chronograph readings 35 Rem

[Battis]

I bought a Caldwell chronograph and tested it with my 38/357 a few days ago. The chronograph won't connect to my tablet but the readout is pretty big and clear. The readings for the .38 and .357 were consistent, but not so much today with the Model 8 .35 Rem.
I loaded up ten rounds, each with 20.4 grs IMR 4227, 2 different bullet weights. The action worked perfectly with each shot, ejecting and picking up a new cartridge.
This is what I got:
158 gr (10 ft) The higher numbers are where they should be. I shot the first 5 in bright sunlight.
982
960
1708
982
1735
206 gr (under the shadow of the overhang)
2390
1666
1670
1681
1688
Maybe 10 shots isn't enough but at least I know it works. Would the sunlight cause the variation in the 1st five shots?

[Yodogsandman]

You don't mention whether you used the diffusers or not. Best to use them on sunny days. Not needed on cloudy days. If partly sunny, I always use the diffusers.

Check your manufacturers recommendations on distance from the chrony. Pistols are normally closer than for rifle shots.

My chronographs manufacturers recommend buying a bunch of .22 match ammo and shooting a few each time out to check the accuracy of the unit. .22 match ammo is supposed to be very consistent.

What does your chrony directions say?

[C. Latch]

How far from the screens was your muzzle?

I've had weird readings before when trying to shoot too close to the screens, so now I use a distance of 12-15' and just use math to correct that back to MV.

[Battis]

Directions say 10 - 15 ft. I was 10 ft. I used the sun shades, but now that I think about it, the afternoon sun came in at an angle. Either the readings for the 1st five shots were wrong or something went wrong during reloading. The readings for the heavier bullets were more consistent.

[Mk42gunner]

I've never used a Caldwell, but for my first chrony I found a few things that helped.

A good battery. I learned to keep a couple of new in the pack nine volt batteries in the case.

Secure the tripod the chrony is attached to. It is not fun to feel the trigger break as the wind gusts and you see your chronograph tipping, knowing there is not a darn thing you can do.

Diffusers help.

Too close and you can get readings from the expanding gas, even if you can't see it.

I had a milk carton of .22 Long Rifle that I always shot a few from one particular rifle to ensure the chronograph was seeing the projectile and make sure it was working. Unfortunately that ammo became corroded, so I have to open anther box the next time I want to check speeds.

Make sure you have your line of bore over the chrony or screens, not just your line of sight; otherwise you will be joining the "I shot my chronograph" club. I am not a member, yet.

It is best to shoot from a solid bench, less chance of flinching and joining the club.

I now do my load development for accuracy before I check velocity of my final load.

Robert

[Battis]

I took it to the range today and it works great. The sun was directly overhead, so the shades worked better than when the sun hit it at an angle. It even connected to my tablet. I think it picked up the speed of a swarm of NH black flies as they charged at me.


I bought a copy of The Great Remington 8 by John Henwood. I was surprised to read that he "specifically advises against shooting any Remington Model 8 or 81, even with factory ammunition." If you do shoot them, he says, keep the loads light. Well, yeah.
Anyways, a chronograph does make sense with these older rifles.