Range Report Velocity VS Accuracy Question

[AKAce]

Savage, .260 26"

I have come up with 3 "Accuracy" Loads
All Data was Averages of Multi <span style="font-size: 8pt">Groups</span>

142 SMK's

43 Grains of IMR 4350 .39's @ 100, .59 @ 200. <span style="font-style: italic">2728 FPS</span> ES=16 SD=6 <span style="font-weight: bold">28.75 MOA @ 1000</span>

45,5 Grains of 4831 SC .38's @ 100, .58 @ 200. <span style="font-style: italic">2664 FPS</span> ES=21 SD=7 <span style="font-weight: bold">30.5 MOA @ 1000</span>

44.0 Grains of RL 17 .69 @ 100, (not shot @ 200 yet) <span style="font-style: italic">2920 FPS</span> ES=25 SD=9 <span style="font-weight: bold">24.5 MOA @ 1000 </span>

I have more Load Dev to do with the RL 17, it was late in the day when I tried a couple, but it was obvious it was not going to be As Accurate as the others, or at least not as forgiving.

Question is... For Tactical type matches, would you chase the Great Velocity of the RL 17 and give up a little Accuracy, or chase the Accuracy giving up the flat Trajectory and wind bucking. ? And Why ? Thanks in advance. ~Ace~

 

[kraigWY]

Re: Velocity VS Accuracy Question

I'd go with accuracy myself. Maybe velocity will shoot a bit flater but that's why they have those lillt knobs on my rear sight or scope.

 

[Simon Templar]

Re: Velocity VS Accuracy Question

If you know exactly what range and wind you are shooting at then go with accuracy, but if you cannot use LRF:s and you have to estimate or range with your scope then I would definitely(and I do) go with more speed over benchrest accuracy.

 

[desertHK]

Re: Velocity VS Accuracy Question

I'll take accuracy over speed anyday. It would be nice to have enough ooomph to get out there in a relatively flat trajectory, but consistency is the key. Are you saying that it's better to have a 175 smk traveling at 2800 fps, but has a 2MOA accuracy vs. at 2600 fps but has sub MOA accuracy?

If you are concerned about the shorter or smaller danger space of the more parabolic trajectory then I would focus on range determination as part of my training.

 

[BryanLitz]

Re: Velocity VS Accuracy Question

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">All Data was Averages of Multi Groups</div></div>

This is important. How many groups? How many shots in the groups?

There is a significant difference in your average velocity, but depending on the number of shots in your groups, there may not be a statistically significant difference in your groups sizes or ES/SD.

If the groups and ES/SD data is compiled of 5 groups of 10 shot each or more, then it's probably solid. But if it's 2 or 3 3 or 5 shot groups, it may not be indicating a 'real' difference. I suspect your sample size is probably somewhere in-between.

Point is, you have to have 'hair-splitting' data if you're trying to make 'hair-splitting' decisions.

-Bryan

 

[AKAce]

Re: Velocity VS Accuracy Question

Most were 15 rounds, Three 5 shot groups.

I had numbers closer in velocity between the powders, but they were not the most Accurate. (LOW end of 4831 shot best, high side of 4350)

I realize that part of the data is not concrete, my only real question is for UKD, Tactical matches, is the decrease in accuracy (Still Sub MOA)acceptable to get the close to 200 FPS and 6 MOA less Elevation @ 1000.

I am not done collecting Data, and have more work to do with the R-17 looking for better accuracy, but having just swapped to the 6.5 for it's benefits over .308, I can't help bu think the Velocity is what will truly give it an advantage.

 

[BryanLitz]

Re: Velocity VS Accuracy Question

Ace,

3-5 shot groups is a pretty good sample. But given the minor difference in the ES/SD and group data, I'd say the major difference in your loads is still the average velocity.

Thinking outside the box...

If you're objective is to optimize a load for UKD contests, you might consider lighter bullet/higher velocity loads, like the 107/123/130 grain sierra, scenar, or Berger. You won't have the resistance to wind defleciton that you enjoy with the heavier 142 class bullet, but you will enjoy a longer danger space and absorb more range uncertainty with the flatter shooting round.

-Bryan

 

[MontanaMarine]

Re: Velocity VS Accuracy Question

I'd compare the mechanical accuracy, against 1K drift values, and see from those numbers which makes more sense.

In other words, given all loads are solid sub-moa, I'd give up .3 moa at 100 yards, if it will save .5+ moa of drift downrange, and extend supersonic range.

 

[AKAce]

Re: Velocity VS Accuracy Question

Thanks for the advice so far, I was contacted by a few very helpful folks with .260's and will be trying a dif bullet next weekend, they seem confident it will like the High end of the charges VS the SMK liking the low end. I will Update my results.

 

[dar1246]

Re: Velocity VS Accuracy Question

I would think on the IMR and RL-17 charge is about right but on the H4831sc that seems low on the powder charge. I have 5 260s and gave 2 away to a family. All the 260s have shot a hotter load with more speed with H48321sc.

260s are not finky to load for as long as you seated the bullets at the right seating depth.You should be around 2800 to 2880 from a 26" barrel with great accuracy.

 

[AKAce]

Re: Velocity VS Accuracy Question

With the 142 SMK's, Every combination shot best at the Bottom end of the powder charges. I have 139 Lapua's on the way to see if they act different as has been suggested to me.

 

[dar1246]

Re: Velocity VS Accuracy Question

The shot the 142s for awhile. I had better luck with the 139s and 123s. I would think the 130 bergers would also be a great choice.