12.5" to 14.5" barrel 5.56 vs 300 BLK?

[Dov]

If sticking with a 12.5 to 14.5 inch barrel, no suppressor, is there any reason to use anything besides 5.56?

[Default.mp3]

If sticking with a 12.5 to 14.5 inch barrel, no suppressor, is there any reason to use anything besides 5.56?Sure, if you want better ballistics (both external and terminal), you could go with something like 6.5 Grendel or 6.8 SPC. Mission drives the gear train and all that.

[Super77]

If sticking with a 12.5 to 14.5 inch barrel, no suppressor, is there any reason to use anything besides 5.56?

Between 300BLK and 5.56, I don't think BLK makes a ton of sense unless you want something shorter than a 10.5" barrel.

[Navin Johnson]

Question is way too specific. Could you make it more open ended?

[TGS]

If sticking with a 12.5 to 14.5 inch barrel, no suppressor, is there any reason to use anything besides 5.56?

Yes.

[Dov]

Question is way too specific. Could you make it more open ended?

:cool:

[Dov]

So arguments for something other than 5.56 would be?

I really like 6.5's but I'm not someone who would be using a sub 16" 5.56 for anything even really midrange let alone long range so exterior ballistics differences not significant for this IMO

Terminal ballistics for even 12.5" barrel 5.56 are still categorically above service pistol cartridges right? My understanding is 300 BLK is a better choice somewhere around 10" or less barrel for terminal ballistics & etc vs 5.56 or that is my rule of thumb from last time I looked into it. Didn't think there was any other benefit for supersonic loads in longer barrels, other than possibly barrier penetration.

[Tensaw]

Disclaimer: This reply will not be of much, if any, assistance.

I love the *idea* of 300Blk in the same way that I love the idea of .45. I have three 300Blk rifles in 7.5, 10.5, and 16 (all unsuppressed). The 10.5 is my favorite because of how it handles and shoots - the recoil impulse is smooov and justt very pleasing to shoot. The two shorties are for the house and the 16 is a deer gun (all ARs). If I had it to do over again, I would either stick to 5.56 and just run 77 grain loads or step up to a 6.5 Grendel (for hunting). Two main reasons are the increased cost of even basic FMJ ammo and the anxiety of trying to make sure a 300Blk doesn't end up in a 5.56 chamber (the second mainly).

I jumped on the train early thinking/hoping it would take off and go somewhat mainstream - it didn't. It would not hurt my heart if it took off and ammo prices came down to be competitive with 5.56. If we got to the point, I would probably leave the 5.56 guns in the safe and run 300 almost exclusively, but I suspect we will never see that day.

[TGS]

If you want 45-70 ballistics in a semi auto, there's a variety of big bore cartridges available for the AR-15.

Whether you personally want 45-70 performance in an AR-15 is up to you as an individual, but they're not 5.56 and they have a purpose for existing.

[Clusterfrack]

My go-to AR is 11.5” suppressed. If I need to shoot significantly past 300yds, I have a 18” 5.56 and a 16” 6.5G.

But, for a PDW role (handy truck gun, etc), my 7.5” 300BLK unsuppressed is hard to beat for size and capability. Don’t have any interest in 300blk otherwise.

I like 14.5” 5.56 mid length a lot for a do-all AR.

[Dov]

My go-to AR is 11.5” suppressed. If I need to shoot significantly past 300yds, I have a 18” 5.56 and a 16” 6.5G.

But, for a PDW role (handy truck gun, etc), my 7.5” 300BLK unsuppressed is hard to beat for size and capability. Don’t have any interest in 300blk otherwise.

I like 14.5” 5.56 mid length a lot for a do-all AR.

Are you using your 7.5" BLK on coyotes or any other critters? If so curious what load & performance your seeing?

[Dov]

If you want 45-70 ballistics in a semi auto, there's a variety of big bore cartridges available for the AR-15.

Whether you personally want 45-70 performance in an AR-15 is up to you as an individual, but they're not 5.56 and they have a purpose for existing.

I'll give you the 375 to 45 caliber options have uses well beyond 5.56 but that's outside the box I was thinking of in this case. Partly because I've never considered any of those calibers in anything shorter than 16" barrel, but perhaps some of them perform well in sub 16" barrels?

[Clusterfrack]

Are you using your 7.5" BLK on coyotes or any other critters? If so curious what load & performance your seeing?

I use my 18" 5.56 with a thermal for coyote hunting, but I'm confident that a Barnes 110gr Tac-Tx (https://www.midwayusa.com/product/1001895644/?pid=430384) would do the job.

Cdub_NW has shot a lot of 'yotes with 5.56, and I think he shot at least one jackrabbit with his 300BLK 5.5" Rattler.

[Cdub_NW]

I use my 18" 5.56 with a thermal for coyote hunting, but I'm confident that a Barnes 110gr Tac-Tx (https://www.midwayusa.com/product/1001895644/?pid=430384) would do the job.

Cdub_NW has shot a lot of 'yotes with 5.56, and I think he shot at least one jackrabbit with his 300BLK 5.5" Rattler.

Correct on all points. Lots of yotes with 556 out of a 16" barrel w/thermal. Mainly 53gr V-Max running about 3050fps, only had two yotes not drop where they stood, both were due to bad shot placement by the operator (dare I say I pulled the shot... but I pulled the shot). Put down a few more with 75gr A-Max 556 out of a 26" bolt gun, that was pretty impressive. All of my shots have been over 100 yards and the longest we have dropped one so far was at about 435 under thermal.

**Added** Sorry, forgot to discuss the SBR lengths specifically. I have dropped two yotes in the yard (118 and 128 yards) with a 10.5" 77gr Hornady loads, and one so far with the 14.5" with 77gr OTMs. I would have zero concerns using either. The 14.5" would easily handle the task out to 400 with confidence but I would hesitate with my 10.5" only because it's setup with a red dot and gauging drop at distance would be risky in my opinion. Hopefully all those counts go up in the near future as I have seen a lot of new activity on my cameras lately so I am guessing it will be a busy winter on the farm.

As for the 300blk. Yes a half dozen jack rabbits with the 5.5" rattler with fantastic results. All were under 50 yards but its devastating to say the least. Personally for yotes I would prefer the faster/flatter cartridge compared to the weight of the 30cal. Things happen so quickly that not being able to get the exact range is common, having more forgiveness in drop can be the difference.

Unless there is a specific need to be ultra quiet and subsonic, I would opt for the 556 every time over the 300blk. AND if the distances were over 100 yards.

[TGS]

I'll give you the 375 to 45 caliber options have uses well beyond 5.56 but that's outside the box I was thinking of in this case. Partly because I've never considered any of those calibers in anything shorter than 16" barrel, but perhaps some of them perform well in sub 16" barrels?

The .458 SOCOM is specifically purposed for 10"-16" barrels. That's the only one I've had a passing interest in, I'm not sure about the other Thumpers in SBRs.

[GyroF-16]

**Added** Sorry, forgot to discuss the SBR lengths specifically. I have dropped two yotes in the yard (118 and 128 yards) with a 10.5" 77gr Hornady loads, and one so far with the 14.5" with 77gr OTMs. I would have zero concerns using either. The 14.5" would easily handle the task out to 400 with confidence but I would hesitate with my 10.5" only because it's setup with a red dot and gauging drop at distance would be risky in my opinion. Hopefully all those counts go up in the near future as I have seen a lot of new activity on my cameras lately so I am guessing it will be a busy winter on the farm.


Thank you for the data points.

Do you tend to choose heavier (75-77 gr) for the shorter barrels? If so, what drives that decision?
Or was it just what you were using that day?

I ask because I’ve tended to view the heavier (longer) bullets aa optimized for long-range precision. If you’re choosing them for shorter ranges (+/-100 yds) out of a 10.5”, I want to know what advantages I haven’t been aware of.

[Cdub_NW]

Thank you for the data points.

Do you tend to choose heavier (75-77 gr) for the shorter barrels? If so, what drives that decision?
Or was it just what you were using that day?

I ask because I’ve tended to view the heavier (longer) bullets at optimized for long-range precision. If you’re choosing them for shorter ranges (+/-100 yds) out of a 10.5”, I want to know what advantages I haven’t been aware of.

Yes generally I go heavier with the longer barrels and longer intended ranges. That being said, for the short SBRs I normally run the Hornady 75gr SBR specific rounds. I am concerned with over penetration and or the round not expanding at the lower velocity so I (whenever possible) use the loads designed for shorter barrels.

But.. my most recent coyote was a run in encounter and all I had with my was my 14.5” with 55gr fmj range ammo…. Ripped the yote open easily but it did pass through with enough energy to hit one of my 3” aluminum irrigation hard lines through and through 20 yards behind the yote… take that for what it is. I don’t think I hit any major bone as the shot was about 3” too far back. For the 14.5” setup I always run 77gr otm or similar. That rifle has a 1-6x or 1-10x optic on it and can reach out if needed.

I’ve switch my main SBRs to 12” barrels recently but will continue to run the 75gr SBR loads until I find something better.

[Magsz]

Are you using your 7.5" BLK on coyotes or any other critters? If so curious what load & performance your seeing?

I'm currently hunting hog down here in Florida with a 5.5 inch 300 blackout rattler.

I'm running 110 grain AAC vmax loads through the gun. Zero issues.

I'll have some chrono numbers for this load and my barrel next week. :)