Truing muzzle velocity

A month ago I went to our range with my magnitospeed to re check our 3 rifles because I had switched from dry media tumbling to wet. I discovered that for some reason, although I have my own theory, all 3 rifles slowed down around 25 fps.
Also I noticed that my 260 had some pretty bad consistencies. I was asked if I annealed and if I had checked it with tempilaq. I have not ever checked it only gone by the dark room technique.

Robinhood sent me a bottle of tempilaq and I discovered that indeed I had the speed of the machine set pretty close. The main problem with that was I had the flame way to close and wasnt getting even heating over the whole neck and shoulder.

Ill try and make a long story as short as possible.

The High SD's really bothered me so I decided to check and re check every measurement. Good thing I did. Honestly I had been on auto pilot for months and hadnt pulled out calipers to check anything. Well I did and here is what I discovered. I use the Redding type S full lenth sizing die with their piece of crap ring on it. Apparently they all loosened, which they did regularly, and slipped and were no longer bumping the shoulder back at all. I replaced them all with Forester rings. Now as for the slow down with the stainless media. My theory was they were super clean and now the bullet was slightly more loose in the neck. So I dropped all three down one bushing size to counter that effect and all the numbers came right back up. Now that everything is re set and re measured I went to the range to see what the "final" MV was of all this change.

Here is where im getting to my question. Ill use my rifle only as an example.
Magnetospeed average MV 2800 SD 8.3 over 10 rounds fired.
Ok great. I punch all that into my calculator and get set to shoot 300 yrd target. Only Im 3" high. I think I recall Litz saying to true the MV inside the transonic and the BC at the transonic so I measure what the drop should be to be on target and true the MV. It bumped it up to 2900 ish. I reluctantly chose "use this velocity". Now I drop down to shoot 500 yrds at an 8" target. HIGH. So I adjusted to hit center and trued the velocity once again. The actual vs measured and now the mv is like 2974. REALLY?

What is up with that? I confirmed that at that mv I hit dead center at 508 yrds. I had 1.5" group at that distance 1 inch to the right of center. But is the calculator wrong. Is the magnetospeed wrong? I am using the g7 BC that 140 gr berger hybrid says to use.

what is going on? Why are the numbers that far appart?

One of the best posts I have seen here in a while Doc. Is the actual BC of your bullet the same as the published BC? Alter the BC in your equation to verify? What variable is off....

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Originally Posted by Robinhood

One of the best posts I have seen here in a while Doc. Is the actual BC of your bullet the same as the published BC? Alter the BC in your equation to verify? What variable is off....

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Probably not because BC is affected by velocity. Listed BC numbers are best used to sell bullets.
Confirming information by actual shooting has always been necessary.
And the further away the target, the more necessary it becomes.

Thank you sir. Ive been working on this issue since you and I talked last. In fact the reason I was looking for 243 brass a couple weeks ago was because I didnt have any pristine brass to measure in comparison to what I already had. I am aware of the maximum measurements for all the actions of all my long range guns, but I also like to know what Lapua sends out as standard measurement. Anyhow, I found some on another board. So back to the issue at hand.

One would think, I would think, that if the actual MV is accurately measured, the correct BC is used and current DA known that you should be able to input a distance and get the approximate drop at that distance. I am sure there MUST be error built in to the calculations and conditions do indeed change. This time however, at the time of MV collection, I was careful to collect all conditions on the day of zeroing.

The very next time to the range we shot at 300 yrds. This had the sole purpose of verifying the ballistics and see if the "new accurately loaded" round grouped well at distance. Well they grouped quite well just high. To high to just accept for that. All calculators have a "truing function". So I looked at that. I had the option of truing the MV or the BC. At first I chose the BC. The G7 bc for my bullet is .311 per the manufacturer. I forgot what value is gave me but it was quite low, very different from the published value. The .311 value was supposedly an updated Doppler confirmed value so I went the other way. So I measured what the actual drop should have been and my MV went up.

The next time to the range was now at 500 yrds and current conditions and new MV. I ranged the target, fired 3 rounds at an 8" target, drove down to the target just to see NOTHING. From experience I dialed down .2 mils and was on paper I had to dial back up .1. Ill try to upload a pic in a bit.

Suffice it to say that the mv went up a little more. Teresa's rifle also went up through this whole test period as well. Her's went up substantially more than mine. Granted I shoot 260 and she 6.5 creed. Her barrel has always been fast, real fast.

I just want to know WHY is there sooo much difference between calculated and reality. I use strelok pro and that program gets bashed but Ive compared it to 2 others and it calculates exact numbers as 2 of the other leading programs so Ill stick with it. But that doesnt answer my question. The only thing is the BC. Could the published bc be incorrect? I have asked others in the past 6 months and as far as I know everyone is using the .311. We will go back out tomorrow under MUCH different conditions and run it one more time then re check zero. I wont have time to measure mv again, well I dont think so at this point. But I seriously doubt its actually almost 200 fps faster than last time.


Im still trying to get the pic..... I hate photobucket

Yobuck, I hear what you are saying about BC's used to sell bullets. But in this case, actual is better than calculated. That means that what I am getting out of my rifle is much faster than using the calculations based on the bc they gave me. Why would they publish a bc that is not as good as it actually seems to be performing?

That is my dilemma.

Attachment 2778
This was the final group at 508yrds. The patches below that was the inital OVER adjustment from flying the target on the first shots.

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Originally Posted by doctnj

Yobuck, I hear what you are saying about BC's used to sell bullets. But in this case, actual is better than calculated. That means that what I am getting out of my rifle is much faster than using the calculations based on the bc they gave me. Why would they publish a bc that is not as good as it actually seems to be performing?

That is my dilemma.

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We all see and read things differently.
I certainly don't see any (dilemma) with your shooting ability or the accuracy of the gun, and that's about all you have any actual control over to any degree.
The rest is what it is, and tomorrow is a new day.
We are being brainwashed, mainly by people with products to sell that this is or at least can be an exact science.
And your finding it to be otherwise. Thank goodness for old fashioned sighter shots.

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Originally Posted by yobuck

We all see and read things differently. I certainly don't see any (dilemma) with your shooting ability or the accuracy of the gun, and that's about all you have any actual control over to any degree. The rest is what it is, and tomorrow is a new day. We are being brainwashed, mainly by people with products to sell that this is or at least can be an exact science. And your finding it to be otherwise. Thank goodness for old fashioned sighter shots.

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A wise man was once overheard saying " I don't always pay attention to what people say but when yobuck utters his wisdom, I listen. Stay thirsty my friend.".

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Originally Posted by doctnj

Yobuck, I hear what you are saying about BC's used to sell bullets. But in this case, actual is better than calculated. That means that what I am getting out of my rifle is much faster than using the calculations based on the bc they gave me. Why would they publish a bc that is not as good as it actually seems to be performing?

That is my dilemma.

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To sell expensive bullets to people who don't test them. Nosler has, for years, been known to inflate their bc numbers. When they came out with the accubond long range, stating .719 g1 bc from a 142g bullet, long range shooters everywhere lost their tops. After being debunked by some of the premiere ballisticians today, nosler still stands by their inflated numbers. I think Litz calculated and confirmed with Doppler that it was closer to .647.

http://www.longrangehunting.com/foru...-719-a-154384/

I would be looking at at other factors. A headwind, a tailwind, atmospheric conditions, the position of Venus, something you aren't seeing right would be my suspect. We shot yesterday and had a similiar issue. I had to adjust my dopes on the fly. To true my ballistic calculation with the drops I was seeing my, .260 would have to be shooting 142 smk's at 2950+ when in reality it is still at 2850. A normal 850 yard dope is 20.5. My adjusted yesterday was 18.5 Moa. There was some voodoo in the air and it threw the whole line for a loop.

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Originally Posted by Robinhood

A wise man was once overheard saying " I don't always pay attention to what people say but when yobuck utters his wisdom, I listen. Stay thirsty my friend.".

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Call it whatever you like, but i wouldnt call it wisdom. Id call it reality, and believing what you see, and not what you'd like to see.

Everybody has a chip latey.

Ok on a different note. I have my rifle trued at distance now (for conversation sake anyhow) I noticed I.E. in the pic that my windage was off. Yesterday I went to 100 yrd target to check windage and sure enough it was off but so was my elevation. Elevation was low by .1 mil. Thats not very much and we dont shoot for x's in our competitions. Im afraid if I bump it up that .1, it will throw off all my long range stuff. I have a competition this coming Sat. and may not have a chance to get to the range but will if I have to.

Should I go ahead and make that adjustment then check at distance and true one last time?

or
Leave well enough alone and realize "thats close enough besides you will almost never shoot anything at 100 yrds"?

What scope are you using? If all the data is correct and imput into your calculator properly your drops should come out within at least a click or two of your actual shot data. Do you have your scope height set at the correct value and not the assumed 1.5"? What direction are you shooting? Rotation of the earth can and does affect trajectories. Is your temp, altitude and pressure input correctly? Are you using a G1 drag model or a G7 drag model? This alone can make a big difference but if any of these things are off the results can be compounded. I have a hard time thinking the magneto speed is off as they are a very reliable piece of equipment and have been independently tested to be accurate within +- 1fps. Have you performed a tall target test to verify that your scope is level and tracking vertically and the right amount per click?

Ok Ill run down the list of your questions.

Scope vortex vyper pst ffp 6-24x50
Scope height used calipers from center of vent hole to center of precision vortex rings that are properly torqued on a 20 moa base
Direction of fire NNW 3 degree down angle
drag model G7 of .311 I use kestrel drop for zeroing weather and updated at every shooting event that data is input via blue tooth

So yes that is why Im stumped. Maybe I have a goofed up magneto speed?

If the magneto speed is accurate and everything else in properly inputted, then the BC is the only thing that could be off.

BUT here is the deal.. the bullet is flying further than calculated!!! performing BETTER than calculated. I routinely have to dial down a couple clicks to get on target.

I had to do the same thing when I finally started shooting at distance last year and again this year. I started off completely fresh this season because I changed my brass prep and measured EVERYTHING again. I also used a tighter bushing in my sizing die. Therefor I did not trust my data from last season. and good thing because it changed.

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believing what you see, and not what you'd like to see.

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Amen!

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Originally Posted by doctnj

Ok Ill run down the list of your questions.

Scope vortex vyper pst ffp 6-24x50
Scope height used calipers from center of vent hole to center of precision vortex rings that are properly torqued on a 20 moa base
Direction of fire NNW 3 degree down angle
drag model G7 of .311 I use kestrel drop for zeroing weather and updated at every shooting event that data is input via blue tooth

So yes that is why Im stumped. Maybe I have a goofed up magneto speed?

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Well I hate to say it, but the weakest link in your set up is probably that Vortex scope. I have had so many issues with vortex scopes, especially with their tracking ability or lack there of. I would seriously perform a tall target test to verify that your scope is moving corectly and vertically. It may turn out that your scope is working fine other than it is moving slightly more each click than it is supposed to so you end up dialing more elevation than you think you are. Possible you have a lemon magneto as well, but the velocity readings seem more in line with typical velocities than your trued one.

I did a tall target test last spring when I put my custom gun together. If I remember right I went up to 6 or 7 mils only but that encompassed all of the ranges we shoot at. The one thing I noticed doing that test was a slight horizontal shift as I went up. I hung a long level to put my reticle against to try and get it set right. I wound up scratching another line in my bubble level about a mm away from the original.

But to be honest I dont remember anything else about that test that stands out. When I have time Ill do another one with all 3 of my rifles that have the same scope on them. You may be on to something.

If they are not tracking right, I guess I could send them back in to be fixed?

Yeah, the nice thing about Vortex is they will fix it free of charge and no questions asked. Problem is I started to get to know the Vortex Warranty guys on a first name basis because I was calling them constantly.

when you sent something in for work, What was average time turn around?

Best to use a plumb bob on a string as opposed to a level for making a plumb line on something.
A heavy fishing sinker would work well enough for that, as would a chalk box which would allow for snapping a line also.
Drive in a nail on top and hang the device from it. A level isn't always a good level, reverse it without flipping it over, and see if it reads the same. Don't just assume the level you have or somebody hands you is good.
But even if the scope dosent track 100% perfect, so what?
A slight wind read error could cause the same thing, or a wind change while your shooting.
I can see where in a match with no sighters permitted it could be important, but otherwise just make the correction and shoot.

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Originally Posted by doctnj

when you sent something in for work, What was average time turn around?

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I generally had it back in hand in about 2 weeks.

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Originally Posted by doctnj

when you sent something in for work, What was average time turn around?

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I sent mine in right before Christmas, had it back at the end of January. I have an hs-t that sees heavy use and was missing some teeth. It would, for lack of a better term, get lost when dialing up and down. I think the missing teeth were between 6 and 7 Moa, it just seemed like every time I went above or below 6moa it would wander further from zero.

As as for the plumb bob, that is the way to go to level your scope. You can pull the bolt and make sure it intersects the bore perpendicularly and then reach up and level the scope on the same line. I have a nail in the door frame at the end of the hall for just that.

I actually have a plumb bob from the days of pool installation. Ill give that a look and see where they are. Its more likely than not that I will leave well enough alone for the next 2 weeks though. We have back to back matches and have everything trued to what the heck ever velocity is coming out of the rifles at this point. I know being off level can throw off horizontal as well as some vertical effect at distance. I simply dont have time during either of these weeks to re set then go re test all of them. Ill check them for sure, I just cant do anything about it till we have a weekend off from matches.

And Yobuck, there are no sighter rounds in PRS. Every shot counts, or doesnt count however you want to look at it. It seems most every match has a special first stage that is "cold bore". So your rifle isnt warmed up and you have to make a shot out to like 600yrds. So you rely on your previous dope and a wind "guess" and go for it. Plus first shot jitters which is the worst because everyone is watching you because we do this one at a time. Heck at my very first match I could hardly get the magazine in the rifle, my hands were shaking so bad! lol needless to say I missed. I wasnt even sure where the crosshairs were when I pulled the trigger. lol

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Originally Posted by doctnj

And Yobuck, there are no sighter rounds in PRS. Every shot counts, or doesnt count however you want to look at it. It seems most every match has a special first stage that is "cold bore". So your rifle isnt warmed up and you have to make a shot out to like 600yrds. So you rely on your previous dope and a wind "guess" and go for it. Plus first shot jitters which is the worst because everyone is watching you because we do this one at a time. Heck at my very first match I could hardly get the magazine in the rifle, my hands were shaking so bad! lol needless to say I missed. I wasnt even sure where the crosshairs were when I pulled the trigger. lol

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Sounds like a common case of buck fever lol. Even worse would be running the whole mag thru the gun without firing the gun.
Which is why most of the guys I know only use single feed guns. lol
But again, I'm not a competitor, and never have been in any serious manor.
I know about and appreciate the effort that goes into it, and I also fully realize the products and equiptment all of us enjoy using today has come about to a large degree as a result of the demands of competitive shooting and shooters.
Just how much of the equiptment, and the mindset/technique required for one aspect of the sport is a (requirement) for another aspect, seems to be where opinions can vary.

I breezed through most of these posts and the one thing I never saw mentioned was truing your scope height. I've found this to be a large factor in getting correct drops as well. I had a lot of these same issues when I was truing data within the "Shooter App". I've since switched to BallisticARC in conjunction with the WeatherFlow Meter and it's been treating me very well!

This is the kind of stuff that'll drive you crazy. I've had to tweak my bc,s a bit more so for G7 and longer pills. Oddly enuff, I cked my speeds using a buddies magneto as well. I'm off by maybe 1 moa out to distance. I haven't started my diagnostics yet because I've simple adjusted for the errors and am good with that for now because I'm shooting set distance s from 200 out to 1300yds.
1st process I do when I start my mad scientist diagnosis is double cking my speeds with different chronographs. I know for a fact that were not the only ones who play around with the bullets bc...drag....speeds....and given drops at given distances to make it match up with our actual drops.

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Originally Posted by eddiesindian

This is the kind of stuff that'll drive you crazy. I've had to tweak my bc,s a bit more so for G7 and longer pills. Oddly enuff, I cked my speeds using a buddies magneto as well. I'm off by maybe 1 moa out to distance. I haven't started my diagnostics yet because I've simple adjusted for the errors and am good with that for now because I'm shooting set distance s from 200 out to 1300yds.
1st process I do when I start my mad scientist diagnosis is double cking my speeds with different chronographs. I know for a fact that were not the only ones who play around with the bullets bc...drag....speeds....and given drops at given distances to make it match up with our actual drops.

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Well again, all this is very important for those reading it who happen to be competitive shooters where first round hits are imperative.
Otherwise (I personaly) don't feel its worth losing much sleep over because of the many things involved which you cant control.
All these type discussions of coarse involve shooting, and most if not all discussions involve some type of a range, or a place chosen by the shooter where they can shoot with no obstructions to shoot thru or otherwise hamper the shot.
But go someplace where you can stand under a large tree like say an oak tree, and look up, and envision another tree over there and there and everywhere because the whole area is woods, with many various size branches overlapping each other.
Now look at your shooting data and determine where your bullet will be as for height above ground when it gets out to say 700 or more yards.
Even a slight touch by one of those countless branches will send your bullet off coarse, and it could very well cause it to go no further.
There is no way to compensate for that other than to get another round in the air asap.
Now admittedly not everyone reading this shoots in that type environment, but many of us do while hunting long range.
Another example would be the various types of terrain, as for flat as opposed to hilly or mountainous.
Picture a dart board hanging on a wall, and then picture it laying on a table or in any other position and then determine which position you would rather shoot at it. The game would become a totally different game depending on the position or angle of the board.
Now add some branches in front of the board and the game changes yet again.
So again, depending on where an individual does his shooting, or hunting, will likely have a strong influence on his (opinion) as to order of importance of various equiptment and shooting techniques.

I lived in PA for the first 64 years of my life, and at age 12 was taken to the N C region of that state by my father to hunt deer.
After about 5 years we relocated to a different area, about 50 crow fly miles to the N W, which is where Im still involved in a camp and hunt today.
With gods help, this fall coming will mark 70 years since that first trip.
A lot has happened during that period regarding shooting, but has it really?
We hunted exclusively the way many others did back then, and some still do, by organized deer drives on those steep side hills.
My chosen gun then since I'm a lefty, was a then new model 141 Rem in 35 rem. A very popular choice then, along with the even more popular 94 Winchester 30/30, and the 99 Savage, mostly in 300 Sav. Scopes of any type would be rarely seen on guns, and wise comments were often made towards those who used them.
PA by the way ranked in the top 3 as for hunters, along with Michigan and Texas.
In the fall of 1955, I was driving a new 55 chevy with the loudest pipes I could get. lol.
We were in my car, with a couple other cars making up our group. It was mid afternoon, and we didn't have enough day lite for another drive, so we were headed back to camp.
Talk about a poor way to utilize man hours, that method of hunting has to be the worst for that.
Anyway we were headed down a dirt mountain road known as Montours run rd, which is right at the northern Clinton co, and S E Cameron co line, when we had to stop because there were a few cars and a group of guys blocking up the road.
There was a guy sitting on the road shooting at a side hill across the valley.
We got out and joined in with the others standing around watching.
There were always guys patrolling that road and glassing across the valley, and this guy was one of them.
There was considerable brass laying on the road from his shooting, and after a few more shots he stopped shooting and started picking up his brass.
There were 2 other guys standing there who were also regulars along that stretch of road, and when the shooting stopped, one of them asked if he were finished, and if he would mind if he shot.
He then went to his car and removed the seat section of the rear seat and placed it on the road.
He got out his gun which was a model 70 Win 270 with a Unertle target scope on it.
The same type I was using then for shooting indoors with a Winchester model 52 22 rifle.
The buck was laying down and had never gotten up during the first guys shooting session.
I'm sure at this point that the second shooter was evaluating what he saw and it could have helped him. But in any event, on his 3rd shot the deer was dead, and as I recall he hit it also
on his 2nd shot.
There was no rangefinder in play, and the only ones available then were the large military ones.
I don't recall any discussion over how many clicks he added either, but that's not to say he didn't.
But he surely he did something right that the first guy didn't.
I was blown away by that shot, I think it was the single most important event in my years of hunting. Without my fully realizing it then, it affected my attitude toward the way I hunted, and even toward those I hunted with.
He had to know what the distance was at least reasonably close.
I did ask him how far it was and he immediately responded 700 yds.
In the late 60s, a few of us in the group decided to devote all of our time toward glassing sidehills and shooting across those valleys.
I soon obtained a Barr&Stroud military rangefinder, and one of the first things I did with it was to check the yardage of that shot still etched in my mind.
I found that the guy who's name was Ray Diamond from Pittsburg, was right on with his answer to my question years earlier. So he had to have had ranged it before that day.

Fifty years later at age 70, I killed my first and only PA black bear from a lookout we made on the hill right above that spot on the road.
The bear was running up the steep hill across the valley, and I was following him in the 3.5x 10 Leupold with a custom multi dot reticle programed for the 162 gr hornady load in my 7x300 Weatherby.
The scope had no target knobs at all, but since, ive had an elevation only knob installed.
My son was watching him also thru a set of tripod mounted 12x60 German WW2 binnocs, while holding our range information for that spot in his hand.
The bear finally stopped about 3/4 the way up the hill and I asked, how far?
His answer was he isn't real close to any of our ranged spots, but id say he's about 700.
I said well I'm gonna hold my 700 dot on top of his shoulders, and with that I sent it over there.
He went down instantly, But as bears do, he got up again and tried to go.
He went just a short distance uphill, before making an abrupt change in a direction across the hill.
I said to my son he's hurt bad to have done that, but then I missed him very close on the second shot.
But a third shot about as fast as I could chamber another round dumped him for good.
The dead bear was laying within 100 yds from where that deer was when I witnessed my first long range shot 50 years earlier.
That's long range hunting, at least where I do my long range hunting, and no it dosent always end happily, at least for most of us.
You might have lots of time to evaluate all the conditions before a shot, and you might not have time for any of that.
Reality is your probably better off if your just pretty good at doing both, and learn to hit the curve balls, because for sure there coming.

By the way, when we first saw that bear, he was coming out of thick laurel and within 100' of us sitting on that lookout.
My son had heard him coming by the noisy leaves on the ground, but we were fully expecting it to be a deer.
But he either saw or winded us, and was gone in an instant back into the laurel and down the hill.
Fortunatly, I found him going up the hill across the valley with my large glasses, sorta like finding a fly on a big pile of straw.
And yes luck plays a big role, as it often does.

But based upon what you've just read, what would you think to be the most important thing or item of equiptment a long range hunter, again (hunter), could have?
Besides luck, and a gun of coarse, but could even that answer be debatable?
Now for sure somebody will be thinking yeah but you gotta have a good chart. lol