IMR 7383 with cast bullets in the SKS?

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Maven posted this 24 April 2015

Has anyone tried IMR 7383 with cast bullets in the SKS, specifically the Type 56 (Chinese, late manufacture/spike bayonet).  The reason I ask is that I take possession of the rifle tomorrow and have several pounds of 7383 which I'd like to put to good use.  I will be using the Lee ~175gr. RNGC bullet for the 8mm Mauser, which I've resized to .3145” to suit what I think is the Type 56's bore (owned one in the past and that dimension worked extremely well).  In the meantime, I've loaded 30 rounds with 8gr. Unique + 20 with 8.8gr. Unique and the resized Lee CB.  In short, is 7383 a good (or bad) idea in the 7.62 x 39mm cartridge?

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jeff houck posted this 25 April 2015

I don't recognize IMR 7383 powder. Did you by chance mistype this? Jeff

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onondaga posted this 25 April 2015

http://castbulletassoc.org/forum/view_user.php?id=126>Maven

IMR7383 is a Mil contract powder replacement for equal volume of 4831 and is approximately 15% bulkier than 4831. It is a very slow burn rate tubular extrusion powder. Here is a description of it from  http://www.gibrass.com/gunpowder.html >http://www.gibrass.com/gunpowder.html  a supplier:  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 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

A 100% density load of IMR 7383 will not over pressure a 7.62X39 SKS but the powder is not likely to develop enough pressure or the correct pressure curve to operate the action of an SKS reliably.

This powder needs heavy bullets, large cases and long barrels for it to light well. Your SKS is well out of the design parameter for IMR7383 and is likely to misfire, hang fire and muzzle flash and  if it lights at all there will be a full trail of partially burned particles down the bore after every shot. There is also a strong possibility that bullets will stop mid bore and cause catastrophic explosion on the next shot.

I'd say don't even try it in your SKS for the safety reasons. 7.62X39 really likes H4895 and AA2230 with cast bullets.

Gary

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Maven posted this 25 April 2015

Jeff, No I didn't make a typographical error:  IMR 7383 is an oddball, but usable milsurp powder, but perhaps not in the SKS.  See Onondaga's post below for a description of it.

Gary, I knew 7383 may not have been the best choice for the 7.62 x 39mm cartridge in a gas operated gun.  E.g., 5744, 4198, RL-7 would be much better, but I have none of those on hand and no local gun stores which carry any powder, let alone those.  In the meantime I've loaded 30 rounds with the resized Lee CB and 8.0gr. Unique and 20 with 8.8gr. Unique. If that's successful, I'll move up to 10gr.  Btw, I've had no trouble using 7383 as a substitute for IMR 4350 with jacketed bullets in the .243Win., .30-06, and 8mm Mau.  It works fairly well in the latter two with heavy CB's and loads of at least 37gr.

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onondaga posted this 25 April 2015

http://www.castbulletassoc.org/forum/view_user.php?id=126>Maven

 I have IMR7383 also. I purchased it for a specific application where it does fit. 30-06 with the Lee 300 AAC 230 gr cast bullet, it works fine there and burns well. I have also  tried it with the Lee 185 gr , it fires and groups well but my 1903A3 spits chunks and leaves a trail of partially burned powder down the bore when shooting the lighter 185 gr bullet. Accurate but bothersome messy with the lighter bullet. At $60 for 7 pounds it is worth the fight against messy even with shipping and hazmat when you get 2 or more jugs and it is new surplus, not a dirty pull-down.

Your powder choices are good ones that you listed. I forgot to add the one with freakishly high velocity in X39, the Hodgdon  H 322  will get the highest velocity possible at usable pressures from the caliber. I'd put that one on your watch list too.

I currently have lots of AA2230 and Alliant Reloder 7 and am set for a long time for powder for 7.62X39.  At one point about 5 years ago AA2230 went on sale at Midway for $12.99/lb and I got 10 pounds the first day of the sale. Still have 6 left !!

Gary

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Maven posted this 19 June 2015

"A 100% density load of IMR 7383 will not over pressure a 7.62X39 SKS but the powder is not likely to develop enough pressure or the correct pressure curve to operate the action of an SKS reliably.”  ...onondaga 

It was with great trepidation that I tested IMR 7383 in the SKS today, but I'm happy to say all went well.  First, a FL sized 7.62 x 39mm case with the NOE 316-160SP-GC (C.E. Harris design) CB seated to 2.125” holds 22gr. 7383 (uncompressed).  Second, although I fired only 3 such loads, all three ejected perfectly and exhibited no signs of undue pressure. That load also burned clean as evidenced by little unburned powder residue and clean case necks & bodies.  Third, mean velocity (n = 3) was 1,389 fps +-26fps.  Needless to say this load needs further testing, with those same CB's seated to 2.215” OAL and perhaps with 21.5gr. 7383 as well.>

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onondaga posted this 19 June 2015

http://www.castbulletassoc.org/forum/view_user.php?id=126>Maven I suggest you don't load this powder below 100% density at your 22gr. 7383 (uncompressed). This is shooting safely for you. Reducing below that is heading toward danger and dirt. IMR7383 is safe to compress. heading carefully in that direction monitoring pressure signs should be productive with the powder. 103% of your  capacity load will likely be the ticket if there are no pressure signs.  22 + 3% = 22.66 gr IMR7383.

Gary

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Maven posted this 19 June 2015

Gary, I was thinking of trying 22.5gr., but when I do, I'll start with new brass.  Also, I've used 7383 at considerably less than 100% loading density in the 7.5 x 55 Swiss and 8 x 57mm Mau. (both 37 - 39 grains), and 55 grains in my .30-06 with little crud build up inside or outside the cases.

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onondaga posted this 21 June 2015

7383 ignites efficiently with a high pressure start from a heavy bullet with a casefull or slightly compressed casefull of the powder. When safe in that application it is a good, very consistent powder with a low ES like Hodgdon Varget in a match shooting load. The powder has a superb consistency when used in it's narrow application parameters.

Lowering the start pressure less than the ideal above with this powder very significantly effects burn efficiency and accuracy results.

A personal worst for me with this powder was a casefull with a 300 gr bullet in a .458 WM. The rifle choked, spit unburned powder and belched a long fireball every shot. accuracy was  50% worse than my good loads for the rifle. I don't shoot heavy bullets in my .458 but I bet a 600 gr bullet would work well with that powder in .458 WM.

Gary

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Maven posted this 23 June 2015

I tested the 22.0- and 22.5gr. loads of 7383 with new Privi Partizan brass and the NOE CB (164gr.) today, but couldn't get a chronograph reading because of the sun. (Wouldn't you know it, not 10 minutes after I put it away, the clouds rolled in.)  What I can tell you is (1) that both loads cycled the action perfectly, although the 22.5gr. charge did so more vigorously. (2) There was neither leading or unburned powder in the bbl., but perhaps as much as 15gr. in the magazine well. (3) Based on only 3 chronograph readings, I estimate the 22.5gr. load produced 1,400 - 1,450fps. (It certainly was less than the 1,529fps I got from 11.8 - 11.9gr. Blue Dot.  It struck the target about 1” lower too.) (4) The extra 0.5gr. seemed to tighten the group as well, but I'm not certain since I'd put the chronograph away* and only had to focus on the target and where the brass landed. (5) The fired brass was essentially clean with only a barely noticeable layer of soot on its surface.

What my Lyman pistol powder measure throws with rotor 10s *When I chronograph my loads, I have to focus on the machine & target (so I don't hit the former), the reading so I can record it, and with the SKS, where the ejected brass lands so I can recover and examine it.  In short, I rarely shoot as accurately when it's in place.

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onondaga posted this 24 June 2015

http://castbulletassoc.org/forum/view_user.php?id=126>Maven

It sounds like you can have some fun with IMR7383, but I wouldn't call the powder you note in your magazine well “good” results. You will have to be meticulous cleaning your SKS when you use IMR7383.

Gary

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Maven posted this 24 June 2015

Gary, The stuff in the magazine well is what accumulated after 30 rounds.  Whether it's the powder of choice is debatable, as I can't get RL-7 or IMR 4198 locally.  (For whatever reasons, RL-7 is becoming a rara avis too.)  However, 7383 does cycle the action, shows little evidence of excessive pressure, and may also prove to be as accurate as 12gr. Blue Dot (sooty cases, partial extraction of fired cases ~2 out of 10 times).

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Maven posted this 04 July 2015

I tried IMR 7383 (no lot no. on my jug, but ~the same burn rate as IMR 4350) once again at 22.0gr. with both WLR standard and WLR magnum primers; 22.5gr. also with both primer types; and 22.7gr. with WLR standard primers only and the NOE 316-160 SPGC bullet (sized to .3155” & seated to 2.125").    Frankly, I'm a bit disappointed since I couldn't get my chronograph to read, which was my main purpose in going to the range today.  Judging from where my rounds hit the target (at least 2” low @ 50 yd.), I estimate the velocity  to be less than that of my 11.9gr. Blue Dot (1,530 +-30 fps), and not nearly as accurate.  Moreover, none of the loads was what I'd call clean burning, as there was always unburned powder left behind in the empties (and sometimes on them as well), the action, and magazine well.  Loads with magnum primers burned cleaner of course, leaving less powder residue behind.  Btw, I removed the gas piston prior to firing so I wouldn't have to hunt for the brass in the high grass, but I think it's absence negatively affected accuracy since groups fired with it in place were not noticeably better.

I'll try 7383 one more time and then seek to purchase a propellant more suitable to the SKS. 

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Maven posted this 16 December 2015

In early November, I was able to chronograph* both IMR 7383 loads v. IMR loads using the NOE 160-SP-GC bullet.  50 yd. accuracy for either propellant was VG with no failures to eject and no bore leading to speak of.  Of the two powders, 4198 was much cleaner burning than 7383, even with LR mag. primers.  The results are below: 

 17.0gr. IMR 4198 + NOE CB + Win. LR primers -> 1,508 +-28 fps (n = 10) 

22.8gr. IMR 7383 + NOE CB + Win. LR mag. primers -> 1,508 +-17 fps (n = 16) 

Btw, 23.0gr. 7383 is as much as the 7.62 x 39mm case will hold and is a compressed load.

 *older, but reliable Shooting Chrony F-1

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Maven posted this 23 August 2016

I tried 22.7gr. IMR 7383 again in my Type 56 SKS earlier today (except for 1/10 gr. less powder, the particulars are largely as stated in post #14) and was very pleased with its performance:  relatively clean burning; impressively accurate; positive ejection of fired cases.  One thing to add:  Today I used both Privi Partizan/PPU brass as well as Red Army brass, which I purchased from Alan in VT on the Boolits site (excellent quality brass & exceptional service).  What's notable, is that the PPU brass loads impacted the target lower than their Red Army counterparts, but no pressure signs were evident in either instance.

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Hamish posted this 27 August 2016

Maven, just noticed this thread. I think I may have to try a case full with a 200 grain bullet in the 300 Blackout. Thanks very much for taking the time to post up.

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Maven posted this 28 August 2016

You're very welcome!

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