Need some advice on 6.8/Grendel SBR barrel length

[chadwickz71]

Wanting to get another rifle from V7 i have their 308 and its a super nice rifle. Wanting to get the most power out of the small frame and SBR.

Specifically we thermal hunt hogs in Texas, 200yds and in 100% suppressed.. normal is around 75-100yrd shots. So i really don't care about what the rifle will do at 300yd and beyond it'll never shoot past 200 frankly...

V7 sells a complete 6.8 with a 10.25" mid/light contour barrel to skate under the laws of SBRs and sell as a pistol and super light. I was originally thinking i wanted a 12.5" barrel grendel..... but now i am second guessing myself

Whats ya'lls thoughts on a 10.25" 6.8 for what im doing.... Is that starting to lose to much speed at that point... Or is there a reason i should wait and order a 12.5" barrel in a 6.8 or Grendel etc.

 

[oldrifleman]

I am going to throw a dark horse here, the 8.6 Blackout. Check out the rounds that phantom Defense has developed (these guys are hog hunters)

https://phantomdefense.co/shop-ammo/rifle-ammo/8-6-blackout-ammo/

 

[chadwickz71]

Thanks i am aware of it. I would like to keep it to just the grendel and 6.8.

It appears really the 6.8 is more powerful under 200yd by around 200ft/lbs based on just factory Hornady 120sst and 123's in the two calibers if the barrel is the same length.

 

[supercorndogs]

Are you limited to factory ammo? I like the 105g bullets in the grendel. A 223 or 6 arc will kill pigs fine also and give a longer point blank zero range.

 

[VikingSinEater]

6.8 with Fusion 90s. Can load them to 2800 in a 12.5 (should be roughly 2725 out of a 10.5)with AA2200. Throw a suppressor on there and don't look back. If you don't reload then go with the 120sst. Its taken many hogs and deer out to 300 (16” barrel). If you want to punch paper at range then the Grendel is your cartridge. 6ARC might be good too but don't know its performance from a shorter barrel. Factory ammo is like does not fully use the ability of the 6.8 SPC II however. You can load to 100-150 fps safely.

 

[fanninland]

12.5” 6.8 gets you mid length gas… the V7 10” is probably carbine gas? My thermal/pig go-to the last 14 or so years has been ARP’s (now Blackstone Arm’s) 12.5” barrel on suppressed SBR w/120SST factory ammo. Performed great on pigs/yotes for me out to 250-300 yds but I’m mostly at 50-150yds on pigs.

I don’t have time to reload or chrono stuff and not into caliber wars but from what I’ve gathered over the years the 6.8 excels in shorter barrel lengths, 6.5G does to a degree and as distances increase the 6.5G gains an appreciable advantage.

 

[VikingSinEater]

12.5” 6.8 gets you mid length gas… the V7 10” is probably carbine gas? My thermal/pig go-to the last 14 or so years has been ARP’s (now Blackstone Arm’s) 12.5” barrel on suppressed SBR w/120SST factory ammo. Performed great on pigs/yotes for me out to 250-300 yds but I’m mostly at 50-150yds on pigs.

I don’t have time to reload or chrono stuff and not into caliber wars but from what I’ve gathered over the years the 6.8 excels in shorter barrel lengths, 6.5G does to a degree and as distances increase the 6.5G gains an appreciable advantage.

I too have a 12.5" 6.8 from ARP (Blackstone Arms now). I have several barrels from Harrison and they are ALL shooters. I print 3/4 inch off of 90gn Gold Dots (now Fusion unless you can find some demised pulldowns from the ME contracts) at 2800 FPS out of that 12.5" barrel. It does have a lot more velocity out of a short barrel than the 6.5 Gren. Like I said... if I was shooting paper out past 400-500 yards I would go with a full length Gren. But hunting inside 100 yards with a short suppressed barrel? 6.8 all day long. Also if you reload it's a no brainer imo. Been shooting both for around 13 years now, I gave up the Gren when I got into PRS and went into the 6.5 Creed and 6GT range. My 6.8s I'll never give up, great hunting round and self defense round (that 12.5" is my bump in the night gun with a Sandman-L on it).

 

[supercorndogs]

Actually looking at load data a 6.5 grendle and 6.8 spc shot about the same speed with a 90g bullet.

 

[VikingSinEater]

Actually looking at load data a 6.5 grendle and 6.8 spc shot about the same speed with a 90g bullet.

This is the major issue with looking at load data.... If you go to Hodgon you see similar velocities from their loading data for a 24" barrel. The issue is those are the SPC I numbers they have to use. Everything made now is SPC II chambered. This prevents the pressure spikes that plagues Remington's first reamers (Remington messed up the reamer when first pushing the cartridge). The SPC II I use the near max load data to start my loads, which on an SPC II chamber is close to starting at a mid load, then I find an accuracy node and stick with it. When looking at hodgdon you see they use a 24" barrel to get 3k FPS out of a 90 grain bullet for 6.8 SPC I.. I have factory ammo that is 2988 average out of a 16" 3R barrel (XM68GD). You can reach 3k pretty easily with AA2200 in a 16" barrel with those same load numbers (31.4g being the max advertised). That same XM68GD ammo is 2800 out of my 12.5". One of the MAIN advantages of the 6.8 SPC II is was the design for short barrels. You don't really gain much from using a longer barrel in the 6.8 SPC II, I never even take out my 20" anymore.

There are those that hot rod the 6.5 gren with shorter barrels using various powder and bullet combos as well. But the easy button for short barrel hunting is the 6.8 SPC II. I would grab a 12.5" 3R or 5R barrel from Blackstone arms or a built upper (mid-gas) and never look back.

 

[supercorndogs]

A grendel can pushed over pressure as well to get more velocity.

There is no magic short barrel designed cartridge. These things are governened by physics not feels. You cut a barrel you loose velocity, you add barrel you gain it. I

The 6.5 grendel and SPC are likley to become even more niche as the 6 and 22 arc take off.

 

[dk17hmr]

I have an 11.3" 6.8 that kills mule deer really well. 90gr gold dot at 2750fps (I think I can't honestly remember).

I haven't played with the 6.5 Grendel. I'd like to I just haven't because I have 6.8s, 300blks, and 224 Valkyrie (in the works). Grendel ammo seems to be more available and cheaper.

 

[smarcus]

I went with a 12.5 Grendel. Barrel is Proof CF. I'm shooting Cavity Back Bullets factory loads 105 Grain at 2477fps. I set this up as my walk around daytime hunting rifle for hogs, deer, coyote on 200acre ranch in South Carolina and have a separate rig set up for night time Thermal. I did try a Guide 630 LRF thermal clip on last weekend and made hits on steel out to 500 meters. I use a 50 yard zero to get a decent MPBR out to 250yards. I would have no problem using this as my one and only rifle but I have a 6.5 CM with a Trijicon Reap IR that crushes hogs off a fixed platform for when I'm sleeping out all night.

	12.5 Proof Grendel	105 CBB
BC G1	0.48
MV	2477	actual
Weight	105
Temp	80
Wind	0
Zero	42
RANGE (YDS)	VELOCITY (FPS)	ENERGY (FT.-LB)	TRAJECTORY (IN)	COME UP (MILS)
0	2477	1430	-3.00	0.00
50	2390	1331	0.38	0.21
100	2305	1238	2.25	0.63
150	2221	1150	2.48	0.46
200	2139	1067	0.96	0.13
250	2059	989	-2.47	-0.27
300	1981	915	-7.94	-0.73

 

[VikingSinEater]

A grendel can pushed over pressure as well to get more velocity.

There is no magic short barrel designed cartridge. These things are governened by physics not feels. You cut a barrel you loose velocity, you add barrel you gain it. I

The 6.5 grendel and SPC are likley to become even more niche as the 6 and 22 arc take off.

You aren't pushing over pressure for the 6.8 SPC II. It would in in Spec I chambers, which are rare to come by these days. It was designed initially to use a shorter barrel. I never said I pushed this cartridge over pressure… where did you get that from? Of course it's governed by physics, but the difference is one of these cartridges was designed to be used in a short barrel configuration the other was not. SPC will never be niche in hunting circles, thing drops hogs and deer very well with little recoil. 6 and 22 ARC are great out of the appropriate barrel length but I would never make an SBR 6 or 22 ARC.

Either way its whatever flavor you want to use. 100 and 110 grain Accubonds are awesome in the 6.8. The 90GDs are the ticket for short barrels though from my experience.

 

[hlee]

Contrary to what many on this board believe, shooting beyond 200 yards is the niche application. And, when constrained to a short barrel length, more over bore cartridges tend to be penalized more heavily than those that are less over bore. 22ARC is fine, but I’m not going to ham string it with a 12” barrel. A suppressed 12” 6.5 Grendel drops a hammer on deer in this range, while staying light and nimble.

 

[supercorndogs]

Contrary to what many on this board believe, shooting beyond 200 yards is the niche application. And, when constrained to a short barrel length, more over bore cartridges tend to be penalized more heavily than those that are less over bore. 22ARC is fine, but I’m not going to ham string it with a 12” barrel. A suppressed 12” 6.5 Grendel drops a hammer on deer in this range, while staying light and nimble.

While staying easy to poke out the pickup window.

 

[hlee]

While staying easy to poke out the pickup window.

Damned straight!

 

[VikingSinEater]

Now if we could just get the SBR and suppressor bullshit stricken from the damn NFA…

 

[91Eunozs]

Honestly can’t go wrong with either round for your use case…

6.5G seems to have better support for factory loads, so if you don’t reload that’s what I’d recommend. I chose 6.8 SPC-II personally, but I reload and can push the velocities with my preferred bullets a bit higher. I have a 12.5”, a 14.5” and a 16” upper in 6.8, and all three shoot great:

I honestly don’t shoot at long enough distances to notice any real difference in terminal performance or accuracy between them; usually well inside 200 yards…hell, half my shots on pigs are at 75 yards or closer. I usually carry the shorter ones during the day, but typically use the 16” one when using a thermal at night.

 

[chadwickz71]

Do you mind posting some of your speeds and bullets you are getting out of each barrel length for reference?

 

[91Eunozs]

Do you mind posting some of your speeds and bullets you are getting out of each barrel length for reference?

Will have to find my notes, or the pics… not in the folder I expected to find them in, but IIRC I was only ~150fps slower in the 12.5” vs. the 16” barrel, shooting the exact same loads.

I’m getting ~2,700 fps (usually just under that) out of my 16” barrel with the 110gr Hornady VMax and 28.5-29gr Accurate 2200. I can usually get almost 2,800fps using the 95gr Barnes TTSX (blue tips) and just over 29gr of that AA2200. I could probably go a bit higher on the powder charge, but that was fast enough for my needs and the distances I typically shoot, and I started seeing some bulging on my primers above 29.5 grains of that AA2200.

I prefer the Barnes bullets, but can almost always find the Hornady bullets in stock around here.

I’ve also used Accurate 1680 across all my 6.8 loads and it shoots well (accuracy is the same), but I get more drop at 100 yards. I didn’t chronograph it, but surmise it’s going slower.

Edit: Still can’t find the pics of the chrono, or of the load data cards I drop in every box of reloads, but did find a pic of some of the cases fresh out of the wet tumbler! LoL

Lemi-shine, a drop of dish soap, hot water and stainless steel pins FTW! LoL

Getting closer...found one of a load in progress, but with the 110 BTHP Match vs the VMax:

 

[supercorndogs]

I bet the pressure between the two barrels is diffrent. Surely it's not loosing 42fps per inch from 16 to 12.5.

 

[chadwickz71]

I was actually thinking the same thing. I appreciate the load info there. What barrel manufacturers do you have on your guns are they all the same or different.

 

[91Eunozs]

I bet the pressure between the two barrels is diffrent. Surely it's not loosing 42fps per inch from 16 to 12.5.

No idea… may have been more, but can’t find my dang notes, and that’s what I recall.

The 12.5” is a White Oak, and the other two are from ARP but think all three are 1:11 twist. Pretty sure the White Oak is a 6 twist, and the ARPs are both 5R twist, but would have to look at ‘em to be sure and not at the house this weekend.

Edit: Found this pic of that WOA barrel from when I first installed it, can’t quite make it out, but think it’s stamped 1:11

Will see what else I can find, but will take ‘em out when I get home and pull the hand guards. That’ll tell us the twist rate if it’s on there…know the chambering is stamped on there, but not sure about the twist rate.

More to the point, I’m not sure that twist rate even matters for velocity…the type of rifling used would for sure, but not sure twist rate plays a big part at all on velocity. I’m no ballistics expert though, so maybe someone else can chime in with better info?