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Posted: 8/2/2026 2:07:50 PM EDT
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Bit of a practical and broader philosophy of use question for the hive - currently shooting a 16” MEGA mid gas 308 barrel in a quasi DMR rifle. I’m content with the accuracy of the barrel, it’ll do just over a minute at 100YD assuming I do my part. What I’m seeing is that it starts to become more of a (literal) hit or miss proposition past 600; 750 is absolutely doable but there’s a lack of consistency that’s a bit frustrating. I understand the ballistic limitations of the cartridge and don’t need it to be a 1,000yd laser beam, but I’d like to get those hits at 750 with a bit more confidence the rifle/bullet will hold up. And ideally I’d like to do so without turning this into a 22” barreled musket. Question: have any of you all made relatively incremental barrel length increases and if so, did it deliver any meaningful improvement in performance? In my case I’d probably step up to 18” rifle gas, eyeing a Criterion or V7 barrel. Math says I’d gain maybe 50-75FPS max which feels marginal. But curious to hear what you all think. Again, overall goal is to move a bit further away from the csass concept without turning it into a true “sniper rifle” that’s a nightmare to maneuver with. Attached File |
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what ammo are you shooting , do you handload ? just over an moa at 100 yards i'd probably be looking at a more accurate barrel if i couldn't find a load/bullet the barrel liked look at some ballistics charts for 6.5 CM out of a 16" barrel if your thinking about re barreling the rifle , you might get to keep it compact and get better down range accuracy. seems like the easy button unless you want to stay with god's rifle caliber |
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Originally Posted By 1iviper: what ammo are you shooting , do you handload ? just over an moa at 100 yards i'd probably be looking at a more accurate barrel if i couldn't find a load/bullet the barrel liked look at some ballistics charts for 6.5 CM out of a 16" barrel if your thinking about re barreling the rifle , you might get to keep it compact and get better down range accuracy. seems like the easy button unless you want to stay with god's rifle caliber For volume I shoot American quality ammo 168gr otms, which print 1.24-1.5 all day long with a bipod and minimal effort. Heavy fgmm and center strike tighten it up a bit more at considerably more cost. I’m sure I could get a slightly more accurate barrel and of course I could hand load, but reloading is just not something I have the time for nowadays unfortunately. To everyone posting about 6.5, I hear you. The bullets are slippery as it gets, I know it would hold up better at longer ranges and punch tighter holes on paper. But I’d like to stick with 308 due to its ubiquitous status, huge bullet selection, long barrel/parts life, and ability to defeat barriers. It hits in a way no 6mm can match. If what that means is this rifle is more or less a 600-700 yard gun, I am OK with that. Was just curious if bumping up the barrel length a bit would help in a meaningful way…I suspect it won’t. Maybe I’ll buy a backup 6.5 upper 
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Originally Posted By SSG-69: I have .308 MATENs in 16” and 18”, both with Mega 1/10 barrels. What twist and what grain weight if factory? You might get a little more going to 178gr. 1/10 mega barrel from back in the good old days  It shoots a little bit tighter with 170+ pills, but I’m trying to balance the perfect loading with something I can stack deep. At $2/round or thereabouts, tough deal to stack the heavy Berger or Federal GMM deep. |
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Originally Posted By Bearcat24: Give these a try before rebarreling…. High BC. https://www.hornady.com/bullets/rifle/30-cal-.308-174-gr-eld-vt#!/ Funny enough I have a box of ELDs that I haven’t gotten around to testing. Next time I get out there I’ll see what applied ballistics spits out and give them a go at longer range. I’m not opposed to the idea of having a loading specific for true long range so long as the zero and holds at shorter ranges aren’t dramatically different than the more typical 168gr loading I have in my ammo fort. In a way, I know I’m asking quite a bit here: 750 yards from a “just OK” 16” barrel and $1/round 308 loading may be a bit greedy. I’d love for this mega barrel to work out, it’s gassed beautifully, nice barrel profile, etc. I don’t wake up in the morning yearning to spend $650 on a v seven barrel 
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| 2" of barrel is absolutely going to be marginal. I'd at least go to 20 but even then you might get what 100fps? If you are dead set on a 308 auto I'd go as long as you can and find the load that shoots best. You should keep track of the different sight ins for the different loads anyway so focus on performance rather than something that shoots the same. I have no idea what the hot 308 loads are. Your options are greatly increased if you handload. |
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| Years ago I built an Armalite 16in AR10 with an old fluted Noveske barrel, that I had melonited. Very accurate, especially with 175, 178, 185, and 190's. problem was they all seemed to be around 2500-2550. so now I shoot 190's in it. very accurate, great BC, and might as well shoot the heaviest thing it can from the mag if they are all going the same speed. Worked out pretty good. |
try some 155gr match ammo to see if the bump in velocity helps out  there are lots of factory loaded optionsi know your trying to keep the cost per round down but maybe also try some of the badlands nas3 loaded ammo when you can find it in stock from their website they list 2644fps from a 16" LMT with 175 smk's , and 2760fps with 150gr TTSX from the same gun they also have a 130gr TTSX load but no data on the 16" yet but they do list 3150fps from an 18" LMT and a 175gr TMK load with the same velocity numbers as the 175 SMK |
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Originally Posted By 135Patriots: 1/10 mega barrel from back in the good old days It shoots a little bit tighter with 170+ pills, but I’m trying to balance the perfect loading with something I can stack deep. At $2/round or thereabouts, tough deal to stack the heavy Berger or Federal GMM deep. Originally Posted By 135Patriots: Originally Posted By SSG-69: I have .308 MATENs in 16” and 18”, both with Mega 1/10 barrels. What twist and what grain weight if factory? You might get a little more going to 178gr. 1/10 mega barrel from back in the good old days It shoots a little bit tighter with 170+ pills, but I’m trying to balance the perfect loading with something I can stack deep. At $2/round or thereabouts, tough deal to stack the heavy Berger or Federal GMM deep. I bought them both on the EE many years ago. I’ve yet to shoot the 18”; just got a great deal on upper/lower/barrel. I have had really fantastic results, like .3 MOA, with 178gr Hornady match in a 1/10 bolt gun and hits to 1100 on steel plates at Raton. Edit: the Brits had good results with 155gr for their L129 rifles. Have yet to try. |
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Originally Posted By 1iviper: try some 155gr match ammo to see if the bump in velocity helps out there are lots of factory loaded optionsi know your trying to keep the cost per round down but maybe also try some of the badlands nas3 loaded ammo when you can find it in stock from their website they list 2644fps from a 16" LMT with 175 smk's , and 2760fps with 150gr TTSX from the same gun they also have a 130gr TTSX load but no data on the 16" yet but they do list 3150fps from an 18" LMT and a 175gr TMK load with the same velocity numbers as the 175 SMK I think I have a handful of mid-weight Hornady SST somewhere in the ammo fort, I’ve chrono’d it but never worked up a dope with it. I want to say it was a superperformance load that was *hot*, spent brass looked pretty angry which doesn’t shock me in a 308 gas gun. I’ve looked at the NAS3 stuff quite a bit but it’s rarely in stock. I’m not opposed to having a smaller stash of boutique ammo and having a separate set of data for it. Perfect world, I consolidate around one loading per cartridge…but this is not a perfect world. |
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If you want to keep it to 16" and still have "more powder burn (less flash)" Open the bore. Perhaps look at 8.6 BO, .338 Fed or .358 Win. db Edited: All three of these have greater legs (range) than they are credited with, but lean into their "strength" with the shorter barrel. |
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In typical arfcom fashion I’m going to keep the 308 upper but also pin together something in 6.5 Creed. Now just need to figure out if 16” rifle gas or 18” rifle gas do something meaningful, seems like 6.5 scales better with bbl length. I am holding onto some of my 308 ammo fort but will sell a chunk of it at a huge discount for any local (mid TN) members. Check the EE
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| All things being equal, barrel length alone has little to do with accuracy. Other things like ammo, barrel quality and overall rifle build quality have more of an effect. |
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Originally Posted By TBone556: Get a criterion 20”, don’t get a ghey 6.5 barrel. Attached File Too late  It is Criterion but the difference in ballistics going to 6.5 was too substantial to pass up. |
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It sounds like you have an accuracy problem, not a speed problem. Keep it short and handy. Buy a higher quality barrel if the desire is there. Maybe try different ammo/bullets. Having shot 22, 20, 18, and 16 inch 308s I would never go any longer than 16 again. At elevation (6k ft and up) 1200 was within reach. 750 shouldnt be an issue at any elevation given adequate minimum speed and a good BC rated bullet. I wouldnt do anything that made my rifle heavier. Yours looks to be over 10lbs already, could be wrong but not likely by much. |
| my 2cents try 185gr Berger Juggernauts FGMM, great bullet out to 800yds on my 16"barrel, my experience 100yd groups are good for zero and getting some initial appreciation for the (precision) group size (eg if you get a 2moa group the ammo does not play well with your barrel) the real deal happens at the point where BC begins to count IMO beyond 200yds, measure your group at 500 or 600yd on a low wind day and see the results of what the ammo and barrel can really do. Prior experience with some ammo types with excellent 5 shot groups at 100yd (sub-MOA large frame AR 308 piston rifle) have had poor precision results ie large dispersion at 600+yds. IMO Applying 100yd results to group size extrapolated to 500+yds can be misleading, BC and aerodynamic drag are key at range. That is not to say that 100yd results are invalid, IMO they are just a pointer. YMMV regards, PeterNNH |
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