If I hadn't seen this set up, I wouldn't say it would work but it does. The ogive is slightly below the case neck correct, but most of the neck is holding the bearing surface of the bullet.
In the 200+ rds I have seen fired, there were ZERO issues, no bullet set back and plenty of accuracy. HK SL8 approx 1.5 MOA at 1000yds. This is definitely one of the most accurate semis I have had the pleasure to shoot and see shot.
Also, with a load of Benchmark, there is precisious little room in the case for the bullet to set back. It is very close to compress.
It is a myth that jacketed bullets don't work when seated below the neck shoulder junction. Every single 300WM factory load has the base/boattail of the bullet well below the neck.
No one has announced any trouble in how many decades?
The load data I have suggested is lower then what is achievable in a bolt rifle in light of the needs of a gas rifle. Considering the performance that match AR rifles are reporting, the performance I suggest is well within reason.
Isn't 5.56 NATO ammo speced at higher pressures then 223? maybe we don't need to ease up for the AR????
Whether factory ammo is available doesn't concern me cause I reload for everything and find the best performance/accuracy that way.
I have already agreed that the 6.5 will deliver a bigger hunk of lead down range. There is no dispute on that but this was a ballistic comparison.
As for a light bullet zapper, the SAAMI on a 55gr Vmax is 3380fps. So let's say 3200fps out of a 20" AR. No issue with OAL, etc.
Sure it will get bounced in the wind more then either of the above but it will go nicely to 1200yds. Yep, watched the trace all the way out.
How about the 70gr Berger VLD. That'll fit
Comparing modern 6.5 VLD bullets to stubby JFK era bullet designs is also an unfair comparison. If you wish to compare POTENTIAL, then give them both an equal shake.
Modern 22cal VLD's are pretty amazing and when fed in gas guns will up their performance HUGE.
By the way, the 77gr MK is a stubby non VLD design. With one of the lowest, if not the lowest BC of this class of bullets.
Jerry
PS Isn't there problems with bolts breaking in Grendels?