Lab Radar question

[Tank308]

2 weeks ago and now Today. My 338 NMI. 28". 300 gr Berger. ATACR 7x35.
Can the gases from my brake on my gun cause false readings. I've never had the fps be off by so much. Radar says 2803 avg. plugged it into StrelokPro. It says 8.9 moa to 500. The impacts were 5 inches low. When I went to 7.75. Perfect. Plugged into StrelokPro truing. It says 2955 fps. I ran my wsm both times and it's readings are good at 500. I have the radar set behind the break on the bench 12" so the gases don't rock it. I can't set it out front because the stand is elevated. I'm missing something.

 

[Bob Wright]

I move mine behind the brake about 12-18 inches. Never measured so guessing a bit. I get consistent readings.
On an optical chronograph, the blast and propellant debris would affect the readings a lot if not out about 15ft.
If you could shoot over another device, that might tell you something.
Edit to add:
Keep moving your device back towards you until it fails to trigger, it that can happen...
Then see if it makes any change.

 

[The Oregonian]

Mine is 6-12" behind the brake and maybe 2 ft to the side. I usually either get accurate results or no reading. This is shooting things from 6.5cr to 30N.

ETA - once a year or so I will get an obviously wrong velocity, like 1000 fps over what my rifles shoot.

 

[Tank308]

Ye

I move mine behind the brake about 12-18 inches. Never measured so guessing a bit. I get consistent readings.
On an optical chronograph, the blast and propellant debris would affect the readings a lot if not out about 15ft.
If you could shoot over another device, that might tell you something.
Edit to add:
Keep moving your device back towards you until it fails to trigger, it that can happen...
Then see if it makes any change.

I have several brakes I've tested with. But this is a Dragon. David Tubb brake. I Just thought 150 fps is a lot for a 300 gr Bullet.
I tried it 24" back and to the side. Straight back on both sides hugging the barrel.

 

[Mason Blackmon]

I got the air gun microphone for mine and that's what I use for a trigger and it's worked great on my bench. And I can put the LabRadar more places out of the way(limited bench space).

Have you tried putting a blast shield between the brake and the crono like the instructions suggest? I've seen that make a difference to some shooters on other forums

 

[Scott E Ames]

I elevate my LabRadar about 8-10 inches with a pipe clamp setup to grab the side of the concrete shooting benches at our club. I set this up about 12 inches to the side and this seems to catch all my 7 RM shots with a Lil' Bastard brake. You obviously have much more muzzle blast to deal with in a 338 NM. With the pipe clamps you can set the elevation by picking the pipe length to raise even more. I like hearing the airgun trigger lets you put the unit anywhere, sounds like that may be the best plan.

 

[cohunt]

Are all your other variables correct in streelok? "Scope height" , g7, weather data, shooting angle, etc? Do you have a "canted" pic rail?

 

[Tank308]

Are all your other variables correct in streelok? "Scope height" , g7, weather data, shooting angle, etc? Do you have a "canted" pic rail?

The 300 Berger is in StrelokPro library I used that data. Weather data I adjusted each weekend. Angle is correct. Yes it's canted 20moa. I read a thread that a hunter shooting 300 grain bergers at 2845 dialed 8.25 for a 623 yard shot with success. I interned that data in my StrelokPro and it said the comeups should be 12 moa. I'm going to look at another calculator.

 

[Roxie 10]

2 weeks ago and now Today. My 338 NMI. 28". 300 gr Berger. ATACR 7x35.
Can the gases from my brake on my gun cause false readings. I've never had the fps be off by so much. Radar says 2803 avg. plugged it into StrelokPro. It says 8.9 moa to 500. The impacts were 5 inches low. When I went to 7.75. Perfect. Plugged into StrelokPro truing. It says 2955 fps. I ran my wsm both times and it's readings are good at 500. I have the radar set behind the break on the bench 12" so the gases don't rock it. I can't set it out front because the stand is elevated. I'm missing something.

What powder are you using

 

[Tank308]

This was zeroed at 100 yards October 23. 70 degrees
This was yesterday 40 degrees. Both weekends I shot what StrelokPro said 8.75moa. Low both times. 7.75 moa right on both weekends. At 500.

 

[Korhil78]

In the calculator there is a measurement that you need to make for sight height. Measurement is from the middle of the scope objective to the middle barrel. Unless you have done that already. The above is in common terms. You can look up on the internet how it's actually measured to donit exactly right.

Although I doubt it's enough to change it 1 MOA.

 

[Tank308]

In the calculator there is a measurement that you need to make for sight height. Measurement is from the middle of the scope objective to the middle barrel. Unless you have done that already. The above is in common terms. You can look up on the internet how it's actually measured to donit exactly right.

Although I doubt it's enough to change it 1 MOA.

Thank you. Although my scope height was correct. On that screen the click values were .344 (mrad). Changed to .25 and now only 30 fps difference. I knew I was missing something

 

[Korhil78]

There ya go.

 

[BrentM]

Just get a recoil trigger and the bs is gone. I use my trigger exclusively and don't have to mess with placement issues or missed shots. Best thing for the lab imho.