Did I just email you on this topic?Originally Posted by El Cid
If not, crazy coincidence, but I'll repost here what I recently had to say on the matter:
*NOTE: "MRAD"="MILS", I just prefer the technical accuracy of "MRAD" over "MILS" in writing.
Distances in yards. Projectile weight in grains. Projectile velocity in feet per second.
Comparatively, a 14.5” 6.5mm Creedmoor will show about the same drop correction as a 20” 7.62 shooting 175gr ammo, but with about 1/3 less wind drift inside 800 yds. The 6.5 projectile is also way less affected by trans-sonic (and trans-sonic happens at a further distance), making those longer pokes easier. That’s mostly applicable to those that carry a 20” 7.62 rifle that meets their range requirements, as they can go to a significantly shorter and lighter system and meet or exceed their current performance.
Personally, I really like 16” for 6.5 CM, not only for avoiding NFA hassles, but also for the velocity gain over 14.5” barrels.
Once you go past 16”, I’m just not seeing the benefit to the weight and length until you hit about 22”. With a 22” barrel I will be in the 2750 ft/s area with 140gr Berger AR Hybrid projectiles, which is really the next step up in practical performance over the 2500-2600ish ft/s of the 14.5-16" (projectile and load dependent, of course).
My 16” shooting 140s will show 10 mrad of drop at 1,000 and 2 mrad of wind correction for a 10mph wind from 3:00.
22” will show 8.7 mrad of drop and 1.9 mrad of wind.
20” 7.62 with M118LR will show 11.6 and 2.8
16” 7.62 with M118LR will be 12.8 and 3.0
My 16” is a 5mph gun out to 800 (+.1 at 900 to 1000, +.2 at 1100, and adding an additional .1 sequentially past that)
My 22” is a 5mph gun out to 1,000 (+.1 at 1100 to 1200, increasing by .1 every 100 yards past that)
That 6” of barrel difference is needed to get any useful gain in performance for wind or drop.
When it comes to speed drop, my 16 is 1.8 (covers 300 to 650 with .2 error) 22” is 2.1 (covers 300 to 800 with .2 error).
For ranging error, I’m 0.5 mrad difference between 800 to 835 with 16”, and 800 to 840 with 22”.
For midrange center hold, putting 1.5 mrad on the gun will cover 295-365 with +/-0.3 mrad error with 16”, while 1.3 on a 22” will cover 295-380 with +/- 0.3 error.
For midrange dial/hold patterns; with the 16”, dialing 2.1 mils onto the gun will make the center crosshair 400, 1 mrad will be 500, and 2 mrad will be 600, with a 0.1 error between 400 and 600 –OR- dial 3.1 on and hold under 1 mrad for 400 and over 1 mrad for 600.
22”: dial on 1.8 mrad and center will be 400, 1 mrad=500, 2 mrad=600, 3 mrad=700 with a 0.1 mrad error -OR- dial on 2.8 and hold under 1 mrad for 400, center for 500, 1 mrad for 600, and 2 mrad for 700.
From comparison, the 14.5” 6.5 will be a 4.5 MPH gun to 800 yds, will show about 2.3 mrad of drift from a 10 mph wind at 1,000 yds, speed drop is 1.6 (250 to 520), ranging error is 0.5 mrad difference between 800 and 830, 1.7 dialed on will cover 295 yds to 335 yards (+/-.3), and dialing on 1.5 mrad will give center for 300 yds, 1 mrad hold over for 400 yds, and 2 mrad hold over for 500 yds.
Anyway, at least that’s how I see it.
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