Re: 6.5 Grendal
The 6.5 Grendel, and 6.8 SPC both shoot bullets of around 123 grains, and at about 2550-2600 FPS. That is of course a generalization and of course, there are different loads for both rifles. However, when comparing similar weight projectiles, both rounds have a similar enough velocity that I doubt any human or animal would be able to tell much difference inside of 300 yards.
The much higher BC of the Grendel's bullet means that after passing 300 yards, the Grendel's performance begins to improve markedly compared to the 6.8 SPC. The Grendel will loose velocity more slowly than the fatter 6.8 bullet.
However, the 6.8 does have advantages too... The Army marksmanship team has found that when they compared the 6.5's 123 grain bullet and a 30 caliber 123/125 grain bullet at the same velocity, the 30 caliber bullet has less recoil. As a result, the Army has started using a short 30 cal round for much of their 3 gun matches. This principle will also apply to the 6.8 bullet, but of course to a lesser extent.
I am a true Grendel fan, but realize that either round has it's benefits and limitations. I wanted a round that would perform accurately well past the limitations of the 5.56 bullets, and the Grendel gave me exactly what I was looking for. My 123 grain Scenar bullets at 2550 FPS easily remain supersonic past 1000 yards. The bullet will do fine for punching paper, or tagging a piece of steel at 1000 yards. However, I do not think it would be ethical to shoot at game with the Grendel at those distances simply because I think I might be able to hit it. The Grendel's remaining energy at 1000 yards is simply insufficient for ME to consider using it on game at that distance.
I would be completely comfortable using the Grendel (with a bullet designed for game) on deer sized animals at lesser ranges though.
I have tried 24, 19.5 and 18 inch Grendel barrels. For me, I think the best compromise barrel is one around 20 inches. A barrel of that length allows the case to develop sufficient velocity without being too long and awkward.
When people keep in mind that the Grendel is really what I would term an intermediate cartridge, it can be very useful. For shooting at game at extended distances I think that I would like to move to a case with a capacity/performance of at least the 7.62x51 or larger.
A previous posting asked about where to go for a barrel for the Grendel. I understand that Alexander arms recently came out with a number of different barrel profiles. If I could choose any barrel, I would buy a light to medium weight, 20 inch fluted barrel and mount it with a tube for-end. I think that a slim to medium barrel with fluting would give excellent balance, accuracy, heat dissipation, and sufficient velocity.
Alexander arms also has a number of other really interesting barrel profiles and lengths, so they should have just about anything you can imagine. And they have these barrels available in a number of different quality levels.