PCC: IRL Trajectory and Ballistic Calculator Do Not Match . . . Why?

[twofewscrews]

I've got a Ruger PCC (9mm) zeroed for 17 yards (50'6" exactly according to the range) that shoots 5 inches high at 50 yards, but according to the ballistic calculators I use, ShootersCalculator.com or GunData.org, a 17 yard zero should have me shooting 2 to 2.3 inchs high at 50 yards. A 50 yard zero makes the hold under more extreme then I'm comfortable with and then it should be and simply adds to my confusion. I know that ballistic calculators are a rough mathematical estimate of what should happen, so I'm not expecting it to be 100% right, but when I run other firearms/calibers though them I get number that match up with real life enough to be useful. When I run numbers for my .357 lever gun, .308 and .22lr rifles they match up to within an inch or so.

According to all the ballistic calculators and other peoples experiences I've found online, a 25 yard zero (or 17 yard zero) should have me shooting either dead on or maybe an inch or two high at 50 yards.

I know my hold under/over out to 50 yards, and I understand its a PCC so a 3 inch spread at 50 yards is acceptable.
This isn't an issue of me not being able to hit where I want per se, but it's something that keeps me up at night wondering is it me, the rifle, the ballistic calculator or what?

Here are my numbers
Ammo: CCI Blazer 9mm 115g BC of .147 traveling at an advertised 1145fps. I don't have a chronograph but according to the net I'll gain about 200fps, so lets says its traveling at roughly 1345fps.
Height over bore: 2 inches
Ruger PCC: 16.12 inch barrel with a 1:10 RH twist
Optic: This shouldn't matter but I'm using the PA SLX 1x Microprism

These are my targets from my last trip to the range. My 17 Yard (50 1/2 foot) zero might be a bit off, but I've had this same issue when perfectly zeroed at this distance and 25 yards. I zero at either of these two distances and am still twice as high as I should be according to the ballistic calculator I use. Even if my zero is a bit off these images accurately represent where a 17 yard zero shoots at 50 yards.

The middle is switching from Winchester to CCI and firing from a supported position. 10 shots on each stickie. The top right is confirming zero firing from a supported position. As the barrel heats up the spread tends to shift right. The other three are firing unsupported, 2 shots each, moving from target to target in no particular order.

This is 50 yards. My hold is at the bottom of the blue (5 ring) where it meets black (4 ring). From the bottom of the blue to the yellow is three inches. The yellow inner is 3 inches in diameter. If your inclined to run check my math the line under distance to the bottom line under notes is 1 inch. That is 50 shots with 5 "flyers"


Am I using crappy ballistic calculators? If so, what do you recommend I use?
Should I double check the distance's of both targets at the range? I don't have a laser but I do have a tape measure.
Is this a function of it being a takedown? ie because its a takedown the barrel is flopping about throwing rounds high . . . or something of this nature.
Is there something I am missing all together?

Thanks for your help in advance.
Please feel free to call me an idiot . . . but also please explain why I'm an idiot

 

[someguy2800]

I would recommend you adjust the scope to hit where you want it to hit at 50 yards and not worry about it anymore.

 

[twofewscrews]

I would recommend you adjust the scope to hit where you want it to hit at 50 yards and not worry about it anymore

I don't worry but I am curious. Its a plinker, not a "battle rifle" or a hunting rifle. The discrepancy between the the calculators and real life differing only occurs for this combination of rifle and caliber and I want to know why. If it was a "battle rifle" or hunting rifle I'd be worried, but its a plinker so I'm curious.

 

[LoonWulf]

If the expected outcome doesn't match what you're seeing in real life then your data input isn't accurate.



I played with it a little bit and couldn't duplicate a 5-in variation....but using 1350 as velocity, .175 bc (calculated based on the velocity loss expected in the ammo spec), and a sight height of 2.5 (thats about what my sub2k is) i came up with 3" over at 50yds with a 17yd zero.

 

[Bwana John]

Sound like the height over bore is not accurate enough.
Remember you are measuring from the bore midline to the scope midline.

 

[twofewscrews]

Sound like the height over bore is not accurate enough.
Remember you are measuring from the bore midline to the scope midline.

I might be off by an 1/8 or so, but an 1/8 shouldn't matter too much.

 

[twofewscrews]

If the expected outcome doesn't match what you're seeing in real life then your data input isn't accurate.



I played with it a little bit and couldn't duplicate a 5-in variation....but using 1350 as velocity, .175 bc (calculated based on the velocity loss expected in the ammo spec), and a sight height of 2.5 (thats about what my sub2k is) i came up with 3" over at 50yds with a 17yd zero.

I had to increase the velocity to between 1800fps and 2000fps to get a 5 inch variation and I'm pretty sure I'm not getting a 500fps or more then the advertised velocity.

 

[CarJunkieLS1]

In 9mm from a 4 or 5 inch barrel to a 16 inch barrel your velocity doesn't increase at all. Use the same velocity as advertised and see what that does in your calculator.

For my Canik 5" barrel and my Ruger 9mm PCC 16" barrel the only ammo that gained any velocity in the longer barrel was 147gr +p best memory says it was like 30fps or so. Anything else I used didn't gain enough to be outside the ES or SD of the shorter pistol barrel.

 

[jmorris]

If the expected outcome doesn't match what you're seeing in real life then your data input isn't accurate.

Or you are outside the range in which the calculation is reasonably accurate.

You could also have a “tolerance stack” where all of your data is “close” but wrong in all the wrong directions, making the “perfect storm“ for a wrong answer.

 

[ECVMatt]

I'm sure this has been posted before but some loads do experience significant velocity gains.

Lucky Gunner 9mm Carbine Test

It could be a combination of things.

I had to play with my Ruger's zero to get it where I wanted it.

I found that shooting at 50 yards for zero gave me a trajectory closer to the calculated trajectory.

 

[twofewscrews]

In 9mm from a 4 or 5 inch barrel to a 16 inch barrel your velocity doesn't increase at all. Use the same velocity as advertised and see what that does in your calculator.

For my Canik 5" barrel and my Ruger 9mm PCC 16" barrel the only ammo that gained any velocity in the longer barrel was 147gr +p best memory says it was like 30fps or so. Anything else I used didn't gain enough to be outside the ES or SD of the shorter pistol barrel.

When using the advertised velocity, 1145fps, according to the calculators I use I should be 1 to 2 inches high at 50 yards.

Every calculator I've used/have access to give me roughly the same data. The only way I can get the ballistic calculator to match the real world is increasing the FPS by 500 or more.

 

[Random 8]

Ballistic calculators only calculate the forward, lateral (wind) and gravity vector components of the trajectory. They do not count for lateral or vertical vectors imparted to the bullet as it accelerates down the bore. IF there was a good way to calculate these, they could compensate. These tend to be amplified with lower velocities as the dwell time in the barrel is longer. Revolver shooters have been aware of the phenomenon since before computers were a thing. LR rifle hunters tend to deny the very existence of this phenomenon favoring blind faith in computer models to engage vicious elk and mule deer at too great of distances. The PRC, F class and High power crowd generally have some real world experience with these outliers and have learned to compensate in their come-ups and sometimes windage.

This is why some rifles, generally light Sporters in medium calibers, seem to shoot inexplicably flat to a certain range until gravity acceleration overcomes the vertical acceleration imparted in the barrel and things start lining up better with mathematical predictions.

The best answer in all cases is to determine your actual trajectory at range and interpolate with the predicted data to figure out where to set your sights.

Warning: this comment will create a distracting discussion that will drift off topic.

 

[twofewscrews]

Or you are outside the range in which the calculation is reasonably accurate.

You could also have a “tolerance stack” where all of your data is “close” but wrong in all the wrong directions, making the “perfect storm“ for a wrong answer.

Either of those possibilities seem reasonable.

I don't have access to a chronograph so I can't verify velocity. I can remeasure height over bore but at most I'm off by 1/4 of an inch. My caliper would give me a more accurate measurement but at less then 50 yards I don't think a quarter inch would make that much of a difference, but I could for sure be wrong about that. I don't think I have the ability to properly verify all the data I'm using which really stinks.

I suppose I could be outside of the range in which the calculation is reasonably accurate, but that just leaves me wondering why its accurate for .308/.357/.22 but not for 9mm.

 

[jmorris]

My caliper would give me a more accurate measurement but at less then 50 yards I don't think a quarter inch would make that much of a difference,

To know that, we would need to know the calculation. Multiplication of error is one way to get off track quickly.

 

[CarJunkieLS1]

When using the advertised velocity, 1145fps, according to the calculators I use I should be 1 to 2 inches high at 50 yards.

Every calculator I've used/have access to give me roughly the same data. The only way I can get the ballistic calculator to match the real world is increasing the FPS by 500 or more.

I see what you're saying, but you said that according to the net the 16" barrel will gain 200fps over a pistol barrel...thats just not true. I really have no idea why the calculator is so off from what you're seeing, but set your optic to the furthest distance you'll shoot and then shoot at closer range and go from there.

 

[jmorris]

The yellow inner is 3 inches in diameter. If your inclined to run check my math the line under distance to the bottom line under notes is 1 inch.

Looks like most of your hits are inside of 3” so I would see that as your resolution, how large were the 17yard groups? A 17 yard zero with a 1.4” group leaves a lot of room for error to creep in. IE a 17 yard zero shot 3/4” high, isn’t a 17 yard zero.

If you want to spend time playing with your firearm, could you set several targets out all level and track the same bullet the whole way vs getting lost in disparity?

Kind of like this but with paper targets instead of balloons.

Remote trigger

www.youtube.com

That would remove the largest variable I am seeing. As each individual shot would then be represented at both ranges.

That rest helps a lot too, as far as putting them into the same spot.

One shot zero

www.youtube.com

 

[jmr40]

I only read the OP and none of the replies so someone may have mentioned this. The height of the sight above the bore matters. A typical hunting rifle will have a scope, or irons about 1/2" to 1" above the bore. Most handguns 1/2". Most AR's and many other rifles have the sights 2" or more above the bore.

If the calculator you're using is ASSUMING a 9mm handgun with the sights 1/2" above the bore and your PCC has them 2" above the bore that changes all the angles. Most online calculators will let you change that setting.

This is a common issue with AR's. A typical battlefield zero at 25 yards is also zeroed for 300 yards. About 2-3" high at 100 and 5-6" high at 200, before falling back to the 300 yard zero

 

[twofewscrews]

I only read the OP and none of the replies so someone may have mentioned this. The height of the sight above the bore matters.

I'm aware that ballistic calculators usually have the height over bore set at 1.5 inches. My height over bore is 2 inches and I make to use it when making calculations.

Looks like most of your hits are inside of 3” so I would see that as your resolution, how large were the 17yard groups? A 17 yard zero with a 1.4” group leaves a lot of room for error to creep in. IE a 17 yard zero shot 3/4” high, isn’t a 17 yard zero.

The only time I can establish a "true" zero with this rifle is within 10 yards. Past 10 yards the group opens up no matter what position, benched or supported, bagged or bipod, to at least 1 to 2 inches. For example, the first shot will be zero, second shot high right, third shot low but centered, fourth shot high right, fifth shot low but centered. Because of this I shoot 10 shot groups, between 10 and 25 yards, and so long as the spread stays within a 2 inch group I call it zero. From 25 to 50 yards a 3 inch spread is normal. At 100 yards the spead was roughly 4 to 6 inches. Its a takedown model so I assume this shot to shot variation is a product of the barrel not actually being secured to the reciever. All my other rifles do not suffer from this issue and zero is actually zero.

If you want to spend time playing with your firearm, could you set several targets out all level and track the same bullet the whole way vs getting lost in disparity?

I went back to the range today and established a 25 yard zero. At 5 yards POI was roughly 1 1/2 low and at 10 yards POI roughly 1 low. At 17 yards POI was roughly 3/4 inches low. Then I brought it out to 50 yards and my POI was 2-3 inches high. The trajectory roughly matched up to what the ballistic calculator said it would be.

I then went back and zeroed it at 17 yards, moved out to 25 yards and 50 yards. At 25 yards POI was 2 inches high and at 50 yards POI was 5 inches high. 5, 10, and 17 yards POI roughly mirriored that of a 25 yard zero.

Using a 17 yard zero at 50 yards, the POI was still 5 inches high.

 

[Litetrigger]

Individul ballistic reality seldom match the numbers

 

[horsey300]

I've got a Ruger PCC (9mm) zeroed for 17 yards (50'6" exactly according to the range) that shoots 5 inches high at 50 yards, but according to the ballistic calculators I use, ShootersCalculator.com or GunData.org, a 17 yard zero should have me shooting 2 to 2.3 inchs high at 50 yards. A 50 yard zero makes the hold under more extreme then I'm comfortable with and then it should be and simply adds to my confusion. I know that ballistic calculators are a rough mathematical estimate of what should happen, so I'm not expecting it to be 100% right, but when I run other firearms/calibers though them I get number that match up with real life enough to be useful. When I run numbers for my .357 lever gun, .308 and .22lr rifles they match up to within an inch or so.

According to all the ballistic calculators and other peoples experiences I've found online, a 25 yard zero (or 17 yard zero) should have me shooting either dead on or maybe an inch or two high at 50 yards.

I know my hold under/over out to 50 yards, and I understand its a PCC so a 3 inch spread at 50 yards is acceptable.
This isn't an issue of me not being able to hit where I want per se, but it's something that keeps me up at night wondering is it me, the rifle, the ballistic calculator or what?

Here are my numbers
Ammo: CCI Blazer 9mm 115g BC of .147 traveling at an advertised 1145fps. I don't have a chronograph but according to the net I'll gain about 200fps, so lets says its traveling at roughly 1345fps.
Height over bore: 2 inches
Ruger PCC: 16.12 inch barrel with a 1:10 RH twist
Optic: This shouldn't matter but I'm using the PA SLX 1x Microprism

These are my targets from my last trip to the range. My 17 Yard (50 1/2 foot) zero might be a bit off, but I've had this same issue when perfectly zeroed at this distance and 25 yards. I zero at either of these two distances and am still twice as high as I should be according to the ballistic calculator I use. Even if my zero is a bit off these images accurately represent where a 17 yard zero shoots at 50 yards.

The middle is switching from Winchester to CCI and firing from a supported position. 10 shots on each stickie. The top right is confirming zero firing from a supported position. As the barrel heats up the spread tends to shift right. The other three are firing unsupported, 2 shots each, moving from target to target in no particular order.
View attachment 1191469
This is 50 yards. My hold is at the bottom of the blue (5 ring) where it meets black (4 ring). From the bottom of the blue to the yellow is three inches. The yellow inner is 3 inches in diameter. If your inclined to run check my math the line under distance to the bottom line under notes is 1 inch. That is 50 shots with 5 "flyers"
View attachment 1191468

Am I using crappy ballistic calculators? If so, what do you recommend I use?
Should I double check the distance's of both targets at the range? I don't have a laser but I do have a tape measure.
Is this a function of it being a takedown? ie because its a takedown the barrel is flopping about throwing rounds high . . . or something of this nature.
Is there something I am missing all together?

Thanks for your help in advance.
Please feel free to call me an idiot . . . but also please explain why I'm an idiot

My just a real quick throw at strelok pro says 3" high at 15 yds, not sure your atmospheric conditions etc, but with 4moa ammo/scope/shooter, this COULD be 5" high to 1" high.

 

[PO2Hammer]

I zero my Ruger PCC with a Romeo5 at 50 yards (125 gr, .125 bc, 1100 fps, 1.4” sh) and my shooter’s calculator gives me a 18 yard first zero, 1” high at 35, 50 yard zero, then 7 inches low at 100 yards, exactly what I’m seeing at the range.
Shooterscalculator.com
I think your velocity and sight height numbers must be a bit off, and the short range zero is magnifying the errors.

 

[jmorris]

Looks like he figured it out in #18.

I went back to the range today and established a 25 yard zero. At 5 yards POI was roughly 1 1/2 low and at 10 yards POI roughly 1 low. At 17 yards POI was roughly 3/4 inches low. Then I brought it out to 50 yards and my POI was 2-3 inches high. The trajectory roughly matched up to what the ballistic calculator said it would be.

 

[Walkalong]

If the expected outcome doesn't match what you're seeing in real life then your data input isn't accurate.

This all day long.

 

[twofewscrews]

I zero my Ruger PCC with a Romeo5 at 50 yards (125 gr, .125 bc, 1100 fps, 1.4” sh) and my shooter’s calculator gives me a 18 yard first zero, 1” high at 35, 50 yard zero, then 7 inches low at 100 yards, exactly what I’m seeing at the range.

I get basically the same trajectory when I use your numbers: 50 yard zero is high at 18 by .03" and dead on at 50. My sight height is different then your by .6", I'm using 115g and your using 125g, my BC very well could be wrong, so while our trajectories should be and are close they are not identical.

I think your velocity and sight height numbers must be a bit off, and the short range zero is magnifying the errors.

Losing FPS bring the arc lower which is clearly not happening. You have to increase fps by 500 to match the trajectory I'm seeing and all I've ever used is factory ammo and never +P. I use the advertised box speed for the calculations and the internet advise that you gain 200fps, I end up with half an inch difference in the arc on paper.

Even if my sight height is off by half an inch, up or down, that doesn't make enough of a difference. A 17 yard zero should be about 2 inches at 50, not 5 inches.

I've used two other scopes on this rifle but except for getting on paper I never even considered checked trajectory within 25 yards.
I'd say I should check the optic but If its accurate elsewhere then I should be looking at the gun . . . but its as it should be in every other respect . . . thankfully its not my "battle rifle" or anything, just a range toy.

 

[twofewscrews]

Looks like he figured it out in #18.

Dammit. I wasn't clear. A 17 yard zero was still throwing them 5 inches high. Gotta edit that now