YES! A chronograph is a very valuable tool. It can help accuracy in the sense that it can tell you how uniform the ballistics are. Most loads shoot better with a low ES and SD. Only way to find this out is to shoot the loads over a chronograph.
Well it depends on what you want to do.... ☺
I have a chronograph, and I use it all of the time with my son..., when we are working on modern ammunition intended for shooting at 1000 yards. They are a MUST for that type of shooting. In fact we are going out Columbus Day to do some of that, but that's a discussion for another forum....
As for the muzzleloader, it can answer some questions, but do you
"need" to know or are you just curious?
I write that because I harvested many deer before I got curious and tried out my loads with my Chrony. The groups were very good out to 100 yards (I'm normally about half that distance when I harvest a deer), I had learned how to ensure a good, consistent load with my measure, and my patched round ball was firm when loading. No worries.
So..., It might be good to satisfy my curiosity. It would be good to test a batch of powder IF I ordered in bulk, and wanted to double check that everything was consistent.
So in the end if you get a 50 yard grouping like this, just about a 1" group, this is very good for hunting ...,
This will also work at 50 yards, being about a 3" group...,
THIS is....not really good, needing improvement, in my book ...,
Now between the first and second targets above, if the first target's load gave you 1100 fps at 50 yards, and the second target gave you 900 fps at 50 yards, the deer would not know the difference.
Would increasing the velocity get you from the 2nd target to a target like the first? It might, but you could find out by simply increasing the powder in 10 grain increments and look for positive change, and never use a chronometer.
IF you had either of the first two targets at 50 yards, and then got the third example above when you moved to 100 yards..., you might have a velocity problem, but you also may have other problems. When I've seen folks with accuracy and grouping problems at 100 yards, and it was cured by upping the powder charge (so increasing the muzzle velocity), the bad target looked something like this ...,
Note how the left to right spread is only about 1.5 inches, BUT the vertical spread shows a drop of more than 4" compared to the center of the group on the first target. This probably means a velocity situation, while the third target above may be a velocity problem but also likely other problems too. I was able to correct myself when I got a target like the fourth one, by not only increasing the load about 10 grains, but also gently tapping the side of the powder measure to settle the charge, and then topping it off. I increased the charge AND learned how to pour a more consistent charge. Again no chronograph needed.
So unless you're dedicated to some long range shooting, or need it for a different shooting discipline, I'd find somebody who will allow you to chronograph your loads with his machine. I'd save my money and use it on powder and lead and practice.
LD
.54 Hawken Flintlock
