AR10 FP Spring

[Razorhunter]

Why is there a FP spring in an AR10? Why not in an AR15? Been wanting to ask this for a while.
Has there ever been a successful AR15/M4 design, which used a FP spring, as the AR10 does?
Finally, do ALL AR10 variants (SR25, etc), use a FP spring design?
Thanks guys.

[Tspeis]

Why is there a FP spring in an AR10?
To reduce the possibility of slam fires or drop induced discharges.


Why not in an AR15? Been wanting to ask this for a while.
Don't know. My guess would be the heavier weight of the AR10's carrier may contribute to increased bolt/carrier velocity, thus increasing it's chance of slam firing. Just a SWAG on my part though, take it for what it's worth.


Has there ever been a successful AR15/M4 design, which used a FP spring, as the AR10 does?
Yes, it's called the HK416. :D In addition to the spring, it also has a spring loaded firing pin safety.


Finally, do ALL AR10 variants (SR25, etc), use a FP spring design?
I believe many have free floating firing pins just like the standard AR. Maybe someone else could chime in on this one.


Tspeis

[Robb Jensen]

Why is there a FP spring in an AR10? Why not in an AR15? Been wanting to ask this for a while.
Has there ever been a successful AR15/M4 design, which used a FP spring, as the AR10 does?
Finally, do ALL AR10 variants (SR25, etc), use a FP spring design?
Thanks guys.

The AR10 has a longer and heavier firing pin vs. that of the AR15. The spring is used to reduce the possibility of slam firing.

.223 firing pins are much lighter and almost all .223/5.56mm ammo has hard enough primers to prevent slam firing. FWIW the HK416 has a firing pin safety.