Probably the most anticipated powder in the last 10 years or more to come out.   Here is some opinions on it:
  • Compressed loads, pretty much no matter what bullet you choose from 75+ grain
  • You either have medium compressed, or very MEGA compressed if you want higher velocity
  • Due to very high compression, we think SD and ES are varying, probably due to crushed powder and varying OAL.    Some bullets started creeping back up after seating, because it was well over 100PSI to seat almost everything, even loads over 1 grain under max
----Design thoughts
  • Not ideal for 223, no way.  But that is subjective to some, but to us, its for sure.  When you load way under max, even 1.5 grains under max, and you have to compress the bullet over 100 PSI to seat it, that is not ideal and that itself causes issues.   Ideal for 223, we think is like Benchmark, N135, N530, AR Comp and in that area, some would say XBR8208 and H4895 are right in sweet spot along with the others.   N140, Varget and RL15 are all good around 24 and they are not efficient to use for lighter bullets, lower performance .  
  • RL 15.5 is not well suited for 223, but that doesn't mean its not a great powder.  Its just not great for 223. It will be great for larger case cartridges like Valk, and Creed, 6MM, etc.  Where you don't have mega compression.  We will test Valk next, it will do a lot better, we are sure.
 Lets see some results.  Maybe they will sell us....
P.S.  Alliant.  We LOVE your company, you have so many top tier powders.  Reloader 13 is what we need.  In between RL15 and AR Comp, but TS technology!  So basically, 23.5-23.8 grains would yield 2750 FPS in a 20" barrel using 77 SMK @ 2.260.   Or if there is a way to use TS, but less bulky, like benchmark for example, then around 24.5-24.8 grains to hit 2750 FPS would be ideal area.  You probably think that is a waste of time, because AR Comp is so close.  Basically RL13 would be .5 grains slower.  Hardly worth it.  Or just come out with RL15X and have that the TS version.  Same load data as RL15.  But please, make granules same size as AR Comp and RL15.  I absolutely HATE powder dropping RL15.5 and RL16.  They get stuck in the drops, and then spills all over. I can't stand it.

Reloder 15.5 Testing
We wanted to make this test thorough, so we baked up a bunch of top tier components, prepped it professionally, then used basically the best equipment money can buy to assemble it.
Lapua Brass
Looks like magazine picture, but that is actually one of the exact cases in the test
We live inside the Lapua factory, part time

Arbor Press with neck tension guage
Wilson Micrometer chamber style die
Federal GM Primers

Some Bullets used in test
Nosler 77 Grain CC (3rd left)
Sierra 77 Grain Match King (mid)
Berger 77 Grain OTM (3rd right)
Sierra 80 Grain Match King (2nd right)
Berger 80.5 Full bore (right)
Nosler 85 grain RDF (not pictured)
Some mag length...some not
The long ones on the right are Berger 75 Grain Match, which are too long for magazine length.  They hit the lands of this Shilen at 2.413.  So we loaded them to 2.400 OAL.  And single loaded them to allow for maximum capacity of powder with

We neck turned it all
Typical neck thickness for Lapua 223 match brass is 13-14k thick at thickest point, generally.  We turn it so is around 12k uniform all the way around, with give or take about .0004, or 4/10 of 1 thousands. 
Reloder 15.5
Some ladder test using Berger 77 OTM and a Wilson Chamber die.   Bullet run-out was less than .001 on every single one.  Most were under .0005  Despite this, SD and ES were all over the place, and this is brand new, batched, Lapua brass with Federal GM 205M primers.

This was really just to understand what area of load generated around what velocity.  Then you can see, we tested:
RL15  24.3 Grains = ~2780 FPS
RL15.5 24.3 Grains  = 2680 FPS
RL16 24.3 Grains = 2450 FPS

RL15.5 is way closer to RL15 than RL16.  But its super bulky like RL16, and looks the same as it.  RL15 has much smaller granules, like AR Comp and you can fit more into a case, and more easily compress loads with it.

Norma Brass
Only a few groups under 1 MOA.  And this is a match Shilen Barrel, from WOA.  Very accurate barrel.

Norma brass has very high case capacity because its 1.750 long, but it only weighs 90-91 grains, it has internal capacity of over 31 grains.  And you can see from pics below, its quite large internal space for  223 brass
RL 15.5 Data

We didn't shoot all the groups on this paper, so some targets are blank. 
23.4 RL15.5 with 77 SMK best one

AR Comp thrown in, same lot of prepped brass.  Half inch and .67 inch groups.  Just to show its not gun, etc.

Of note, the target on the right, the Berger 75 Grain Match VLD, with 24.5 grains, was .5" range and best group for RL15.5 so far.  That was also near 2750 FPS. 


This is an advantage over a normal die, is that a Wilson Chamber die will allow A LOT more pressure seating and still doesn't leave an ogive dent.
Neck Turned

Lapua Brass
(how much RL15.5 fits in Lapua case)
Starline 223 brass
(how much RL15.5 fits in Starline case
Another shot
Neck turned brass, with RL 15.5 to the top
Norma Brass
(how much RL15.5 fits in Norma case)
Super bulky
This is what all the case measurement fills looked like.  You could argue you could fit 2-3 more granules in there, but it would stick over top barely. 

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