Velocity issue...

[trentcwwilson]

With a 60,000+ psi load, I promise there are harmonic deflections at play. Varmint Al had some very good visualizations on his site.

Um....I'm NOWHERE near 60k. Hodgdon list 48,600 at a max of 45 grains. I'm shooting 44.7.

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[Deadshot2]

With a 60,000+ psi load, I promise there are harmonic deflections at play. Varmint Al had some very good visualizations on his site.

Um....I'm NOWHERE near 60k. Hodgdon list 48,600 at a max of 45 grains. I'm shooting 44.7.

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Regardless, there are harmonics at play. Even with a "20mm barrel blank" there is still flex. It only takes .040" of "movement" at the muzzle to give you 4" of movement at 100 yards. Only .038 MOA of angle change at the muzzle if you want angular measurement. Want to see how flexible your barrel really is? When the action is out of the stock place each end in a v-block on a solid surface (like concrete).

Put a dial indicator under the center of the barrel and lay a 20# bag of shot on it. Read the change on your dial indicator. Be prepared to be surprised at how much change there is. It's just metal's nature and as long as the modulus of elasticity is not exceeded, it just springs back. Heck, even concrete flexes. I've had the misfortune of having to change a flat tire on a bridge and there's enough flex to make some people get "sea-sick".


What's hard to visualize is how small changes yield such large results.

Want to be totally confused? A rifle with a brake behaves totally different than one without. Just the difference in recoil can shift POI an amazing amount due to how the shooter's body behaves during those critical Milliseconds between ignition and the bullet leaving the barrel.

I don't think there is a thing wrong with your barrel, rifle, brake, load, or even your shooting technique. You are just seeing a natural phenomena that can be dealt with by simply changing the Zero with the brake attached and enjoy your shooting.

FWIW, I shoot twice a week and frequently sit next to a friend who's constantly putting on and taking off his muzzle brake. Don't know exactly why but he experiences the same thing with POI shift. Nothing wrong with his rifle as he's regularly in the top three at local competitions with more than just a few wins.

[trentcwwilson]

Regardless, there are harmonics at play. Even with a "20mm barrel blank" there is still flex. It only takes .040" of "movement" at the muzzle to give you 4" of movement at 100 yards. Only .038 MOA of angle change at the muzzle if you want angular measurement. Want to see how flexible your barrel really is? When the action is out of the stock place each end in a v-block on a solid surface (like concrete).

Put a dial indicator under the center of the barrel and lay a 20# bag of shot on it. Read the change on your dial indicator. Be prepared to be surprised at how much change there is. It's just metal's nature and as long as the modulus of elasticity is not exceeded, it just springs back. Heck, even concrete flexes. I've had the misfortune of having to change a flat tire on a bridge and there's enough flex to make some people get "sea-sick".


What's hard to visualize is how small changes yield such large results.

Want to be totally confused? A rifle with a brake behaves totally different than one without. Just the difference in recoil can shift POI an amazing amount due to how the shooter's body behaves during those critical Milliseconds between ignition and the bullet leaving the barrel.

I don't think there is a thing wrong with your barrel, rifle, brake, load, or even your shooting technique. You are just seeing a natural phenomena that can be dealt with by simply changing the Zero with the brake attached and enjoy your shooting.

FWIW, I shoot twice a week and frequently sit next to a friend who's constantly putting on and taking off his muzzle brake. Don't know exactly why but he experiences the same thing with POI shift. Nothing wrong with his rifle as he's regularly in the top three at local competitions with more than just a few wins.

Again, I've rezeroed the scope and is shooting better than ever at 100 yards. Now, explain to me how barrel harmonics have changed my ballistic charts for extended ranges and it not be a velocity issue.

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[taylorce1]

I'm not new to the game of long range shooting. At 100 yards, barrel harmonics wouldn't change my POI 4" unless the front action screw was majority loose. It's not, torqued down to spec. As far as a chrony, I'll only buy quality equipment, and that means the MagnetoSpeed V3. I've tried the standard models and they have issues I don't have time to deal with.

Adding a brake changes the way hot gasses exit your barrel, and you don't think it affects barrel harmonics? I don't care if you have a .800 thick barrel, anything applying pressures in the tens of thousands of pounds per square inch is going to cause the barrel to move. So yes your POI can change by 4".

It's amazing how any of us ever functioned before the Magneto Speed or Lab Radar, and still managed to hit anything we were shooting at. Great tools both of them, but recording data is essential in long range shooting, so even a cheap chronograph can supply you with good info. Even if it gives you errors on occasion if your record enough shots over it, you can get a pretty exact speed of your bullets to plug into a ballistics program.

Continuing on my previous post, I did rezero my scope. At 200 and 300 yards, my ballistic charts are STILL not correct. I'm not getting 1.70 MOA adjustment @ 200 and 4.28 MOA @ 300.

So you have info at 200 and 300 yards to plug into a ballistics program, unless you didn't bother to record the changes. So what was your new drops to get on target at those ranges? Just change the speed in the ballistics program until your drops match what your getting on target. Again you don't have an issue or "BIG" problem, other than the fact you're looking for one.

Um....I'm NOWHERE near 60k. Hodgdon list 48,600 at a max of 45 grains. I'm shooting 44.7.

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Actually Hodgdon lists your load at 48,600 CUP, which very well could be close to 60,000 PSI. They are not the same measurement: http://bulletin.accurateshooter.com/...-measurements/

[Deadshot2]

It's amazing how any of us ever functioned before the Magneto Speed or Lab Radar, and still managed to hit anything we were shooting at. Great tools both of them, but recording data is essential in long range shooting, so even a cheap chronograph can supply you with good info.

I started shooting when I was 7 and shot for 56 years before I bought my first Chronograph. All through those years it was simply a matter of recording drop at known distances in order to build my own ballistics tables. Not only no Chrongraph but no computer or smart phone "apps". Just pencil, paper, and a ruler.

Eventually factories started printing "drops" on the box for hunters but most hunters just used those for starting points when making a distance change during the pre-season target shooting.

Then there those "LR Shooters" that do it for a living. Military Snipers don't spend a lot of time with chronographs, just their log book which records pretty much every shot and the changes made for distance, wind, temp, altitude, etc.

I've found that even if you do have accurate speed, and a good ballistic's app (along with an accurate calculated range if not shooting KD), all it usually does is let you get "on paper".

[darkker]

Um....I'm NOWHERE near 60k. Hodgdon list 48,600 at a max of 45 grains. I'm shooting 44.7.

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I said 60,000+ PSI, Hodgdon doesn't list PSI data, they list CUP; those are not the same units and can't be interchanged.

Remember that lots of powder can vary in burning rate, quite widely, so the specific grain charge isn't important alone; you need to know the velocity per charge weight. That way you can compare to the pressure tested data, to get an idea of where you are pressure wise. Assuming that your lot and the lot Hodgy tested(which they don't list, btw) are the same is not a safe bet.
Hodgy posting CUP data has been one of my complaints for some time now. Quite some time ago now, SAAMI sent out some reference powder lots to the majors(Federal, Rem, etc) for pressure results. Once you exceed @ 45,000 PSI, Calibrated Copper Crushers report pressure swings on the order of 20,000psi. This is why the industry moved to PSI rather than CUP, because of the discrepancy in reported pressures.