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mrbates 03-10-2011 02:49 PM

Introduction and Ammo question.
Hello everyone, I have been lurking for some time, but created an account a few days ago. I am very familiar with the black rifle(12 years Infantry), I just finished(if that is possible) my second AR build.

My current setup is:

RRA upper/bcg/ 16" Hbar, 1/9 twist
Spikes lower/spikes guts.

I didn't realize the 1/9 twist until I received the barrel, I ordered it a long time ago and it was waiting on me when I came home from Afghanistan. What kind of ammo do you recommend for target/everyday use with that barrel? I currently have several boxes of Winchester 5.56 white box 55grain FMJ, but thinking about it that ammo was really designed for the 1/7 barrel correct? Am I crazy? Should i be using a heavier bullet?

Thanks in advance,


treehugger49 03-10-2011 04:20 PM

Though I don't consider myself an expert on the AR platform, and as an owner of a RRA Entry Tactical for the last year, it's safe to say the vast majority of civilian AR-15s are 1:9 twist, and perform well with ammo weighing into the 60s grain weight. I know some varminters looking for smaller MOAs are shooting 1:8 barrels, and 1:7 barrels are definitely preferred for the heavier bullets, but you should find a large array of choices of bullets and bullet weights your gun is capable of firing well.

JonM 03-10-2011 04:26 PM

the 1/9 is a comprimise twist rate that works for pretty much all .223 and 5.56 bullet weights. it fires the 60 grn the best but will fire the heavier bullets and the lighter grain reasonably well. its a good choice for a general purpose AR15

Sniper03 03-10-2011 04:35 PM


The 55 grain bullet is technicaly designed to be shot in barrels that have a 1:12 Twist. Example the Military M-16 A-1 Rifles as well as most of the commercial guns using the 223 Remington Round. Most are 55 Grain or Lighter
Your 1:9 which is a my prefered twist for a tactical rifle, because it kind of bridges the gap. It will shoot the 55 grain well and up to 69 grain. The military 1:7 was designed to shoot the heavier bullets in the 62 grain to 70+ grain bullet range. The reason was, the military wanted more penatration in barrier type material so they wanted a heavier grain bullet which required the 1:7. The twist rate had to be faster so it would stabilize the heavier bullets in flight. Although the 1:7 would shoot a 55 grain bullets OK they would not get the pricise accuracy as they would be using a heavier bullet. Bottom line the 1:9 is an excellent choice for you. Nothing to worry about.


mrbates 03-10-2011 05:24 PM

Thanks all, any recommendations on bulk ammo? I picked up my last four white boxes of 5.56 at Walmart for 9.99, but they don't stock a lot of it. I did see they other day they had a 100 rnd box of Federal 55gr FMJ .223 for 38.99, I only saw one box--maybe they will get more.

treehugger49 03-10-2011 05:41 PM

I have shot exclusively the 5.56 55 grain FMJ ammo thus far, and have avoided the steel-cased offerings like Tula and Wolf. Anytime I can find it in the price range of $.30 - .35 per round, I'll buy some.

I have had good luck finding Winchester Q3131A1 at MidwayUSA (it's not available very often) and Federal XM-193 through Sportsman's Guide. To get the better prices I usually am buying 400 rounds or more at the time.

robocop10mm 03-10-2011 06:55 PM

The 1/7 was developed not for the 62 gr M-855/SS-109 Green tip bullet but for the much longer projectile of the M-856 (Tracer) bullet. The longer the bullet (regardless of weight) the faster the twist needs to be to properly stabilize it.

The 1/7 works just fine with the lighter stuff (55 gr FMJ). My Colt is quite accurate with this bullet. The problem arises when you try to spin a thin jacketed bullet too fast. A 40-52 gr Match or Varmint bullet may come apart because of the rotational forces at play in the fast twist barrel.

In my experience it is not the twist rate that causes the stability, but the RPM's. A heavy (long) bullet can become more stable when the velocity is increased. The increased velocity increases the RPM's and can yield better stability.

stag1 03-12-2011 01:35 PM

Robocop is correct, the 1/7 twist was designed to stabilize the M-856 tracer round. There has been numerous debates on twist rates throughout the years. Each has their place. slower twist rates for varmint shooting, faster twist for longer heavier bullets. A 1/9 twist barrel can handle the most common rounds AR-15 shooters use now days, being the 55 gr and 62 gr rounds.

A good source of bulk ammo is Lake City M193 (55gr), Lake City M855 (62 gr), also IMI, Privi Partzan makes decent surplus ammo and prices have fallen lately to ruffly $6.00 or so a boix.

mjkeat 03-12-2011 02:02 PM

Your 1:9 twist will be fine for the 55gr stuff. I think Horniday makes a 70+-gr round for the 1:9 if you need something heavier.

If you're not happy w/ the 1:9 you can always sell it.

Edit: If you're looking to buy bulk try some Wolf or Tula. Id purchase a couple hundred from Walmart and test it in your rifle first. Occasionally a rifle will leave the factory w/ an out of spec chamber or gas port making int not function steel case correctly.

What size buffer does your rifle have?

JonM 03-12-2011 02:10 PM

be sure that your range allows the wolf tula stuff more and more ranges are banning it due to the harder than lead core material.

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