I just tested 68 and 69 grains of RL-22 with a 180 gr Nosler BT in my H-S Precision, Pro-Hunter 300 WSM rifle which has a 26" barrel.

I had great accuracy success (.270" group, and no pressure signs) with 67 grains of RL-22 and wanted to see if I could up the velocity a touch with a bit more powder.

The velocity dropped by about 50 FPS with both of these heavier loads.

BTW the ambient temp was 20 degress hotter when I tested the heavier loads.

I�m going back to 67 grains but am curious about what you think may have happened.

TR

Maybe I missed something , accuracy is fine , then dont worry about velocity . You happen to own a hunting rifle , not a velocity chute . I would trade fps. for consistant point of impact anyday .

Trathner,
I have a .444 that gets 2380 f.p.s. with 47.0 grains of h-4198 and a 240 grain bullet, but when I went to 48.0 grains I lost almost 100 f.p.s.
The recoil was also much more noticeable. I think what happened is I went over pressure, for my gun even though there were no visible signs of this.
Maybe something like that is what happened to you.I'm sure somebody here will be able to tell us what happened.
fwiw, JT

Most accuracy loads are under max. I use max loads for hunting and therefore need the max energy that I can get. If you just think about the mechanics of the thing one can come to a reasonable explanation. Like the slower the bullets goes down the barrel, more it grips the rifling and the better twist rate results in better accuracy. Less recoil, the warmer temps, there's a lot that starts to figure in when trying to figure this out. Read your reloading manuals and I remember seeing an article in one of them that covered this issue.

CLL,

I am happy with the accuarcy and said I was going back to the accurate load. Im just curious if anyone knows why velocity would drop with a bit more powder.

TR

Okay lets put it this way, the bullet tears down the barrel with the hotter loads, and the bullet turns down the barrel with the slower loads giving better accuracy. That's the plainest way that I can explain it without getting into the books.

Robert,

What you say about accuracy makes perfect sense, but why would it be slower with more powder?

Todd

I will look in my reloading manuals and maybe call the guys at Sinclair who seem to know ALOT. But I thought it would be an interesting topic for discussion.

TR

Call the sierra guys, they've been really helpful with me. Let us know what you come up with. I really didn't mean to confuse you. Speer manual #13 page50 toutches on the subject a little. Don't know that it answers the why question though.

[ 05-13-2003, 06:24: Message edited by: Robert M Boren Sr ]

How many rounds did you fire for each load while checking velocity? What were your extreme velocity spreads and standard deviation for each load?

I fired about 5 3 shot groups of each load. Deviations were no more than 20- 30 fps. But I did not write down all. I just wrote down the average velocity for each load. Extreme spreads were probaly no more than 50 fps. But again, this is from memory. Should have kept the notes on velocity of each shot.

TR

Just a guess, but if your load actually overdrove the rifling, the bullet could be damaged to make a less effective gas seal, allowing more gas to pass teh bullet along hte sides.

Also, if your powder measure is like mine, occasionally a load is not what its supposed to be. and a little lighter load can cause slower velocity. I found a few out of ten loaded cartriges would be on the lighter side, balanced by a few on the heavier side, although the error is definitely not a bell shaped curve, since light loads can occur, but it is nigh impossible to have a load more dense than normal.

[ 05-13-2003, 09:40: Message edited by: Jameister ]

some powders, especially double base powders, will actually reduce pressure and burn rate as the available air space is reduced. The dangerous part of this is that the burning characteristics become unstable just beyond the "knee" of lowered pressure. Some powders will completely snuff the primer charge while others generate an uncharacteristic rise in pressure.

PaulS

A while back a guy (Ok Shooter) had some information on this on his website.
Many people savaged him, but he had the data. It seemed to be real.
All I know is that odd things happen around what the old timers called the "balance point".
Good luck!

just exactly why this happens, I am not too sure, but it is not too unusual.

I had a similar experience recently when trying the new Nosler Accubond bullets in my 300 Weatherby. I was using RL 25 and 83 grains gave a velocity of 3087 while a charge of 84 grains dropped to 3062 fps. (Fired the same day at the range.)

With some load combinations once you reach a certain charge level, there is nothing to be gained by adding more powder. This is one of the ways that owning a chronograph is worth every penny spent.

R F

If you were fireing a smoothe bore thie increase would change acordingly. But you're not you're shooting a grooved barreled gun. When that bullet reaches a certain point it begins to try and overcome the rifling. What you have then is an increase in friction, and hence the lower velocity however slight it is.

I would start looking at the ignition part. With more powder, ignition might shove more into the barrel after the bullet. This would reduce initial pressure, and thus result in a less complete combustion. In general, the pressure in the barrel is much lower than that in the chamber.

It would be an interesting test to put a few sheets on the ground in front of the barrel, and collect the kernels on the "heavy" and "light" loads for comparison? Also interesting might be going to a heavier primer. FWIW< Dutch.

This is a very common phenomonon.

As you increase powder charge, velocity increases, up to a point. Then you each increment of charge produces a smaller increment of velocity. As you increase even more, velocity decreases. Unfortuntely, pressure continues to increase, sharply.

When you are getting less and less increase in velocity as you increase charge, it is a good sign that you are at, or past maximum charge.

This is discussed in the Hornady manual, and was also discussed in one of the Sierra "technotes" or whatever they call them.

The thing that baffles me is: Why?

One other thing that you might want to check is how you're throwing the powder. Are you measureing every charge? I would try that while you're expierementing and see if you find some incomsistancies.

Accuracy has little to do with maximum or minimum charges, but rather the barrels harmonics, consistency of the charge to release the bullet at the right time, type of bullet, quality of the bullet etc. I have a number of loads that shot their best at maximum, and a number of loads that shot their best at the minimum charge weight. The common thread between the two is in that the bullet is released from the barrel at a �friendly� point in the barrels harmonics consistently and repeatedly, resulting in better groups.

Turok

For those who asked about the method of loading the charges in the cases, I am weigh every charge.

I know there is no set relationship between velocity and accuracy. Some shoot more accurately faster...some slower.