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I have been reading the threads about rifles and have decided it is probably time to move towards an EBR. I suppose this could be a step towards increasing my defense options. I have hunting rifles and am familiar with rifle shooting, using scopes and have fired a pistol with the red/ green dot optics. I have never even held an AR type rifle and frankly need some basic education, starting with a basic explination of the various parts and their functions. I mean basic, like uppers, lowers, (barrel and stock I think I have the idea) and how the are put togther. Then I wonder about the 1:9 versus the 1:7 issue. I assume that refers to the twist rate on the barrel grooves. Does the barrel with more twists in it produce a greater rate of spin on the bullet and result in greater accuracy? And finally, what caliber is most widdely used? I ask this in the context of a worst case scenario and I am forced to scavenge ammunition, I would like to improve the odds of finding some.

Thanks in advance for your thoughts.

5.56mm (~ .223 caliber) is most widely chambered as its what the US Military and NATO uses

I turn in 7 inches (1/7) is "faster twist rate" than 1/9 and better stabilizes heavier bullets (worse with lighter bullets)

Both should do fine with common 55-grain FMJ. 1/7 does better at upper end of 5.56mm bullet weight (69- to 77-grain) 1/9 does better with the little "varmint" rounds ~ 40 grain and well with 62 grain and "acceptable" (depending on variables) up to about 69 grain

They're very easy to work on - don't be intimidated by the sheer volume of info out there. If you can buy a complete rifle, I would recommend that - it's often said that frankenrifles tend to be the least reliable ARs (probably due to tolerance differences between upper/lower batches from different manufacturers?). The most common caliber for these rifles is 5.56x45mm - by far. Judging by your criteria, this is probably the only caliber you ought to be looking at.

A 1:7 barrel is preferable - most surplus ammo out there is going to be M193 (55 grain) or M855 (62 grain), and the 1:7 twist was specifically chosen by Uncle Sam for these loads. The faster 1:7 twist will allow you to stabilize the heavier "modern" loads (usually 68 grain or heavier) that are most suitable for defense and hunting (although they are expensive). A slower 1:9 twist is much more common with civilian rifles, but less desirable unless you intend to primarily shoot light varmit loads (<50 grain).

5.56 and .223 are slightly different - a rifle chambered for 5.56mm can also fire .223, but a rifle marked .223 should not be used with 5.56 (5.56 is a slightly higher pressure round). There is a more detailed explanation here:

http://en.wikipedia.org/wiki/5.56%C3%97 ... _Remington

5.56mm is the standard AR-15 round, although versions in other calibers can be found. 5.56 is used by NATO and many police forces in the US, and is the standard round found in the military M16 and M4 rifles.

As for upper & lower - it is a 2-part receiver design. The lower is legally the firearm, and contains the trigger, buttstock etc. The upper has the barrel attached and bolt.

One of your main decisions is carbine (typically 16" barrel) vs rifle (commonly 20" barrel). For personal protection, shorter and more maneuverable is usually more practical. The longer barrel gives more velocity, so is often better for long range shooting.

The most important parts of the rifle/carbine are the barrel, the bolt, and the trigger. All can be upgraded later (trigger is the most common upgrade people seem to do, barrel is the hardest to do). Stick with a quality manufacturer and you should be okay.

DT... You definitely want to read this web page..
Best resource I've found for answering AR startup questions.

http://forums.officer.com/t81462/" onclick="window.open(this.href);return false;

Man I love this site...but it's costing me a ton of money...now I want an AR!

MikeStone wrote:Man I love this site...but it's costing me a ton of money...now I want an AR!

Be warned, it is virtually impossible to own just one AR - they tend to multiply when put in gun safes.

DentonTactical wrote:5.56 and .223 are slightly different - a rifle chambered for 5.56mm can also fire .223, but a rifle marked .223 should not be used with 5.56 (5.56 is a slightly higher pressure round). There is a more detailed explanation here:

http://en.wikipedia.org/wiki/5.56%C3%97 ... _Remington

This may change your perception about that: http://www.luckygunner.com/labs/5-56-vs-223/" onclick="window.open(this.href);return false;

mdoan300 wrote:

DentonTactical wrote:5.56 and .223 are slightly different - a rifle chambered for 5.56mm can also fire .223, but a rifle marked .223 should not be used with 5.56 (5.56 is a slightly higher pressure round). There is a more detailed explanation here:

http://en.wikipedia.org/wiki/5.56%C3%97 ... _Remington

This may change your perception about that: http://www.luckygunner.com/labs/5-56-vs-223/" onclick="window.open(this.href);return false;

Very interesting read, thank you for posting that. Looks like he did get a few popped primers from firing 5.56 in a .223 chamber (less than ideal). Given that an awful lot of people don't know the difference between 5.56 & .223, you can guarantee that thousands of people are shooting 5.56 ammo in .223 chambers every day without realizing it, and without blowing up their guns...

Thank you for the input. I have much to learn. The references cited are a great start. All thoughts are welcome.

DentonTactical wrote: Be warned, it is virtually impossible to own just one AR - they tend to multiply when put in gun safes.

That's the truth. I built a 5.56 AR a little under 2 years ago from RRA parts. I now have its .458 SOCOM big brother in progress, which should be complete in January.