01-21-2022, 02:22 AM
(This post was last modified: 01-21-2022, 02:38 AM by r.tenorio671.)
(01-20-2022, 07:27 PM)dave_the_ss Wrote: Just finished my 6mm arc build. I chose to run 70 grain nosler varmageddon bullets. With cfe223 (it’s what I have and easy to find)
Max OAL is 2.090 I loaded to 2.094 cause I had so much jump.
My jam is 2.230
Is that way to much jump for an ar?
If I increase the OAL is that going to cause pressure To go up or down?
I fired a few rounds today to check pressure and have no pressure signs. And cycled just fine. All the way to max load data of 33.0gr.
Now I’ll put my thermal on and go sight in and shoot for accuracy
....bullet profile & magazine internal length have the most influence on attainable COAL in regards to MAX COAL.
...an increase in OAL may decrease pressure, but not always.
...when increasing OAL, just ensure the seating depth has sufficient bullet in the neck.
FWIW, excellent "performance" can be obtained at multiple jump distances, it comes down to testing....each barrel is unique. I have the same bullet loaded up for testing and my data is CBTO 1.6415 / COAL 2.1215. With these measurements these rounds fit easily in my Duramag & E-Lander mags and chamber & extract from MY barrel's chamber with no issues, and have sufficient bullet in the neck for retention. Pre-installation measurements of MY barrel had these bullets registering a max COAL (touch-point) 2.2246 and the CBTO being 1.7061 at that max COAL.