Help with 50 BMG velocity

[bellavite1]

So I just got back into 50 BMG.
I got me a Barrett 99, 32" heavy barrel.
I will be shooting only two loads out of it, both factory:
Hornady A-Max 750 gr (hornady website lists 2820 fps out of a 36" test barrel) for "accuracy".
PMC Bronze 660 gr (PMC website lists 3080 fps out of a 36" test barrel) for fun.
Both velocities seem grossly overstated:
I use the Shooter App on my phone which has a "velocity calibration feature, where you input actual correction at different distances and it extrapolates actual velocity.
According to that, PMC is flying at 2720 fps, loosing 360 fps in 4" of barrel.
Sounds like A LOT!
Finding that out costed me 20 rounds, about $70...
The 100 yds zero is (thank God) identical.
I need to find out the actual velocity of both rounds out of my rifle, but I do not own a chronograph and I am not sure of how to use one to prevent the muzzle blast from giving me false readings.
Is there a kind soul that can help?

[00tec]

You can set the chrono several feet out and shoot over it.

[bellavite1]

You can set the chrono several feet out and shoot over it.

I was hoping to meet up with one of my fellow members ( maybe someone who is also a member at BLGC) that has a chronograph and the knowledge to shoot a few rounds to test thing out.
I will supply the rifle and the ammo...

[O2HeN2]

For a couple of pops I'm willing to volunteer my LabRadar!

Never used it for rifle, only pistol so it'll be something new.

The downside is that it's quite a drive for you.

Pm me if you're interested.

O2

Frontier Sportsman's club, Hanover range

[buffalobo]

For a couple of pops I'm willing to volunteer my LabRadar!

Never used it for rifle, only pistol so it'll be something new.

The downside is that it's quite a drive for you.

Pm me if you're interested.

O2

Frontier Sportsman's club, Hanover range

Do not hesitate, take him up on this.

It will be worth the drive.

If I could justify membership for two trips a year I would be a member.

[bellavite1]

For a couple of pops I'm willing to volunteer my LabRadar!

Never used it for rifle, only pistol so it'll be something new.

The downside is that it's quite a drive for you.

Pm me if you're interested.

O2

Frontier Sportsman's club, Hanover range

It sounds great!
I just saw a video about it.
We may have to find a way to secure your radar to the bench since the muzzle blast is quite intense and pretty much blows off anything that is not nailed down...
I sent you a PM

[O2HeN2]

We may have to find a way to secure your radar to the bench since the muzzle blast is quite intense and pretty much blows off anything that is not nailed down...

Muzzle position

We'll probably position the muzzle well forward of the unit.

I'll see if anyone in nfatalk.org has any sage advice, too.

O2

[zimagold]

Use adjacent bench for LabRadar. Set to max offset in software. Ditch the tripod and use sandbags. Caldwell Tack Drivers stood on end with the LabRadar wedge between work great for high muzzle blast. External accelerometer trigger. Don't forget your external battery pack.

Edit: Bring the tripod. Always bring all the things when trying to get one shot sets of data. If you go the sandbag approach, tether the LabRadar so it doesn't fall off the bench when adjusting. Been a few years since I tested an M82a1 for a friend.

[bellavite1]

This is what we'll contend with...
https://youtu.be/p-FzqyqXTDw

[O2HeN2]

That's the muzzle brake you've got? I'm thinking putting the lab radar forward and well off to the side and see if we can find a sweet spot between the side blast and the muzzle blast.

O2

On edit: should have just looked up the 99. Yhea, that's the muzzle brake you've got