Here's my first update on the Berger 77gr OTM Tactical .224 bullets. Three ladder tests were shot today via my long range .223 Carbine. The gun was not zeroed for these rounds so I have no data on the drop at the specific distance. I simply arrived at the shooting location and confined hits with my lowest charge weight with 10 rounds that I used to come to a working temp and confirm hits at 330 yards. Then the three ladders were fired with 15-20 mins between strings. My rifle build is as follows:
20" Criterion 1:8" barrel with 5.56 Match chamber rifle length gas system almost shut down with a Syrac block because of the suppressor. I'm one click out from closed as it will go and all cycles without fail. Vltor upper with a HDMR scope and SAS Reaper suppressor attached. All shots fired from a sandbag setup and rear bag.
77gr Berger OTM Tactical bullets
Lake City 07 matching lot brass FL sized with shoulder bumped 0.003 from prior firing in this chamber
Federal Gold Metal Match AR Small Rifle Primers
H4895 powder thrown from Hornady Lock and Load Auto Charge with weight confirmed on a GemPro 250 to 0.04 grains of target
Loaded to a COL of 2.255" (0.015 jump to lands)
All rounds fired over a Shooting Chrony F1 Master 8 feet from the muzzle in the following weather: 64.2 degrees, 6811 DA, 5177 Altitude, 24.72 Absolute Pressure. Wind was 8-15 MPH at our 8 or 12 o'clock depending on the string.
The three strings were with powder loads from 20.6 - 22.4grs in 0.2gr steps. The data provided from Berger stated that the max load for this combo is 22.1 which should net 2799 fps from a 24" barrel. The Hodgdon provided data states that a max of 22.6grs with a Sierra 77gr should net 2727 fps.
The lower charge weights resulted in very low hits within the ladders but had an ES within the same charge weights of as little as 2 FPS amongst the 3 ladders. The lowest charges resulted in velocities of as low as 2363 fps. As the speed picked up the ES opened up some but even the hottest load had an ES of 14 fps between same charge weight between the 3 ladders. The first ladder was disregarded for accuracy because of my issues as a shooter. The last two ladders resulted in the hottest 4 rounds landing within a 1.5" group at 330 yards which equates out to 0.45 MOA for that 4 shot group of 4 different charge weights. The interesting thing was that the charge weights 22.0 and 21.8 had a velocity that averaged 2530 fps and the charge weights of 22.2 and 22.4 had an average velocity of 2590 fps so not even close in velocity but they were landing in very close proximity despite the velocity. The fastest velocity seen was 2600 fps from the 22.4gr loads.
NONE of the cases showed any signs of evening being near the pressure max. My next part of the workup with be additional ladders loaded at 22.0 - 23.0grs at 0.2gr steps to attempt to confirm a max load. My suspicion is that the hottest load I tested today is likely at the middle of an accuracy load but I'd like to confirm that.
Unfortunately the the Berger data was not correct or I would have loaded hotter rounds to take today and the testing would be pretty much done. The Hodgdon data appears to be on target for what I'm seeing from my gun. I'll be back out again next week to run the next set of ladders. The results were pretty impressive considering the 4 hottest loads were coming in so tight with the different charge weights being used but I'd like to get more velocity from these for my final load. We'll see what happens.
Any suggestions as well as other's data on velocity with these Bergers from a similar build would be helpful.
Thanks
