308 SMK Load

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Performed a ladder test yesterday using and I think I found a good load.

Remington 700 sps varmint 26" 1:12

Sierra MatchKing 168gr
H4895

41.5, 42 and 42.5 @ 100 yards were grouped at .426"

I will probably load 42gr

I was curious to see what others results were and if my load was in range with others.

 

[backwoods83]

I use 47grns of Varget and a cci br2 primer under a 168SMK at 2.830" but only in Winchester brass that is neck sized. I have also used the same combo with hrndy 178 bthp match at 2.904" and pulled off a .271" 7 shot group. I only use H4895 under 155 and smaller pills.

 

[TikkaShooters]

What was your es/sd? The more consistent load should be used.

 

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what is es/sd?

 

[TikkaShooters]

That is your extreme spread and standard deviation.

A load that performs well at 100 that has high es/sd numbers will perform poorly as you reach further out.

This is why it is not only important for a load to be accurate at short range, but consistent enough in velocity to be accurate at long range.

 

[Bart B]

A load that performs well at 100 that has high es/sd numbers will perform poorly as you reach further out.

This is why it is not only important for a load to be accurate at short range, but consistent enough in velocity to be accurate at long range.

'Tain't necessarily so.

Years ago, when several of us developed the load for Sierra's 155-gr. Palma bullet in the .308 Win. case, the load that the lab tested and produced the lowest spread in muzzle velocity and peak pressure was the least accurate of a couple dozen loads tested. The one we ended up using had a little less than average numbers for velocity and pressure, but it was the most accurate. Shot well under 4 inches at 600 yards in spite of 3/10ths grain powder charge weight spread.

Lake City Arsenal's M852 match ammo with Sierra 168's had about 42 grains of IMR4895. They used a charge weight that produced best accuracy within pressure and velocity specs. And best accuracy didn't always have the lowest spreads in averages for these two things.

 

[TikkaShooters]

I was not referring to maximum velocity for pressure vs. a lower velocity for pressure reasons or how it effects accuracy. Every gun is different and prefers a certain velocity/burn rate/bullet combination.

If you es/sd are high, you will see vertical stringing the further out you go.

If a bullet is traveling 50fps slower at the muzzle than the bullet before it, it will hit lower. At shorter distances this is less prominent. Once you extend past a certain point for any given powder/bullet combination, the group will open up and vertical stringing will occur.

 

[Bart B]

Every gun is different and prefers a certain velocity/burn rate/bullet combination.

That's one of many myths about rifles and ammo. It stems from folks shooting to few shots per test group as they shoot rifles off their shoulder as it rests atop bags or something on a bench. I can't think of a worse way to evaluate a heavy recoiling (.308 Win. or larger) rifle for accuracy.

The load I mentioned above shot well under 4 inches in several dozen match rifles; different chamber and bore dimensions. Over half of then shot under 3 inches at 600 yards.

Federal .308 Win. match ammo with 168's shot under 4 inches at 600 yards in military M14NM's and 7.62 NATO M1's for years.

I've shot the same .30-.338 Win. Mag. Loads in one Douglas, one Obmeyer and one Kreiger barrel and the same .308 Win. loads for bullets of 155, 168, 180, 190 and 200 grains wearing out five Hart, 3 Kreiger and two Obermeyer barrels; all with different bore and groove diameters. And I've worn out 3 or 4 Springfield Armory government arsenal 7.62 NATO barrels in Garands with all sorts of match ammo. All shot very, very accurate.

Others have shot the same load in several barrels for the same cartridge that easily equalled what benchrest rifles shoot at long range.

 

[TikkaShooters]

If a benchrest shooter shot a 4 inch group at 600 yards, his next shot would be at his gunsmith.

There is good accuracy which is what you are referring to, and there is great accuracy, which is what I was referring to.

Each person shoots for a different reason and needs a different level of accuracy. Me, being a perfectionists, load for less than 1/4 moa accuracy at any given range.

The benchrest record for 1000 yard comp. is a 10 shot aggregate of approximately 1.5 inches. This is a timed match in which these shots must shot very quickly resulting in more human error.

In the precision shooting crowd, the numbers you list would be completely unacceptable.

 

[Bart B]

The benchrest record for 1000 yard comp. is a 10 shot aggregate of approximately 1.5 inches.

The NBRSA and IBS 1000 yard 10-shot records are larger than that. Please let me know what discipline it was fired in.

Note that record group was/is the smallest one fired in competition. All others are larger. If that rifle's barrel has shot 200 ten-shot groups at 1000, that record one is only half a percent of all groups fired. Find out what the largest group is that it fired. Then we'll know what size groups it shoots "under." Betcha two fired cases and 10 spent primers it's at least 6 to 7 inches. That's about 2/3 MOA; same as I mentioned with those .308 Win. rifles shooting under 4 inches (2/3 MOA) at 600 yards.

That should be an easy job for a "perfectionist."

Hint: Check the 6- and 10-group aggregate records then add about 20% to them. This is what one rifle shot "under" that day to set the record. All the other rifles shooting those agg's prior to that record shot under larger sizes.

 

[backwoods83]

I'm going to go with Bart on this one, that would be just over a 6.5" group at 1K. The 1.5xx" group was a 5 shot record light gun done by Bill Shehane with a 6.5 Shehane (aka 6.5x284 imp) and has been taken from him by Bruce Baer with a .998" 5 shot record with a 308 baer, very similar to a 300 ackley magnum, on the other hand I have seen the same guy with the same gun shoot 14-16" groups as well, lots of things come into play. I like my es to be single digit as well but I'm not going to shoot a single digit es load that groups 1.5moa either.

 

[Bart B]

The 1.5xx" group was a 5 shot record light gun done by Bill Shehane with a 6.5 Shehane (aka 6.5x284 imp) and has been taken from him by Bruce Baer with a .998" 5 shot record with a 308 baer,....

Any rifle can shoot a tiny knot once in a (great) while.

Best example of several shot in one test was explained to me years ago. I'd called Lake City Arsenal about a problem a military rifle team I was on regarding a particular lot of 7.62 NATO M118 match ammo. The ballistics engineer there explained the issue and that was good enough for me. He later said that in a recent test of M118 ammo, a new employee was being shown how they did accuracy tests. Shooting a couple hundred shots from a Picatinny rail gun at 600 yards, these two went down to check the group. The group was about 8 inches in diameter for all shots fired. The new man said words to the effect of: "Look at all those 1/2 inch 5-shot groups down here 600 yards from where we shot 'em." So the old engineer replied: "Yes; there's dozens of them. Too bad they're not all at the same place."

 

[TikkaShooters]

You guys completely missed the point of my advice to the original poster. Out of three loads they ALL shot .5 moa or better. Common sense dictates that if they are all accurate to a similar degree take the more consistent load. I never stated that he should sacrifice accuracy for es/ds numbers

 

[Bart B]

What was your es/sd? The more consistent load should be used.

J-man, we probably thought you meant the es/sd that was the most consistant was the one to use for best accuracy. If you meant the best accuracy as being the most consistant, then that's different and a good thing to do.

The benchrest record for 1000 yard comp. is a 10 shot aggregate of approximately 1.5 inches. This is a timed match in which these shots must shot very quickly resulting in more human error.

I don't think shooting 10 shots very quickly results in much human error if the rifle's fired in free recoil. And that's how most benchrest rifles are fired these days; especially the 20-pound and heavier ones shooting the big .300's.

Here's some examples....

That 155-gr. Sierra bullet load for the .308 Win. I helped develop was loaded on two Dillon 1050 progressives. One sized down the new case necks at one station, opened up at the next station with an old Lyman expander die to have a medium grip on the bullet when they were seated and seated a Fed. 210M primer in the last station. The second 1050 metered 45.3 grains of IMR 4895 (3/10ths grain spread) at one station and seated the bullet and another one. 23 rounds at random were taken to a 600 yard test range where the Win. 70 based Palma rifle was clamped in a machine rest; it had a 3 point suspension and was perfectly repeatable within 1/50th MOA. Two or three sighters were fired to center the group on a test target. 20 shots for testing were fired, each about 20 seconds apart. All 20 went into 2.7 inches at 600 yards. A picture of that group's in a fall 1991 issue of Handloader magazine. Compare that group to the current 600 yard benchrest aggregate records.

A friend fired several 10-shot groups at 600 yards using bullets that had been spin tested for balance; only those with perfect balance were used. All cases were full length sized and fired in another Win. 70 with a Hart barrel. They all were under 1.5 inches; smaller ones were under an inch. All shots fired 20 seconds apart. Another test with the same timing, rifle and ammo had 40 consecutive shots fired into 1.92 inch.

Shooting fast has the advantage of getting ones shots off when the wind's constant (zero is preferred). Good rifles don't change point of impact as their barrel heats up. Just get the shot off within 10 to 15 seconds of chambering it so the powder doesn't heat up enough to make the shot go high.