I’m wanting to set up a thermal pig and predator gun. I currently own an 18” 6.5 upper with a fair amount of ammo. I’m wanting as short as possible because I will run suppressed. I’m quite sure max range will be within 200 yards.

Cut my 6.5 barrel down or sell upper and ammo and go with 6.8? Other?

Palmetto has their 12” 6.5 uppers for $390 right now. Quite a few good reports on accuracy. Throw a pistol brace on the lower and you are good to good then sell the longer 6.5 here.

I would find it hard to jump into a 6.8 right now. I don’t see it being readily available in 10 years.

At that distance (apples to apples), the 6.8 (make sure you get the SPC II chamber) will edge out the 6.5 very slightly. Most folks accept that at 300 and beyond, the 6.5 will start to win the ballistics race slightly.

I run a 6.8 SPC II suppressed SBR (ARP barrel, which is now owned by Blackstone Arms, whose owner is a THF member) and have had no issues killing whatever I aimed at. I do roll my own and right now shooting 90gr Gold Dots. However, it has been sub-MOA with everything I've fed it.

If you reload, you can get out of the 6.8 what it was designed to do (again, with an SPC II chamber). Remington botched the original SPC chamber and original ammo offerings caused pressure spikes. The SPC II chamber solved this, but commercially available ammo is still down-loaded to be safe with the SPC chamber. Lackluster, IMHO.

If you don't reload, then suggest staying with the 6.5, but agree with scot that you should just pick up a new upper and be done. I wouldn't fool with cutting one down. Just make sure you're staying within the NFA requirements. With a suppressor, I'm sure you're aware of all of that stuff. Good luck, HTH.

I like 6.8 but if you have a Grendel and ammo, I would just go Grendel. It probably won’t do as good in a short barrel but likely won’t matter if shots aren’t too far.

To me, they are so close there is practically no difference in killing power.

Agree with what they said.

I have 2 Grendels and about to buy a third one for the Wife. By this time next year will probably have 2 uppers 16 and 24 inch, boltaction with a 22 inch and TC Encore 16 inch barrels. I hunt almost exclusively with the Grendel these days and it has never let me down.

Not a hill of beans between the two calibers, What Kmon11 said is the way to go. I had planned to get one or the other, so did a bunch of research. After all that, I made the most scientific and technical decision (I had everything I needed, except brass, to load for the Grendel and had nothing to load for the 6.8).

I’m about to install a Faxon 12 inch 6.5G barrel for the exact reason you stated, a short barreled 200 yard suppressed pig gun.

200 yards and less, it is a flip of a coin, on terminal performance. The Grendel will do better if you want to play at long range. I've spotted for 6.5 Grendel and 6.8 SPC on my range. The 6.8 will run out of gas between 600 and 700 yards. The Grendel will consistently hit out to 800 yards.

6.5 mm bullets have been easier to get than 6.8 for quite some time.

Have your Grendel barrel cut down and move on.

For me the deal breaker is 6.8 components. Good as it is, it is not getting much support in the market. 6.5 Grendel has a much more positive future. But if you are staying within 200 yards I'd get a 16" 300 Ham'r but that's just me.

However... I see lots of guys running long barrels and suppressors on their Grendel's (and other cartridges). No need to put that can on until you are set up and ready to hunt. It's worth a try to see if you like it and it's free. Nothing wrong with a few hundred extra fps velocity.

I don't necessarily believe the Grendel has a more positive future, but folks should choose what they want. I personally have multiple barrel lengths of 300 HAM'R and 6.8 SPC. I chose both of those because I thought they were better for hunting and self defense. I don't have trouble buying components for either.

For under 200 yards, I would lean towards the 300 HAM'R. If I already owned a lot of stuff for 6.5G, I might feel differently. I grew up using .308 or .277 based cartridges for hunting, and it stuck with me. I own a 6.5CM I use for target shooting, but never hunt with it. It doesn't mean you can't, just that I don't.

both work, having said that, I love the 6.8, we have two, my brother has one, several hunting buddies have bought one after hunting with me..

Been a "6.8" guy" for like 15 years. I used to handload but have been using the factory 120 SST load from Hornady since it came out.
Lots of pigs and deer have met their demise to it.

re read your initial post, unless you just really want to make a change.. what you have will work fine. maybe chop the barrel or replace with a shorter/lighter profile one, especially running a can.
Morgan at Class 3 Machining in Dallas does fantastic work and is fast.

^^^ This right here. I've had my LaRue Tactical 6.5G banging steel out to 800 yards at JG's place.

I have only taken the Grendel out to 600 yards but no problem there. Game, hogs at 400+ yards died from 1 well placed shot each. Deer from 20 yards to almost 300 not a problem either.

6.5 bullets have better BC for sure, used to get into an argument with a guy about it. he was only concerned with long distance and said the 6.8 was inferior. he couldn't quite grasp the concept than inside of say 300 yards and certainly for hunting its's an irrelevant point.

That's true enough for sure. The 6.8 will kill just as well as the Grendel---and maybe even better inside typical hunting ranges (and not because of anything inherently better about the cartridge itself but rather just the bullets that happen to be available). Nonetheless, I'd choose the 6.5 simply because finding components will be much easier, and especially bullets. The bullet I liked for the 6.8 was the 120-grain SST, and availability seemed to be spotty for a while. The 6.5, OTOH, seems to be fairly ubiquitous and usually available. The other thing about the 6.8 was that it seemed to really want Accurate 2200 and not much else. Other powders would work, but the 6.8 seemed to have a very well defined preference. The Grendel, OTOH, seemed to like a broader range of propellants (although AR-Comp was really hard to beat!). At least, that's how I saw it during the time I played with the Grendel.

I can’t speak for the 6.5, but the 6.8 with Hornady 120 grain SSTs is a lethal combination.

The .277 120gr SST is available, I'm not sure why you think it isn't. I've made a couple of purchases of them in the last 6 months. Both times I looked, it was no problem to find. Lot's of things are unavailable from time to time.

I haven't looked for it for many months. Got out of the 6.8 and went with .260 for killin pigs. As I recall availabilty was iffy at that time. YMMV.

I loved the Barnes 95g TTSX, was one of the testers for them before they got released to the public.
Loaded hot they were fantastic! Got tired of chasing SSA brass in the field though

For typical hunting distances that most people use an AR for, especially hogs, don't think it makes that much difference, as dad used to say "shot placement trumps everything"

Three currently available hunting bullets that I like for the 6.8 SPC (Order doesn't mean anything):
1) Hornady 120gr SST
2) Barnes 95gr TTSX
3) CBB 105gr MKZ

Personally I would just compare the cost and the availability of each cartridge. Which one is cheapest and easiest to get ??

That is the only question is see between them. Both are proven pig killers.

I've never tried AA2200, but most 6.8 reloaders say it's the choice for 6.8 speed. I've stayed with several of Hodgdon's temp-stable powders as it matches my shooting the best, and all that I tried seemed to work well and were sub-MOA. I think I settled on H322 for the time being.

Can't speak to the 6.8 as I've never shot one. I was talked into the 6.5 Grendel for my son a deer gun. I was hesitant, but when he does his job none of his deer have gone over 40 yards with Nosler 120 BTs. I've been impressed with it.

I tried a number of other powders in the 6.8 and some of them seemed to have potential. They include Benchmark, LT-32, X-Terminator, and AR-Comp. My AA 2200 load got me a little over 2500 fps with th 120-grain SSTs but I left some velocity on the table in favor of accuracy. It looked like LT-32 wanted to work pretty well, but the others presented problems with bullet seating due to heavy compression of the charge when trying to match the velocity of AA 2200. I don't recall how much I had to compress the LT-32 charge and my notes don't mention it, but for whatever reason I chose to go with the crowd favorite. I'd have tried H322 if I'd had any, but I originally used that in .222 Remington and abandoned it in favor of LT-32. I don't have room for powders I'm not using and try to keep them rare.