Varying The Oal In A Load For A Semi-auto?

[Religious Shooter]

Went to the range looking for an OCW for A2230C and 55 grain Win FMJBT. I think I found one or two possibles. (For those who care I got 25.9 grains and one somewhere between 25.3 - 25.6 grains. The lower charge had a smaller elevation change --- delta of 0-.5" vs. .5-.6". But I'm going with the 25.9 due to the greater velocity --- flatter trajectory and more wind resistence.)

I guess the next step was to vary the OAL. Is this step necessary given it is for a semi-auto (AR15)?

For those who have varied their OAL for their ARs what kind of group reduction did you get?

I really, really, REALLY hate load development. But I will go do the OAL thing if it nets me a .25"+ gain without sacrificing reliability. If it's less than that... I'm gonna blow it off.

[milanuk]

If you are shooting from a magazine, i.e. pretty most normal applications of an AR outside of the Prone Slow Fire stage of an NRA High Power match... I'd seat to an OAL of 2.250-2.260" depending on your tolerance for magazine hiccups (i.e. I seat a little shorter to give a tad more clearance in the mag) and call it a day. If you are shooting in a venue such as mentioned above where single round loading is the only acceptable way to load the gun... then it usually is a worthwhile pursuit to measure the distance to the lands and seat the bullet out accordingly. Hint: OAL is not the correct measurement to be using for this... bullet jacket lengths can and do vary, upwards of 20 thou or more. When trying to get w/i 0.005" of the lands or less... that don't cut it. Measure off the ogive, and to hell w/ the OAL. Normally this is done more w/ the longer bullets like the 75gr A-Max, 80 & 90gr SMK's and similar VLD designs, and helps reclaim some of the limited case capacity present. Using 50-55gr bullets... I honestly wouldn't bother, personally. YMMV.

HTH,

Monte