How accurate are reloading guides velocity ratings?

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cath8r

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I know alot of diferent factors go into how fast a load will be and that every rifle is an individual..... but..... have any of you all actually compared chrono readings against what the reloading manual said would be the velocity? What were your findings? Close, far off?
Thanks, rob.
 
With rifle I find my chrono readings for the same load are in the 50-150FPS +- range depending on load:rarely am I less than 30 fps off.

If my difference is substantially greater say 300fps for example then I would certainly review my load as that would be a significant diffference and a clear indicator that something is "not quite right" for sure.

Regards,
 
I usually check to see what their loads are fired through. I tend to find mine depending on the book a little higher for the most part.

I don't tend to use them as any reference when loading though and chrony all new loads myself.
 
Thanks guys. I'm working up loads for a new rifle and just want to see what my accurate loads are going to be in the ballpark with. I don't have a rifle chrono right now, just want to see roughly where the trajectory would be on the Hornaday Ballistic calculator. Will try to chrono officially once I get a real accurate load and see for myslf how close it lines up. So far the load that seems to work for now is a 75gr Amax out of a 22-250 running 3100fps according to the book. Will see how accuracy is at 200 yards with fine tuning and then run it through a chrono to make a drop chart. Running sub moa thus far...
 
I buy barrels several at a time from the abrrel maker. They get chambered with the same reamer. Side by side they need difffernt loads and with the same ammo are 100+ fps apart.

The lab's rifle is different than yours. The velocity will be different, but within 200 fps.
 
A rough bored, sloppy chambered rifle might not get within 150 of "the book". A tight chambered match barrel may beat it by 150 or so. Added together there can be more variation between barrels than between cartridges.
 
The only way to determine the velocity of a given load in your firearm, is to actually chronograph that load in your firearm. Anything else is just a guess. It might be very close, or it might be 150fps or more off.
 
+1 to whateveryone else has said about a chrony being the only reliable way to know for sure.

As a general rule, to come up with a half decent estimate, is to check what the test gun was, as ceriksson has suggested, and then compare it to what you are shooting it through.

For example, if the test gun has a 24" barrel, and you are using a 26" barrel, then using 25-40 FPS per inch as a rule of thumb, you could expect to be around 50-80 FPS faster, just on account of barrel length.

You can generally assume that the big manufacturers put alot of rounds through their test equipment, but keep it in good working order.

So if you gun is new, I'd expect maybe another 50 FPSish. If you gun is really old abused, maybe subject 50-100 fps ish.

The rest of the variation will be on account of stuff you can't really know, like temperature/pressure conditions during test fire vs what you will be doing on the range. When the respective firearms were last cleaned, and how well they were cleaned.

as boomer686 has suggested, if you are ever more than 300 FPS off, or even only 200 fps higher than where you think you should be based on book value, then I'd really scratch my head and try and figure out why before I continued shooting that load.
 
The rest of the variation will be on account of stuff you can't really know, like temperature/pressure conditions during test fire vs what you will be doing on the range. When the respective firearms were last cleaned, and how well they were cleaned.
Click to expand...

Actually, in most cases, the biggest factors will be the chamber/barrel dimensions, and the lot to lot variations in components.
 
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