Odd Ladder results

[DP425]

Loaded up a spread of cartridges using Lapua brass, 175 SMK and Varget. 42gr up to 46gr in .5gr increments.

After firing 5 rounds of 168SMK Fed to ensure I wasn't rusty and get a good initial zero so I didn't land shots who know's where on the paper I was using. I went ahead and started at 42gr (hodgdon book min)... First landed almost POA- 42.5gr ended up landing about 6" higher. All the rest landed within about a 1.5" group near the first shot. Distance of 200m. I stopped at 45gr (book max) because, well... didn't really see any reason at all to shoot over max when dispersion was so minimal as is.

I've never used the ladder method before, so it's my first go at it... it seems this is some pretty abnormal results. I can still discern some info from it as some rounds landed nearly right on top of each other... but I was really expecting like better than a foot of dispersion, if not two. Anyone ever experience this before? Rifle is a 20" OBR. Almost like it's not really sensitive to the load- which is a bit baffling to me.

 

[DP425]

Re: Odd Ladder results

Sighters- bottom was first shot, ragged hole are the following 4
@200

And here's the "ladder test"- as you can see, there isn't much ladder to it. Last shots went through existing holes so I couldn't really mark where they went as I didn't know.
@200:

 

[turbo54]

Re: Odd Ladder results

Looks like you need to do it at a longer distance. Also, load two identical ladders next time so you can have more confidence in the results.

 

[Big Dog Steel]

Re: Odd Ladder results

If I were you I would do it over again. Use a smaller aiming point and use 300 yards as a minimum distance.

It seems very odd that #2 was so high then your shots drop as your charge increases. It doesn't seem right...every test I have ever done, the charges climb to a node then climb out of it. I typically use 5-10% or less charge variation between rungs. Half a grain seems fairly coarse for the test. I would take your maximum book load and count 10-12 steps from there. I would run .3 grains, shoot a few sighters just as you did to warm up the barrel and then procede with the test. Shoot one shot, then go down range and mark it, shoot another, mark it, etc.

 

[turbo54]

Re: Odd Ladder results

The ladders I've run don't seem to indicate that a higher charge weight = higher point of impact. At 600 yards, I've seen 1/2 grain more powder hit 6-7 inches lower than the last shot.

 

[kill_goose]

Re: Odd Ladder results

Back up. 400 yards or further.

My first tests with my .260 were at 400 and yielded no clear and definable node. Gonna go to 500-600 for the following finer tests.

+1 for doing two identical tests (I usually do one ascending, and the other descending with cooling time between each shot).

 

[DP425]

Re: Odd Ladder results

Okay should have mentioned- that aim point isn't like "center of black box"... it's corner of black box. In this case, bottom left corner.

Yeah I was a bit worried I'd hear "back up". All I have left is a 300m range 30 min drive from me. This was my local range and 200 is the max. And the thing that REALLY confused me was the ONE shot that went like 7" high.

Guess I might have to set-up to run this again and make the 30min drive so I can get to 300. Bastard charges like $8 per half hour too. When will my spottings scope show up?!?

 

[DP425]

Re: Odd Ladder results

And the .3gr spread sounds pretty good too- assuming this ladder becomes a ladder not a semi-decent group for a beginner (I'm not a beginner fyi)

 

[aquinas]

Re: Odd Ladder results

The point of a ladder test is to eliminate vertical dispersion. It usually does not show up at close range. 500 is the minumum I'd go. You proved it to yourself with the group. Now do the same at 600 and see what kind of results you get. In other words, a load that works at 200 will fall apart at distance. Most of the problems won't even show on the target.

1/2 grain is way too big. I do it in .01 grain icrements. You are looking for an area where 3 or 4 shots land withing a few inches of vertical of one another. I don't care about windage windage because when I'm doing a ladder test, I don't adjust for wind. When you find this area, test those loads. You are looking for a load that is not so sensitive to any changes. There's a good article on 6mm br about ladder tests by jason somebody. maybe someone can provide the link.

 

[ryhag1]

Re: Odd Ladder results

Great article for Ladder testing.

http://www.6mmbr.com/laddertest.html