05-29-2022, 10:57 PM
(05-29-2022, 08:40 PM)Dino11 Wrote: If you are using metal mags some of them let you load COAL as long as 2.300. Most of my AR 6 mm ARC's are loaded to 2.295 giving me about .055 to .060 off the lands on most of my gasser stuff using secant olgive bulletts. These bullets have a long slender profile to them and tend to have large jumps. Now if you take the Hornady 105 and compare it to a Noster or Berger 105 you will see what I'm talking about. You have to load the Hornady at no more than 2.200 to 2.220 or you will push it into the lands.
....true, bullet ogive does make a difference. In my barrel the Berger 95 Classic Hunter (hybrid) -vs- the Berger 95 VLD Tgt (secant), there is a 0.1313125" difference in their "touch point" when COAL is measured (2.197" -vs- 2.328") and thier CBTO's were 1.730" -vs- 1.726" respectively.
I found the articles you referenced to be interesting and enlightening on the common findings of large jumps, especially since the SAAMI chamber drawing indicates that there would be a 0.0899" freebore length in a SAAMI compliant chamber. Buying an off the shelf/online barrel makes how exact that dimension is somewhat of a "spin the wheel" prospect.
...large jumps will be the default in gassers, IMHO, only because of the SAAMI freebore spec AND the 2.260" 'standard' for magazines, regardless if a particular mag brand/model gives a little more room. I've seen enough posts in multiple forums where folks encountered feed issues when they exceeded the 2.260" COAL, be it the COAL or influenced by other factors (feed ramp, mag fit/height, etc.). It was more prevalent in "mix & match" of upper and lower brands.
...I want to simplify my reloading process so I'll stay within the 2.260 limitation and work the powder charge and minor negative seating depths to find the widest "forgiveness" band. Since I picked up 500 107 SMK's, those will be my focus for the time being.