7.62x39, AA 1690 and the Hornady V-Max

[tkcomer]

7.62x39, AA 1680 and the Hornady V-Max

I know everyone's gun is different, but I thought I'd ask. First off, the gun is an AR-15 with a 16" barrel. I tried my first load with the .310 Hornady 123gr V-Max and 23.6grs of AA 1680. Shot around a little under 2" at 100 yards. Now I'm trying to figure out what direction to go for my next load. Do you get better results loading the V-Max hotter? Slower? In the middle? My Hornady data doesn't list the V-Max bullet specifically. Just a max of 23.9grs for their 123gr .310 SP and FMJ bullets. AA list a max of 25.5grs for SPR 125 SP .311 bullets. Speer has a start load of 26grs of 1680 for their .311 125gr bullets. Max is 28.0grs. Quite a gap there on load data. The Hornady data is what's making me fearful of loading hotter. And hotter may not be better. So what are people that have tested this combo using?

 

[Beagle-zebub]

Not to get the thread off topic, but why can't I find that bullet on Hornady's website? And do stores stock it anyway?

 

[tkcomer]

If you can catch it in stock, Graf & Sons has them.

 

[R.W.Dale]

AA list a max of 25.5grs for SPR 125 SP .311 bullets. Speer has a start load of 26grs of 1680 for their .311 125gr bullets. Max is 28.0grs. Quite a gap there on load data.

AA1680 check your thread title

I've used the 28grn load in bolt actions and even then brass indications show this load in all likelihood to be too hot. IIRC this load had been throttled back in later Speer manuals

For the AR15 26.0grs is as high as I'm willing to go again because of brass condition.

But I use the much much stouter small primed cases. When using large primed cases the high pressure indications I mention become extremely pronounced. As in brass got tossed after 1 loading.

 

[Mikee Loxxer]

My understanding is that the .310 Hornady 123gr V-Max has been discontinued.

 

[tkcomer]

Hey krochus. You've helped me before on getting started on loading this caliber. Brass condition is an important factor as it's not cheap or abundant. Did your bullets get more accurate as you increased powder charges? I'm not a 'max' kinda guy, just looking for directions. The Sierra max for their 125gr bullet is 24.6. I thought of bumping up to 24.5gr just to see what happens. Just didn't know if performance degraded at higher velocities. I'm a paper puncher only, so higher velocities for hunting doesn't interest me if accuracy degrades. Then again, my scope is not really a target scope. Leupold 3X9 compact scope. Crosshairs are a little too thick for "precision" work.

 

[R.W.Dale]

Did your bullets get more accurate as you increased powder charges?

With both the AR and the bolt gun accuracy was pretty stable all across the velocity spectrum from start loads to max with a slight edge going towards the bottom end of the load development.

Here's a pic illustrating how case expansion increased in new lapua cases with a corresponding increase in charges



Of course YMMV

 

[tkcomer]

That's kinda what I've run into with these heavy barrel guns. If you have a good bullet, doesn't seem to make much difference what load or powder you use. The "squirrelly" ones on the other hand can use tuning.

 

[steve4102]

Lyman 48, Max 25.7gr
Hornady #7 Max 23.9gr
Sierra #5 24.6gr
Speer #13 28gr
Accurate Powder 25.5gr

Me, I shoot 26.5gr of 1680 in my Ruger Mini-30 with 125gr Nosler BT. I have gone as high as 28gr, but that's too hot.



Here is what Quickload has to say about 1680 and the VMax. I know QL is only a tool and should be used with caution, but I have found it to right on the money in my 7.62x39 with all powders I have tested.

Cartridge : 7.62 x 39 (M43) Russ.
Bullet : .310, 123, Hornady V-Max 3142
Cartridge O.A.L. L6: 2.190 inch or 55.63 mm
Barrel Length : 16.0 inch or 406.4 mm
Powder : Accurate 1680

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-20.0 67 20.80 1793 878 22800 4634 79.4 1.213
-18.0 69 21.32 1836 920 24161 4798 80.7 1.185
-16.0 70 21.84 1878 964 25599 4961 82.0 1.157
-14.0 72 22.36 1921 1008 27106 5123 83.2 1.131
-12.0 74 22.88 1964 1053 28686 5284 84.3 1.119
-10.0 75 23.40 2007 1100 30350 5442 85.5 1.090
-08.0 77 23.92 2050 1148 32113 5598 86.6 1.063
-06.0 79 24.44 2093 1196 33981 5752 87.7 1.036
-04.0 80 24.96 2136 1246 35962 5903 88.7 1.010
-02.0 82 25.48 2179 1297 38062 6050 89.7 0.985
+00.0 84 26.00 2223 1349 40289 6193 90.7 0.959
+02.0 85 26.52 2266 1402 42652 6333 91.6 0.935
+04.0 87 27.04 2309 1456 45160 6468 92.5 0.911 ! Near Maximum !
+06.0 89 27.56 2352 1511 47824 6598 93.3 0.888 ! Near Maximum !
+08.0 90 28.08 2396 1568 50655 6723 94.1 0.866 ! Near Maximum !
+10.0 92 28.60 2439 1625 53666 6843 94.9 0.845 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 84 26.00 2344 1500 47317 6419 96.4 0.893 ! Near Maximum !
Data for burning rate decreased by 10% relative to nominal value:
-Ba 84 26.00 2076 1178 33542 5749 82.5 1.041

Understand QL runs the 7.62x39 at 51,488PSI which is more in line with your AR, while SAAMI lists Max pressure at 45,000PSI.

 

[tkcomer]

Thanks for the info. I'm thinking of loading two 10 round batches. 24.5grs and 22.5grs and see if there is any change in groups. I like to fire 10 round groups to see where the gun actually stands. I also tried some 124gr Golden West Brass bullets with the same 23.6grs, but my first load didn't really do much better than some of the mil surp ammo I have. Gun seems to tighten up the hotter it gets. The weather has been absolutely crappy every day I'm off the last several months. I've been itching to get out, but it's been windy every day I'm off.

 

[rotorman1]

7.62 x 39 Using VMAX 110 grain .308

I have been using the 110 grain .308 VMAX in the 7.62 cartridge that calls for the .310 diameter bullet. You can set your dies to set the neck just a little tighter to shoot the .308 VMAX round. I find it does very well in my AR15 7.62 x 39 with a 20" barrel. It gives .002 less friction on the way out and down range.

I load it up with the AA1680 28 grains. There is still plenty of room in the cartridge and it can take it but I am hanging at the 28 grains for a while.