I have reloaded for a while now but recently purchased the garmin chronograph.

I loaded 150g eldx for my 280ai. I used load data out of my Nosler reloading manual. I started with 55.0g of 7828ssc and increased in .5g increments to 57.0 g. Attached is the data.

Using the data in the pic how you use the data to develope a final load? I chose 56.0g because a decent SD even though the muzzle velocity isn't as fast as I thought it should be.

There's no point in selecting a low ES, SD load if it didn't shoot good. How'd it shoot?

^^This

Look at the groups before you start worrying about the Chronograph.

I was shooting steel at 300 yards and and didn't measure groups but I was able to group them around the plate. Couldn't tell a big difference between groups.

I stopped using a chronograph because it was more of a hassle keeping it aligned properly and getting to read consistently. I just shot groups to find something that shot well and then measured dope out to 600 and back calculated my muzzle velocity.

The Garmin chronograph was super easy to set up and use but sounds like my new toy isn't actually that valuable.

So after finding a group that shoots well how would you use chronograph data?

It’s a great tool, but accuracy at range trumps es and sd when they’re as close as the ones you’ve listed.

You simply cannot rely on measured velocities to develop an accurate load. Low ESs and SDs just won't guarantee consistent POIs. You might eliminate bad loads for long range use based on higher ESs and SDs, but that's as far as it will go. Your best use for a chronograph is to measure velocities for the sake of safety and that's because the best pressure indicator you have short of actually measuring pressure is the velocity itself. Traditional pressure signs like hard bolt lift, ejector marks, flattened primers, etc. and etc. can be very misleading. Velocity is a much more reliable way to go about it.

And to add to this.

When you add powder, but do not gain velocity, you need to stop adding powder.


I have done lots and lots of very successful load developments and did not chronograph a single shot. I found tight shooting, guessed at velocity based on experience from previous rifles, and then headed down the range with it. If the bullet is inpacing high at 500 yards, I go into the ballistic calculator and increase the velocity I plugged in. Then shoot 600 yards. Keep tweaking that plugged in velocity until everything matches up. By 800 yards, I know the muzzle velocity.

First, my LabRadar chrono is absolutely my most valuable tool when testing ammunition. But I use it in conjunction with what the groups are telling me. I can shoot a load that have very good low ES and SD numbers, but it's out of the accuracy node and doesn't shoot good. So, only going by how low your ES and SD is, isn't the "final" answer. BUT... generally speaking, the accuracy node that shoots the best (or very good), also has a low ES and low SD.

Second, accuracy trumps all. I want a good shooting load first. The chrono just tells me what my speed is. I MUST know this.

I ran the LabRadar and the Garmin side by side last night, and the Garmin and LR were within a few fps each time. The Garmin was a few fps faster than the LR was on each shot, but it was consistent each time. I was testing and working up my new 30-06 subsonic rounds, which performed perfectly. I was testing the 190 SUB-X and 220 RN bullets. I couldn't do this testing without the chrono.