# You don't know what you don't know till you know what you don't know.........Yogi Berra

#### Hummer

OK you have a good shooting load for your rifle and you want to know how much it drops at different ranges.

You have a ballistic calculator on your computer but how good is it?

Probably not very good.

At Aberdeen Proving Ground we had the Army Ballistic Research Lab and had computer systems with chronographs running in the 5 digit figures price range.

They told me ballistic calculators are only right 5% of the time. If fired on the range your program might be dead on at 300 and 700 yards and off everywhere else.

Yogi was right.

Make up a target 4 ft wide and 8 feet high and put thin plywood or paneling on it and cover it with news print. You can get end rolls of news print from your local paper.

Zero your rifle for POA/POI at 100 yards. Place a new target bull at the top of the board. Using a weight and string draw a vertical line through middle of the target you aim at to the bottom of the target. From 100 yards shoot 3 shots.

Move back to 200 yards shoot 3. Then 300, 400 etc

Keep this up till you get to where your shots are not on the board.

You never touch the adjustment knobs.

When you finish measure down the center from the bull you aimed at each time and record how many inches below you hit and take the average. At Aberdeen these measurements were in millimeters.

Also measure how far the shots drift to the side at each yard line.

When you get through take the average elevation for each three shots and compare them to a ballistic program and see if they match.

Oh yeah you gotta do this in a no wind condition for best drift data.

At Aberdeen we did this for three rifles shooting 3 ten shot groups each and put all data on a sheet and sent it to a lab and they put data in a computer and the computer plotted the shots told us the size of each 10 round groups and calculated center of each 10 round group and the center of all three 10 round groups and plotted them and then averaged all three rifles for 9 ten round groups. No sights knobs were ever touched.

Our target was 32 feet high and 32 feet wide. The range was only 2500 yards long.

This is why when you see trajectory data from Aberdeen Proving Ground printed out you know it was from actual firing and not from a computer but the actual data is compared to computer projections.

CIP John Unertl was making the Marine Corps Sniper scopes in 79. He told me he had received five ballistic programs from five different sources and none were correct and none matched either. He asked me to get him data on M118 Match and I did and the data I gave him was right on the money.

When you die if you run up on a bunch of rag heads from Fallujah ask them if what they think of Marine Corps Snipers as they took out a pile of them and the methods they used was remarkable.

What is this Aberdeen Proving Ground you speak of? Oh wait, I heard you the 1st four times....
I kid, I kid....

#### slimmer13

Yeah I'm not going to do any of that. Strelok has been dead on for me at 400, 600, 720, and 1k. I figure it is close enough.

That said, ballistics calculators are only as good as the data put in. Manufacturers have been known to wildly inflate their listed BCs. Also a quality chrono like a Lab radar is a must because the cheapo ones can be quite inaccurate.

I think that if your ballistics calculator is off, simply verifying your data and adjusting as needed is easier than the method described in the OP.

#### Andy54Hawken

I like to keep my shooting simple...
Once I find a load that both my rifle and I shoot well with...
I simply practice with that ..at various distances , shooting positions ( both on and off the bench ) and in all kinds of weather and lighting....
I try to do this till my shooting with that rifle and load is second nature and an action that I can do without much thought.

'Course good shooting , or good shooting practices , like anything that is individualistic , will vary drastically between what one person sees as good shooting / practices and another person.
Andy

#### MannyGlocks

The title of this thread reminds of Secretary of Defense Donald Rumsfeld.

#### ilikegunspdx

Does ur proving ground measure the actual velocity for every shot or does it use entered data?

No rounds will have exactly the same velocity readings shot after shot in the real world. But the computer uses an assumed, entered, consistent velocity. As the distance of the shot increases, any change of velocity will have a larger and larger effect on point of impact.

In addition, some types of ammo can have a greater range of variance than others. Fe some eastern block guns that many consider inaccurate can often be simply due to using military ammo that has a lot of variance and groups can tighten up considerably when using high quality ammo.

We flew a refrigerator to the moon and back with the same math and physics running a ballistics calculator.

The math is fine. Check your variables.

#### Flopsweat

Does ur proving ground measure the actual velocity for every shot or does it use entered data?

No rounds will have exactly the same velocity readings shot after shot in the real world. But the computer uses an assumed, entered, consistent velocity. As the distance of the shot increases, any change of velocity will have a larger and larger effect on point of impact.

In addition, some types of ammo can have a greater range of variance than others. Fe some eastern block guns that many consider inaccurate can often be simply due to using military ammo that has a lot of variance and groups can tighten up considerably when using high quality ammo.
That's called Standard Deviation and IIUC it's part of the calculation in some of the fancier programs.

The title of this thread reminds of Secretary of Defense Donald Rumsfeld.
"There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know."
Yup, checks out.

OK you have a good shooting load for your rifle and you want to know how much it drops at different ranges.

You have a ballistic calculator on your computer but how good is it?

Probably not very good.

At Aberdeen Proving Ground we had the Army Ballistic Research Lab and had computer systems with chronographs running in the 5 digit figures price range.

They told me ballistic calculators are only right 5% of the time. If fired on the range your program might be dead on at 300 and 700 yards and off everywhere else.

Yogi was right.

Make up a target 4 ft wide and 8 feet high and put thin plywood or paneling on it and cover it with news print. You can get end rolls of news print from your local paper.

Zero your rifle for POA/POI at 100 yards. Place a new target bull at the top of the board. Using a weight and string draw a vertical line through middle of the target you aim at to the bottom of the target. From 100 yards shoot 3 shots.

Move back to 200 yards shoot 3. Then 300, 400 etc

Keep this up till you get to where your shots are not on the board.

You never touch the adjustment knobs.

When you finish measure down the center from the bull you aimed at each time and record how many inches below you hit and take the average. At Aberdeen these measurements were in millimeters.

Also measure how far the shots drift to the side at each yard line.

When you get through take the average elevation for each three shots and compare them to a ballistic program and see if they match.

Oh yeah you gotta do this in a no wind condition for best drift data.

At Aberdeen we did this for three rifles shooting 3 ten shot groups each and put all data on a sheet and sent it to a lab and they put data in a computer and the computer plotted the shots told us the size of each 10 round groups and calculated center of each 10 round group and the center of all three 10 round groups and plotted them and then averaged all three rifles for 9 ten round groups. No sights knobs were ever touched.

Our target was 32 feet high and 32 feet wide. The range was only 2500 yards long.

This is why when you see trajectory data from Aberdeen Proving Ground printed out you know it was from actual firing and not from a computer but the actual data is compared to computer projections.

CIP John Unertl was making the Marine Corps Sniper scopes in 79. He told me he had received five ballistic programs from five different sources and none were correct and none matched either. He asked me to get him data on M118 Match and I did and the data I gave him was right on the money.

When you die if you run up on a bunch of rag heads from Fallujah ask them if what they think of Marine Corps Snipers as they took out a pile of them and the methods they used was remarkable.
I do this on most rifles, and will be doing it very soon on my new to me 1895 Winchester in .30/06 with Un Marked Lyman rear sight and post and globe front! Will mark one side for 165 gr bullets/ loads the rifle likes, and the other side will be marked for 180's the rifle also likes! This way, the sight is correctly marked TO THE RIFLE and it's favorite loads, AND' it's also correctly marked for the RIFLES point blank zero!

#### v0lcom13sn0w

......and if ya dont know, now ya know.........

#### Mygrainman

you never know... til you find out

OP
H

#### Hummer

`First off ammo is accepted to a spec which is very demanding to a point. By this I mean the spec has to be somewhat broad to get the ammo through and is conducted with three cut down 1903 actions with accuracy barrels on the and the stock cut off about 2" in front of the action and at the back of the pistol grip so there is just enough wood to hold the trigger guard assembly in place.

Acceptance on 7.62 and larger is done at 600 yards on a range with highpower targets on it.

The targets are 6 feet square when run up and the rifle is placed in a Frankford Arsenal mount (we called it FA MOUNT) and barrel is clamped down at muzzle and front of action. It is pre aimed and is bolted to a concrete mount that weighs tons so nothing is moving when the barreled action is fired

The Gunner will load about 3 rounds into mag and fire the first shot. Another Gunner in the pits will radio back and tell the shooter where the shot hit and he will adjust the wheels and shoot again. Generally the shots are hitting pretty much centered by third shot and he gives the go ahead to fire a 10 round string.
5 rounds are loaded in mag, target is pulled down and pasted up and the gunner fires 5 rounds as fast as he can work the bolt and has 5 additional rounds in left hand and drops them in one at a time and experienced gunners will get off 10 rounds in around 15 seconds.

The pit gunner pulls the target and measures the group and if it is in spec he radios back and tells the line gunner who pulls that rifle out of the mount and gets another rifle and does the same thing. This is done for three rifles. All three rifles have to print acceptable dispersion.

Should a rifle not deliver the line gunner is notified and he gets a box of Reference Ammo out which is a known good lot and each box in that lot is stamped REFERENCE and fires 10. If the Reference Ammo meets acceptance he will shooter the test lot one more string. If it fails again that entire lot is rejected.

As each rifle is removed from the mount and number of rounds fired is entered on the rifle log maintained for each rifle and after firing all three rifles go for a thorough cleaning.

The acceptance rifle barrels normally hold up for 15,000 to 17,000 rounds, then are rebarreled and shot till it goes out. If the lot of ammo fails it is sold as surplus.

Generally Match ammo is the best shooting, then BAll ammo and tracer ammo acceptance is much larger because the weight changes in flight along with the CG.

So no the velocity of each round is not checked but we had chronograph capability to shoot 30 round strings at about 3 second intervals though chronos that coast 15K 35 years ago.

We also had a devices that measured cyclic rates on full autos. You could fire a burst and about 2 seconds later a cash register tape was spit out telling how many rounds were fired and the cyclic rate. You see published cyclic rates for weapons but the are ball park.

For instance M16s has initial acceptance rate which is slower than the rate it will develop once the the parts are "worn in" and they start to cycle faster and increase about 30 rpm. On the Hydramatic-General Motors gun they had to be given a waiver as the parts were produced with a much smoother surfaces and they cycled faster from the get go so to speak.

We also took readings from -65 below to 160F with those devices that were designed by a guy in our office named Dave Perrin who was always coming up with something amazing. For instance he developed a 9MM handgun bullet that punched more ceramic armor that a 5.56 ball round and would punch a Class II vest at 100 yards fired from a 5" barrel. When impacting a body, it stopped quickly. He estimated it would punch 100 layers of Kevlar if fired from a 357 Magnum. Class II vests are 22 layers. IIRC

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#### Heywood

I’ve found pretty big discrepancies in a ballistic calc I favor from cartridge to cartridge. I use them to get me close enough then try to fine tune it to my rifle/bullet/load. Saves me a lot on time and ammo.
I’ve used a few calculators and have settled on Ballistic AE for my iPhone.
It has many of Brian litzs. Info on actual ballistic coefficient of individual bullets so you don’t have to rely on advertised/supplied data.
Ballistic is dead on for me with my 6.5 Grendel load and good with my AR10 load but not so much with my 338 Lapua.
I would love to be able to take the time to do what OP describes. Just don’t have the time.

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