50cal
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Not at all. N310 is fast. I can get 100% burn using 'slower' powders too. I prefer the 310. Theory and calculations are just that. Personal preference is subjective and derived through experience.
Powder burn rate and barrel length
- Thread starter Zendude
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Many years ago in one of the gun magazines (when I still subscribed and read them) had an article that answered the question well. They took .357 mag ammo loaded with a standard bullet wt and manufacture using slow and fast powders. They shot each load over a chrono starting with a long barrel, then cut off an inch of barrel length and repeating the procedure.
The measured results showed that slower powders (2400 and H110) that produced higher velocities in the long barrel when compared to the faster powders used also produce higher velocities at each subsequent shortening of the test barrel. I believed they stopped at a 1" barrel.
The measured results showed that slower powders (2400 and H110) that produced higher velocities in the long barrel when compared to the faster powders used also produce higher velocities at each subsequent shortening of the test barrel. I believed they stopped at a 1" barrel.
50cal
Member
Exactly.
I am not at all surprised. Powder energy is not dependent on burn rate or the type coating/retardant used. The chemistry of the powder itself varies and is what produces the energy. This is why I suggest experimenting with a variety. 100% burn, 70% burn, etc. is not a factor that important to me. I want the energy that works best for my bullet and my gun to be produced in about 4 hundredths of second and I don't care what is happening after that (once the bullet is gone).
I do however consider 'rates' because given the information supplied by manufacturers, its pretty much all we have to go on (granule shape is another) and there is simply too many powders test a wide enough variety for each gun. I found I like VV powders and work with them almost exclusively in everything from .38 Supercomp to rifle cartridges. In my mind I get better accuracy with it, it's clean and meters consistently.
I have generally found that "best" performace [i.e., accuracy] is found for a target velocity when:
- Case fill is between 102-106% (by QuickLoad volume calculations)
- Burn completion is between 95-98% at the muzzle
If the target velocity is max, this works
If the target velocity has already been established (i.e., matching a 308Win 175gr/2,550fps figure in a M1A),
it still works -- even though w/ a different weight of a different powder
This makes for best starting point, and I generally find the optimum a very short distance above/below the start.
- Case fill is between 102-106% (by QuickLoad volume calculations)
- Burn completion is between 95-98% at the muzzle
If the target velocity is max, this works
If the target velocity has already been established (i.e., matching a 308Win 175gr/2,550fps figure in a M1A),
it still works -- even though w/ a different weight of a different powder
This makes for best starting point, and I generally find the optimum a very short distance above/below the start.
50cal
Member
Cool. A numbers guy 
Calculated but not measured - don't see how you can measure burn completion within 3%. Nonetheless seems like a good starting point (vs ladder). Since this focus is on pistols and for the most part similar hand guns will spec out closer than long guns, what is your best (in terms of accuracy) .45ACP load (5" or commander)?
Calculated but not measured - don't see how you can measure burn completion within 3%. Nonetheless seems like a good starting point (vs ladder). Since this focus is on pistols and for the most part similar hand guns will spec out closer than long guns, what is your best (in terms of accuracy) .45ACP load (5" or commander)?
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Zendude
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It sounds like for each powder type, you would need a chart showing velocity for each barrel length. I have seen charts like this but much of the data was interpolated rather than produced empirically.
Although more energy per gram could be produced by powders with different chemistry, the upper limit is still the maximum safe pressure for the cartridge. It seems like any powder could achieve the maximum allowable pressure, but a powder that has less than a 100% burn rate would be an inefficient choice.
50cal
Member
Are you saying efficiency equals accuracy, or maximum pressure equals accuracy or both/neither? Notwithstanding case integrity or unsupported area - for autos, "Safe" is circumstantial depending on many factors. Calculations have their place, more so in l/r bench shooting as far as I am concerned. The only handgun I have that is accurate at very high pressures is the fully compensated custom below. Otherwise my most accurate loads are far below a supposed max pressure and with no consideration for efficiency. There is plenty of load data that is empirical and posted by manufacturers and qualified reloaders. That is a good place to start.
Experimental physics and chemistry are both numbers games.
That said (again), one can look down a barrel after a session and
tell if it's a complete burn (or in many cases most definitely NOT
)Note also that while powders can burn "dirty" and still be complete,
it's the intact granules litering the bore that spell the difference visually.)
As the velocities match -- ergo energy inserted matches -- I tend to
trust when QL tells me how the powder/bullet/barrel combination
has performed.
Pistols, however, are different when it comes to "old" BP-heritage
cartridges. There's no way to use case-fill predictions at that point other
that to look for visually-safe case fill percentages.
I've got my best of the best 1911 "truck gun" load-choice/pic on the home computer.
I'll post that one this PM.
Truck Gun Load/Performance/25Yd:
Ballistic efficiency is not the issue (which is also different from burn efficiency)
The target is what bullet/what speed/what pressure.....
Only at Mag cartridge performance with powders that come no where near
efficient burn (and therefore one is dumping a whole lotta "stuff" at bullet exit)
does burn completion rear it head for purposes of accuracy.
Ballistic efficiency is not the issue (which is also different from burn efficiency)
The target is what bullet/what speed/what pressure.....
Only at Mag cartridge performance with powders that come no where near
efficient burn (and therefore one is dumping a whole lotta "stuff" at bullet exit)
does burn completion rear it head for purposes of accuracy.
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Zendude
Member
Powder efficiency and accuracy are probably not related too much. I would guess that accuracy woul be greater with powders that have the most consistent burn rate and pressure generation. Quality control and particular chemical ingredients would likely determine accuracy (i.e. if 1000 samples of 3 grams of a particular powder had little or no variation in burn rate and energy produced, then it should produce high accuracy)
50cal
Member
Anyway, Zen what gun are referring to in the original post? Chances are you want something on faster end of the spectrum (N310, Titegroup, Bullseye). A lot of slower powder in the casing will certainly give you a significant fireball in a 2in barrel. Bullet weight plays a role in powder selection but less so in handguns and even less so in revolvers. You can control bullet weight. A lighter bullet will be more accurate in handguns generally (less recoil and torque) and give higher velocities. Try different bullets to find the most accurate.
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Zendude
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Anyway, Zen what gun are referring to in the original post? Chances are you want something on faster end of the spectrum (N310, Titegroup, Bullseye). A lot of slower powder in the casing will certainly give you a significant fireball in a 2in barrel. Bullet weight plays a role in powder selection but less so in handguns and even less so in revolvers. You can control bullet weight. A lighter bullet will be more accurate in handguns generally (less recoil and torque) and give higher velocities. Try different bullets to find the most accurate.
I am loading for a 32 H&R magnum with a 2 inch barrel. I am currently using Bullseye powder at about 3.5 g. I load 100 grain plated and 85 gram Hornady XTP bullets and plated Ranier 100g. solid ,
50cal
Member
Sounds to me like you are in the right ball park. How are those loads working out? If you have a lot of room in the cylinder you might try .327 brass (Starline rocks) and work it up. Getting the bullet closer to the forcing cone is good.
Not much else I would do aside from N310 powder. The cylindrical shape might meter better. It's cleaner than Bullseye too.
Not much else I would do aside from N310 powder. The cylindrical shape might meter better. It's cleaner than Bullseye too.
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Zendude
Member
If I can find some N310, I'll give it a try. Starline brass has worked well. When I purchased the 32, I ordered a 500 pack of Starline brass. So far so good.
Baselining the Hornaday 100XTP: I'd try these powders/in order:
Alliant POWER PISTOL
Vihtavuori N350
Vihtavuori 3N37
Alliant BULLSEYE
Vihtavuori N330
Winchester WAP
Ramshot Silhouette
Hodgdon HS-6
Hodgdon Longshot
Ramshot True Blue
Winchester 540
Alliant UNIQUE
Vihtavuori N340
Alliant HERCO
Alliant POWER PISTOL
Vihtavuori N350
Vihtavuori 3N37
Alliant BULLSEYE
Vihtavuori N330
Winchester WAP
Ramshot Silhouette
Hodgdon HS-6
Hodgdon Longshot
Ramshot True Blue
Winchester 540
Alliant UNIQUE
Vihtavuori N340
Alliant HERCO
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Zendude
Member
Hopefully the powder shortage will pass. The only ones I can find right now are Bullseye and Universal.
BCRider
Member
Your mistake is in thinking that the burn rate is related to the barrel length. It ain't so.
The burn rate is related to the volume of powder used in any given cartridge and to control the pressure build so as to avoid a pipe bomb scenario.
That's why the results become catastrophic if a fast burn pistol powder is used in a rifle cartridge by accident. It's not that the powder produces so much more gas than the slower burn rifle powder. It's that the bullet can't move far enough down the bore before the powder burns to avoid a super high peak pressure that splits the gun apart.
This is why even within a rifle bullet load data that you often see powder options for bullets at one end of the weight range that are not included at the other end of the weight range. With relatively low difference between upper and lower limits with the rifle powders a change in bullet weights can result in one becoming dangerous when the burn rate isn't correctly matched to the bullet weight so the bullet movement and burn rate work together to achieve a safe build to the pressure peak.
The same on a smaller scale applies to magnum handgun loads. Lots of pressure is needed so lots of powder is used. But the powder has a slower burn rate so the bullet moves down the bore a little ways before it's all burned so the peak pressure that is reached is tempered with a gain in chamber volume by the bullet being out of the case and at least a short way down the bore. It won't be much but even a bullet length or two opens up the volume sufficiently to limit the peak pressure.
The burn rate is related to the volume of powder used in any given cartridge and to control the pressure build so as to avoid a pipe bomb scenario.
That's why the results become catastrophic if a fast burn pistol powder is used in a rifle cartridge by accident. It's not that the powder produces so much more gas than the slower burn rifle powder. It's that the bullet can't move far enough down the bore before the powder burns to avoid a super high peak pressure that splits the gun apart.
This is why even within a rifle bullet load data that you often see powder options for bullets at one end of the weight range that are not included at the other end of the weight range. With relatively low difference between upper and lower limits with the rifle powders a change in bullet weights can result in one becoming dangerous when the burn rate isn't correctly matched to the bullet weight so the bullet movement and burn rate work together to achieve a safe build to the pressure peak.
The same on a smaller scale applies to magnum handgun loads. Lots of pressure is needed so lots of powder is used. But the powder has a slower burn rate so the bullet moves down the bore a little ways before it's all burned so the peak pressure that is reached is tempered with a gain in chamber volume by the bullet being out of the case and at least a short way down the bore. It won't be much but even a bullet length or two opens up the volume sufficiently to limit the peak pressure.
50cal
Member
'A' for effort.
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