barrel attached chronographs

[geekeye]

So I'm pretty new to reloading, and I'm working up some california legal hunting loads for 350 legend. i have 150 grain and 180 grain solid copper projectiles (nominally 0.3565") but there is not a lot of published data to start from that isn't based on 0.355" jacketed. given the tighter fit, i wanted to be careful of over pressure, so i'm starting light, but because these are going to be for hunting, i am hoping to still get as much velocity as i can.

Getting to the point, I ordered a magnetospeed chrono that straps to the barrel for testing at the range, and I'm curious what this is going to do my groups. Will it affect group size, or just POI? Can I look for velocity nodes and measure groups at the same time, or do I need to only measure groups when the chrono isn't hanging off the barrel?

thanks in advance!

[Tommy Gun]

You can purchase or make off barrel mounts for it. Found something between $100 to $160 for a machined polished product. Or can go the way of a heavy metal base with a threaded bolt for adjustments and mounting bars, probably buy at HD or Lowes, for a crude mock up.

[curtnelson226]

I have the same chrono and the only thing that i had to worry about was the poi, which was minimal for me testing at 100 yds... less of a factor than lighting conditions and sensitivity settings. Good purchase for the price once its rolling you'll be happy with it

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[Dave626]

Wiser precision have the chrono mount. It works

[Revoman]

I've seen a lot of users with the little bendy 'spider' camera or phone mount. Like $30 or so.

[jwfire25]

If your firing loads to get chronograph data then focus on that and not POI changes or groups opening up. Shoot for groups without it and you'll be good to go. I know guys who's shoot their loads into a pile of dirt 15 yards away because their objective at that point is just to get data. Good luck. Obviously this applies if you attach the magnetospeed directly to the barrel.


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[ar15barrels]

So I'm pretty new to reloading, and I'm working up some california legal hunting loads for 350 legend. i have 150 grain and 180 grain solid copper projectiles (nominally 0.3565") but there is not a lot of published data to start from that isn't based on 0.355" jacketed. given the tighter fit, i wanted to be careful of over pressure, so i'm starting light, but because these are going to be for hunting, i am hoping to still get as much velocity as i can.

Getting to the point, I ordered a magnetospeed chrono that straps to the barrel for testing at the range, and I'm curious what this is going to do my groups. Will it affect group size, or just POI? Can I look for velocity nodes and measure groups at the same time, or do I need to only measure groups when the chrono isn't hanging off the barrel?

thanks in advance!

Don't shoot groups with the chronograph attached.
The weight added to the barrel changes the groups so unless you intend to keep the chronograph on the barrel all the time, do your load development with the gun configured how you intend to shoot it.
Do your load development separate from your velocity testing.
Put the chrono on the barrel just to check velocity.

If you want to check velocity WHILE testing loads, you need a chronograph that does not contact the barrel.