How much can 7383 be reduced?

[singleshotbuff]

Gentlemen,

I'm fairly new to using IMR-7383 (just got my second jug today), having only used it with jWord bullets in mostly full case loads in 8X57mm, 7.5X55mm and 7.62X54R.

Now I'd like to try some cast loads with this powder. Since all I use right now are plain base boolits, I obviously need slower loads than I am getting with full power loads.

My question is, how much can I safely reduce this powder? I understand there are safety issues when using much reduced charges of most "stick" powders. Do these apply to 7383 with it's "quirky" nature and low density? Would a dacron filler help?

For example, I use 48grs of 7383, with a 150gr jWord bullet, in my 7.5X55mm. I get about 2650 f.p.s. with this load. If I switch to a 160gr plain base boolit, how low can I go with the charge weight to get the velocity down for a better chance of success?

Thanks for any input.

SSB

[Ricochet]

I haven't tried very reduced loads of it, because I'm a little afraid of the "SEE" phenomenon, and I know it doesn't burn well at very low pressures. I made a real mess in my 1895 Marlin .45-70 by using a full load of the stuff under a 340 grain cast boolit. The powder's way too slow for that and left intact, half burned grains that locked up my action tighter'n Dick's hatband. It was a real job cleaning the powder out. You'd run into a lot of that with low charges in the Swiss, I think.

I don't think it's suitable for plain base boolits in typical military calibers. Works best with gas checked boolits around the 2000 FPS range, I think.

[singleshotbuff]

Ricochet,

Kinda what I was afraid to hear, I knew you'd have an answer for me.

You seem to be "the man" on 7383. Guess I better just start PMing you my questions about it instead of posting them LOL.

Since I have your ear, what about wc860 in the Swiss with 160gr boolits? I haven't tried 860 in 7.5X55mm yet, been working with it in 8X57mm.

Thanks

SSB

[Maven]

ssb, 48gr. WC 860 + a mag. primer will work in the 7.5 x 55mm, the 8 x 57mm and the .30-06 with CB's between 160gr. - 200gr. In deference to the 160gr. CB, start at 46gr. , chrono. your loads and work up to 48gr. (You can use 49+gr., but I haven't found it necessary or particularly desirable.)

[singleshotbuff]

Maven,

Thanks for that info. I imagine (based on my tests with 860 in 8X57mm with jWord bullets) that there will be a lot of unburned powder in the barrel and cases.

SSB

[Maven]

Shawn, The 48gr. load I suggested will leave unburned powder in your bbl. (dry patch after ~5 - 10 shots), but very little in the fired cases. The trick is to use it with the heavier CB's, i.e., 175gr. or more, since it burns more efficiently with greater pressure. Btw, there's just the merest powder smudge on the case necks with this load and accuracy is as good as you can hold.

[Ricochet]

I haven't yet tried WC860 in the Swiss, but probably will try it with the heavier bullets. I've got a good stock of it and of WC872 when the WC860 runs out.

I definitely will try 7383 in about full case quantities with the 113 grain Lee "Soup Can."

[BeeMan]

I found erratic velocities with 7383 behind the RCBS 180 FP in 30-06, when trying to load down. Gave up and now use the 7383 in 243 with 70 grain jacketed, which makes a fine target load. I had better luck with cast in the 06 using 820, as Maven has reported.

BeeMan

[Maven]

All, Maybe we should say 7383 is a "niche" propellant. I.e., it has a narrow range of applications, but excells if confined to that range. The smallest quantity of 7383 I used was 35gr. in my K-31 (suggested by Vly) with Ly. #311466. While it was accurate enough and clean burning, velocity was higher than I wanted: 1,967fps, +- 21fps. ES was 21fps. Btw, this load was tested in 2 K-31-s, neither of which showing any evidence of bore leading. On the other hand, 40gr. - 41gr. with 87gr. Hornady BTHP's is extremely accurate, clean-burning and fast in my .243Win. Pressure rose, however, when I tried 43gr. (same bullet) @ ~85 deg. F. 41gr. is a MAX. load for me! As I had some .30cal. 125gr. SP's lying around, I tried them in my .30-06 with 55gr. 7383 v. 55gr. IMR 4350. Accuracy was the same with both powders, but 7383 filled the case more and gave higher velocity: 2,697fps +- 22 v. 2,545 +-23. Ambient temp. was ~80 - 85deg. F. This was a safe load in my rifle. I think 7383 is a good choice for certain applications: Higher loading densities, but with little/no compression: approach higher density loads with caution since pressure rises can be sudden and high: use cast or jacketed bullets with the former cautions in mind. Reduced charges of 7383, and WC 860 and 872 for that matter, are BAD ideas. AA 5744, IMR 4198, VV N133, especially the first mentioned, are much better choices for that sort of thing.

[Jim]

[QUOTE=Maven;162391]All, Maybe we should say 7383 is a "niche" propellant. I.e., it has a narrow range of applications, but excells if confined to that range.

Maven,
You got that right! I remember 5 or 6 yrs. back when I started messin' with this stuff havin' to learn all it's idiosyncricies. And, man, does it have a lot! What I quoted you saying above couldn't be said better and nothing more need be said!

Jim
Vice President, Glue Shooters Society

[Nobade]

I've been burning a lot of 7383 in my 260 Rem lately, and it works wonderfully there. It really likes the big case/small bore rounds, and in this rifle uses 37gr. under a 140 A max and 27gr. under the RCBS 140 SIL. The reduced charge works fine, and gives terrific accuracy. But I wouldn't try that in a bigger bore rifle, you just can't build the pressure to get it to burn properly.