Group issues long range

[Harvey_NW]

Some loads will shoot extremely well at 100yds but fall apart at longer ranges. I work up loads at 100 and then test at 500.

That's not really a thing, with all things considered dispersion is linear. If a load shoots tight at 100 yards but falls apart at distance, it's highly likely either unaccounted for winds or shooter error.

*edit* - I should have said mostly linear at reasonable distances, not as an absolute. I understand that things like MV SD, BC variability, etc. amplify at longer ranges, but in the context of the OP referencing 300, 400, 500 yards, those are not likely the cause of impacts way outside the expected variability at those distances. If anyone is interested in hearing it from a ballistician, listen to this.

 

[huntsd]

Results?

havent got back out there yet.

 

[Fujicon]

First thing I'd check is scope. Much to my personal embarassment I had a very similar situation to the OP's. Turned out the scope was not installed properly. That's after I'd installed probably 40+ scopes without a single hiccup, but physics don't lie. I wasted two boxes of 300 PRC before I nailed it down, checking the scope all along and thinking it was secure. Finally rectified after a full reinstall. Life has a funny habit of reminding us to recall those fundamental lessons we learned way back when.

 

[jimh406]

The farther the shot the more basics like follow through matter. My guess is the rifle is fine, but the shooter is not.

 

[Sadie]

If extreme spread is not small vertical dispersion will show up at longer ranges but not so much at 100 yds.

 

[Quicksilver]

That's not really a thing, with all things considered dispersion is linear. If a load shoots tight at 100 yards but falls apart at distance, it's highly likely either unaccounted for winds or shooter error.

Not 100% true, I had a load fall apart vertically at 800yds that was consistently sub 1/2 moa out to 450yds. The load had single digit SD and ES around 12fps and looked very promising until some distance. A primer swap fixed the load. Slightly better accuracy, but the group shape was better overall and held together at 800yds. Slightly slower velocity, but same SD/ES after the primer swap.

 

[Harvey_NW]

Not 100% true, I had a load fall apart vertically at 800yds that was consistently sub 1/2 moa out to 450yds. The load had single digit SD and ES around 12fps and looked very promising until some distance. A primer swap fixed the load. Slightly better accuracy, but the group shape was better overall and held together at 800yds. Slightly slower velocity, but same SD/ES after the primer swap.

So this is kind of why I said all things considered, meaning everything had been substantiated with at least somewhat valid sample sizes before coming to a conclusion. Things like "single digit SD and ES around 12", "sub 1/2 MOA", and "primer swap fixed it" make me question that. If you have significant data of high shot counts over a chronograph, establishing a baseline of precision and zero with a large sample at 100 yards, and measured conditions with shots impacting well outside the expected dispersion, I would be very surprised to see that result. But based on the context, I would presume you're just dealing with noise.

 

[Quicksilver]

So this is kind of why I said all things considered, meaning everything had been substantiated with at least somewhat valid sample sizes before coming to a conclusion. Things like "single digit SD and ES around 12", "sub 1/2 MOA", and "primer swap fixed it" make me question that. If you have significant data of high shot counts over a chronograph, establishing a baseline of precision and zero with a large sample at 100 yards, and measured conditions with shots impacting well outside the expected dispersion, I would be very surprised to see that result. But based on the context, I would presume you're just dealing with noise.

Could be noise, but then explain how some high ES loads can shoot tight groups at distance (800-1000yds for example) as well? That goes against what the data is telling you should happen. Majority of the time you follow the rules, but there are outliers of that periodically. Take all the data you want, but the target doesn’t lie. This is for hunting distances specifically I should add.

I’ll take horizontal dispersion all day for reasons like you mentioned, wind and whatnot. That dispersion is expected. With multiple passes over a chronograph and a good sample size for velocity, vertical dispersion is very hard to make happen, and for my testing it wasn’t a game of inches, it was target impact, then low 2 feet, then just beneath target, etc. primer swap with all else being the same with the load and I’m banging the target multiple times. I’ve tightened up a few loads swapping primers as well, although these have been closer distances of 450yds so can’t compare to my one example at longer ranges.

For my sample size you question for my results, it’s at least 20 shots at 100yds and about the same at distances from 450-600yds. Not all at once but at separate times in different conditions. I usually don’t do more than 3 shot groups in my hunting rifles. Instead of slinging lead for extended periods of time into a group I’ll challenge myself to make impacts on specific target sizes in different conditions to simulate the vital zone of an animal. I’ll then average the group sizes over those days to get a baseline for the rifle. If I can have repeatable results, on different days in different conditions, I feel confident in my numbers. If someone else was shooting I’d definitely be questioning shooter error as well because I have seen it first hand, but I’m confident in my ability to have repeatable results pulling the trigger behind multiple rifles.

 

[Harvey_NW]

and for my testing it wasn’t a game of inches, it was target impact, then low 2 feet, then just beneath target, etc. primer swap with all else being the same with the load and I’m banging the target multiple times.

This is the only outlier I see, it's possible you got a bad batch of primers, or had something unknown happen when charging cases.

 

[Quicksilver]

This is the only outlier I see, it's possible you got a bad batch of primers, or had something unknown happen when charging cases.

Velocities were recorded while shooting with my labradar and they were consistent, bad primers could be the case. It’s fixed now so that’s all that matters

 

[Formidilosus]

Could be noise, but then explain how some high ES loads can shoot tight groups at distance (800-1000yds for example) as well? That goes against what the data is telling you should happen.

That’s easy- velocity SD and ES very often have little to do with grouping even at relatively long range. The barrel is oscillating while the bullet leaves- sometimes the barrel is at 12 o’clock, sometimes 6 o’clock. I have a bunch of rifles/loads that have 70-100 FPS MV ES, and yet hold sub 1.5 MOA (quite a few significantly les than that) at 800 yards.


As far as the rest, maybe. I have yet to see a rifle whose 30 shot ES group is signify different at 600 to 800 yards than it is at 100. There is nothing magical happening that makes groups fall apart. Every time I have seen it with someone, it has been a case of small sample size at short range and then seeing what’s happening at long range.

 

[Quicksilver]

That’s easy- velocity SD and ES very often have little to do with grouping even at relatively long range. The barrel is oscillating while the bullet leaves- sometimes the barrel is at 12 o’clock, sometimes 6 o’clock. I have a bunch of rifles/loads that have 70-100 FPS MV ES, and yet hold sub 1.5 MOA (quite a few significantly les than that) at 800 yards.


As far as the rest, maybe. I have yet to see a rifle whose 30 shot ES group is signify different at 600 to 800 yards than it is at 100. There is nothing magical happening that makes groups fall apart. Every time I have seen it with someone, it has been a case of small sample size at short range and then seeing what’s happening at long range.

I guess my SD/ES question was more rhetorical and I agree, bad harmonics will throw all your good numbers out the window

And my long range sample size was very small, but it showed enough that I didn’t need to continue further. Usually I won’t spend as much time at close range, if something looks promising I’ll take it farther out and see how it does and spend my time there continuing testing.

 

[Harvey_NW]

bad harmonics will throw all your good numbers out the window

I don't believe in this either. Like I said initially, if it shoots good and it's proven at short range, it will do the same at long range. You just have to "do your part" calling wind

 

[Quicksilver]

I don't believe in this either. Like I said initially, if it shoots good and it's proven at short range, it will do the same at long range. You just have to "do your part" calling wind

Everyone has a lot of their own opinions on everything, reasons as to why and why not. But whatever you’re doing, the target will let you know if it’s right or wrong! There is no right or wrong answer if it works.