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Posted: 10/5/2006 5:32:14 PM EDT
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I am looking a future SBR 6.8 SPC build and the two barrel choices I am looking at is a Noveske 10.5" or 12.5" 6.8 SPC barrel. Which one should I choose? I am leaning toward the 10.5 to gain the smallest length I can. But what I'd like to know is how much effectiveness does the extra 2" gain on the 12.5" model? Obviously a 12.5 will outperform a 10.5 in terms of ballistics, velocity, etc, but how much more so? Is it noticeable or negligible? Thanks. |
 I run a 10.5 Noveske 6.8 for a deer pest control permit. It's plenty effective out to 225 yds, I haven't tested it further, but it fragments like crazy at that range with SMK's and Remington FMJ. I'm sure that the 12.5 will be more, but how much range are you looking for in an SBR. I'm no ballistics expert, but the V-max offerings I feel will fragment almost to 300yds, but I can't prove it........yet. Several 100-200yd shots that I've taken with the V-max had no exit wound whatsoever, just a 2 foot wide purple buldge coming off the side of the deer. Total transfer of energy into the target! The 6.8 may not have an edge on exterior ballistics compared to other 6.? rounds, but the terminal ballistics are out of this world, even the FMJ rounds are frag-o-matics. One thing that you may need to consider if you go with the 12.5 is getting a decent variable magnification optic, it would be a shame to waste all that range and accuracy with an aimpoint or EOtech. 
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Excellent picture. Yeah I was just wanting to know how much a 10.5 barrel gave up over a 12.5 barrel. My ideal setup was going to be a Aimpoint M3 with a 3x behind it for anything over 175 yards. Here's the upper I am imagining. Noveske 10.5" or 12.5" barrel LaRue gas block Noveske KX3 LaRue 11.0 or 12.0 depending on barrel choice (I want the maximum amount covered) LMT front BUIS (some rear BUIS) Aimpoint ML3 with 3X behind it (in some mount) That's it for now. I toyed with the idea of a silencer but I have one for my 5.56 and don't think I need one for a 6.8. |
Well, I think Wes Grant said it best: "If you can't kill it with a 12.5" 6.8, call in a JDAM." I'm not set up to test for velocity right now, but people are getting anywhere between 2350-2450FPS out of LW 10.5" 6.8's using Hornady and SSA ammo. John noveske told me that running the same setup as I am with Remington ammo he was consistently getting 2400FPS +/_. If you are curious about 12.5 velocities, contact Victor from the NV forum, he did some chrono work on his 12.5 noveske. As far as the silencer goes, I know that the 10.5" 5.56 rifles are loud without cans, but wait untill you hear the 10.5" 6.8. You may indeed change your mind in very short order. The guys I shoot with run 10.5" 5.56 rifles, but they won't let me shoot with them without my can  . Also, you get that fantastic freebore boost in velocity!
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The 10.5 is probably adequate for what you're doing, but what's the difference in final length you're after? I know that I personally will slap an extra 2" of barrel onto almost every application, but I dunno. I'd say detemine just how short you actually want it (16" is where I'm happiest), because I don't see that big a difference in lethality of the SPC round. |
It's often stated that 12" is the minimum lenght that still gets all the potential out of a 6.8. I believe (might be wrong though, please correct me if i am) that the reason is that under 12", 6.8 loads will not achieve a full, proper, burn. Still, the 6.8's ballistics keep amazing me. Full fragmentation over 200yds out of a 10.5 barrel! 
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Here's a group I just shot at 300 meters/400yds. The shot on the right was a called flyer. Ammo was Hornady V-max, it would have been tighter if I had sand bags or a bipod. The 12.5 will supposedly get almost all the powder burn out of the cartridge, but the 10.5 doesn't seem to suffer much at all from velocity loss.  I will try to get a picture of it later, but I was shooting cement blocks yesterday with Remington FMJ at 300 yards and it punched through the outside wall with a .270 sized hole and the exit on the other side of the first wall was about 4 inches in diameter. It barely touched the other side, the FMJ completely fragmented in the inside of the block, there were tiny peices of it all over the inside. While I understand that it was concrete and that it doesn't simulate flesh at all, fragmentation like that at that range with FMJ is pretty impressive to me. I promise that as soon as I get a chance to shoot some more living targets at that range that I will give a full review. 
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Thanks for all the replies guys. The blast from the shorter barrels is understandable. That's why I plan on putting a KX3 on it to help direct hte blast outwards. A silencer may be an option one day but for now I think the KX3 fits the bill (until God forbid I get this setup and have my ear drums burst!) Can anyone confirm that a LaRue, DD, KAC, etc 12" rail will fit over a 12.5" barrel with room for the shoulder of the KX3? |
The LT, DD, and Troy rails will fit, but the KAC is a different length. If you go with the first three it will look something like this (Victor's pic, not mine):  But just remember, the flats on the KX3 will be inside the rails, so if you do decide on a suppressor later, you will have to change rails. It happened to me, the KX3 just didn't cut it for me and I had to get a new rail. Also, just some food for thought, but the 12.5" with the KX3 will be very close to 16", I think somewhere around 15". You may want to consider a 14.5 with a welded FH, it would save you ears, give you extra velocity, you can weld on a silencer mount for later upgrades, and it would save you a tax stamp all by being about an inch longer. |
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Here is a quickload trace for the 6.8 SPC with a very common 115gr load. It's accurate enough for you to estimate velocity at about any barrel length. Quickload specifically says 10.5" barrels will give 2203fps while 12.5" barrels will give 2311fps with the same load. 
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Cool chart, thanks. Judging from the curve, 6.8 spc won't fragment at all out of a 7.5" barrel. |
That's what has my head spinning, the 6.8 was supposedly designed to allow for lethality out of shorter barrels, but it seems I am always going to end up near 16". 
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