I have a Kimber M84 in .223. It shoots better than I can most of the time, (nickel sized 5 shot groups at 250 yards) so I've never wanted to take a chance with 556 ammo in it.

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Originally posted by beltfed21:
I have a Kimber M84 in .223. It shoots better than I can most of the time, (nickel sized 5 shot groups at 250 yards) so I've never wanted to take a chance with 556 ammo in it.

Your Kimber 84M has a match grade chamber according to the Kimber website. You are very wise not to stuff crappy 5.56 NATO ammo in there.

However, further reading reveals it has a 24 inch 1:9 twist bull contour barrel. I'm not sure why there is a match grade chamber and such a fast twist in .223 and what one would presume to be a tight .223 chamber with a short leade. My guess is the leade may not be as short as the one in a pure .223 chamber with a 1:12 twist. It may well have a longer leade that will allow the use of longer bullets but it is probably cut very tight to minimize the movement of the case neck, something akin to a Wylde or ArmaLite chamber.

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Originally posted by sigfreund:
I finally found a dealer who tracked down a new/old stock, but I could only guess that everyone expects us all to shoot long, heavy bullets in ARs, but not in bolt guns.

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Originally posted by NikonUser:
I'm not sure why there is a match grade chamber and such a fast twist in .223

When I decided on 223 bolt action, it didn't take long to determine that factory rifles weren't on my short list. I honestly don't recall the twist rates of factory rifles at the time.

Aftermarket 223 barrels are definitely built with users of long, heavy bullets in mind. Sure, there are 1/12 twist barrels available, but also many from 1/7 to 1/8. I won a Proof Research barrel in competition, and I only had the options of 1/8 or 1/7 twist -- nothing else. I chose 1/8 for a 24" barrel.

Checking the Bugholes site for quality 223 barrels, Bartlein barrels are only available in 1/7 and 1/7.7. Mullerworks in 1/7.5, 1/8, and 1/12. Brux in 1/8 and 1/12. Krieger in 1/7 and 1/8. Proof Research in 1/7.

I have run the numbers on my AR-15s, and even for something like prairie dog shoots, the heavier match bullets cheat the wind better than the lighter ballistic tip bullets. Sure, the lighter 223 bullets fly flatter, but laser range finders simplify dialing/holding the correct elevation.

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Originally posted by fritz:
(snip)
I have run the numbers on my AR-15s, and even for something like prairie dog shoots, the heavier match bullets cheat the wind better than the lighter ballistic tip bullets. Sure, the lighter 223 bullets fly flatter, but laser range finders simplify dialing/holding the correct elevation.

It's always been considered axiomatic that we have a little dial on top of the riflescope to compensate very accurately for distance.

The same cannot be said of a dial to deal with the wind, so we try to minimize the effect of the wind on the trajectory of the bullet.

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Originally posted by NikonUser:
It's always been considered axiomatic that we have a little dial on top of the riflescope to compensate very accurately for distance.

The same cannot be said of a dial to deal with the wind, so we try to minimize the effect of the wind on the trajectory of the bullet.

Exactly.

After purchasing my first AR-15, it didn't take me long to realize that lighter varmint bullets fly faster & flatter than heavier match bullets, but get pushed around more by the wind. We can easily measure distance and we have the tables to accurately predict the drop that occurs over distances. But then there's that whole wind thing.

I do not truly understand why some varmint shooters -- especially prairie dogs in windy plains regions -- stick with with speedy 50-55 grain varmint loads when even a pokey 69 SMK load is noticeably less affected by the wind.

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such a fast twist in .223

Odd use of words...I would never call 1:9 a fast twist. Yup my go to stuff is all 1:7 or so. But that's fine to decent bullets like the 69 SMK.
As to the original thread I'd never bother running 5.56 ball ammo because as I think fritz said it sucks. But good 5.56 match loads would not bother me in a bolt action .223. The action on any modern one won't give a hoot. Its not any advantage so why bother. but you aren't going to hurt anything.

The Mini-14 user manual states that its chambered for either the standardized U.S. military, or factory loaded sporting .223 cartridges. See here...

http://www.manualsdir.com/manu...mini-14.html?page=10

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Originally posted by hrcjon:

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such a fast twist in .223

Odd use of words...I would never call 1:9 a fast twist. Yup my go to stuff is all 1:7 or so. But that's fine to decent bullets like the 69 SMK.
(snip)

If you read the rest of the stuff that I wrote after that little snippet, you can see where I explained why I made the statement.

As a matter of fact, the 1:7 twist which the .mil inflicted on the M16/M4 is way too fast for the original bullet used in the rifle, the SS109/M855 62gr FMJ-BT with 10gr mild steel penetrator. It over stabilized the bullet and drastically reduced its effectiveness in combat. The reason for the 1:7 twist was to stabilize the very long M856 tracer ammo in arctic conditions. A 1:10 twist would have been just fine for the original SS109/M855 bullet.

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Originally posted by hrcjon:

quote:

such a fast twist in .223

Odd use of words...I would never call 1:9 a fast twist. Yup my go to stuff is all 1:7 or so.

I agree that 1:9 is slow in the AR world, but to me the 223 is a varmint gun. I prefer 1:10 or even 1:12 for 50 to 55 grain bullets.

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Originally posted by jaybirdaccountant:
I agree that 1:9 is slow in the AR world, but to me the 223 is a varmint gun. I prefer 1:10 or even 1:12 for 50 to 55 grain bullets.

Have you shot light bullets out of faster twists? I have, and all 7 of the AR-15 barrels I've owned shot light bullets well -- one was a 1/9 twist, but all the others are 1/8 to 1/7 twists.

For the upper with the most types of ammo down the pipe. A 24" DSC 1/8 twist, groups of 5 at 100 yards, all factory ammo:
Hornady 55 Vmax -- .92", 1.25"
Black Hills 52 Match HP -- .97", 1.28"
ADI 55 Sierra Blitzking -- .79", .92", 1.05", 1.20"
Black Hills 55 VMax -- 1.01", 1.52"
HSM Berger Varmint 50 -- .63", .75"
HSM 50 Vmax -- .77"
HSM 55 Vmax -- .75", .94"

My shortest barrel and least accurate barrel, a 14.5" LWRC 1/7 twist:
Black Hills 52 -- .67", 1.12"
Hornady 55 VMax -- 1.00", 1.27"
ADI 55 Blitzking -- .88", 1.15"

My newest barrel, 16" Wilson Combat 1/8 twist:
Hornady 55 VMax -- .63", .69", .75", .89", .90", 1.10"
ADI 55 Blitzking -- .44", .66", .87", 1.25"

This level of accuracy isn't just for short range. These loads maintain sub-MOA vertical variation out to as much as 500 yards.

Furthermore, none of the light-bullet loads I've shot show any sign of bullet disintegration from excessive rotational speed.