Home Forums Hunting & Shooting Long Range Hunting Trajectory Validation / Velocity / BC

So do you guys check your trajectory and compare it to a ballistic program to validate velocity and BC to tweak your drop charts?

My range goes out to 550 yards, My rifle is zeroed at 100.

What would be a good max range and mid range to check drop? Not sure about being able to shoot a good group at 550 despite hitting steel at that range.

Can I just plug in the drop at those 2 ranges into the app for an automatic adjustment for all the drops? So what gets adjusted, the BC, velocity?

Can someone splain this all to me?

What ballistic app are you using?

Jordan, I meant to include that. I am using Strelok+, which does have a trajectory validation feature.

Edit: would one range be enough?

I think you’ll have to start with an assumed BC and juggle velocity or an assumed velocity and vary the BC.

You can use the trajectory calibration feature of the app, or you can calibrate it manually. If doing so manually, you would modify the quantity you have the least confidence in. So if you're using BC values you belief are reliable, and a chrono that is not so reliable, then you would modify velocities until the trajectory matched your actual results. And vice versa.

If you want to use the trajectory validation feature, the more data points for drops at various distances, the better. But as a minimum, you would need two data points, one being your 100-yard zero and then another drop value at another distance (in your case 550 yards is preferred).

EDIT: To answer your question, I don't have Strelok but it looks like you can select for the app to adjust either BC or velocity in the trajectory validation process. As I mentioned previously, I would select whichever you have the least confidence in.

Gotcha. Thanks

One more thing to be aware of, you should validate your turret adjustment increments before changing muzzle velocity or BC.

Like Jordan says I do a tall turret test to make sure my knobs dial appropriately. Then I would shoot 500 atleast and may atleast check 300 as well. If manually doing it I tend to tweak BC as every rifle is different and bullets can vary box to box. I believe my magnetospeed more then the box label.

The Magnetospeed is a very good chrono, but I forgot to mention that one also needs to consider the measurement sample size when determining how much confidence they have in their average MV value.

Yes, I have done that. Scope is a NF NXS and has proven to have accurate adjustments.

I have a magnetospeed and have questioned my velocity of 2845fps in my 6.5 CM. This is with a 26" barrel, 41.5 grs of H4350 and 139 Scenars. 10 rounds for average velocity.

With 143gr ELD X factory loads, hitting steel at 550 was done with regularity. When I switched to the handload Scenars, I was having a rough time yesterday. This is despite a 3/4 MOA site in at 100 yrs.

I plan on going back with paper, hence the trajectory validation question.

Well I went back to the range this morning and realized that my drop was about 7" more than Strelok showed at 540 yards, 300 and 400 yards were fine.

I dialed up another 1.25 MOA and nailed it. Targets are at 540.

Now I have to figure out if I made an entry error or what else could have been wrong like velocity or BC.

BC changes with velocity. So maybe plug in different bc values over the flight of the bullet?

Comparing the 2 drop charts with a revised velocity of 2772 compared to 2845, the difference gets real noticeable starting around 375 yards. 2772 fps was spit out with the validation adjustment at 540

Since I only shoot out to 540 right now I am going to go with a 2772 MV. It seems reasonable enough for the load.

I am assuming the Scenar BC is pretty accurate? I will try changing the BC, thanks.

Things will be a lot more telling beyond 550. Right now the 1000 yard range is under construction, but I have never shot past 550. Thinking it's a whole new ball game starting at 600.

Thanks for your input. Just trying to learn this stuff

You got your MV from a magnetospeed??


You had to reduce it like 75fps to validate?



Have you tried lowering the BC?? How low do you have to go for your data to validate??


Scope height and all that good stuff is input correctly??


BC from the manufacturer is more of a starting point IMO.



Ballistic calculators and apps are only as good as the information you put in them.

Bryan Litz tested the 139gr Scenars and came up with a .285 G7. If I have a BC Litz provided, I true the muzzle velocity to make it match the trajectory. You might plug in Litz’s G7 and see how it lines up for you.

John

Mauser and Hondo, thanks. After looking at this closer I am a little suspect of Lapua's G1 of 578. Hondo, it looks like I can only change the G1 in Strelok.

I was able to find Litz's G1 at .557 and will plug that in and see if it comes close to matching my drop at 540.

Thank you for all the replies!!

I have learned a lot the past few days and allowed me to expand my shooting skills.

Edit: I know some of Litz's information is subject to copyright laws but some specific numbers are on the interweb

Do you guys have his book?

I don’t use Strelok but would be amazed if it didn’t have a G7 option. Ballistic AE has a library of bullets Litz has tested with their associated G7 BCs. That’s where I get the BCs if available. If using a Litz provided BC, I always true the velocity at the farthest I can shoot on my range (820 for now). That has always worked out pretty well for me.

Litz did several podcast on “The Everday Sniper” podcast, and they were very informative. G7 is the way to go for BCs if you can get it. Velocity banded G1s like Sierra does work well if your software can process that. Single G1s are least preferable because the G1s decrease markedly as velocity decreases.

John

The G1 BC is based on a poor drag model for the shape of the Scenar. Your MS velocities are likely very accurate, so I would use the Litz G7 BC value and tweak as necessary to match your actual drop data. Like John said, I’d be surprised if Strelok didn’t have the capability to use G7 BC values.

I just checked and don't see where I can change from G1 to G7 on Strelok +. I also have Strelok Pro, which does have the capability to use G7. Strelok + satisisfied my needs so I hadn't use the Pro application.

Now that I am in the rabbit hole, I will transfer to Strelok Pro and see what I come up with.

EDIT: using Litz's G7 and my original velocity, I am right about where I should be. 10.6 MOA using my original velocity vs. 11.0 MOA using a 73 fps reduced velocity.

I quit using my multiple chronographs,a coupla years ago. I KNOW with good brass,propellants of repute and a Smooch,that my SD's are amazingly trite. Hint.

I also KNOW,that I test glass mechanics and that the deviations there,will reliably blow minds. My gut hunch is you bought The NightFarce Koolaid and are gunning assumptions. That's correlated in your final thoughts,as you address come-ups that the NightFarce simply can NOT contend(.10 MOA "graduations"). Tall 100yd paper as cited prior by Mallard,is a fhuqking requisite. Hint.

Once you KNOW how your erector behaves(total mechanical swings,along with zoom actuations),then you can correlate WTF is happening downrange,as you steer bullets with same. Read that again. Now one more fhuqking time. Less same,you are pissing up LOTS of ropes. Hint.

"G7's" are a lovely Factoid to cast about,but it don't do fhuqk all for Optic's Integrity. Cut a concise G1 by 50% and you "resolve" it's G7. From there,factor if scope mechanics can account for the "discrepancy". Hint.

Personally,I'm shooting come-ups in good conditions,with distance nearing a platform's Transonic Slip. I simply backtrack from there,as good input in,yields DOPE in accordance to a known erector's abilities. Hint.

In this manner,there is no bogus muzzle velocity to fixate and ONLY mechanical come-ups matter,which is how POA/POI are aligned. There's no "fast" barrel or "slow" barrel fhuqking bullschit,there's simply a known optic,correcting a known bullet,at a known range in a known atmosphere. The hits are real and zero fhuqking else matters. Hint.

From there,repeats are easily ascertained through the erector's threshold and it's easy to establish a baseline of hit connect expectation,as per mechanics. That leaves Atmospherics in it's own World,as it should be and another Thread. Hint.

PROVE the NightFarce. First. Hint.

Thank me later.....................

I do agree. Being new to long range I was looking for short cuts with numbers coming out of a black box and hoping things lined up for hits.

One can purchase "odds" and there are some seriously well known routes,from which to arrange same. That being said,it only takes a few shots to correlate a platform's relative ability. Glass is fhuqking KEY,because despite the bullschit,it ALL revolves around same. There are some "KNOWN" quantities,but they too warrant being proven in context. Hint.

Keeping angular measurement as a fixture,will help most. That ".25 MOA" "click" graduation at 100 yards,soon becomes a "halfa fhuqking foot "click" downrange(perhaps rightfully subtended). Hint.

"Odds" are in this day and age,that implements and ammo are fairly sound,as juxtaposed against Legendary Tales. The weak link being Optics and their schitty "abilities",which are glossed over and "explained". Hint. LAUGHING!

Shots were/are "heralded",with wares that preclude their mechanical ability to even fhuqking arrange same! I'll let The Lore Live. Hint. LAUGHING!

Simply start at the fhuqking start,if only as per always.

Hint....................

I follow your diatribe but you could cut out most of the fhuqking crap and get to the point with much less BS...and your point is most oft quite well taken. You can be very helpful and instructional when you want. Hint.....Thanks!

MsQueen,

I get it that you are a NEEDY Kchunt and a Brokedick to boot. Hint.

I simply Post Facts,that ain't refuted...to The Chagrin Of Crying Clueless Fhuqks EVERYWHERE. Hint.

Laughing!.......................

Glad you got it sorted out.

There are really no short cuts ,get a target a buddy with a 4 wheeler start moving the target farther and farther away and shoot at 50 yard intervals or so. When you are put into a position where you only have one shot and nail it you will not regret doing the homework.

Well yeah, trajectory validation refers to the process of confirming model predictions using actual drop data.

First shot of the morning,required 28 Mils erector correction(530yds),from an 18lb + Vudoo's 50yd zero. Rifle/ammo both at ambient,as it lives in my crummy. I called the wind at half-value,which was a subtle 3 Mil's windage slide and it was money. Hint.

Rifle had never seen a chronograph or a 4-wheeler,though it do wear an erector of repute and the "surprises" were/are nil. DOPE is factored in 10yd increments and simply tracked backwards from mechanical erector travel ceiling,conjoined with it's (10 ) Mil's of reticle,which of course reliably aligns POA/POI from the muzzle to same. Hint.

Flipside and sliding numbers about...with a 139 Skinner and .285 G7 at the de-tuned 2772fps launch speed with a 100yd zero,in the moment's current atmosphere,28 Mil's of elevation would be knocking on the 1750yd line's door,though obviously on the dark side of the Transonic Slip. To catch 6 Mil full value wind correction requisite,one would need to drive the parcel past the 2000yd line. Hint.





Not to diminish the oblivious humor of The Traveling Cardboard Circus Troupe,their "abilities","knowledge" or "results". The modest solution that puzzled the OP,was founded. Enter reticles which align erectors start to finish and at all magnifications and the "AMAZING" and "INCREDIBLE",simply become fhuqking mundane,as all correlates nicely with Base Ten "math". There's no fiddle fhuqking around,to the chagrin of Clueless Drooling Dumbfhuqks the World over. Hint.

Laughing!................

Thanks for posting that and your methodology

Have a new rifle,I may get to tomorrow. No matter who's barrel it is,whether OEM or Custom,they all get cleaned sterile. JB/Kroil for me,but I've used it all. Hint.

KNOWING well in advance,the particulars of the Trifecta which matters most(RPM/COAL Latitude/Throat Geometry),it's easy to pick THE bullet. In this instance,a .284" 180 ELD M and it's .790-ish BC. With Virgin brass and a new Lot of powder,I'll kiss square and shoot a couple rounds to find pressure(while putting a light season on the bore) and mag feeding the works handily. That all before even mounting the fhuqking scope and it never seeing a chronograph. Hint.

From there,I'll conjoin rings/rail/glass that have an unerring track record,boresight and shoot a hole in 100yd paper. From there,I'll subtend POA/POI correlations,adjust same for a 250yd zero and toss a proven SWAG velocity at the whole enchilada. From there I'll go straight to 900yd steel,shoot a couple rounds and backtrack any inconsistencies. That less a fret of ES,SD or erector woe(s). With that info in hand and well under 10 pokes on a new platform,I'll have a good feel for it's Transonic Slip and will look to validate projections in it's realm. From there,it's simply a matter of shooting a barrel out while chasing lands,then simply rinse and repeat(more RPM on it's replacement,for 190 Beer Cans). Hint.

These numbers,will be SCARY close and I've yet to seat a primer. Hint.




The reticle alone,gets it to the 1300yd line and it's Supersonic to 1800yds+,in the toughest of atmospheres. Full value(10mph right angle) wind is a hilariously paltry 1.4 Mil's at the 1000yd line. 1575yds full value wind correction in a 20mph condition,is only 5 fhuqking Mil's. There really ain't much fhuqking to it. Hint.

Just sayin' and food for thunkin',aboard a "lowly" Rem 700 Factory rifle,that I gave a "whopping" $650 for. It's in the middle of today's Mail. Hint.................

Backtracking from 900, at distances are you connecting dots to finish the trajectory curve?

At 900yds,there's no way to miss steel due trajectory. It's a simplistic matter to ring same,subtend impact and either add or subtract velocity,to align the trajectory curve if needed. From there I want to go far,rinse and repeat,to get a feel for alignment towards the Transonic Slip. Hardly daunting,to tune a new platform/load,with but a modest number of rounds. The simplicity blows minds and creates THE warmest of fuzzies,because repeats are as per whim. Hint.

Outlander turned out nice on the Bart' 224 Speedmire,though it's trying to Chinook this morning. Hint.....................

He didn’t mention it explicitly in that post describing his process, but part of “backtracking” is confirming actual turret adjustment increments, which can be done using a TTT (tall-target test). By removing that variable from the equation, any inconsistencies in trajectory can be traced back to either velocity or BC error (or possibly a little of both), assuming all your other inputs are correct.

I thought I'd mentioned the importance of tracking prior?!? Hint.(grin)

At 900 any/all POA/POI discrepancy is easily subtend via the reticle,which is of course speaking fluently in the same language as the reticle. I'm not a Strelok Guy and LOVE AE for the ease in which to arrange same. You simply denote the subtended correction and enter it's value whether high(fast) or low(slow),denote the range and the corresponding comeups are backtracked less a chronograph,in a single shot. Values are of course correlated to erector value(1/10 Mil),for both trajectory and windage. Though it's faster/easier than it sounds,even if it sounds EASY,because it fhuqking is. You can continually correct/quantify an initial solution. Hint.

The approach makes it a breeze,to sort both new Lots of powder and/or temp swings. The gains are fhuqking HUGE when gunning Long Range Rimfire,because the requisite corrections are HUGE in comparison and modest deviations accrue quickly. I'm 40-50 Mil's deep in elevation daily with them. Temps/atmospherics tend to sway them more than a "smidge" too and that in itself is interesting and applicable to other platforms. With any/all new Lots of ammo,Powder or bullets,I'm HOPING nothing changes...but if it do,a couple shots will resolve all and I KNOW what is going on. Hint.

A GREAT Rule Of Thumb,is to simply factor a scope as being compromised in tracking/repeats and zero retention,until you have PROVEN that it is not. Folks are in a hurry to justify and make excuses to the opposite,which while being funnier than fhuqk,will scatter alotta projectiles about needlessly and to no end. Be MEAN to your glass,in regards to mechanics and make it PROVE itself. Less that,you are perpetually pissing up ropes. Read that again. Now one more time.

It's as easy as you want it to be and much of that depends on how you cut the check(s). Hint.

Just sayin'..................

Haha, indeed! And I mentioned it prior to that, but it warrants yet another mention to drive home the importance.

Been using AE/FTE since its inception, and after having spent time playing with nearly all of them, it remains my favourite ballistic app. Early on I asked the app developers to add the option to calibrate trajectory by varying either the BC or velocity parameters, and they said they would but never have. Doesn’t matter all that much, but would be a nice feature.

Thanks Stick and Jordan. And yes, I have read responses multiple times!

AE does allow velocity calibration, but alas, no BC calibration.

John

Sure it does. Concoct whatever potion you wish and simply calculate,then add to Favorites. Go to Favorites,pull it up,hit "load",go to BC and do whatever you please. Bump the change you deem requisite,calculate and you are done. Hint.

While it isn't Cruise Control like velocity,you can still get there in seconds. If it suits you,can correct both,in whatever percentage you factor to be the driving force. Hint.................

Of course. I was vague, but meant there was no automated process as with the velocity truing function. But yes, one can do it manually. My son, a friend and I were shooting out to a mile yesterday. And both process work pretty well.

John

Shot purty hard this evening with a bunch of stuff,but the Newest Bitch done fine. Hint.

Fired (2) rounds from the hip this morning,looking for pressure and liked what I saw,so loaded 50rds. All prior to it seeing a ring,rail or scope. Hint.



Then tore it apart for a cursory inspection and found the typical tattle tales,but let 'em ride if only in the interest of R&D. Hint.





Slammed a NightFarce steel 40MoMo rail aboard,trial fit glass/rings and had to shorten the rail for objective clearance,which is a GOOD thing. Gooped the works,slammed it tight,ran a cursory boresight on an Iggle Nest out the kitchen window and was ready to make empties. Hint.





Long story short,I missed my velocity prediction by right at 25fps,as the 1300yd steel was actually a 10.2 Mil correction,which is .2 more than my supposition cast yesterday,prior to even seating the first primer. All things considered,I don't beat myself up when a Mystic Velocity Assertion is off by less than 1%. I'd attribute the discrepency to both a new Lot of powder(slower),a touch looser than usual bore and that despite a throat shorter than most. Only slid the proposed velocity and let BC roll. Hint.




In fairness and counting the (2) pressure test hip shots,it was a total of 8rds to assert same. Fired (2) of those at 970yds. Sadly,no Cardboard ChooChoo was incorporated and it took but a coupla seconds to input the Mystic Velocity Assertion's actual and backtrack come-ups to the muzzle. Pard was shaking his fhuqking head,so I had him follow suit. 100yd boresight paper was easily resolved by FFP Gen2 Milscale Spotter(fhuqking POS Reupold MK4). FUNNIEST part was,I actually got the Goat Fhuqk X-Mark trigger to behave! Hint.



Not that I don't enjoy how folks make this schit difficult. This Rifle is yet another Myth Buster and the "surprises" none. Weather sucks too. Hint.

LAUGHING!..............

Oh crap ! ! !
You can't put any thread locker on scope mounting
hardware ! ! !
Other people don't like that.
They might get unhappy with you.

Leaving the BC alone and slightly altering the MV when supersonic seems to be the rule of thumb. Subsonic or transonic tweaks can be tweaked with the BC. This is if I read Litz correctly. Same for using the G7 with low drag bullets.

I ended up lowering my MV 1.8% and left the Litz G7 alone. It seemed to really line things up at my max range of 550. Looking forward to extending the range past that but for now it is as far as I have to shoot.