I am sure anyone that has reloaded has noticed that the manuals consistantly use different barrel lengths when calibers of the same bore size. I'll pick on Nosler since I use thier manual most & that is what is in front of me at the moment. Case in point 7x57 22" barrel, 7mm-08 26"barrel,284 Win 24" barrel,280 Rem 26", 280 IMP 24", 7mm SAUM 24". This is done with the 6.5 mm calibers also. I would really like to see data useing the same barrel length to get better comparisons. How about you?

It doesn't matter to me, differences between barrels of of the same lengths and mmanufacturers will vary velocity as much as the length will.

I have two 223s with identical barrels bought from the same manufacturer, at the same time that differ by almost 200 fps with identical loads.

I rely more on a chronograph to give me the speeds of my bullets, than a reference manual..

some calibers especially like the 7 x 57 and 6.5 x 55 are all over the map...

reference manuals are just that.. reference...
not bibles..

Seafire, I was wondering what is the average variation of muzzle velocity from what the reference manual says?

Thanks,

Jim

Most of the SAAMI test barrels use tighter tolerances for the bore and chamber than production barrels meaning they usually produce higher velocities.

quote:

Originally posted by Fjold:
It doesn't matter to me, differences between barrels of of the same lengths and mmanufacturers will vary velocity as much as the length will.

I have two 223s with identical barrels bought from the same manufacturer, at the same time that differ by almost 200 fps with identical loads.

I agree. Sometimes a chrony can reveal some pretty incredible stuff.

Every rifle is an individual. Which is why there is no such thing as an "average" deviation. You can get an average idea of what X or Y caliber should be capable of, and many manuals are pretty good for that. But there are no garantees at all.

quote:

Originally posted by Singleshot03:
Seafire, I was wondering what is the average variation of muzzle velocity from what the reference manual says?

Thanks,

Jim

In my experience it can vary from virtually nill to all over the map...

some manufacturers have admitted that their chronographs were off a lot... some folks find velocities listed in some Manufacturers manuals to be optimistic to overly-optimistic.

I've had loads in rifles blowing primers with one or two different loads that were several grains BELOW recommended starting point, yet in the same page, give other loads that the rifle barrel was getting blow back ( not enough pressure...cases smeared with soot after firing) on max on other loads...

I chalked it up to poor load techniques and notes when the manufacturer was testing...

I've seen all sorts of oddball anomalys with handloading, so that is why I rely more on my chronograph than anything else...