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Discussion Starter · #1 ·
Is there any advantage or disadvantage to the different burn rates of the powders on the market today? I'm looking at Red Dot, Clays, Clay dot and 700X among others. These powders are all fast burning and have pretty high pressures. (sidebar- is there a difference between psi and lup)?
Then there are powders like green Dot and Unique that have lower pressures for the same muzzle velocities. Is there a better way to go or is this personal preference? Also, is there a never exceed pressure?
 

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Yes, there is a difference between PSI and LUP. But there is no hard and fast rule. LUP (lead units of pressure) is an older measure of pressure.

The fast burning powders you mention are good for target loads. They are safe for modern shotguns if you use the manufacturer's recommended loads.

The slower powders (green dot, etc.) are less economical to use (you have to use more weight of powder to achieve the same velocity), but some people feel they have less recoil. I can't tell the difference.

There is a safe "working pressure" for shotguns, and don't exceed that.

If you use published loads by the manufacturers, you won't!

BobK
 

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Wow! Lots of questions there! I'm sure there are lots of opinions on this, but I'll give you my take: the idea is you want to match the powder burn-rate with its best application. Not only will you get peak efficiency, but most of the time you'll maximize economy as well.

What exactly are you loading? Any of those fast-burning target 12ga powders you listed will work fine for 7/8oz all the way up to 1 1/8oz @ 1200fps. Unless you're exceeding that payload or velocity, they're all fine.

So when would a slower burning powder like Green Dot be better? For pushing 1 1/8oz beyond 1225fps. The reason being, you'll get a slower, safer, longer "push". Unique, an even slower powder, doesn't become a practical 12ga choice until you're exceeding 1250fps, or unless you're pushing a bigger payload than 1 1/8oz.

PSI does NOT equal LUP. PSI is "pounds per square inch", which is the more definitive measure. LUP is "lead units of pressure" which is an older (and some would argue outdated) measuring system which isn't as accurate. There is no direct conversion, even though they're designed to measure the same thing.

As for maximum pressures, the SAAMI maximums are listed here:

http://www.leverguns.com/articles/saami_pressures.htm

(Shotshells are at the bottom).
 

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jaybw,
First, Yes, there is a distinct difference in the usefull range of powders, depending on their burning rates.

Fast powders are the first choice for 12 ga. target loads, from the lightest up to 1-1/8 oz., as they not only perform best but also are more economical to load/reload with fast powders.

Slower powders are used in loads above 1-1/8 oz. in 12 ga. because they perform better at much lower chamber pressures when payloads get heavier.

Slower burning rates are necessary also as the gauges get smaller. This is also to control chamber pressures.

Yes, There is a difference in LUP, (lead units of pressure), and PSI, (pounds per sq. inch). Lup is an antiquated system of using lead crusher units in test barrels. Served it's purpose, but is less accurate than the piezo electric systems now used which readout directly in PSI, and are much more error free. There is no formula with which to compare one to the other. You just take them for what they are, and move on.

Yes there are maximum pressures the MUST be adheared to, that are set by SAAMI, the Sporting Arms and Ammunition Manufacturers Institute.

These are 11,500 PSI for 12 ga. 2-3/4 and 3 inch shells,
12,000 PSI for 20 ga. 2-3/4 and 3 inch shells, 12,500 PSI for 28ga., and 12,500 PSI for 410 bore 2-1/2 inch shells.

There's nothing wrong with loads that approach these maximums, but it is considered far better to pick loads that allow for some margin of safety, below these maximums. However going too low promotes poor performance due to incomplete powder burns and of course dirty burning, meaning leaving excessive derbis in the barrels after firing.

DLM
 

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Discussion Starter · #5 ·
Thank you for your replies and the really good advice. And boy, was I headed down the wrong road. I recently got back into trap (12 ga) after about 20 years off. I reloaded my own at that time, and forgot most everything that I knew about it. And what I remembered had changed. Thanks for the help. Oh btw, I will be reloading 12 gage for 1150 and 1200 fps for 16 yard and handicap, 1 1/8 oz. I may experiment with 1oz loads, but the last few times that I used them, I did not do well.
 
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