Help with velocity:

[Kosh65]

I was hopeful that someone could help calculate a pretty close velocity for my reload?
I know, I know. By a Magnetospeed! And I will one day. But for now…………..here is my load data and rifle info.
-Remington 700 with 24” Rock Creek, #3 contour, 1:8 twist 5R match barrel.
-Hornady case trimmed to 1.517”
-CCI BR-4
-31.5 gr. of Lever
-Sierra 123 gr. HPBT MK
-Seated 1.667” BTO
-Two thousandths neck tension.

I shot this load on Sunday morning and it grouped pretty well. All sob moa. Temperature was 70 degrees and low humidity. My elevation is approximately 775’.
Groups were 2.5” high @ 100 yards. I backed up to 200 yards to check drop and POI was only 1” lower. I guess that I expected more drop than that.
Thanks for any help. Brian

[riuma]

Knowing the weather and altitude and ballistic coefficient, get onto a free ballistic app (JB Ballistics?) and back feed your data punching in what you think are approximate velocities. Eventually a 100 -200 yard drop will match yours and you'll know the velocity.
Try it. It's not hard and it works. ~Riuma
(My guess is to Start with 2500 fps)

[VASCAR2]

Your velocity will be approximately 2625 FPS, BC .510 elevation 775’ ASL with scope 1.5” over bore I used a 225 yard zero and got approximately your results. A variation in the height of the scope could make the results different. This is using Hornady G1 Ballistic calculator. Rough estimate but seems plausible.

[Kosh65]

Thanks for the input. VASCAR2;That’s pretty close to what I was estimating, (2600-2650)

[Kosh65]

I finally broke down and bought a magnetospeed. Soon I’ll be able to answer all my own questions. NOT!!!

[kmon]

A chrono can give you a lot of information, now using that information can be a different story.

[Kosh65]

Well, I finally got time to shot my reloads with the new Magnetospeed today. 10 shot string average velocity of 2657fps with SD of 5.

-Hornady case
-CCI BR4
-123 Sierra MK HPBT
-31.5 LVR
-51 degrees

[VASCAR2]

I don’t feel to bad, my estimate was off 32 FPS, close enough for government work. I think the Magnettospeed chronograph produce reliable velocity readings and are pretty easy to use. A Friend has a Magnettospeed chronograph we used to chronograph 16”, 18”, 20” and 24” 6.5 Grendel AR-15’s. We got a five shot average of 2619 FPS out of his 24” AA 6.5 Grendel with 31.0 grains CFE223 and CCI 450 primers with 123 grain Nosler CC on a 70 degree day. I’ve seen extreme spreads greater than 32 FPS and I probably can’t shoot good enough to tell the difference in shot placement with 32 FPS velocity difference, lol. Your SD of 5 is really good and even though CFE223 and LeveRevolution are affected by temperature change I think their burn rate make them very good powders for the 6.5 Grendel.

[Kosh65]

I’m not so concerned with the temp sensitivity as some are. I built this rifle for hunting deer sized game and most all of my shooting (I do some shooting @ paper during the summer months) will be in the range of 20*f—-60*f.

I do shoot prairie dogs every summer. But I have a couple heavy built varmint rifles chambered in 22-250 and use Varget specifically for that as temps sometimes are in the 90’s.