I am building a flat top, I have the lower and stock together. I am wondering what barrel will give me the most bang for my buck. I am looking toward a heavy barrel 16 inch 1 in 7 twist. Opinions
If you use the 1 in 7" twist barrel, you are then limiting only using heavy .223 projectiles. This tight twist will over stabilize lighter projectiles and your accuracy will suffer. The optimal barrel twist for the entire weight range of all .223 projectiles is 1 in 9". Here is a good primer for twist rates of a .223/5.56 barrel 223 Rem + 223 AI Cartridge Guide
FWIW, my 1:9 won't stabilize (cheap) 62 gr (a possible ammo problem) but does fine with (cheap) 55 gr pills. The 1:8 (Fulton) handles 62 gr well. Both shoot as well as I can see over irons, and I don't have any optics on either one. Yet. The table in RC's linked site says that you can go to 90 grain pills in 1:7, but doesn't say much about minimums. Do note carefully that you can shoot 223 in 5.56 chambers, but not necessarily the reverse. Thus, says me and maybe me only, get the Wylde chamber in your new barrel to avoid all potential pressure problems with factory ammo. (Unless competition is in your future, then more research is required.) Also, FWIW, if I get another AR or barrel, it will be 1:7. My personal opinion, subject to change and criticism, is that 1:7 will prove the most versatile unless I think to go varminting at longish ranges. Around here, there's no such thing as a long shot, there are few places where 200 yards is available except on ranges that are purposely built and cleared. Bear in mind that the feds will take liberties with their tape measures, so give serious thought to an 18 barrel vs. a 16 incher. Both my 16s tape out at 16.25 as I believe all the commercial barrels do, but check.
Just a NOTE here: If you are doing your OWN Loading, Barrel Twist Rates can be compensated for, by Powder Selection, and Loading. You can find the "Sweat Spot" for your weapon, with a little Loading Variation, using just about ANY Projectile. If your buying someone else's Ammo, then you choices are limited to what they Load. ...... YMMV....
+1 for what BT said. I dont have a heavy in 16" but my brother does. He likes Sierra 68gr BTHP and he will keep 5 rounds touching at 100 yards. His is a 1:8 twist. I have a heavy 20" barrel on mine and so far I am happy with it. I only have about 150 rounds through it so far. Will be increasing that number this Saturday and will be able to give a better report.
1:8 has worked well in mine so far, running 55, 62 and 75gr rounds. 20" stainless barrel, standard profile...
My general advice is BCM hammer forged. A mil-spec barrel at a decent price. Not all parts are created equal.
So, I have an update on my AR project. Just back from the range and I am in the 160-170 (out of 200) range for all positions in highpower shooting 200 yards. To me that is saying the rifle is everything I could expect and a little more. Keep in mind, this is the first time going through all positions and with a new, unbroken in, barrel. Not to mention a completely new set up (trigger and scope) for me. I think by mid summer, I am going to be a very happy shooter!! Now, it is time to dash........... BUSY day!!
The drawback to the 1:7 twist is not just it's limitation on ammo but the penetration rate of it also. There were two famous cases of this, I think I read about them in Unintended Consequences. There was a shootout in Florida where some bank robbers were cornered by police, they came out firing and during the melee one of the cops was out of ammo, crouching behind his car when one of the perps came around and shot him with an AR at less than 15'. IIRC. He put his arms up and the round stuck in the bone of his forearm, saving his life. It was later found that the bad guy with the AR had a 1:7 barrell and was shooting 55 gr ammo. The faster twist makes the bullet fragile and it disintegrates on impact with very little penetration. If he had of had the right combination of barrel to ammo he would have easily killed all of the cops that day. A similar story emerged from the Waco massacre. When the F troopers entered a second story room from the roof two of the Davidians started firing up from the ground floor below. They had the same 1:7 barrels with 55 gr ammo and none of the rounds penetrated the floor into the room above. If they had of had the correct combo there would have been several more feds killed or wounded that day. I had a 1:7 barrel and traded it for that reason. I wanted the versatility of ammo if it ever comes down to the wire. I don't want to have to be searching for the correct gr ammo in a survival situation. Now all of my AR's have the same barrel and I can shoot any gr ammo in them. Just my 2 cents, but something to consider.
Minuteman - those are interesting cases, and it seems plausible that the forearm or wood floor protected the lives of the individuals, but, to me, it's more related to the fragmentation properties of the bullet rather than the twist rate. [I am not a Physicist, so this is just my humble opinion.] I'd been taught that the .223/5.56 55gr bullet fragments nearly to powder upen hitting something at 3000+ fps (close range), so hitting sheet rock or an arm at close range could prevent the bullet from travelling further. People like using the .223 for home defense for the same reason - the bullet doesn't usually travel through walls because of fragmentation - lessing the chance of hitting unintended targets. Anyway, it's good to hear from you again here on this forum!
I personally noted a pattern of terminal ballistics in theater where the SS109 5.56 would separate into jacket, steel penetrator and lead base in a person after first passing through at least 1 layer of sheet metal of a car. Of course, none of the wound tracks were straight. For those shot with SS109s without first passing through a barrier, they usually went through like ice picks unless they hit bone. These were from GI issue M4 barrels.
All 5.56 will generally fragment. On impact. That is what its designed to do. The only exception to that is specially made bonded hunting ammunition. The fragmentation is what creates the "just as large" terminal cavity as larger caliber weapons. The way the round fragments changes with velocity and construction. It has little to do with barrel twist. NATO rounds have a distance in which they are more apt to fragment correctly. That should be noted. In general, try both M855 and M193 for accuracy before deciding. This will help: :: Ammo Oracle The advantage to a 1:8 or 1:7 is the ability to stabilize a larger variety of bullet weights. Generally, they will stabilize anything from 45 grains to 80 grains. A 1:9 is hit or miss with anything over 75 grains. I didn't say impossible, I did say hit or miss. My own shooting through several dozen civilian ARs, a few mil-issue M4s, with mil-spec and commercial ammo, and reloads to distance up to 500M confirms this "usually rule". This is a good reason to choose 1:7 or 1:8 over 1:9 for SHTF. Would I toss my 1:9? No. I would try and see what it will stabilize well. Maybe it will shoot 75s, maybe not. Maybe it will shoot 77s, maybe not. Choose your ammo based on accuracy, velocity, and bullet construction. Velocity and construction has more of a bearing on lethality than anything^. Not all 55 grain or 62 grain bullets are mil-spec/created equal.
Rock Creek makes an excellent cut rifling barrel. M193 fragments 20" barrel 190-200m 16" barrel 140-150m 14.5" barrel 95-100m 11.5" barrel 40-45m M855 fragments: 20" barrel 140-150m 16" barrel 90-95m 14.5" barrel 45-50m 11.5" barrel 12-15m Not all 55gr supposed to be M193 fragments only the real M193 fragments. M193's terminal ballistics were so impressive it prompted the Russians to come up with the 5.45. Early M16s had a 1:14 twist was too slow to stabilize the bullet in air. When a bullet does not stabilize it can hit the target at an angle. "Any pointed lead core bullet will turn base over point ("tumble") after penetration in flesh, because the center of gravity is aft of the center of the projectile. The large wounds observed by soldiers in Vietnam were actually caused by projectile fragmentation, which was created by a combination of the projectile's velocity and construction." M16 rifle - Wikipedia, the free encyclopedia
....just adding information RE: fragmentation Direct from .gov documentation: In 1977, NATO members signed an agreement to select a second, smaller caliber cartridge to replace the 7.62 mm NATO cartridge. Of the cartridges tendered, the 5.56×45mm was successful, but not the 55-gr. M193 round used by the U.S. at that time. The wounds produced by the M193 round were so devastating that many consider it to be inhumane. Instead, the Belgian 62-gr. SS109 round was chosen for standardization. The SS109 used a heavier bullet with a steel core and had a lower muzzle velocity for better long-range performance, specifically to meet a requirement that the bullet be able to penetrate through one side of a steel helmet at 600 meters. This requirement made the SS109 (M855) round less capable of fragmentation than the M193 and was considered more humane.
So, I heard the Kommissar-in-chief has used XO to ban M855 ammo because it is "armor piercing." Well, I guess it depends on who is defining "armor piercing," but, all they're going to do is make a black market for those rounds made by the Serbs and Russians. Might be a good idea to pick up a few boxes of M193 as they are probably next. And by boxes, I meant cases.
1:8 has it all. Mine shoots 50-80gr very well. Never tried really light varmint stuff in it. Brands? IDK there are tons of them.
Kind of an older thread, but I have a friend who swears by White Oak barrels for precision setups. White Oak Armament
Then again a 300 AAC is loaded with 110 to 220. Reman ammo can be bought in 147 FMJ @ 2000 fps. I'll keep my 5.56 but I'll also be into the 300 Blackout. Just natural to look for more than one round but the same platform of rifle.
I would tend to agree, but that .300 provides little more than .30-30 ballistics. If you're shooting suppressed, it makes sense, but otherwise is more of a neat playtoy that has horrid ballistics past 200 yards. I'd think the 6.8 SPC is likely better as an all around cartridge for the intents of SHTF. Although that can get pricey as well.
