200yrd Ladder Test 6BRX

[clark98ut]

I'm new to the whole ladder test method and wanted to see if you guys could tell me more about what I'm looking at, and where I should focus my efforts.

This is out of a 24" Brux barrel.

This target is with the same components except using Ramshot Hunter instead of Varget.

Thoughts? Suggestions?

 

[Bradley Walker]

Was it windy? It looks like a lot of horizontal movement.

 

[TonyR]

I think you should try the ladder again with three rounds at each powder charge. Ideally, you will see a point where the vertical dispersion between the three at each charge will decline at the same time the higher charges start to impact lower, on average, than the lower charges. This is the area of the node you are looking for. Looking at what you did shoot on the upper target, see how 32.4 gr is above 32.6 is above 32.8? I'd shoot some three or five shot strings at those loads along with maybe a string at 32.0 and 32.8 if you aren't seeing pressure signs. See if the average vertical compared to your point of aim does the same thing with longer strings this time. Don't change anything but the powder charge when shooting a ladder. Same bullet, bearing surface, primer, and seating depth for all of them. Test those factors seperately and later in the process. It would also be worth reading Jason Baney's article about ladder testing. His method absolutely works. http://www.6mmbr.com/laddertest.html

 

[clark98ut]

Was it windy? It looks like a lot of horizontal movement.

I had a decent headwind, but didn't think that would affect things that much. My velocities also seem a lot lower than expected.

Thanks guys.

 

[TonyR]

Head winds and tail winds can give you vertical depending on the design of the range facility. If the targets are close to the impact berm, the wind can come over the top and give you vertical that might not be there in a wind from another angle. Many chronographs show wildly different velocities if the lighting changes. I actually saw nearly 100 fps with a Shooting Chrony when some safety baffles cast a shadow over the screens one afternoon.

 

[CdnHotshot]

Question: Can anyone tell me if a 300 yard ladder test is more accrute then a 200 yard test?

Thanks
AL

 

[TonyR]

I have heard both sides of this debate. I do most of my ladder testing and other load development at 300 yards. I can only say that I have been able to develop loads that test well at 300 and shoot to my satisfaction to 1000 yards. I like 300 because I can still see bullet holes from my 7mm through the rifle scope but also see the effects on the target of ammunition variables that are important at the longer ranges. Some of these effects are harder to see at 200 than 300 so I prefer to test at longer range whenever possible.

 

[Erik Cortina]

Tha farther the better when it comes to ladder tests. I always try to do them at the distance at which I will be shooting.

Good luck.

-Erik

 

[limbic]

What about the wind factor? Isn't there a distance that the wind begins to mess with the results. I do most of mine a 200 or sometimes 300 if wind is negligible.

Out of my BRX (27" Broughton) I was getting 3100fps max fps. Accuracy was really good (.072 three shot groupat 100y) but it was way to hot at 33.9 grains of Varget. I was also seating the bullet (105Lapua) when I closed the bolt. Fired brass was .270 and I sized the brass with 269 bushing. I need to run this test again and see if the numbers hold up. Oh and find a load that dosen't make the bolt so sticky ;D

 

[tsiero]

Here are several comments. Extending the ladder test from 200 to 300 yards will amplify the errors or deviations. One hole groups at 200 yards will probably open up at 300 yards. Both horizontal and vertical dispersions will increase so that you can better see what going on. Here are two pictures of a 200 yard ladder test with seating depth as a variable in .003" increments. I draw a picture of the target at the bench to track my shots so you can't really see anything other than a preponderance of horizontal dispersion. The first picture are Sierra 107's and the second are 108 Bergers over 32.0gr of Varget and Fed 205M primers. Wind was only a minor factor. I would estimate only 1/2" of the dispersion. As it turned out they both like to be shot at 0.010" off the lands. Now I will do the powder test in .2 gr increments but pick a windless day and shoot at 300 meters. If it is a real good day a 500 yards. Then I will really see what I have for the combination. The upper shot in the top picture was the first in the string and the lowest was the last. What luck! P.S. It is a Dasher case.