Estimating velocity from dope.270win

[DesertDug]

I have a cds cap needing to get set up. I have landed on the classic load of 60 gr of H4831. Took to the range today on shoot 50, 100, and 200 yards. The thought is if I replicate the dope off same poi I could come close in guessing velocities and provide this information to Leopold to get the cap made.

I used the hornady billistic calculator. https://www.hornady.com/team-hornady/ballistic-calculators/#!/standard

shoot groups of 5@50, and 10 @ 100 and 200. Excluded the pulled shoots and cold bore. Took vertical measurements off aim point. These results were replicated in the calculator and I came up with 3,450 fps. This seems high out of the end of it's 25" barrel.

Anyone have a better way to approach this or am I headed in the right direction?

Here is a screen shot othe the dope chart with 50 yard zero and 200 yard zero for 3,450.
https://i.postimg.cc/Y9DNS9K3/IMG-1786.png (https://postimg.cc/yg93Q7Ng)

https://i.postimg.cc/sXMyt6V2/IMG-1785.png (https://postimg.cc/TLvZbc58)


https://i.postimg.cc/CLNtsCgr/image.jpg (https://postimg.cc/LnJNH1hj)
https://i.postimg.cc/gjKM4pfL/image.jpg (https://postimg.cc/30dCJsr3)https://i.postimg.cc/nz3j1w3c/image.jpg (https://postimg.cc/TLW3dQ8Z)

[scootergisme]

Looking at the Hodgdon load center data for 4831, 62 grains pushes a 110 grain bullet 3214 f/s with a 24" barrel. You didn't specify your bullet or bullet weight, but it sound like 3,450 f/s would be too high of a velocity. What bullet and bullet weigh are you using?

[celltech]

Based on the information in the Hornady app you should be able to get close. The temp and altitude will also play into things and don't appear to be in that app? I use the Strelok app on my phone and it can figure out the velocity based on actual drop as well, but I have never used it.

[DesertDug]

Looking at the Hodgdon load center data for 4831, 62 grains pushes a 110 grain bullet 3214 f/s with a 24" barrel. You didn't specify your bullet or bullet weight, but it sound like 3,450 f/s would be too high of a velocity. What bullet and bullet weigh are you using?

130 gn bullet. Cas compactly is 67.1 grains of water.

[DesertDug]

Based on the information in the Hornady app you should be able to get close. The temp and altitude will also play into things and don't appear to be in that app? I use the Strelok app on my phone and it can figure out the velocity based on actual drop as well, but I have never used it.

What kind of velocity are you coming up with based on pics?

The hornady does have one with more variables such as altitude. I am shooting problem at 20' amsl, on the cost of Texas. Temp was 54 degs.

Nosler has published velocity of 3124 for 59.0 24" barrel. I am shooting 25" 5r 1-10 twist x-caliber barrel.

[Robinhood]

Due to the flat shooting nature I would drop the 50 and add a 300. What bullet did you use for your calc?

[DesertDug]

Due to the flat shooting nature I would drop the 50 and add a 300. What bullet did you use for your calc?

Do not have access to 300 yards right now. Nosler 130 bt b.c. 0.433.

Does anyone one have the " quick load" application?

[12bhunting]

That seems a little high for 130 grain.

[celltech]

I setup a test 270 load in Strelok with your round. The Nosler .270 130 BST has a G7 of 0.199/G1 0.433. I am confused by your photos...did you set a 50 yard 0? Assuming you did, the 100 yard POI at 3400 should be -1.12 MOA and -.41 at 200. At 3100 fps the 100 is -.96 and 200 is .09.

I think that at these short distances it would be impossible to get an accurate read on your velocity. You can swing several hundred FPS and have variances that might be outside of you and your guns ability/accuracy to verify. Even at 500 years the difference between these speeds is only 2 MOA (5 and 7 drop).

Buy or borrow a chrono if you must have the most accurate reading. But if you had to guess, I would say you are closer to the 3100 range.

[darkker]

Yeah, careful with Nosler's claimed G1's; they have been sandbagging it for years.
G1's are always stepped by velocities, and many times not achievable in the carriage being fired.

[DesertDug]

Yes 50 zero.
100 yards +1.05
200 from group would be either 0, just below 0 or up to -1.5" average @200.

[celltech]

Here is what I plotted...

[DesertDug]

Celltech, so it may be pushing the higher velocities. I say this because the 100 yard is above poi. 3200-3400 range?

Is there a better way to go about this without crono?

[celltech]

In both plots the 100 yard is above POI...the minus sign indicates that. -0.96 for 3100 and -1.12 for 3400. No offense, but you were not exactly shooting bugholes at 50 or 100 yards. The drop difference between the 2 velocities is so slight that I would not trust the groups alone....especially at only 200 yards.

[DesertDug]

In both plots the 100 yard is above POI...the minus sign indicates that. -0.96 for 3100 and -1.12 for 3400. No offense, but you were not exactly shooting bugholes at 50 or 100 yards. The drop difference is so small between the 2 velocities is so slight that I would not trust the groups alone....especially at only 200 yards.
non- taken. It was a gusty windy day. not the best for shooting groups. Any other ideas?

[yobuck]

We need to be asking ourselves as individuals, just what it is we are attempting to do with the information were looking for.
Certainly today with the information available on various sites, owning a chronagraph isn't necessary in order to learn the velocity of our load. Just remember that tomorrow it might not be, at least exactly. Thats just the way it is, and owning the best chronagraph wont change any of it.
A hunter leaving from say Florida, with an elevation above sea level of almost zero, can prepare a chart similar to those produced by Celltech for a Colorado hunt @ 7000' before he leaves Florida.
But he should only be looking at that as ballpark information at best.
Certainly those who get warm feelings by making first round hits, need to be evaluating lots of information for a shot before they shoot.
But as a rule, that dosent work very well when long range hunting for various reasons. And note I did say "as a rule".
So the important thing then is having the ability to gather the information you just saw happen, and fix it for the next shot, assuming there will be one.
Another problem for a hunter, could be not actually seeing what happened on the first shot, which is another subject.
Look at the 2 charts prepared by Celltech, and evaluate the differences in actual distance the bullet would land from the aiming point even with the big differences in velocity. Then ask yourself would that make much difference for your second shot?
And if it does, then thats where you need be focusing your attention, and not with having a perfect chart.

[DesertDug]

thanks yobuck for bringing me back to reality. What I am trying to do is provide the best most accurate information to Leopold for setting up my CSI cap. The CSI cap replaces the elevation turret cap to be marked in distance, so no dope chart needs to be referenced proving quick adjustments. Now I understand that this type of cap is inherently not precise as it would be set for one velocity, elevation and temperature and will be slightly off if any variable changes. This is for a hunting gun and should get me within minute of kill zone.

Is there a way to calculate a velocity by charge and type of powder, weight of bullet and shape and column of case? Maybe I could see where that falls into possible speed. I just ant to get a good estimate to use with out buying another piece of equipment that I do not see using all that much.

[CFJunkie]

DesertDug,

I would be a bit cautious about making a calculating velocity based on your three targets, because I think there is more shooter induced variation in the groups than you might think.
In fact, I believe your rifle may be shooting much more accurately than you believe.

First, the three targets show groups of 2.514 moa at 50 yards, 2.209 MOA at 100 yards, and 1.950 MOA at 200 yards.
Second, the horizontal dispersion on all three targets is a big contributor to the group sizes and to the determined POI position.
At 50 yards ,the horizontal dispersion is 1.285 inches or 2.5 MOA. I suspect that the majority of that (+/- .6 inches) is shooter induced variation. The vertical dispersion is actually about .7 MOA.
Note that the cold shot is high and to the right by 1.5 inches. I agree that you should throw that out. Most of my accurate rifles shoot a cold, unfouled shot high and to the right.

At 100 yards, the horizontal dispersion to the right is almost 2 inches, but the groupings are to the left compared to being on the right at 50 yards. That might indicate that you reset your set up when you shot at 100 yards. The horizontal dispersion to the right is about 0.7 inches. I suspect that the one far right hole was caused by the rifle butt resting on your shoulder bone instead of the inside edge of your shoulder bone.
Also note that the cold shot is low and in line with the aim point. I don't have one rifle that shoots high when it is cold and then low when it is allowed to cool down. I have rifles that shoot either high or low when cold but not both. I would suspect that the cold shot at 100 yards was shooter induced not barrel induced. You're right to throw it out, but it indicates set up anomalies more than barrel temperature.

At 200 yards, your POI is to the right like it was at 50. It is hard to understand why the 100 yard POI is to the left when the 50 and 200 yard targets show to the right without suspecting shooter set up.
You have 5 rounds that group within an inch at 200 yards about 0.5 inches low and 1.7 inches to the right - that's 0.5 MOA. If that is indicative of what your rifle is doing, you conclusions will be much different.
But you have 5 other rounds at 200 yards that have a 3-inch horizontal dispersion and a 1.7-inch vertical dispersion that are 2 inches low about 1.5 inches right with the same aim point. When they are included, your conclusions turn out completely different.
Those five shots don't look like rifle caused to me - they look like shooter caused variations.

Sorry to be critical, but there are too many indications of variations in set-up that would suggest that the overall groups are not statistically stable enough to make a judgement about velocity.
On the positive side, your 200 yard and 100 yard targets give indications that the actual median point of impact might be much more predictable if you could eliminate some of the horizontal dispersion and tighten up the occasional drop. But the resultant POI would be different than you are considering now.
Trying to conclude anything about velocity when including the large vertical and horizontal variations will only lead your conclusions astray.

[DesertDug]

thanks CF Junky. I agree that the groups are more a result of my shooting, and not that of the riffle. I will keep practicing and give this another try.

[CFJunkie]

Don't get discouraged.
It took me 3 years of really working, shooting over 5,000 rounds a year, to get most of my shooter induced variations under control and I didn't have anyone to help point them out.

I hope that suggesting a few things to consider might make your personal quest a bit shorter.
As I said above, I see some good indications but there are enough variations to not be able to make any conclusions.

The first step is to recognize that you have work to do, and you have already done that.
After that, concentrate on getting your set up consistent and you'll be surprised how quickly things get better.

I would suggest that you find the rifle you shoot best - it probably fits you the best and you set up more comfortably and consistently - and then try to identify probable variations with every shot.
Your targets will tell you if you were right.
Everything you do to get consistent will carry over to your other rifles, but having the confidence to identify problems will give you the biggest payoff.

Jumping from rifle to rifle while you are trying to get consistent will mean that you will have to figure out everything on the fly with a lot of changing conditions.
It just makes things tougher.