Ladder test works!

257speed · #1 07-11-2005, 04:38 PM

Many thanks to Abinok and the others for turning me on to the ladder test. Had to develope a load for my 257 STW using Ramshot Magnum and 110gn Accubond. Ladder tested 20 rounds at 400yds. Sure enough, two distinct sweet spots at low (3300fps) and high (3500 fps). Chose the middle load of the higher sweet spot and sure enough, shot a 1/2 moa group at 100 yds (first four in .290")at 3490fps. Load developement in less than 40 rnds! [img]/ubbthreads/images/graemlins/grin.gif[/img] Gotta love it, especially with a barrel burner like the 257 STW.

4ked Horn · #2 07-11-2005, 05:00 PM

Cool beans.

I'm looking forward to trying it myself in the future.

So I take it that you shot a 1/2 MOA <u>5 shot group</u>? Good deal. The les shots for load development the more shots for critters.

257speed · #3 07-11-2005, 08:52 PM

Yes thats correct, five shots in .590".

Kenster-Boy · #4 07-11-2005, 09:01 PM

I am curious if you could BRIEFLY explain what a ladder test is? I think that I am already doing this sort of thing without knowing that it was a common procedure but just to be sure, what is it?

Thanks.

abinok · #5 07-11-2005, 09:27 PM

Glad to hear it worked for you 257. Next time you see somebody at the range knee deep in brass, with a frustrated look on his face, be sure to share!

7mm, the short description would be shooting a series of rounds, each with different powder charges loaded in increasing incriments of charge wt in an attempt to find vibration nodes that minimize the dispersion caused by varying charge weights, while allowing an accurate, repeatable load to be found for a rifle, with a minimum round count being fired. Ive got a document that does a passable job of explaining the ladder test. If you would like a copy, id be happy to email it to you.

257speed · #6 07-11-2005, 09:33 PM

7mmagman, check this out http://longrangehunting.com/ubbthrea...p;page=8#67743

257speed · #7 07-11-2005, 09:40 PM

Abinok, I edited my post above with a picture of the results of the test, but I did not have any pictures of the ladder target. I wish I did because it was different than yours. Even at 400yds, the shots did not climb vertically very much. What they did do, is that they would be very erratic and then they would cluster, than get erratic again and cluster again. Out of the 20 shots, there were two distinct clusters at two different velocities. I chose the faster of the two clusters and then picked a load somewhere in the middle, which gave me the group in my previous post. All in about 27 total shots! I think at these distances, the 257 STW is shooting so fast/flat that there was not much vertical change.