5-Shot Test Group's Size and Shapes

[Kevin]

And no, not every group will exhibit the same elongation and angle. 5 shots will not statistically be repeatable. However, the final load determined by the group testing will always be statistically consistent if properly selected.

Temperature can affect the most accurate load, but typically with our setups, we settle on a load that is temperature stabile. Environmental conditions will change POI. But we get a sighting period to get that centered up.

 

[xcesiv]

I can say with certainty that not all US F-Open team members test the same way. We have different equipment and cartridges amongst us. Some use groups, some use ladders, some do both. Some test from 1000yds, some from 100. Some in between.

But what I will tell you is that most of us can find an accurate (1/4moa@100) load in approx 100-120 rounds after break-in.

That load will remain constant for the life of the barrel and component lots. The lands can be chased if necessary with seat depth to maintain a sufficient group size to be competitive.

We shoot 20 shots for score in up to 20 minutes. If we have a good load, then wind is our biggest enemy.

The results on target are due to understanding the bullet exit timing relative to the sinusoidal vibration of the barrel. You cannot find this without testing. However, the testing doesn't have to burn up the useful life of a barrel either.

I agree with Kevin and have found that there are several different ways to achieve accuracy. For someone to say that there is only one way, that would be an untruth. It is all about Barrel timing and the more consistent your loads are the more success you will have. I loaded and shot more than 8000 rounds last year and had a pretty consistent and successful year. You just have to pick a system and stick to it.
Dwayne Draggoo

 

[Heman]

Bart Kevin has chimed in. Also the 3 shot groups I posted for you on nm forum out of Jeff's gun were to just verify the seating depth before nationals.

 

[chkunz]

I can say with certainty that not all US F-Open team members test the same way. We have different equipment and cartridges amongst us. Some use groups, some use ladders, some do both. Some test from 1000yds, some from 100. Some in between.

But what I will tell you is that most of us can find an accurate (1/4moa@100) load in approx 100-120 rounds after break-in.

That load will remain constant for the life of the barrel and component lots. The lands can be chased if necessary with seat depth to maintain a sufficient group size to be competitive.

We shoot 20 shots for score in up to 20 minutes. If we have a good load, then wind is our biggest enemy.

The results on target are due to understanding the bullet exit timing relative to the sinusoidal vibration of the barrel. You cannot find this without testing. However, the testing doesn't have to burn up the useful life of a barrel either.

Kevin, this is good information. But I keep rereading the original post of this threat and no one is addressing the main point of the thread. "Each bullet seater settings' group will have its unique shape; .............. Repeating the same load bullet seating depth always has the same group elongation and angle;.........."

 

[Depart123]

Meangreen,

I dont think a group pattern reflects where the bore axis pointed for each bullet hole. All bullet's barrel time, trajectories and atmosphere they go through are not exactly the same for each shot.

I will disagree with your first sentence, while whole heartedly agreeing with the second. When a rifle exhibits the same predictible pattern (say, 1.3 moa elipse stringing from 2:30 o'clock to 7:30 o'clock) with multiples of radically different loads, I would say that barrels harmonic tendencies are readily apparent.

Another common pattern is stringing vertically from 1 o'clock to 7 o'clock until a certain pressure is reached, then the group tightens up nice and round. Beyond that, the vertical stays small and the groups start spreading out sideways. I've seen these patterns repeat from multiple rifles in multiple calibers and configurations. I've seen them in my own shooting as well as from looking at many groupings on this very forum.

You don't have to believe me, you can go back and look for yourself.

 

[Kevin]

Kevin, this is good information. But I keep rereading the original post of this threat and no one is addressing the main point of the thread. "Each bullet seater settings' group will have its unique shape; .............. Repeating the same load bullet seating depth always has the same group elongation and angle;.........."

Well, I thought you guys were capable of reading between the lines.

5 shots is not statistically repeatable so the angle and spread may not be identical. But given a statistically repeatable shot count (~20) the shape of the group will be consistent enough to determine a trend taking wind elements out of the test.

Bullet seating depth WILL affect exit timing. Exit timing WILL affect group size. I can typically find a jump distance that will withstand several thousandths of throat erosion before I have to chase it.

 

[Bart B.]

I will disagree with your first sentence, while whole heartedly agreeing with the second.

I don't think a group pattern reflects where the bore axis pointed for each bullet hole. If it really does, then.....

... all bullets are perfectly balanced, have the exact same barrel time, and gas escapes perfectly uniformly around their heel upon exit, they all have the exact same BC because the thing holding the rifle has no variables. The bullets' trajectories are exactly the same varying only in the angle the barrel points upon their exit. And so is the atmosphere the trajectory goes through exactly the same for each shot.

Stranger things happen.

 

[Depart123]

I don't think a group pattern reflects where the bore axis pointed for each bullet hole. If it really does, then.....

... all bullets are perfectly balanced, have the exact same barrel time, and gas escapes perfectly uniformly around their heel upon exit, they all have the exact same BC because the thing holding the rifle has no variables. The bullets' trajectories are exactly the same varying only in the angle the barrel points upon their exit. And so is the atmosphere the trajectory goes through exactly the same for each shot.

Stranger things happen.

So what is your explanation for these repeating patterns then?

 

[Heman]

Bart as I told you in the National Match forum we have data and shooter experience doing this versus what you think and data beats opinion. Realize it may be a haul but I'll cover weekend match fees for youvat atterbury so you can shoot with them and talk/learn more about it.

 

[Bart B.]

Still waiting to see several groups with the same shot hole patterns shot with one load with the same bullet seating parameter.

Post #25 addresses this. The earlier picture in post #10 showing 3 charge weights and 3 jump distances show only 1 group per load. None are the same as seen by me. Close, but not the same. The credibility of one 3-shot group is the same as what some people have to others.

What are the conditions, standards and objectives to certify two or more groups are the same?

 

[Heman]

LOL, I like a person who sticks to their convictions. Kevin has tried to explain it to you Bart, take from it what you will.

 

[Bart B.]

I can say with certainty that not all US F-Open team members test the same way. We have different equipment and cartridges amongst us. Some use groups, some use ladders, some do both. Some test from 1000yds, some from 100. Some in between.

Here's what I was able to do with no load workup at all back in the 1990's. Just used what was popular with no case prep at all save the 200 grain load neck turned and full length sized, 190 grain load in new cases. 30 shots, alternating loads, in 20 minutes time. Pit crew said ES was about 7 inches for all 30, under 5 for each load. Shot from F class open position slung up with rifle on bags.



Here 20 shots at 800 yards from prone and bagged with a 308 Win. Another popular load with 155's in a Palma rifle.



Working up loads is sometimes a waste of time.

 

[CharlieNC]

I don't need to change seating depth to get different group sizes and patterns, just need to shoot the same load on different days!

 

[Heman]

Bart, first nice shooting. Second yes I do agree load dev isn't needed for the tried and true stuff in prone just like in service rifle. For a palma gun and the tried and true cartridges we know the loads, put them together done. When I got my first .243 barrel from Whidden he told me his load I did a ladder and in 12 shots I was done. However if you have a cartridge/powder/bullet combo that isn't well known then you may have to figure out what it is. If my gun is shooting 1/2X ring elevation at a given yardage, yup I'm good. I don't do near the load development they do and I'm more along the lines of what you did. BUT obviously there is a reason the FClass shooters do their testing and do stuff the way they do it. 5" vertical spread is the entire X ring for FClass and that isn't good enough once you factor in environmental conditions. For you and I that is 1/2 the X ring and not an issue. Loads I have that shoot cleans at 1k with nice x-counts but when I switch over to the F-Class target the load isn't good enough. You need to go shoot Fclass sometime then maybe you will understand why they do what they do. I wish I had the old server which had some of the plots stored on it, but we had some that those guys shot where they were using 1/2 of their X ring elevation wise if not less, it was rather impressive to watch to say the least.

 

[memilanuk]

Here's what I was able to do with no load workup at all back in the 1990's.

I was wondering how long it'd take before this got trotted out again. Kinda surprised it took this long...

 

[Kevin]

I like how no two bullets touch. That takes skill that few possess. I'm guessing even back in the 90s you were saving spindles.

Its a known fact today that if an F-Class guy shoots a spindle, he is forever shamed. You must have led that charge. Congrats!


On a more serious note, after testing a 2nd barrel, the charge turned out to be identical, however seating depth was different. To each their own!

 

[Bart B.]

I like how no two bullets touch. That takes skill that few possess. I'm guessing even back in the 90s you were saving spindles.

Its a known fact today that if an F-Class guy shoots a spindle, he is forever shamed. You must have led that charge. Congrats!

I've only shot one spindle out.

Sighters for the 1000 yard stage of a Palma team match. Coach had me put on 7 clicks for wind, first sighter called X at 9, it was an inch right of the letter X. Coach moved me 2 clicks left for second sighter; called it an X at 2. Shattered the spindle. Had to wait for target repair.

I give 68% of the credit to the coach.

 

[Heman]

So Bart with such skill and ability I imagine you still can shoot. Do you still shoot? What kind of scores do you put up?

 

[daniel brothers]

are those bullet holes or magic marker dots....?

 

[glockaholic]

These guys have it figured out. This comes from many thousands of rounds being fired. Short range guys have been doing this for decades
Seating depth is the key

This is the method I use, 2 variables: powder charge and seating depth on the same target/day. I wise gunsmith showed me this. Next explore the sweet spot further.

I don't know the mechanics of internal ballistics but image some gas getting in front of the bullet before the jump is complete. The more jump, the more gas gets in front of the bullet. This is what I believe is affecting the harmonics and pattern shape.