1 MOA guarantee

[Broc]

I just watched the rest of the video.
For a guy that is usually very careful with his tests and data, this video is junk.

I call junk because he talks about the rifle, but he is including the shooter. His averages over time are averages with a human behind the trigger. The factory claims the rifle is accurate, the human element introduces a variable.

 

[peterk123]

I just watched the rest of the video.
For a guy that is usually very careful with his tests and data, this video is junk.

I call junk because he talks about the rifle, but he is including the shooter. His averages over time are averages with a human behind the trigger. The factory claims the rifle is accurate, the human element introduces a variable.

Good point

 

[dingbat]

If you remove wind, how is a bullet’s dispersion not linear?

Muzzle velocity SD can have a non-linear effect on group size as distance increases because the drop from gravity is not linear, but that’s not going to manifest itself much between 50 and 100 yards. Example: if you have a spicy round that’s 50 fps faster than the average, the vertical dispersion still won’t be even a tenth of an inch. SD and extreme spread won’t have a measurable effect on group size at 100 yards or 50.

You can even get valid group extreme spread numbers from 25 yards. The issue there is that the holes likely overlap so much that it might be hard to obtain other data about the group. It also might be hard to get extreme spread data if the group is REALLY tight. Just because of the fidelity of measuring the holes in the target.

Assuming your less than a tenth of an inch for a spicy round is at 100 yards and not 50, it’s still 5-10%. and that’s just one variable.
Taking the ammo out of it, I was under the impression that chamber geometry and tolerance could have a significant effect on the consistency of things like peak chamber pressures and stability of the round. My thought is those would affect consistency of muzzle and terminal velocities.
I agree that these things wouldn’t manifest themselves much between 50 and 100 yards. Just saying all deviations aren’t necessarily linear so it wouldn’t be a guarantee that a rifle capable of 1/2” groups at 50 would make 1” groups at 100.

 

[PappyM3]

Assuming your less than a tenth of an inch for a spicy round is at 100 yards and not 50, it’s still 5-10%. and that’s just one variable.
Taking the ammo out of it, I was under the impression that chamber geometry and tolerance could have a significant effect on the consistency of things like peak chamber pressures and stability of the round. My thought is those would affect consistency of muzzle and terminal velocities.
I agree that these things wouldn’t manifest themselves much between 50 and 100 yards. Just saying all deviations aren’t necessarily linear so it wouldn’t be a guarantee that a rifle capable of 1/2” groups at 50 would make 1” groups at 100.

I get what you're saying; I just think the non-linear factors don't really show themselves until further distances.

I decided to do the math, and it seems that an additional 50fps (on a 5.56 77gr) should change the POI by 0.051" at 100 yards (99 fps for 0.1"). But, that doesn't mean it's going to be a 5% difference from the 50 yard group. At 50 yards, the shift would be about 0.025" (197 fps for 0.1")

So, even with such an extreme example extreme spread in muzzle velocity, let's say we have the following groups:

Without that "flier" in muzzle velocity:
50 yards: 0.45" group
100 yards: 0.90" group

Add in the flyer:
50 yards: 0.475" group
100 yards: 0.951" group

We would have a 5.56% larger group at 50 yards and a 5.67% larger group at 100 yards. About a tenth of a percent difference. And this could just be due to the higher fidelity available in calculating the amount of FPS necessary for the shift at 50 yards. There could be even less difference if I could calculate fractions of a FPS.

Ultimately, there is no meaningful difference between the groups at 50 and 100 yards, even taking into account the non-linear effect of muzzle velocity differences. The reason is that at 50 and even 100 yards, the external effects on dispersion are still pretty linear. Wind may be more of a factor in the difference between 50 and 100 yard zeros, but I haven't done the math. And I know lots of people have fairly sheltered 100 yard ranges anyway.

 

[Mountain]

Mil-surp would be extremely difficult, I’m sure. Obviously, old milsurp may be different, but with my issued M4, M855, and ACOG, I could get down to 1.25-1.5 MOA when actually checking for groups and I was very happy with that issued rifle/ammo combo.

Irons are tricky. With my competition Service Rifle, back when it had irons, I could get 3/4 MOA groups if I kept my cheek weld. But I had a problem with ever so slightly changing my sight picture if I picked my head up and brought it back down. So I’d have another 3/4 MOA group, but maybe shifted 1/4-1/2 inch over on the target. I blame the AR’s front sight guards . Though, it happens with other iron sights too, and the multi-group spread is evident with 2-3 MOA surplus guns just as much with match guns.

That problem is greatly reduced with a circular enclosure over the front sight so that one can easily center the circle in the aperture circle.

Oh, and my “3/4 MOA” groups, whether irons or optics, grow to 1.5-2 MOA when I do rapid fire stages with 1 shot per second. I just can’t hold as tight.

I need readers and typically wear a +0.5 corrective lens on my shooting glasses to keep that front sight post clear. When I was young both eyes were ~20/13 (better than 20/20) but I didn't give a crap about sub moa groups. I'll shoot my best with a tiny rear aperture but the light has to be very bright for that. Those damn cobwebs are a PITA on dark, cloudy days.

 

[jkelly1229]

Assuming your less than a tenth of an inch for a spicy round is at 100 yards and not 50, it’s still 5-10%. and that’s just one variable.
Taking the ammo out of it, I was under the impression that chamber geometry and tolerance could have a significant effect on the consistency of things like peak chamber pressures and stability of the round. My thought is those would affect consistency of muzzle and terminal velocities.
I agree that these things wouldn’t manifest themselves much between 50 and 100 yards. Just saying all deviations aren’t necessarily linear so it wouldn’t be a guarantee that a rifle capable of 1/2” groups at 50 would make 1” groups at 100.

Butterfly effect

 

[jkelly1229]

I get what you're saying; I just think the non-linear factors don't really show themselves until further distances.

I decided to do the math, and it seems that an additional 50fps (on a 5.56 77gr) should change the POI by 0.051" at 100 yards (99 fps for 0.1"). But, that doesn't mean it's going to be a 5% difference from the 50 yard group. At 50 yards, the shift would be about 0.025" (197 fps for 0.1")

So, even with such an extreme example extreme spread in muzzle velocity, let's say we have the following groups:

Without that "flier" in muzzle velocity:
50 yards: 0.45" group
100 yards: 0.90" group

Add in the flyer:
50 yards: 0.475" group
100 yards: 0.951" group

We would have a 5.56% larger group at 50 yards and a 5.67% larger group at 100 yards. About a tenth of a percent difference. And this could just be due to the higher fidelity available in calculating the amount of FPS necessary for the shift at 50 yards. There could be even less difference if I could calculate fractions of a FPS.

Ultimately, there is no meaningful difference between the groups at 50 and 100 yards, even taking into account the non-linear effect of muzzle velocity differences. The reason is that at 50 and even 100 yards, the external effects on dispersion are still pretty linear. Wind may be more of a factor in the difference between 50 and 100 yard zeros, but I haven't done the math. And I know lots of people have fairly sheltered 100 yard ranges anyway.

Nerd

 

[Cuz]

I just watched the rest of the video.
For a guy that is usually very careful with his tests and data, this video is junk.

I call junk because he talks about the rifle, but he is including the shooter. His averages over time are averages with a human behind the trigger. The factory claims the rifle is accurate, the human element introduces a variable.

You also have to consider the fact that the "variable" introduced by the human can, on rare occasions, make the rifle appear more accurate than it really is, because groups that may have spread out, were actually closer, due to human error. It works both ways, but not at the same ratio.

 

[Mark from MA]

Most of my rifles are cheap ruger, savage or marlin (when they made the x7). Very few factory rifles shoot 1inch at 100 yards with factory ammo. Unless you scour the universe and shoot 15 flavors.

I can tailor a handload at the proper chamber length and usually get those same rifles to get moa.

My ruger 6.5 manbun was an exception. 1 moa with everything. Then I put a magpul hunter stock on it and it got even better. It shoots hornady match cloverleaf’s all day long.

If the rifle can do it shooting under or around 1 inch at 100 has not been an issue for me with a good scope and rings from a solid rest.

 

[Cuz]

I wish I was good enough to shoot consistent 2” groups from a 1 moa rifle/ammo combo at 100 yards. I hope to rectify this over the winter and actually know/learn how to shoot a scoped rifle by the time Spring rolls around.

 

[vicorjh]

I wish I was good enough to shoot consistent 2” groups from a 1 moa rifle/ammo combo at 100 yards. I hope to rectify this over the winter and actually know/learn how to shoot a scoped rifle by the time Spring rolls around.

Project Appleseed. A worthwhile bootcamp ...

 

[Cuz]

Project Appleseed. A worthwhile bootcamp ...

lol, I attended the 25m event at Mansfield last month and earned my Rifleman patch! It was with a scoped 10/22. Of course, my kid also attended and got Distinguished Rifleman with his 10/22 and iron sights. Tough to compete with young eyes and a determined kid.
It was definitely a blast, but 25m is not 100 yds, even with reduced targets to simulate the distances.

 

[lukewarm_fuzz]

I wish I was good enough to shoot consistent 2” groups from a 1 moa rifle/ammo combo at 100 yards. I hope to rectify this over the winter and actually know/learn how to shoot a scoped rifle by the time Spring rolls around.

Don’t let your dreams be dreams !

 

[vicorjh]

It was definitely a blast, but 25m is not 100 yds, even with reduced targets to simulate the distances.

Technique, technique, technique. The skills are transferable and you'll be able to diagnose equipment/ammo.