Milsurp 7383 powder workup

Jimbeaux82

Handloader
Jan 6, 2011
358
23
About 10 or 15 years ago I bought a shipment of milsurp powders from Gi-Brass (Jeff Bartlett). One of the 8 lb jugs was a powder called IMR 7383 , not to be confused with IMR 7828 cannister powder , which we are all familiar with. It is listed as a milsurp replacement for 4831 and advised to use 4831 data less 15%. Since I have been snowed /iced in at home in Louisiana I decided to do a work up of this powder to see how it reacts. Also, since powder is extremely hard to purchase these days, I thought some reloaders might be interested in this milsurp powder as a replacement if they can find some. My goal was to get within 100 fps of IMR/H4831 velocities without burning up too many components. So I focused on 4 cartridges to work up; 243 Win - 100 gr bullet, 270 Win - 130 gr bullet, 7mm Rem Mag - 160 gr bullet, and 30/06 - 150 gr bullet. I fired 2 shots at each charge wt thru a Magneto-speed for velocity and keep in mind the listed Avg and SD is for 2 shots only. As always, and specifically for milsurp powder, use extreme care in utilizing this data. It was safe in my rifles under the conditions I tested it in. Here goes:

243 Win, 100 gr bullet, Husquavarna 22" barrel, book max load listed IMR/H4831 43 grs, target vel - 2900 fps
36 grs - 2474 fps, SD = 44
37 grs - 2551 fps, SD = 6
38 grs - 2635 fps, SD = 92
39 grs - 2689 fps, SD = 109
40 grs - 2811 fps, SD = 14

Possibly could make 2900 fps but would need to work up further in 1/2 gr increments

270 Win, 130 gr bullet, Sako A5 23" barrel, book max load listed IMR/H4831 56/60 grs, target vel - 3000 fps
50 grs - 2739 fps, SD=80
51 grs - 2781 fps, SD = 28
52 grs - 2889 fps , SD = 10
52.5 grs - 2893 fps , SD= 58

I think this is max and will not work up further based on "lull".

7mm Rem Mag, 160 gr bullet, T/C Venture 24" barrel, book max listed IMR/H4831 61/60 grs, target vel-2850 fps
52 grs - 2280 fps, SD=11
53 grs - 2328 fps, SD = 11
55 grs - 2420 fps, SD = 14
57 grs - 2537 fps, SD= 64
59 grs - 2739 fps , SD=5

Could possibly work up a little further at 1/2 gr increments

30/06, 150 gr bullet, Win Mod 70, 22" barrel, book max listed IMR/H4831 59/61 grs, target vel - 2800 fps
50 grs - 2456 fps, SD=86
51 grs - 2560 fps, SD=30
52 grs - 2608 fps, SD=29
53 grs - 2646 fps, SD=9
54grs - 2694 fps, SD=2 (case full slightly compressed)

case full, that is it here.

As you can see, I was able to get within 100 fps of most max book velocities. All my testing was done at 30 deg. My data showed closer to 4831 less 10%. Before I push it further I will retest the fastest loads this summer to get a feel for its temp stability before pushing any further. I did not group for accuracy may do that this summer.

Hope someone else finds this data useful or at least interesting.

Powder was IMR 7383 Milsurp lot 48001.

Good shootin

Jimbeaux
 

FOTIS

Range Officer
Staff member
Oct 30, 2004
23,009
48
I ordered 8 lbs of that and wc 857 (h1000/RL 25 burning rate) last month.

He is 5-6 weeks out in shipping.....
 

baltz526

Handloader
Sep 25, 2005
1,073
6
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IMR 7383
The main thing to remember about IMR7383 is that it is a HIGH ENERGY TRIPLE BASE PROPELLANT that goes by different rules of loading density than the normal single and double base propellants that we are normally used to. The third ingredient is nitro guanidine, which supplies both the increased energy content and confers its flashless characteristics. It also makes it very peaky when approaching its upper load limits, giving absolutely no warning like the single and double base propellants do that a high pressure excursion is about to happen. This cranky nature is a very unfortunate characteristic of this otherwise quite useful powder. The reason why it is flashless is because it was designed specifically as the propellant for the .50 cal spotter rifle used to aim the 105 mm recoilless rifle. For the purpose of aiming a cannon by spotting it is a good idea for the spotting rifle to be flashless to keep the enemy from seeing the muzzle flash and returning fire before the main 105mm cannon has a chance to be fired, which is not flashless. As soon as the 105mm cannon is fired, the crew leaves immediately. I have fired my .30-06 700 ADL at night and instead of getting blinded with a large bright muzzle flash like IMR4895 makes, all I saw was a faint dull red streak emanating from the muzzle. There are at least three lots of IMR7383 that I know of and their characteristic are all different, so what goes for one lot will not work for another and it is a good idea to start off conservatively using IMR4064 loading data. I use IMR4064 data myself and have had good results. Also, it is not the best cast boolit powder around, although I get reasonable results in my French 36 MAS with the 180-grain Lee. Since the French cartridge is practically identical to the 7.65 Argentine/Belgian Mauser, it should work just as well in that rifle/cartridge combination. With around 39 grains if IMR7383 it also works well using 140-grain .308 brass tracer jackets in the French and .308 Winchester cartridges.

I am not trying to discourage using IMR7383 by any means, just be careful.

(Written by Linstrum)

I will add to what Linstrum posted by saying that I have found 7383 to burn very dirty below the pressures it needs and that once you find a clean burning load, you have reached the sweet spot. Going beyond the point at which you get clean burn is begging for a pressure excursion and should not be done. 7383 is certainly a powder where too much of a good thing is a very bad thing. I also find that 7383 doesn't like empty space in the case with it nor does it like compression. Best loads are most commonly found between 85% fill and 105% case fill. Below 85% is often erratic and above 105% is usually asking for problems with pressure. available powders and all other currently available surplus powders. It requires special care when loading so has been given a section of its own.

The data provided here was safe in the author's gun at the time it was produced. This in no way implies it is safe in any other gun or should be used. Always use caution and work up carefully. We take no responsibility for the use of any data found on this page.

Jim's 7383 Data
This is the collective data Jim has provided.
Will's 7383 Data
My results of using 7383 in various cartridges.
 

Johnly

Beginner
Dec 12, 2020
49
15
http://castboolits.gunloads.com/showthr ... ase-powder

7383 "triple base" story origin

I'll tell you exactly how the "triple base" story got started. Back in the late 1990s-early 2000s my friend Linstrum told me in private E-mails of the great results he was getting with basically full case loads of 7383 in various military cartridges of the .30 caliber to 8mm class. At the time Hi-Tech had a lot of it in 7 lb. jugs for $28, so I got in a good supply. I found it to shoot well in cartridges including .30-06 with 150-180 grain jacketed bullets, .22-250 with 55 & 60 grain jacketed bullets, and later with cast bullets in 8mm Mauser, 7.5mm Swiss (of both the more modern 7.5X55 and the original 7.5X53.5, GP90 sort of load for the old 1889 Swiss rifle), and in the .300 Weatherby Magnum with cast loads. I noticed some quirks about this powder right away. It is about 7/8 the bulk density of other IMR tubular powders, and a noncompressed full case load won't come close to factory load velocities in the .22-250 or .30-06. In trying to push this I loaded some compressed loads and quickly discovered the sharp pressure rise that occurs when you compress it, perhaps due to fractured grains burning faster. You can get away with some compression, but be very cautious. The powder doesn't burn completely at less than full loads in the previously mentioned cartridges (other than the .300 Weatherby where I only tried it for reduced loads, about 2200 FPS with the 200 grain "30 HBC" boolit. In .45-70 so much of it doesn't burn that a somewhat compressed case load with 340 grain boolits was giving me velocities around 1200 FPS and jammed the action of my 1895 Marlin with unburned powder grains. Took a while to get all of that out. This led to the observation that most extruded powders have a gray surface from graphite coating, but when partly burned so the surface is burned off the inside part is usually yellowish or greenish and translucent, but the 7383 grains are jet black through and through. It's got either graphite or carbon black pigment mixed in it. Now to the point of this story. When this stuff is fired, the powder gas has a pungent odor of ammonia! I have never smelled this from any other powders. From rifle loads that burned most of the powder, the ammonia smell is all in the cloud blown out of the muzzle, while the freshly fired cases and bores smell like ordinary smokeless powder. With the abortive .45-70 loads that barely burned the powder, I got ammonia smell on opening the action. So I figured that the ammonia had to be coming from a surface coating that quickly burned off and got blown down the bore to come out first, while the remaining powder burning didn't produce it. Speculating about what could make the ammonia, I thought that the coating of the grains might have nitroguanidine in it, as NQ is said to deflagrate with a lot of sooty smoke and ammonia among the gases, producing no flash in the process. So I thought that could explain why they would try that since this powder was used in the .50 caliber spotter rifle fired before the main barrel of the 106 mm recoilless rifle. If there was such a coating on the grains, that gas would emerge first from the muzzle, reducing muzzle flash, which would reduce exposure to the enemy of where the spotter shot came from before the big bang. I could find absolutely no reference anywhere to nitroguanidine being used as a coating on small arms powders, or in any other way for that matter. It's a well known ingredient in triple base artillery powders, of course. So all of this is pure speculation on my part. Linstrum and I were carrying on lively E-mail discussions about all this. He told me that nitroguanidine on slow heating decomposes with hydrogen cyanide as one of the products. So I scattered grains of 7383 on the surface of the solid lead in my casting pot and watched as it slowly heated. The 7383 grains burned off with much less flame than other IMR powders I've done this way. Each produced a strong puff of very yellow smoke. I don't think I've ever smelled any real bitter almonds, but the smoke had a peculiar smell like stinkbugs that I thought might be the cyanide odor that's described as like bitter almonds. So that encouraged Linstrum and me to think that there likely was nitroguanidine in the coating. Somewhat later Linstrum posted a thread on here about 7383 that's been widely read and is one of the first things that comes up if you Google IMR 7383. In it he strongly warned that one should be very careful with this powder because it is a "high energy triple base powder!" I think that was a jump beyond the evidence I just laid out. The stratification of the ammonia gas in burning in the gun suggests that whatever makes it is in a surface coating only, NOT mixed into the matrix of the powder as would be the case with a triple base powder. So there you have it. I would LOVE to hear from someone with real historical knowledge of how 7383 was produced and its ingredients, or if someone with access to the proper lab facilites would do some qualitative analysis of its ingredients. Linstrum and I could be completely wrong about the nitroguanidine hypothesis. But if so, I want to know what makes the ammonia smell! Meanwhile I still have a good bit of this and will keep right on using it as my mainstay powder for cast boolits and moderate jacketed loads in midsize rifle cartridges and will probably use it again as a reduced load powder in the .300 Weatherby. The ammonia smell bothers some of my neighbors at the range, but not me.

**************
http://www.gibrass.com/gunpowder.html

IMR7383 This is a slow burning stick powder originally used for the Cal. .50
M48A2 Spotter/Tracer round. This is not the same case as that known as
the .50 Browning Machine Gun cartridge. This powder is NOT recommended
for the .50 BMG round. It is a very bulky, single-based powder, composed
of 85% nitrocellulose and 15% stabilizers, flash inhibitors and graphite;
that was developed to replace the IMR4831 powder that had being used.
It has about the same propellant energy as IMR4831 when compared in equal
volume. IMR4831 data can be used. Begin with starting loads, reduced 15%
by weight.

*************
 

Jimbeaux82

Handloader
Jan 6, 2011
358
23
Good data. Thanks for posting. I had heard that IMR 7383 was tricky to work with and did not show normal pressure signs like we are accustomed to and had a sudden and sharp pressure spike. That is why I was working up so carefully.
 
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