6.5 140 AccuBond BC off?

[bboswell]

Is the advertised BC pretty close on these or no?

6.5 PRC dope is being problematic.

Last 5 shot group only recorded 4 shots on the LabRadar but with ES of 4 and SD of 2 which makes me pretty confident in velocity.


Shot at 375 today as that’s as long as I can get at home and it shot 1/2 MOA but a full minute low.

I have double checked all input date including scope height and can’t get dope to match real without huge adjustments to either BC or velocity.

Unless these are known for erroneous BC numbers I will confirm 100 zero and then shoot a box to confirm turrets.

Ideas?

[canny]

I’d true up the BC, if you’re confident in the velocity


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[1longshot]

I would search for Bryan Litz's bc numbers on the 140 accubond, they will be better to go off of than noslers.

[bboswell]

I’d true up the BC, if you’re confident in the velocity


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Given the chrono would you be confident in the velocity? I will add that’s the velocity is consistent with through the load development but the last load added some neck tension which really tightened up ES & SD.

[canny]

6.5 140 AccuBond BC off?

Given the chrono would you be confident in the velocity? I will add that’s the velocity is consistent with through the load development but the last load added some neck tension which really tightened up ES & SD.

Gotta start somewhere. It’s all physics you have a mass and a velocity. You can adjust either one to get the drop data you need. I would start with the BC. You only checked it at 375 this isn’t far enough to give you good data. I would take the rifle as it sit, go shoot it out to at least 5-600. I use a piece of plywood and aim at the top all the time. The point is to get a measurable amount of bullet drop at different yardages. Take that data and compare it to your ballistic calculator. Adjust your BC until it all fits. Then use that data and try and stretch it a little farther and see if it validates.


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[bboswell]

I would search for Bryan Litz's bc numbers on the 140 accubond, they will be better to go off of than noslers.

When I search for anything related to BC everything defaults to LR bullets, I don’t like the way those bullets at the distances intended for this rifle. I just want a good dependable bully capable of 500 and in kills out of a lite weight rifle.

[TX03RUBI]

What powder were you using, and what conditions? Some powders are EXTREMELY temp sensitive, and will have large velocity swings depending on temperature.

[TX03RUBI]

Gotta start somewhere. It’s all physics you have a mass and a velocity. You can adjust either one to get the drop data you need. I would start with the BC. You only checked it at 375 this isn’t far enough to give you good data. I would take the rifle as it sit, go shoot it out to at least 5-600. I use a piece of plywood and aim at the top all the time. The point is to get a measurable amount of bullet drop at different yardages. Take that data and compare it to your ballistic calculator. Adjust your BC until it all fits. Then use that data and try and stretch it a little farther and see if it validates.


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If he’s a full minute low of his dope at 375 he’s got other factors at play. Even a inaccurate BC won’t drop him that much. At PRC speeds the advertised BC should be slightly low if anything.

[bboswell]

What powder were you using, and what conditions? Some powders are EXTREMELY temp sensitive, and will have large velocity swings depending on temperature.

Vit N-165, all shooting has been at same location and weather was within a few degrees of the same.

[Radar]

Need to shoot another string of 5 again, verify all chrono data. You have a heck of a load with a SD of 2. Do you know what the mirage was doing at the 375 target? Was it horizontal or vertical?

I do not know what ballistic software you are using but try to use two different ones at the same time. Applied Ballistics and JBM are the two I use. G7 is a better choice to use in calculations. Altitude and humidity settings in your software, terrain your shooting in can make differences in charts. Verify your scope height with exact measurements, make sure your reticle is square with the rifle and not canted.

I have never seen any software produce exact numbers that did not need tweaking. Here is a good place to start:

https://appliedballisticsllc.com/education/

[trophy8]

I’m gonna say the BC is off. However, those speeds seem slow for a prc. If I recall, nosler BC isn’t as high as they claim. Check Bryan Litz numbers. You’re running the same set up I intend to. I’ll probably run a 140 Berger for targets. Those accubonds are lightning out of a gun barrel on critters.

[bboswell]

Need to shoot another string of 5 again, verify all chrono data. You have a heck of a load with a SD of 2. Do you know what the mirage was doing at the 375 target? Was it horizontal or vertical?



I do not know what ballistic software you are using but try to use two different ones at the same time. Applied Ballistics and JBM are the two I use. G7 is a better choice to use in calculations. Altitude and humidity settings in your software, terrain your shooting in can make differences in charts. Verify your scope height with exact measurements, make sure your reticle is square with the rifle and not canted.



I have never seen any software produce exact numbers that did not need tweaking. Here is a good place to start:



https://appliedballisticsllc.com/education/

Mirage was vertical, I had 8mph wind dang near perfectly in my face.

I thought G7 was better for really high BC bullets and G1 was better for std flat base bullets? Anyway I ran my info with G7 and it was off even more.

Have fresh loads, will confirm zero, then shoot a box to verify turrets and then de-shoot distance. U fortunately 400 is all I have available during deer season but that been enough to get real close on everything else I have done.

[etxccampbell]

Believe the bullet!!


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[meltingfeather]

ES of 4 looks a little fishy to me.
I’d verify the chrono readings

[bboswell]

ES of 4 looks a little fishy to me.
I’d verify the chrono readings

Every shot for the whole work up was chrono’d on the LabRadar, speeds have been consistent, I had several charges in the very low teens for SD and this one that was 6 on the first group, I went one size smaller on bushing and SD 4 was the result.

Doesn’t seem to be an outlier.