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  #1156  
Old 05-26-2020, 03:18 PM
W8LON is online now

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Only question I have though is finding ballistic coefficients of bullets? Entered .134 on my app just as a guess. Kind of fun to play with and seeing what conditions play on shooting placement.
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  #1157  
Old 05-26-2020, 03:21 PM
jaia
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http://gundata.org/ballistic-calculator/

select y'er cartridge type and brand, bc already applied
zero distance and scope height above bore.
Graph and data displayed
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  #1158  
Old 05-26-2020, 03:38 PM
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Ballpark maybe, which is what I would expect, as long as I’m paper. TRASOL app takes into effect Corialis, barometric pressure, temp and humidity as well as twist of barrel along with elevation, slope and cant. Where I’m at on the planet at the moment there is a 12” variance in elevation from gundata. Enter junk receive the same in return is the problem with these apps.
Get a bigger target!
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  #1159  
Old 05-26-2020, 04:14 PM
Gmww
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At Jaia request

I rarely shoot on paper to 200 yards. My field targets at that distance usually involve four legs. During the Spring I take my daughter out of state to shoot Sage rats at a couple of ranches to help keep them down. We usually shoot with 22lr, 17HMR, 17Hornet, 17HM2, and on occasion .223 rem.

We use Nikon Scopes with BDC reticles. I have three 17HM2's. Two are custom barrels made by my local gunsmith from Green Mountain barrel blanks in .17 cal. The third is a Ruger American made for Whittacker guns. Out of curiosity after sighting in at 50 yards with my first 17HM2 I took it over to see how it printed at 200 yards on paper. I placed a blank sketch paper below the target to see the actual bullet drop at 300 ft. above sea level.

What I found was disappointing. I don't know if I did the whole 50 rounds at 200 yards. What happened was I was getting maybe 20% of the rounds hitting paper. I then adjusted to bring the hits higher using the BDC marks. The hits if any were wild. Out of frustration I found a leaf the size of a baseball at the 175 yard mound. I shot at it to see if my scope was off. I consistently hit it.

Going back to 200 yards I got the shotgun pattern of tumbled hits. The group shown represents a small portion of the bullets that actually hit. The last photo is how this round did at 50 yards. The numbers on the target represent the torque on the action screws and actual number of bullets through this new barrel being broken in.

I have not tested the other two 17HM2's out on paper at 200 yards. I have used all of them in the field on Sage rats. Normally a miss will show up as a puff of dirt when we are shooting them. With these 17HM2's I'm not seeing the dust from the dirt at longer ranges. As comparison my 17HMR shows puffs of dirt dust when I miss indicating that I was at least close.

I've searched online about 17hm2. It seems the majority of reviews talk about good accuracy to around 150 yards. They don't indicate if they tried it out to 200 yards or longer. I did find a video of someone shooing accurately at an object 273 yards away downhill and hitting it.

Not sure what is causing my issue. Crown looks good and anything under 175 yards is hit so long as I do my part. All three of my guns are shooting similar. Shooting my Ruger Precision 17HMR is deadly at 200 but 300 seems to my where I can't hit the Rats. My Ruger Precision, CZ455, and Whittaker Ruger American in 17HM2 loses it at 200.

My guess is this is a stability issue for the 17gr. V-Max that I'm using. The question is it being caused by the 1:9 twist rate or something else. Another hypothesis might be due to external influences. Based on the Nikon Spot On program the bullet speed drops to subsonic at around 190+yards. Could that be what causing my issue as explained by this article about transonic wobble?

"What happens in terms of ballistics and accuracy, is that the center of pressure shifts forward toward the tip of the bullet. The shifting of the center of pressure lengthen the lever between it and the center of gravity, amplifying static and dynamic instability. The result is that the bullet angle of attack and yaw mightdramatically change, invalidating all the trajectory predictions made by ballistic software, and making it impossible for us to compensate correctly for drop and drift. It might also produce an increase in wobble, which can lead to an accuracy decay and can make the bullet tumble. That’s the reason why shooting beyond the transonic range (the distance at which the residual speed reaches Mach 1.2) results in “key holes”, that is, holes made on the target by tumbling bullets that impacted on their side, instead of at the tip." https://sofrep.com/news/long-range-s...nsonic-region/

I frankly don't know for sure what the problem is. I do know that Sage Rats go poof under 200 yards when hit by the 17HM2. Others on this forum have reported success at longer distances. I read where some have had similar results as I did with keyholing. https://www.rimfirecentral.com/forum...hlight=keyhole



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  #1160  
Old 05-26-2020, 04:15 PM
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Okay now I’m in pursuit of quantitative data. I have stuff and time on my hands. Clamp survey rod to backstop, measure drop and wind drift from 200 yards with a transit. Also can measure slope on the range up to 12’ with this rod. Just clamp a sighted to the c/l of scaled plywood hunk, and away we go!
Can never have enough stuff to haul to the range either.

Last edited by W8LON; 05-26-2020 at 04:50 PM.
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  #1161  
Old 05-26-2020, 05:26 PM
jaia
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Y'er having way too much fun with this W8.


Gmww, thanks for the 17hm2 results at 200 yards.
Not a lot of information with that cartridge at extended range.
Keyholing was not what I expected.
I was thinking they would carry like the 17 hmr.

What's y'er twist in that rifle?

Last edited by jaia; 05-26-2020 at 05:29 PM.
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  #1162  
Old 05-26-2020, 05:35 PM
Gmww
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Quote:
Originally Posted by jaia View Post
Y'er having way too much fun with this W8.


Gmww, thanks for the 17hm2 results at 200 yards.
Not a lot of information with that cartridge at extended range.
Keyholing was not what I expected.
I was thinking they would carry like the 17 hmr.

What's y'er twist in that rifle?
1:9 I believe.
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  #1163  
Old 05-26-2020, 07:47 PM
jaia
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Playing with the different hm2 cartridges, CCI VMax, Hornady (made by CCI)
and the calculator, the CCI runs a bit faster and doesn't go transonic until past 200 yards.
The Hornady is in the transonic zone right at 200 yards.
If you were getting MV's less than those rated on the box, you'd be in the transonic earlier,
guessing about 170 yards, so I can see where the keyholing would happen.
I'd want to use a chronograph to see what those cartridges are doing.
You may have a batch where the primer/powder isn't up to spec.
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  #1164  
Old 05-27-2020, 02:16 PM
Gmww
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Quote:
Originally Posted by jaia View Post
Playing with the different hm2 cartridges, CCI VMax, Hornady (made by CCI)
and the calculator, the CCI runs a bit faster and doesn't go transonic until past 200 yards.
The Hornady is in the transonic zone right at 200 yards.
If you were getting MV's less than those rated on the box, you'd be in the transonic earlier,
guessing about 170 yards, so I can see where the keyholing would happen.
I'd want to use a chronograph to see what those cartridges are doing.
You may have a batch where the primer/powder isn't up to spec.
https://www.rimfirecentral.com/forum...hlight=keyhole

From the above link Joet333 post #15 chronicled his experience testing several brands of 17hm2 and also took measurements of the seating depth. Of interest to me was his experience of what happened at 200 yards. His observation of the Hornady 17gr V-max that advertises a 2100 fps muzzle velocity showed that at 200 yards it did not keyhole but were in his words "inconsistent". He also had inconsistency with ammo within the same box. His conclusion agrees that lots seem to make the difference. He had similar keyhole results with the CCI which advertises a 2010 fps muzzle velocity. So it seems to be that 90 fps muzzle velocity appears to make the difference of keyholing 200 or not. The keyhole strikes had been disappointment to say the least for me.

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  #1165  
Old 05-27-2020, 02:20 PM
jaia
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Y'er right G.
I flipped the brands when I was typing the post.
The Hornady is supposed to be faster.
Dyslexia is a wonderful thing.
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