Duplex loads using 50 BMG Powder?

[DonMountain]

I have 2, 8 pound kegs of 50 BMG powder that I bought 20 years ago to use in a 50 BMG rifle I had then. I have tried it in a 338 Win Mag with heavy J-bullets and never gained much accuracy. Having converted most of my reloading to cast lead boolets over the years, I was wondering if anybody has tried duplex loads using a fast pistol power like maybe Red Dot under a slow powder like 50 BMG powder using typical lead boolet weights in old military rifles like 30-06, 308, 303 British, 7.65 Argentine, 7.5 Swiss, 8MM Mauser and etc.? Could anybody offer any guidelines if they have? Or a reason to think its not a good idea?

[rockrat]

I think I remember a posting about doing just that. I believe the person used a couple of grains of 4227 as a "booster charge" over 860 powder. I am sure those that have, will post here. If you do a search, you might find the posts.

[Sgtonory]

I have had good results useing WC 870 with 5 grains of longshot as a booster in 308 win. With a Lee 312 185 cast. Accuracy at 30 yards was fine for me. This was shot out of a M1A cycled the gun find. But have also used any pistol powder that works well under compression. Red dot also worked well. I would start low on booster and work up.

[rbuck351]

I have been using H5010 with a booster of several different pistol/shotgun powders. Unique,red dot, AA9 all seem to work about the same. I fill a case up to the base of where a boolit will be and weigh the charge and fire a couple to make sure I'm not getting high pressure. Mostly it barely burns. Then load 4 or 5 grs less 5010 over 4 or 5grs of booster. Start lower with small cases like 30/30 then add more and more booster charge until the burn cleans up. I usually max out the booster at about 7 to 9 grs depending on case size. It is possible to go overboard with the booster as 9grs of red dot will build fair pressure without the 5010 in the case so work up slow.

[SOFMatchstaff]

I just tested a WC860 load in the in the 405 win, 57grs, with a 3gr booster of 800x, 1700fps and 2" at 50yd with a 325gr FB cast, and a .035 card mildly compressed, still a bit of unburned powder in the barrel and case. The WC872 at 60gr did about the same but at 1500fps. Both load velocitys had a very small extreme spread, 11fps for 10rds. I think the accuracy would be better if my eyes and open sights got along better, but no scope on the 1895 Win, aint gonna happen....

I'm going to bump up the booster a couple gains and see if that cleans up the burn, If not I may go to a faster powder like Red Dot. No pressure indications of any kind and the recoil is mild.

[Screwbolts]

OP, It might help if you would/could narrow down the field some as to which one of the many powders suitable for use in 50BMG you actually have.

Ken

[DonMountain]

OP, It might help if you would/could narrow down the field some as to which one of the many powders suitable for use in 50BMG you actually have.

Ken

I have Thunderbird T5070, and River Valley Ordnance RVO-57, and was planning to use RED DOT or Alliant PROMO as a primer.

[MUSTANG]

Here is some work ups I posted in the past on duplexing WC860 & WC872 50BMG/20mm Vulcan Powders

Some tested loads in .223/5.56 using WC872:
http://castboolits.gunloads.com/show...92s&highlight=

Some tested loads in .223/5.56 using WC860:
http://castboolits.gunloads.com/show...But&highlight=


Some tested loads in M1a using WC860:
http://castboolits.gunloads.com/showthread.php?169370-WC860-in-M1a&highlight=



In the past I also posted some pdf's of TCCI load data sheets from several years ago that might be of interest/utility. See the following link.
http://castboolits.gunloads.com/show...ets&highlight=

[Screwbolts]

OP, Thank you for listing them, I used the last of my RVO-57 some years ago, at the time I got the RVO, it came with duplexing info. If you still have any of the original paper work RVO sent with their powder, you may have their recommended duplex loadings for many calibers.

Ken

[DonMountain]

OP, Thank you for listing them, I used the last of my RVO-57 some years ago, at the time I got the RVO, it came with duplexing info. If you still have any of the original paper work RVO sent with their powder, you may have their recommended duplex loadings for many calibers.

Ken

I do have some of their reloading data sheets, but none with duplex loads. I originally bought the powder for a 50 BMG and they just happened to send along loading sheets for a 338 WIN mag that I also have. But unfortunately it didn't work very well in that round either. Giving me very erratic results. So maybe it needs a "primer" powder in the 338 WIN mag also?

[Bjornb]

I recently did quite a bit of testing with duplex loads in 30 cal. rifles. My 2 cartridges were 30XCB (30x57, powder volume halfway between .308Win. and 30-06), and .308 Winchester. Twist rates were 1:14 in the 30XCB and 1:12 in the 308.

My milsurp powder was WC860, which was too slow by itself to get a good burn. I tried the following boosters: Promo, Bullseye, Unique, (each with .3cc under a compressed caseful of 860), IMR4227 and IMR4198, each with .5cc booster.

I shot the 165gr. Accurate XCB bullet cast from Lyman #2, Lyman GCs and White Label 2700+ lube.

The loads with the IMR4227 stood out immediately, they gave me 2350 fps in the 30XCB and 2200 fps in the 308. XCB groups were about 1.5 inches at 100 yards. 308 groups were not quite as good, but reducing the booster to .3cc reduced the velocity to about 2100 fps and gave the same 1.5 MOA accuracy.

I loaded and shot these 2 loads on 5 different occasions, and the results varied very little. I would be confident taking these 2 duplex loads to the woods come hunting season.

[Screwbolts]

My RVO data listed unique as a booster. As Bjornb pointed out there are many good prospects for boosters. If IMR 4227 is showing promise, then I believe I will also be trying RE7.

OT, H4227, IMR4227 and Re7 are all very good in Smokeless MLs, because they don't require high pressure for complete/consistent burn. That may be the ticket to light the supper slow powders available for the big BMG case. I have surplus, 5010, 860, 872 now.

Ken

[DonMountain]

Is everybody using standard primers or magnum primers with these loads of 50 BMG powder over a fast booster duplex load? And for the folks giving loads measured in cc's, could you also give me the booster loads used in grains? I don't have a clue what .3cc or .5cc of IMR4227 weighs? I don't have any IMR4227 to measure out and weigh.

[Bjornb]

Don,
All my duplex shooting was done using standard Winchester LR primers. And with 4227, .3cc and .5cc weighs respectively very close to 3 and 5 grains. I just got used to using those little Lee dippers for expediency.

[MUSTANG]

Don:

All of the loads I tested used CCI standard small and large rifle primers.

[DonMountain]

Well, I did a few experimental duplex loads today. Started out with 46.0 grains of T5070 (all that would fit in the case), Lake City 13 brass, CCI 250 Large Rifle Magnum primers with an RCBS 30-180SP gas checked boolet. Three of them were in a 12" circle on the target at 75 yards and the primers showed no flattening with much rounded edges, indicating a low pressure load. A bunch of unburned powder was left in the barrel. The second load with everything the same except for 3.0 grains of PROMO primer powder placed in the case first and 43.0 grains of T5070 on top. The fit in the case was tight with compressed powder. The primers were more flattened than before, but still a little rounded. And only a little unburned powder in the barrel. The target pattern was smaller, down to 9" diameter. So now I am going to try increasing the PROMO primer powder to 3.5 grains, and reducing the T5070 by 2.0 grains to improve fit in the case. And maybe eliminate all unburned powder and improve the pattern on the target. The rifle I am using is one of those converted 7mm Spanish Mauser rifles to 7.62 NATO. Sites aren't very good. But I am hoping it will do well enough to kill a deer.

[jonp]

Nobade was a big help to me when I bought a bunch of surplus from Don Bartlett to try duplexing 35 Whelen and 45-70.

I'm surprised you started off by reducing the powder 3gr and replacing it with a 3gr kicker. All I have read indicates to start with a 1:1 replacement. You might also try a different kicker powder. I think the point is to get right to where the powder cleans up and then stop as pressures can become radical and unpredictable.

Be very careful with this and all care should be taken to not mix the kicker and primary powders.

[MUSTANG]

My observations are that as you move up the quantity of "Booster Charge" the volume of "Cannon Powder" (WC872, WC870, WC860, T5070, etc...) will change at a slightly different volume due to differences in physical volumes per grain of weight. The important aspect is to have a slight amount of compression for the "Duplex" loaded round. This is to ensure that powder do not migrate together, and to ensure there is a consistent pressure from round to round, although the burn curve will vary as the fast powder ignites, and then the slow powder ignites in each shot.

As a loader slowly incrementally moves the "Booster" charge up 0.5 to 1.0 grains in load testing, they will see incremental increases in velocity (irregardless of caliber/case capacity). Duplex Load development must always start at a low booster charge and move up in small steps for test/load development groups. This is due to multiple events occurring: (1) velocities and pressures increase with each incremental increase in "Booster Charge", accuracy will improve to a certain point- then drop off along the way for the particular boolit/bullet chosen, (3) Unburned powder granules will go from many - to few - to none.

WARNING - ENSURE THERE ARE NO DOUBLE CHARGES FOR BOOSTERS!!! JUST AS IN FAST BURNING POWDERS IN PISTOL LOADS, DOUBLE BOOSTER CHARGES ARE DANGEROUS. The good news is that a double charged booster would usually result in excess "Cannon Powder" spilling over the case mouth if loads are all "Slightly Compressed"; a visual indicator of a double booster charge/obstruction in the brass case/or mixed volumes for cases.

As a general statement; I have observed that a booster charge of 7% to 10% is where full powder burn is achieved, and the range for best accuracy is achieved. In the 10% to 13% range is where I have observed flattening of primers may begin to occur. Slow & incremental increases, coupled with careful record keeping are important to developing Duplex loads.

Change any component and you will need to go back to ground level and begin load development again. In particular if you change from a commercial brass case (i.e. RP, Winchester, etc..) to a military case such as LC you will see a visible difference in powder position in the case - perhaps even spilling over the case mouth since the LC is thicker and has less internal capacity.

I have standardized on CCI #41 primers for small rifle applications, and CCI #200 for Large Rifle applications - Should I switch to another brand or another type of CCI Primer I would need to go back and redevelop my loads.

[rupe01]

rbuck351's post exactly mirrors my own duplex experiences.....excellent advice.

[Blackwater]

This subject was dealt with some years ago when it was almost cheap enough to use as fertilizer, and some got quite gratifying results. Like any such "wildcatting" type proceedures, it calls for a lot of judgement in selecting and using the "igniter" charges of faster powders, but the more able and knowledgeable ones got some great results with it. If you want to try it, use the search feature and you should be able to turn up quite a pile of info on it that should be of great help. After all, no sense in plowing new ground when someone else has already been there and done it all before. Just a FWIW.