Low SD but bad groups

[Mike Matteson]

If you have different Primers try them and seating depth too. You really never know until you have tried different things.

 

[Window]

can you have really low sd (5) but have bad groups. Person behind the gun? I had a load work up for 6.5 PRC 156 eol and retumbo. Had three strings of 3 shots with eally low sds. But the groups were 2". I was shooting magpro earlier with 156 and had some good sd and 1/2 moa.

The retumbo sting was at the end of the shooting day. May be tiredness. But I don't think so. Just don't want to waste components to re-try.

These were 100 yards shots.

Find your node with a simple ladder test. From there find your jam and and work back until you find where they group the best and take the guessing out of it.

 

[waveslayer]

Find your node with a simple ladder test. From there find your jam and and work back until you find where they group the best and take the guessing out of it.

too many variables with a simple ladder... Use a OCW using 5 rounds to get better results to really find nodes

 

[Beluebow]

Ladder tests don't work?.......Learn something new everyday.

 

[waveslayer]

Ladder tests don't work?.......Learn something new everyday.

By statistics and having POI shifts happen at distance, say a ladder test... a true ladder starts at 600 yds, then yes. You will get impacts that a high, low and all over. Issues will arise! Hence why an OCW works much better. You take a group and use it to track nodes and eliminate variables. Weather, winds, temp stability of powder, cold barrels, hot barrels etc. You can use a ladder but may be chasing your tail or over look a node because of shot placement. And are you that good you can ensure a good shot at the same target every time all the time. Most guys will jerk the rifle, flinch, pull etc.

 

[Beluebow]

By statistics and having POI shifts happen at distance, say a ladder test... a true ladder starts at 600 yds, then yes. You will get impacts that a high, low and all over. Issues will arise! Hence why an OCW works much better. You take a group and use it to track nodes and eliminate variables. Weather, winds, temp stability of powder, cold barrels, hot barrels etc. You can use a ladder but may be chasing your tail or over look a node because of shot placement. And are you that good you can ensure a good shot at the same target every time all the time. Most guys will jerk the rifle, flinch, pull etc.

I can see where you would be right if all ladders were one shot per charge weight. I certainly wouldn't base any data off of one or two random shots.

What if you shot say, 3 shots at each charge weight in a round robin fashion?

 

[blueprairiedog]

My best 200 yard group is double digit on lab radar but when I shoot the 200 match that's what I use if I use h4350 I get single digits but my group opens up to about 1 1/4 inch at 200 I still don't get it maybe it would be different at 500 plus yards I am open for suggestions also

 

[TXTrained]

can you have really low sd (5) but have bad groups. Person behind the gun? I had a load work up for 6.5 PRC 156 eol and retumbo. Had three strings of 3 shots with eally low sds. But the groups were 2". I was shooting magpro earlier with 156 and had some good sd and 1/2 moa.

The retumbo sting was at the end of the shooting day. May be tiredness. But I don't think so. Just don't want to waste components to re-try.

These were 100 yards shots.

Its your Harmonics..Get you a EC Tuner or a EC Tuner Brake.It will shrink those groups up. I had the same thing on one rifle. If you cant get it where you want it then.. Then its your barrel. I hope this helps.GOOD LUCK.. M ine was also with a 6.5 PRC...LOL

 

[L.Sherm]

Most guys will jerk the rifle, flinch, pull etc

And that doesn't screw up OCW tests?
I think you better convince alot good shooters there ladder tests dont work

 

[cjuve]

I will stick to my ladders


Edit to add… long range ladders

 

[DUCKMAN11]

I thought a ladder test was used to find velocity nodes or more accurately, a minimal amount of velocity change with increasing charge weights. Or maybe I'm getting confused between "ladder" and "ocw".

 

[Bob Wright]

I thought a ladder test was used to find velocity nodes or more accurately, a minimal amount of velocity change with increasing charge weights. Or maybe I'm getting confused between "ladder" and "ocw".

Correct. Velocity recorded for each and clusters of "flats" on target vertical dispersion say a lot on barrel harmonics and nodes. It never disappoints to know. Shoot these at 300 minimum.

 

[L.Sherm]

I thought a ladder test was used to find velocity nodes or more accurately, a minimal amount of velocity change with increasing charge weights. Or maybe I'm getting confused between "ladder" and "ocw".

In my opinion your describing the Satterlee method.
When I do ladders its more about bullet impact and vertical in relation to were all the bullets impact in the whole ladder test to determine the " node" the wider the better in both powder, seating and neck tension ladders. I do record velocity but its not the determining factor.
I do 2-3 shot groupings in the ladder test.

 

[Orange Dust]

Actually if the gun groups well at 300 hundred yds it will group better at 100 yds. You are more than welcome to go to the Lab, and prove this , all expense paid if it can be done and repeated. Litz runs the Lab. It has yet to be proven. And ladder tests are also suspect. Dave Thomas has a great write up on Ladder tests and issues with dispersion giving you false data, garbage in garbage out.

Most guys shooting tight groups at 300 and not at 100 with the same load have a parallax issue or need to power down their scope. It was a study done and the conclusion was, "at 300 yards you focus on a more fine target" meaning you focus harder on a small POA. Power down the scope and focus on a small POA at 100 and you will get tighter groups than at 300 yards.

Reach out to Litz and become famous for proving your theory, I don't mean to come of string or insulting, just letting you know that it hasn't been proven, the opposite has.


OP- yes you can have excellent SD and ES and get terrible groups. I did a load work up for some .308 subsonic ammo and had a MOA group with an SD of 116 and ES of 366! And had a low SD group that was 3 MOA... usually good SD means good reloading practices and consistency, not good groups

I'm not going to get into it with Brian but I will with you. 100 yds is just too close to see meaningful differences. We have a 100 yd indoor range. Every rifle I have will duplicate the groups shot there at 300 outside. No idea if it is lighting, their tables, or whatever, but it is pretty consistent. I am not referring to the boattaild going to sleep. Never believed that. I am referring to today's rifles are too accurate to be able to judge loads that close. We don't test enough rounds to have meaningful statistics between loads anyway. Short range only enhances the issue. The more accurate the rifle the worse it is. I believe this is where a lot of the shoots good at 100 but falls apart at 400 comes from.