Ladder test confusion

[Jmccracken1214]

Trying to get this H4895 to shoot in my 308. Had no luck with Hornady 168s and trying smk175 now.

had a few rounds that were very close but the 3rd rounds velocity would be off.

what’s up with 43gr losing velocity when it’s the highest charge?

 

[ShtrRdy]

I've seen this happen before. I dont know what causes it. I would suggest continuing stepping up another grain or two.

 

[nn8734]

Seeing an occasional drop in velocity with an incremental increase in charge weight is common and nothing to be concerned about. Sometimes, I notice a very slight drop just beyond one of my accuracy nodes on the charge weight curve when doing a ladder.

Did you write the charge on each case? If so, measure the diameter of base of the case corresponding to the 43 grain charge with dial calipers or a micrometer then compare the value to the diameter of an unfired round. If that fired case’s diameter is <.0015 greater then id go up a little in charge weights until you see expansion of .0015 or greater. For me, .0015 is my pressure threshold and I stop there once I see that much expansion.

Also, 4895 is somewhat on the quick side burn rate-wise; if you reach pressure too fast or before hitting your high node (most rifles have two nodes), I might try Varget. Never met a .308 that I couldn't get to shoot using Varget.

 

[Deleted member 10043]

Ladder tests are confusing because their is no basis to it.

 

[Powder_Burns]

How many rounds per charge weight? Lets say your 43.0 has an ES of 30fps...it could be 2618 or 2648fps.

When I do ladder tests, I’ll do 3-5 rounds per charge weight. I’ll do like .3gr intervals until I find pressure signs, then work down from there to find a node that groups well and has low es/sd. Then I’ll check .1gr and .2gr up or down, and then mess with seating depth. (Then buy a new barrel and start over cuz its shot out now.)

 

[Rocketmandb]

I would play with 42.2 - 43.0 again, and also go a couple ticks more, pressure allowing. That 42.6 - 43.0 range looks like a flat spot, but validate it. Not unusual to drop in velocity on an up-round. As @Powder_Burns says, you could have gotten a low one on the spectrum of 43.0 loads. Your velocity there is very much within the realm of reason.

By the way, this is why I always load two ladders worth. Either I have a round that doesn't read on the LabRadar, or one that's just out of whack that I want to validate. But most importantly I like to validate in one trip.

 

[EN2722]

I’ve also seen a velocity drop right after a node or within .2 to .4 of the start of a node.

If you’re an excel or google sheets whiz, I recommend plotting them in a line chart so you can see where the flat spots are. Those historically tend to be the node in which in theory will produce the best ES/SD’s for your rifle.

From there I load 5 or 10 across the node in .1 internals to validate it.

Also, I’ve had great success with IMR4064 with both 168’s and 175/178’s in my 308 with a 26” Criterion

 

[Steel+Killer]

When I am trying to find a load for a new bullet/rifle combo I load fifty rounds total, ten five round groups, five per charge weight that I am testing. I usually make my last two five round groups .2-.4 over published max. I am shooting these over a magnetto speed checking the SD/ED and shooting for groups at the same time. As I am working toward the published max rounds I am checking for pressure signs. I have noticed I can usually go way over published max before any over pressure signs appear.

 

[smoothy8500]

I load fifty rounds total, ten five round groups, five per charge weight that I am testing.

That sounds "old fashioned"! We're all doing the OCW/Ladders/Nodes.

 

[Milo 2.5]

If me, I would test between 42.5-42.9 gr, but like an above poster mentioned, your sample size was too small.

 

[Rocketmandb]

If me, I would test between 42.5-42.9 gr, but like an above poster mentioned, your sample size was too small.

I don't view first ladders as the end-all, so have never considered sample size to be critical on them. For me, the first ladder is about finding areas to validate with a second set of tests using larger numbers of rounds. Then after that I'll run a bunch through to get the real numbers.

 

[Milo 2.5]

I don't view first ladders as the end-all, so have never considered sample size to be critical on them. For me, the first ladder is about finding areas to validate with a second set of tests using larger numbers of rounds. Then after that I'll run a bunch through to get the real numbers.

I am sure we all do crap differently, lol
Unless this is a brand new barrel, the numbers generated here should hold.

 

[db2000]

Anecdotal but I had good luck with 42.2 H4895 and not even of my better SD's
Savage Model 10 Ashbury Precision Ordinance .308 24" barrel, 1-10" twist, SilencerCo ASR brake
Magneto v3, Hornady digital scale, Lyman manual caliper

Sierra MK 175 HPBT
40F 45% 30.17mmHg
Fed brass x 6 firings
H4895 42.2 gr
Fed 210M
COL 2.020
COAL 2.780
2729, 2695, 2724, 2723, 2718
2700, 2720, 2707, 2718, 2685 SD 14.4
0.6" group
(pic is not this firing but similar results)