Standard AR-15 lowers with different caliber uppers (6.5, 6.8, 300 and such)

[clayshooter99]

Good afternoon, looking for knowledge!!! I am very familiar with standard AR in 223/556. Looking for youth deer hunting upper here in Indiana. Public land not an issue, private only so I am not forced with straight wall. I just have extremely limited knowledge in the 6.5 Grendel, 6.8 SPC and 300 blackout. Anyway, I have standard AR lowers so it needs to fit. What calibers match to standard bolts? I see the term 6.8 SPC and 6.8 SPC II, and do not see an ammo difference with that. I am leaning away from 350, 450 and 458 for less recoil and true rifle cartridges advantages. Will standard uppers in the 6.6, 6.8 or 300 be capable of 2 inch groups at 100 yds?. Any other valuable info would be appreciated.

 

[Mgderf]

.300 Blackout uses the same bolt as the 5.56, has low recoil, and should do 200 yards if you do your part.
One caveat.
Since they do use the same bolt and magazine, it's easy to get the upper mixed up with the 5.56.
You do NOT want to accidentally load a 5.56 round in a .300 Blackout gun.
Bad things can happen.

 

[edwea]

6.5, 6.8, and 300 blackout are all capable of 2" groups and have good hunting loads available. Of those 3, 300 blackout is the only one with a common bolt. If you're just throwing another upper on a lower, it would already have it's own bolt, right? Then the only consideration would be the magazine. The 300 uses standard mags, so another point for it. I have 6.5 specific mags, but usually use standard p mags and don't have any failures with it. Are you buying or building?

 

[edwea]

Fwiw, my vote goes to the grendel. I have killed deer with the 300 and grendel, more with the grendel though. At the ranges that I hunt, there is not too much daylight between the two ballistically speaking. I just like it more for hunting .

 

[BIGE7.62]

I'm sure I'm the odd men out but
6.8 spc . It doesn't have the following of the
6.5 Grendel or the 300 blk out though so ammo is harder to get in the box stores . Plenty on line .
The 6.8 spc even out preforms the 6.5 Grendel to 300/400 yards, has a stronger bolt and is more than capable of shooting under 2 "moa with proper ammo and shooter
The 6.8 spc ll is the chamber cut and IIRC they went from a 1/10 twist to a 1/11 .
A bolt ,barrel and mags and your gtg.
Mags can be for 6.8 or 224 Valkyrie

 

[clayshooter99]

Will be buying complete upper or maybe even full rifle. I am leaning towards the 6.5 Grendel or 300 ACC Blkout strictly for ammo availability. And likely leaning more towards 6.5 due to speed and flatter shooting. So I am understanding the 330 is same bolt and mags? The 6.5 requires different bolt and mags. Anybody have solid recommendation's on what company for the upper and mags?

 

[Kirk Freeman]

Will be buying complete upper or maybe even full rifle. I am leaning towards the 6.5 Grendel or 300 ACC Blkout strictly for ammo availability. And likely leaning more towards 6.5 due to speed and flatter shooting. So I am understanding the 330 is same bolt and mags? The 6.5 requires different bolt and mags. Anybody have solid recommendation's on what company for the upper and mags?

I like LWRCI. Bought this one on INGO.

It loves the Federal 110grs. I put an ALG ACT in it, BCM CH. I like having rails for bipod and light even if don't use it.

It has the Manta rails in black now to protect my vealesque hands.

I use black Magpuls with a 3 demarcating them in a giant white paint marker.

PA GLX 2X on top.

 

[AndreusMaximus]

You do NOT want to accidentally load a 5.56 round in a .300 Blackout gun.
Bad things can happen.

Reverse that. A 5.56 round won't fit in a 300 Blackout chamber, but even if you managed to jam it in there, it wouldn't cause a catastrophic failure because the smaller .22 caliber bullet would head down the 300 Blackout barrel just fine, albeit sorely lacking in velocity.

However, a 300 Blackout round will chamber just fine in a 5.56 gun, and WILL blow up your rifle due to the .30 caliber bullet of the 300 Blackout being unable to fit down the .22 caliber bore. There are some pretty gnarly photos out there of the aftermath of accidentally firing 300 Blackout ammunition in a 5.56/223 barrel.

Kaboom!!! 300 BLK in 5.56/223 AR-15!

Some unfortunate shooters have learned the hard way that is is possible to fire a 300BLK in a rifle chambered for 5.56mm or 223 Remington. The results of such a dangerous event are spectacular. In …

rifleshooter.com

 

[AndreusMaximus]

Will be buying complete upper or maybe even full rifle. I am leaning towards the 6.5 Grendel or 300 ACC Blkout strictly for ammo availability. And likely leaning more towards 6.5 due to speed and flatter shooting. So I am understanding the 330 is same bolt and mags? The 6.5 requires different bolt and mags. Anybody have solid recommendation's on what company for the upper and mags?

Yes, 300 Blackout uses the same bolt and magazines as 5.56.

6.5 Grendel uses a different bolt. On the magazines, it's a bit more complicated: some 5.56 magazines will work with 6.5 Grendel, depending on the internal design. However, you can also get magazines that are specifically designed for 6.5 Grendel, which should be more certain to work reliably.

 

[jagee]

I went with 300BO myself. Where I hunt I won't have a shot further than 75yds, and I wanted to run suppressed. Seemed to fit the bill perfectly for me.

HM Defense 300 Blackout Integrally Suppressed Upper

Full thanks to @jagee that ordered this and allowed me to do a review. I've seen a lot over the years - suppressed this, newly invented that. Thirty five years collecting guns, fifteen years in the resale market and there's new stuff, better designs, better materials, but not a lot of change...

www.indianagunowners.com

 

[dak109]

I run a 6.8spc. My son uses a Grendel. Both are accurate and kill deer and coyotes. One of those would be my choice over the Blackout. Unless you are suppressed and want to be really quiet. Bear in mind you lose velocity and range with subsonic in the blackout. I run the 6.8 suppressed with supersonic ammo, not as quite as Blackout with subs but I don’t give up velocity or range.

Edit to add: Ammo isn’t as common as Grendel or Blackout but is available online. If you reload you have options. If not, Druid Hill Armory loads some good hunting ammo.
SPC vs SPC II ,as mentioned is a different chamber. There isn’t ammo loaded to SPC II pressure by major manufacturers. Unless you get into rolling your own or a custom reloader it is a non issue.
I do recommend the SPC II chamber though.

 

[dak109]

Don’t feel like editing again lol.
Magpul Six8 mags will not work in a standard AR lower. They are for LWRC Six8 specific lowers. ASC and Duramag work with standard lowers.

 

[Purdue1991]

I highly recommend the 6.5 Grendel for deer hunting. Has the range - 300 yards plus. Has very low recoil. Every deer I've shot in the boilerplate have dropped in its tracks.

 

[DadSmith]

I've got and used a 6.5 Grendel.
It's very accurate with 123gr Hornady SST, and ELD match. I usually load my own 123gr SST, but I've also bought their Hornady Black 123gr ELD match ammunition to try out. It's good stuff also.
IIRC it was shooting under 1 moa with both.
I never tried the ELD match for hunting. But the 123gr SST does a good job.
I've also been wanting to try Speer 90gr TNT as well. I hear good things about those bullets in a Grendel.
My Grendel build has a 20" barrel.

 

[Creedmoor]

.300 Blackout uses the same bolt as the 5.56, has low recoil, and should do 200 yards if you do your part.
One caveat.
Since they do use the same bolt and magazine, it's easy to get the upper mixed up with the 5.56.
You do NOT want to accidentally load a 5.56 round in a .300 Blackout gun.
Bad things can happen.

I don't believe you can chamber a 5.56 round in a 300 blackout chamber. The bolt will not close all the way.

 

[edwea]

I've got and used a 6.5 Grendel.
It's very accurate with 123gr Hornady SST, and ELD match. I usually load my own 123gr SST, but I've also bought their Hornady Black 123gr ELD match ammunition to try out. It's good stuff also.
IIRC it was shooting under 1 moa with both.
I never tried the ELD match for hunting. But the 123gr SST does a good job.
I've also been wanting to try Speer 90gr TNT as well. I hear good things about those bullets in a Grendel.
My Grendel build has a 20" barrel.

Grendel doesn't seem fussy at all to load for does it? Seems to shoot pretty well with a variety of bullets, or at least mine do. My go to hunting loads have been 120 sierra pro-hunters and 120 speer gold dots. This year I'm using 115 Barnes Tac-Tx. I've used the Tac-Tx in 300 blackout and it worked well. Just moving to lead free rounds for hunting.

 

[clayshooter99]

Thanks for the responses. My only concern with the 300 Blackout is the much slower speed. Kind of feels like going back 100+ years. Also, how is the expansion of the bullets with the 300 blackout and the slower speed?

 

[glank09]

I have taken many deer with the 300 blackout. I have gotten very good expansion. I hunt with the Barnes 110 Vor-tx, if I remember correctly velocity is somewhere around 2400fps.

 

[edwea]

You do you, but how much velocity does it take to kill a deer? Few if any cartridges have dropped as many deer as the venerable 30-30 and it's velocities are right around 2200-2400 at the muzzle. I realize that those are heavier bullets, but they have the bc of a brick. I took a small spike last year with a 300 blackout loaded with 110 Barnes over 19 grains of H110. Shot was 150y and it was a pass thru. Never recovered the bullet. Now I don't know what ranges you hunt at, but for where I was hunting, this was a long shot.

Another factor to consider is damage to meat. If you're hunting to feed yourself, you'll likely find those higher velocities tend to translate to meat loss. Few things bum me out more than peeling the hide back and finding jello instead of a shoulder roast. Just my .

Eta..not trying to push the 300 necessarily, just that I don't think a person needs to chase fps to hunt deer in IN. I'll be using my 6.5 grendel this year because I like the rifle more. It's a build on an INGO lower

 

[AndreusMaximus]

Thanks for the responses. My only concern with the 300 Blackout is the much slower speed. Kind of feels like going back 100+ years. Also, how is the expansion of the bullets with the 300 blackout and the slower speed?

As the two replies above referenced, bullet selection is key. Naturally, if you were, for instance, to use a 150 grain bullet designed for a hunting load in a 308 Winchester cartridge, you'd definitely be setting yourself up for failure. A good deer hunting load in 300 BO will typically use a bullet around 110 grains. Bullets that are designed for varmint rounds in 308 (i.e., rounds that are designed to provided extreme, explosive expansion/fragmentation with relatively little penetration) such as the 110 grain Hornady V-Max, the 110 grain Barnes referenced above, etc, will often work well, because at 300 BO velocities instead of fragmenting you will tend to see more controlled expansion, the way you would want a deer round to work.

I've never personally shot a deer with 300 Blackout, but I have heard plenty of success stories. Of course, it's not going to be as ideal for 300+ yard shots. But if your shots are all going to be at distances of 200 yards or less, it's plenty to get the job done, and, as others have pointed out, the higher velocity of more powerful cartridges often translates into no benefit at closer ranges, and only results in more lost meat.