Ladder test/accuracy and velocity ES

[jrock]

I recently did two ladder tests on two different days with diffing weather conditions. Once I brought the data back to the "lab", I noticed that the groupings were about the same regardless of weather...no surprise there. I found that the most accurate group for my .243 shooting 100 gr Hornady Interlocks was 43.0 grs of IMR4350. Less than 2" group at 400 yards. It had a velocity ES of 30 fps or so. Reading some articles online, they suggest a much lower ES for long range shooting. I dove into my data some more and discovered that the 42.8 gr charge had an ES of less than 5 fps yet grouped 4" at 400 yards on both days.

Any thoughts on what path I should take? It seems to me that consistently tight groups would be the ticket and just toss the velocity ES data.

 

[gohring3006]

I would mess with seating depth I know interlocs have a canelure my 06 loves those interlocs seated to the canelure and no crimp but I would seat them in or out slightly to see if that helps. I have noticed that 500 is about the limit on those interlocs with my rifle but that's with the 165s I haven't tried 180s yet I just went to 200gr.smk for the long pokes

 

[Canadian Bushman]

It depends on the shooting you plan to do. If its a mid range rifle you use for hunting id go with the more accurate load and shrug off the es. When in comes to long range stuff, that es will start to catch up with you.

 

[MNbogboy]

You didn't mention how many shots per group, if it was only 3 or 5 the ES differential could easily reverse with a few more shots in each group...ES and SD averages are far more revealing when 10 or more shots are taken per group or are compiled over several groups within several "outings"....Other things that should be taken into consideration are the bag manners and consistency over every shot....A different shoulder pressure with each shots can change ES dramatically....

In my opinion the actual results on the target (with repetition) are more of a factor than the chrono results when decisions are at hand....

As mentioned earlier fine tuning depth with both loads may even out or turn your present results around....

Also as mentioned a true representation of ES over longer distance will be a factor, but at 400 yards your ES results may or may not show up...A controlled test at 600 or more may answer your initial question.

Usually your first cold barrel shot will drive the ES and resultant SD up with the first group compared to subsequent groups....This cold barrel shot actually is the most important one....Getting that shot (usually slower) to group with the rest is very important....In this case your ES may be higher but consistent POI at moderate ranges can be attained....Again that lower velocity at longer ranges will not allow the tightest groups....This is LRH and we have to count on cold barrel #1...

My $.02,
Randy

 

[jrock]

Groups were 3 shots each done in a round robin manner. 7 shot strings with a 5 minute break between strings. Since, I have been thinking of moving to 600 yards to get more group separation. I had done a 100 yard seating depth test with 3 shot groups prior to the ladder to find the optimal depth and results showed little difference with that bullet.

 

[Barrelnut]

I had done a 100 yard seating depth test with 3 shot groups prior to the ladder to find the optimal depth and results showed little difference with that bullet.

Were you monitoring ES and SD during the 100 yard seating depth test? I have noticed ES and SD get better the deeper a bullet is seated sometimes. Seems the reason is that the deeper seating is taking up the extra space in the space in the cartridge and allowing more consistent ignition of the powder.

 

[cowboy]

With your concern of ES versus actual field data. I would ask the question as to what your confidence factor is in your chronograph?

Chronograghs are just like every electronic device - they have their limitations, some more than others. I would never over ride a true shooting field test over 98% of the chrony's data on the market.

If I could consistently shoot 2" groups at 400 yds., I could care less what any chrony tells me.
Stretch that rifle out a little more distance and see what that load does for you. I say let the holes in the paper over ride any electronic data.

 

[4xforfun]

So, you are shooting groups. You are NOT doing a ladder test.

Apples and oranges.

 

[jrock]

I have an F1 Chrony and I've heard mixed reports about it's performance. I went back over my shooting log and noticed that the first day had a little different velocity ES but the pattern of 42.8gr being tighter velocity than 43.0 remained.

100 yard seating depth tests also showed that the most accurate load had a higher ES.

Part of me wants to say, "you can't argue with a 2" group at 400 yards" but the scientist inside of me wants to correlate that to data to my reloading practices to better understand what is going on.

Thanks for the help.

 

[jrock]

So, you are shooting groups. You are NOT doing a ladder test.

Apples and oranges.

Does doing three ladder tests on one target still count? I just noticed group formations and that one was much tighter in all directions than the others despite higher ES and round robin testing on two different days.

I want to get this verbiage right so correct me if I'm wrong but my understanding of a ladder test is a string of rounds shot at LR to find a vertically tight cluster which indicates a "sweet spot" of barrel vibration.

 

[4xforfun]

Does doing three ladder tests on one target still count? I just noticed group formations and that one was much tighter in all directions than the others despite higher ES and round robin testing on two different days.

I want to get this verbiage right so correct me if I'm wrong but my understanding of a ladder test is a string of rounds shot at LR to find a vertically tight cluster which indicates a "sweet spot" of barrel vibration.

Yep, that is actiually what a ladder test is. But looking at how three of the same powder charges did as a group in not importand. If you did the ladder test correctly you would have shot some "warm up loads".....get that bbl pretty warm. Then, shoot your shots slow at a timed intervel. I use a clock and space the shots out to about 60 seconds, depending on the weather (cooler breezy days cool faster than hot still days). That is about right to keep the tube roughly the same temp. If you start with a cold tube and run you shots fast you have just introduced heat induced bbl stress into the equasion. My point is that it might be an hour between shots of the same powder charge, so all kind of enviornmental things could have happend.

When I run more than one ladder test at a time I clean between strings and let everything cool. I also run the second test bacwards...high to low.

When I run a tripple, what I look for is that the clusters happen at the same powder charges. Three ladder tests that show the same clusters....AWSOME!!

 

[jrock]

Thanks that sounds like a good method for the test. Will have to give that a try.