ammuniiton differences at 100 yards.

[Jimi Jah]

I've found that shooting the same ammo at sea level and at over 10,000 feet lands one inch higher at 10,000 feet.

[ar15barrels]

I've found that shooting the same ammo at sea level and at over 10,000 feet lands one inch higher at 10,000 feet.

That makes sense because the air density is so much lower at 10,000ft.

Here is a fun one:
I once saw a 1/2" elevation shift of my 100yd zero within a 15 minute time period.
It happened to 20+ shooters that were all on the firing line at the same time during a match where we were shooting at 100yd paper targets.

A huge storm came in and everyone's zeroes shifted the same amount.

[19K]

I’m sure someone in here will post that they get sub moa with wolf/tulammo and match is a waste. Don’t listen to them. They’ll never post pictures or film their tests.

2-3 moa for cheapo bull ammo is the standard. 1moa or less for high quality match from a reputable company.

To answer your question, at 100 yards 2-3 inches vs less than an inch. It may not seem like much but move to 300 yards and you’re now at 6-9inches vs less than 3.

[unindicted_coconspirator]

FourT6and2,

Would you share the details of your rifle build and optics?

Thanks,

unindicted

[Preston-CLB]

That makes sense because the air density is so much lower at 10,000ft.

Here is a fun one:
I once saw a 1/2" elevation shift of my 100yd zero within a 15 minute time period.
It happened to 20+ shooters that were all on the firing line at the same time during a match where we were shooting at 100yd paper targets.

A huge storm came in and everyone's zeroes shifted the same amount.

Randall, I find this to be very interesting. Were the POI's high, or low, assuming no change in windage.

If the POI's were 'low', I would suspect that the air density would be higher due to greater water vapor in the air, so that the bullet would lose velocity, resulting in a lower POI.

If the POI's were 'high', I would suspect that warm rising air would have a lower density resulting in a slight increase in velocity which would raise the POI.

In any event, the occurrence you mentioned is very odd: Mother Nature works in very strange ways, indeed.
-P

[ar15barrels]

They all went low.
It was minutes before we had a crazy thundershower.
You could feel how thick the air was while breathing.

Randall, I find this to be very interesting. Were the POI's high, or low, assuming no change in windage.

If the POI's were 'low', I would suspect that the air density would be higher due to greater water vapor in the air, so that the bullet would lose velocity, resulting in a lower POI.

If the POI's were 'high', I would suspect that warm rising air would have a lower density resulting in a slight increase in velocity which would raise the POI.

In any event, the occurrence you mentioned is very odd: Mother Nature works in very strange ways, indeed.
-P

[hermosabeach]

https://shooterscalculator.com/ballistic-trajectory-chart.php

Drag Function: G1
Ballistic Coefficient:0.48
Bullet Weight: 180(gr)
Initial Velocity: 2600(fps)
Zero Range:100 (yd)
Sight Height: 1.5(in)

Range Elevation inch Elevation MOA
1000 -422.47 40.34 -- temp 59

1000 -408.29 38.98 - temp 80

so with this calculation I just changed the temp by 21 degrees and your impact changed 14"



the default Barometric Pressure: 29.92 for calculation above

1000 -408.29 38.98 - temp 80
I changed to BP to 24

1000 -363.35 34.69

So the drop moves from 408 inches with 29.92 to only dropping 363 inches at 24 BP

45 inch change of impact from the only change being BP

[Preston-CLB]

They all went low.
It was minutes before we had a crazy thundershower.
You could feel how thick the air was while breathing.

It looks like my theory about water vapor laden air increasing the air density was the reason for the lower POI's.

Interesting.
-P

[yacko]

It looks like my theory about water vapor laden air increasing the air density was the reason for the lower POI's.

Interesting.
-P

The storm likely brought in a cold front at the same time. Likely dropping temps 5- to even 10 degrees- also adding to the density.

[hambam105]

You can see it with accurate & consistent shooters.

Sacramento Valley Shooting Facility
Summertime temperatures.
7.62X51mm
1,000 yards.


Ambient temperatures will often change quickly. Half minute changes occur are more noticeable
with less efficient rounds during extreme temperature swings.

With less experienced shooters, their group sizes are erratic at extended distances and these moa
temperature related shifts are undetectable for me to see.

[ar15barrels]

The storm likely brought in a cold front at the same time. Likely dropping temps 5- to even 10 degrees- also adding to the density.

I think it dropped 20+ degrees that morning from the previous morning.

[ShaunBrady]

Assuming the shooter does their bit and there arent fliers what could a person reaosnably expect to be the difference between El cheapo wolf / brown bear .223 and decent factory match ammunition at 100 yards? Is it inches or is it a matter of a quarter of an inch or so in terms of a grouping size?

I tested a pair of 223s through a ShotMarker at 100 yards last Sunday. I brought a couple boxes of WWW 5.56 55 grain because I was curious about this.

The first gun was a Mossberg MVP with a 1:9 24" barrel. It's stock except for some bedding work.

20 rounds of the WWW gave a 2.78" group. Breaking that out into the 5 shot groups I would have seen on paper if they were done separately at 5, 10, 15 and 20 shots gave 2.38, 2.35, 2.18 and 2.48". Breaking out 5 shot groups for every shot after 5 gave groups from 1.92 to 2.78". Breaking out 3 shot groups the same way gave group sizes from 0.54 to 2.78". Tracking the zero shift for the groups gave plus or minus a half inch for 3 shot groups and plus or minus about 0.4" for 5 shot groups.

Velocity spread for 20 rounds was 97 fps with an SD of 29. Five shot SDs varied from 19 to 44 fps. 3 shot SDs were between 7 and 49.

You could lose your mind trying to do your part with that ammo.

The quickie 77smk/varget load I use for bulk practice in the gun gave 5 shot groups between 0.8 and 1.0". The 20 shot group was 1.26". The zero floated around between the groups plus or minus 0.25".

The velocity spread and SD for 20 shots was 36 and 12 fps. The 5 shot SDs were between 7 and 15 fps. Typical SDs for Match ammo are 16-17 fps. Sometimes it's less, but the next batch you buy won't be.

The second gun is a RPR with a 1:7 26" Bartlien barrel. The chamber started as a standard 223 Wylde and was then throated to take advantage of the longer AICS magazine. It shoots 75 ELDm.

The WWW accuracy results were similar. That surprised me, I thought the 7 twist would kill the cheap ammo. Even with 2" more barrel, the average velocity was down 175 fps. Some of that could have been a different lot of the WWW ammo. I've had them vary 60-100 fps in the same gun. I think a lot of it was the 0.300" jump killed the pressure.

With the ammo developed for that gun, the 20 shot group was 0.55". ES and SD were 26 and 9. 5 shot accuracy varied between 0.24 and 0.55". SDs were between 4 and 11. The zero only drifted plus or minus 0.125" between the groups.

The point of all that information is to set realistic expectations when you start shooting. We all like to post our best groups and chrono results, but the real question is what do you think the next group or velocity spread will be? Also, if you're trying to hit anything in the real world and not just the last hole in the target, the zero shift that is forgiven in group shooting becomes an issue.

Also, with match ammo, you're buying your way out of herding several other cats beyond group size.

Anything with steel jackets, cases or cores will likely be even worse than the WWW.

[sigstroker]

Randall, I find this to be very interesting. Were the POI's high, or low, assuming no change in windage.

If the POI's were 'low', I would suspect that the air density would be higher due to greater water vapor in the air, so that the bullet would lose velocity, resulting in a lower POI.

If the POI's were 'high', I would suspect that warm rising air would have a lower density resulting in a slight increase in velocity which would raise the POI.

In any event, the occurrence you mentioned is very odd: Mother Nature works in very strange ways, indeed.
-P

A headwind or tailwind can also shift poi up or down.

[whatmeworry]

Last week I shot a 0” sub MOA group with Tula Ammo. Oh, it was a one shot group.

[divingin]

I tried to help a guy sighting in a bolt gun, .308 at 100yds. He was all over the place. Groups were a foot or more. I took a few shots with his rifle and ammo; first couple of shots about an inch apart, third was wide by almost a foot. Second three shot group didn't have 2 shots within about 5 inches of each other. I made sure he was OK with putting my reloads through his rifle, and had him shoot a 5 shot group with my bulk (AR-10) ammo. All 5 in an inch and a half. I put three into about an inch. He had been shooting Winchester white box (ball ammo? Don't remember now); turns out his rifle really didn't like that stuff.