Is my chronograph lying?

[schmidtzen]

I took my shooting crony* to the range and got 1425+ fps 40-70ss 63 gns 1.5f OE powder 410 PJ creedmoor. I later shot my 22 lowall using Eley Match 22lr the ammo box says 1050 fps. The crony was reading 1250 average fps. Whats up? Tommy

[powderburnt]

Possibly the muzzle blast is reaching the screens before the bullet. To avoid erronius readings you will need to cut a hole to shoot through in heavy cardboard or plywood to block the muzzle blast from passing through the screens. Also, you should be mindful of card wads hitting your chrony when shooting your BP loads through it.

HG

[schmidtzen]

It just seems to me like its reading 200 fps faster than it should.

[Lumpy Grits]

When was the last time you installed fresh batteries?
Gary

[schmidtzen]

Fresh 9V battery. It (chronograph) had not been used for 15 yrs or so. Could be operator error

[Gamerancher]

Just move it further away from your muzzle. Mine worked best about 6 yards from the muzzle. That load in my Shiloh .40-70SS runs around 1230 f/s.

[Lumpy Grits]

How close is the screen to the muzzle?
Gary

[schmidtzen]

I had it 6 feet away from my 40 cal muzzle. My .22 it was about 2 feet

[Lumpy Grits]

You may have to place a old sheet before the crono to help stop debris from the muzzle causing false readings.
Gary

[Aviator]

Take a look in the instruction manual for your Shooting Chrony.
You will probably find that that they recommend a greater distance from the muzzle, to avoid erratic performance due to muzzle blast.

[schmidtzen]

Thanks I'll give it a try