IMR 7383, conflicting information

[Erebos]

Hi. Long time reader here, finally registered to post.

I'm wondering about IMR 7383. I'm seeing some conflicting information as to whether it is a single base powder or a triple base powder.

GI Brass has it for sale, and lists it as a single base. http://gibrass.com/gunpowder.html

I sent an email to that company as to whether it's single or triple base, and got this link back as a reply. http://www.parttarget.com/1376-01-049-1452_1376010491452_10534781-3.html (http://www.parttarget.com/1376-01-049-1452_1376010491452_10534781-3.html) This also says it's single base. Here's a screencap of that page, in case the link doesn't work right.135488

http://www.castpics.net/LoadData/7383/default.html

Over at that castpics link, it is stated to be a triple base propellant. Just about every other forum post I've seen says it's triple base.

What's the deal? Am I missing something?

How can I verify for myself if a powder is single base or triple base?

[Yodogsandman]

I wondered the same thing. Maybe someone here knows.

[freebullet]

Why would it matter? It never made a difference in how I use it.

[Erebos]

I want to be absolutely sure I'm not looking at two different powders that share the same name/number. Also curiosity to verify the truth.

[Erebos]

Somebody's information has to be wrong.

[freebullet]

I think member Maven had it analyzed. I don't remember the results, some searching should reveal the info you seek.

[Bored1]

Looks like it might have been wiljen check post #39 here!

http://castboolits.gunloads.com/showthread.php?210359-IMR-7383-duplex/page2

Not sure what it is. All I know is everyone says to be super careful with it, so that's what I'm planning on!!!!

[Elkins45]

As of a couple of years ago (when I first bought some) GI Brass described it as triple base as well. He just recently changed his description, probably based on the fact that someone apparently asked DuPont about it. It used to say that it contained nitroguanadine but I no longer know if I believe that to be true.

It's pretty touchy stuff, and it smells like no other powder when it burns. I think that's the flash suppressant coating.

[Erebos]

Thanks, Bored1. That provided a lot of useful information, and is a great starting place for my research.

It sort of brings up even more questions, though. Why is that powder listed as single base now, when before it was clearly....per the lab that tested it...something "else". Is the current listing wrong, or has the powder been replaced with a new single base formula that is designed to fill the same role, and the name got reused? That's a possibility I find concerning, because the data and safe use practices for new and old would certainly not be the same.

I'm going to look around at the other sites that sell surplus powder, and see what they have it listed as, and maybe send another email to GI Brass.

[Erebos]

Well, nevermind. GI Brass appears to be the only store that has that right now.

[madsenshooter]

Yes the nitroguanidine is there, but I wouldn't say it's a part of the base. It's in the coating, an explosive meant to keep the nitrocellulose base from burning with a flame. No flame, no muzzle flash. In my opinion, takes the temp and pressure of a 50BMG primer to get that explosion to initiate at the proper time. I don't get much of the smell others are talking about when I boost it a tad to get up to 50BMG primer temp and pressure. No, compression, just a light touch of the bullet to keep the booster in place. I think burning it without the proper temp and pressure is more a danger than boosting it up, cause the explosion isn't there and gases resulting from trying to slow burn it are more volatile. Boom! Lots vary, so some lots may work fine without the booster.

[Erebos]

So it sounds like it was simply "reclassified" to a more correct description as single base, since the nitroguanadine isn't actively working as a propellant/major ingredient. Sound about right?

[Erebos]

I got a reply back from Jeff Bartlett at GI Brass. Here is what he sent me.

"I have not found any credible info that indicates IMR7383 as triple based.
However, I have pasted a response to an Email I sent to an ex-OIC of Lake City AAP, who oversaw opns from 1968-1972.

IMR 7383 is a single based propellant and composed of about 85% nitrocellulose (NC) and 15% graphite, stabilizers and flash inhibitors. Believe me it does not contain nitroquanidine, unless you or someone else added it? BTW, the IMR 7383 tubular grains are supposed to be 0.038" in diameter and 0.085" long and if anything else is added you should be able to detect it?

Please remember that IMR 7383 was specifically blended for use in the .50 Spotter Cartridge with short (2.00" long) case with a 50M percussion primer and flash tube, the nominal charge weight was 110 grs. which in the .50 M8C aiming rifle produced a peak chamber pressure of approx. 38,000 psi.

This is all the info I have. On the other hand, be advised that in 1986, the DRMS released three (3) lot numbers of new, virgin IMR7383. Two lots were manufactured by duPont, and one lot was from the Radford Ordnance works. It is my understanding that the Radford lot barely passed the DPA tests, whereas the duPont lots were fine. It could be that over time, the DPA %-age of the Radford lot has deteriorated to being somewhat unstable and/or unpredictable.
Having personally consumed over 100lbs from the duPont lot that I sell (lot 48000), I have had no issues whatsoever.
Here is another website that might have additional info for you.
http://www.nsncenter.com/NSN/1376-01-049-1452

Jeff Bartlett"

That NSN link contains the actual formulation data, as relevant to the people involved in the supply chain for it's intended use.

Note: he's still selling from lot no. 48000, which is a specific lot number I see other people mentioning.

135559

So that begs the question, what is the source of the conflicting information.

[madsenshooter]

All I know, is that with heavy cast bullets in the Krag, it doesn't get going even with LRM primers. Partially burned granules are left down the barrel. Ditto 168 jacketed in the Garand, some of the partially burned grains fall back into the chamber upon extraction. It does get going with a little extra flash. I've got better results placing that bit of extra flash higher up in the powder column than at the base. The powder was supposed to be flashless, if the flash inhibitor wasn't nitroguanidine, then the powder wasn't made to spec. If you stop once it burns clean, it's wonderful powder for the US Krag with heavy bullets, delivering pressures the Krag can live with.

[nekshot]

I know the unknown is there and this stuff must be used with common sense. What others are doing safely is what I do. I don't try experiment with unknown powder. I get more a thrill in the gun going bang and the bullet chugging along economically than spending what I am a little short of and shooting less howbeit with mach speeds. Bring on the surplus!

[madsenshooter]

Went out yesterday and shot a few duplexed loads of 7383 out of my K31. Federal 215M primer, 30.5gr 7383 at the bottom, 4gr 10B101 in the middle, 14.5 7383 on top for a total of 49gr. Over that went an Ideal 308329 spitzer that weighed in at 175gr checked and lubed. Nothing broke, recoil was only slightly more than a 2000fps load I'd been shooting earlier, smoke out the end of the barrel was black. No unburned powder down the barrel or left in the case. No alloy blew back on the caseneck, so I didn't exceed the alloy's pressure limit. I had previously moved the front sight to get on target with a 168gr Eagan flatnose. It appeared to me that if I'd shot the spitzers first, I'd have been on target where the sight originally was, at the index mark that's on it. Guesstimated velocity 2200-2300fps. I hit the target @100yds from prone, the shots weren't any sort of group, but I'm out of practice, and it's the first time I shot the rifle without a scope. Now that the cases are fireformed to the K31 chamber, I can get another 1.5gr in them. Note that this experiment was with lot #48000. Do not try with other lot numbers!

[cmdrted]

I have been using it in 303 british with 311299 cast linotype bullets. I do the recommended 4831 minus 15%. there was also a posted suggestion, fill the case, measure the weight -75% to start cast loads. so far in 303 36-37 is a sweet spot 1725 fps 1.5 moa at 100yds

[cmdrted]

I guess what i was attemping to say but got blind sided (I'm at work), so far no troubles with this powder as following the suggestions from jeff bartlett and another sage reloader here on the site. I read all the posts before jumping in and trying this powder, And to tell the truth that first round went into some part of the backstop as i braced and flinched hoping the stuff really was stable. it was s mild to med push no flaming whistles or explosions. I intend to load it in my 8mm with the heavy noe lyman clone and 30-06 with the 311299 in the 03a3. all with the above precautions, but i feel comfortable with the powder now.

[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.

[Maven]

"I think member Maven had it analyzed. I don't remember the results, some searching should reveal the info you seek." ...freebullet

No, it wasn't me, but Shady Grady. He found a thorough description of IMR 7383 in a U.S. Army propellant manual and reproduced some of it here. Search for Shady Grady's posts about 7383, as they are most illuminating.

[Maven]

Here's the information Jeff Bartlett posted on his site re: IMR 7383:

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 (italics added) and 15% stabilizers, flash inhibitors and graphite;
that was developed to replace the IMR4831 powder that was 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.
This is new powder, not pulldown.
$60/7# jug

[madsenshooter]

It's worked out to be closer to "by weight" than "by volume", comparing it to H4831SC, and not counting the kicker used with the 7383. In other words, put enough fire to it and it burns like IMR4831.

[madsenshooter]

J word load. 190gr PRVI match bullet 18.5gr 7383/3.2gr 10B101/18.5gr 7383, 40.2gr total charge. Pretty much max load for a Krag, grey smoke, guesstimating 2200-2300fps. The bullet is thicker jacketed than US match bullets, mics .3085 and has a long bearing surface. group is 1.25" tall x .5" wide. 100yd, 1902 sight all the way down, 6 oclock hold, off the bench. I have some loaded with an equal weight of RL19 that I'll compare next time I'm out. The PRVI bullets really varied in the tip, more than .030 in length, but I found an old CH 7.5X55 seating die that made a perfect file trim die.

[Maven]

Great results ms, but I think I'd back off by 1 gr. in deference to the Krag's age and action strength.

[madsenshooter]

It makes for a case full to the base of the bullet Maven, that way I don't have to fret about the kicker going anywhere. It appears to me that as case capacity increases, the amount of kicker needed to get the job done does too. 3.2gr is fine in the Krag, but in 7.5 Swiss, 4 isn't quite enough to get to the grey smoke stage. Ditto 30-06. Could be a little less, say 2.5gr would be enough in the 7.62x39 with heavy bullets.

[madsenshooter]

I got out to shoot some more of the same load I mentioned above, and a comparable load, by weight, of RL19. I had to shoot from prone, which I've not done for awhile, so no great groups. But the equal weight of RL19 was hitting about the same area vertically and the primers looked about the same as with the boosted 7383. They're Federal GM215M primers, softer than CCI. I'd say both loads are about max for this particular Krag, no hard bolt uplift or extraction encountered. All in all, I'd say that boosted 7383 burns about the same rate as RL19, which is roughly right between 4350 and 4831. No doubt varying the amount of booster will alter the burn rate. As case capacity increases, the amount of booster required to reach the pressure and temp needed to set off the nitroguanidine increases. Some have said it doesn't contain nitroguanidine. I'm fairly certain it's there and if it isn't nitroguanidine, it's some other flash inhibitor that acts the same. It's a chemical meant to explode in order to snuff out the burning of the nitrocellulose. That's the way flashless powders work.

The Lyman 49th Ed. has some RL19 loads with a 220gr bullet. They show a max load of 46.5gr @ 38,500cup. 2250fps. I don't think I wanna try to go anywhere near there!

[madsenshooter]

With this powder, not much boosting is needed, and you need to work in small increments. I've been doing .3gr increments. In the Krag case, 3.5gr gets me to "no smoke" stage and I'm going no further. With that nitroguanidine explosion taking place initial pressure is high. 6 percent of 37gr is 2.2gr. So the nitroguanidine explosion is about like another LRM primer going off. I really think it would be wise to use this stuff boosted for J-words and that it might be best to leave it alone for other purposes. Trying to keep it down to cast bullet pressures, you're making a bunch of gases that at some point could go boom! I wish I had some pressure trace equipment like Larry has, but it ain't in the budget!