AR15 tight chamber?

[kyotekiller25]

I'm about to start loading for an AR15 223 Wylde with a 20" krieger 7.7 twist. Taking some case measurements on fired brass and coming up with 1.457" on the Hornady comp gauge. Reason I believe it's on the tight side because my LR bolt R700 223 wylde has a tight chamber and the brass from that rifle comes out at 1.457"

Is this normal for an AR? Not super familiar with them. Also read where ARs need about 3-4 thou bump and 3-4 neck tension, which hopefully won't be an issue with my current die set up which is just an RCBS FL sizer. I also have a Redding FL bushing sizer with a .248" bushing for my bolt rifle with lapua brass at a .250" OD loaded neck. It won't work for the AR/federal brass which is like .247" Loaded neck. So I'd need like a 243"-.244" bushing for it. Seating is done with a Forster ultra micrometer for both rifles.

 

[Edsel]

1. Not necessarily unusual. My $99 AR-Stoner Barrel (MidwayUSA budget bin) + $99 Palmetto State Armory Bolt Carrier Group (also a Saturday Sale item) have a headspace at exactly SAAMI maximum. The sheer volume of these parts being thrust into circulation also results in a sheer volume of inconsistencies and variation - and in my case, one of these barrels paired with one of these BCGs just so happens to have the tightest headspace in all my rifles. For context, my Tikka bolt action rifle has a headspace of SAAMI maximum + 0.001".

Yes, both items were on sale at $99 each, once upon a time - I have three of the first, and a bunch of the latter

2. The recommendation for a -0.003" to -0.004" shoulder bump relative to fired cases for semiautomatic actions was probably a recommendation based on maximizing reliability of feeding, and to account for the uncertainty in headspacing of sized brass (+/- 0.002" - speculation on my part) as well as the wide variation in "bloatedness" from different extraction timing (some shoulders stand tall, while others remain short, some rifles are overgassed and some are not). It's still a good rule of thumb to follow. Brass from semiautos tend to be more varied in headspace after firing, compared to your typical bolt gun. Note that chambering a loaded round in an AR can also "bump the shoulder back" by as much as -0.002" [EDIT: -0.004" to -0.005"]. You may change your opinion about how much headspace you want once you get to measure your rifle's chamber more accurately, and figure out what size it actually tolerates.

3. Account for the "fat bottomed girls." Despite having an identical shoulder bump or headspace, two different pieces of brass may not necessarily chamber in the same rifle - one may have a more bloated base, and the other a narrower one - owing to variations in brass springback, and the chambers in which they were fired.

Brass failing to chamber isn't always a headspace issue.

4. Not sure about the bushings and neck tension, all of my AR brass is full length sized and run through a mandrel that is -0.001" below the bullet's caliber.

Please excuse the use of the pronoun "I" and possessive determiner "my" in these narratives. We handloaders are so in love with our own methodologies and voodoo, and are blinded by self - perceived individualistic exceptionalism that we consider our personal methods as divine gospel

 

[BCP]

I'm about to start loading for an AR15 223 Wylde with a 20" krieger 7.7 twist. Taking some case measurements on fired brass and coming up with 1.457" on the Hornady comp gauge. Reason I believe it's on the tight side because my LR bolt R700 223 wylde has a tight chamber and the brass from that rifle comes out at 1.457"

Is this normal for an AR? Not super familiar with them. Also read where ARs need about 3-4 thou bump and 3-4 neck tension, which hopefully won't be an issue with my current die set up which is just an RCBS FL sizer. I also have a Redding FL bushing sizer with a .248" bushing for my bolt rifle with lapua brass at a .250" OD loaded neck. It won't work for the AR/federal brass which is like .247" Loaded neck. So I'd need like a 243"-.244" bushing for it. Seating is done with a Forster ultra micrometer for both rifles.

That sounds desirable to me. Make some dummy rounds using a sized case and whatever cheap bullets you have lying around, if they stick in the chamber then consider a small base die.