(Notice how I put "Hot Cor" and "OCW" right next to each other in the title? I hope my arch rival won't slam me too hard for that... )

I've just returned from the range, having tested Speer's 150 grain "Hot-Cor's" in my .308 win chambered rifle. The powder used was RL "Reloder" 15. Cases were virgin Winchester brass, and the only preparation was neck sizing in Lee Collet dies, and slightly chamfering the case mouths. Primers were Remington 9 1/2s.

Optimal Charge Weight load testing proceeded with the following charges: 45.8, 46.2, 46.6, 47.0, 47.4, and 47.8 grains. The last two graduations were above most published maximums, and they were only fired after confirming that the preceeding charge did not exhibit pressure signs.

All three shot, round robin groups came in at MOA or under, except for the 47.8 grain charge, which strung vertically a bit over MOA.

The harmonic whip of my Savage 10FP's barrel seems to move in a vertical pattern (preferred, actually) and the muzzle velocity variations usually make vertical patterns when velocities aren't consistent.

Anyway, the OCW was determined to be 46.3 grains of the RL15. The 45.8, 46.2, and 46.6 grain groups, once triangulated, showed a common point of impact at 100 yards. The higher charges were definitely faster--judging only from their raised points of impact, but they were very sporadic with where they wanted to group.

The 47.0 grain charge shot a *tiny* 3/8" three shot group, due I believe to favorable barrel harmonics. The 46.6 and 47.4 grain charges grouped well away from this small 47.0 grain group, so the 47.0 grain charge would be too pressure sensitive for reliable MOA accuracy.

The overlaid group size for the 45.8, 46.2, and 46.6 grain groups was 7/8"--not bad for a "hunting bullet."

I would normally expect the groups to tighten as the OCW zone is approached, and then spread out as the OCW zone is departed from. That was the case here, with the 46.2 grain charged group coming in at 1/2 MOA. All three of these groups tended to string slightly vertically, and again I attributed this to their following the harmonic whip of the muzzle.

Since the 46.2 and 46.6 grain charged groups were practically identical in their points of impact, I decided to declare 46.3 grains the OCW, which is a tenth of a grain above the tested charge.

I'll measure velocity in the spring, but around 2800 fps would seem to be in the ballpark for a 22" barrel.

The Speer Hot-Cor's are of course not target bullets, and will likely take a backseat in accuracy to match bullets, or probably even Sierra's Gameking bullets (the hunting bullets that think they are match bullets ), but for most of us who would use the .308 for deer and similar game hunting, I believe that 46.3 grains of RL15 behind Speer's 150 grain Hot-Cor bullet will be powerful hunting round, with better than average accuracy. Folks who use the Hot-Cor's routinely report excellent terminal performance on game animals.

I used an OAL of 2.785" for this test, and will likely "depth tune" the load to take advantage of the harmonic node at a later time.

Considering that the brass was virgin stuff, and not match prepped in any manner, and considering that the load has not been depth tuned to the test rifle, I think the combination should prove to be a winner in the majority of .308 chambered rifles. After preparing the same recipe in fire-formed, prepped brass, and optimizing the seating depth, I think I'll be looking at a very consistent 1/2 MOA hunting load.

Work up from below the 46.3 grain charge, of course...

Take care,

Dan Newberry
green 788

Dan I just recently did some expansion testing and posted the results for the new 225 grain 338 caliber Hornady SST's, however, I also did test the 150 Speer Spitzer Hot-Cores as well out of curiousity. I shot 2 rounds into soaking wet phone books at 100 meters and they retained 79% and 76%. The cores were still tightly bonded to the jackets and the bullets had the classic mushroom shape. I shot them out of my 308 at about 2850 fps. Good Luck, Steve

PS: In my rifle, the 150 Speer bullets actually shoot better than the Sierra MatchKings!! I recently rebarreled my 308 to shoot 175 SMK's using a 1 in 10 twist stainless barrel but the Speers still shoot better groups at 200 meters! Haven't tried 155 or 168 SMK's I think they also are a decent hunting bullet too from the results of the expansion tests. Steve

Steve, that is encouraging news... The Hot Cores do seem to have more accuracy potential than I would have thought.

An added plus here is that at my local Walmart, I can get the 150 grain Hot Cores for 12 dollars for a box of 100.

I will test the load at 300 yards next, and see how things go...

What powder and charge did you use to get the 2850 fps?

Thanks,

Dan

For Comparsion reason my Nosler Manual list 46.0 or Reloader 15 with 150 grain bullets in the 308 Win.

Other powders that should be excellent is H322 at 42.0 and IMR 4895 at 47.0

Hi Dan: I use 49.0 grains of 748, Fed 215 primer, WW cases, 150 Speer Spitzer and seating to an OAL of 2.750". I have used this load for years in a variety of rifles and found it to be very accurate. Velocity averages about 2850 in my rifles with a 22" barrel. Steve

"I have used this load for years in a variety of rifles and found it to be very accurate."

You have a very resilient and consistent load recipe there, no doubt about it. These recipes are not harmonic whip dependent--they ignite and accelerate with such uniformity that it doesn't matter where on the harmonic whip they are released, they just group. This explains why these recipes work well in various rifles. I would imagine if you were to run the OCW test on that powder and bullet, you would find that you've got an optimized charge of W748 there...

Thanks for sharing the data. I've made a note of it.

Dan

Thanks, Gus...

We know that barrels vibrate from the impact of the cartridge being fired, and the bullet traveling down the barrel. This of course means that the muzzle will trace out a repeating pattern while the barrel is in vibration.

From the muzzle end, the pattern is usually shown as an elongated figure "8". While every barrel will vibrate differently, the pattern of vibration will be repetitive--so long as there are no bedding issues that would create inconsistent vibration patterns.

Conventional load development finds most folks beginning with a preconceived overall length of the cartridge (distance to lands), and then altering powder charges until a group tightens up. Usually, this will work out well for that one rifle so long as nothing changes the harmonic whip of the barrel (like forearm tension, etc.) and so long as nothing changes the pressure characteristics of the load recipe (like odd brass cases, odd primers, outside temperature, etc.). If these "stars remain aligned," this load will shoot well.

Normally, those conditions can't all be counted on to remain constant, hence occasional flyers, or "bad days at the range."

Anyway, back to the harmonic whip. Ideally, the bullets will exit the muzzle on a slow portion of the harmonic whip. The slow portion occurs when the muzzle is at one extreme or the other, just about to change directions. This will allow bullets which do not have tight velocities at the muzzle to nonetheless group well, since they are being set to flight in the same tiny point in space.



Now. If your load is very consistent in ignition and acceleration, it will not need the "crutch" of the static node of the harmonic whip. It will be consistent enough so that even though the bullets are exiting in a "straighaway" of the harmonic whip, they still get spit out of the barrel in the same tiny point in space. You may see an "arcing" or stringing pattern on the target, but this line will be very short (MOA or under) with a good load.

You can of course make a good load even better by "depth tuning" it to your individual barrel. Then you'll have a load capable of very uniform ignition and acceleration, which also has the added benefit of a friendly harmonic node. The short "arcs" will then become clusters.

I'm not always the best at explaining things, so please--anybody interested--let me know if this makes no sense and I'll give it another try...

Take care, and thanks for the read,

Dan

SteveB -

quote:

---

Haven't tried 155 or 168 SMK's I think they also are a decent hunting bullet too from the results of the expansion tests.

---

Gads, man. What's wrong with you? Don't you know MK's shouldn't even be considered as a hunting bullet?

I see you're fairly new here, and, in case you're wondering what all this is about:
A. Check out http://www.serveroptions.com/ubb/ultimatebb.php?ubb=get_topic;f=6;t=003036;p=1
B. I'm joking. MK's actually work pretty well as hunters.

R-WEST

Can this method of load development be used at a distance of 100 or 200 yards and still be conclusive?

Fetchmax,

Do the initial OCW testing at 100 yards--no farther. Otherwise, wind will become a factor in the shot locations and screw up your triangulations.

Once you have confirmed the OCW zone, and decided on the tentative OCW recipe, you can then test the load at the extreme range at which it will be used.

You can go to my website on page one and find the instructions there. Link to my site at the bottom of this post...

Thanks for the interest.

RWest,

You will be interested in the following text from Adrian Gilbert's book "Sniper." The text appears in a section discussing terminal ballistics tests of different bullets used in the craft.

"The U.S. Federal Match Sierra bullet (used in the military sniper's M852 round, now replacing the M118) begins to tumble after only two inches and then breaks up to carve a large permanent would track, before dividing into two seperate channels of twenty-two and sixteen inches in length."

Now I don't know about you, but that does sound pretty wicked to me!

Dan

R-West: I didn't read my comments properly. I am well aware that the 155 and 168 SMK's are not for hunting and are match bullets only. Sorry about that. Steve

SteveB...RWest is only kidding...there was once a thread...hell it turned into a rope.. that rivaled "War and Peace" in length. he provided a link but dont go there unless you have ulimited time, patientce and internet access....
Thanks for the info Ive used W748 for lighter projectiles and will try it with the 150s
Dave

Thanks Green 788 for the reply. As soon as the shoulder heals up I will try this process. Yes you can reload with one arm.

SteveB - Dave's right. I was yanking your chain. The rope actually is a pretty good read, if you've got a few hours (days?) to kill.

Actually, I was trying to get another MK controversy going - hey, my range is BURIED under snow, and I won't be able to shoot for months, so I've got to find something to do to pass the time. There are a number of dedicated MK users in here that will vouch for their effectiveness on game, and, probably, an equal number totally against their use.

Dan - Is that the 168 grain MK they're using in the sniper round?

R-WEST
(Average snow depth on shooting range as of 2-19-03 = 8 feet )

R, The M852 uses the 175 grain SMK, and a healthy charge of RL15. It used to be 42 grains of IMR 4895, but Alliant now has the contract.

I'm not certain of the actual charge of RL 15 they are using, but I have heard that the charge has been reduced from the original some due to pressure problems.

Dan

To my knowledge its M118LR that replaced M118.

M852 continues to be loaded with the Sierra 168 projectile. M118LR aka AA11 is loaded with the 175 Sierra.