Date: Sun, 11 Dec 2005 16:37:36 -0600
Reply-To: FIREARMS Discussion List <
[email protected]>
Sender: FIREARMS Discussion List <
[email protected]>
From: Dan Major <
[email protected]>
Subject: 7.62x39 article contunued
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
SUMMARY DATA ON 7.62x39 - Revised CEH 4-23-90 - This is additional data which was not included in the recent American Rifleman article. I have reloaded thousands of rounds of this 7.62X39 ammunition with both cast bullets and jacketed, and have fired them in the AK and the SKS. I got frustrated with the AK as accuracy of these seems to be generally poor, but the SKS is more reasonable, and is a real bargain these days. It seems the best an AK will do is about 5-6 moa, and the SKS with good ammo will do 3-4, sometimes better.
The gas ports on these guns are larger than they need to be for reliable functioning, so light cast bullet loads down to about 1400 f.p.s. work fine. None of the common cast bullet designs are quite right for this caliber, because the necks are so short, and the groove diameters run large. I designed a bullet and had a custom mould made by NEI of Canyon City, OR, which they identify by the number 155.311GC. This bullet is .92" long and weighs 155 grs. in linotype or about 160-grs. in wheelweight alloy. I designed it with the idea to produce the heaviest bullet which could be loaded effectively without the GC poking into the powder space, and which would be big enough on the forepart to fill the large throats on the AK and SKS, as well as in the 7.62x54R Russian, .303 British, 7.65 Argentine, 7.7 Jap, etc. It has only one grease groove, and a crimp groove .26" from the base. The rear driving band casts .313", the front band .311" and the forepart ahead of the crimp groove is .310", and the ogival radius starts from this large diameter in order to maximize bearing length. The bullet has proven very accurate, and outshoots ball ammo in the SKS or AK with any reasonable load, and in a bolt- action rifle will stay under 1-1/4" 10-shot groups at 100 yards taking bullets out of a 5-cavity gang mould.
The Sierra 125-gr. .308" spitzer seems to be the most accurate of this weight, and shot better than the Hornady 123-gr. .310" and the 150-gr. Spire Points in either .308" or .312", which they make for the .303 British. The popular 150-gr. spitzers intended for the .30-'06 or .308 do not expand at 7.62x39 velocities, but bullets intended for the .30-30 work well. Of these the 125-gr. Sierra JHP flatnose and the 130-gr. Speer FN seem to work the best. I have gotten good accuracy with the 150-gr. Sierra MatchKing bullets in by boltgun of this caliber which I built on a Sako action, but you might consider using match bullets a costly absurdity in an AK or SKS. I also tried some of the cheap surplus 7.62 NATO M80-type bullets, but these shot very poorly, about 4-5" in the boltgun at 100 yds., and almost twice that in the AK, and about 6" in the SKS. I prefer cast bullets for most of my shooting in this caliber, but if I were to buy jacketed bullets the 125-gr. Sierras in either FN or spitzer style would be my choices, with the 130-gr. Speer flatnose .30-30 bullet also strongly in the running, and the 123-gr. Hornady spire point for the 7.62x39 is also OK, as are 150-gr/ .30-30 bullets.
I don't have the pressure gun to work with which I did when at Ruger, but in my experience with several rifles, these loads should be OK. When I did pressure tests with H322 and Accurate Arms 2230 and Hodgdon H335 it appeared you couldn't get enough into the case with a 125-gr. bullet to get into any trouble, and a caseful made a highly satisfactory load. H322 used to be about the cheapest powder around, and works very well in this caliber. I use 28 grs. with a 125-gr. bullet for about 2200, and 25 grs. with a 150-gr. bullet for about 1900. With my cast bullet I use 24 grs. for about 1850, which works very well. Accurate Arms now has their powder AAC1680 which is very similar to the Olin 680 Ball powder, though slightly slower. The best load with 1680 and the 155 gr. NEI cast bullet seems to be around 16 grs. in the SKS, which gave me about 1400 f.p.s., and 3" groups at 100 yds. 18 grs. gives 1630 f.p.s. and about 4" groups in the SKS, with 19 grs. velocity is about 1700 and groups opened up to over 5", which I consider unsatisfactory. I did just two strings with the Olin 680 for comparison with the NEI bullet at 18 and 19 grs., respectively, which gave 1810 and 1930 f.p.s. I would not exceed 19 grs. of Olin 680 with the 155-gr. cast bullet, or 23 grs. with a 125-gr. jacketed one, as these are both full loads. With ACC2230 you can use all the powder the case will hold with a 125- gr. jacketed bullet, about 30 grs., and no problem. With a 155- gr. cast bullet start around 26 grs., up to 28 grs. maximum, for 2050 f.p.s. I have also used IMR-4895 with good results. About 17 grs. is the minimum charge which will function the SKS with a 160-gr. cast bullet, but you can stuff the case with all the powder it will hold and you can't get in any trouble. It works well with cast bullets from 150 grs. up.
As for reloading the Berdan primed cases, it isn't worth the trouble.
Charge Establishment for NEI 155.311GC cast CEH design bullet, WW alloy quench-cast from mould, as-cast dia. .313", tumble lubed in Lee Liquid Alox. No GC used except where noted. Midway cases, Remington 9-1/2 primers, Ctg. OAL 2.20" taper crimped in C-H die from Midway Arms. Test firings in Norinco AKS with 16.4" barrel. H4198 Velocity Remarks (Grains) @ 15 ft. 14.8 1252, 39Sd feeds, ejects OK, but unburned pdr. granules cause occasional failures of breech to close fully. 17.4 1490, 47Sd functions OK 18.5 1578, 31Sd functions OK 20.4 1715, 47Sd function OK, slight leading w/o GC 22.0 1880, 30Sd GC bullet, function OK, no leading 22.6 1909, 27Sd GC bullet, function OK, no leading accuracy decays above this charge.
Charge Establishment for Accurate Arms 1680 propellant in SKS with NEI 155.311GC bullet, as above. Grains Vel. @ 15' ES for 5-shot group @ 100 yds., (cm) 16.0 1422, 21 Sd 4.5 cm 17.0 1629, 25 Sd 7.7 cm 19.0 1710, 7 Sd 11.7 cm Olin W680 for comparison 18.0 1810, 15 Sd no group recorded 19.0 1932, 18 Sd " " " Olin 680 with 122-gr. PS Ball bullet pulled from 101-71 Chicom ammo. 23.0 2381, 11 Sd Midway case with large primer F210 23.0 2332, 14 Sd BELL case with small primer F205 PS Ball for comparison, velocities from SKS with 20.5" barrel Chicom 101-71 2415, 11 Sd East German 04-77 2448, 11 Sd
MANUFACTURER'S CODES FOR 7.62X39 MM AMMUNITION CODE COUNTRY CODE COUNTRY 01 WEST GERMANY A79 SOUTH AFRICA 3 USSR AD INDONESIA 04 EAST GERMANY aym CZECHLOSLOVAKIA 05 EAST GERMANY bxn CZECHLOSLOVAKIA 10 BULGARIA CAVIM VENEZUELA 11 (PRC no serifs) Yugo has serifs 13 CUBA CBC BRAZIL 17 USSR FN BELGIUM 21 POLAND HP AUSTRIA 22 ROMANIA IK YUGOSLAVIA 23 HUNGARY IZ CZECHLOSLOVAKIA 31 PRC Lapua FINLAND 031 PRC NK YUGOSLAVIA 51 PRC (letter N backwards) 60 USSR nny YUGOSLAVIA 61 PRC PMC SOUTH KOREA 71 PRC PMV CUBA 81 PRC PP YUGOSLAVIA 93 NORTH KOREA 101 PRC 141 PRC PPU YUGOSLAVIA 270 USSR PT FINLAND 343 POLAND VPT FINLAND 351 unk. (PRC?) RPR ROMANIA 501 PRC SO FINLAND 539 USSR ZV CZECHLOSLOVAKIA 711 USSR Numeral headstamps containing the number 1 (one) WITHOUT SERIFS are usually PRC.
EAST-BLOC BULLET TIP COLOR CODES: Tracer - Green API - Black tip/red ring API - Black tip/black annulus (PRC) PRC API will have lacquered or copper washed steel case. BRASS CASE WITH THIS CODE and nny headstamp is Yugo proof Analysis of 7.62x39 mm powder from Chinese PS Ball Factory 71, 1983: Is single-base, containing 0.4% K2NO3 flash retardant bulk density .90 grams/cc, cylindrical grains .041 long, .0205" diameter, NOT perforated, diphenylamine stabilizer, compares most closely to IMR4475 in granulation and burning rate.
ACCURACY TEST OF 7.62x39 mm SKS RIFLES BY CEH 1/30/88 Average of four consecutive 10-shot groups at 200 yards, iron sights. Two targets each rifle shot with Yugo M67 123-gr. lead core ball Two targets each rifle shot with PRC 101-71 Type PS steel core Rifle No. Origin Avg. ES No. of Hits on "E" Silhouette 641991 USSR pickup 11.75 33x40 (rifle condition worn/good) If zero had been 1/2 mil left this rifle would have scored 40x40 hits. J8138 USSR pickup 11.38 38x40 (rifle condition worn/good) M3976 USSR pickup 13.77 35x40 (rifle condition worn/good) 15082 PRC 15.16 37x40 (rifle condition excellent) 25636 PRC 12.17 35x40 (rifle in new condition) 01724 PRC 12.72 39x40 (used, VG condition) Avg. six SKS rifles 12.82 36x40 90% hits
RESULTS BY AMMO TYPE: SIX RIFLES POOLED, 12 TEN-SHOT TGTS. @ 200 Chinese PS Ball 12.70 108x120 = 90% Yugo M67 Ball 12.89 109x120 = 90% 25636 RESHOOT 300 YDS. 17.28 29x40 40 rds. PS ball 101-71 This is typical 300 yd. performance for SKS Previous Test of USSR SKS carbine serial no. 641991 by CEH and JBR, March, 1983, average of five consecutive 5-shot groups at 200 yds. Vel.@15' Smallest Largest Average USSR PS 2297 7.50 12.87 10.59 60-K (1950) 31 Sd 10-shot tgts. This USSR PS test shows good agreement with other firings of SKS rifles of 1/30/88, which included this one. Note influence of ammunition quality below: Lapua Ball 2370 3.31 7.50 5.94 (Berdan) Better than typical SKS with PS Ball.
CEH FIRINGS OF AKM FOR COMPARISON WITH SKS AKM Factory 66 #305163 17.25 32x40 (rifle condit. excellent) PRC 101-71 PS Ball shot at 200 yds., typical for AKM and AK47. Previous CEH test of Maadi AKM imported by Steyr for NRA, March, 1983. Average of Five consecutive 5-shot groups at 200 yards. Vel.@15' Smallest Largest Average Lapua Ball 2379 7.20 9.60 8.66 (Berdan) 12 Sd This performance is better than expected of PS Ball in average AKM and AK47, attributable to better quality of Lapua ammunition. Note ammunition comparison with SKS above, refiring the same rifle in Jan., 1988, compared to 1983 results. U.S. Military Specification Mil-C-70760 Ctg. 7.62x39 mm, Commercial Dwg. #12598661 Bullet extraction force: 60 lbs. min. Accuracy: 5.0" max. MR @ 200 yds. Velocity: 2275 +/- 30 f.p.s. @ 78', Sd 30 max. (eq. to MV = 2350 f.p.s.) Chamber pressure: 45,000 psi (Cu) max. avg. Cyclic Rate: 550-750 r.p.m. in AK-47/AKM rifles. Bullet Wt. 124 grs., lead core with copper alloy or gilding metal-clad steel jacket. Primer: non-corrosive Penetration Tests of 7.62x39 mm Ammunition by CEH Oct., 1986. All firings at 50 yds. range against standard CMU ("cinder block")
WEAPON CAL. AMMUNITION TEST RESULTS AKM 7.62x39mm Yugo M67 Block hit end-on, perforated web, bullet lead core broke up and only marked next layer. Chinese PS Block hit end-on, perf. first and steel core second webs, cratered third web, without cracking it. AR-15 5.56 M193 Block hit end-on, perf, first web lead core and broke up, marked 2nd next web M855 Block hit end-on, perf. first and steel core second webs leaving no damage to 3rd web other than deposit of debris. Repeat test of M855 broadside hit gave complete perforation both sides of CMU, spraying witness tgt. 3 ft. behind with fragments, steel core penetrated 3/8" into 1x2 SYP tgt. frame. Garand .30-'06 Ball M2 hit end-on perforated first and 2nd lead core second webs of CMU, heavily cratering third web, and cracking lengthwise.
TYPICAL DISPERSION OF SELECTED SOVIET AND U.S. RIFLES Approximate Extreme Spread for 10-Shot Groups, Estimated from Measured Radial Standard Deviations, (assuming MR as .9xRSd and ES as 3xMR) NRA Master gunners in favorable conditions adapted from U.S. Army APG data, AMSAA Technical Report No. 440 , May 1987. 7.62x39 5.45x39 5.56x45 5.56x45 USSR PS USSR PS US M193 US M855 RANGE: AK-47 AK-74 M16A1 M16A2 (metres) 100 4.8 3.5 2.7 2.7 200 9.6 7.0 5.5 5.5 300 14.4 10.5 8.9 8.6 400 19.6 14.9 12.8 11.9 500 25.0 19.6 17.6 16.0 600 30.6 25.5 23.0 20.4 DOCTRINAL BATTLE-SIGHT RANGE 300 450 250 300 (metres) Firing table for 122-gr. Type PS Ball, GMCS mild steel core BT C7 :.156, Standard Metro, adapted from Soviet and U.S. Army Data Range Velocity Energy Drop Elev. Max. Hgt. (yds.) (fps) (ft.-lbs) (ins.) (moa) (ins.) 0 2340 1483 0 0- 1.5 100 2080 1172 3.5 5 0.3 200 1836 913 14.9 8.2 3.5 300 1606 699 37 12.8 9.9 400 1388 522 72.4 18.5 20.9 500 1190 384 126.5 25.6 38.7 600 1051 299 206.9 34.7 65.9
EFFECTS OF TRAINING AND DOCTRINE ON INFANTRY RIFLE EFFECTIVENESS U.S. doctrine is that the M16 rifle be carried habitually with the sights set to the BSR unless there is a need to set the sights for some other range and there is time to do so. American GI's are taught to aim at the center of mass of the visible target at all times, which centers the densest portion of the round to round shot dispersion in the center of the target, to maximize hit probability. Soviet doctrine is to use a bottom of target point of aim with the sights set at the BSR at ranges up to 300 metres, and to set the sights for the estimated range at longer distances. In operational situations the type and magnitude of other system errors cancel any effect of wind deflection upon hit probability for the average soldier. The intrinsic single-shot round-to-round dispersion of the AK47 is larger than the newer AK74, but both Soviet rifles have a larger intrinsic RRD than either the M16A1 or M16A2. These differences are not meaningful in most operational combat situations because stress is the great equalizer. If the shooter's error approaches the worst hitting performance seen in peacetime field experiments the differences in being able to hit an "E" silhouette target caused by differences in inherent weapon accuracy are wiped out. If effective range is gaged by single-shot hitting performance of average soldiers in combat situations, the AK47, AK74, M16A1 and M16A2 have almost no difference in performance. In US Army testing of the AK-74 rifle it was found that the time to hit was the same for the AK-74 and M16A1 for target exposure times of 2-3.5 seconds, but that the muzzle-break-compensator of the AK-74 was an aid to improving hit probability at close-range targets with burst fire. The third round in a burst from the M16 seldom if ever hits anything and is nothing more than a waste of ammunition. Personnel should be taught to use two-round "double-taps" for close range engagements within 50 yds. Beyond 50 yards rapid semiautomatic fire is far more effective than any type of automatic fire, in being able to obtain hits, as well as in conserving ammunition.
(Just kidding, I HAD to get one dig in!)
