IMR 7383 duplex?

[Tatume]

Hello Folks,

The reason I've not heard of anybody using this powder in duplex loads is probably because it's not safe. Or maybe I just missed the conversations. I want to ask anyway. What do you know about duplex loads using IMR 7383?

Thanks, Tom

[Nobade]

I wouldn't try that. That powder gets really peaky past a certain point, and it would be easy to drive it past that point with a kicker charge. Personally the only smokeless powder I would consider duplex loading is the really slow ball powders, and then only in cartridges where they can't possibly generate enough pressure on their own to work properly. My 2 cents.

-Nobade

[singleshot]

So, how about with a 500 S&W mag rifle...hypothetically? :-)

[madsenshooter]

Id go along with it not likely being safe. One has to be careful with kickers, period. I tried lighting a caseful of WC860 with 10B101 as the kicker. Because 10B doesn't like compression, I had nice pressure ring, only where the 10B would have been sitting. Burns Blue Dot speed as long as it is unrestrained, but quickly gets faster and produces higher pressure if compressed.

[Tatume]

I wouldn't try that. That powder gets really peaky past a certain point, and it would be easy to drive it past that point with a kicker charge. Personally the only smokeless powder I would consider duplex loading is the really slow ball powders, and then only in cartridges where they can't possibly generate enough pressure on their own to work properly. My 2 cents.

That's pretty much what I thought. I only asked because I have a lot of it and I'm tired of blowing all the unburned granules out of my 45-70 barrel. :-) It shoots well though, and generates solid high-end black powder speeds.

[redneckdan]

I was wondering how your duplex 10b101 experiments turned out. Got busy last couple years and drifted away.


7383 is like that crazy girl friend you had in college. All fun and games until you come home and she is waiting in the kitchen with a steak knife...:target_smiley:


Seriously though, it's a triple based powder. The fine edge between enough pressure for clean burn and blown up action is razor thin...like less than a few grains in a magnum case.

[Tatume]

7383 is like that crazy girl friend you had in college. All fun and games until you come home and she is waiting in the kitchen with a steak knife

:-) She's unforgettable though.

[evan price]

My very first reloading I ever did was with the 8mm Mauser, using surplus primed berdan cases, pulldown military bullets and 7383 from a paper bag. Filled the cases with powder, set the bullet with a wood mallet.... Didn't know a darn thing about reloading then. Had lots and lots of unburnt powder and carbon and smoke. An old timer gave me some advice, which was to use a kicker of 3031 and then fill with my slow old surplus powder. Glad that those old $50 Turk Mausers were strong actions. I never did get in any trouble, but I will never again try duplex loading and I consider myself lucky to get out with a forehead intact, now that I know what I didn't then.

[41mag]

That powder gets really peaky past a certain point,

Yeppers it does. Also when you compress it just enough as well.

I have a greener back yard due to those reasons right now. I poured out just about 7# of it last Monday and got it all rained in that night.

Simply wasn't something I wanted to mess with and nobody I knew close by wanted to either.

Now on to the 860 and 872 and see where those take me....

[Maven]

41mag, Lots of information on this site's archives and Castpics about WC 860 & WC 872. They're really quite tame compared to IMR 7383.

[41mag]

41mag, Lots of information on this site's archives and Castpics about WC 860 & WC 872. They're really quite tame compared to IMR 7383.

Yes sir they are. I have dabbled with them a tiny bit in standard calibers, but they were purchased for a custom wildcat I had built several years back now. I haven't shot that one in a while, but since I do have several jugs of each sitting there needing to be used up in something.

The 7383 was picked up simply to try out, and for the price I don't really mind where it ended up. Since the rifles I had planned on using it in were 03A3's those little perks with pressure were simply more than I wanted to deal with. If I were simply down to nothing else and had to use it, maybe so, but I have 8+ pounds of H4895 that works a WHOLE lot better with them, and everything else for that matter.

[cowboybart]

I have used it with some success. I used it in 270 & 6.5 WSM, 7 mag, 260 and 6.5-06 (haven't fired these yet). I didn't chrono anything but had good accuracy - exceptional accuracy in the 260. I either used CCI #34 primers or Rem 9.5 M primers.

I used 85% of IMR 4831 data as starting loads. Mine is the RAD78 lot

[Patricklaw]

I just posted on another 7383 thread and I'm really curious about this one. Looking back on this thread, I see the replies in two groups: 1) Ooooo, sounds really dangerous. Don't try that at home, and 2) One person who says essentially, "did it, worked fine, too scared to try again." Anybody actually blown something up with this? I really don't want to be Captain Kirk, "boldly going where no man has gone before." but I can't help but wondering if we've got ten spies telling us, "there's giants in the land." Anybody?

[Bullshop]

I duplexed it in a 22/250 with a 65gn boolit. First kicker tried was trail boss. Second was Alliant Steel. Third was IMR 4895.
No pressure issues at all. Max velocity was 3200 fps. I didn't get the accuracy I was looking for so gave it up.
Everything seemed to go normally and predictably in this application.
In a 308 Win with boolits from 200 to 220gn 7383 has given excellent accuracy with 100% density loads and no indications of abnormal pressure. Velocity was about 2000 fps with the 220gn and 2150 with the 200gn with the same charge weight. Without checking to be sure I am fairly certain the charge was 41.5gn. Not duplexing in the 308 but just mentioning my fondness for the powder in this application.

[Nobade]

I just posted on another 7383 thread and I'm really curious about this one. Looking back on this thread, I see the replies in two groups: 1) Ooooo, sounds really dangerous. Don't try that at home, and 2) One person who says essentially, "did it, worked fine, too scared to try again." Anybody actually blown something up with this? I really don't want to be Captain Kirk, "boldly going where no man has gone before." but I can't help but wondering if we've got ten spies telling us, "there's giants in the land." Anybody?

OK, I'll admit, I did once have an "interesting" experience with it. Worked up loads in a .243 with 95gr. J-word bullets in WV during cool weather. It was about max there. Then brought it out to NM and fired one during the summer, 95 deg. or more. It popped the cork - you could almost drop a shotgun primer in the fired case once I got the action open. Evidently it is a bit heat sensitive.

You can also overload a 260 with it, using heavy 144gr. bullets. Just barely, but a compressed load will produce very sticky bolt lift and cases that will allow the primers to fall out. Anything with a bigger bore than 6.5mm I have not been able to overload. Haven't tried it in an Ultramag yet though...

-Nobade

[MT Gianni]

Old lot from 03, I loaded to a slightly compressed level in 35 Whelen with a 250 gr jsp. It was safe by both 4064 and 4831 powders which were a comparison. I stuck the bolt and coppered the bore first shot on an 80 degree day. Took a week of hoppes soaks nightly to get to where you saw blue rather than copper at a glance down the bore. I found decent groups with the 356 and cast the 351 Saeco did OK. If someone wants the 12 pages of notes send me an email and I will send what I have. On the old shooters board there were 2 blow ups and several stuck bolts.

[Bullshop]

I wonder if the old lot from 03 is the same as current supply?
Jeff seems liberal with his labeling some times. I bought two different lot of WC 846 from him. The two purchases were separated by maybe 10 years. The different lots had a different appearance (color) and quite a wide spread in burn rate.
I had developed a favorite load for a 45/70 with the first lot that pushed the RCBS 420gn out the Marlin at 1800 fps. The second lot didn't make 1300 fps.
Maybe we have a completely different powder than from 03, maybe! I will proceed with caution however.
That 35 Whelen is a puzzlement because with a 4831 of either brand you shouldn't be able to stuff enough in a 35 Whelen with a 250gn bullet to do that.
I wonder if maybe two powder types somehow got blended during the pull down process.

[BCB]

My canister says 4064 loading data...

Any thoughts about use in the 6.8mm SPC?...

95 to 110 grain...

6.8mm is my latest project...

Data is limited for many powders...

BCB

[TCLouis]

Bullshop et. al.

I don't think Jeff is as liberal with his labeling as the government is with accepting their lots of powder.

They test the lot and then load to the parameters of that lot. Wehn lots fit in train cars rather than cans, the acceptable variation is much greater.

Years ago we were discussing powder variation and he mentioned milsurp powder that he found had a very large distribution in "speed" across the different lots available.

I have two cans of 2400 (significant difference in production date) and one would never guess they were the same powder from appearance. A third can still sealed may not resemble either of the others.


I can see that the season for developing loads with the 7383 is over if I plan to hunt with the same load next winter especially in the 257 and 6.5X257.

[Bullshop]

My lot say 4831 less 15%

[Patricklaw]

Thanks all. I appreciate hearing about the experiences and have requested the 12 pages of notes offered above. I suspect that our original author Tatume may have moved. If not, I'd love to hear if you've tried anything sir. So far, I haven't heard anything too discouraging.

I'm going to give this a try as soon as I can get some range time.

[madsenshooter]

I've been digging around finding information on the decomposition (burning) of nitroguanidine and found some interesting information. It does its best at a specific temperature, releasing gases that would act to inhibit the flash (still burning gases) produced by the nitrocellulose which comprises 85% of 7383's make up. That makes me wonder if it's even wise to use a magnum primer, let alone boost it. But, we also have to consider that the round has a primer much larger than any LR primer. There is also likely a reason the round has a tube that starts the burning of the powder near the middle of the cartridge. Anyone sell "powder penetrators" anymore? A lot of you won't know what I'm talking about, but it's an idea Elmer Keith had at one time. Here's what I mean by the tube: http://cartridgecollectors.org/cmo/cmo08dec.htm

[Skipper]

Seriously though, it's a triple based powder.

http://www.imrpowder.com/PDF/MSDS%20Files/Smokeless/IMR/Single%20Base_IMR-SR-PB/IMR%20Singles%20Base%20-%20Canada.pdf

[daengmei]

The numbers look similar, but IMR 7383 IS NOT on that list of single base powders.....confusion can be hazardous.

[madsenshooter]

Jeff says single base too, but I found out different. And, despite what it says on GI Brass, it was not made to replace 4831 in the cartridge. 4831 was never used in the cartridge, except in the proof round and maybe experimental cartridges. 7383 was made so that 110gr of it, the amount needed to duplicate the trajectory of the 106mm round, would take up the same volume as the 143gr of 4831 that's in the proof round, which might be a compressed load. That 110gr of 7383 produces 38000psi vs the 55000psi from the 143gr of 4831.

I don't think it's meant to be clean burning, period. After all, the whole purpose of the nitroguanidine is to make the nitrocellulose burn cooler and without flash, meaning there's no floating around still burning gases to be expelled out the muzzle.

Oops, I was wrong! 4831 was at one time used in the M48 spotter-tracer round. Back in 1968 the load was 120gr of it. In that case, the 143gr of the proof load must be a compressed charge.

120gr of 4831 produced 35,000psi vs 38,000psi for the 110gr load of 7383 and velocity was 1850fps for the 4831, 1745fps for the 7383.

[mikeym1a]

Okay. Just what is 7383 used for? What little I've seen I get the impression that it is used in large case, heavy bullet applications. I have seen it on shelves in a lot of different stores, and doesn't seem to go very fast. Is this a magnum type powder? Was it meant for the .50s and the 20mms? Since it is available, it would be nice to be able to use it, but, I just shoot regular small bore rounds, and I get the impression that it is not for that application. Thanks. mikey

[madsenshooter]

I don't think you're seeing 7383 in stores Mikey, it's a surplus powder. It was used in the 50caliber spotting rifle for the 106mm recoiless rifle. The 50 caliber round it was used in is about half the length of a 50BMG round. The gunner looks through the sight of the recoiless rifle, fires the spotting round, if the spotting round hits, he then fires the main gun.

[mikeym1a]

I'll have to check. Could have sworn that was what I saw. Thanks. mikey

[MT Gianni]

IMR 7828 is what a few confuse it with. All I have seen is surplus only.

[mikeym1a]

IMR 7828 is what a few confuse it with. All I have seen is surplus only.
That may well be what I saw. I get dyslexic from time to time. mikey

[Elkins45]

http://www.imrpowder.com/PDF/MSDS%20Files/Smokeless/IMR/Single%20Base_IMR-SR-PB/IMR%20Singles%20Base%20-%20Canada.pdf

I don't think that list applies here, because the stuff we are talking about was never intended to be a canister powder, and hasn't been produced in a long time. I'm assuming this list only includes current production?

[daengmei]

That list does not apply because the powder discussed in this thread is IMR 7383. The powder listed in that pdf is not the same. Like some are seeing, the numbers are somewhat similar and can cause confusion.

[madsenshooter]

It appears to be very similar in burn rate to RL19, Hybrid 100V, N204, and VV N550. Right in between 4350 and 4831.

[Hamish]

According to Jim, who has researched and loaded it for many years, doing the research with several here on CB, 7383 is a whole different ball game, do not apply what you have learned about any other powder to it, and most importantly, when you get to the point in load work up that it suddenly burns clean, STOP, after that you are pushing your luck.

[madsenshooter]

I would speculate that at the point of burn cleaning, you've already overcome the inhibitors that were meant to prevent muzzle flash and keep pressure in line. If we knew an old recoiless shooter, he could probably tell us just how dirty the powder burned in the spotting rifle. And dirty is a somewhat relative term, big difference between a bit of soot and unburned grains. Any of us who have used ball powder with their inhibitors knows soot, and without a hotter primer, unburned grains. Just the nature of the stuff vs single based nitrocellulose. Not all powders are meant to burn to an ash grey, like RL19 or 4895 does. I should quit theorizing, go out and shoot some to see how it works. I hope good enough to use in my Krag at Camp Perry this year, seems perfect for the round with jacketed and cast both.

[Skipper]

I guess IMR is confused, too:


IMR7383 is a single based powder designed for a specialized spotter round used in a 50 caliber submunition used to zero tanks and recoilless rifles. There is no sporting data for the 7383 as it was designed so specifically for the one cartridge and one use.

Mike Daly
Customer Service Manager
Hodgdon Family of Fine Propellants
Hodgdon Smokeless Powder
IMR Powder Company
Winchester Smokeless Propellants
GOEX Blackpowder

[madsenshooter]

The nitroguanidine is a known, I'm trying to figure out where others came up with the idea it had nitroglycerine too. If the weather will cooperate, I'm going to shoot some tmrw.

[Skipper]

Yeah, I wonder if it's just an anti-flash additive/deterrent that someone mislabeled as a major component :-?

[wiljen]

I had the chemical analysis run on 3 lots a couple years ago:

(Copied from original post)
I found out some interesting facts.

1.) Per the tests I had run neither of us (myself or Shady) was 100% correct. It is a double based propellant, not triple. But the two bases are NitroCellulose and Nitroguanidine. It does not based on the tests contain NitroGlycerin.

2.) One of the chemists at the plant I used to test used to work up the road at Radford Arsenal that made the Rad78L lot and shed some light on it.

3.) The number assigned to it being associated to Hercules and the RAD78L lot are correct in that it was produced at Radford Arsenal in Virginia (now owned by Alliant, then Hercules).

They were experimenting with Nitroguanidine at the time to try and cure some of the problems that plagued early 5.56 ammo. The hope was to maintain pressures while lowering flame temp and improving velocity but it was found to be unsuitable for use due to the added bulk.

All the lots tested for me did contain between 4 and 6% Nitroguanidine along with Nitrocellulose and DiNitrotoluene. Two of the lots also showed trace amounts of Dinitrobenzene which is likely a biproduct of DNT creation.

[madsenshooter]

Thanks for the clarification wiljen. Interesting to note that 7383 came about during Vietnam. The info I found indicating previous use of 120gr of 4831 in the spotter round was from Frankford arsenal, circa 1968. Although nitroguanidine is an explosive, it appears that in this case it is used as to snuff out the burning gas of the nitrocellulose, sorta like killing a oil well fire with nitroglycerine.

[freebullet]

Interesting stuff here.

[Bullshop]

My recent lot number from Jef Bartlet is 48000. Anyone else using from this lot number?

[madsenshooter]

I have that lot #, and have some loaded for my Krag, but mother nature is not cooperating with my plans. In fact one of the reasons I went with the powder was your results with 200gr bullets, as I'm looking for 2150fps with that weight.

[Bullshop]

What a coincidence I was out this afternoon shooting the 308 with that powder and the 200gn NEI-DD boolit. I found an old plow blade painted it white and set it out at 750 yards. I didn't have an exact BC for the boolit so took a wag at 37 minutes from a 100 yard zero. First shot went about 5 minutes low so came up 5 and the next shot was right at the base of the plow blade. Came up one more and started clanging the plow with boring regularity.
There was a fairly stiff cross wind that took 7.5 minutes to get centered. Got that right on the first try.
It was lots of fun then an antelope meandering out by my target tried to tempt me but it didn't work.

[madsenshooter]

Cool, I used to belong to a club in N. IN where we had a 1000yd range. Deer and wild turkeys were frequent visitors. They must've grown up near the range and paid little heed to the gunfire. The temptation is hard to resist when you're at the range alone. One fellow there really liked to keep the groundhog population down at the 1000yd backstop. His longest kill was 1012yds. Like you, he had the range down, but unlike you, wasn't a cast bullet shooter.

[madsenshooter]

Ma nature let me out of the house for awhile today. I got to try shooting some of this powder, 40gr under NOE's 316365 sized .311 and .314 both weighing 202gr. The report was a lot different from what I usually get with slow burning powders in the 24" barreled Krag cutdown. More a thud than a boom. I was using standard primers and had some unburned granules laying in the bottom of the bore. Hopefully a magnum primer will cure that. Accuracy wasn't bad, the larger bullet went about 3" @ 100yd, the smaller about the same with a couple unexplained fliers. The burn wasn't exceptionally dirty, not as bad as a caseful of W860. I'll try to find some magnum primers, the nearest gunstore doesn't have any.

[madsenshooter]

I don't have any magnum primers, so I tried an experiment in my Krag. I put 3.2gr of 10B101 under 36.8gr of 7383 with a 190gr 311365 sized .311 on top. Fed 210 primer. The unburned granules went away and the smoke was more grey than black. Pressure was a bit less than 36000psi, as I know my alloy blows back on the case neck prior to reaching that level. There was a little blowing back, so I'll try a tad less of the 10B101. The idea here is to get enough oomph to simulate the larger 50BMG primer, without going overboard. The large flakes of the 10B101 ought to keep it in place below the grains of 7383.