Confused about group size

[Tyler4565]

I am running a Savage Long Range Precision 6.5 Creedmoor with a Vortex Viper PST 6-24x50. I am loading Winchester brass trimmed to 1.910," CCI large rifle primers, 41.5 grains of H4350, and Hornady Match BTHP 140 grains bullets. Overall length is 2.800." At 100 yards, the gun is a tack driver, usually sending 5 shots through basically the same hole, but at 300 yards, the groups open up to 2-3 inches. I have gotten these same results consistently the last few range trips that I have made. Also, the factory Winchester 140 grain will consistently shoot 1" at 300 yards.

Does anyone have a possible explanation for these results? I have been scratching my head pretty hard...
The green target is 2 separate groups at 100 yards-one 3 shot group and one 5 shot group. The white and red target is a 300 yard group
Common sense says that a group that tight at 100 yards should open up to less than an inch at triple the distance, but maybe something else is going on

 

[LHSmith]

Simple - what else is going on is wind and mirage. Most likely your 100 yard range is a "honey hole" ( terrain surrounding the range that does not see a lot of condition changes). Then going out to 300 yds. conditions sneak in and rear their ugly heads due to the lay of the land and have more time to affect the slower traveling bullet.
Also, define "basically one hole" that could translate into a group size anywhere from 0 to 3/4" or more depending on target paper quality......a poor way to quantify group size.
Lastly, 2 groups @ 100, and 1 group @ 300 is a very poor baseline to try and interpret any meaningful results.

 

[Tyler4565]

LHSmith, I understand what you are saying, but i was wondering if there was anything else besides shooting conditions that could cause that. I have heard before that just because a load shoots great up close, doesn't mean that it will farther away. The range that I shoot at is a 300 yard range on flat ground with target stands at 100, 200, and 300 yards and I only test loads in ideal conditions-no wind etc. I would agree with you 100% that "one hole" isn't a good way to quantify a group, but that is why a posted a picture with a caliper. Also, the results I have seen every time for 4 or 5 range grips are just like what is shown in those two pictures. The thing that I don't like is that there is a factory load that will consistently shoot 1" groups at 300 yards, but I am just attempting to load something that will give the same results with no luck

 

[Tim Singleton]

You have to understand. Without wind flags even tho it looks calm its not and you can't see it
1" at 300 every time is pretty hard to do with wind flags

 

[Tyler4565]

Ah, ok. Do you just put up wind flags where you are shooting, or do you put a couple between you and the target?
Also, is it safe to say that if I am trying to produce a load to shoot very long distance-up to 1000 yards-that a load that shoots like the one pictured at 100 yards would be suitable to do it with? Or would you say that just because it groups well at 100 yards, it may not be an accurate load farther out?
Thanks for the help. Wasn't aware that wind flags could be so crucial even at 300 yards

 

[LHSmith]

The range that I shoot at is a 300 yard range on flat ground with target stands at 100, 200, and 300 yards and I only test loads in ideal conditions-no wind etc.

FWIW, in BR competition, when the flags go from active to dormant during a match( your "no wind ideal conditions") virtually ALL shooting stops....this is no mans land where unseen conditions cause unexplained shots. This is usually when slow moving mirage occurs and in simple terms...you are aiming at a target bull which is actually not where it appears to be.
Take a high power scope, set it up in a solid sandbag rest on a sunny day and simply observe the crosshairs.....the bull will float around the crosshairs within a few minutes of viewing.....the higher the temperature gradient between the ground and the air - the more movement- so you can have this movement anytime of the year. Most people think mirage is absent if the target is not jumping around when they attempt to shoot.

 

[LHSmith]

Ah, ok. Do you just put up wind flags where you are shooting, or do you put a couple between you and the target?
Also, is it safe to say that if I am trying to produce a load to shoot very long distance-up to 1000 yards-that a load that shoots like the one pictured at 100 yards would be suitable to do it with? Or would you say that just because it groups well at 100 yards, it may not be an accurate load farther out?
Thanks for the help. Wasn't aware that wind flags could be so crucial even at 300 yards

Try @ 100 yds flags @ 25/ 50 /75 in same line as bullet trajectory.
Flags are crutial @ 100 yds. Mid range and LR do not allow individual flags....only the range flags are used and I believe they are at or close to the target. Most use mirage to read wind conditions > mirage is wind you can see.

 

[Tim Singleton]

Also, is it safe to say that if I am trying to produce a load to shoot very long distance-up to 1000 yards-that a load that shoots like the one pictured at 100 yards would be suitable to do it with? Or would you say that just because it groups well at 100 yards, it may not be an accurate load farther out?

I don't shoot past 200 yds myself. I understand that a lot of long range shooters do tune their loads at 100 yds. Although it is a point of contention with some.
Read this thread http://forum.accurateshooter.com/index.php?topic=3814361.0

I would recommend some wooden states and surveyor ribbon for the time being learning to read conditions is not something that just comes easy.

 

[TAJ45]

I'm only a BR wannabe and no guru by any means but it seems I've read that some particular combinations of components and chamberings will yield poor results @ 100 but the same loads/rifle will seem to "home in" at a longer distance, will not grow proportionally and be quite respectable. An explanation has been attempted but I will say I didn't quite "get it".

Not disagreeing - I just don't understand that logic yet.

Interesting that the shooting would stop in a lull.....in a flag free environment.....makes sense but had never occurred to me. The other thing is that when going "long" the midrange trajectory puts the bullet waaaay up there for the zephyrs to play with. The lowly 308 has about a 22-24' midrange @ 1k iirc and this would be probably around 2/3 of the way down range, not to mention that it goes subsonic around 930 yds. Falling like a stone.

A challenging sport to say the least.

 

[CharlieNC]

How did you work up your load? If it was not based on a ladder/OCW type of trial to minimize POI shift vs charge weight then it could be that straightforward. As mentioned 300 adds more challenges to the shooter as well, and I usually do my load workup at 200 to get a better POI signal while maintaining better mirage and wind control.

 

[Sniper338]

Personally I would work at developing a load at a longer distance than 100 yards. You have a 300 yard range, load develop at 300 yards and find a load that bug holes at 300.

I will personally step out and say that its very likely that the load you are using is not the right load. Yes it may shoot good at 100 yards, but that is not exactly what you are saying you want. Many times loads are deceiving, they shoot good close, but open up quick further out... Your 100 yard groups look clover leafed, that tells me it isnt the right load for longer ranges. At short range, personally I look for a load that all bullet holes line up very well vertically, then I start with that and test more out further...

best I can describe what I see with your shooting here:

If you took 3 different lasers and mounted them in a triangle fashion with the same space apart from one another, and pointed them at a target at 100 yards, they are all zerod and hit the target in the same place at 100 yards... BUT if you remove that target at 100 yards and dont touch the mounted lasers in the triangle shape, behind that 100 yard point the laser beams cross paths and open up again... Thats what I see - far fetched example I know.

If you understand that example, that explains your right side up triangle group at 100 yards, then your upside down triangle at 300 yards..

 

[jlow]

OP, those rounds that you had going through the same hole at 100 yards, did you ever chronograph them? The reason being that at 100 yards, you are mostly shooting flat and MV variation does not significantly affect group size, this changes as you go out further as significant MV variation will cause vertical stringing. FWIW, you are looking for groups with SDEV of 10 fps or less.

If you go to Eric Cortina 100 yard load development thread, the one with 21 pages and 200,000 plus views, guess what he always ask for other than the targets?

 

[Dos XX]

Chrono your loads then chrono the factory loads that shoot great at 300. You may learn something.

If the factory loads shoot 1" at 300, why are you trying to load your own? Kidding. Kind of?

 

[dkhunt14]

If factory loads constantly shoot 1 inch groups it must be something in your loads or loading. Runout, wrong load, seating depth or bullet tension could come into play. Another thing I didn't see mentioned is making sure the Parallax is out of your scope. I always bobb my head up and down and back and forth and make sure the crosshair doesn't move. If moving it can really open up groups at distance. Matt

 

[Tyler4565]

All great suggestions. I do chronograph my loads and all have been within 15 fps

I want to load my own because I think I should be able to make something better than the factory loads at about 1/3 of the price.

 

[Tyler4565]

dkhunt14 I definitely agree with you that it must be something wrong with my loads. The weird thing is that the factory loads don't shoot near as well at 100 yards as my loads do, but further out the factory loads shoot a lot better than mine do. The factory loads shoot around .75" at 100 yards
I am trying to figure out what causes this and whether I should abandon this load and start over with trying to find one because I have never had a load that shot so well up close but so bad far away

 

[jlow]

You can eliminate any common variable that both your reloads and factory ammo share like the rifle, scope, etc. Of course, this assumes that you shot both your reloads and factory ammo on the same day

 

[johnfred1965]

It could be your rifle simply doesn't like that bullet. I couldn't hit a barn with any powder charge shooting Sierra 107's out of my 243. I switched to the 105 Amax at it shoots like a laser. My Friend's 243 is the exact opposite with these loads, Doesn't like the Amax. If you know someone who has some other brand bullets, give them a try. If you don't want to buy an entire box of bullets for experimentation, one company makes sample packs of many different bullets. Just my $.02

John

 

[jcampbellsmith]

All great suggestions. I do chronograph my loads and all have been within 15 fps

I want to load my own because I think I should be able to make something better than the factory loads at about 1/3 of the price.

Keep in mind that your time isn't free.

Regards

JCS

 

[Park ranger]

No one mentioned parallax. That's my guess.