6.5 Grendel

[soulezoo]

I have a stripped lower that I was going to build a 6.8spc on... after reading more on the ballistics on the 6.5 grendel, I think i am going in this direction. Both the 6.5 and 6.8 use the same effective bullet weight ranges (roughly 113gr to 145gr) so really the only consideration is performance. Due to the very high BC of the 6.5, it is actually more effective downrange than the 147gr .308 loads. Very interesting.

The only thing I can see that may be a concern is effective feeding at high fire rates due to the fat case of the round.

Does anyone have practical experience with this round?

[Redleg]

I haven't fired them yet, but have been researching a build-up myself. Normally the Grendel is for longer range and probably not intended to be used in rapidfire. The 6.8 is designed specificly for CQB knockdown and rapid fire. It sounds like you're looking for a distance shooter? I'd get the grendel too.

[soulezoo]

Well I am thinking this way: It is clear the grendel far outperforms the spc at range. So swinging the argument back to CQB, it would seem the two rounds being of similar weight and construction, similar MV and only a whisker of diameter difference that effectively is no difference at all will perform similarly given identical rifles and conditions. So, the only thing left to consider is functionality and logistics.

It seems that as long as either round will feed flawlessly as fast as I can pull a trigger (semi auto constraint) you have to give the 6.5 a first look.

Both rounds are currently difficult/expensive to source... although the SPC has an advantage here. Both will carry the same rounds in a magazine (28).

So what am I overlooking here that would give the 6.8 a greater advantage?

[Equalizer_2]

This info may come a little late but go over to http://www.68forums.com/, sign up and browse. The 6.8 now has a 85 gr bullet doing 3000 fps from a 16 inch barrel and is only down about 68 inches at 500yards with a 100 yard zero. Of course a longer zero will have a large impact on the trajectory.

The 6.5 has a better selection of high BC bullets as there are a lot more 6.5 caliber cartridges but only two or three in 6.8/.270 caliber so fewer bullet choices.

As for ammo manufacturers there are two known for the 6.5 and at least eight for the 6.8 SPC. There is a group over at the above site that have put a lot of work and research into the 6.8 and it is starting to pay off in terms of performance.

There are also more bullets becoming available for the 6.8 and some of them have impressive velocities and trajectories.

The 6.5 is an impressive round but its true potential can only be realized in a bolt gun due to pressure limitations in an AR. As for full auto cycling I have not seen anything for the 6.5 but here is a short one showing the 6.8 in full auto http://dealervids.com/FSC30.wmv

[Adaminak]

Originally Posted by soulezoo

The only thing I can see that may be a concern is effective feeding at high fire rates due to the fat case of the round.

Cyclic rate of fire is contrained more by the design of the weapon than the round it fires. Granted short, light rounds chamber quicker than long, heavy rounds which is why the MAC-11 shoots a 380 ACP at 1200-1300rpm whereas the MAC-10 shoots the 9x19 at "only" 1100-1150rpm.

The basic design of the M-16/AR-15 is sound. In a purely hypothetical situation, if you should ever convert one to fire from a belt or an endless drum magazine, the cyclic rate of fire for the platform is 900-950rpm, which is at the top end of closed-bolt weapons. There is absolutely no way for you to pull the trigger faster than the action cycles. So long as the cartridge is roughly the same length as the 5.56mm, any weight variances are corrected by the magazine spring and any bullet ogive variances are handled by the feed ramps. To put any fears aside, Alexander Arms also sells a full-auto version of the .50 Beowulf, and it's significantly fatter and heavier than the 6.5 Grendel.

If it were my gun, I'd chamber for the 6.5 Grendel and start reloading in earnest

[n2moto]

Will the 6.5 fit in the ar 15 platform or do you need a ar10?

[soulezoo]

regular ar 15 platform. you just need a 6.5 upper receiver assembly and magazines. It uses a common lower receiver.