Topic: Ladder Test for load development

[luvmy45]

Well it's winter, so it's time to load up my LRTR ammo for the year, since I have acquired a suppressor, I thought it might be a good time to do a little tweaking just to make sure I've got the right load.

Saw a thread over on SH and then RG said he posted a similar account over in the download section.... He's right and it's worth the read.

The long and short is, you do a ladder test to find the harmonic/recoil sweet spot, dial in that specific load and your good to go.

In retrospect, as I was driving to the range, and the snow kept getting bigger today, I probably should have turned around, but hey, I was already committed.

Other than the snow, and limited visibility, it was a nice day  Windless for the most part and I did have the range to myself.

The ladder test is best done at distance, they recommend 300yards, so I settled for 300meters. You load 1 round each from the Max down, in .2 or .3 grains until you have 20 or so rounds. I want the velocity so I only loaded 10 rounds down and I exceded the max printed load. But I was stepping up in .2 steps and watching for pressure signs... none appeared and I think I am going to keep going up a bit.

So, you are suppose to mark each round you shoot, so that you know what's going on... and you are suppose to aim at the same point everytime, and let the bullets just do their thing. Well, with the snow coming down hard, and the target barely visable at 300m... I just shot a 10 shot group and figured I'd sort it out later.

I'll be danged if the group was just 2.25" high, 10 shots and not even a MOA of vertical deviation. There was a 1.5 MOA horizontal deviation, which I attribute to wind moving things around.

So my gun will shoot a sub MOA group at 300m, in the snow, with load variation of 1.8 grains... with a suppressor.. so now I'm scratching my head. It would appear this rifle just like's 175gr SMK and RE15 and pretty much will eat it all.

My next step is to go back when I can see the target with my spotting scope or want to make the trips down range, and do it again, only starting a little hotter and working my way up a little higher. I didn't drag the chrono out, but my final shots should have been around 2600 to 2625, like to get them up a little higher for more consistent 1000 yard shots.

It's an intersting test to do, I'm still kinda baffled by the vertical group, as my fps should be from 2500 to 2625, and shown up more than that on paper. Maybe I'll back off to 400m when I try this again, to try and get a more developed vertical string.

Good stuff. Oh, it's a 308 that I was shooting.

[J Mack]

Another source for info on ladder testing.
'Optimal Charge Weight' method by Dan Newberry: http://optimalchargeweight.embarqspace.com/

Also I noticed 45gr of RL-15 gave me 2660FPS in the spring on a 75 degree day and the same load gave me 2596FPS on a 38 degree winter day from an 18" barrel shooting 175 SMK's and I was not expecting that much of a drop with RL-15.

[ida83704]

go with whatever shoots the most consistant.

the diff between 2600 and 2700fps with a 175SMK is ~50 yards of supersonic distance and not more than 1MOA of elevation


So RL15 has a 2fps per degree change in temp, that seems like alot.
I've heard Varget kicks RL15 on temp, but that never seen it that plain

[luvmy45]

41.5 has been the winner for the last year and half... right around 2600 in the summer and I've taken that to 1300yards.

We'll see when I get done with the ladder test, I may just be right back to where I started, in which case, I'll know that that's that.

Gotta love getting dope in the winter and comparing it to the summer.

[RGinIdaho]

My Varget load shot 2695fps @ 95deg and 2690fps @ 28deg.

[Nomad]

 You may want to try a couple of different powders, Imr 4064 40-42.5 gr, Viht N150 42-45 gr,
did some loads with Imr 8208 last fall with 155gr bullets showed promise and RL-17 with a couple
of 180gr bullets and the jury is out on that still working on it......
 RGin shoots the same load as I do. Different rifles different loads.
 Ladder test does work once you get your group work with different primers to tighten them up or
will waste of time...
 

[luvmy45]

When I run out of RE15 I might give Varget a try... but I've still got 6lbs so it may be a while. 

I have gotten my primer/powder/brass/bullet combo to do almost 1/4 MOA groups at 100m, So I think that I have got the best load for the rifle right now, doing the ladder test to verify that. I think I ran into the node on the barrell harmonics on accident, and now that I know a little more, seeing if a suppressor changes that node and if I can tighten it up at all.

RG has a sweet load, and his SD's are really low, I think with some more bench prep I can get my SD's down as well, but one monster at a time.

Winter, what a great time to spend at the bench.

[TrooperBrian]

I tried this with TAC a few days ago, the results are a bit hit and miss. But neglecting the wind difference, I have a few groups within 1" of each other at 300. So I went ahead and loaded up 10 of each of the three loads that were in that group and I'll try again with a cleaner bore. I forgot my cleaning rod in Norho so I have been shooting with a pretty nasty bore.

[luvmy45]

Might want to read the document again.

Once you find your grouping, depending on what your step size was, you start over, with a small step size at the max load that's in that group.

So if you grouping is for ex. : 41.0, 41.3, 41.5, you would start at 41.5 and us say .2 gr increments working your way down. for 5 loads or so, and shoot the ladder test again and see how your groups are.

Then take the small group, and load to the charge wieght in the middle of the group. What this does, is say your loading along, and you throw a light charge by a grain, or you throw a heavy charge by a grain, it's not a flyer in the group, because your gun is still in it's "tuned" spot for that load.

My guess, is that is why we have flyer's, the gun is performing on the edge of it's tuned area, and you get a round that exceeds that tuned area and whammo, flyer (giving that all else is performing well from the shooter)

My guess is if you load 10 shots each from the "tuned" area for 3 loads, you would get 30 holes in a MOA spread... which would be chasing your tail, you looking for the load that pushes it out of it's "tuned" so that you can find that middle load.

Just my 2 cents...