Front ignition cases, Elmer Keith Duplex loading?

Retrieved: 08/27/2016
Last Post: 04/02/2014

Has anyone ever worked with the extended primer tube cases?

I meet a guy last weekend who loaned me ten 1940 Western cases with the Keith Duplex front ignition system tubes. After I am done testing jacketed bullet loads for him, I will get to play with them for awhile.

hunterspistol
Feb 22nd, 2011

Never heard of such a thing, must be why I hang around.

frank l jr
Feb 22nd, 2011

Uncle Sam had a spotter round for a recoilless rifle mounted on a tank like vehicle, had 6, 3 to side if memory serves me. Mounted just above the tracks, would load up, run up to target, shoot the spoter round, then fire the rifles one at a time. This round looked like a shortened 50 Browning, like the new short round. This round had a forward tube primer system.

RicinYakima
Feb 22nd, 2011

Research and Naramore's books tell me that arty and naval rounds have a tube, but the end is plugged, holes opening to the sides, and the tube filled with priming powder.

Elmer Keith "reports" that it worked well in the 50 BMG round, but no where have I read that it worked for anything smaller.

Hopefully Friday, I will take the first loads out for trial.

Old Coot
Feb 22nd, 2011

Ric; I remember reading about the "forward ignition" cases, and that the idea was dropped due to difficulty in manufacturing them; depriming would be an interesting proposition as well, but you seem to have that covered with the really long decapping pin.

RicinYakima
Feb 22nd, 2011

OC, I don't think I would want to make these either. They appear to have about a 1/36 thread, screwed into the pocket from the front with a small flange.

Ed Harris
Feb 23rd, 2011

I fooled with these quite a bit in the cal. .50 M48 Spotting Rifle cartridge used to aim with the 106mm recoilless rifle. An explosive bullet at low velocity matched the trajectory of the 106mm HEAT round and its strikes were readily visble out to about a mile and were used to get on target before firing off the main gun.

In the 1970s the Navy played with a man-pack, suppressed semi-automatic rifle firing explosive spotting rifle rounds to blow up ammo and fuel dumps, during the Vietnam conflict. I fooled with reloading these at the time, as they had problems getting enough of the M48 spotting rifle rounds for training practice, so we handloaded readily available API M8 or APIT M20 bullets pulled out of linked ammo for the M2 machinegun. Cal. .50 BMG primers were hard to get, so we "rechambered" fired spotting rifle cases to accept a 5.56 mm M196 Blank cartridge pressed flush into the base of the case and used this as a booster to ignite 135 grains of pulldown IMR-4895 salvaged from .30-'06 APM2 ammo loaded loose into the rest of the case. They were tedius to load, but worked well.

Years later I used the same idea to light off 1 pounder Hotchkiss rounds, using 5-In-1 .44-40 blackpowder movie blanks as boosters to ignite two Chok- Full-O-Nuts coffee scoops of H-4381 as the main charge. Worked just fine...

I'm not sure the effort is worth the trouble in conventional rifle brass.

raytear
Feb 23rd, 2011

I think Keith mentions the primer tube/duplex/forward ignition stuff in his autobiography, and a few times in his other articles. If you have access to those you could get the definitive answers.

My own summary from memory is that the tests with .50 BMG were done for the government, but ended with the war. There was a measurable gain in accuracy using the system, but, apparently, not enough to justify switching to that system. Especially with the war ending.

There was also some gain in accuracy with smaller, civilian calibers, but, again, the novelty and complexity militated against wide acceptance. Some folks testing the system published articles that claimed pressure increases. I would guess that is a possibility since some of the powder space was taken up by the tube. So, just reduce the powder charge a wee bit!

My own opinion, for what it is worth is that the system makes some sense for single use cartridge cases because of the complications involved in trying to easily decap thru the flash tube for reloading. Also, it does make theoretical sense that igniting the powder charge from the front would reduce erosion from unignited granules scuffing against the leade, etc.,as they are shoved forward by the gas building behind them. I would think the use of powder whose grains were too large to fit down into the tube would be required for consistency of ignition.

Seems like at some point during the late '50s or early '60s you could buy those tubes. Instead of being threaded, they fit thru the flash hole and were flared on the butt end so they could be held in place by the primer itself. I believe I saw them advertised in Guns and Ammo and Shooting Times.

raytear
Feb 23rd, 2011

Wasn't the original .454 Casull--when it was a wildcat and handload only proposition--a triplex load that started with Bullseye over the primer?

That was before I started handloading, but it still sounded like a great opportunity to destroy a custom made firearm and do oneself a real injury!

RicinYakima
Feb 23rd, 2011

I have six references from Keith, but zero load data and zero results data. He just says it works and provides nothing else. Whelen, Hatcher and Narramore also talk about it, but no shooting data.

I have read about the slip in ones also, but can't remember an article written about shooting results?

raytear
Feb 23rd, 2011

My Keith stuff is out on loan at the moment, and my collection is not as extensive as yours, I don't believe. I have no recollection of any load data. Doesn't mean it wasn't there, just that I don't recall it. I have no Hatcher, Whelen, or Narramore in my own library as it is mostly devoted to other subjects.

If I were working with those flash-tubes I would begin with the suggested starting load from Lyman's manual minus, say, 2%-5% of a medium burning rate powder. Higher percentage reduction for a smaller capacity case, e.g. 2% for a .30-06 and 5% for .30-30. (From my experience, a 2%-5% reduction seems about right because whenever I have used Lyman's starting loads in standard set-ups I always get smudging/sooting, often clear back to the body/shoulder junction.)

Then do the standard work up until velocity matches the load results without the tube. Guess I forgot to mention I am assuming having a known standard load with the given powder to use as a baseline for velocity and accuracy comparison.

Anyway, an interesting set of experiments could be done. I think those might be especially fruitful now, given the HUGE number of powders available that were unknown to the gurus of the previous generation or two. Might even turn out that the advances in powder formulation are great enough to overshadow any gains from flash-tubes.

RicinYakima
Feb 23rd, 2011

Keith's only reference to powder is "DuPont's new slow burning" one in 1939, so looking at Sharps's Handloading, I assume it is 4350. Lyman's #48 has data for pressure and velocity with the bullet the case owner wants me to use, Hornady 220 grain. However they use Winchester cases which are almost 30 grains lighter. First loads will be minimum and then check case volume of fired cases.

I have some R-P cases that are only 5 grains lighter than the modified Western cases. We will see how they do with 48.0 grains of IMR 4350, 2% less than Lyman's minimum.

Thomas Trevor
Feb 23rd, 2011

This was written up in the report of the Chief of Ordnance for 1880. Captain Prince constructed several cases for front ignition in the 45-70 Springfield.

This was using black powder and short story, no better no worse.

RicinYakima
Feb 23rd, 2011

I have found references to earlier work done by Springfield Armory, but don't have any. Could you scan any information you have? Send me a PM and I will send you my email. Thanks, Ric

RicinYakima
Feb 27th, 2011

A big Chinook wind blew in today, so I headed for the range. Temperatures were steady at 48 degrees, but wind was blowing 20 - 25 with higher gusts. So I shot loads over the chrony, after tying it down to two cement blocks.

Remington cases averaged 2193 f/s with ES of 22 f/s and SD of 4.71. Western tubed cases averaged 2157 with ES of 38 f/s and SD of 9.71. All of the Western cases had flattening of the primers and one partial head separation. Lyman lists load of 49 grains, one more than I loaded, at 40,700 CUP. The investigation of this is continuing.

Webley
Feb 27th, 2011

I remember reading about the duplex loads in Guns N' Ammo magazine when Keith was still active. I think that the end result was that given newer powders, it was deemed unnecessary, I think by Keith himself. This was the mid to late '70's.

DonH
Mon Feb 28th

My memory concerning this issue pretty much matches with yours Webley. I cannot put a date on just when all experimentation ended but the bulk of the work with front ignition cases and duplex loading by Keith was in the 40s via the OKH connection. I recall reading somewhere that some experimentation was done in an attempt to improve the OKH ctgs. Agree also that they found as much improvement using newer powders eliminating primer tube work and witches-brew powder charges. Like other things from the past, I predict we will see the idea come around again tho maybe in another variation.

jalexander
Mon Feb 28th

I don't think this will be helpful to your project but just for general interest. Just yesterday I was going through some old Precision Shooting magazines from the late 1980s and early 1990s looking for some arcane information I thought I remembered Merrill Martin had discussed and ran into a discussion between Martin and Creighton Audette about some problems with cast bullets involving shock waves damaging the base of cast bullets, the powder being forced down the bore as it burned, incomplete combustion and other things real or imagined. These were uncovered by Martin's microscopic examination of cast bullets caught in his bullet catcher and of poly wads and the surprising damage to both projectiles.

They speculated that forward ignition might be the solution and that gave Audett the chance to pontificate on the military history which has been covered well above. They made a pretty good case that forward ignition would be a superior system for CB loads with a lot of air space. But as have others have, they decided that the difficulty was too much to try.

I will be interested in what you find out. It would also be interesting to see what they would do with a typical CB load since you are going to get to play with them.

RicinYakima
Mar 6th, 2011

Well folks, it is bad news for all. The second loading, of these 1939 vintage, cases has left one with a partial head separation and 8 others with incipient ones. You can feel the deep thinning ahead of the web with a bent paper clip.

So I did shot the accuracy test with the 8 surviving cases from the first test. If you check the 27Feb post you can get the chrony results. Remington group of 8 shots was 2.025" and Western group was 3.136". The Western cases made a 6 shot core group of .732" but two wild flyers that I don't think were my shooting. The Remington group was strong out from 11 to 5 o'clock, and I think just to light of load of IMR 4350 at less than 40,000 CUP.

Now that there is only one shootable case left, there isn't going to be any cast bullet tests. My gut feeling is that unless you could charge the tube with a grain of Bullseye, there is so much heat loss inside the tube, it doesn't make that much difference. But now we will never know unless someone makes new cases.

bsdger45
Mar 6th, 2011

In the March 1944 AR, Fred Ness has an article. Here is the first paragraph...

"Several years ago when the mysterious OKH Duplex loads were first publicized in the shooters' magazines, we published some dope on the flash tubes, or extended flash holes, in the Dope Bag. It created but passing interest, judging from the response at that time. More recently, we mentioned the O'Neal patented load and described its front ignition by flash tube, and this elicited a lively response from several widely seperated sources."

The article goes on for more than a page. My AR indices only go back to 1940. I have all magazines back to 1922. At least I know that there is more material available in these magazines, more reently to and a few years back from March 1944. John

jon skorepa
Mar 28th, 2011

Look up R.E."Rocky" Gibbs' writings about the Gibbs front ignition cartridges. Barnes' Cartridges of the World has an article. Further Google US Patent Offices front ignition 1850 to now. I'll try to post the patent #s for you.

jon skorepa
Mar 28th, 2011

Gibbs book pdf from Cornels Books patent nos 4 149 465 , 2 269 316 ,398 823 ,180 846 ,62 283. Hope this helps. One day I plan to try tubes in 38-56, 45- 70, 45-2.6 to help reduce recoil barrel temperature and fouling, perhaps lower std. deviations.

RicinYakima
Mar 29th, 2011

Good luck on the project. I have sent the cases back to the collector since they were not shootable any more. The idea has potential, but like all engineering problems the devil is in the details. Ric

swifty
Jan 13th, 2013

Ric, I shot at the national matches at Camp Perry in 1974 high power. As luck would have it I shared the firing points and pulled targets for David Tubb. He was shooting a 30-338 using flash tubes, that is all I have ever been involved with them. Obviously he has been experimenting with long range and over the course rifles for a long time and has found better options.-Muddy

RicinYakima
Jan 13th, 2013

Since Tubb, nor anyone else, has used them for 30 years, it is kind of a rabbit trail running off into the woods. My Army demolition training and engineers tell me that you should be able to focus the primer energy at any point you wish inside the case. The main problem is energy (heat) loss inside the tube; and so little energy in a magnum rifle primer. A primary fire charge may be required.

Chargar
Jan 14th, 2013

I recall reading Keith's words about the long flash tube and front ignition of duplex loads. I also remember my feelings at reading those words. I wanted to stay as far away from those things as I could get. I just ain't that curious.

Reg
Jan 14th, 2013

Seems like I remember reading something about these many years ago and it seems as erratic or high pressures were involved somehow. Am thinking now it might have been a proper ignition problem as I don't think magnum primers had come about yet.

To really get an idea of what is going on , one needs pressure reading equipment as well as a good chronograph.

Muddy 22
Apr 2nd, 2014

In 1974 when I was at Camp Perry I shared the firing point and pulled targets with David Tubb. His long range rifle was a 30-338 and he used extended flash tube cases in it. He probably would be the best information for tihs, especially as to accuracy in target grade rifles-Muddy