5.56×45 Load Data

Volumes have been written about the M16 and the ammunition ran through it. I’ll add my two cents in here and there, but for the most part this is just a blog post to give reference data.

Powder: 28.5 gr of WC844 or 26.5gr of CMR 170 (H335 is canister grade WC844)
Bullet: 55gr FMJBT, G7 BC 0.122
Brass: Arsenal Brass
Primer: Milspec Small Rifle, crimped
Pressure: 50k CUP/54k PSI
Velocity: 3250 fps (20″ barrel) 15 feet from muzzle

Note: 54gr tracer bullets associated with M193 ballistic trajectory use the same charge of WC844. Also CMR 170 at 26.5gr or IMR 8208M at 25.3gr can be substituted.

Powder: 26.1gr of WC844
Bullet: 62gr SS109 type, G7 BC 0.151
Brass: Arsenal Brass
Primer: Milspec Small Rifle, crimped
Pressure: 50k CUP/54k PSI
Velocity 3050 fps (20″ barrel) 78 feet from muzzle

Note: 63gr tracer bullets associated with M855 ballistic trajectory use a reduced charge of WC844 at 24.7gr.

Powder: SMP842 (CFE223 may come close)
Bullet: 62gr copper with steel nose, G7 BC 0.166
Brass: Arsenal brass
Primer: Milspec small rifle, staked
Pressure: 62k PSI (HOT!!!)
Velocity: 3150 fps (20″ barrel)
NOTE: M855A1 duplication may not be safe in your firearm.

Mk262 Mod0 and Mod1
Powder: Non-Cannister Grade St Marks ball powder: Closest match I’ve found is PowerPro 2000-MR
Bullet: 77gr Open Tip Match with crimp groove (Mod1) or no groove (Mod0) G7 BC 0.190
Primer: Milspec Small Rifle, crimped
Velocity: 2850 fps (20″ barrel) 15 feet from muzzle
NOTE: Mk262 duplication may not be safe in your firearm. Much like the Mk248 Mod1 load for the 300 Win Mag, I don’t recommend duplicating Mk262 Mod1 as it is really hot, and frankly it isn’t necessary to get to that velocity/pressure level to get good long range performance from an AR. M855A1, Mk262 and Mk248 were intended for combat use, not reloading the brass.

Now, all of this is “interesting” but not really relevant to civilian interests unless you find that you have a rifle which really shoots a milspec load really, really well and you want to duplicate it. However, for hunting and target shooting there are better bullets available, even cheap 55gr soft points are going to be more consistently lethal than military ball ammunition because they have zero yaw dependency for wounding. The 77gr SMKs are a decent choice for target work, but are expensive which is why I shoot a lot of Hornaday bullets (just as good for what I need them to do).

I don’t know of any handloader that crimps in the primers to help handle the additional pressure of a hot day with a hot chamber, with temperature sensitive powder. This is why I don’t recommend duplicating M855A1 or Mk262 loads, they are loaded in virgin brass with crimped and staked primers for a reason. Black hills even started producing a safer version of Mk262 with a more reasonable velocity for the civilian market (good for them).

Always be safe in you load workup.


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2 Responses to 5.56×45 Load Data

  1. DW says:

    Thanks again for the reloading info.

    Reloading the 5.56 is usually a “cost / benefit analysis as we have standardized on the 55 grain xm193 cartridge spec. Usually we can find this in bulk for .30 or less ( generally buy federal ammo ), so if I factor in my time factor, bulk purchases are usually cheaper.

    But I have seen a number of write-ups, where folks have had good results with the 69 grain bullet. Have you had any experience with this bullet in 5.56?


    • rthtgnbs says:

      I have limited first hand knowledge of 69gr match bullets as I only ever went through a box of 100 doing load workups, but I know of at least one guy who made High Master with 69gr SMKs and an old Bushmaster 1:9 twist HBAR with chrome lined barrel. I sold off my 1:9 twist HBAR to fund other gun projects, so that ended my load workup with 68 and 69gr bullets. If you have 1:9 twist barrels, the 69gr BTHP is the best choice for long range accuracy. I now shoot 1;7, 1:7.7 and 1:8 barrels exclusively, so I use 75gr BTHP as my go to bullet for everything I load to magazine length.

      The 69gr SMK is a tangent ogive (the 68gr Hornady BTHPs are secant) so the 69s are a lot less “jump sensitive” for making a load that works in multiple rifles with different distance to the lands. The 75gr Prvi Partizan BTHPs are tangent ogive are great for 1:7 twist and 1:8 twist barrels, which makes them a better general purpose bullet than the secant ogive 75gr Hornady BTHPs for chambers with generous throats (a worn Wylde or a 5.56×45 chamber). Nosler 77gr Custom Comp and 77gr SMKs are also great for mag length match ammo if you have a 1:8 or tighter twist.

      The Sierra Accuracy load for the 69gr SMK is 25.3gr of Varget, although Hodgdon’s data shows that you can get more velocity and less pressure using H4895. Hodgdon’s load data for both powders is 24.0gr starting, 26.0gr compressed max, so it stands to reason that you’ll probably find a good accuracy node around 25.3gr of H4895. I use Varget now because it’s working out really well for me, but I wouldn’t hesitate to use H4895 either for a load workup.


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