Don't rule out sub-optimal rifle powders

[mkl]

For those new reloaders having problems with accuracy with their rifles:

I decided to post this personal story in case it may help.

In the early 1960's I had a new 1964 Model 70 Winchester in .243 Win. My shooting buddy had a custom Mauser in .243 also. We did a lot of bench rest shooting at that time and I was having one heck of a time to get my new rifle to shoot better than 3-inch groups at 100 yards. Rodger's rifle would shoot half inch groups all day long. Both of us were handloading of course.

I had tried most the recommended powders in the loading books and still could not get my new rifle to shoot. I was using Sierra 75 grain hollow points as was he.

Back then one could buy Hodgen 4831 from a 100 pound barrel for around a dollar a pound, and I had a couple of pounds that one day I decided to use as "fouling shouts" before I started trying new powder/weight configurations in my .243. After all, that "junk/surplus" powder was the cheapest I had; might as well use it for fouling shots.

So that day at the range I had six or so of the 4831 fouling shots loaded before I tried once again another powder/weight to find an accurate load.

To my surprise, the "fouling shouts" grouped 1/2 inch at 100 yards. All my other trial loads grouped 2-4 inches as usual.

Now the old surplus 4831 was one of the last loads listed in my manuals at the time, but all of the wisdom then was the powder was much too slow for the .243 Win. Needless to say, from that time on, I have used 47.5 grains of Hodgen or IMR 4831 behind the 75 grain Sierra hollow point and it has accounted for many jack rabbits and coyotes.

Just for fun, I gave Roger 5 of my accurate loads (with the 4831) and he gave me 5 of his that shot 1/2 inch out of his gun. Both of us shot 3-inch groups with the others loads.

A practical lesson in barrel harmonics!

The point of all the above nostalgia is to suggest that if one is having problems getting accuracy with the "preferred" rifle powders, one may want to try something on the slower end of the normal scale. I know my Winchester model 70 was an exception to the general rule as to preferred powders, but if you are having trouble to get any of the "best" powders to give you the accuracy you feel your rifle is capable of, you may want to try a "sub-optimal" powder like the one I accidentally stumbled onto.

Hope the above may help some of the frustrated reloaders.

best wishes

 

[Unclenick]

Slower or faster may work, though you may not get as high a final velocity with either one.

What happens is that as burn rate goes up, peak acceleration occurs earlier in barrel time, giving the bullet more of its final velocity sooner. That means it gets down the rest of the tube earlier, shortening barrel time. Barrel time is what you need to tune to the rifle's muzzle motions to get the bullets out in one of its dispersion flat spots.

As an aside, it's generally better to foul with the powder you will shoot. Different fouling has different lubricity. A number of top shots have said that if they switch powders in mid-match, it takes about 10 rounds for the gun to settle again.

 

[mkl]

Unclenick wrote:

Barrel time is what you need to tune to the rifle's muzzle motions to get the bullets out in one of its dispersion flat spots.

This is what I was calling "barrel harmonics." I agree 100 percent.

Back in the 1960's we never heard that you should use the same powder for fouling shots as you use in your bench shot loads. All we heard then was that the first shot out of a clean barrel will not place the same as subsequent shots. Accurate shooting has come a long way since my example, and I would defer to Unclenicks advice but still advise trying sub-optimal powders if you are having little success with "recommended" powders.

He is also correct (as usual) about the final velocity. My 75 grain bullets are a couple of hundred fps slower than the "normal" powder loads. Coyotes didn't seem to be able to tell the difference however.

 

[Unclenick]

The reason I avoided the use of "harmonics" is they relate to vibrations at natural resonant frequencies. Varmint Al has, IIRC, 8 different modes of vibration that are possible in a barrel modeled. However, based on fairly sophisticated software analysis, he concluded the initial muzzle deflection is imparted primarily by recoil moments and pressure distortion of the barrel, and the barrel then is free to ring only after the bullet leaves.

The pressure wave Chris Long has focused on does start with chamber expansion as the bullet is driven into the barrel's throat, and its lumps can be seen in pressure traces. That is one form of ringing that precedes bullet exit and may have to synchronize with muzzle deflection for optimum group tightness, but I think the jury is still out on how certain that is. Varmint Al seemed to conclude they are too small to have significant effect.