45ACP SR4756 published values?

[alpining]

Hi all - I've been loading 45ACP 230gr RN (Berry's) with 7.4gr SR4756 (published max) and CCI 300 primers for about a thousand rounds (fairly heavy crimp, 1.250-1.260 OAL). I only just had them chronoed. They are shockingly low velocity, I think.

Fired out of a 5" barrel, five round average of 660fps. That's more than 200fps slower than several manuals say they should be.

Anybody else find this? I've heard that this particular powder had been lawyer proofed in recent manuals, but wow. I've always thought that the 7.4gr loads were soft, and there was the expected unburnt powder, but little sooting.

So, I thought I'd try pushing the envelope a bit last night. I tested up to 8.5gr of SR4756 before I noticed any pressure-related deformation of the primer (and those were very minor pressure signs, I think). That's about 15% over published max (of course, nobody should ever exceed published max). I haven't had a chance to chrono the higher charges yet, but all I'm hoping for is to make major power factor for IPSC (I want around 775fps with these bullets for comfortable clearance).

Anyway, I just wanted to check with more knowledgeable folks here to see if this was unusual. Maybe I got a bad bunch of powder or something. Any advice is appreciated, thanks!

 

[sevoman]

SR4756 is not a great powder for 45 ACP.I tried it once with lighter loads and got a lot of unburnt powder and wide velocity variations.Accuracy wasnt very good either.I just think that 4756 is a bit too slow for the 45.I like it in my 38 super with major loads though.

 

[alpining]

SR4756 is not a great powder for 45 ACP.I tried it once with lighter loads and got a lot of unburnt powder and wide velocity variations.Accuracy wasnt very good either.I just think that 4756 is a bit too slow for the 45.I like it in my 38 super with major loads though.

I found the same with low pressure loads. But as many others have noted, it works very well once you get the pressures high enough. I'm just surprised that you have to boost the charge so far above the published max to do it.

Can anyone else confirm that the published max charge weights result in significantly low pressure / low velocity?

 

[SUPERMAG]

loaded over 12 lbs IMR 4756 6.8 grns 230 gr RN cast and plated jhp as well ran around 770-810 fps for ipsc major power factor so somethings amiss??
supermag
was a soft but dirty load but also very dependable
my 2 cents

 

[squirrelnuttz]

I use 5.8 gr of 4756 for .45 ACP with 200gr cast SWC's.Tried up to book max load.It was always accurate, but had weird function issues with the higher end loads.....Accurate, dependable, dirty.A fair amount of unburnt powder.I fire 500-700 rds. between major cleanings.A wipe here and there, maybe a bit of oil on the slide, but that's it.No leading, but that's due more to proper boolit size.
I like that this powder is great for my slug/buck loads and the .45.

 

[alpining]

Thanks for the help, everyone. I can't figure it out why my pistol would give low velocities with this powder, and I don't want to have to worry about retesting every batch of powder just for the privilege of using this particular powder. Plenty of alternatives exist...

I'll save the rest of the 4756 for my 38Spl, and I'll switch back to Bullseye. Add me to the list of people who go back to Bullseye after trying something else, I guess!