What Barrel Length on Your Grendel AR(s)?

[StoneHendge]

55 was looking lonely down there at 26" so included my 6mm. I does just say Grendel after all.

[mdewitt71]

I used worst-case velocities we've been seeing with the newer Hornady 123gr SST lots of ammo.

123gr ELD-M seems to be faster like the old 123gr AMAX load. Supersonic range has the corresponding wind drift with it. 123gr ELD-M isn't the best bullet for long range, but one of the most popular and available, so I used that.

I used .255 doppler-based G7 drag model for the longer range figures with 123gr ELD-M.

I used .462 G1 for the "within 500yds" figures on the 123gr SST for hunting.

All figures are with 100yd zero, 2.5" optic over bore height, standard atmospheric conditions (59° F, 29.53" hg barometric pressure).

Another graph to look at would be weapon weight with pictograph diagrams showing weapon length and profiles.

Very very good info....... Came across this thread as you just got me drooling over your 12 inch build.
I think I might need to build me a 10- 12 pistol braced Grendel.

[jnr2233]

Very very good info....... Came across this thread as you just got me drooling over your 12 inch build.
I think I might need to build me a 10- 12 pistol braced Grendel.

The performance of the 6.5 grendel per the above table is impressive - I’m particularly impressed with the performance at 16 inches, however, I entered similar info into StrelokPro (using the hornady 123 sst from the cartridge database)and it shows the bullet going subsonic at between 850 and 900 yards. Am I doing something wrong?

[A5BLASTER]

The performance of the 6.5 grendel per the above table is impressive - I’m particularly impressed with the performance at 16 inches, however, I entered similar info into StrelokPro (using the hornady 123 sst from the cartridge database)and it shows the bullet going subsonic at between 850 and 900 yards. Am I doing something wrong?

He is most likely way more above sea level then you are.

Feet above sea level has alot to do with it.

[jnr2233]

Ok I didn’t think of that - I’ll take a look at that - thanks.

[A5BLASTER]

Ok I didn’t think of that - I’ll take a look at that - thanks.

Hey no problem glad I could help.

[grayfox]

His explanation below the graph says he is using standard atmospheric conditions... sea level= 29.53 inHg, 59* F.....

[A5BLASTER]

His explanation below the graph says he is using standard atmospheric conditions... sea level= 29.53 inHg, 59* F.....

Sorry didn't see that.

Just figured it was for the altitude he lives and shoots at.

[jnr2233]

His explanation below the graph says he is using standard atmospheric conditions... sea level= 29.53 inHg, 59* F.....

Ok I used the above pressure and temperature assumptions with the hornady 123sst at 2580 FPS muzzle velocity in strelok and it’s showing the round going subsonic before 900 yards. I’m using the “cartridge database” in strelokpro for the g7 coefficient. Not sure what could be causing the difference here.

[jnr2233]

Ok I used the above pressure and temperature assumptions with the hornady 123sst at 2580 FPS muzzle velocity in strelok and it’s showing the round going subsonic before 900 yards. I’m using the “cartridge database” in strelokpro for the g7 coefficient. Not sure what could be causing the difference here.

Interesting - I think the chart above might be somewhat optimistic.