Long range load development at 100 yards.

[spclark]

That be LC 'match' brass? I've been using Lapua Palma brass w/8208XBR & the Fullbore bullets for the season just passed. Excellent, wide node a bit farther up the ladder than where you're at in two different barrels.

 

[jweb308]

Erik and SP,

Thanks for the input.

SP,

Brass is LC Long Range from M118LR. I have used LC Match in the past and had very good results. Still have some in reserve.

Stay safe,
WEB

 

[savageshooter86]

Advice from this? Shoot ok at 100. Ladder test showed 43.1 to be center of node at 300 yards

 

[Erik Cortina]

Advice from this? Shoot ok at 100. Ladder test showed 43.1 to be center of node at 300 yards

What kind of chronograph? 43.4 seems unusually high compared to the loads on each side of it.

 

[savageshooter86]

Oehler 35P w/ 4' rail

I thought that was odd too

43.1-- 2675,2669,2677,2663
43.4-- 2713,2673,2685,2674
43.7-- 2717,2702,2717
44.0-- 2735,2744,2743

 

[Erik Cortina]

Oehler 35P w/ 4' rail

I thought that was odd too

43.1-- 2675,2669,2677,2663
43.4-- 2713,2673,2685,2674
43.7-- 2717,2702,2717
44.0-- 2735,2744,2743

I would run test again with 5 shot groups. Are you sure you didn't mix a 43.7 load with the 43.4?

 

[savageshooter86]

Don't think so.

I don't have chrony available Tom. I thought about shooting 5 shot groups at 500 yards Tom to see groups and vertical


Here is repost of initial powder charge test from the other week(42.5-44.6)

 

[stork]

I used to do the seating depth at 300 yards, but now I do it all at 100 yards since I have found that if it shoots well at 100, it will shoot at 300.

Virgil King (of the Houston Warehouse notoriety) found the same thing back in the 70's & 80's.

Excellent reading for anyone who hasn't had the pleasure.

http://precisionrifle.files.wordpress.com/2013/10/secrets-of-the-houston-warehouse-by-dave-scott-precision-shooting-magazine-special-edition-1-1993.pdf

Stork

 

[AlanPF]

I have a question, and sincerely hope that hasn't already been answered on the 88 pages of this topic.

If you use this method at 100 yards to tune loads for 1000, surely you would need to also test at 1000 to confirm? Because there are some sources of long range inaccuracy that will not be detectable at 100 yards. One is bullet uniformity, or more particularly BC consistency. BCs can vary by several %. Bryan Litz quoted a figure of 8% improvement in BC with a Whidden pointing die. Let's say two projectiles vary by 4% in BC, with one having a G7 BC of 0.300 and the other 0.312, and identical muzzle velocities of 3000 fps. I calculate the difference in bullet drop at 100 yards to be 0.003" which is undetectable, but at 1000 yards the difference is nearly 6 inches, enough to put you out of the 10 ring.

 

[Erik Cortina]

I have a question, and sincerely hope that hasn't already been answered on the 88 pages of this topic.

If you use this method at 100 yards to tune loads for 1000, surely you would need to also test at 1000 to confirm? Because there are some sources of long range inaccuracy that will not be detectable at 100 yards. One is bullet uniformity, or more particularly BC consistency. BCs can vary by several %. Bryan Litz quoted a figure of 8% improvement in BC with a Whidden pointing die. Let's say two projectiles vary by 4% in BC, with one having a G7 BC of 0.300 and the other 0.312, and identical muzzle velocities of 3000 fps. I calculate the difference in bullet drop at 100 yards to be 0.003" which is undetectable, but at 1000 yards the difference is nearly 6 inches, enough to put you out of the 10 ring.

Bullet BC uniforming is something that needs to be handled separately. You can not tune a gun to compensate for bad bullets. Get your gun properly tuned at 100 yards and get your bullets sorted to minimize BC differences and it will shoot at 1,000 yards.

 

[spclark]

You can not tune a gun to compensate for bad bullets. Get your gun properly tuned at 100 yards and get your bullets sorted to minimize BC differences and it will shoot at 1,000 yards.

Good answer that. Sorting then maybe tweaking bullets pays off only after you've worked out the other parameters that affect accuracy AND consistency out where you can see the results on paper.

 

[jlow]

Did an OCW with my 24” AI AT 308 today and here are the results: Berger 185 Juggernaut, Varget, Lapua brass, Tula LRP. Bullets seated to 0.010” jump. Conditions: 46 degree, 80 humidity, pressure at 29.23. Powder range 44.0 to 44.8 grains at 0.2 grain interval – no pressure signs. QL predicted OCW at 44.5 grains.

Top right 3 rounds fouler done with cheap Win brass/175 SMK/42 grain Varget so ignore.

Plotted average POI using OT data with red dots and arrows showing movement. Looks like average POI for the 5 groups did not change much within powder range tested. Probably the most movement outside group was the first charge i.e. 44.0 grains.

MV captured with Ohler 36p. Average MV linear within powder range. All groups had single digit SDEV.
First question is what’s next? Since the average POI did not move much and group size was small, should I still try to optimize with seating depth adjustment?

 

[jsthntn247]

I have a question about load testing at 100 yards when trying to keep everything in mag length. When seated to 2.800 I am jumping the bullet .140 in my 308. I can tell I'm in a node but the seating depth is not best. Would you still back off 2.800 in .003 increments or use something like .010 increments since you are sooooo far off the lands to start??

 

[jlow]

When I have done this in the past in your specific situation, I still adjust seating depths by 0.003” or 0.005” at most, but never as much as 0.010”. I think that is too much and you will miss the optimal seating depth.

 

[Brians356]

I have a question about load testing at 100 yards when trying to keep everything in mag length. When seated to 2.800 I am jumping the bullet .140 in my 308. I can tell I'm in a node but the seating depth is not best. Would you still back off 2.800 in .003 increments or use something like .010 increments since you are sooooo far off the lands to start??

Keep in mind the seating depth change affects not just bullet jump, but also net case capacity. So don't abandon small increments just because the bullet jump is so large to start with.

 

[Erik Cortina]

I have a question about load testing at 100 yards when trying to keep everything in mag length. When seated to 2.800 I am jumping the bullet .140 in my 308. I can tell I'm in a node but the seating depth is not best. Would you still back off 2.800 in .003 increments or use something like .010 increments since you are sooooo far off the lands to start??

Do .003" at a time. You will find a node.

 

[jlow]

Did an OCW with my 24” AI AT 308 today and here are the results: Berger 185 Juggernaut, Varget, Lapua brass, Tula LRP. Bullets seated to 0.010” jump. Conditions: 46 degree, 80 humidity, pressure at 29.23. Powder range 44.0 to 44.8 grains at 0.2 grain interval – no pressure signs. QL predicted OCW at 44.5 grains.

Top right 3 rounds fouler done with cheap Win brass/175 SMK/42 grain Varget so ignore.

Plotted average POI using OT data with red dots and arrows showing movement. Looks like average POI for the 5 groups did not change much within powder range tested. Probably the most movement outside group was the first charge i.e. 44.0 grains.

MV captured with Ohler 36p. Average MV linear within powder range. All groups had single digit SDEV.
First question is what’s next? Since the average POI did not move much and group size was small, should I still try to optimize with seating depth adjustment?

Wow! 61 views and not one feedback.. Must be really bad or really good! ;D

 

[Brians356]

Did an OCW with my 24” AI AT 308 today

Wow! 61 views and not one feedback.. Must be really bad or really good! ;D

I think we're all waiting for Erik to comment - I know I am. It's his thread, and his methodology.

(Not sure why you refer to "OCW" however, that's a quite different methodology than what's happening here.)

 

[Erik Cortina]

Did an OCW with my 24” AI AT 308 today

Wow! 61 views and not one feedback.. Must be really bad or really good! ;D

I think we're all waiting for Erik to comment - I know I am. It's his thread, and his methodology.

(Not sure why you refer to "OCW" however, that's a quite different methodology than what's happening here.)

Actually, that's part if the reason I did not comment on it, I thought he was doing something different and simply posting results for comparison.

I'll take a look and give you my feedback.

 

[Erik Cortina]

Did an OCW with my 24” AI AT 308 today and here are the results: Berger 185 Juggernaut, Varget, Lapua brass, Tula LRP. Bullets seated to 0.010” jump. Conditions: 46 degree, 80 humidity, pressure at 29.23. Powder range 44.0 to 44.8 grains at 0.2 grain interval – no pressure signs. QL predicted OCW at 44.5 grains.

Top right 3 rounds fouler done with cheap Win brass/175 SMK/42 grain Varget so ignore.

Plotted average POI using OT data with red dots and arrows showing movement. Looks like average POI for the 5 groups did not change much within powder range tested. Probably the most movement outside group was the first charge i.e. 44.0 grains.

MV captured with Ohler 36p. Average MV linear within powder range. All groups had single digit SDEV.
First question is what’s next? Since the average POI did not move much and group size was small, should I still try to optimize with seating depth adjustment?

I would go with 44.2