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Discussion Starter #1
The situation:

A. You are reloading and your reloading manual shows that the load to be the anticipated most accurate load for your bullet (say 175 grain SP) is at 30 grains of powder A at a velocity of 2500 fps; and you do not hold that powder. Assuming casing, primer, etc are the same in all the scenarios.

B. The manual shows Powder B at a load of 35 grains will give the same estimated velocity; and you have Powder B.

C. The manual shows Powder C at load of 34 grains will give the same estimated velocity; and you have Powder C.

Questions: Could you expect the same degree of accuracy from the Powders B and C at the 2500fps loads that you are getting from Powder A?


Recap Summary:
Powder A with 30 grains @ 2500 fps = accurate load
Powder B with 35 grains @ 2500 fps = same result accurate load?
Powder B with 35 grains @ 2500 fps = same result accurate load?

If the same design and weight bullet is loaded to the same velocity in three different powders shouldn’t the accuracy be similar? Or do powder burn rates, structure, and case capacity used, affect the accuracy that much?

CJ
 

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Reads like it would...but never seems to work out that way: (I have a good friend, has been a hand-loader for a very very long time) and he swears by it. Me, not so much. Every one of the manuals always list: their bullet, their primers, some times their brass, and powder, and, are always shot useing their test gun/barreled action. Some times, its not even close to published velocity...so how can that be? Another thing...notice how one book is always higher or lower for the maximum load (even their own, one edition to the next) than the others! It's a guide/starting point and nothing more!
 

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Depends on the cartridge you are loading for, and the burn rate of the various powders. I don't think there is a single, standard, patented answer to your question.

Some cartridges do better with the slower burning powders, some do better with powders that are on the quicker end of the spectrum (for that specific cartridge). Not to mention that each rifle is a rule unto itself. As an example, I have a few .30-06's and if I look at a specific bullet weight for that cartridge - - say 180's for now, one rifle does the best with H414, the other two show the best accuracy burning IMR-4350. In all of those instances, the velocity is plus or minus 75 fps or so.

Sierra manuals (at least, the one that I have) show "hunting loads" and "accuracy loads" and how they make a specific determination is likely based on their test barrels, however, we don't have access to those barrels. We may choose to use those guidelines, and hopefully, get lucky in finding an accurate load, at a velocity level that we are trying to acheive. Like 1 big hole said... "Sometimes, its not even close..."
 

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No.

The problem is variation in powder burning rates, which moves peak pressure around in the barrel, which in turn effects pressure behind the bullet at muzzle release.

In other words, if I have 30 grains of IMR 3031 that produces 2400 fps with a 163 grain bullet the .324 Biku Whale-Killer Express, muzzle pressure will be LOWER than using any amount of IMR 4350 (a much slower-burning powder) that produces 2400 fps with the same bullet as this load will exhibit peak pressure inside the barrel MUCH closer to the muzzle than does the faster-burning 3031. Remember that a rifled barrel vibrates like a violin string upon firing, and small differences in muzzle release pressure can make substantial differences in accuracy.

Make sense?
 

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Your answers are here but I'll go just a bit further into the barrel issue. Barrel thickness and weight help reduce vibration and help increase accuracy. (Ever notice most bench-rest rifles are heavy barreled? Barrel length makes a big difference in velocity. Barrel rifling makes a big difference in accuracy with regards to bullet weight, material and velocity.

Also, believe it or not, your type of action can make a difference. You should see my full auto throw 55gr fmj factory loads sideways through paper targets. (This isn't necessarily an accuracy issue it's just that the bullet is no longer pointed perpendicular to the target by the time it reaches it. This is at about 75 yards.) You can imagine how that might affect velocity. ;D ;D ;D
 

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OR... just is...

The one thing that can hold true is that a particular bullet may have a velocity range it prefers for best accuracy with it. But that doesn't mean that it will be accurate at that preferred velocity regardless of powder used to get it there...
 

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One thing that SHOULD be the same if velocity is very similar is point of impact, however, the group sizes will likely be measurably different.
 

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In my experience, any effort to predict anything at all from a load change is doomed. IME, even the point of impact from same speed loads will likely be different because of the different barrel vibrations involved.
 

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Discussion Starter #10
Good feedback from everyone. ;) Boils down to there is no easy answer is there? :( ;D

CJ
 

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Even if you could remove ALL the other variables, changes in barrel harmonics alone would probably be enough to skew your results. I start out by trying to find a bullet the gun shoots well, then adjusting velocity and seating depth until it tells me to stop. I'm also a big fan of near-100% load density for ballistic uniformity. 8)
 

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Discussion Starter #13
DWB said:
Sierra manuals (at least, the one that I have) show "hunting loads" and "accuracy loads" and how they make a specific determination is likely based on their test barrels, however, we don't have access to those barrels. We may choose to use those guidelines, and hopefully, get lucky in finding an accurate load, at a velocity level that we are trying to acheive. Like 1 big hole said... "Sometimes, its not even close..."
DWB,
I was looking for a load in that very manual and that is how I got into generating this thread topic. :eek: ;D I was looking at the velocity range of the "most accurate" load. ;D

CJ
 

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Question I would ask is most accurate in what? Pressure barrel, M77, Model 70, #1, AR. Every rifle and pistol is different. barrel weight, twist rate, exact diameter, headspace.......
Manuals give you a starting point and a recommendation, but most accurate, fastest, best is up to you and your individual gun.
CF
 

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result even vary with the heat of the barrel and the outside temperature. To many factors, that is why reloading is so interesting.
 

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Discussion Starter #16
Chihuahua Floyd said:
Question I would ask is most accurate in what? Pressure barrel, M77, Model 70, #1, AR. Every rifle and pistol is different. barrel weight, twist rate, exact diameter, headspace.......
Manuals give you a starting point and a recommendation, but most accurate, fastest, best is up to you and your individual gun.
CF
I agree that you have to find the load that performs the best in "your gun", but the "theoretical' question was basically - -- would the same weight bullet loaded to the same velocity in three different powders have similar accuracy/point of impact? ;) It is apparent that the answer is "probably not" due to a whole group of factors such as; powder burn rate, powder density, barrel harmonics, etc. ::) But I was thinking it could might be used for a starting point for load development in a given rifle. Say, start a grain lower and work up to a grain higher than the optimum velocity load. Of course there is still the question of ----is that really the optimum velocity for accuracy in your your gun? No, it is probably just the right velocity for the test barrel used in the load developement. :(

CJ
 

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papajohn said:
Even if you could remove ALL the other variables, changes in barrel harmonics alone would probably be enough to skew your results. I start out by trying to find a bullet the gun shoots well, then adjusting velocity and seating depth until it tells me to stop. I'm also a big fan of near-100% load density for ballistic uniformity. 8)
I agree with this. (I know, PJ, you can't believe it!). In all my years of reloading, I have found that some guns just don't shoot some bullets well, regardless of the powder used. If I find a bullet that shoots well, then I start looking for an accurate load at the velocity I want to achieve. I usually find this in a narrow range of powders. For example, I might get good results from a powder like 4064, or 2520, but if I go to 4350 on the slow side, or 4198 on the fast side, I'm not going to get the accuracy with the velocity I'm looking for, even though it's an inherently accurate bullet in my gun.
 

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"the "theoretical' question was basically - -- "

In theory, there should be little difference between theory and practice. In practice there usually is, big time. Ergo, theory is mostly irrelivant in reloading, test everything as a stand alone.
 

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Cascade Jinx the proof is in the pudding...put the theory in the gun and test it by pudding it on paper :)
 

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Discussion Starter #20
Thanks for the feed back everyone! lot of factortors to ponder over in reloading, but that is what makes it fun and challenging! :)

As long as I get the fpe I need for humane kills at the range I tend to be hunting, then the most important factor to me is the accurcy of a load that also gives me that fpe factor as well. The search goes on, but now armed with the sage advice and council of my MO friends. Thanks again!

Me - If I look for proof in the pudding will I find some chocolate covered bullets? ;D I have been "pudding" it on paper, but the smear marks make it hard to evaluate the results. ;D ;D But I like your approach! Testing is the fun part of this reloading effort!

CJ
 
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