"I experimented with John Buhmiller's double primer load"
Retrieved: 08/23/2016
Last Post: 02/06/2010
Has anyone used this method of adding a second primer face down on a compressed load in straight walled cases? What's up with this?
9.3x57
07/11/09
Quote:
Why would one wish to do such a thing?
Buhmiller wrote that he had some troubles getting all powder in the case to burn in the very large wildcats he developed. The addition of the extra primer solved that problem. If I remember correctly he charged the case as normal and dropped an extra primer on top of the powder and then merely seated the bullet on top.
He didn't report any pressure problems but did work up loads for a variety of wildcat cartridges which in those days meant "no data available". He didn't shy away from a guess.
I certainly understand the sentiments of some who think such actions are irresponsible, ridiculous, etc, but for those of us that are happy to develop loads with non-canister military surplus powders and thus never do have any idea what our true pressures are or other such experiments, such fixes don't seem so absurd.
Naturally, I cannot recommend it.
Daryl_S
07/11/09
The reason John B. developed the double primer system was to aid ignition in straight cases with compressed loads. The system works as designed.
Yes - I have used them in the .458 2" to aid the igntion of the Fed 215's and CCI 250's normally used in the primer pocket. I found a standard primer underneath the bullet added ignition to the point of allowing a reduction of 8 gr. of powder. Prior, it took 68.0gr. of H335 to get 2,290fps in my .458 2" Mauser, but with John's 'extra' primer, 60gr. gave the same velocity. Just in case you think 68gr. is too much for a 350gr. in the 2" case, I used that powder charge with all bullet weights, 350Hornady at 2,290fps, 400gr. Barnes @ 2,160fps, and 500gr. Hornady @ 2,050fps.
So - I only used the double primer as an experiment with the lighter, lower pressure load (350gr.) and only as a test. It would have been more useful with heavier bullets in cases of limited capacity, like the 2" .458. Since I was able to beat 2,000fps with normal 24" drop tube loading with both H335 (68.0gr.) and IMR 4320(66.0gr.) and 500gr. to 510gr.'ers, I elected not to use the double primer in them.
grandveneur
07/11/09
The idea is not irresponsible or ridiculous, but a booster load! The problem are the shells and the load, normally a very fast burning "solid" powder. Look at experimental cartridges without shells for example!
xausa
07/11/09
Elmer Keith experimented with primer tubes which went from the flash hole to the top of the powder column in an effort to improve combustion of large charges of slow burning powder. I believe he got the idea from a system used in some fixed type artillery ammunition (as opposed to the large naval guns, which used bags of powder loaded directly into the breech behind the shell.) I don't believe they worked very well and must have been a real bitch to reload. Buhmiller's method seems much simpler and streightforward, as was the case with most of his ideas, such as the bullpup stock design for long range rifle shooting.
Omnivorous_Bob
07/11/09
I think the dual primers is an interesting idea but unknown territory. I'm speculating, but a few grains of unique under the main charge would probably accomplish the same aim. It would be very interesting to test that out in a pressure gun!
xausa
07/11/09
I was present in the shop of a gunsmith friend of mine when a man brought a thoroughly demolished SMLE. He said that he had heard of the benefits of handloading ammunition and had set about loading some .303 ammunition for his rifle himself. Not having access to commercial smokeless powder, he had emptied the powder out of a number of rounds of .30-'06 blank cartridges, and used a caseful for his first shot.
Amazingly, he was uninjured, and the SMLE action was intact, despite the stock and barrel being totally destroyed. When one reflects that blank powder was the same material used to fill World War II hand grenades, our amazement was understandable and justified.
I submit that filling the case with gasoline would have been far less dangerous.
My opinion of the strength of the SMLE action rose considerably.
Bramble
07/11/09
I don't think that the second loose primer increases the velocity because it aids ignition, simply that the power generated by the combustion of the very volitile primer compound in the second primer is much greater than it would be if that volume of case capacity were occupied with powder.
I have never measured the pressure produced by a primer alone, but given some of the large velocity differences one can get simply by changing primer brands or types it must be substantial.
Without some very sophisticated gear all one could decide was that the velocity went up with the loose primer -v- without it. To what this could be attributed would be a suposition.
Elmers experiments were somewhat different as he was only lighting the powder from the front, not from both ends.
As I see these experiments if one were to suceed in promoting a burn from both ends (and I don't think that this does) then one has two flame and pressure paths in direct contradiction to one another there are all sorts of reasons that this is not a good idea.
The other thing that would bother me is the primer migrating. If one loads the cartridge and fires it immediatly then it is probably where it was put. After a few days as cartridge 2 or 3 in a mag then the primer could be anywhere in the charge, including cup down on the flash hole. That could be interesting.
Tatume
07/11/09
Quote:
Without some very sophisticated gear all one could decide was that the
velocity went up with the loose primer -v- without it. To what this could be
attributed would be a supposition.
Exactly so. The gun magazines are full of unsubstantiated hypotheses presented as facts. In my studies one thing I have come to realize is that ideas that "just make sense" often don't.
9.3x57
07/11/09
Quote:
The other thing that would bother me is the primer migrating.
I've wondered about this, too.
If one loads the cartridge and fires it immediatly then it is proberbly where it was put. After a few days as cartridge 2 or 3 in a mag then the primer could be anywhere in the charge, including cup down on the flash hole. That could be interesting.
A round subjected to months of banging and bouncing around in the rig and then having a few shots fired over it in the mag might allow a bit of shifting. Whether it matters, who knows. I think it would make an interesting experiment to load ten or so with the extra primer on top, ten in the middle and ten next to the seated primer on the bottom. Shot thru a pressure gun over a chronograph would be best but the results even of mere chrono testing would be interesting.
As far as the need for adherence to exact scientific method is concerned, I guess I don't much care if it is safe and works, that is, solves a problem and gets the job done.
We all have our lines in the sand. I absolutely will not any longer use any fillers except for firm wad coulumns in rifle rounds but have no problem using milsurp powders the pressures of which are unknown to me, tho the rounds function safely in my guns. As for Buhmiller's extra primer, I guess if it cleaned up the extra powder kernels and didn't show signs of excess pressure, I'd use it. Others might not, and that's ok too. Funny, I would never use a fast burning powder on top of the main charge. We all have our comfort zones I guess. Modern powders probably obviate any need for Buhmillers "Solution" though.
Tatume
07/11/09
Quote:
As far as the need for adherence to exact scientific method is concerned, I
guess I don't much care if it is safe and works, that is, solves a problem and
gets the job done.
The point is attribution of cause. If the problem is solved and the result is satisfactory, that is fine. But when a claim is made about the physical mechanism by which the effect was caused, more information is often required than is at hand.
As an example, consider the claim that a powder column "burns like a match, from one end to the other." The pressure of the load could be measured, and the exit speed of the bullet could be measured, but the claim is completely unsubstantiated. Yet, it is repeated and held forth as fact time and time again. It "just makes sense." It may be true, but it is not demonstrably true.
Daryl_S
07/12/09
As to migration - try filling a 2" .458 case with 60gr. of H335, then seating a 350gr. Hornady to the cannelure. You will see that migration isn't a problem. We're talking about heavily compressed loads - both that ctg. I used and the gun were certainly up to the task. The barrel was retired after 15,000+ rounds through it - many of them with home made bullets to 560gr. - shortened .303 brass, annealed and drawn '06 and .250 Savage cases for the bullet jackets. Interesting stuff.
As with all handloading, one must start conservatively - there is/was no danger in my testing, which is why/how I found 8 gr. less to give identical results. Yes - pressure was higher than without the extra primer - which showed up in the increased velocity. Pressure seemed normal however and the same as the full charge of 68gr. - which was mild considering that same 68gr. charge was used with 510gr. Winchester Solids @ 2,050fps as well. I just never got around to experimenting with dual primers with the heavy bullets, the extra 8 gr. of powder being cheaper than adding an extra primer. That 2,050fps was virtualy identical to what Speer chronographed factory .458 mags from a Ruger #1 at that time - mid 1970's, Speer #7, I think it was listed in. Seems to me that's what .470 Nitro gets with it's 500gr. bullets and what a .450/.400 gets with it's 400gr.'er. My little 2" .458, with 22" bl. was a wonder in itself! Never, ever expanded a primer pocket nor lost a case for any other reason - in 15,000 rounds. The 'key' to safe pressure is brass longevity.
As to adding unique or some other easily ignited 'booster', I didn't get around to testing that - which is amazing, considering what 'other' stuff I did experiment with.
404bearslayer
07/12/09
There is another 'experimental' method that I would consider a bit more predictable as the double-primer method. As it is experimental, I do of course not recommend it, and present it for stimulatung thought only .
Mixing two RELATED powders, taking advantage of their respective properties (benchresters do this quite often):
Take a .470 NE. RL-15 ignites fast and burns off efficiently enough (nearly 100 % with a 88 grain load giving appr. 2100 f/s to avoid muzzle flash in a 24' barrel. That load would end up with under 90 % load density however, and you would want to avoid anything less then 95 %, especially in a long case. RL-22, with reasonable pressure at same speed and a compressed load of 108 % (possible when using a 'drop tube' while filling the case) WILL ignite well at this level of compression but will leave you with a lot of unburnt powder at the muzzle, hence big muzzle flash and a bit of extra recoil from 'rocket effect'. By carefully subtituting a certain percentage of one powder with the other, mixing, and inceasing the mix step bay step while observing velocity and pressure curve, you will be able to arrive at a new powder property that matches your requirement better then the single components. Stay in any event away from powders that are already 'hybrid', like Norma URP or R-17. These are generally not feasable for DG calibers as they need high pressure to work in a predictable way. Using the Quickload reloading software will show you where each powders weaknesses are in respect to case capacity, pressure etc, pointing you towards how you want to mix. The best way is to approach your end-mix in small steps, kind of like regular load development and to measure not only velocity, but pressure. RSI 'Pressure Trace', for example, can measure the pressure curve of your loads by simply attaching a temporary strain gauge to your barrel. Not only do you get peak pressure, but you can also observe the pressure curve on your laptop screen. Using this system, you can adjust the mix until you do not anymore observe 'tail-end' spikes at the end of the pressure, indicative of bad ignition.
As the purpose of this method, as well as the double primer system, is smooth ignition, you can even use Pressure trace beforehand to see whether there is a problem at all, and how serious it actually is. By running tests with Pressure Trace, you may learn that all you actually need is: a heavier bullet, a tighter neck, a strong crimp, or moving the bullets ogive closer to the lands (jamming is not an option for a hunting rifle, but moving the ogive to about 1.5 mm to the lands will not give you problems, but work similar to jamming - INITIAL pressure will be higher),
cooch
07/13/09
Quote:
Elmer Keith experimented with primer tubes
IIRC, Keith was experimenting with .50 BMG.
His intention was to initiate combustion at the front of the case, rather than the rear. He expected this to cause the powder to burn more in situ, rather than in the barrel. He did report increased velocities for standard pressures, but I can imagine that the cost and complexity of the manufacturing process was not welcomed at that stage of WW2.
Now you have me curious. I must check.
[edit]
OK. Charley O'Neil created the first "duplex" rounds at Keith's suggestion. That were working on .22 and .25 wildcats based on the .30 Newton case. The barrels were heating excessively, and Keith wanted a way to burn the powder in the case/chamber, rather than in the barrel.
During the war, Keith experimented with the duplex (tube) loadings in .50BMG.
He reported-
Reduced muzzle-flash.
Longer barrel-time pressure curve.
Uniform pressures.
Burning an extra 18 grains (7.5%) of powder and achieving an extra 200fps velocity, at standard pressures.
Reduced recoil.
The problem was in the manufacturing of the rounds under wartime conditions. Sometimes "good enough" is good enough.
Bramble
07/13/09
EK also goes on the say in his writings in "Hell I was there" (1) that during these experiments in order to preserve security (being wartime) that they released FALSE information that they were experimenting with mixing powders.
He says that this made the pages of "American Rifleman" and that many guns were blown up by people trying this stunt.
(1) "Hell I was there" Pg 177
Paul
07/13/09
Not that I would want to try it, but Keith's duplex loads may have got him somewhere. As I recall he was able to get velocities from the 333 OKH nearly as high as we expect from the 338 Winchester Magnum.
Daryl_S
07/13/09
Same with his lady's .280 DuBiel if memory allows - very high velocties, low pressure and good case longevity.
Difficult loading, or course, as the tube had to remain clear of powder I think.
Some people thought he was mixing powders due to the name, 'Duplex'.
The first .454 Casulls actually had real duplex (and triplex) loading, with up to '3' different powders used. Some guns wrecked as a result of people mixing their own recipes - apparently. I've even seen receipes in print, up to 3 layers of powder - something I'm not prepared to do.
I's used duplex loading my BP ctg guns - FFFG 'starter' with 1F for the main charge as well as some pistol and rifle powders used as up to 14% of the load of black sdepending on the calibre - but that's as far as I'm willing to go with 'duplex' loading and I've found other methods that make for clean shooting loads using straight BP - no mixes.
9.3x57
07/13/09
I believe some artillery round use the primer tube and maybe that is where Elmer got the idea?
jgrabow
07/13/09
Crushing a primer on top of a full case of powder. What are the chances of the primer going bang as you're seating the bullet.
Daryl_S
07/14/09
Jim - never happened during my testing - not as much "Crushing" going on as you might visualize.
cooch
07/15/09
"...we fired ten or fifteen shots through the thing one day and I actually put a cigarette on it and it started to smoke.
I told Charley 'We are firing the powder at the wrong end.'
He said 'What do you mean?'
'Well', I said 'if we could ignite the front end of that charge, and start the buillet up the bore with a portion of it,then the pressure that drove the bullet forward would hold the powder back in the case until the fire came back and it was all consumed...'
I could see no way of accomplishing this, but I gave Charley the idea..."
Direct quote from Hell, I was there" page 177.
Keith did not publish his method (although they applkied for, and got, a patent) only the results. It was another writer who wrote that Keith was mixing powders... which is probably the origin of the term "Duplex".
Keith also specifically says that he did not publish the method, because he didn't want the Germans to use it and boost the velocity on their artillery.
So there we have it.
Keith came up with the principle.
O'Neil first put it into practice.
Keith believed that the principle was not, in fact, being used in the artillery of the day.
Incidentally, the two anti-tank rounds from that era (2Pdr) in my possession have primer tubes which are closed on the end, and perforated on the sides.
bigfoot
10/24/09
It was mentioned early in this thread that you could achieve the same/similar MV with less powder using this method. These days of reloading component shortages and increased cost of components, I'm thinking most primers cost a bit more than a few grains of powder; powder is generally easier to come by than some primers.
My other concern is what damage that extra primer is doing to the inside of the barrel as it zooms through, in most cases, a considerably larger diameter bore. Thin and light as that primer jacket is, it's still probably gonna ding up the rifling somewhat.
Daryl_S
10/25/09
Out of the 15,000 rounds I put through that particular .458 2", perhaps only 1,000 were double primed - no damage was expected and not occured. It was still shooting sub 1 1/2" groups with all bullet weights when I retired the barrel. It had been on three actions during it's 'life' and had too many dovetails to suit me, thus was retired, not because it stopped shooting like a varmint rifle.
Riflemanusmc
02/04/10
The BEST info on flash tubes was done by Rocky Gibbs. Good information and very straight forward. His point was "Start the fire at the front". One thing you'll notice is that when you eject the case, its HOT. Otherwise unknown for a boltgun. The point is less barrel wear from rear ignition and pushing raw powder into the barrel. I have the book copied if anyone would like it. Just email me.
Daryl_S
02/05/10
The flash-tube idea was used in some military rounds, which system Elmer Keith tried in some of the wildcats he was shooting. The .280 DuBiel comes to mind, Loraine's rifle. He/they called it Duplex Loading.
The double primer used by Johm Buhmiller was in straight cased .45 and .50's to help burn the powder. John, to the best of my knowledge, didn't use the tubes as they take up needed powder space in the straight cases. He didn't have the powders then, that we have today, and with the straight cases, was looking for a way to get better burning of the charge. In a way, it was similar in idea, but without the tube.
I experimented with his double primer system back in the 80's, with the loose primer sitting cup-down on top of the charge under the bullet and lightly compressed in my .458 2". I was able to cut the charge 5 to 8gr. and still recorded the same velocities as without it. Using the double primer system, I obtained 2,290fps with 350gr. RN's in my .458 2" Mauser with 60gr. of H335 as opposed to 68.0 for the same velcoity with normal loading. The presures for this load weren't very high as I used the same powder charge with up to 510gr. WWSolids and softs, for 2,059fps.