Ladder testing a 6-284, phase 2

[rstreich]

I wasn't happy with my normal mode of load workup. It worked fine most of the time, but when it missed, I was left with nothing. So, after reading a few bits about ladder testing, I thought I'd give it a try.

I went out and shot a ladder series with my 6-284, RL-22, and 105 Scenars. From that I selected a powder charge and loaded up a series of 10 three-shot groups. I started with a .025" jam and worked my way out in .005" increments up to .020" off the lands.

The results kind'a surprised me. The groups pictured below were shot at 100 yards. I was expecting to see more of a progression in the groups--from bad to good and back to bad or somesuch. However, it seems rather random to me.

If the results are valid, it's kind'a obvious which seating depth to work with, but I was hoping that someone who has done this before could tell me if the apparent randomness is to be expected or, at least, not worried about.

 

[brad6ppc]

When I do my ladder tests I do it at the 200yrd mark.What you shoot at 200 will be pretty consistant the rest of the way out.I found that 100yds is not enough to show group dispersions accurately enough for long range shooting.But then if you are only going to shoot 100yds your done.

 

[billmo]

Robert, In all the ladder test I have done I have found the random shots also. You would think that your next higher powder charge would print higher on the paper but it does not work that way for me. It has been said that the "barrel whip" due to vibration changes has control over where the next bullet will print but I don't have any credentials to prove that. But, I have found that the groups that print the tightest will be a good place to start with your load development. On different days with temp. swings, air density and wind changes the load may need to be adjusted. Just my findings. Bill

 

[Fred Bohl]

Robert,

Just a few observations:

In my experience, three shot groups can be very deceiving, so I always shoot at least 5 shot groups.

For seating depth trials, I always clean,1 wet 2 dry patches) between groups.

I typically wait 1 minute between shots when jumping,-) and 2 minutes when jammed,+) and try to keep all cartridge in chamber times near 5 seconds.

Doing the above generally shows more of the pattern you were expecting. However for bullets that worked better jumped,107 SMK) the good point is on the jump side,-) and those that work best jammed,105 Berger VLD) the good point will be on the jam,+) side.

Also note that unless you are chasing your "touch",0.000) point, apparently good seating depths near that,+/- 0.005) won't be valid by the end of the test. The touch point erodes toward the barrel at 0.003 to 0.007 per hundred rounds roughly proportional to velocity.

When are we going to see further reporting on your results with that new March 10-60x variable? I've had to delay ordering one myself do to other more urgent expenditures.

 

[bootlaceb]

I agree with Brad6ppc. The further you shooting out,the better the variation shows.
I do it on 300yrds, and it shows up very well.

 

[rstreich]

Bill,

Phase I was shooting just ten shots at 300 meters with a ~1% increasing powder charge to look for shots that clustered together. You don't need any credentials to make the claim about barrel whip. Varmint Al has done enough modeling on this issue and backed it up with enough empirical evidence to make it real.

brad6ppc,

At 100 yards I might get false positives, but I won't get a false negative. A bad group at 100 isn't going to look any better at 200.

Fred,

I know what you mean about the three vs. five. I used to shoot five-shot groups, but it just took too long and cuts into my barrel life. I looked at it this way: As above, I may get false positives with a three-shot group, but a bad three-shot group would still be bad if I put two more shots in it. I also focus on the shooting better with three-shot groups. If the first three looked bad, I found that I was not as focused on the last two when shooting five-shot groups. False positives I can eliminate with a few additional groups, preferably at 300 meters.

The only time I do any cleaning is when I switch powder or jacket material. If I'm shooting groups, I will probably clean between series, but not always. My rationale is that if it won't shoot in a dirty barrel, it's not going to shoot in a match or in the field,doesn't really apply to a medium- to big-game rifle, however). The truth is that I really hate the tedium and occasional frustration of working up loads and I'm too lazy and/or busy trying to get everything done that needs to be done at the range.

As to the March, well, I don't really have anything to say other than I want several more. 60X is pretty slick. Once I've had it out for a full season in comp., I'll probably go with a fixed power. From the bench, I never use anything other than 60X even when the mirage is horrendous. However, I'm curious to see if I'll want that much power when shooting prone. I won't know that until I get my prone rifle. I think I will, want the 60X that is, but I'll wait and see. Curiously, the thing I like about it the most are the nicely designed turrets--easy to read with positive clicks all in a comparatively compact package.

 

[billmo]

Robert, that is interesting. I had not seen that before. Am I right in assuming that barrel whip is at least partially responsible for higher powder charges printing lower on the target while shooting a ladder test? Thanks, Bill

 

[rstreich]

Apparently. I noticed that when I was shooting ladders from my 6-284 and my 6BR, I'd get a couple of shots next to one another, then one a bit lower, then the next shot would be up and out of that cluster.

Dig around more on Varmint Al's site. He's got all kinds of stuff laying around in there.

 

[brad6ppc]

But if you shoot at 200 or 300 yards you will eliminate your false positives and you can concentrate on your good groups.I have had loads that were great at 100 but terrible down range.But if you have a good load at 200 or 300 it will be good all the way out.

 

[rstreich]

But at 200 and 300 yards then I have to start worrying about the false negatives. Did I get my shot off before that wind change? Was that shot out because of a condition I didn't see? Etc. It makes the two-and-one groups kind'a agonizing with the second guessing. In the end, I wind up shooting more groups that way.

Sometimes I have to go out further. For whatever reason, one of my .223s will shoot a four-grain spread of VV 133 and 52 gr. Bergers all into little holes. That one I have to take to 300 to sort them out. But then, it's usually a little dicey in the wind at 300 with the little bullet.

 

[jo191145]

rstreich
First off let me say every load I've ever developed started from an Audette ladder. I shoot more ladders than groups and can usually tell if I'm in the ball park with my chosen components.

As for your seating depth test. You mentioned it seemed random.
I respectfully disagree. Have you ever read the story "Secrets of the Houston Warehouse"
If not you should be able to google it on the web.
Whether this story is true or not I cannot say but the most interesting part for me was the description of seating depth.
Your groups seem to jive exactly with that description.

Your group seated at .000 shows vertical. +.010 shows horizontal.
+.005 is getting pretty good. You might want to try +.006 or .007 at greater distances.
Of course -.010 is looking good too.

Like you I spare the rod during load workup. I need my rifles to shoot hot and dirty so thats how I need to work loads.
Lighter fluid works good for swabbing out any developing crud if you leave a gun soiled for a few days.

 

[rstreich]

When you reach a plateau the bullets tend to go to the right somewhat and roll-off very slightly.After that the bullets will center up again and hit higher.

I had pretty crappy conditions when I was shooting the ladder portion of this, Lynn. I love our 300-meter range for matches 'cause it's a real PITA for matches, but it drives me kind'a nuts when I'm trying to develop loads. However, I saw exactly what you described from all three of the guns I was starting load workup for.

If your a good note taker and watch your conditions like a hawk you will get great accuracy from the load that went slightly right and rolled-off.
If your not a great note taker and use that same load at a match when it is hotter out your groups will show 2 shots low and right on the target followed up by 2-3 higher up and left.
I usually pick a load just shy of the load that hit right and low to avoid heat related problems.

Thanks for that tip. I went with the load right before the one that dropped to the right. Since I was shooting from an air-conditioned building, I figured I'd be moving up the curve when I was shooting from outside. Now I know that I can go up that extra half-grain if I want in cool conditions.

For your seating depth check I would get to the range whenever the best conditions appear.The 107's I've shot seem to like two points.One just back from the full jam length and one about 0.023 off the lands using 0.003 of neck tension.
Lynn

I never got a chance to try the Sierras. This is really just a glorified varmint rifle that, it turns out, will make LG weight. Sadly, I've apparently missed the last long-range match here this year, so I'll probably put it up for the Winter. I just thought I'd give it a try. My 284 prone gun,still under construction) will likely get most of my attention next year.

Thanks a lot for all of your advice, Lynn. You've helped turn this 6-284 project into much more than I was expecting.

BTW, I had run through the pound of RL-22 that I had and only had one pound of the RL-25. Given your comment about it being a "fast" lot of RL-25, I just ran the ladder again with a new lot of RL-22,I bought ten pounds this time) instead of continuing with a new lot of RL-25. The new lot of RL-22 was pretty close to identical with the original lot, but I didn't have some of the "odd" shots this time,likely operator error dispensing charges). I wound up with 52.5 grains as my load. I haven't forgotten what you said about the 50-53 grain range, but hoped that maybe the extra bit of barrel, different bullet would make a difference.

jo191145,

I was talking to Jim Borden about another project and I took the opportunity to describe my groups to him. When I said "...then I had one string horiontally." He replied, "Yeah, and another one vertically..." I figured I was on the right track. His response to the bad groups on either side of the "good" group was that, in his experience, pointier bullets are that much more finicky about seating depth. So, I'm feeling much more confident in my results these days. Now if only I had a match to try it out in....

Echoing Lynn's point from above, I now need to repeat some measurements to ensure that those loads were as far off the lands as I think they were.

 

[bsekf]

When you shoot ladder groups do you arrange it so you don't shoot the 1st group from a clean barrel and the last group from a dirty barrel? Hard to explain, 1st shot 1st group then 1st shot 2nd group then 1st shot 3rd group and on and on.

I understand 3 shot groups when working with OAL, but how about powder charge? The first article I read about increment loading used just 1 shot.

Bill

 

[billmo]

Lynn, I would like to read that post but I cannot find it. Please help. Thanks, Bill

 

[billmo]

Thanks, rewinder. Bill

 

[billmo]

Lynn, I understand that. I am as dumb as an oyster on this thing too. I simply have a tough time making this thing work most of the time. I am amazed at how some of these guys can do all that they do. Wish I could figure it out. Anyway, it is good reading. Thanks, Bill