462, I heard that and saved up a bunch of same headstamp SP .45 brass and tested several
loads. I could see zero difference in accuracy. And since I have probably 5-6K of LP .45 ACP
brass, I find the SP stuff a real irritation. Maybe with a careful enough test, there might be
something to find, but if so, I think it is very small or non-existent. I think the ammo makers
somehow save maybe 4 cents per 1,000 rounds loaded and so have gone that way in some of
them.
Over the years, I have periodically sat down and loaded up different bullets, brass, powders,
and powder charges (to a smaller degree, since I want full power ammo mostly) and tested it
repeatedly in multiple 1911 guns.
For MY guns, I have found that most of them do their best with R-P brass, 452460 or H&G 68, sized
to .452 (even though for a LONG time commercial H&G 68s around here were sized to .451, take it
or leave it, and leaded very slightly) and lately I have been trying different primers, although not too
systematically. I need to sit down and do some five five shot groups of each primer in rotation
with some of my more accurate guns and see for sure. At this point I think Rem 2 1/2 primers are doing
a bit better with my standard 4.8 TG load than my most common choice for the last 30 years, the
CCI-300. I have done some tests with Fed LPs and from other's reports, expected improvements
with some specific tests. So far, Fed LPs have shown me nothing special. I have tested .451 and
.452 diameters, since most of my .45 ACP barrels slug at .4515 (amazing over decades of time
and multiple companies to hold that tight). .452 wins, but .451 is not horrible. Another design
that is quite accurate is the MP200 HP, basically a copy of the 452374 Lyman with a HP. I haven't
shot enough of the 374s for accuracy to have an opinion on them, although they sure load nicely
into a 1917/625 in moon clips, and will feed well in any gun. I have found no issues ever with
H&G 68 in any gun made since the early 80s because they have the mil std Colt absolutely square edges
of the chamber on the sides ramped. All guns that I have seen, from any maker since about 1980
have been good to go with H&G 68s, IF YOU TC them properly as a separate operation! Key
issue, there.
Preferring R-P brass today surprised me, because early on, in 1980 when I started with .45 ACP
in quantity, the little bit of range pickup R-P brass that I had seemed to have thinner necks
and I seemed to get less neck tension. I had yet to really work out the need for TC as a separate
operation as a crucial step in loading for reliable ammo, and got it in my head that WW brass
which I had more of, was somehow better. That idea persisted until about 2003 or so when I sorted
out a bunch of different brands, Fed, WW, R-P, Starline (which I expected to win) and loaded up
a BUNCH of each and shot the heck out of it in 3-4 different guns, my more accurate ones.
I was surprised that R-P consistently beat all of the others by a substantial margin. Retesting
couldn't make it go away, so I gave up and bought 1000 new R-P and now sort my brass every
so often to put R-P in bins by itself, all others mixed. I have a bunch of new Starline still, and
respect it greatly, but it hasn't been quite as accurate in this caliber for some reason.
I have seen nothing so far that makes me think the SP .45 ACP brass is anything but what Brad
pointed out, a PITA to have accidentally mixed in with your brass at the range. I don't scrap
them, but they get put aside for "after the EMP or zombie apocalyps" or whatever.
Bill