Shotgun Powders all Fast Burning?

[flmason]

Hi All,
    Was looking at burn rate charts and was surprised to see Red, Green and Blue Dot powders are all way up at the top near things like Bullseye. Completely the opposite of what I would've expected considering the weight of shot charges, the long barrels etc.

Anyone know why that is?

Just curious what the technical rationale is, because I missed it completely. And having long believed in picking the powder that gives the most velocity for the least pressure, was kind of shocked that shotguns use such inherently fast powders for such normally low pressures compared to rifles and whatnot.

Probably inherited a dislike for fast powders. Was told as a kid that powders like Bullseye erode barrels and rifling at a much accelerated rate?

[Graybeard]

You were fed some bad info as a wee lad. Bullseye is great stuff. I've used a lot and never seen any problems it caused.

As to why they are on the fast end of the powder burn rate scale I'd guess pressures have a lot to do with it. Most shotshells operate at a max of around 10,500 LUP. The .410 can reach about 12,000 LUP and uses the slowest of the shotgun powders.

Shotgun and handgun powders usually are very similar in burn rates and in fact many shotgun powders are also the more popular handgun powders such as Unique and the dot powders as well as both 700X and 800X.

Average shotgun velocity is around 1200-1300 fps with lead shot. That's also close to the max of most handguns other than a few of the larger magnums.

[redleg155]

And to add to GB's comments, the .410 shotshell uses typically the slowest of shotgun powders.  Nearly all of the factory .410 shells in the world are loaded with H110 or commercial equivalent.  You can reference that in the general powder burn rate charts and see that, it too, is on the very fast side for metallic cartridges.
 
- redleg

[huntswithdogs]

I have always thought or justified it as, it was to have a small amount of powder to move a very large payload.

HWD

[flmason]

You were fed some bad info as a wee lad. Bullseye is great stuff. I've used a lot and never seen any problems it caused.

As to why they are on the fast end of the powder burn rate scale I'd guess pressures have a lot to do with it. Most shotshells operate at a max of around 10,500 LUP. The .410 can reach about 12,000 LUP and uses the slowest of the shotgun powders.

Shotgun and handgun powders usually are very similar in burn rates and in fact many shotgun powders are also the more popular handgun powders such as Unique and the dot powders as well as both 700X and 800X.

Average shotgun velocity is around 1200-1300 fps with lead shot. That's also close to the max of most handguns other than a few of the larger magnums.

Well, yes, clearly the burn charts show that only Blue Dot (of the Dot powders) is slower than Unique and all are definitely "fast". IMR 4198 is considered a fast rifle powder and it's slower than 2400, what I'd consider a slow pistol powder.

As to Bullseye (in handguns), even if it's doesn't burn exceptionally hot, if it's got the same peak pressure as a slower powder, it's got to "beat" on the gun more as it's the same pressure in less time. Perhaps the reality is, it's not enough to worry about, but hard to tell since the charts I'm finding don't give any sort of indication of "how fast" one powder is compared to another, just a ranking.

Somehow I find it ironic that the fastest powders, those most likely to blow the gun with an overcharge, are used for the lowest velocity loads. Can't quite figure out why it should be that way. I realize the idea of a quick pop vrs. a long push, but still can't find a reason other than powder cost to even want to use the faster of two powders when selecting a powder?

Seems like it's trading barrel punishment for lower powder costs?

[Val]

In order to reduce my inventory of different powders I use Bluedot for both my 44 mag and 9 mm semi-auto.

[nitesite]

I recall reading that shotgun propellants are quick burning in order to let peak pressures drop to a safer level before the thick walls of the chamber area transition to the very thin walls for the rest of the barrel. 

[flmason]

I recall reading that shotgun propellants are quick burning in order to let peak pressures drop to a safer level before the thick walls of the chamber area transition to the very thin walls for the rest of the barrel.

I'd actually been wondering about that possiblity of late. I noticed that transition in thickness and was thinking... hmm... maybe it's [what you said].  Contain the bang... taper the walls to go along with the drop in pressure. Shotgun barrels do strike me as rather thin, all things considered.

Interesting that something that moves so much lead uses the least progressive powders. The whole thing strikes me as almost paradoxical. LOL!

[epanzella]

On a related note, why is it that slug loads like corelokt ultra's and SST's can advertise 1900 fps while I can't find a published load for my Savage 220 that comes anywhere near that. Why is it that ammo companies can do things with their ammo that powder companies can't duplicate with their powders?

[kynardsj]

If I'm not mistaken, Lilgun, which is my favorite magnum pistol powder, began life in 410 shotgun shells.

[Couger]

On a related note, why is it that slug loads like corelokt ultra's and SST's can advertise 1900 fps while I can't find a published load for my Savage 220 that comes anywhere near that. Why is it that ammo companies can do things with their ammo that powder companies can't duplicate with their powders?

Two words that most affect what you're asking;  litigation and lawyers. 
 
 
 
Companies that sell powder to reloaders cannot control what careless and sometimes dumb people do!

[BBF]

Visualize the  difference of space in a barrel that gets created as the bullet vs shotgun charge moves forward.
Disregard max pressure for a moment.
There is a big difference in space(volume) between a 6mm bullet and a 12 gauge "package" as it moves toward the muzzle.
To fill up the space without going into rifle pressure you need a small amount of fast burning powder.

[jedman]

   Economy is the reason shotshells and for that matter most all factory loaded ammo is loaded with the type of powder that they can use the least amount of and get the velocity / pressures that are safe and cost the least to load.         Jed

[flmason]

   Economy is the reason shotshells and for that matter most all factory loaded ammo is loaded with the type of powder that they can use the least amount of and get the velocity / pressures that are safe and cost the least to load.         Jed

Have often believed that. At least with say .38 wadcutter target reloads and such. I mean 3 gr. or Bullseye, can't hardly beat that price-wise. What I wonder about is the effect on the gun's longevity. Not that I've ever worn a gun out, not even an ancient one. Closest thing to worn out I've seen were an old, old steven .22 bolt and a Marlin pump shotgun... but it was moving action parts, not anything designed to hold pressure.

But still wonder about barrel erosion on the faster powders.

But what prompted me to post the thread was the seeming paradox with shotshells. I'd think you'd want to slow start pushing a heavy payload, yet shotgun powders are some of the fastest going. Noticed this while looking at reduced loads and cast bullet data for my Mosin. Was thinking, "Geez, why do I want to pound the heck out of the gun for *less* performance?"

At least with "normal" loads I've always tried to get lowest peak pressure for velocity delivered.

[JoeG52]

 Shotguns have a larger diameter bore compared to most rifles and as the bullet / shot starts moving down the bore the volume that the gasses have to fill becomes greater much faster than in the smaller bores. You need a faster powder to keep up with the increasing volume to generate enough pressure. Larger bore shotguns use faster powder than smaller bore shotguns.

[flmason]

Shotguns have a larger diameter bore compared to most rifles and as the bullet / shot starts moving down the bore the volume that the gasses have to fill becomes greater much faster than in the smaller bores. You need a faster powder to keep up with the increasing volume to generate enough pressure. Larger bore shotguns use faster powder than smaller bore shotguns.

Interesting thought. The way I've been visualizing it is the fast burning powders go "pop" and then the heavy shot payload starts to move and the pressure declines rather rapidly as evidenced by the barrel taper and that on at least the NEF shotgun I have... the bead's mounting hole goes all the way through the barrel. 

Very counter-intuitive to me. But, clearly it works. Guess that's why I'm not a firearms/propellant engineer, LOL!