after I finish my .300blackout build, I'm considering a 6.5 or 6.8... this would still be a few years down the road for me.
I do know that if you reload, the 6.5 Grendel should blow away the 6.8 SPC, you get slightly diminished mag capacity, and any DI gun might need tuning to run dependably...
I believe you'll need a dedicated upper and bolt (not sure about buffer), at which point I'd say just run a dedicated gun
Bill Alexander designed it specifically for the AR rifle platform. Many Soldiers, including me, wishes the US Gov't would switch over our battle rifles for this cartridge. The efficiency is amazing and the killing power blows the 5.56 away. I have been Jonesying for a bolt gun for a while now.
I have been thinking about building a 6.8 SPC or 6.5 Grendel next. I had been leaning toward the 6.8 as it seemed it would be slightly cheaper to put together. However, I discovered that you can get Wolf Military Classic 6.5 ammo for around .35/rd, so now I am leaning toward the 6.5 due to ammo cost.
Does anyone know if any steel case 6.8 SPC is in the works? That may change my mind again if so!
Have had my 24" Heavy barrel for a couple years now. Some of the negatives would include more than normal magazine issues. Some magazine companies had more feed issues than others. Uses Grendel specific magazines only. Lots of chambering issues with failures to chamber and failures to extract. Extractors need to be specific to the Grendel bolt and often won't grip rims and will leave a spent round in the chamber. Extractors need polishing to not cut into rims and most often they are not polished from the manufacturer. Extractor springs sometimes need a heavier custom spring. The ejector pin needs to have a rounded tip and polished. The sharp radius of the standard AR ejector pin sometimes keeps the larger heads of Grendel brass from sliding smoothly from the left of a magazine across the ejector pin. 6.5 bullets sometimes hard to find in stock but getting better. Brass is expensive. Powders have been hard to find but getting better. When introduced their were issues with chambers between 264 LBC 6.5 Grendel and others. Bolts were slightly different between manufacturers with some problems with bolt breakage in the past especially with heavy powder charges.
Best thing is being able to shoot 6.5 bullets in an AR platform with good magazine capacity. Lapua brass is very good but expensive and has small flash holes sometimes causing issues with sizing die primer pins. I get less velocity with Lapua than with Hornady brass. I actually prefer Hornady but no question Lapua is quality. All the Lapua brass I've bought has the shoulders pushed back too far and around 10 thousandths too far compared to Hornady factory and my chamber. There are some very good factory Grendel ammo being produced. It's almost a better bargain to buy factory and reload the brass than buying new brass. I think Grendel rifles from some of the manufacturers are highly overpriced
It's a very fun gun to shoot. The most accurate rifle I own. Don't think I'd recommend converting the military to 6.5 Grendel with all the issues with the caliber so far. Check out the "troubleshooting" section at the 6.5 Grendel Forum. Mine is much more reliable after some polishing and extractor work. Very good long range target and hunting round. Most shoot 20"-24" for long range but 18" owners get good results. Don't expect blazing veloctity. For 120-123 grain loads expect 2500-2650 fps. Doesn't handle heavy 6.5 bullets and 129 grains is about maximum. Requires an expensive long range scope with lots of adjustment for best results at longer ranges and best with a 20 moa sloped scope base. You won't be disappointed with the caliber. Seems 6.5 calibers are inherently accurate and the Grendel is too. Just my UNprofessional opinions.
While I have heard plenty of horror stories about the grendel I have experienced none. Having said that the rifle I built is fairly new. I have maybe 300 flawless rounds down range and I love it.
I did a Grendel build on an AR platform. Used an upper assembly 20 inch stainless fluted barrel from Red X Arms. Very accurate. First time out put 3 of 4 shots within the same hole at 100 yards using Hornady factory loads.
If I wanted a bigger, better AR cartridge, and you want to stay with the Grendel head size, I'd only use the 6.5mm version if I had to be able to buy factory ammo.
Since I do handload, I'd chamber the rifle in 6mm AR, which is of course made directly from Grendel brass. I believe they'll do over 2,800 with a .400+ G1 BC bullet, even from the magazine in a standard length barrel, and they will do so with a bullet weight twice that of a lot of .223 ammunition.
As wildcats go, 6mm AR is about as easy as it gets.
I'm using the Alexander Arms (the inventors of this cartridge) 24" upper and have never had any feed, extraction, or cycling issues using the Hornady 120 and 123 gr. ammo using AA's Grendel mags. With the Giessele National Match match its one my most accurate rifles and was planning to use it for deer if the new regs had been adapted. Very very fun to shoot, too!
I am just wrapping up my "budget" Grendel upper build now. I took a chance and went with an unknown (at least to me) company for the Barrel (Spinta Precision). I found their 20" Grendel barrel on Slick Guns for around $165 shipped. My only concern (besides it being an unknown company) is that it uses the type 1 bolt (7.62x39) and these can be prone to issues. Time will tell if I'll regret this build or not. Best case, I have a tack driver that I built for comparatively next to nothing. Worst case scenario is that it is absolutely terrible, but I won't be out much if it is.
I have 24" that I built from DSA parts and love it. Never had any feed or ejection problems and have been able to use standard ar mags. It really likes the 107gr match kings for long range targets and the 123gr SST for hog hunting.