Spike Camp

Actual Muzzle Velocity

Actual Muzzle Velocity
« on: April 23, 2009, 02:33:04 PM »
I've been using my chronograph about 15 to 20 feet from my muzzle.  My .300 Wby averages about 3,200 FPS at this distance.  Does anyone have any idea what the actual muzzle velocity would be?  I've been leary of firing the rifle right next to the chrony.

Thanks
BPH

Oregon Jim

Re: Actual Muzzle Velocity
« Reply #1 on: April 24, 2009, 07:14:37 AM »
If you are getting reasonably constant readings I would suggest that you accept your readings as accurate for a couple of reasons. First, a chronograph too close to your rifle will be less accurate because of the muzzle blast. If the chronograph is detecting the blast it will indicate a large swing in your bullet velocity from shot to shot. I do not know if the blast will hurt your chronograph, but I think you are just fine where your chronograph is, if it is giving consistant readings. Second, even if there is a few feet per second difference in bullet velocity in 10-30 feet distance from the barrel, that difference is really insignificant in the real world except when shooting at extreme distance. And lastly, I believe that identical bullets fired from different rifles will have different velocities, so there is no "true velocity" for any bullet. There are too many variables. If you doubt the accuracy of your instrument, could you test yours against someone else's chronograph?

Re: Actual Muzzle Velocity
« Reply #2 on: April 24, 2009, 01:13:28 PM »
I'm simply curious about how much velocity is lost in that 20 foot span.  I know it's insignificant, but a bullet is at it's fastest the moment it exits the bore and decreases in velocity at an increasing rate over distance.  I have no problem with my chrony.  Just curious.

BPH
BPH

dubyam

  • *****
  • 4925
    • View Profile
Re: Actual Muzzle Velocity
« Reply #3 on: April 26, 2009, 10:07:57 PM »
Well, the technical and absolutely correct answer is that it depends on what bullet you're shooting (both weight and style).  I suspect, at 3200fps, you're shooting 180gr bullets, as that's about what I'd expect from them.  Using the 180gr Hornady Spitzer commonly available in factory ammo, you're probably getting about 3250fps of real muzzle velocity.  If you're shooting something like a 180gr Remington Core-Lokt, you're about the same.  If you've got some 180gr Nosler Accubonds, then you'd be looking at about 3240, which is, as you suggest, negligible in difference versus the others.  It's also pretty moot considering the 3200fps you're getting at the chrony.

You can use any ballistic calculator to 'back-figure' the true muzzle velocity by measuring the velocity at 20 feet and setting it up to match that in the ballistic calculator.
I believe this is a practical world, and in it I can count only on what I can earn.  Therefore I believe in work, hard work. - The Auburn Creed
The older I get, the less stock I place in what men say, and the more I place in what men do. - Andrew Carnegie

Re: Actual Muzzle Velocity
« Reply #4 on: April 27, 2009, 02:01:34 PM »
I'm shooting a 185 Berger VLD.
BPH

Re: Actual Muzzle Velocity
« Reply #5 on: April 27, 2009, 02:17:53 PM »
According to a couple of the ballistic calculators I looked at, my setup would slow down by about 10 fps at 5 yds and 18-24 fps by 10 yds.
BPH