[Manitou]

I've been loading for 10 or 12 years, and have gotten much better accuracy with my handloads than any factory ammo. I've mostly loaded for rifles, with 6.5x55 ,30-06, .270, 30-30, and .22 Sav Hi Power, being some of the cartriges I've loaded. I've generally stayed with IMR powders, but have been branching out lately with some WIN 748, Win 231, and Clays(in .45 auto), , and most recently, some Reloader 22 (for the 6.5x55 again).

Now to my question;
If I use say, theoretically, 36 grains of IMR3031, and in another load for the same gun,use 44 grains of Reloader 22, and (just for the sake of this example) they give very similar velocity readings, wouldn't the group size be very similar, almost identical?
If you push exactly the same bullets down the same barrel, at the same speed, and all other factors remain the same with the exception of the powder type and amount (but remember, they give the same velocity), wouldn't they both perform the same?

What I'm trying to determine, is , if I should be going for higher and lower velocities (while remainig in the safe range) to attempt to tune my loads to a particular gun. Simply trying another brand of powder that gives a very similar velocity some how seems to be an execise in redundancy.

Now I know that burn rates affect pressure curves, and burn rate may be the missing link (at least to me) here. But I thought that I'd ask the learned members of this board to see if I'm the only one that thinks about stuff like this.
Manitou

[griz]

I suspect that it's more about matching the pressure curve to the gun than obtaining one particular velocity. As an example, most hi-vel 22 LR ammo attains similar velocities but a rifle may prefer one over the other buy a large margin.

[Manitou]

Then, would it be more advantageous to have the pressure peaking as the bullet leaves the barrel than somewhere more closer to the breech? (not that this would be easily discernable from powder burn rate charts). If this is true (and I don't doubt you) than twist rate, barrel length, and bore condition would play greater roles in what a rifle likes.

[Frohickey]

Wouldn't you also need to count the amount of powder that you are using in the 'accuracy' equation?

What I have read is that the higher accuracy loads are ones with powders that more fully utilizes the case capacity. Though, there is also a weight range that the barrel would like as well.

[HSMITH]

Consistency of where the barrel is in it's 'whip' or oscillation when the bullet leaves the barrel is where accuracy is born, THE major factor. Everything else is just a contributor, like smooth bore and all of that. You can have a rough bore shoot one hole groups for instance. If anyone thinks a barrel does not move drastically during the firing cycle tie a normal hunting rifle down tight and hold on to the front sight while it fires, obviously make sure you won't get shot or burnt by the blast etc, make sure you are safe. The barrel moves a LOT more than you think.

Getting the bullet to leave the barrel at exactly the same place in the 'whip' every time is a matter of getting everything else lined up, all or most of the small players must be on the team. Consistency is everything.

Burn rates, charge weights, primers and bullet weight drastically effect the frequency of barrel 'whip' and some combinations work while others don't. The only absolute is there isn't one. If you took 3 powders and drove the same bullet to the same speed with each you will have a measurable difference in accuracy and even point of impact. Yes, POI too. I have seen loads within 20 FPS of each other print a full 6 inches apart at 100 yards with the same bullet.

My observations have been made with hunting rifles, not heavy barreled types. Obviously the effects I have seen would be lowered by stiffening the barrel.

[Vern Humphrey]

Quote:
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Then, would it be more advantageous to have the pressure peaking as the bullet leaves the barrel than somewhere more closer to the breech?
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Pressure peaks before the bullet moves (or in some cases before it moves much.) Muzzle pressures are typically only between 5 and 10% of peak pressure.

To visualize this, imagine a Garand rifle with a gas port pressure of 48,000 lbs!;)

[Manitou]

Thanks for all of you replies, I knew that i'd get a lot of imformation that I wouldn't have thought about on my own. I guess it's back to trying lots of powders, as long as I am safe.

[Sunray]

You need to work up a load using the Reloader 22 based on what your manual says. Not the velocity or anything else.

[Manitou]

Yes, I'm going to try 44 grains of Reloader 22 with a 140 grain Sierra SPBT.
That's the starting load in the Speer Data in my One Book/ One Caliber load book for 6.5 x 55. Other manufacturers in the book (Nosler and Sierra) show this a s a mid range load.