Questions about ladder testing.

DaveMachine

DaveMachine

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So I was reading about ladder testing on another website so I decided to give it a try. My results weren't exactly encouraging as I could distinguish no discernible nodes.

My main problem seems to be that my loads with heavier powder charges did not consistently hit above my loads with lower charge weights. Now, it seems to me that I just need to shoot better and suck less but I'm wondering if my 300 yard range is not long enough to do this type of testing.

What say you, reloading gurus?
 
I had the same problem so I tried firing three round groups with each powder weight, measured each group the started working with the best groups.
 
Hmm, I was hoping to avoid that so as to expedite the whole process. The method I was reading about required that I do a coarse ladder test, followed by a fine ladder test and finally 3 or 4 5 shot groups once I had things narrowed down.

Maybe I'll break out the camera so you guys can see what I'm talking about.
 
300 yards is plenty far (100 also works).

What kind of rifle/scope setup is it, what bullets are you using? How much did you change the charge each time (or what was the spread from your lightest to heaviest charge)?


I'm not familiar with the target you used... is the group about two inches high by about three inches wide?

What I see in this group, is that there is no noticeable effect on POI due to powder charge changes. This is good, BTW - so far this is saying, "the powder charge doesn't matter at 300y, all the shots go into the same group"/
 
It's a Tikka T3 Stainless Varmint in 6.5x55 with a Falcon Optics 5-25x50(56?) on top. Not the greatest optics, I know.

I'm using RL-22 and started from 45.2gr to 47.3gr (in .3gr increments) w/ 142 Sierra Matchkings and CCI large rifle primers all in Winchester brass that has been sorted by weight*. I had two more rounds at 47.6 and 47.9 but I mixed them up and lost track of which round was what charge weight.

The target is a 6 inch sticky target on a cardboard backer.

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*I wasn't sure how fussy I should be in sorting my brass so I just kept everything within 1gr of each other. IE 182.0-182.9; 183.0-183.9; etc.
 
I don't have load data in front of me for RL-22/SMK142/6.5x55 so I don't know if this is min/mid/max/etc. (BTW nice load combo, you ought to get really good results with it).

I don't know how much shooting experience you have, or how good your shooting setup was the day you did your testing (did you have a solid rest or bipod, did you have a rear bag, did you have a good solid bench, were you happy with the shots you were breaking, was the range sheltered or did you have any readable wind indicators etc...). BUT even ignoring all that, what I see in the photo you've given is a ~1MOA 8-shot group at 300 yards. Which is pretty darn good on an absolute score, period, and even better when the specific factors are taken into account (expect for shot #8, the vertical is great; with shot #8 it's still damn good; these all had different charge weights, over a 2.5 grain interval).

By all means do more load development and tweaking, but realize that even right now you are in a very good position. You could set your powder measure to throw 46.5 grains, use your as-thrown powder charges (not weighed and trickled), and you will have ammo that ought to shoot an honest MOA (which is a different unit of measurement than an Internet MOA ;-)
 
Max load for RL-22 in my Sierra manual is listed as 45.7gr but I'm assuming that's a bit lower for the old Krags out there.

I was shooting from a concrete bench with a bipod and an old sock filled with cat litter (lol) as my rear bag. I'd much prefer to shoot from the prone to be honest but sometimes you get fudds/range nazis that like to gripe about anything. :p

The firing line itself is sheltered and the wind the range receives is typically from behind, that said there wasn't much wind that day. No wind indicators down range.

When I first looked at the shots I was drawn to shots 4, 5 and 6. Would it be worth while testing those 3 charge weights with 10 shot groups now?
 
DaveMachine said:
Max load for RL-22 in my Sierra manual is listed as 45.7gr but I'm assuming that's a bit lower for the old Krags out there.
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Likely true. Carry on, but do be careful. One thing to be careful about with the 6.5x55 is that a lot of the really good bullets available for it have unusually long shanks (the striaght cylindrical portion). If there is a small difference in shank diameter (for instance I seem to remember that Lapua 139 Scenars are .0008" larger than Sierra 142s), that can make a much bigger difference in pressure than you might experience in a calibre in which the typical bullets you use have much shorter shanks. So when you change bullets, or load for a different 6.5x55, really do do the various basics "start low and work up" etc. I have a wrecked bolt from an M96 to remind myself...

I was shooting from a concrete bench with a bipod and an old sock filled with cat litter (lol) as my rear bag. I'd much prefer to shoot from the prone to be honest but sometimes you get fudds/range nazis that like to gripe about anything. :p

The firing line itself is sheltered and the wind the range receives is typically from behind, that said there wasn't much wind that day. No wind indicators down range.
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Sounds like quite a good setup, including the sock; might not sound elegant but it should work well.

When I first looked at the shots I was drawn to shots 4, 5 and 6. Would it be worth while testing those 3 charge weights with 10 shot groups now?
Click to expand...

Most likely a case of your eyes playing tricks on you. You're looking at three of eight shots, which are inside what is already a completely respectable group.

Are you going to be shooting this at 600 yards and less, or were you interested in shooting it to 1000?

If you want to get good results at 1000, there is some more work that needs to be done, using either a chronograph or actual live firing at 800+ yards (in order to tune your ammo so that its velocity is consistent, so you don't get vertical stringing at long range).

If you are shooting at 600 yards and less, then if you are using good bullets (you are), pretty much anything that shoots a good group for you at 100, will shoot a good group all the way out to 600 and actually a bit further too.

If all you want is good 600 yard ammo, load up 10 (or 20) rounds of a middle charge weight (any one of #4, #5 or #6 ;-). Take it to 100 or 300 yards, and fire it as carefully as you can. If it shoots well, your load development can be done right then and there.


(BTW you mentioned that you weight-sorted your brass into 1-grain bins; that's plenty good)
 
rnbra-shooter said:
BUT even ignoring all that, what I see in the photo you've given is a ~1MOA 8-shot group at 300 yards. Which is pretty darn good on an absolute score, period, and even better when the specific factors are taken into account (expect for shot #8, the vertical is great; with shot #8 it's still damn good; these all had different charge weights, over a 2.5 grain interval).
Click to expand...

Hmmmm. I never thought of it that way. Thank you for the insight. :)
 
The hardest thing about load development for me is knowing when I'm shooting well enough to accept the groups and vice versa. Some days I just have to do it all over again.
 
One thing I have noticed many times when doing the ladder test is that just because the powder charge is more doesn't necessarily mean the shot will print higher on the target.

The last time I used this method (308 win) I started low to high, in .5g increments. The first 10 or so shots printed as predicted, stacking higher and higher on each other. Then the shots started to print left of the last shot for about 2 or 3 in a nice horizontal string. Then started to print lower and lower for the remaining 5 or so shots. Total vertical dispersion was about 5" from the first shot to the last shot before they started printing to left. That horizontal string measured about 1.5" and the last 5 shots, which were the hottest loads and started to print low, measured about 3". It was very interesting to see this pattern form on the target. It happens often.

I also see this when load tuning in benchrest. Typically when vertical is seen in the groups you increase the powder charge. At some point the load will begin to be a little hot and it will start to print lower than it should.

Once I find what looks like a good node, I'll load up some cases with powder charges above and below the "node" and shoot some 3 shot groups to narrow things down. I do this at 200 yards. Once I've decided on a load, I'll practice with 5 shot groups to make sure all is well and consistent.

One thing that I have recently learned and I think is very important (I think rnbra touched on this) is that, if you've found a load that is accurate and even with charges slightly higher or lower, the accuracy or POA doesn't change, you've found a great load because it is not sensitive to slight changes in powder charge.

The ladder test can be tough with very accurate rifles as it can be difficult to discern what shot was what. Whatever target I'm shooting at, I always have a blank target beside me at the bench and once I make the shot, I view it through my spotting scope and then plot it on the blank target. Saves me a lot of " ah s**t I'll have to come back and redo this all over again" days.

One more thing. It's important to have some sort of wind indicator at various points along the bullets path. "A shot without wind flags [when tuning] is a wasted shot"
 
A bit of an update here:

I settled on 46.4gr of RL-22 with no additional testing and it seems to have worked REALLY well.

300 yard target.
http://img35.imageshack.us/img35/1294/300kh.jpg

My only issue now is that it seems to drop like a stone. From my 200 yard zero there seems be about 8-8.5 inches of drop - is this normal or should I be loading to higher velocities?
 
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