larger -- say, the 6.5 PPC, or a little smaller -- say the .22 PPC. Of course the .22 PPC is not much different from the .220 Russian, Palmisano and Pindell's parent cartridge for the 6 PPC.

In any case, by sticking with the basic proportions of the .30-'06 for the past 115 years, we have the general proportions that have steered American cartridge design, with occasional detours for sharper shoulders (Ackley Improved) or belted magnums. Otherwise, we had to await the arrival of the short magnums to see radically different case proportions.

Sounds to me like an interesting subject for a longer discussion!
 
Lay three cartridges on a table in front or you -- a .223, a .30-'06, and a .50 BMG.

Notice anything interesting

Lol. yeah, I've noticed that...never mentioned it to anyone because they might think I've lost my mind.
 
You touched on it a little bit but I think it's important to emphasize they they WERE all designed as military cartridges. For that reason, smooth functioning, especially in automatic rifles is far more important than TOTAL performance! I don't think this in any way means that they are the most efficient design for what most of us do and it's exactly why the majority of the most competitive shooters use short, fat, low taper and sharper shouldered designs.
 
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