I picked up an Aero Precision M5 receiver for a good deal. I would like to build a 6.5 CM in a short barrel, not in a long barrel. I have bolt guns with 24" barrels. I'm looking at the Ballistics Advantage barrels in 16 or 18 inch. The reason for the shorter barrel is I will be running the gun suppressed with either an Omega 300 or Scythe-TI. I'm leaning towards the 16" barrel because of total length. I would the gun as lite as possible. Anybody build a 6.5 CM in a 16" barrel? What did you think of it? The gun will be used on pigs out to a couple hundred yards.
- Thread starter tomt53
- Start date
I'd do one of these barrels before I did a BA barrel
www.rainierarms.com
Rainier Arms Match 6.5 Creedmoor Barrel
Rainier Arms Match 6.5 Creedmoor Barrel Introducing our 6.5 Creedmoor barrel. We start off using a high precision match blank in 1:8 twist, machine it to the highest quality and matched with our limited-life time warranty. You have a barrel that is the be
www.rainierarms.com Stay away from mid-length gas in both the 16" and 18" 6.5CM, which is what BA offers.
Would a Criterion barrel be over budget?
I should have added, I have a 16" Ruger SFAR 308 win.
theres another thread with these barrels. seem to be very promising
If you want it as light as possible, I'd grab one of these before they're gone. Nemo arms bought 2A Armament and is phasing out the inventory. Originally these were OEMed by Faxon, but what is left were turned in house by 2A before they sold out. I'd try shooting it as is and if you really want it shorter, chop the barrel later.
The Craddock RTR is great, but it's heavier than the Criterion hybrid barrels, the nitride on the Criterion could also be of some benefit.
I shoot a lot of short barreled (14.5 and 16 inch) 6.5 Creedmoor in a semi-auto platform, and I have been extremely happy with performance.
In the competition space I shoot Quantified Performance (GP and Practical divisions) and NRL Hunter (Team/Heavy Open) with a suppressed 16" 6.5. I did shoot one PRS match with it in like 2018, but it's not really the gun for that (especially as there were not enough gas gunners for a separate division at that match).
My go-to ammo is Berger loaded 140gr Hybrids, or a 135gr A-Tip load. Lots of folks like the lighter weight 6.5 projectiles, but I have not found them to be an advantage for my use. I almost exclusively use KAC 20-round steel magazines.
I hunt vermin and hogs with the same 16" 6.5, and I easily reach out to 700 yards with it, with acceptable terminal performance with appropriately placed hits. Since adding that rifle to my safe, I have reduced my .308 gas guns to just one 16" upper, and I only kept that one in case I need a .308 for some specific requirement.
A 14.5" 6.5 with moderate speed 140gr Bergers will show about the same drops as a 20" .308 shooting 175gr SMKs at M118LR/AB39 velocity, with less wind effect. The 16" cleanly out-performs it.
In the competition space I shoot Quantified Performance (GP and Practical divisions) and NRL Hunter (Team/Heavy Open) with a suppressed 16" 6.5. I did shoot one PRS match with it in like 2018, but it's not really the gun for that (especially as there were not enough gas gunners for a separate division at that match).
My go-to ammo is Berger loaded 140gr Hybrids, or a 135gr A-Tip load. Lots of folks like the lighter weight 6.5 projectiles, but I have not found them to be an advantage for my use. I almost exclusively use KAC 20-round steel magazines.
I hunt vermin and hogs with the same 16" 6.5, and I easily reach out to 700 yards with it, with acceptable terminal performance with appropriately placed hits. Since adding that rifle to my safe, I have reduced my .308 gas guns to just one 16" upper, and I only kept that one in case I need a .308 for some specific requirement.
A 14.5" 6.5 with moderate speed 140gr Bergers will show about the same drops as a 20" .308 shooting 175gr SMKs at M118LR/AB39 velocity, with less wind effect. The 16" cleanly out-performs it.
What are you seeing for velocity out of your 16-in 6.5 Creedmoor gassers?
I was all set on building a 16" 6.5CM on an LMT 15.3" upper. I knew the velocities would be low but with the higher 6.5mm BCs I figured it would even out. Then I started seeing some velocities people were posting and ran the numbers in AB at my DA. I compared them to my 16" 308 I'm loading for right now. 155's at 2750 to 2800. There's 3 or 4 155gr bullets with BCs between .500 and .530. The 16" 6.5 velocities I see are 2500 - 2600. Even with a 140gr BC there's no wind or elevation advantage at 1000. If you try to run 123 or 130gr bullets to jack the speed up, you're at even more disadvantage. Most of those BCs are pretty much right there with 155gr BCs but it's still slower. You have to run a .600 G1 140gr at 2600 to gain 1/2 a tenth of a mil of wind at 1000 over a Sierra 155 Palma. You have to run a .630 G1 140+ at 2600 to gain a .1 mrad wind gain over a 155gr TMK.
Started off with a 16” 6.5CM and worked well for a couple years. Switched to a 20” with +2 CAMGAS and have been much happier. Running suppressed exclusively, the extra length doesn’t hinder mobility like I thought it would. Extra speed is helpful, but the longer gas length has been the biggest benefit.
Between 2475 and 2650 depending on the load. My current lot of Berger was an early lot shortly after they changed to a large rifle primer and it's at the low side of my velocity range, while I recently shot a lot of M1200 that was at the 2630 area average from the same barrel.
I also was going to mention the Craddock RTR...
https://craddockprecision.com/rtr-6-5-creedmoor-16/
https://craddockprecision.com/rtr-6-5-creedmoor-16/
Which bullet are you loading and how is the accuracy from your 16” 308 AR?
To be honest, I think you're kinda comparing apples and oranges. 2795 with 155s out of a 16" barrel is screaming. I run 155 ELDMs at 2825 out of a 20" bolt gun and wouldn't go any higher. I run 140 ELDMs at 2650 in a 19" gas gun and 18" bolt gun. What pushed me to the 18" 6.5 bolt gun was the realization that I needed the same or less wind with the 19" 6.5 gas gun (140s @ 2650) than I needed with a 26" .308 bolt gun (175 RDFs @ 2730). Every way that I've crunched the numbers comparing 6.5 to .308, you need less wind with the 6.5. Of course, you can skew those numbers by running reasonable loads in 6.5 and really stepping on it with the .308...
I was asking because I’ve thought about trying some 155’s but didn’t know if I could get the velocity and keep good accuracy. Those higher bc bullets don’t seem to shoot nearly as well as some of the more mild types like the original Amax and SMK’s from the AR also. I might give some 155 eldm’s a swing in mine.
On the 125’s I have a load with 125 NBT’s that run 2900 from my 16” barrel and hover .8-1.2” at 100 yds. Hammer on deer and hogs.
I have a chrome lined 16” Criterion (before they switched their 6.5 CM to nitrided).
It chronos factory Hornady 143gr ELD-X between 2470 and 2520 depending on the lot.
I'm only shooting them that hot bc they shoot far better at that speed.
Yeah you might be right. It does illustrate that there is a cutoff on speed you should be aware of; a point at which you might as well just be shooting a 308. On the other hand Hodgdon data center lists several loads for 155's at around 2900 with a 24" test barrel. If you subtract 20fps per inch 2795 isn't that far off from Hodgdon book data that is always slower than what people shoot in just about any modern cartridge.
Yeah, there definitely is a speed cutoff. I can't say for sure your load is hot, all barrels, chambers, etc are different. I'm more saying that comparing relatively faster .308 loads to moderate 6.5 loads doesn't really give you an accurate performance comparison. By your math, you're still 60fps faster than what the data center would predict and by my math (I've always used 25fps/inch) you're about 100fps over. Anyways, a lot of this is splitting hairs but I guess that's just part of the process, haha.
If we took your 20” barrel with that load and cut it to 16”, it would be doing 2707fps.
If you loaded longer COL and added some more powder with a fast 16.5” barrel, I think you could do 2795fps, but it’s definitely in the maximum realm or over some.
When I was competing with .308, I shot 155gr Scenars at 2820fps from a 22” Obermeyer pipe built by GAP on DPMS receivers.
If you guys want an excellent internal ballistics engine where you can change charge weights, bullet weights, and barrel lengths from a known set of numbers and see what it will do, use Shooter’s Notes Velocity Estimator. Bookmark that site. You’ll reference it a lot.
I'm using Hodgdon's max load. 45.5gr of Ramshot Tac. It's not 0.1gr more than what they list for load data. I guess to make a fair but theoretical comparison Hodgdon lists 2800 for a 140gr using StaBall. So applying the same 20fps x 8" you'd be looking at 2640fps which just eclipses a 155 at 2800. By about 0.1 mrad at 1000.
I just think with the smaller bore size you see more velocity loss in short barrels.
Tighter bores limit how much peak pressure you can start with because of the case yield strength, bolt and extension, and chamber.
.308s let you evacuate with faster-burning powders and not much overbore, so you can punt them pretty fast with the lighter bullets.
If you look at the SAAMI chamber pressures, it trends downwards from .308 to 7mm and then 6.5s and .243 Win.
.308s let you evacuate with faster-burning powders and not much overbore, so you can punt them pretty fast with the lighter bullets.
If you look at the SAAMI chamber pressures, it trends downwards from .308 to 7mm and then 6.5s and .243 Win.
Similar threads
