Looking for Help - Barrel Harmonics Question

[Paul Milone]

Im looking for any help with this issue / question. I recently had a build completed by a quality gunsmith / national shooter. Rem 700 action, 26" Stainless Proof Research barrel, 6.5 creedmore, Razor HD Gen II 4.5-27x56, LaRue Tactical OBR mount/rings, 20 MOA base, Hornady 140gr ELD-M rounds.

Shooting sub 1" at 100. Ballistics calculator(s) all say I should be 2.6 mills at 500. I was not on steel until I went up to 4.1 mills A full 1.5 mills more. Then I shot a hurried 5" 5 shot group at 500yds.

Wondering what was going on. What did I do wrong. Re calculated the ballistics program(s), re sighted in.... no change.

Shot 10 rounds thru decent chronograph. Averaging 2797 fps.

Took scope off, replaced it with a Nightforce. Got the same results, shooting low, but shooting tight.
I spoke with the folks at Proof Research. I spoke with the gunsmith, I spoke with great shooters. All say dont worry about it, just increase your dope and continue to shoot groups at distance.....

Some other folks say "it's a lemon".

Has anyone else had a barrel that "shoots low" ?

 

[CharlieNC]

2.6 mil is right for 500yd and its difficult to imagine the velocity could be so slow to require 1.5 more, but have you run it on a chrono? Have you confirmed actual 500 vs further? The harmonics don't know if the bullet is going to 50ft or 500yd, so the launching position should not be a factor. Something is way off and I would not simply accept such a major discrepancy doesn't matter. Probably something simple though.

 

[mikegaiz]

Can't help with harmonics, however I have found that 100 yard load testing for long range purposes does not work for me. Once I went to 300 for testing I found best loads loads worked at 1000 yds. Retest at 300 would be my advice.

 

[ebb]

When you do a OCW test and find a sweet spot where it is grouping good, the bullet is exiting the barrel when the harmonics have the barrel at the top of its vibration cycle or at the bottom. If it is at the bottom this may cause the low situation. Also has the barrel been clocked? Many smiths have agreed that the bore on most all barrels is like a spiral if when this barrel was head spaced and screwed into the action the crown was at the bottom of this spiral then that could cause it to shoot low. It really doesn't matter what the numbers tell you, it how small the group is when it gets there!

 

[Jarhead6870]

Normally I would have asked if you did a tracking test on the scope but if you changed scopes and got the same results, then tracking should be okay. You might double check your torque values on your action/guard screws as well as your scope base, cross bolts and cap screws.

 

[SheepDog]

If I understand you - you are getting good sized groups but the group is lower than the software predicts - is that right?
If so then there are problems with your software and not your gun. Does the software allow you to enter sight to bore centerline distance? Have you actually measured that distance at the muzzle? Are you able to put in the environmental variables? Are you using the ballistic coefficient that the bullet is rated with and choose the corresponding "G" table? (using G7 numbers in a program that assumes G1 will give more drop)

 

[Cool Tool]

When you do a OCW test and find a sweet spot where it is grouping good, the bullet is exiting the barrel when the harmonics have the barrel at the top of its vibration cycle or at the bottom. If it is at the bottom this may cause the low situation. Also has the barrel been clocked? Many smiths have agreed that the bore on most all barrels is like a spiral if when this barrel was head spaced and screwed into the action the crown was at the bottom of this spiral then that could cause it to shoot low. It really doesn't matter what the numbers tell you, it how small the group is when it gets there!

I don't by that theory for one minute.

 

[Sniper338]

This is the second post... same OP, same copy paste question, just different title...

 

[ebb]

Wasn't asking you to.

 

[Paul Milone]

2.6 mil is right for 500yd and its difficult to imagine the velocity could be so slow to require 1.5 more, but have you run it on a chrono? Have you confirmed actual 500 vs further? The harmonics don't know if the bullet is going to 50ft or 500yd, so the launching position should not be a factor. Something is way off and I would not simply accept such a major discrepancy doesn't matter. Probably something simple though.

I did run it thru a chrono 10 rounds average was 2797 with a standard deviation of 15 I also was able to get hits at 600 with 5.1 mills (should be 3.5)

 

[Paul Milone]

If I understand you - you are getting good sized groups but the group is lower than the software predicts - is that right?
If so then there are problems with your software and not your gun. Does the software allow you to enter sight to bore centerline distance? Have you actually measured that distance at the muzzle? Are you able to put in the environmental variables? Are you using the ballistic coefficient that the bullet is rated with and choose the corresponding "G" table? (using G7 numbers in a program that assumes G1 will give more drop)

Yes Yes and Yes. Im using Shooter as well as Strelok. Both say the same thing. 2.6 mills Scope height is 2.5" (measured) which is what I put in the calculator. I used the BC that Hornady gave me. Ive used both G1 & G7 I am able to enter environment in my calculator(s) I have entered and re entered all the data dozens of times. It simply does not make sense. But I am grouping. That is why some say, who cares, keep shooting groups and dont worry about what it should do, but rather worry about what it is doing.

 

[Steelnecktie]

It doesn't matter if barrel is clocked at 12 or 6, when your sighted in at 100yds. the bullet can not drop faster because it was clocked at 6. Your scope turrets or something else is messed up. Do you have MIL turrets on a MOA scope? I'm sure it is something simple you will figure out.

 

[rduckwor]

My guess is that your measured velocity is not correct. Try a different chrono. They are not exactly reliable machines unless proven to be so.

Good Luck,

RMD

 

[CharlieNC]

Your velocity and calculated results are completely typical. There is not enough fine tuning for bc, velocity, weather, etc to give 1.5 mil error at 500yd. Now it is interesting that the same fixed 1.5 error is present at 600yd. This is beginning to sound like you are not actually zeroed at 100yd. I don't know the details of your scopes, specifically how the zero stops are set. This is an aspect you may want to investigate and confirm. And you can confirm shooting 100yd zero, then shoot 500yd with just a reticle holdover to explore proper turret operation.

 

[Paul Milone]

Your velocity and calculated results are completely typical. There is not enough fine tuning for bc, velocity, weather, etc to give 1.5 mil error at 500yd. Now it is interesting that the same fixed 1.5 error is present at 600yd. This is beginning to sound like you are not actually zeroed at 100yd. I don't know the details of your scopes, specifically how the zero stops are set. This is an aspect you may want to investigate and confirm. And you can confirm shooting 100yd zero, then shoot 500yd with just a reticle holdover to explore proper turret operation.

I have a 100 zero. sub 1" groups. I did confirm with the reticle at 500 and it was the same 4.2 mills The scope is tracking fine as best I can tell. The hits at 500 were the same if I dialed it as I did by holding in the reticle. It's a horace type reticle on the Vortex Razor HD Gen II

 

[CharlieNC]

I'm out of ideas. All my rifles from 223 to 300WM shoot 2.5mils +/-0.1 at 500yd. The fixed 1.5mil error is the major clue, but what?

 

[MislMan]

Since this is a consistent issue and two different scopes have been used I would figure you might look into other factors such as ammo/bullet concerns. It sounds like you are using factory box Hornady ammo. Maybe they got the wrong ammo in the box. Maybe 143 Ammo in a 140 box or maybe ELD-X in a ELD-M box. Can we assume these results were all on the same day/same conditions? If so maybe some weird wind condition?

 

[MislMan]

Any chance this could be a shooting position thing? Something like eyesight issues causing you to not have crosshairs centered on target. Let someone else shoot the gun and rule this out. Could be shooting where you are aiming.

 

[gat]

Two thoughts 1) No confusion between Mils and MOA?? 2) Parallax problem??

 

[mikegaiz]

Did you take the height of your bases/rings into the calculations?