Need some help.  I have reloaded for bolt actions for years but need some help reloading some ammo for my Bushmaster varmiter.  My questions concern crimping and setting the OAL.  If I seat the bullet .020 from the riflings will I have problems with them feeding through the magazine or the action?  Would it be better to set them at factory length?  Also the recoil on the AR is minimal do I need to crimp?  I always neck size on bolt action rifles and only shoot one round at a time so I have minimal expieriance with crimping.  Im using a 60gr sierra HP some Accr 2520 and winchester brass.  Thanks for the help

Brandon

Pretty much the limiting factor will be your magazine's dimension.  Most find that anything over the max spec of 2.260" cartridge OAL may be problematic in some mags.  Your AR will take rounds considerably longer than will feed in your magazines.  My 5.56mm chamber on my RRA Elite CAR A4 will fully chamber a friend's match ammo that measures a whopping 2.505" OAL.  He loads his single shot through his match AR as they are way too long to fit into a magazine.  I try to keep mine to 2.255" max OAL so I have no worries with feeding from my mags.

YMMV

I reload myself and push my OAL to the max.  The mag-length is 2.275 inches.  I like heavy bullets for my 1:7 twist and dont want to have to hand feed them so it is important to know the limits of the bullet.  Here is my pet load.

Powder: Hodgon Varget 23.5 gr.
Bullet: Hornady 75 gr. BTHP
Case: LC brass
OAL: 2.265

Crimping is not necessary for .223, but I put a very small crimp on mine just as a moisture preventative measure.  I have zero problems with my bullets feeding correctly.

The 75 gr. Hornady AMAX can not be used for semi-auto and must be single-fed.

Hopes this helps,
CJB

I do not crimp anything I load for accuracy, only for general shooting with cheap bullets. I started to crimp after I had a bullet shoved into the case while feeding out of mag, soft points, never have had this issue with polymer tip or hollow point only soft tip, the crimp has fixed the issue with over 1000 fired. I shoot the 75 a-max from a single shot follower from Sinclair International, smooth as can be.

For varmints I load the 55gr Nosler Ballistic Tip with 25 gr of H335

Length: 2.250

That seams to work well in my rifle.  Very accurate to at least 300 yds.  It might not be as accurate as heavier mach bullets but is good enough.  I don't shoot any further so I don't know about longer ranges.  The ball powder is quicker to measure accurately.  Varget tightens the groups but I usually measure every charge with Varget.

Quoted: Need some help.  I have reloaded for bolt actions for years but need some help reloading some ammo for my Bushmaster varmiter.  My questions concern crimping and setting the OAL.  If I seat the bullet .020 from the riflings will I have problems with them feeding through the magazine or the action?  Would it be better to set them at factory length?   You should seat your bullets to an OAL of 2.250" or shorter if you want them to feed from a magazine. Also the recoil on the AR is minimal do I need to crimp?   You do not need to crimp as long as you have adequate neck tension.  Try to push a bullet into its case.  Push it point-first into a hard surface.  If it goes in at all, you have inadequate neck tension.  Polish the expander ball to a smaller size until the neck tension is adequate.. I always neck size on bolt action rifles and only shoot one round at a time so I have minimal expieriance with crimping.  Im using a 60gr sierra HP some Accr 2520 and winchester brass.  Thanks for the help Brandon

...just take a look in the reloading section.  There are plenty of people using magazine-fed rounds that are longer than 2.25 OAL

2.260" SAAMI maximum spec - got it MAXIMUM.  You need a little margin for error, especially in a magazine-fed round.

I also just put a caliper on a 20 round magazine.  It measured 2.260" to 2.280" depending upon where you measured.  

Black Hills also seats the 75 gr Hornady HPBT-M bullet to 2.250".

In reloading, as in life, you need a little margin.