Now that I have a chronograph and am able to do lots of interesting little tests with my loads, there is something that is nagging at the back of my brain. My question is this. Are the loads shown in the various reloading manuals considered to me a maximum based on a specific powder charge or a specific velocity?

Here is a "for instance" to illustrate my question. Various reloading manuals show a maximum load for the 243 Winchester using Reloader 22 and a 100 grain bullet as being between 41.7 grains and 45.5 grains for a velocity spread between 2950 fps and 3076 fps. The different manuals use varying bullets, cases, and barrel lengths which really muddy the waters. In the past my conservative approach has been to check out all the available sources and use the most conservative reference as a maximum load. Now that I have a chronograph and have started checking the velocity of my particular loads in my rifles, the result has been that for this particular rifle in this particular caliber my velocity is well below the maximum velocity shown in any of the reloading manuals. The actual result is this:
Fire formed Winchester Brass
Federal 210 Match Primers
95 grain Berger VLD bullet seated 0.030" shorter than touching the lands with light neck tension.
42.0 grains of Reloader 22
Remington 700 rifle with 24" barrel
Approx. 2830 fps measured at 8 ft from the barrel with a velocity spread of 9 fps for 10 shots.
No pressure signs with rifle or load.
Altitude 670 ft above sea level
Temperature 55-60 deg. F.
Humidity - low
Wind gusting 5-10 mph.

I have read that different lots of brass will have different capacitity and different powder lots will have varying burning rates not to mention that different barrels will give varying velocities shooting the same load.
This is why I am wondering if I should be loading to reach a specific velocity rather than using a specific powder charge weight as the maximum load. The question never entered my mind before getting a chronograph.

Bruce,

You are going to get into a few head scratching occasions now that you have a chronograph.

You are going to find that each rifle has its own maximum charge and velocity.

You are going to get a specific increase for each grain of powder as you go up. And then you will find a load that might actually give you LESS velocity with a higher charge!?

You might have two identical rifles, one might give you 200 fps higher velocity than the other.

What I suggest is you strive for good accuracy with good velocity.

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saeed@ emirates.net.ae

www.accuratereloading.com

My answer is that a load is maximum based upon the powder charge, not the velocity. You may be able to better the velocity of a listed "book maximum" load by changing the powder charge, but you MIGHT have to change the type of powder also, in order to obtain a SAFE increase in velocity with a given bullet. Generally, slower powders give higher speeds at safe pressures, OR adequate speeds at lower pressures, IF your case will hold enough of that type of powder.

As Saeed said, "You are going to find that each rifle has its own maximum charge and velocity"!!! One of the reasons for the difference between what a book says is a maximum load and what your rifle will do is that data in many loading manuals was derived using pressure guns. These tend to have minimum chambers, and will reach a maximum allowable pressures with less of a specific powder,producing lower speeds, than a rifle with the larger, less well-machined chamber typical of production guns. So, in your gun, a maximum load may be more, or may be less, than a book maximum. The only way you'll know is by developing individualized ammo for your gun. Book data gives us a starting point, from which one MAY be able to go up, or perhaps have to go DOWN!! Remember accuracy is more important than the last one or two hundred feet per second of velocity!!

My load development will presumably not change. What I still intend to do is to load up 5 shots at each 1/2 grain incriment and shoot for group at 200 yards in order to determine the rifle's sweet spot then fine tune things in 1/10 grain incriments within the most accurate area. That methid will not change. All I am looking for at this point is to find out if the chronograph velocity is a more reliable method for determining chamber pressure than the widely varying maximum loads shown in reloading manuals so that I can reliably decide on a maximum load while testing for accuracy.

Well, neither, actually. I know, you just love that answer. Let me explain.

Most manuals show the max loads as the highest pressures they feel comfortable reporting, or the maximum charge the case will hold with a bullet seated. Velocity is simply a result of the pressures achieved, and the charge is simply a result of the case capacity or pressure maximum, whichever is reached first.
While I don't advocate loading to book max loads, some rifles shoot best at or near max. A chronograph can be a cruel mistress, however. Your rifle may never reach book velocities or they may exceed the book easily, depending on your particular components. A good level of experience and common sense will teach you when to cut back and when to proceed- but only your rifle will tell you that.
Watch for brass expansion, flattened primers, etc... as usual. Also, in my experience, .1 grain increments in charge weights never really has done much for my accuracy levels. Bullet seating depth, correct powder, good brass prep, and good technique has always made much more difference in my rifles.- Sheister

Within some reason, higher pressures will equal higher velocities. Barrel throats, seating depths, etc. can change both pressure and velocities; up or down. Since you have a chrono, if you are approaching a max velocity for a specific bullet/primer/powder combo as listed in a respected loading manual, you are courting the devil if you go beyond that velocity. That being said, if you are not getting the velocities listed in said manual(s) with the max powder charge, do not go beyond that powder charge.....or at least monitor yourself VERY CAREFULLY if you choose to forge onward. Good luck. Gary.