Rifle rounds in pistols and vice versa...the powder problem...


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saturno_v
February 4, 2009, 11:59 AM
Bear with me, I'm not a reloader.

If I understand correctly, in general, pistol round loadings use fast powders that make the most efficient use of the short barrel they are intended for.

Rifle rounds, instead, use slow burning powders to take advantage of the longer barrel.

So, following this logic, a pistol round on a rifle platform (for example a 44 Magnum) will make only marginal use of the longer barrel. Conversely, again in theory, a rifle round on a typical pistol barrel (for example the 30-30 on a T/C platform) will rob too much power from the cartridge.

There are some powders that are a happy medium?? Do you reloaders use different powders depending on what platform do you use your ammo?? (it can be particularly dangerous for pistol powders used on a rifle) What kind of powders commercial ammo manufacturers use for their typical pistol/rifle cartridges (for example, 357 Mag, 44 Mag, etc...)??
Or the use of one type of round (pistol or rifle) on a different platform remain an inefficient proposition at best anyway??

Regards

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Art Eatman
February 4, 2009, 12:41 PM
"If I understand correctly, in general, pistol round loadings use fast powders that make the most efficient use of the short barrel they are intended for.

Rifle rounds, instead, use slow burning powders to take advantage of the longer barrel."

Well, yeah, generally.

However, if you shoot a pistol at night, you'll see that there is still unused powder. The fireball is wasted gas pressure. So, there is a notable gain in shooting a pistol cartridge in a longer barrel. I don't have specifics, offhand, but figuring around 30% or a bit more is a ballpark number.

Most rifle cartridges perform best--from a practical use standpoint--in barrels of 18" to 24". (Magnums and near-magnums, 24" to 26") The performance is generally adequate in barrels of lesser length.

All powders when burned provide a curve of pressure versus time. A rapid rise, a coast over the top, and then a falling off. The x-axis is time, a function of barrel length. The y-axis is pressure, which controls the powder charge from a safety standpoint. No matter what sort of powder is used, the accepted safety limit (generally) is around 50,000 to 55,000 psi. (Roughly.) The area under the curve correlates to performance, from a velocity standpoint. More is better.

You cannot increase the velocity from a shorter rifle barrel by using a faster burning powder. To do so would mean a higher-than-safe pressure. In a longer barrel, the slower burning powder gives more area under the curve for a given safe maximum pressure.

Hope this helps, and that it's not too confusing...

Art

1858
February 4, 2009, 01:57 PM
However, if you shoot a pistol at night, you'll see that there is still unused powder. The fireball is wasted gas pressure. So, there is a notable gain in shooting a pistol cartridge in a longer barrel. I don't have specifics, offhand, but figuring around 30% or a bit more is a ballpark number.

Last weekend I chronographed 10 rounds of .45 Colt using a Marlin 1894. The average velocity for 9 loads was 1466 fps (one odd load - bad primer maybe). I plan to chronograph them out of my Ruger Redhwawk (4" barrel) this weekend so I'm curious as to how much lower the velocity will be. A 30% reduction would put them at 1026 fps which would be VERY disappointing. I'm hoping for something around 1250 fps.

http://128.171.62.162/hawthorn-engineering/thr/45Colt_chrono.jpg

** CAUTION: THE LOADS SHOWN IN THE ATTACHED FIGURE ARE NOT SAFE FOR COLT SAA REVOLVERS OR THEIR CLONES. THEY ARE INTENDED FOR RUGER BLACKHAWK/REDHAWK AND MODERN MARLIN 1894 RIFLES ONLY.

:)

R.W.Dale
February 4, 2009, 02:16 PM
If I understand correctly, in general, pistol round loadings use fast powders that make the most efficient use of the short barrel they are intended for.

Rifle rounds, instead, use slow burning powders to take advantage of the longer barrel.

this is incorrect and thus your logic is completely flawed . Don't feel bad most experienced handloaders don't get this either. Instead it should read.....

If I understand correctly, in general, pistol round loadings use fast powders that make the most efficient use of the small case capacity and low expansion ratio.

Rifle rounds, instead, use slow burning powders to take advantage of the larger case capacity and to keep pressures in check due to the high expansion ratio.

Barrel length has vuritually nothing to do with the optimum burn rate for a cartridge. A great example of this are TC handguns chambered for rifle cartridges, 9 times in 10 the propellant that offers the highest velocity in a 14" handgun is still a top performer in a 24" rifle bbl.

Even in my 10" 30-30 revolver Varget is still the top performer with 150 & 170grn bullets

saturno_v
February 4, 2009, 03:55 PM
Krochus, thanks for the explanation...this make things very clear...so many people say "never use pistol powder on a rifle!!"...that statement actually makes no sense..they should say "never use pistol powder on a typical rifle round"...you can use a regular 44 Mag pistol round in your .44 carbine....but you should not use a pistol powder reloading your 30-06 ammo.
At this point I think that are many original rifle rounds that appear similar to pistol rounds (straight walled, somewhat small capacity) where the pistol powder can be used.

Well at this point I have a question about some of the Hodgdon reloading tables.
Under the "Maximum Loads" section, for every bullet weight (at least for all the most common chamberings) there are listed several loads that often generate significant velocity difference without generating pronounced pressure difference..actually in some cases the pressure is equal or even lower in the faster load.

So in this case what are the situations where the slower load is preferable?? Why should I choose, if pressure is the same and bullet is the same, the load with less velocity??

Even in my 10" 30-30 revolver Varget is still the top performer with 150 & 170grn bullets


At this point my question would be this: If you take a 44 Mag load (typical pistol round) and a 30-30 load (typical rifle round) with their ompitmum powder for each cartridge (the 44 a typical pistol powder, the 30-30 a typical rifle powder), with their performances out of let's say a 20" barrel, which of the 2 loads, in principle, will lose the most performances when you cut the barrel to 10"??? The loss will be comparable in percentage?? The 44 Will lose more?? Less??

Regards

R.W.Dale
February 4, 2009, 04:06 PM
So in this case what are the situations where the slower load is preferable?? Why should I choose, if pressure is the same and bullet is the same, the load with less velocity??

That's where you start of getting into that Grey area of each gun being it's own individual and the somewhat artistic side of handloading of finding the load that offers the best accuracy in YOUR individual firearm. Theres much more to overall load performance than just the FPS value.

Or in many cases It's simply a matter of already having X powder on hand that's used in another cartridge you load for and just using that. I've done this a lot

1858
February 4, 2009, 07:07 PM
So, following this logic, a pistol round on a rifle platform (for example a 44 Magnum) will make only marginal use of the longer barrel. Conversely, again in theory, a rifle round on a typical pistol barrel (for example the 30-30 on a T/C platform) will rob too much power from the cartridge.

I've been thinking about this a lot today. Are you familiar with Homer S. Powley's equation relating velocity (V) to bullet weight (B), charge weight (C), expansion ratio (R) and a constant (K)?

http://128.171.62.162/hawthorn-engineering/thr/velocity_calc.jpg

I calculated R for my Marlin in .45 Colt (33.4) and solved for K based on the chrono data above with an average velocity of 1466fps. Using K with a value of 6560, I calculated the theoretical velocity of the same load in my Ruger Redhawk with a 4" barrel and an R of 7.4. The theoretical velocity would be about 1200fps which is an 18% reduction compared to the Marlin. Now this value seems reasonable and it's close to the 1250fps that I'm expecting.

So is an extra 266fps in the 20" barrel a "marginal" increase in velocity compared to the 4" barrel? How about the extra 394 ft-lb of muzzle energy?

Note: "K is a constant that depends on chamber pressure and other factors in the gun". Chamber pressure should be the same in the Marlin and the Redhawk but if "the other factors in the gun" are significant, it may not be acceptable to use the same value of K for both. The chronograph will shed some light on that.

:)

mpmarty
February 4, 2009, 07:27 PM
Another thing to keep in mind is that accuracy and velocity don't necessarily go hand in hand. Each rifle and to a lesser extent each pistol will exhibit different accuracy for a given load of any appropriate powder. Varget, H335, H4895, BLC2 are all of moderate burning rates. Each will exhibit more or less accuracy in any individual rifle (they're all rifle powders). The reason for this is in part the harmonic resonance of each individual rifle. Playing with tenth grain increases and decreases, different primers, seating depth, bullet brands will each show different accuracy results. Sometimes, and not most of the time, top safe loads will deliver good accuracy. That's why reloaders have so many different variables to play with in search of that "sweet spot" in load combinations. To add more frustration (or facination) to life we get into reloading our home cast bullets also.:banghead:

FredT
February 4, 2009, 10:23 PM
As you said, you are not a reloader. When you buy your first couple of reloading manuals and read them, you will have most of your questions answered. Good stuff in those manuals. Buy one way before you get started.

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