AA#7 in the 5.7x28mm?

[Lucifer]

I load AA#7 in a variety of calibers and was pleased to see it listed in the Accurate loading manual. Perusing this site I found a thread from a few years ago where one guy said AA#7 meters poorly and described it as a flake powder. The AA#7 I load is more of a ball type powder and meters quite well?

Anyone have success with AA#7? I'm not looking for maximum velocity...maybe a touch warmer than factory SS197SR with the 40gr VMax, but I'd be fine loading up a clone as well if that's generally the safest route.

If I start out low, stick to the chrono and stay well off max listed loads I imagine I should be okay assuming common sense? I'm thinking a ceiling of 1800FPS...sound reasonable? How many loadings you guys get off once fired?

[panzermk2]

Welcome to the forum.

AA#7 works great for the 5.7 as long as you're not at the upper limits. It meters ok for the 5.7. Not the best.

Here is why, if you are .1 of a grain off on 45acp with W231 you will NEVER know it. Now with the 5.7 .1 can take it from a safe 45kpsi to 55kpsi, 5k over max.

This is the issue with AA#7 keep it around 40k and you are good. Get above that and it gets very spiky due to how it meters.


As long as you properly clean you brass and NOT tumble it you can get 5 to 8 reloads. About that time the coating and the shoulder/neck gives out if the primer pocket has not loosened up already by 5x.

Also keep in mind we sell virgin brass.

[DoubleJ]

...

This is the issue with AA#7 keep it around 40k and you are good. Get above that and it gets very spiky due to how it meters....

Lost me here, how does the metering of a powder cause pressure spikes? AA7 is also a spherical powder, like AA9 and HS-7, which both meter great.

[panzermk2]

Inconsistent metering means hi and low pressures. Keep in mind the missing powder that creates a low charge will then dump with the next.

Add to that powders change how they work when pressures get above 40k

7 and 9 work great for pushing 10mm but even really hot 10mm does not get above 38k psi.

7 and 9 meter OK not great. Static in the powder funnel play havoc with them.

Spend some time digging into the reloading section.


Members found this out years ago when they started loading and chronographing 7 and 9. Chronograph readings would be very consistent until they got above 40k, pressures estimated on their part by velocity, then they would get inconstant.

I also knew this from years of chrono and pressure barrel testing which is why I never used 7 or 9 for the 5.7

[DoubleJ]

I haven't played with AA7 in the 5.7, as I've read it's not ideal, but I use AA9 exclusively in my G20 and my .357 Sig chambered M&P, and it meteres great from my cheapo Uniflow. As for the 5.7, I only use my 1500 to charge cases, so I know it's always x.x grains going into each case. If AA7 creates erratic pressures, and your measurement method is good, then something else is at work (like H110 does with light loads maybe). Poor metering of any powder will give wide pressure variations, but it isn't the metering properties that are causing it, it's the variations in charge weight.

How did the members know they were above 40k? They have pressure barrels?

I've spent plenty of time digging through the reloading section, as well as loading and testing, I'm not exactly new to the 5.7 or the forum. That's why I have no experience with powders that don't work, I read that they don't work, so I didn't try them, except for HS-6, which I got a giant can of free, so I confirmed that it doesn't work above plinking loads.

[panzermk2]

FPS combined with known weight of bullet can give a good idea of pressure.

I use a pressure barrel and a chrono to verify. About 40k 7&9 have spike issues end of story. If you want to push please feel free. I am just passing on free information.

Again powders are designed to work a certain way in within a set of parameters. Pressure is NOT linear.

Example A slower powder like Ramshot Enforcer ABOVE 40k burns FASTER then True Blue.

Just like temperature changes how powders behave so does pressures.

But carry on, take it to 50k.

[spyderco monkey]

FPS combined with known weight of bullet can give a good idea of pressure.

I use a pressure barrel and a chrono to verify. About 40k 7&9 have spike issues end of story. If you want to push please feel free. I am just passing on free information.

Again powders are designed to work a certain way in within a set of parameters. Pressure is NOT linear.

Example A slower powder like Ramshot Enforcer ABOVE 40k burns FASTER then True Blue.

Just like temperature changes how powders behave so does pressures.

But carry on, take it to 50k.

Based on your testing, what do you consider the best off-the-shelf powders for the 5.7x28, in terms of both safety and performance?

[panzermk2]

True Blue hands down and it was even used by FNH for awhile in the 192 and white box 195. Damn stuff is still rare as hens teeth though.

Consistent as you can get even above 55kpsi


3N37 and 3N38 are good also.

7 and 9 aren't bad. Just not good at the upper limits.

If you really wan to get a better understanding of what's going on I recommend starting with this book.

Ballistics: Theory and Design of Guns and Ammunition, Second Edition 2nd Edition
by Donald E. Carlucci