AutoComp Powder in 10mm

[10mm-Admirer]

They say "necessity is the mother of invention."  With the powder shortage going on, my powder choices are rather limited since I wasn't reloading 10mm prior to the shortage.  I don't want to use up my Power Pistol too quickly so I turned to a 1lb container of AutoComp powder I had on the shelf.

This morning I loaded up some Hornady 180gr FMJ FP bullets with Winchester AutoComp powder

180gr Hornady FMJ FP bullet
CCI 300 LPP
1X Starline cases
7.2, 7.5, 7.7 gr of Winchester AutoComp powder
OAL:  1.250"
I was shooting a G20SF with a KKM 4.6" barrel and BT Guide Rod and 22# ISMI recoil spring.

I don't have a chronograph right now.  Sorry.  In a weak moment I shot my last one.  So, this data is anecdotal.  However, there doesn't seem to be much information on the internet about AutoComp in 10mm.

The online Hodgdon data shows 7.0gr of AutoComp to be the starting load and 7.7 to be max with a 180gr bullet.

The 7.2 load was soft and accurate
The 7.5 load had more recoil and continued to be accurate
The 7.7 (max) had moderate 10mm recoil and was accurate. Showed beginning signs of pressure on the primer compared to others.

Observations:
I noticed with the lighter loads there was some smoke and soot on the barrel and cases.
No unburned powder was visible in the barrel, chamber or breach face area.
Accuracy was good.  Good as I can shoot.
Feeding was 100% with the heavier 22# spring.
I am going to estimate velocity at 1,150 fps since the data showed 1,199 with 5" barrel and I was using a 4.6".
The 7.7 max load is usable and about max.

I'll be able to use AutoComp on practice rounds until more suitable 10mm powders become available.

I had trouble with heavy boutique 10mm loads and reliable cycling in my G20SF with a 22# recoil spring.  Since I've started loading max book loads and shortened the OAL to 1.250", cycling has been 100%.

[The_Shadow]

That's a good report and about what is expected from the AutoComp powder in the 10mm.

Hodgdon's data does show the Sierra 180 gr JHC (like a JHP) OAL 1.2600" using 7.7 grains @ 1199 pressure reaching 36,000 psi at your max load with 5" BBL.  Using the 180 FMJ should be a slightly shorter bullet length and slightly less pressure.

With the 10mm MAP set at 37,500 psi your load is 1,500 psi short of the max SAAMI and should be very safe.

I like the fact you shorten the OAL, that would be what I would have done also, that would raise the pressures just a little but like mentioned earlier, that bullet is already shorter so the pressure would about even out.

At your lightest loading, the soot was probably because the casing didn't fully expand to seal the chamber thus the pressures were too low for the best burn.

Yes, without the Chrony you are sort of working blindly, not getting to see you velocity numbers...

[attrapereves]

Autocomp really isn't a great powder for 10mm. However, I've had decent luck with it in 9mm.

[10mm-Admirer]

Shadow, the data I used from a couple of Hodgdon sources listed the tested OAL at 1.250".

Attrapereves, I am limited on my powder choices with the powder shortage we're experiencing.  Looks like AC does better, velocity wise, with lighter bullets.  I'm going to try it with lighter bullets.

[attrapereves]

Shadow, the data I used from a couple of Hodgdon sources listed the tested OAL at 1.250".

Attrapereves, I am limited on my powder choices with the powder shortage we're experiencing.  Looks like AC does better, velocity wise, with lighter bullets.  I'm going to try it with lighter bullets.

Definitely understand that! I'd stick with 165gr pills for Autocomp. You should be able to crank out some decent velocities. Actually, you could even work up a nice 1150-1200fps load with 180gr pills.

[10mm-Admirer]

Why would you stick to 165-180 bullet loads with AutoComp?  Loading data shows good velocities with 155gr bullets and I have some XTPs on hand.

[10mm-Admirer]

I loaded and fired 31rds of 10mm AUTO with 7.7gr of AutoComp with 180gr Hornady FMJ FP and 6 XTP HP bullets.  This a max load according to Hodgdon.  This time I experimented with longer OALs, 1.255-1.260".  All fed reliably and shot accurately in my newest G20SF (have 2) with a 5" KKM barrel.  I didn't notice any pressure signs and recoil was mild.  I wasn't recoil sensitive at all today.  The pistol and handloads were as accurate as I can shoot.  I shot well but was the limiting factor.  When I did my part the pistol and ammo delivered.  Couldn't expect or ask for better.

[The_Shadow]

Man I wish you had a Chrony! 

[10mm-Admirer]

Me too.  A Chrony needs to be my next purchase.  I've noticed more soot and stain on the stainless barrels with AC loads than Power Pistol or factory loads.  No unburnt powder, though.

[The_Shadow]

Yes, I have seen that from the Winchester products as well.