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Does barrel length factor into choosing powders?

Lapua40X said:
I'd recommend bite the bullet and go into debt (it's a small debt for such great guidance). I did it the slow painful way - borrowing books from my son. Then again, a guy can only absorb so much at one time so maybe one at a time is good enough. IMO, it's not as important how you work your way through Bryan's stuff, just that he's got so much to offer about why bullets behave as they do that any shooter should be exposed to his work.
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I'm going to bite the bullet.

My good fortune is that Bryan is an engineer and when he enters into the realm of engineering jargon my engineer son is always there to pull me out of deep water.
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Good point! I have a client that's an engineer who's also interested in shooting that I can tap into for clarity.
My grandfather was an engineer. I grew up in a "Math is life and life is math" world. That seems to have rubbed off on me a bit.
 
A ~22" barrel is common in 6PPC. This is a tiny little cartridge burning N133.
If this was most accurate regardless of powder, then we would all be using 22" barrels, whether shooting 6PPC, 243win, or 6STW. Right?

Well, flat base bullets are commonly used in 6PPC, and even with such a short barrel it's muzzle pressures top at ~6-7Kpsi (per QuickLoad). This allows very clean bullet release.
Larger capacity cartridges need more slower powder, which liberates more gasses, smacking the backsides of bullets on release.
In fact, these gasses can provide a secondary pressure peak well exceeding that of chamber pressures. If your hat is blowing off with shots, your muzzle pressures are extreme, and this cannot be 'good' for an accuracy endeavor. Also a boat tail provides more area for this muzzle pressure to influence.

I know, somebody out there is shooting 1/8moa with a 264wm pistol..
But this anecdotal basis would have us all shooting pistols at 1kyd.
I try to keep my muzzle pressures at or below 8Kpsi per QuickLoad. I think if you check the most accurate cartridges & loads, this is what you'll see.
I control this with barrel length, and powder choice (given good load density) for the chosen bullet.
If I want a ~25" barrel in 25cal. I pick the bullet and cartridge capacity to meet my goals with available powders.
Compromises come into play, but I prefer not to leave myself short on barrel length.
 
I grew up in the semiconductor business before circuit simulators were available. When they came available, we learned that they were great design tools, but we also learned to not trust them implicitly! We used them for the extra information we could get from them in addition to the bread-boards we also built of the new design.

I now use QuickLoad as a helpful simulator to work up new loads and when picking powders. It is a guide, not the Holy Grail!

So, one can compare different powders and different loads in a given rifle barrel to see how they change.

I determine my load by shooting 5-6 five shot groups at 200 yd over a chrony with loads incrementing 1% or so per step. I find the best load by comparing ES of these 5-6 loads after plotting the ES's in EXCEL and doing a 3 to 5 power exponential curve fit.
The primary parameter from this data is Mv! But, if you change powder you have to re-characterize as the barrel time for the same velocity will change and barrel time is the prime factor in tuning. After finding the right load, I then tune the barrel tuner from its original setting at an arbitrary zero to what gives best groups at distance.
The ES tunes for primary longitudinal resonance (like an organ pipe) and the tuner tunes for the beam resonance where the barrel wiggles up and down.
 
I wasn't saying QuickLoad was an input to my tuning procedure, but that QuickLoad was a simulator that can show one the relationship in barrel length, powder and load.
 
QL is a good reference go how far off the burn rate of your powder is. They use the factory specifications of the factor burn rate. The H 4350 is dead on . Varget is off as much as 70' from lot to lot. Larry
 
mikecr said:
A ~22" barrel is common in 6PPC. This is a tiny little cartridge burning N133.
If this was most accurate regardless of powder, then we would all be using 22" barrels, whether shooting 6PPC, 243win, or 6STW. Right?
... If your hat is blowing off with shots, your muzzle pressures are extreme, and this cannot be 'good' for an accuracy endeavor. Also a boat tail provides more area for this muzzle pressure to influence.
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FWIW Virgil King (of The Houston Warehouse lore) always used a barrel 21.75" long, with every cartridge, and flat-based bullets. In particular, his most accurate rifle was a 22 PPC (datum shortened .050) burning IMR 4198 and 205M primer behind 52-gr Remington Bench Rest bullets. The powder charge was only described as "on the warm side".

I wonder what his muzzle pressure would have been?
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