I recently purchased a the Magnetospeed Sporter V2 to determine the muzzle velocity of the Hornady 168 grain A-Max Match product number #8096. According to the box, this round has a muzzle velocity of 2700 FPS. Hornady's web page documentation states that their muzzle velocities are calculated using a 24" test barrel.

Using the Magnetospeed, I received three sets of averages of 2326, 2318, and 2425 FPS. Averaging these three, I get 2356 FPS. Looks like I'm losing 344 FPS over what's stated on the box. If the test barrel is 24" and the barrel of the M&P 10 is 18" than I should lose 6" of muzzle pressure, correct? To calculate the muzzle velocity per inch, I divide 344 FPS by 6". If my calculations are correct, I’m losing 57 FPS lose per inch. Am I correct? This seem like too much muzzle velocity lost per inch to me.

I would like to know what FPS you guys are getting with this ammo. I'm not confident that the Magnetospeed is accurately reading the muzzle velocity because the Magnetospeed kept coming loose and displayed various error codes while trying to use it. I had to keep switching to different sensor sensitivities after every 4 or 5 shots. I wasted about 60 rounds just trying to get the three averages (7 shots per average)!

I can’t recommend the Magnetospeed Sporter V2, due to the difficulty of maintaining a tight connection between the barrel and mount on an AR type weapon.

Going off topic here, but I’m a left-handed shooter, and every fourth shell casing would hit me in the face. Is this normal for the M&P 10? The brass defector is already showing green primer, after only shooting 200 rounds of the Hornady 168 grain A-Max Match. I never had this problem shooting any of the PMC ammo? On the bright side, I'm shooting 3/4" MOA with this ammo.

Sorry that my post will not be helpful. I read that last sentence of your post and it makes me wonder if all the rest matters.

I wish you good luck!

The test does matter as I need an accurate muzzle velocity to calculate hold overs beyond 100 yards. I plan to shoot at ranges from 100 to 600 yards

Oehler 35P.
The best.

@OP,

I have a Magnetospeed Sporter that has proven to be very reliable for me. I use it with my F class rifles and load development. I am on the other end, using a 26" barrel, and looking to develop less than 1 MOA loads for 600 yards and 1000 yards. I have never had it come off due to muzzle blast, and I have gotten error codes when it was set for an ultra sensitive setting. My midrange rifle is an AR platform.

For your 3 sets of data, were all of the cartridges from the same lot? Were any of the cartridges left in the sun?

I use my chronograph data with Sierra Infinity. I would use your middle average to get your adjustments. Remember, your program will recommend changes, which should put you on paper, and that is the best you can rely on. Once you fire the distance to find your settings, THAT is the setting that you retain. This is one of the main reasons that you want to keep a book.

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Judge control not gun control!

You said it!!!!.....Mine's over 25 yrs old and still going strong.....Love the proof channel..........

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S&W Accumulator

Your findings seem perfectly in line to me.

All data was obtained using cartridges from the same lot. The cartridges were not in the sun.

OP- You will see that kind of difference in MV based on the barrel lengths. I've researched it quite a bit. Not uncommon to see between 25 -50 FPS per inch difference.


I own the MS Sporter, and it is giving you accurate readings, as far as I can see in your posts. Your diminished MV from Box MV is due to your shorter barrel length. Most Box ammo MVs are derived from 24 inch test barrels.

I own a Rock River Arms 6.5CM with 20" barrel and my MVs are less than posted on the box. (which is why I started searching around about this)

PS: I also own a 6.5 CM w/24" bbl and subsequently got a LabRadar. And can testify that the MVs on Box ammo are not always accurate. Overall I am finding them to be somewhat under the posted MV. FWIW.