Question regarding AR rate of twist and other things


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owlhoot
September 5, 2008, 01:39 AM
I have a fair quantity of older 5.56 ammo with the light 55 gr bullet. Not the newer NATO round. I have a Mini 14 that I bought around 1980 that I've never been happy with and am planning to upgrade to an AR. My question is what is the preferred rate of twist for the old 55 gr load? Is there a compromise twist that will give good results with the old load as well as the NATO load? Are there any chamber differences?

My second question: I have a bolt action sporter chambered in .223. I have been firing this old ammo through the bolt gun. Is this a bad practice? Any potential problems?

My third question: Why would I want a flat top AR rather than the handle? What are the pro's and con's?

Thanks for your help.

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Jim Watson
September 5, 2008, 01:52 AM
Standard rifling twist for the 55 gr M193 was 12".

A 9" twist will stabilize the current M855 round with 62 gr SS109 bullet, and shoot the 55 gr just as well. The 7" twist of the current issue weapons is to handle the very long M856/SS110 tracer bullet.

Lots of information at
http://www.ammo-oracle.com/body.htm

The 5.56 chamber is cut to handle wartime ammunition of sloppy production tolerances being fired in a hot dirty weapon. I have not heard of fresh surplus or commercial imitation surplus giving trouble in a .223 rifle but Ammo Oracle, SAAMI and most Internet Experts warn against it. I don't shoot cheap military crap in my good guns anyhow. I have some ball ammo and a stock AR for when the Islamofascist zombies attack but my bolt action and my target AR get the best handloads I can make.

A flat top AR reciever is meant to mount a scope sight low enough you can maintain a good cheek weld instead of having to stick your neck up to see through a handle mount.

Bartholomew Roberts
September 5, 2008, 09:06 AM
Why would I want a flat top AR rather than the handle? What are the pro's and con's?

Well, you can make a flattop receiver into a carry handle receiver in about 5 seconds with a detachable carry handle mount costing $80. Afterwards, you can switch it back to a flattop in another five seconds. In addition, the flattop receiver can mount a wide range of optics and sights (for example, you can buy H&K sights, M14 National Match sights, etc. for the flattop AR).

The carry handle is for life. It limits what optics you can mount and most optics will be above their optimum height for mounting. If you want to change a carry handle to a flattop, you need to buy a new upper receiver and swap out the carry handle - this process requires special tools and is not quite as convenient as bolting a detachable carry handle onto a flattop.

The pros of a flattop dramatically outweigh any possible cons and to be honest, I can't think of any practical cons when comparing the two - the flattop will do anything the carry handle can just as well and still be more flexible. This is why all the new military rifles are flattops.

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