M&P 15 Volunteer XV Pro M-Lok & The 6mm ARC Seconda Parte

03/05/2023 – “Yesterday”, and the rest of the 1965 Paul McCartney lyrics that follow, express the day. This scene was a black top driveway, patches of green lawn and woodland. The town was out posting roads in anticipation of spring thaw. The daytime temperature was 40°F. But that was then and this is now; nature expressing its perspective on humans controlling climate.

For me, good news – bad news. The good news is that I get to play with Skippy and Chuck II, respectively, the 1025R John Deere tractor  with 54″ snow blower and the Cub Cadet 420cc 3X walk behind. Yes, there will be some judicious shoveling, but that means I can skip a work out day. Yippy for me.

The bad news? The range outback looks worse than the picture and short legs, deep snow, is never a good combination. So I will not be able to wrap up this project, with reliable and well tested data, until I can clear a path to 100 yard targets. Right now, the schedule is for Tuesday completion. In the mean time, I thought I would share what I have so far concluded.

Flexibility…

The 6mm ARC does bring increased lethality in comparison to the 5.56 NATO powered AR 15 whether for security or hunting applications. The cartridge case and gas system capacity is there, so all that remains is appropriate bullet selection.

*Under SAAMI minimum cartridge overall length spec.
**Remington in name only. A green colored Hornady V Max
***Exposed cannelure
**** Sorry, I was on a roll and couldn’t help myself

And then…

Headspace was checked with each bullet and, from this aspect, there was plenty of clearance from rifling: 0.050″ Berger VLD Hunting, 0.040″ for the Hornady ELD Match, and a whopping 0.100″ for the Berger VLD Match.

So the gating item for cartridge overall length was AR magazine standard, which set maximum cartridge length at 2.260″.  As a point of reference, the Hornady 108 grain measures 2.255″. There were no feed problems even at 2.260″.

I decided to test, particularly bullet weights and charges with the initial bullet selection, but to overhaul the list for the final set. The problem is that I have had excellent results with all of them , they are all good quality, but a number are wrong for the application.

I realize the cartridge can deliver deer dropping power at 500 yards, however, hold over beyond 300 yard is significant and that performance is with match bullets that do not have proper construction for hunting medium size game. Focusing on hunting and a self imposed 300 yard maximum range, I do live in the woods, boat tail bullets and match bullets are not useful.

Boat tail bullets sharpen the ogive to a lower BC by shifting weight to the heel. Within 300 yards, there is barely a streamlining benefit and the rear projection takes away case powder capacity. So my preference is for a flat base bullets, even at the expense of a fatter ogive.

I don’t like exposed cannelures on bullets. Not a functional problem, these bullets were collet crimped, as much as an aesthetic eyesore. It is evidence that these bullets were intended for a  different cartridge. In this case, the 243 Winchester and 6mm Remington. Seating deeper to the cannelure would tax already limited case capacity and, in this case, they are seated to the respective manufacturer’s recommendations for the 6mm ARC.

The data and testing will be completed and published next week, as some people may disagree with my logic and find the load data useful. It has been known to happen. Then a new bullet list will be generated and that data will be published. Some folks might agree. It has been known to happen.

Going to take off. If snow removal doesn’t begin before 5 AM, the forecasted temp spike will turn this mess into a snow cone sea and I will be stuck here until the thaw.