Thoughts on this chrono data

[brentru]

New to the 10mm cartridge, but have experience reloading other calibers (mostly rifle).  I've done a round of load development over the chrono and I'm getting much higher velocities than the book says I should expect.  Was going more for measuring velocity, but the accuracy at 25 yds was nothing to speak of with any charge.  100+ rds through the gun prior to load testing.  Any ideas what might be causing this? 

1 x fired Win brass, CCI 300 primer, AA #9, XTP 180 gr., 1.260".  Conditions: 45 deg., 30.07" Hg, 6700'.  5 shot strings.

Charge: 12.0    12.5    13.0    13.5    14.0   14.5
Avg:      1097   1164   1204    1232   1284  1315   
ES:        72       28      40        55      25      35
SD:        26.5    10.6   14.8     20.2    10.6   12.3

Hornady book max is 14.9 gr. @ 1250 fps.  I got pressure signs at 14.5 gr., so I stopped.  The numbers show I'm pushing 65 fps faster at .4 grains below max.  Something just doesn't seem right to me and not sure where to take it from here.  Any advice is appreciated.

[The_Shadow]

brentru, what gun and barrel length are you running?
The numbers you have are not bad.  However the newer Accurate#9 seems to produce better velocities than the older versions.  Accurate Arms #9 has undergone at least 5 formulation changes over the years.
When AA#9 was first produced it was very fine microbead powder, then they blended with two Winchester powders and then a mix of Winchester and AA#7.

Today Accurate #9 is a flatten ball type, but I haven't heard of the new mixture / blend or actual formulations since Western Powders took over the brand...

[brentru]

Shadow, it is a SA XDM 4.5" 10mm.

[DenStinett]

Brentru:
Welcome to the Forum
Nice report and good information .... thank you
Been loading 10mm since the early 90s and have only used AA5 and 7
Have only Chrono tested a couple Loads throughout that time but have never been as thorough in my testing as this

[brentru]

Den, it is kind of a carryover from doing load development on the long gun side.  I figured that if it is good for load development for the long guns, it should be good for the short ones too.  However, I'm not sure that all of that theory carries over to the short ones.

I did a lot of reading prior to choosing the AA#9 because it sounded like a good powder for the 180 class bullets.  I'm beginning to think that it might not be the right one for my pea shooter from an accuracy standpoint.  Interestingly enough, although I was getting velocities higher than (Hornady) book for the 180 XTPs, when I used 180 gr. PC HC, they averaged slightly slower than the (Western Powders) book velocities.  I'll keep playing with it until I find what works with AA#9 or switch when I run out of it.

Based on my rifle loading experience, I would say that I have 2 accuracy nodes - 12.5 gr. and 14.0 gr.  I'll continue to work around those and see if things improve from an accuracy standpoint.

[The_Shadow]

Thanks for adding the info and your range reports... Being at 6700" the air is much thinner and can allow higher velocities as well. 
The XDM may also have a tighter bore than some other guns, 0.3990" as compared to a Glock with a 0.4010"

I have used Accurate #9 but have gotten better accuracy with other powders using less powder...  As you have seen with the actual nodes in your testing,

[brentru]

Shadow, what would you recommend if I have to switch powders?

[NH45]

These are my results using a Kimber Camp Guard with the original 5" barrel
All loads are with new Starline brass and CCi primers.

9.5 Longshot, Nosler                        180  JHP        1344 fps
11.0 Blue Dot, Nosler                       180 JHP         1332 fps
9.0 Longshot, Nosler                        180 JHP         1291 fps
11.5 V V N-105                               180 FMJ         1291 fps
11.0 Blue Dot  RMR                         180 FMJ         1279 fps
10.5 Blue Dot, Nosler                      180 JHP          1274 fps

And yes, the primers are a little flat and the brass ends up 20 feet away. But, not one bulged case yet.

[brentru]

It is amazing how far the brass flies with the 10mm.  Even factory FMJ flies a good distance. 

Ideally I'm looking for XTP 180 recipes as I have 100 on hand and 200 more on the way.  May consider going to Starline brass if I can't get the Win brass to play nice.

[The_Shadow]

The 180 XTP's will work with most all 180 JHP data.  NH45 Has shown some good data.

You can also study the data in the commercial pull down documentations section, specifically Underwood, Double Tap, Swampfox, Buffalo Bore

180 XTP using IMR800X  9.4 grains @ 1300
180 XTP using LOVEX D037-01  13.0 grains @ 1300
180 XTP using Power Pistol  8.8 grains @ 1300
180 XTP using Accurate Arms #9 14.6 @1350
180 XTP using LongShot Weight: 8.6 grains @ 1250

[sqlbullet]

This is a textbook example of why a chronograph is needed when chasing max loads.  The listed velocity is a max too.  It becomes a whichever is first situation.  Usually we hit max charge before the listed velocity, but not always.

[Bimmer]

... the accuracy at 25 yds was nothing to speak of with any charge.

How was the accuracy? 

Were you shooting off sandbags?  If yes, then I would hope for 3-4" groups at 25yds with a duty-type pistol with a 4.5" barrel. 

If accuracy is much worse than that, and it bugs you, then you might try a different bullet...