Precision load development question. Chrono or Target Groups? Which one is best?

MuthaFunk

MuthaFunk

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I have been in the works developing a few loads for my custom built target Mosin. I've been running ladder tests for all of them and have my charges zoned down now.

One of my tests revealed nice tight groupings with not surprisingly consistient chrono readings. One of the other very close loads had much larger ES chrono readings and somewhat larger groupings to a certain degree but still very reasonable. If I'm comparing the two, the first charge looks much better because it was tighter on paper but I'm thinking this may not nessesarily be what I'm looking for. Would the second load perhaps be a better load to work with because despite seeing much larger differences on the chrono I observed less error on paper? Could the paper results just be me pulling a couple shots into a more decent group?

My question is when selecting a final charge is it best to go solely off of my Chrono readings or is the final paper results more important. As I've read I think the point of the ladder test is to find a load that will allow slight variances in reloading that will minimize the error on the target. Is this correct? Or is it a certain charge worked out with a rifle will easily deliver consistient FPS out and therefore hit your target where your aiming every time?


I hope I didn't cloud my question up too much...
 
from my limited readings online, majority sources say go with lowest ES/SD then "tune" the load by playing with seating depth. I personally find the tightest group and go from there, but now that I have a chrono I'm going to try by going with lowest ES/SD and playing with seating depth to tighten up the group.
 
I think it depends on the number of shots in a group that you are relying on. 3 shot groups really dont tell you much and a 5 shot group is only slightly better. Repeated groups over top of each other in different conditions will be the "truth" of how the load performs. If you shoot 4 groups of 5 shots each on the same target in one day, you will be able to pickout some amazing 3 shot groups out of there whether its a consistant load or not. I think ultimately what you want is a powder charge that gives you the most reliable, repeatable perfromance (point of impact) in a variety of conditioins. Thats what ladder tests and optimum charge weight tests try to zone in on.

Another thing to consider is that out of all the components you are using, the chronograph is likely to be the most imprecise and inconsistent part of the whole equation. I think putting any faith behind es and sd readings from affordable optical chronographs can be misleading.
 
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RL-300mag said:
Maybe check out Mystic Precision's website.
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I've been there. Lots of good info. I don't think Insaw the answer to this particular question though.

It was my understanding that the Chrony brand chronographs were quite accurate when you get a reading. From my ladder tests aid say my personal experience is it's very accurate. I rarely saw a speed that didn't correlate vertically on paper unless I knew I pulled the shot and marked it on my FPS table.
 
The beta chrony's are actually pretty good as far as ES/SD go. What your actual velocities are is a little more hit or miss.
 
Groups that exhibit low deviation should hold together at longer distances. A good group at 100 with a large velocity spread will fall apart at greater distances. Decide what distance you want the load to perform at then choose the method that will help you get there. If all you want is 100yds then go for the smalllest group regardless of ES&SD. If you want to stretch your legs 400+ you might want to go with the low ES&SD to keep your vertical spread to a minimum.
 
Go with lowest ES/SD for at least 5 shot groups. At least 5 shot groups and be sure your chrono is accurate and that you the shooter is not the biggest variance.

Last set of test on 308 the lowest ES/SD had best grouping.

PS Post some numbers cause good/best/poor... is kinda meaningless.
 
RL-300mag said:
Maybe check out Mystic Precision's website.
Click to expand...

On Jerry's site under "tech" is an article about load tuning. It's worth reading.

It's my understanding that the chronograph should stay in its case until the very very end of your tuning exercise, and then only bring it out to get a velocity for your ballistics calculations.

Base your charge and seating decisions/choices on vertical dispersion at 2 or 300 yards. Cheat like crazy - bags, rests, no wind, etc - pull out all the stops to eliminate you as an error source.

Took me a while to subscribe to this, but now it makes sense. Your goal is accuracy, not numbers on a sheet or readout - they are a surrogate - so why not use the actual outcome as your decision making tool??
 
burnaby said:
Go with lowest ES/SD for at least 5 shot groups. At least 5 shot groups and be sure your chrono is accurate and that you the shooter is not the biggest variance.

Last set of test on 308 the lowest ES/SD had best grouping.

PS Post some numbers cause good/best/poor... is kinda meaningless.
Click to expand...

Will do! I'll have to wait until tonight to post my chrono readings as I dont have them right now however I do have the target pics.

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As you can see the 48.8 gr load shot the tightest group and had the lowest ES on my Chrony of the three. When you see the 48.5 gr ES vs the group on target you'll see that they still have a decent group. Again, I feel like that could have been me pulling a shot into the group. I was using sand bags but am still working on my technique.
 
Notice how your 48.2 is vertically oriented, whereas the 46.8 is more horizontal?? That fits with your ES being bigger on the 48.2.

One other comment - not sure what powder you're using (you may have posted it, sorry, too lazy to look back) but 48.8gr seems heavy for most powders I've seen. Are you seeing any pressure signs?? If so, there's likely another accuracy node (or maybe 2) lower down that will save your brass and your barrel......

Another comment, sorry..... I did something I swore I'd never do - I bought a rest. You can get a Caldwell "the Rock BR" for about 180$. It could easily save you 180$ in components and barrel life.
 
^^^ I'm loading 7.62X54r 150 gr PPU SP with Varget.

I'm going to proceed with testing the 48.8 gr loads. I'll spin up a batch of 50 and see how the targets look. I may play with seating depth with half of the 50.
 
MuthaFunk said:
^^^ I'm loading 7.62X54r 150 gr PPU SP with Varget.

I'm going to proceed with testing the 48.8 gr loads. I'll spin up a batch of 50 and see how the targets look. I may play with seating depth with half of the 50.
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Don't play with seating until you pick a powder charge. It gets way too confusing.

Read Jerry's article - it's quite helpful, even if you don't follow his plan.
 
You can look at 100 yard groups and hope they mean something at long range. You can look at chronograph results, hope that they are actually correct, then guess whether they are going to matter at long range. (The chances of them not making any difference at close range are pretty good.)

Or, you can go to the longest range you are going to shoot at and just see what it does.
 
Didn't see the distance (100m???) or size of grouping.

If you look at the challenge thread that requires five 5 shots under 1/2" group all on same sheet of paper. Good start on precision shooting. Until you know your rifle and you can do 1/2" groups at 100m best to concentrate on shooting techniques. Start tweaking to get consistent <1/2MOA groupings.

MuthaFunk said:
Will do! I'll have to wait until tonight to post my chrono readings as I dont have them right now however I do have the target pics.

...

As you can see the 48.8 gr load shot the tightest group and had the lowest ES on my Chrony of the three. When you see the 48.5 gr ES vs the group on target you'll see that they still have a decent group. Again, I feel like that could have been me pulling a shot into the group. I was using sand bags but am still working on my technique.
Click to expand...
 
burnaby said:
Didn't see the distance (100m???) or size of grouping.

If you look at the challenge thread that requires five 5 shots under 1/2" group all on same sheet of paper. Good start on precision shooting. Until you know your rifle and you can do 1/2" groups at 100m best to concentrate on shooting techniques. Start tweaking to get consistent <1/2MOA groupings.
Click to expand...

Yes those were at 100 M. Your absolutely right in that I need to practice on my technique. I've never been able to test myself with a truely precise rifle and ammo. I have shot plenty of sub 1.5" groups with Chinese milsurp ammo and my home bubba'd Mosin which has led me to reloading to achieve tighter groups.

I have a cheap light sled and sand bags that I switch between for testing. I don't think it's possible this particular rifle could make it into that challenge even with a well practiced hand. I could be wrong but it's not likely to get sub 1/2" unless by chance.
 
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