First time trying something like the ladder test

[Dave in WI]

I always used to just shoot at 100yds for groups when doing load development. Wanted to try something like OCW for once. I put together a rifle in 700 action chambered in 7-08AI with Bartlein 3B 8.7 twist. Finished at 20" (I know, that's what owner wanted).
Hornady brass with WLR primers.
Berger 150 Classic Hunter at @2.737" COL just into lands.
VVN550 powder. Shot at 300yds. Slight wind from right.
Note: this is with once fired brass from same chamber that did not fully fireform. After this second firing, headspace comparator showed mostly equal measurements instead of many short from first firing.

1 42.0 2520
2 42.5 2614
3 43.0 2635
4 43.5 2661
5 44.0 2650
6 44.5 2645
7 45.0 2743 bolt started sticking a little (not on lift, on extracting)
8 45.5 2795
9 46.0 2824

Do I load up 3 of each from maybe 4,5,6 and shoot for groups, or am I wasting time until all cases are fired the second time?

****Edited to add: Optical Chrono placed 10' in front of muzzle

 

[User4302021]

I always used to just shoot at 100yds for groups when doing load development. Wanted to try something like OCW for once. I put together a rifle in 700 action chambered in 7-08AI with Bartlein 3B 8.7 twist. Finished at 20" (I know, that's what owner wanted).
Hornady brass with WLR primers.
Berger 150 Classic Hunter at @2.737" COL just into lands.
VVN550 powder. Shot at 300yds. Slight wind from right.
Note: this is with once fired brass from same chamber that did not fully fireform. After this second firing, headspace comparator showed mostly equal measurements instead of many short from first firing.

1 42.0 2520
2 42.5 2614
3 43.0 2635
4 43.5 2661
5 44.0 2650
6 44.5 2645
7 45.0 2743 bolt started sticking a little (not on lift, on extracting)
8 45.5 2795
9 46.0 2824

Do I load up 3 of each from maybe 4,5,6 and shoot for groups, or am I wasting time until all cases are fired the second time?

This is not an OCW test, this is an Audette style ladder test.

You don't say what chrono was used, but if it was a magnetospeed then the results are invalid anyway. Nothing should touch the barrel for either OCW or ladders.

If you used labradar or an optical chrono and these POI's are valid, then I would load #5 and start seating tests.

 

[Dave in WI]

This is not an OCW test, this is an Audette style ladder test.

You don't say what chrono was used, but if it was a magnetospeed then the results are invalid anyway. Nothing should touch the barrel for either OCW or ladders.

If you used labradar or an optical chrono and these POI's are valid, then I would load #5 and start seating tests.

Thanks, Dog. Edited title and added optical chrono used.

 

[fmuguira]

I would agree with Dog Rocket ... #5, 44 grains and various seating depths. I personally would start right near the lands if that works in Mag and then shorten up. 44 grs 'appears' to be in a node velocity wise.

 

[RegionRat]

Dog is correct, this is much more like an Audette Ladder than an OCW. It does show that from the jump between load 1 and 2, the rest would not have much elevation change. The real question is if any single shot uncertainty is really small enough to trust the shotfall pattern. The good news is your total elevation change between 2 to 6 seems to be tight, if it will repeat.

You can either go to load 5 and test for seating depth, or do another run from 2 to 9 and see if this was all just scatter.

Were there any other signs of high pressure noted on the cases for loads 7 and up? If there were, then load 5 seems prudent.

 

[Dave in WI]

Were there any other signs of high pressure noted on the cases for loads 7 and up? If there were, then load 5 seems prudent.

I did not see any additional flattening of primers or ejector swipe up through load #9

 

[fmuguira]

Could try #5 and if accuracy there could go up for next node; typically 3% more. Put you around 45.3 ish grs ...

Sounds like you experienced no pressure up there already ...

 

[RegionRat]

Well, if the note about the difficult extraction on load 7 was a fluke and load 8, 9, didn't stick, combined with no visible signs of pressure on the primer or case, it makes me wonder if you shouldn't try one to two more runs of the same test from load 2 though 9 to see if the results are repeatable before you stop and do detailed group tests at any one load for seating depth.

For my own rigs, I run ladders more than once, and I round robin the shots to make sure bbl heating or fouling isn't adding bias.
I then plot all the verticals against charge weight on one plot, and again with velocity against charge weight on another. We look for nodes that help us decide where a OCW is likely to give us the most forgiveness for vertical and speed. The hope is groups at that charge weight can then be optimized by playing seating depth.

If the client is keeping his shots within say 500 yards for terminal ballistics performance, it looks like you should have enough muzzle velocity for a good all around rifle.

I run that ladder twice each time, and again, on two separate days, I do this to see how repeatable the results are between those four runs before I select a charge range for group testing. By the time I am done, I have a fair idea of how the cold bore performance will look and the brass is all detailed. The next tests I run are for big swings in climate. So far, using powders like H4350 that are known to be less temperature sensitive, I have been very happy with the efforts. YMMV

 

[fmuguira]

As RegionRat mentions load #7 somewhat puzzling... maybe just a fluke, odd case?

Anyway looked at VV550 burn rate and appears slightly slower than H4350.... with that in mind I've worked up to 47.2 gr H4350 load in my standard 7-08 with a 162 AMax. Gives 2710 fps Ave in 24" factory Rem 700 SS SPS barrel and consistent sub-MOA.

Maybe RegionRat is on to something and you should re-test and maybe go up again if no pressure signs. I d think in that 7-08 AI, even with 20" tube, 2800 fps should be attainable. Just need to see if accuracy can be found there.

Good Luck

 

[Slick8]

I don't have any experience with this powder but have shot a few ladders.

I would load a 3 shot group of number 5 not changing anything.

I'd retest 7, 8 and 9 perhaps even adding a 10. I say this reluctantly as I don't know what the book or QL says about this round's max load but it seems you have a good knowledge base and feel for your rifle. Load carefully.

 

[pony doctor]

I always used to just shoot at 100yds for groups when doing load development. Wanted to try something like OCW for once. I put together a rifle in 700 action chambered in 7-08AI with Bartlein 3B 8.7 twist. Finished at 20" (I know, that's what owner wanted).
Hornady brass with WLR primers.
Berger 150 Classic Hunter at @2.737" COL just into lands.
VVN550 powder. Shot at 300yds. Slight wind from right.
Note: this is with once fired brass from same chamber that did not fully fireform. After this second firing, headspace comparator showed mostly equal measurements instead of many short from first firing.

1 42.0 2520
2 42.5 2614
3 43.0 2635
4 43.5 2661
5 44.0 2650
6 44.5 2645
7 45.0 2743 bolt started sticking a little (not on lift, on extracting)
8 45.5 2795
9 46.0 2824

Do I load up 3 of each from maybe 4,5,6 and shoot for groups, or am I wasting time until all cases are fired the second time?

****Edited to add: Optical Chrono placed 10' in front of muzzle

 

[pony doctor]

For me, once I see a group forming, I like to move to 300 yards and as suggested, begin tuning your seating depth with a well designed ladder test. Early on, I was looking for velocity to start my load development but learned that velocity does not create 1/2 moa patterns or kill anything! Accuracy is the only goal from this point forward.

 

[jasonco]

Load #5 and shoot 3 shot groups at different seating depth, then go from there.

 

[BountyHunter]

IMO .5 grain jump is a little too large for a 7-08 case from my experience. That size case I use .3 increments and .5 on larger magnum cases.

I would shoot from 43.4 to 44.2 with .2 increments and three shot groups. Watch your chrono and groups. Pick the best and most uniform in SD/ES with group and then do seating depth test starting at Max magazine COAL minus .010. I never liked crowding a magazine.

The 150 might be good for elk and larger game, but in that caliber the 120 ballistic tip is a proven winner time after time and shoots flatter. You should be able to easily hit 3000 fps with it in the AI. I am 2990 fps in my regular 7-08.