I first started using IMR7383 from Hi-Tech in April of 2003 and with the first shipment was a spec sheet reprinted from H.P. White Laboratories. The spec sheet listed several lots of IMR7383 and what grabbed my attention were the differences in characteristics between them. The particular lot of IMR7383 I got from Hi-Tech was not identified and the only way I could correlate my powder with the ones listed on the spec sheet was by the weight that would fill a particular manufacturer's .30-06 case. Thankfully there was enough disparity in bulk density between the various lots so identifying them that way was possible.

I ran several performance tests and what got my attention immediately was the chameleon-like behavior of the powder. It varied so much in performance from one caliber to the next that it was not possible for me classify the particular lot that I had as being like one particular powder. The stuff ranged from IMR4831-like to IMR4064-like. Its behavior depended on the cartridge, charge weight, and weight of bullet it was used with. When that occurs sirens and red warning lights should go off in your head, because the pressure-time curve characteristics of the powder are affected drastically by conditions that are normally minor for other powders.

NotRicochet and I are friends and we quite often share information and collaborate on projects. Both of us are chemists (he's an M.D., too) and we are also pretty well versed in physics. When we first started using IMR7383 we compared notes and found that we had made a lot of the same observations independently. One of the observations he made about IMR7383 is that it produces a lot of ammonia initially during combustion, which is the first gas in the stratified gas column to exit from a gun barrel and indicates its origin as being from a coating on the powder grains. Another observation is IMR7383�s chemistry is different from the others in the IMR series and contains a compound that decomposes into large amounts hydrogen cyanide when gently heated. Pyroxylin by itself doesn't do this, and most of the IMR series are single-base pyroxylin powders all with the same basic composition but with varying shapes and deterrents used to control pressure-time characteristics. I did some other simple chemical tests and what the results of our observations point at are that IMR7383 probably contains nitroguanidine. That compound is used in high-energy powders, which IMR7383 seems to be.

Nitroguanidine also has the characteristic of preventing muzzle flash, and that is a highly desirable characteristic for a powder used for spotter or pilot rounds.

Another feature of IMR7383 is that its tubular grains have extremely thin walls, which accounts for its bulk density being approximately 7/8 of powders like IMR4350 and IMR4895. That in itself could account for the powder's seemingly fickle behavior because as the powder column is initially collapsed inside the cartridge when first ignited, the powder grain tubes collapse and diminish the exposed area, which in turn slows the burn rate. That could in effect act as a pressure limiting mechanism. If something disrupts this mechanism, like an especially violent priming compound, then the powder would behave as a faster burning member of the IMR series PLUS also having a very high energy content!

I have about 70 pounds of the stuff and intend to use it for both cast and mild jacketed loads in various .30 cal milsurps. I make all of my loads as though it were IMR4064 and accept the results without pushing it. Like the guy said, it doesn�t take much to punch holes in paper. Be careful!

Does anybody know how this IMR7383 compares with IMR5010? I have a slug of the IMR5010 that I have used in my 7STW with heavy bullets 160 and 175. It shoots good and give decent velocity and group sizes.

linstrum ! Your scientific approach to the understanding of 7383 characteristics is refreshing and helpfull to say the least.Do you have data to share with us relating to slow igniton,increasing rate of energy release/change in Pressure or critical points that you may have approached or gone beyond. Have you any indication that compressed loads exhibit unusual results; stuff like that? Something in what you have written about has lead you to your conclusions and precautions.

My four jugs of 7383 have no lot number either and White's Lab report was not included with the powder. Thank you for your contribution roger

Hi, guys: My work with 7383 began by reading what others had already done with it. I could not understand the huge discrepancies in the reports, but a few of the guys doing the reporting were pretty reliable, so I knew something was up. One of the problems right away was that there were three or four different manufacturing lots of the stuff out there simultaneously and since they were not canister grade that accounted for some of the vagaries we were seeing, but not all. When I got some 7383 I found out for myself the stuff was all over the loading charts, so after the red warning lights and sirens quit I simply found out what the fastest powder was that it behaved like without pushing it hard and came up in the H-380 and IMR4064 neighborhood. So, to be on the safe side I adopted IMR4064 as the baseline reference for my loads. For the most part it behaves like under loaded 4350 when used at 4064 load densities, but because I know it is fickle I just leave it alone and accept it. It gets the bullet out of the barrel, which is what I want. You know, a lion will pull a cart as good as a horse, but if you keep beating a lion to go faster the results are very different than if you go beating a horse. If you want to push the performance of 7383 it's gonna turn on you! I keep several different kinds of canister grade powders on hand for when I want a top-performing load and leave the 7383 for the other 99% of my shooting where I don't need a balls-to-the-walls load. I never compressed the loading because it was plain to me that compressing it could conceivably pulverize the extremely fragile thin walled tubular grains and change its characteristics from just mechanically working it alone! The use of a magnum primer was probably what precipitated the problem right there in the .270 because it shattered the powder grains and turned some of it into Red Dot with a high-energy content attitude! So, I did not go "beating the lion" when I worked with 7383, I just let it do what it will without pushing the envelope. I talked to NotRicochet yesterday and he also came up with the same thoughts and conclusions about compressed loads and the use of magnum primers.

What Ricochet said.

I've used a lot of 5010 and by itself it probably doesn't start coming into a useful arena until you get into the smaller cal. ultra mags.It is to slow for max performance from 25-06 ,.264 mag. 7mm rem mag. and of course the 300winny.Some of the larger capacity cartridges in these calibers have not to bad performance with 5010. It would be hard to overload 5010 on it's own ; not so with 7383. roger

5010 is in no way similar to 7383. It's the IMR powder for .50 BMG and is far slower burning than 7383, which was made for the .50 Spotter cartridge. The .50 Spotter is to the .50 BMG about as the 7.62x39 is to the .30-06. A much smaller case. It also operates at a lower pressure than the .50 BMG, max average of 38,000 PSI.

bartsch: I would be very interested in your findings regarding IMR 7383 please email me a copy if you would to [EMAIL][/EMAIL] <br />Thanks,<br />James Howard