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Posted: 3/11/2010 7:32:48 AM EDT
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So I got a Hornady OAL Gauge (http://www.6mmbr.com/catalog/item/1433308/977259.htm). I chucked up a few various bullets in my 5.56 barrel to find out where the ogive engaged the rifling lands. I shat brick when I was getting COL readings of 2.35"-2.45" depending on the bullet brand/weight! So with the max COL of 2.260" that means the tightest fit I can achieve is .090"- .100".
The instructions for the tool said to seat the bullets .020-.040" off the lands. Personally I think .040" seems too huge for a .223/5.56 bullet. A reloading buddy of mine said .010" was the best. Of course none of these specs are reachable unless I make loads that are too long to fit in the magazine. 
Also how much of a difference is there in freebore between a barrel chambered in .223 and 5.56? I heard the 5.56 has a longer freebore to accommodate for higher case pressure (which since the max COL is 2.260" that would explain why 5.56 barrels are less accurate than .223 chambered barrels). Thoughts? |
| In an AR the limiting factor is the magazine unless you load single. There are also limiting factors in lever, pump and other autoloaders. Even the box magazine in a bolt gun can limit OAL. Just because the lands are a specific length doesn't mean you can achieve it. |
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In an AR the limiting factor is the magazine unless you load single. There are also limiting factors in lever, pump and other autoloaders. Even the box magazine in a bolt gun can limit OAL. Just because the lands are a specific length doesn't mean you can achieve it. Right. Did you see my post where I said, "Of course none of these specs are reachable unless I make loads that are too long to fit in the magazine." |
| You probably have a .223, that sounds about right, still a little short though. The 5.56 leade is .0303 longer and also is .0025 larger in diameter. The freebore diameter is also different, so the shape of the bullet can have an effect, as in if the ogive is closer to the tip. The caliber should be stamped somewhere on the barrel. |
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In an AR the limiting factor is the magazine unless you load single. There are also limiting factors in lever, pump and other autoloaders. Even the box magazine in a bolt gun can limit OAL. Just because the lands are a specific length doesn't mean you can achieve it. Right. Did you see my post where I said, "Of course none of these specs are reachable unless I make loads that are too long to fit in the magazine." Irregardless that is where it is at. I highly doubt you will achieve it for either chamber in an AR unless you have a special chamber cut. In a bolt gun probably. |
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I went the same route with a hornandy OAL gauge, and came to the same conclusion. I can seat bullets out far enough to not fit into a magazine, and still be off the lands. I worked up some, got a single shot follower so I could use the longer rounds, and checked accuracy. I was using a Noveske barrelled upper. The accuracy improvement at 100 to 300 yds wasn't substantially better than rounds with a coal that would fit in a magazine. I didn't see enough improvement to justify using the single shot follower and loading singly. |
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Quoted: The instructions for the tool said to seat the bullets .020-.040" off the lands. Personally I think .040" seems too huge for a .223/5.56 bullet. A reloading buddy of mine said .010" was the best. Of course none of these specs are reachable unless I make loads that are too long to fit in the magazine. ...Look at it this way... If you've got a factory barrel and buy a box of ammo, you're chances of having jump less than 0.040" is virtually nil. As far as accuracy goes, a lot the times, a bullet simply won't care where you seat it, and the ones that are pickiest generally were never intended to fit in a magazine. If it's a bullet that's meant to fit in a magazine, then simply seat it out as far as you can without having feed problems and enjoy––especially if we're talking about fodder bullets. |
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Every rack grade AR I know have is throated so long that the lands cannot be touched, even with 80 grain bullets. The bullets fall out of the case before touching in my Colt! Lot's of other rifles on the market are chambered the same way because the manufacturers are afraid of a reloader sticking a bullet into the rifling with a hot charge of gunpowder, so they need to protect us from ourselves.
Load to magazine length and don't sweat this. |
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The only bullets on the market designed for AR15's "to touch" or "almost touch" the rifling are for single loading only. The various VLD's from Berger and those formerly made by Jimmy Knox, as well as every 80 grain made by Sierra, Nosler and Hornady fall into this category. The are competition bullets specifically designed for the 600 yard stage of the National Match course. They are needed to compete against .30 caliber rifles at that range and really serve no other purpose. Part of the deal in seating them so long allows for more powder space than a magazine bullet will allow.
I don't agree that the reason for our chamber designs were to protect us from hurting ourselves. They are mostly the result of a search for reliability under adverse conditions and even during full-auto firing. The Wylde chamber retains most of the NATO 5.56mm body dimensions while tightening the throat and leade a little for improved accuracy. The standard .223 chamber is too tight and too short to the lands for the bullets we shoot nowadays. 77 grain bullets do not shoot as well through SAAMI .223 chambers or you'd see them everywhere in tournaments. Most people are running Wylde, CLE or 5.56mm Match chambers. CLE's chamber splits the difference between NATO and Wylde and has been a favorite of the Army's Marksmanship Team. On average it's 2.475" to the lands in a Wylde chamber, 2.500" in a CLE and 2.550" in a NATO or NATO Match using Sierra profile 80's. I am happy with the accuracy I get from a magazine in spite of the fact I shouldn't be getting it. The rifles shoot great when loaded to 2.250" using any quality bullet weighing 52 to 77 grains. FMJ's - don't bother. I'm loading up a few 60 Hornady HP's right now and can load them a little over 2.300" and shoot them through my Model 70 or I can load them at 2.250" and stick them in my AR's mag. They shoot really well in both rifles. I leave the long loads for the bolt gun unless I actually have a full course tournament to attend. |
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I went the same route with a hornandy OAL gauge, and came to the same conclusion. I can seat bullets out far enough to not fit into a magazine, and still be off the lands. I worked up some, got a single shot follower so I could use the longer rounds, and checked accuracy. I was using a Noveske barrelled upper. The accuracy improvement at 100 to 300 yds wasn't substantially better than rounds with a coal that would fit in a magazine. I didn't see enough improvement to justify using the single shot follower and loading singly. You won't notice much difference in accuracy till you start shooting 400+ yards, then you will, especially at 600 to 1000. |
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... I don't agree that the reason for our chamber designs were to protect us from hurting ourselves. They are mostly the result of a search for reliability under adverse conditions and even during full-auto firing. ... The point about long throats and safety was in reference to rifles other than AR's. Whether the manufacturer's take the decision to seat to the lands out of our hands is irrelevent if they throat their chambers out long anyway. We have two choices - rebarrel or find a manufacturer that uses nominal chambers in the rifles they sell. |
| I discovered the same thing when I measured the distance to the lands on a couple of my rifles with Wylde chambers. Fortunately, most bullets tend to be pretty jump tolerant; I can still shoot sub-moa with my White Oak upper, even though 75gr BTHP's have quite a jump to the lands. Pretty much falls into the category of "things you can't control so don't worry about it", IMO. |
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Also how much of a difference is there in freebore between a barrel chambered in .223 and 5.56? click here |
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