AA #9 OK to underload?

I've used AA#9 slightly below starting loads in 10mm without problem. It burns a little dirtier, but still cleaner than Unique. I took comfort from the fact that the .40 loads went WAY below the start 10mm loads, and all the 10mm start loads just looked to be max minus 10%, rather than some tested-for lower limit.

I made a few test rounds and confirmed that they worked, of course.

When I tried it in my 10mm, it worked,,, but the velocity ( pressure) variation really went nuts, thus giving me some very crappy groups.

I treat it the same as H-110/WW296. I've had bullets stuck in the barrel due to squibs with all of them.

Buck13 said:

What recipe did you use for .40? Accurate's website doesn't even mention #9 in .40 S&W.

Click to expand...

I can't recall. I have a number of loading manuals, so it could be from one of a number of them. I'll check my notes when I get home and see if I can figure that out.

But I didn't use a .40 recipe, just took comfort from the fact that the high end of the .40 recipe was near what I was downloading to. Just to be clear, I wasn't going WAY light, just a bit below starting... probably one hole smaller on the Lee Auto Disk.

Obviously, I make no representations or warranties as to the wisdom or correctness or safety, etc., of any load I'm talking about. I just know I've gone a little below start loads and not had problems with function.

Float Pilot said:

When I tried it in my 10mm, it worked,,, but the velocity ( pressure) variation really went nuts, thus giving me some very crappy groups.

Click to expand...

Interesting. How far below were you going?

Check the Accurate Load Data and you will see the numbers they list are not all that different for AA#7 and AA#9 in the 10mm with the same bullets. Actually, some of the AA#9 loads generate less pressure than the AA#7 loads. I'm sure AA#9 will work just fine in the 10mm after looking at the data.

I use a LOT of #9 in my 10mm with 180gr jacketed, and to be honest the start loads aren't much to worry about if recoil is your concern.

My standard load is usually in the 13-13.5gr range depending on just who's 180gr bullet I am using. I don't recommend simply jumping right on up to the above listed amount however without working up slow. You could easily find your most accurate load somewhere before those weights.

OK, checked my notes and my manuals. Upon further examination, what I did was find published data in one load manual (Hornady) that went lower than other sources. Significantly lower than Speer's listing, for example. Hornady's manual is one of the few that does not appear to just base their start loads on a 10% reduction of max. So go look at a Hornady book if you want published softish data on AA#9.

Once again, no representations or warranties made, proceed at your own risk, etc.

No reason to treat AA#9 like W296/H110, they are in no way the same. AA#9 is not hard to ignite while W296 can be especially in the colder weather. Also, Accurate does not have a standing warning not to download their #9 powder more than 3% like Hodgdon does with W296/H110.

Buck13 said:

With the 180 gr Rainiers, the #9 starting load at 12 grains is pretty close to what I wanted.

Click to expand...

As suggested in my earlier post, check the Hornady manual if you want "permission" to go a little lower. Like half a grain or thereabouts.

AA #9 OK to underload?

Click to expand...

I will so no based on my experience with Accurate #9 in 357 Magnum, I have had pressure spikes with #9 using standard primers with reduced loads.
#9 works well for me in 357 mag at moderate temperatures with SPP but at colder temps it is not consistent so I am using magnum primers now.