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badzero
February 14, 2017, 07:04
Will a 1:12 twist barrel stabilize a 62 gr projectile (m855) or is it too slow of a twist? I can't seem to google a reliable answer.

CG&L
February 14, 2017, 07:32
I have a 223 with a 1-12 twist. A 52 gr will keyhole at 100 yds. A 45gr pill does well out to 300 yds. The rifle is a Cooper M21

hueyville
February 14, 2017, 08:21
My 1:12 SP1 Colts don't like 62 grain ammo that well. Research tells us the original AR 15/M16 was designed for a 55 grain bullet to be on the ragged edge of stability so that upon impact would yaw, thus inflicting maximum tissue damage as tumbled through the body. Have one original 1:12 barrel that someone cut to 12.5 inches and won't stabilize 62 grain to 25 yards. It wont stabilize a 55 grain past 75 yards either. My 20" 1:12 barrels seem to do OK out to 75 yards with 62 grain then go loopy. Have one 20" SP1 that goes loopy past 100 with 55 grain bullets but 40 to 50 grain bullets it shoots close to MOA. All barrels have a personality and have to test them. Why now prefer 1:9 for milspec 55 to 62 grain ammo. My premium AR's get 1:8 for use with 62 to 69 grain ammo and 1:7 for 69 through 77 grain. Have a 24" bolt rifle with 1:12 that with 37 to 50 grain bullets rains death on prarie dogs, ground hogs, crows and coyotes.

jhend170
February 14, 2017, 08:33
Anything over the 55gr is going to have trouble stabilizing. It's just not a fast enough twist. You need at least a 1:9 for 62gr, typically they are a hair longer by weight because the penetrator isn't as heavy as the lead around them.

Length of a projo is the problem, and a 1:12 just (typically) can't handle a projo that long reliably. Oddly though, this is one of those places where your mileage truly can vary, as a friend of mine tried some 75gr stuff of mine in his 1:9 and it grouped quite well, even though it likely should not have.

So, it's cheap, buy 40 or so and see what results you get.

MAINER
February 14, 2017, 08:42
Remy 700 PSS will keep 60 gr. V-Max in an Inch at 100 yds, but scatters 62 gr. M855 about the landscape and doesn't like 55 gr fmj's much either.
Long Boattail spitzer shaped bullets need a faster twist than shorter flat base hunting type bullets.

Refill for your search foo bucket;

http://www.gunsandammo.com/ammo/pair-barrel-twist-rates-ammo/

https://www.thehighroad.org/index.php?threads/1-12-and-62gr-bullets-for-223.694931/

https://www.ar15.com/forums/t_6_2/409957_.html&page=1

http://info.stagarms.com/blog/bid/371861/How-Barrel-Twist-Rate-Affects-Ammunition-Choice

http://forum.accurateshooter.com/threads/223-1-12-twist.3579071/

TenTea
February 14, 2017, 08:58
Retro AR, 20 inch, 1:14 barrel here.

Does excellent with M193, 55 grain fmj fodder or 60 grain lead gas check bullets.

Shoots a one foot wide arc of keyholes at 50 yards with 62 grain M855. :eek:

I built the rifle specifically for my cast lead bullet handloads and iron sight practice and plinking.

hagar
February 14, 2017, 10:03
May stabilize the 60 Sierra and probably the 64 grain Winchester PP (short stubby bullet), but I think you will be SOL with a 62 grain FMJ.

djfin
February 14, 2017, 11:00
I use a 24 inch 1:12 barreled AR with 50 grain V max bullets. It does not like anything 55 grains or higher at all. 62 grains were all over the paper at 200 yards (24 inch square)

Tuscan Raider
February 14, 2017, 11:42
Green tip in 1x12 in emergencies only and 100yds or less.

That's what we were told in the Army way back when.

hueyville
February 15, 2017, 03:41
Green tip in 1x12 in emergencies only and 100yds or less.

That's what we were told in the Army way back when.

I have some older 1:12 rifles that would be flinging bullets that were going end around end rather than point first and still spinning at 100. The short barrel unsure if bullets would be painful much less lethal at 100.

lysanderxiii
February 15, 2017, 08:07
Whether the bullet stabilizes or not is a result the bullets RPM, which is based on two things: the twist of the rifling and the muzzle velocity.

If you have a 1 in 12 you need to keep 55 grain bullets comfortably above 2500 fps. In cold weather the stability factor drops.

If you want to stabilize a M855 type bullet (.9 inches long) in a 1 in 12, you'll need a muzzle velocity well above 10,000 fps. For more practical muzzle velocities, you'll have to have a 1 in 9 twist.

badzero
February 15, 2017, 08:31
Thanks for the insight guys, I guess I'll be building with my first choice and keeping everything standard at 1:9, having a rifle that is picky about what it shoots is about as useful as my ex wife.

jhend170
February 15, 2017, 10:50
Thanks for the insight guys, I guess I'll be building with my first choice and keeping everything standard at 1:9, having a rifle that is picky about what it shoots is about as useful as my ex wife.

Unless you've already purchased a barrel might as well move slightly higher at a 1:8 and then you can handle just about everything. Mine loves 69gr SMKs in front of Varget from an 18" barrel.

NFADLR
February 15, 2017, 11:02
I'm wondering what the cutting tool looks like that creates the rifleing anyone seen this tool ?

I would bet it's somewhat like a broaching tool in that each does the job of a specific size.

I have a video of a local guys broach machine pulling a spline on the transfer case flange that's going in my 1986 Chevy truck.

WI attempt to upload it somewhere to display in one of my threads.

It's a hoot as most broached holes from my experience are pushed thru the hole and this one is pulled thru.

tdb59
February 15, 2017, 11:36
Green tip in 1x12 in emergencies only and 100yds or less.

That's what we were told in the Army way back when.

Green tip 62s are sideways at 25 yards out of my SP 1 CAR.



.

lysanderxiii
February 15, 2017, 13:10
I'm wondering what the cutting tool looks like that creates the rifleing anyone seen this tool ?

I would bet it's somewhat like a broaching tool in that each does the job of a specific size.

I have a video of a local guys broach machine pulling a spline on the transfer case flange that's going in my 1986 Chevy truck.

WI attempt to upload it somewhere to display in one of my threads.

It's a hoot as most broached holes from my experience are pushed thru the hole and this one is pulled thru.

There are several methods used to create rifling. Staring with the oldest:

Single cut rifling – A single cutter makes multiple passes through the barrel to cut a single groove. The tool in then indexed and the process repeated until all the grooves are cut. It is labor intensive and slow. However, because it is slow, if your careful, you can really control the process and make some extremely accuracy barrels. And, since it requires low amounts of energy, it can be performed by hand, and the equipment is easily made.

A rifling cutter box for single cut rifling:
http://4.bp.blogspot.com/_59GYpEVAu0U/S_TBMFrdlGI/AAAAAAAAAFg/iYVmJnvCTRU/s1600/rifling_head_small.jpg

Broaching – Nothing more than a series of cutters, each slightly larger than the preceding, and the last the final size. In this manner, all grooves can be cut to final depth in a single pass. It does require more effort. The one thing you have to mind is how to keep the swarf from being re-ingested and messing up the work.

Broach:
http://2.bp.blogspot.com/_59GYpEVAu0U/S_TTXb5iNqI/AAAAAAAAAGA/8AgHMkWN1nE/s1600/broach-2.jpg

Button – A very hard carbide “button” with a reverse of the bore profile on it is pulled through the barrel, and quite literally just mashes the rifling into the bore. Very quick and very accurate, and better yet no swarf.

Rifling button:
http://www.quackenbushairguns.com/50button.jpg

In the above three methods, the barrel needs to be drilled to the diameter of the lands prior to rifling. In the following methods, the raw barrel is shorter and has a larger diameter hole than the finished barrel.

Rotary swaging – a series of dies are rotated around the work and are cammed together. This deforms the steel tube to the shape of a mandrel in the center. The dies continue to rotate and come together as the raw barrel is fed into the machine. The mandrel has a raised image of the rifling so the inside profile is squished into the steel. This process is very rapid and repeatable, as all the finished bores will be almost perfect copies of the mandrel. The cold working of the steel also imbues the work with improved metallurgical properties. The machines are relatively inexpensive. This method was invented in the US during WW2.

Rotary swaging mandrel:
http://dmetool.com/wp-content/uploads/2013/11/Hammer-Forging-Mandrels-stacked.jpg

Rotary hammer forging – This is a more involved version of rotary swaging. The principle differences are the dies do not rotate, the work and the mandrel do, the depth of the die movement can be controlled, allowing for exterior profiling, and if desired, the mandrel can have the chamber positive and during the final stages of the operation, the completed chamber can be formed. This process has many of the advantages of rotary swaging, rapidity, repeatability, excellent metallurgical properties, and identical bores, but the machines are much larger and more expensive than rotary swagers (further there is only one company that makes them, GFM, GmbH). This process was invented in Germany at about the same time as rotary swaging, quite independent of each other.

Rotary forging mandrel (with chamber):
http://labscdn2.luckygunner.com/labs/wp-content/uploads/2012/06/hammerforgedmandrel-1024x761.jpg

badzero
February 16, 2017, 08:10
Anyone know where I can find a 20 inch light or gov profile barrel in 1:9 with an fsb installed? I can't seem to find one in stock.

hueyville
February 16, 2017, 08:41
Anyone know where I can find a 20 inch light or gov profile barrel in 1:9 with an fsb installed? I can't seem to find one in stock.

$154 right here. Other places as well. On Gunbroker but add another $100 to price.

http://www.del-ton.com/Del_Ton_Inc_Barrels_p/bl1028.htm

TenTea
February 16, 2017, 09:30
$154 right here. Other places as well. On Gunbroker but add another $100 to price.

http://www.del-ton.com/Del_Ton_Inc_Barrels_p/bl1028.htm

This one is currently actually *In Stock* but it's HBAR.

http://www.del-ton.com/DTI_20_Barrels_p/bl1015.htm

hueyville
February 16, 2017, 09:45
Aero Precision has it in stock with standard profile barrel $249. Didn't try adding to cart on other link.

http://aeroprecisionusa.com/556-20-fsb-rifle-cmv-barrel.html

Edit:
Found a lot of places with the 20" 1:9 for $150 range but out of stock. Quite a few did have it in 1:7 at that price range though. Gunbroker has a vendor selling 1:9 with shielded handguards for $260. Is there a reason for 20"? Lots of 18" versions in twist of choice and a little handier. Found 18" to be as accurate if buy decent barrel. Maybe your building a true to form A1 clone which needs the 20".

badzero
February 16, 2017, 21:25
My 11 yr old son broke his leg at school and he's not able to do much, so he and I are building a rifle. We started doing an 80% lower and he wants a 20 in barrel for it. kind of a bastardized A3 clone. I'm just happy one of my 3 is actually interested and that he was able to bypass the wife's arms embargo. Since you guys talked me out of the slow twist I'm going to keep it the same as the other rifles I have at 1:9. The fsb is because he shoots open sights most of the time.

hueyville
February 17, 2017, 01:48
Give him 40 years, will be looking for glass then. Meantime saving you a lot of money.

michael_g927
February 17, 2017, 03:44
Both of my government pattern rifles use Delton chrome lined barrels.
The A2 uses a 1-9" HBAR. It shoots my 55gr stuff ok.
The A1 uses a 1-12" barrel from AR15SPORT.COM. it shoots my 55gr stuff lights out!
Both rifles zeroed at 300 yards. No keyholing.
My Sig 516 is fair with my 55gr stuff. But remember it has a twist is 1-7".
My 55gr ammo is 55gr Winchester FMJBT over 25gr of Winchester 748.
I like my A1 because it shoots the most common ammo (55gr.) Very well.

gunseller
February 17, 2017, 17:11
All but two of my rifles have a 1/7 twist barrels. They shoot all bullet weights through 80 very well. The short barreled rifle in 1/12 twist in a 10.5" long barrel. At 100 it still does well with 69 and has killed many yotes out to around 300 with the 69s. I know it should not shoot the 69 SMK well and I have no idea which end of the bullet hits the yote at 300 and do not care. The other non 1/7 rifle is a 1/6.5. It shoots 90 real well but also shoots 45s as well as it shoots 69s. It is my service rifle. Enjoy the extra time spent with your son. They grow up way too fast.
Steve

pistolero1911
February 23, 2017, 19:56
My 20" 1:12 twist Colt SP1/A1 loves 55gr M193 ammo. Very accurate up to 300 yards, no key holing. It will shoot M855 but not as accurately as the M193.

Just Sayin' YMMV

ftierson
February 23, 2017, 23:24
My 20" 1:12 twist Colt SP1/A1 loves 55gr M193 ammo. Very accurate up to 300 yards, no key holing.

I would hope no keyholing since that was what it was designed to shoot for the .mil boys...

Forrest

Grinder
February 24, 2017, 18:49
I have a 223 with a 1-12 twist. A 52 gr will keyhole at 100 yds. A 45gr pill does well out to 300 yds. The rifle is a Cooper M21

Something is wrong with this rifle