7.62x39 for deer/hogs?

Here's a post I made several years back over on the "boolits" forum.  You may find some useful information in it appropriate to the topic of this thread.

LMG

 

Junior1942’s 7.62x39 loads

During the latest thread on LeveRevolution Powder Junior1942 PM’d me asking about the 30-30 testing I had done with the RCBS 30-180-FN and that powder.  He asked about the test and was trying to correlate the psi’s from that test to the 7.62x39 for possible use in his Yugo SKS.  He primarily was interested to see if the LeveRevolution powder would give him a bit better performance under his COWW cast bullets which weight 197 gr.  I suggested there was no sense trying to correlate when I could pressure test in the 7.62x39 also.  I suggested he send some bullets and the data for his other powder loads and I would pressure test those also.  Junior thought that was a great idea.  He asked how many bullets?  I told him a hundred minimum. 

Junior scrounged around and found about a hundred (104 to be exact) he had already cast and said he’d cast up some more and send ’em if need be.  He said a few were wrinkled.  Told him they’d be fine for the initial LeveRevolution work up as we were interested there was the psi. I got the bullets a couple days later.  They were sized at .314, had Hornady GCs and were lubed with LLA.  The BHN measured 11 – 12.  I proceeded to check out the Mini Mk X Mauser I would use for the test.  Unfortunately, the strain gauge had partially cracked for some reason.  It hadn’t been used in over 2 years and the change in location, temperatures and humidity are my guess why.  Called the company to order some more gauges and they would take about 6 – 7 weeks.  Told Junior and he was a bit down over that.  However, in about 2 weeks a package showed up with the strain gauges. 

I PM’d Junior and told him I was ready to test and asked a couple clarification questions about his standard loads.  I didn’t hear back from Junior and just assumed he was away or busy.  I did not know he had gone to the big range.  I proceeded with the test and will post the results here…..for Junior…..rest in peace, may the sun always be to your back, the wind in your face and all your shots go true.

Test rifle; Interarms Mini Mk X

Caliber; 7.63x39

Bore; .301

Groove; .311

Barrel length/twist; 20”/1-9.5”

Sights; Bushnell 4X scope

Test equipment; Oehler M43 PBL

Range; Sara Park, Lake Havasu City, AZ

Test range; 100 yards, solid cement benches

Rest; Hoppe’s front and leather sand bag (rabbit ear) rear

Test shots; due to limited number of bullets not all test strings had 10 shots.  Some had less but not less than 7 shots.  The LeveRevolution psi workup had 2 shots per powder charge.

 The test was conducted on two separate days early in the mornings.  This gave the least heat (this is the desert with daytime temps running 105 – 115) at daybreak (85 – 90) and the least wind.  Juniors’ standard loads and the LeveRevolution psi work up was conducted on the 1^st day along with a LeveRevolution psi workup with a 175 gr C314041 cast bullet of my own.  The second day was the test of 3 loads of the LeveRevolution under Juniors 30-180-FNs and 3 loads under my own C314041. 

The 1^st day’s tests;

Reference ammunition test;  The CIP Pmap (Maximum Average Pressure) for the 7.62x39 cartridge is 51,500 psi (piezo-transducer or strain gauge).  Three factory loads were tested to set a base line for the mini Mk X.  

Wolf Factory FMJ

Velocity; 2498 fps

Psi(M43); 46,400

Accuracy; 5.4”

Herter’s Factory FMJ

Velocity; 2549

Psi(M43); 46,100

Accuracy; 3.3

 

Wolf Factory HP

Velocity; 2581 fps

Psi(M43); 46,700

 

Cases; IMI 7.62x39

Primers; CCI 200

Bullet; 30-180-FN (197 gr)

Cartridge OAL; 2.24 (fit the test rifle magazine and my Russian SKS and fed fine from both) which put the top of the GC right at the case neck.

 

Crimp; Roll under the 3^rd drive band

Junior used 3 different powders for his standard loads; Varget, H4198 and surplus 4895.  He sent 3 loads for the Varget and 4895 to test and 2 for the H4198.

Varget loads;  Junior sent 3 test loads for Varget powder; 23.3 gr, 24.7 gr and 26 gr.  Junior stated the 26 gr load was compressed and it was. 

23.3 gr;

Velocity; 1608 fps

Psi(M43); 27,200

 

Accuracy; 2.1” (7 shots)

24.7 gr;

Velocity; 1700 fps

Psi(M43);  30,300

Accuracy 1.78 (8 shots)

 

26 gr;

Velocity; 1778 fps

Psi(M43); 35,100

Accuracy; 4” (8 Shots)

 We see here the RPM Threshold of these components is between 1700 fps and 1778 fps.  Accuracy went from very good at 1700 fps and 128,800 RPM to poor at 1778 fps and 134,700 RPM.

Junior specified two loads for H4198 powder; 21.3 gr and 22.7 gr. 

21.3 gr;

Velocity; 1820 fps

Psi(M43); 42,200

Accuracy; 4.9” (8 shots)

 

22.7 gr;

Velocity; 1925 fps

Psi(M43); 50,700

Accuracy; 7.5” (8 shots)

 With these two loads of H4198 we see higher psi’s and velocities and poor accuracy.  Both loads exceeded the RPM Threshold for these components.  The RPM was 137,900 and 145,900.  The 22.7 gr load also came very close to the CIP Pmap.

Junior specified three loads of surplus 4895; 23.4 gr, 24.5 gr and 24.7 gr.  Hard to say how close our different lots of 4895.  I have two lots and used the one that is closest to IMR4895 in burning rate. 

 23.4 gr;

Velocity; 1706 fps

Psi(M43); 32,300

Accuracy; 3.3 (8 shots)

 

Note; comparing the accuracy with the Varget 24.7 gr load we see the Varget load is more accurate ate very close to the same velocity.  Note however, the Varget load has the lower psi meaning the time/pressure curve was slower.  We see that in the pressure traces and in the “Rise” data.  The 4895 load reached pressure in 129 microseconds while the Varget load took 144 microseconds.  Seemingly not much of a difference but when pushing the RPM Threshold the devil is in the details. Top trace is the 4895.

24.5 gr;

Velocity; 1767 fps

Psi(M43); 35,200

Accuracy; 4.8” (8 shots)

24.7 gr;

Velocity; 1778 fps

Psi(M43); 35,800

Accuracy; 4.5” (8 shots)

 Junior’s chronographed velocities were about 80 fps less than the ones I recorded.  The velocities I list are corrected to the muzzle and different rifles were used of different actions.  Additionally, the lot to lot variation of the powder used and I was testing in 85 – 90+ degree temps all combine for the differences.  For what Junior was looking for (a “smack down” hog load for 100 yards or less) his Varget or 4895 loads would have been fine. 

 LeveRevolution Powder with the 30-180-FN at 197 gr in the 7.62x39

 I did a “workup test” using LeveRevolution powder. What I do is usually load 2 cartridges (sometimes just one) of increments from a start to a projected “max” load.  I used to call this “ladder testing for velocity and psi” but too many confused this with the “ladder test” commonly used for working up loads.  What I do in this initial psi/velocity testing does not consider accuracy at all.  My testing is concerned with velocity and psi.

With LeveRevolution powder I worked up from 23.5 gr to 28.5 gr in 1 gr increments.  28.5 gr was at 105% load density with the RCBS bullet.  Velocities ran from 1554 fps to 1924 fps with psi’s from 20,100 to 36,300.  Knowing the RPM threshold was between 1700 fps and 1750 fps with the other powders I loaded 25, 26.5 and 27.5 gr looking for velocities from the mid 1600s to the mid 1800 fps.  The idea was to see how far the much slower burning LeveRevolution with its radically different time/pressure curve would push up the RPM Threshold. 

25 gr;

Velocity; 1668 fps

Psi(M43); 22,400

Accuracy; 6” (7 shots)  and very poor.  There was soot blown back the expansion ring on the cases indicating poor breech sealing.

 26.5 gr;

Velocity; 1771 fps

Psi(M43); 26,500

Accuracy; 2.4” (9 shots) no soot on cases.  Accuracy definitely improved.

27.5 gr;

Velocity; 1843 fps

Psi(M43); 28,700

Accuracy; 2.65” (9 shots) definitely pushed the RPM Threshold up as RPM is 139,700.  28.7 gr is worth a try but alas I am out of the RCBS 30-180-FN bullets………note on the target the 1^st and 2^nd shots were right at the bottom of the target I was using.  To make sure I didn’t lose any shots off target I moved the scope elevation up 3 moa.  Those 1^st two shots would have been in the group. 

 

This definitely should be the better “smack down” load in the SKS that Junior wanted.  Graphing out the psi at the gas port shows a projected 8000 psi which is less than with the different Russian made factory 7.62x39 ammunition.  I would have tested this load in my own SKS but again, I am out of the bullets!  Perhaps Junior is hunting with this load already!  I sure hope so……and I’m sure he wouldn’t mind me sharing with all of you.  That’s the kind of guy Junior was.  He loved to share here and on his own web site.  I will miss Junior……….