XM256, XM256E1 question


#1

Weights are for the full cartridge.

I have one FA65 that weighs 310.2 grains. Believe this to be XM256
I have 3 FA66 that weigh 316.4, 316.5 and 319.2 Believe these to be XM256E1 but what’s with the heavier round?


#2

Jestertoo, and for the rest of us: what caliber is being talked about???


#3

Sorry ! 7.62x51


#4

According to HWS III:

The initial reduced recoil XM256 cartridges used the forward 82-grain projectile (FAT 92) from 7.62mm NATO duplex rounds. These were loaded into ⊕ FA 66 cases.

Accuracy issues arose due to the cavity in the back of the FAT 92 projectile, so they made a projectile without the cavity which weighed 90 grains. Cartridges with this projectile were designateed XM256E1. HWS indicates that these were loaded into F A 6 6 cases and at least one pilot lot was loaded into ⊕ FA 67 cases.

Both projectiles were also tested with aluminum cases.


#5

My bad. The lighter weight is FA 66, the heavier ones are FA 6 6. Thanks for the correction.

Any idea as to the almost 3grain difference in the later version between the two at 316 and the heavier one at 319? No outward differences.


#6

I’ll have to dig my examples out and see how they compare. Off the top of my head I don’t have an explanation for the difference. I have no idea what the manufacturing tolerances were for the various components, although 3 grains would be about 1% which seems a little high.


#7

For what it’s worth, my ⊕ FA 66 round weighs 310.6 grains and my F A 6 6 round weighs 315.6 grains.