newbie chronograph question

[gspgundog]

Finally got a day where I could go out and test some loads and boolits that I have been cooking up. Never used a chronograph before but by reading the directions and making sure I did not hit the screens I was able to get readings on all my test loads. In one of my loads I used 5.0 Gr of Bullseye pushing a 451 185 gr SWC through a 1911. I got readings of 804 - 905 - 891 - 877 - 903 FPS. Each load was weighed before charging the case. My question is this what kind of variation in normal from round to round when using a chronograph? At what point do you say something is wrong and disregard the data?

Thank you

[Artful]

That's an extreme spread of 101 fps - but the first shot from a cold barrel may throw off a string in my experience - you may have oil from cleaning the barrel and cold barrel won't be expanded like a warmed up barrel. If you throw out the first shot your extreme spread is only 28 fps. The other thing is the first round was loaded by hand the others by self-loading action of the gun. Did you tip the barrel up or down before presenting the muzzle to the target and shooting?

The other thing is on my chrony - if your not sending the boolits on the same path it can make a difference in the FPS it reads - take a 22LR and experiment a little and you'll see what I mean.

[fishnbob]

I agree with Artful, I get a lot of difference on handgun velocity because I shoot offhand almost exclusively. On some of the big bore hand guns, I use sandbags and the fps is noticeably more consistent from offhand. Also I think the crimp makes a difference. If I want really good data, I sort brass by headstamp and trim the brass for exact length which controls amount of crimp. I have shot through the chrony off center enough to get an ERROR reading.

[gspgundog]

Thank you gentlemen it gives me a few things to check out next time I go out.

[williamwaco]

Your readings are actually quite good.

You just need a little more experience to build confidence.

[Artful]

The other thing I have learned - how does it group? Doesn't matter what the Chrony says if you and the gun put them all in the X ring ;)

[country gent]

Try using a pellet gun and the same batch of pellets at the start of each session a good single cocking air rifle is very consistent velocity and will prove out you set-up and accuacy each time.A 5-10 shot string over it at the start test loads and another 4-10 shot string to prove nothing has changed. Just what I do. 1000 pellets last a log time like this.

[Artful]

The other thing is shoot some factory to see how it does - might surprise ya.

[williamwaco]

Try using a pellet gun and the same batch of pellets at the start of each session a good single cocking air rifle is very consistent velocity and will prove out you set-up and accuacy each time.A 5-10 shot string over it at the start test loads and another 4-10 shot string to prove nothing has changed. Just what I do. 1000 pellets last a log time like this.

Try some .22LR it is usually very consistent.

[gspgundog]

Thank you all for your input, you have given me a lot to think about (do) to learn how to use a chrony better. I can do the pellet gun test in the back yard and the .22 idea is a lot cheaper (purchased before the great mindless ness) then factory .45 but requires a trip to the club but still a great idea. I also like the idea of testing rounds for how they group first then worrying about the FPS.
Again thank you

[Artful]

Your welcome - I loaded for many years - my first experience with chronographing ammo was for competition (major power factor) - only reason I bought my own was needed for subsonic load development - it has come in useful for long range ammo development as well.

[country gent]

I use the pellet gun at the start and end of every session to verify the set up is good and reading consistent and at the end to verify it hasnt changed. Once you have the numbers write them down and if they vary but too much from sesio to session you know something is changed or not right.

[OuchHot!]

Artful covered the ground really well. All that I can add is a cautionary tale....I was a world class reloader until some nitwit loaned me a chronograph. I had a number of quite accurate loads that had very worry some extreme spreads. Comparing to spring piston airguns or .22 rimfire is usually a good check for consistency. With the auto pistol, you want to be cautious should you see extreme high vel. That can mean that the boolit is being deep seated on loading.