Three years have passed with my .500 Maximum and what’s the old adage?
Time flies when you’re having fun.  The conversion has been a blast to shoot,
though my wrists and knuckles may disagree.   When completed in 2011 I
swore it wouldn’t be like those before it (I suspect a lot of Linebaugh Longs
are used sparingly in an attempt to save wear to the revolver and the
shooter).  They’re specialty pieces and I can’t argue that stance.  But mine
wouldn’t be pampered.  It was built to be shot hard, meter Blackhawk
endurance, and assess accuracy potential with bigger bullets.  And while
there's nothing magical about 1.60” x 0.512” brass, it has given me newfound
appreciation for big-bores.  Indeed, lessons learned call for an update to this
article.  My original treatment touched on durability and case life, but offered
limited anecdotal evidence.  I think 3,650 rounds is enough trigger time to
advance the subject.  What follows is an evaluation, or re-evaluation, of the
cartridge.  I’ll also grow the component base.
38.0 grains of AA1680 with the 525 WFN is my go-to load.  3,200 of the
aforesaid 3,650 were that combination and good precision was had at 25, 50,
and 100 yards.  Speed was also well ahead of the smaller .500 Linebaugh,
particularly as bullet weight increased.  But I’ve been unable to duplicate that
performance in recent months.  Here’s how it played out.  Initial
chronographing gave 1,325 fps, a figure recorded on two instruments using
new and 3x fired brass.  Temperatures were between 50 and 60 degrees for
both sessions, I fully understand atmospheric impacts.  In late 2013 I re-ran
the tests, again using cases on their third reload.  The numbers weren’t as
impressive, 1,265 – 1,280 fps to be exact.  I assumed the machine was off,
so I switched out the chronograph, repositioned the screens, and made no
change to neck tension or crimp.  Thirty shots showed the usual low spreads,
but none went higher than 1,280.  What changed?  The gun mic’d the same
on gap and the cone was still sharp and distinct.  I have no plausible
explanation, unless the first lot was fast 1680.  That jug dated to 2005, my
other 8-pounders shipped in 2011 and 2012.  Of course, 1,280 fps is solid and
the receiving end would never know the difference.  For the hell of it, I then
ladder tested in 0.5 grain increments all the way to 41.0.  A consistent 1,300
– 1,315 fps followed and the gun never winced.  Yet my ballistics software
says we’re over 40,000 PSI and I don’t recommend more.  I’ve heard of 525
proof loads to 1,500 and while the guns hold, longevity won’t.  I’m staying
with 38.0, there’s no reason to push the envelope.   
The .500 Maximum is a brutish round, capable of fine accuracy and diverse
performance levels.  Be that as it may, jaundiced attitude (ie, bigger is
better) cannot trump objective thinking.   At first glance, the Max looks like
the .50-caliber revolver champ (.50 Alaskan BFRs excluded).  But compare it
to the .500 Wyoming Express and it loses some shine.  The smaller FA 83
puts a 500 gr WFN at 1,270 fps and does so with lower recoil, far less
powder, and a compacted frame.  I’ve done the same in the JRH using
Leadhead’s 500 gr wide flat nose.  The only downside to the JRH is the brass
must be reamed for the longer shank.  Not so with the .500 WE.  With each,
the trade-offs are higher pressure and possibly reduced case life.    
The supply shortage of 2013 & 2014 forced me to try other powders.  
Regrettably, AA1680 is MIA at the time of this writing.  I’m down to my last 5
pounds and at 38.0 grains per drop it goes quick.  IMR 4227 is available so I
picked-up twenty-four pounds along with a jug of AA5744.  Top velocities
notwithstanding, they’ve matched 1680 on accuracy:    
Cartridge
Bullet
Powder
Charge
Velocity
Notes
.500 Maximum
435 gr WFN
IMR 4227
42.0
1,488
3" @ 50 yards
.500 Maximum
435 gr WFN
AA 5744
40.5
1,467
Max
.500 Maximum
525 gr WFN
AA 1680
38.0
1,275
Very accurate
.500 Maximum
525 gr WFN
AA 1680
41.0
1,310
40,000+ PSI
.500 Maximum
525 gr WFN
IMR 4227
37.0
1,232
<2" @ 50 yards
.500 Maximum
525 gr WFN
AA 5744
35.5
1,214
1.5" @ 50 yards
Could we gain anything from more weight?  You’ll recall my .500 Linebaughs
liked the 525 and weren’t lax on performance.   It’s my opinion that 435 is
medium in the 1.40”, 525 is the upper-end of heavy.  Anything below 400
grain is light.  That scale should be moved one increment to the right with
the .500 Maximum.  Meaning, 435 is light, 525 is medium, and heavy is...
well, a question mark until now.  In spite of the WFN showing good stability
to 100 yards, the nose isn’t ideal for accuracy beyond 50.   A Keith or LFN
should print better at that distance.  But that’s pure speculation and I strive
to keep my writing devoid of guesswork.  

Mountain Molds has an ingenious online application for designing your own
cast slug.  The software is simple to use and even provides a drawing of the
bullet.  I spent the better part of an evening with it drafting a dual purpose
50-caliber.  First and foremost, I wanted a heavy LFN style for my .50
Alaskan rifle; something to the tune of 600 grains.  I was also interested in a
longer nosed flat-point for my .500 Maximum.  Arbitrarily, I set 550 grains as
minimum with some must-have traits.  They include:  1) A pronounced crimp
groove, 2) A nose length that’ll fit my Ruger cylinder, 3) Wide lube grooves,
4) Adequate driving band height, and 5) A gas-check base.  After a lot of
fiddling, I created a 585 grain LFN.  The full spec sheet:
Sized
0.512"
Front band diameter
0.512"
Nose length
0.510"
Meplat percent
74%
Alloy
Linotype
Meplat diameter
0.378"
Crimp groove
0.090"
Ogive
Tangential
Front band length
0.070"
Base
0.469", GC
Groove angle
45 degrees
Base height
0.130"
Number of body bands
3
Number of lube grooves
2
Band length
0.098"
Overall length
1.202"
Groove C-to-C
0.196"
Lube weight
1.485 grs
Naked weight
569.4 grs
Sectional density
0.319
Diameter as cast
0.513"
Final weight
585 grs
I ordered a single-cavity, aluminum mold.  You can't go wrong at $75 and an
estimated four week turnaround.
Some photos of us casting the 585 Martin LFN using pure linotype:
Linotype is comprised of 84% lead, 12% antimony, and 4% tin.  Its melting
point is 475 F, so we held the pot just above 500 degrees.
A pyrometer was used to measure the melted lino:
We fluxed with Marvelux compound, left.  The right photo shows us
pre-heating the mold:
These were sized 0.512" and the gas-checks were installed on a Lyman 450
press.  I've tried many of the harder lubes, such as LBT, but still prefer
Lyman Alox.  It flows the best and isn't overly brittle.
100% linotype is around 22 Brinell.  Using a Carbine Tree hardness tester, I
checked the 585's post-cooling.  They gauged ~20, which isn't a surprise.  
Freshly cast tend to drop a little soft, then harden as they age.
Left - the naked 585 grain and it lubed and gas-checked.  Right - the 525
WFN loaded verses the longer 585 Martin LFN.
The normal host of powders propelled the new 585 Martin LFN. And I must
admit, expectations were low on velocity, say 1,100 fps.  Nonetheless, full
cases of AA1680, IMR 4227, and AA5744 put my 585 on the heels of Cast
Performance's 525.  In hindsight, this shouldn't have come as a surprise.  
Most of the added 60 grains sits outside of the case.  The 585's shank is just
a bit longer, so volume is marginally reduced.  Selected loads, all assembled
with large rifle primers:
I've only sent a couple hundred down range in the past few weeks.  But
accuracy thus far is as good, if not better, than the 525 to fifty yards.  And at
100 paces, I believe the heavier LFN has it beat.  Properly rested and with a
steady pull of the trigger, I can put five shots on a 10" paper plate.  Loading
the CP 525, it's usually 4 and if I'm really on, maybe five.  Here are some
targets fired with the 585 Martin.  Note the last one at 100 yards.  This came
close to my tightest 5-shot group at that distance with irons.  My previous
best was just under 3-inches using a 405 gr .45 Colt.  So much for excessive
weight and instability.
Cartridge
Bullet
Powder
Charge
Velocity
Notes
.500 Maximum
585 Martin LFN
AA 1680
35.0
1,233
2.0" @ 50 yards
.500 Maximum
585 Martin LFN
AA 1680
36.5
1,265
Maximum
.500 Maximum
585 Martin LFN
IMR 4227
32.5
1,216
Mild
.500 Maximum
585 Martin LFN
IMR 4227
34.0
1,248
3.5" @ 100 yards
.500 Maximum
585 Martin LFN
AA 5744
33.0
1,194
Low spreads
Case life - using .50 Alaskans as the parent, my Max brass has defied logic.  
The first batch of 100 were reloaded seventeen times before the primer
pockets went soft.  Subsequent runs equaled, and even exceeded that
count.  Accuracy didn't suffer as the shells work-hardened and neck purchase
didn't fade.  I'm working on an article that'll analytically approach cartridge
brass and resilience.  Look for it on this site in the coming months.
I doubt this piece will motivate the casual reader to commission a .500
Maximum build.  If you’ve thought about owning one though I hope it’ll dispel
some of the myths.  My only goal is to provide an unbiased review of the
cartridge.  I’ll also periodically post updates on my conversion and total
round count.

If you’ve enjoyed this article I highly recommend Max Prasac’s “Big-Bore
Revolvers”.  It can be purchased by clicking the cover image.  Max is a close
personal friend and I was fortunate to be part of some of his testing.