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Discussion Starter #1
Would like to do more shooting off back porch, have 6.8 with can. Question for 6.8 gods, buy a 300bo upper just to shoot subs or play with 6.8 subs in current rig? Also anyone play with subs in 5.56?

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Bison makes a subsonic 6.8 barrel. If buying an upper the 277 wolverine is the same super/sub concept as 300 blackout but uses 6.8 bullets. Biggest difference is 300 has factory ammo.

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What are you shooting at? You should be able to shoot a 90gr - 100gr lead-core bullet subsonic in your 6.8 and still have it stabilize with 1:11 twist rate. I doubt it would cycle the action. However, if your shooting an animal, I have not tested any typical 6.8 bullets that will expand or fragment at subsonic speeds.

I have a 300 BO and have hunted hogs with it. The BO has bullet options that expand at those speeds. I handloaded the 195 MKZ. The subsonic lesson learned was - you may be holding a rifle in your hands but its performance is equivalent to a 45-cal pistol, e.g., 200 grain bullet at 1000 fps.
 

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A significant effort for such a minimal market. After hunting with subs for a year and only getting 50% DRT results on hogs, I went back to hunting with 6.8mm SPC to take advantage of 4 times the kinetic energy - much improved trajectory and terminal results.
 
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For a serious hunt or kill I wouldn't be with out my 68 but I have been playing with a quit little suppressed bolt action 300.
200gr hard cast 1020fps.jpg
The three on the left are a 205 grain mixed cast: kind of hard cast, to hard for what I want. At somewhere around 10 Brinell. At 40 yards suppressed,1025fps it went through two water jugs, one half gallon milk carton full of packed sand, trough a 1/2" piece of plywood 3/4 sideways by the hole in the wood and finally smacked a concrete block to stop it,,, the gray on the far right is of almost pure lead from old cable sheath and powder coated. I will take care shooting and testing it the best I can before running it through my suppressor.. oh yea my Grandson was hitting a 150 yard gong holding around 12 to 14 inches above with that hard coat 205,, seemed like it took seconds before hearing it ring :)
I ordered a .309 cal hollowpoint mould also, will see what it does...
 

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The person that markets the 277 wolverine also sells copper bullets designed for sub velocities.

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I agree with Xman. Even if a subsonic bullet expands, it is less likely to drop the animal in its tracks. One of the things that cause DRT is the "stunning" effect that high velocity bullets cause when they hit the animal. Years ago, one of the people studying wound ballistics stated that a bullet with a large enough effective frontal area* traveling rapidly enough** sent a shock wave through the body that would essentially cause blunt-force trauma to the spine. Kinda like being smacked with a two-by-four. This often stunned the animal long enough for it to bleed out. If you have seen the big cavity formed in ballistics gel by high-velocity bullets, it is easy to imagine what a "thump" that would be to the innards of something like a deer.

* the "effective frontal area" can be caused by a large diameter bullet (especially a flatnose), an expanded smaller caliber bullet or a fmj traveling sideways

** The "traveling rapidly enough" speed is somewhat debated. In a video produced by one of the ammo companies (I forget which one), the rep said 2500 fpm. Another said that it varied depending upon the effective frontal area that is pushing tissue aside. Something very large, like an expanded .44 Mag from a levergun could be under 2000 fps, whereas something smaller like a .223 might be closer to 3000 fps. People on this forum know that low to mid 2000's seems to work with a good expanding 6.8mm round.
 

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Has anyone here loaded up a 6.8 SPC with Trail Boss? I wonder if that would give enough velocity for a good subsonic round. Otherwise, what do you use? The main reduced-charge powder that I am familiar with is H4895.
 

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Discussion Starter #10
This would simply be for practice off back porch, I hunt with 6.8 100gr GMX . Just looking for quiet practice shooting round, sounds like I need a 300bo upper for my current rig, maybe use for home defense, and swap out to hunt with 6.8

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FYI, you will not need an adjustable gas block for the 300 BO. It just doesn't but out that much gas, subsonic or supersonic. I you want reliable cycling with subsonic you will need a pistol length gas tube. I have a carbine gas tube on my 16-inch with a 0.125" gas port. Subsonic, it will pick the next round but not lock back. Supersonic, it throws everything at 5 o'clock. Just not a lot of oomph in that cartridge. My word for it is anemic but fun to shoot subsonic.
 
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Has anyone here loaded up a 6.8 SPC with Trail Boss? I wonder if that would give enough velocity for a good subsonic round. Otherwise, what do you use? The main reduced-charge powder that I am familiar with is H4895.
Yes, I've loaded 6.8 w/ Trail Boss for subsonic rounds. My barrel is 1:11 twist, and I was experimenting with 110 Grain bullets, which were definitely too heavy for that twist rate and that velocity. Trail Boss works beautifully, but I experienced bullet tumbling at around 3 feet past the muzzle, plus the obvious manual recycling. It was not a very useful combination, but it was at least educational.

As these guys suggested, I decided to focus on my .45 for subsonic rounds, if I want to go suppressed. Just as powerful and a lot more handy. Maybe get an extension kit for it, while I'm at it.
 

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I have a 300 BO pistol that I load subs for and a couple of 6.8 SPCs. I also previously loaded 300 BO subs for a MCX carbine that I had. I have never tried to load subs for the 6.8 SPC because I tried it for my .308 and found it challenging. My experience loading subs it that it is a little trickier than loading supersonic rounds. The fill ratios and seating depth when loading subs seemed to play a very significant role in keeping my SD/ES reasonable. I found it easier to load subs for the 300BO because the relatively smaller case capacity seem to help me find a combination of bullet selection, seating depth and powder selection/ charge weight that worked consistently in the desired velocity range. This is particularly true for something like CFE BLK that seems to perform best when loaded as a compact charge. My most consistent results have been with 225 Hornady match bullets loaded compact over CFE BLK. Easiest way to find the compact charge weight was to charge a fired case and testing seating depth and then adjust charge weight based on chrono data. For me, it worked out to 12.5 gr and COAL of 2.200 to get a nice consistent 1050 fps. I was also able to work up a subsonic load for 190 gr sub-x bullets as an alternative to buying the factory ammo but it took more trial and error with the great case volume.

There are lots of people who load .308 subsonic so it would seem logical if you work at it enough that achieving a decent subsonic plinking round for the 6.8 SPC would also be possible. I just think it would be easier to do with the 300 BO given it was a cartridge intended to function both subsonic and supersonic by design.
 

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Would like to do more shooting off back porch, have 6.8 with can. Question for 6.8 gods, buy a 300bo upper just to shoot subs or play with 6.8 subs in current rig? Also anyone play with subs in 5.56?

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There are some things to consider before making that choice. First thing to consider is case capacity. The .300 was purpose designed for subsonic use. It pushes heavy bullets just over 1000 fps to stay below the speed of sound level. The 6.8 requires more powder for it to function in a semi auto properly, making it harder to load down to the subsonic level. It can be done, but is harder. Second, heavy bullets in .30 caliber are shorter than similar weight in 6.8. That's important because the longer bullets have more bearing surface, and that is a factor in choosing a workable twist for the rifling. A 1:10 twist in .30 will stabilize a 200 gr. flat based spitzer at 1050 fps. That happens to be the standard twist for .30 caliber. Standard twist for 6.8 is 1:11.5, and that is too slow for subsonic use. So, for 6.8 you have to run a twist of 1:7 to stabilize those heavy bullets. If you want to run subsonic in 6.8, a better option is to get a 1:7 twist barrel chambered for the .277 Wolverine. It is much, much easier to work up a subsonic load with that case since it is based on the 5.56, same as the .300 Blackout. The same barrel will also handle supersonic loads just fine. Both applications are well proven in the Wolverine with plentiful load data. The .277 has also a good reputation for taking deer and hogs out to the 250-300 yd ranges most deer hunters are shooting at.
 

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Discussion Starter #15
Thx, for the help. Sounds like I need a 300bo with 1/10 spin

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I disagree - 1:8 to stabilize the heavy bullets. However, I recommend 1:7 twist so you maximize expansion of any monolithic hunting bullets you might use. IMO, the Barnes 110 TTSX (supersonic) is one of the few rounds that makes the 300 BO a viable hunting rifle.

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In am planning a 6.8 to shoot subs. I’m planning on casting Bullets for it to get the expansion for kill shots on hogs at close range. I’m interested in if you went with 6.8 or went with the 300.


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In am planning a 6.8 to shoot subs. I’m planning on casting Bullets for it to get the expansion for kill shots on hogs at close range. I’m interested in if you went with 6.8 or went with the 300.


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Neither one. A cast bullet is not going to expand much at those velocities unless its nearly pure lead, maybe not even then. But it won't feed worth a damn in an auto loader if its that soft. I'd be using a .277 Wolverine with a 1:7 twist barrel, and loading the heavy monolithic bullets designed by MDWS for subsonic use.
 

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Would like to do more shooting off back porch, have 6.8 with can. Question for 6.8 gods, buy a 300bo upper just to shoot subs or play with 6.8 subs in current rig? Also anyone play with subs in 5.56?

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For subs in 6.8, I'd rub elbows with Ben at Bison Armory for one of his rigs. He's done some of the ground work already.

I (personally) would never support two specific calibers (.300 BO and .277 Wolverine), since their creators chose to use bottom feeder tactics in an attempt to gain recognition and a fan base (both of whom were banned from this forum for it). Behavior like that should not be encouraged. Marketing of product should include honorable standards. But, I'm sort of old fashioned in my thinking.
 

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For subs in 6.8, I'd rub elbows with Ben at Bison Armory for one of his rigs. He's done some of the ground work already.

I (personally) would never support two specific calibers (.300 BO and .277 Wolverine), since their creators chose to use bottom feeder tactics in an attempt to gain recognition and a fan base (both of whom were banned from this forum for it). Behavior like that should not be encouraged. Marketing of product should include honorable standards. But, I'm sort of old fashioned in my thinking.
I gave my reasons from a ballistics standpoint, and I won't change on that. As far as the other comment goes, we'll have to agree to disagree on the .277. I was there for that, and I know all the inside baseball on it, and there's a hell of a lot more to it than just what you've said. I was one of the few who tried to mend fences, but neither side would, so there's plenty of blame to go around on both sides. But I'm not going to get into it beyond that.
 
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