I have wondered if anyone has seen anything about using Large Rifle Magnum primers in the 50, obviously using an adapter. I have been unable to find anything. There are a few obscure cartridges that use nearly as much powder. The price difference makes it attractive. There are some posts showing the flame produced by the various brands; I would have to find the info, but would obviously use the 'hottest' brand.
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All things considered
Your average LR primer weighs in at 1/2 grain.
Your average 50BMG primer weighs in a 19 grains.
I wouldn't consider attempting to light 225-250 grains of powder w/ a 1/2 grain weight primer not to mention the cup variables between the two.
Keep'em in the X ring,
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I found a post where someone said they had seen a shotgun primer mod for 50BMG that worked, but that was the extent of the info. I have doubts about that because shotguns use small amounts of fast powder at low pressure. The large size of the primer may make people think it's strong, but I doubt it (I'll have to see what I can find). I don't want poor ignition, or worse, a dangerous condition similar to the theories of why small amounts of slow burning powder can result in detonations (i.e. the bullet moves down the barrel, reducing pressure and temperature, causing the powder to nearly stop burning, then the pressure rises and the stuck bullet lets pressure rise dangerously before it moves). I am sure the military over primes to ensure reliable ignition at temperatures of -40, but wanted to know if anyone has already explored this. I have since found references for 577 Tyrannosaur and 700 Nitro Express loads (which use up to 200-250 grains of powder with large rifle primers) of hang fires until they put a couple grains of Bullseye in (no reference wether the loads are compressed to hold it over the primer). I may try to design an insert that holds the primer and a couple grains of a fast powder, since the 50 BMG does not use compressed loads with the available powders. It would have to be reasonably easy to make and reload or it's not worth it. I have done duplex loads with slow powders in 223 and measure the pressure with a Pressure Trace, so it's not totally uncharted territory for me. I also try anything totally new remotely until I am convinced nothing unexpected will happen.
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I would PM Ed Hubble about this. From my understanding he does a special powder mix and voodoo to get it to work on larger cases but I am not sure about the 50 BMG. Better safe than Wyle E. Coyote.
I would almost guess it is not going to work.
We had a hard time getting our 700 NE to ignite properly with large magnum primers.
We solved the problem by using 2-3 grains of Bullseye at the bottom of the case under the powder charge.
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This thread might give you some insight.
Well, I had decided to try using a priming tube similar to artillery shells by drilling/reaming the 50 BMG cases to accept 30-30 cases. Other cases could be used, but 30-30 are common, inexpensive, and rated for a decent pressure (not quite as high as the BMG, but I wouldn't be loading to max pressure). Artillery primer tubes use black powder for a booster, but I'd look at a smokeless booster. Unfortunately, the price of brass has increased significantly, so I purchased regular primers. I'd still like to try the idea just because I like trying interesting things. Elmer Keith tried primer tubes in the 50 and got better results (about 100fps), but not deemed worth the effort. It was used in the 50 spotter M48A1.
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Good idea using 30-30 cases; but please let's stop with the "pressure rating" for cartridge cases. A 30-30 will take 50 K psi; in a bolt action of course. Just because a cartridge is loaded to a certain pressure, doesn't mean the brass is only made to that pressure. Lots of examples. Common misconception.
We use Benite in Tank Ammo primers; (I was a tank ammunition Production manager for AMCCOM, now JMC, once), which I recall is black powder mixed with nitro cellulose.
Anyway, I would use a booster charge of faster burning powder under the 50 BMG powder. How much and what kind, is for you to experiment with.
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I've been shooting .50BMG for @ 23-24 years now (Lord, has it been that long!?!), and not that I know everything, but I'd like to share a couple thoughts on this project if you are interested.
1). Back in the day, many of the .50BMG powders were simply bring-overs from large caliber sporting rounds. Things like Accurate 8700, etc.... were commonly put behind .50 projectiles in the BMG case and besides the inability to get a full case with those powder types, they worked. So, one would have to assume that using those types of powders, or maybe even the ball type of surplus .50BMG powders with a standard large rifle magnum primer would probably have enough flame front to ignite them pretty reliably (especially in a normal temperature environment.
I think you would probably have some great difficulty getting a much slower powder like VV20N29 or even VV29N41, or H50BMG to light reliably with just a large rifle primer (without a "booster" of course).
2). The difference in primer cup thickness and hardness would be a concern to me. The standard BMG firing pin is a much larger diameter and the firing pin spring is made to deform a much thicker/harder primer cup material than a large rifle primer is meant to be hit by. So, I would also consider adjusting the firing pin travel (assuming you have a bolt action gun?) and if possible, reducing the spring pressure on the firing pin so you do not get an unintentional piercing of the large rifle primer cup.
3). Machining in a smaller caliber case into a BMG one and achieving a primer tube similar to the one the .50BAT round has in not a bad idea. Frankly, even if you don't load the smaller case with a different "booster" compound/faster smokeless powder like they would for artillery, confining the flame front of the large rifle primer to a smaller portion of even the same/slower .50BMG powder, should increase the probability of reliable ignition. Let's face it, if you can get even just 20 grains of BMG powder to fully ignite inside the make-shift primer tube, the rest of the 180-200-some grains of that powder is not going to have a hard time being lit very far behind it. See #4.
4). Since even slower .50 powders are not anywhere as slow as "artillery" propellants (save of course 20mm & 30mm variants which I personally don't lump into the term "artillery", even though they technically may be considered as such), I honestly am not sure if a "booster" of a faster burning smokeless powder will be necessary, especially if you fabricate a primer-tube type of insert. if you do decide to use a booster of this type, I surely wouldn't make it any more than just a couple grains, for fear of making a flame front that dramatically exceeds the normal .50BMG primer type. That could be a very bad thing too!
Back in the day, guys used to retro-fit .50BMG primers to REAL artillery shells (not just 20-30mm, even 40mm BOFORS and larger I believe) and I understand they worked pretty well for them.
Keep us informed of how it all goes.
Are you an FCSA member?
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I recall Elmer Keith writings about that way back in the day. He called them "Duplex" rounds with a tube, that I assumed was filled with pistol powder, but he didn't really elaborate on that point, focusing instead on the idea of igniting the powder charge from the front rather than the rear.
There may be some merit to the approach of a hotter ignition flame. My own pressure traces of factory XM33 show this:
Note the time that it takes before pressures ramp up after the primer discharges and the time before pressure starts to rise in a serious way. It varies a lot, yet peak pressures and ballistic results are not bad at all.
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testa virtus magna minimum
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Old Mopar man is right about the 30-30 cases. Cases are basically gaskets, if they are properly supported by the chamber, that is not a sloppy fit, they can withstand a lot of pressure. Notice how tightly 454 Casull chambers are.
Now I've been shooting the so called cannon surplus powders for more years then I care to admit. Powder like 860, 870, 8700, 867, 872, 5010, etc. I use them in all sorts of cases even very small cases like the 5.56 with excellent results. In my 308 I use 867 with a 4198 booster and can approximate the burning rate of 4350. In fact looking in reloading manuals the total grains of my booster and main charge are equal to the grains of 4350 in the manual. This is a very economical way to be able to shoot a lot and is safe. I make sure my booster and main charge fill the case so that in moving them about the two charges don't mix. With the smaller cases my booster powders are Unique and Red Dot. Sometimes HP38.
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Rocky Gibbs original wildcats use a copper tube soldered into the case for front ignition, similar to what Kieth tried. I always wanted to try it but never did, it would be interesting to crono to see if it really made much difference
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