I enjoy lurking in the sections about firearms, ammo and optics but most always the details are way over my head and its not needed info for the way I "hunt"(no target guy.) I still like to learn and try to slowly pick up things that may help me. This type of thread does that for me. It will slide off topic enough that I can gleam something out of it.
Anyway, my point is there are ALWAYS differences of opinion even among guys that I know are "experts" in their own right. I just have to hold my breath and hope the discussions stay civil, since they often dont. There are too many knowledgeable guys on this thread to single them out but I just picked up on Alpine Hunter being new on here and Im very impressed by what appears to be some good experience and knowledge. Like others, he may not always be right but he can bring a lot to the table. Hopefully civil discussions will keep him interested and taking time to post. I just watched Oppenheimer and there were lots of smart guys on that project and they didnt always agree but their collective efforts got it done. Looking forward to ongoing insights from all our regular tried and tested posters as well as the new guy.

You bring up great points about keep this civil and helping expand the knowledge pool. I'll be the first to eat crow if I'm wrong, just ask my wife. She wears the pants and I've never tried to take them away from her. I'm been working with ballistics and long range shooting for over thirty plus years. I know a lot, but I don't know everything. I've had great conversations with Brad and Bryan over the years when I got stuck on something or didn't grasp what they were telling me. I've got thick skin and never take this stuff personally. What I ask, if you say I'm wrong, which I could be. Just don't tell me I'm wrong, explain your point and use facts. That's all I've tried to do.

My buddy and I purchased a Garmin Xero doppler radar chronograph. I have a new Leupold VX5 3-18 X 44mm HD scope that sits on top of my custom 6.5 CM. After a south Texas hunt in the canyons of the hill country last fall, my aging eyes need more than 10X. 10X is the max I've ever shot until now. In May were headed to the Joshua ranch as we've secured the 1000 yard range for half a day. We want to see what are actual shooting dope is out to a grand. Once I have it I'll have a custom CDS turret made from Leupold to match. I'll also tweak my ballistic program to match. Always better being thorough I say.

Yep keep it professional and as factual as you can. Goes a long way!

Here in lies the next issue. How accurate is your chronograph. We’ve stacked three different chronographs back-to-back and tested loads. Guess what, the velocities were all different. Yes, all the chronographs were stacked back-to-back at 18" or so, but the spreads were much greater to say it was 18". We had spreads greater than 50 fps. My buddy and I just purchased a Garmin Xero C1 Pro. We haven’t gotten a chance to test it our yet, but look forward to trying it out.

Once you're finished, I would be very interested to hear your comments on which chronographs do the best job of capturing the true velocity of a bullet and why. It's the differences in the technology that interests me most, from measuring the length of time that it takes a bullet to pass by two light sensors, to those that supposedly use the Doppler effect.

JG your focus is narrowly focused on the 6.5 CM. I get it you like the caliber. Your claim that the published velocities is are a flat out lie is way incorrect. Manufactures are all held to some type of ISO standards. Manufactures aren't given leeway to lie and make up stuff. If they are caught in an ISO audit not following their ISO standards or lying about results, this leads to major fines and legal issues. These velocities are totally correct when it comes to their test barrels.

There are a lot of physics in play here, small changes cause different muzzle velocities. It's not black and white. Most of the state of the art barrel makers will build barrels to a given inside bore diameter per the customers request. They will cut your rifling in different configurations as well as the number of lands and grooves. Heck they can take your specified twist rate out to the 10 thousands of on inch if that's what the customer requests. Competitive bench rest shooters have been playing the inside bore diameter, rifling type and and twist rates for decades, looking for that small edge to tighten there groups.

When it comes to ballistics parts of your answer, well some just aren't accurate. I get it you have a nice long range to play with and test at. The G1 drag model was originally developed for a one inch round nose projectile. Modern bullets don't resemble a one inch round nose projectile. The G1 was adapted for modern rifles bullets many decades ago. In order for it to work the ballistic modeling and calculations have to be changed as the bullets velocity decreases over distance. This is done by changing the G1 BC as the velocity decreases. These decreases in velocity were often assumed based on the muzzle velocity. I don't reload, so I don't look on bullet boxes, but it makes sense to publish which ever drag model and BC that matches the given bullets. Most ammo manufactures still publish the G1 drag model BC. They should really publish the correct drag model and BC.

Like most things these days, computers and really smart engineers develop better ways of calculating things. The G5/6 & 7 drag models were developed for modern bullets. The bullet BC and ballistic modeling for these drag models remain the constant throughout the decreases in muzzle velocities over distance. The calculations and ballistic modeling are pretty rock solid. Bryan Litz is a flat out ballistics genius as is Brad Mallard who created the JBM ballistic program. These guys have done a ton of R&D and have two of the best ballistic programs available.

As for scope height you are incorrect. Take any ballistic program change the scope height and track your intermediate and max ranges. They will change, especially if a shooter is shooting an AR type platform with two plus inches of scope heights. The further out you go, the more your intermediate and max distance will change.

As for scope tracking and massaging my ballistic program. My Leupold VX5 tracks fairly well. I'm an engineer in real life, I like to play with numbers and calculations. If I can take data and massage it to fit my shooting, nothing wrong with that. I left tracking out of my original post, but that really plays into the equation as well. We used to have a cinder block on top of concrete shooting bench to test a scopes ability to track properly. We had two sets of epoxied dual V-Mount blocks on it. One for 1" scopes and one for 30mm. Sorry this was before the 34mm and greater scope tube sizes. We'd place a scope in the V blocks, take two .5" wide elastic band and tighten it over the scope locking it in place. The setup was rock solid. The height of the cinderblock and V blocks we're designed so they would center the scope reticle on our 100 yard target or be close enough to center of target. We'd note where the reticle center was located on the target and do three box tests. We tested 10, 15 & 20 moa box test tracking. Much more accurate than shooting a box test. You would be surprised at the tracking of some scopes. Some aren't as precise as one would think and can very slightly from one scope to another of the same make and model. Though close enough for 98% of shooters. We were also able to track reticle cant as we moved up/down right left. Cant is a huge issue for shooting long ranges. Leupold pissed off the long range and tactical community when shooters found out there scope cant could be up to three degrees and stay within warranty. That was totally unacceptable for long range and tactical shooting. Each degree of cant at 1000 yards is approximately six inches. So three degrees could be 18". Not good. Think of it this way, you're dead on at 100 yards, as you dial up the cross hairs begin to cant right or left, usually right from what we tested. At a thousand yards your reticle has canted three degree and your POI is 18" right or left. You can say that's lost in the wind or spin drift, but it's a real! Oh yeah, spin drift can be up to 6" or more at a 1000 yards depending what you're shooting. Tactical and long range shooters started leaving Leupold in droves. This opened the door in the early 2000's for other scope manufactures to take that market share and boy did they. Lots of great scopes out there for long range shooting, Now some cant is shooter error on how level there reticle is when shooting. Hence the need for scope levels when shooting really long ranges.

When you say your chronograph is very accurate, I won't disagree or argue. Most are a lot better than they used to be. However, how do you know how accurate it really is? What is the is the internal clock/synchronization sampling rate between screens? My bet if you put two back to back, you would see small differences. We have two CED M2 Millennium Chronographs and we see small differences between the two of them when set back to back. Infrared screens help a lot to decrease those small difference. This is why I'm really looking forward to trying out our new Gamin Xero doppler radar chronograph in the next couple of weeks.

I'm not hear to argue with anyone, just add my thoughts to the shooting community. I don't have all the answers, however I understand ballistics very well. It's a passion of mine as I love to reverse engineer new ballistic programs to see what ballistic modeling and calculations the creator used.

Hope it helps!

The best chronograph money can buy is the Oehler chronograph. This is the Chrono all others are compared to. It's a lab grade chrono used by most bullet manufactures and test facilities.

I noticed Oehler's newest System 89 includes both hardware and software for calculating a BC value in addition to measuring velocity. That brings into question again the hunter wanting to provide data to Leupold for a CDS turret, needing to rely on a BC value provided by the manufacturer of the load they intend to use. As the case with MV, I take it providing Leupold with a more accurate BC value would allow them to calculate a more accurate bullet trajectory and turret markings.

Not being someone who reloads or wanting to invest $3k in a Oehler System 89, I'll remain content with providing Leupold with the BC value shown on the ammo box. Besides, even with my new CDS turret combined with my limited shooting capabilities, I'm not expecting to take shots at a target 600 yards away. But it does make for good discussion both here and elsewhere.

As I said, Oehler makes lab grade Chrono's. For your CDS turret, if you can get access/rent an chrono you could get much more accurate data for your Leupold to work with. Can you send me a private message please, I'd like to help you out.

[quote=Alpine Hunter][quote=J.G.]Shooting short action cartridges to 1400 yards, and I've got ranges available on friend's ranches that can afford me more than one mile shooting. When 1000 yards gets easy, I decided to go 2000 yards. 1.25 Mile is my current farthest hits. 2180 yards.

In a 6.5 Creedmoor it won't be 20 to 25 across the board per inch of barrel. It may start out around 20fps per inch but will steadily increase. In the shorter lengths it will be closer to 50 per inch.
I've done this on 30-06, 270, and 243 barrels.

I’m thinking few people buying an Oheler 89 are shooting factory ammo.

yelp they will absolutely spend $3k on a chrono to build a CDS turret in a budget luppy, with a budget gun price point, with cheap budget adjustable rings with OTC ammo. Only the best will do.

Tikka 6.5CM's, Lapua Scenar 139gr, and RL26 is the easy, easy, easy button combo.

I would have actually thought they would purchase the Lab Corp or Garmin doppler radar systems at a fraction of the price of the Oheler, but you could be right. I have a custom 6.5 Creedmoor built by Chad Dixon at Long Rifles Inc. I shoot Hornaday 143 gr ELD-X factory ammo. I can usually shoot in the .4's, with great conditions I've been in the mid .3's. If flat out shoots! I just added the Leupold HD VX-6 3-18X44mm with Area 419 scope mounts. My aging eyes just weren't digging the 2-10 I had on it last fall hunting in the canyons of the hill country. I'll be adding a custom CDS turrets after we do some testing in early May at a 1000 yard range with our new Garmin Xero C1 Pro.

The only thing not easy about that is finding RL26

Alpine its hard to punctuate sarcasm in written word, but any one verifying their loads would use the Lab Radar or Garmin for a fraction of the price.

Alpine its hard to punctuate sarcasm in written word, but any one verifying their loads would use the Lab Radar or Garmin for a fraction of the price.