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Discussion Starter #1
ok.. I learned a lil bit the other day on ar's and uppers and the possibility of changing caliber.

so.

someone lay it out in detail for an AR newb.

I apparrently have an M4 , with a milspec lower. it's in 223/556

what all would I need to fire a different caliber? ( type slow I'm learning :) )

Ie.. do the new uppers come with a bolt and charge handle?

I assume there is some sort of magazine well conversion piece, unless a magazine that fits an ar is also part of the mod.. or a cal that could use the ar mag?

someone told me 300 blackout could use an ar mag?

let the education begin.. hose me down guys.
 

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If you buy a different caliber upper, all you need to do is pop the two pins and swap it out. A mag change and you're firing your new caliber. So easy, even a liberal could do it.

My alternate AR caliber is the 6.5 Grendel.
 

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AR15 supports

204 ruger
5.56
6.5 grendel
6.8 spc
.300 AAC
.450 bushmaster
.458 socom
.50 beowulf

.204, 5.56, .300 AAC, and .458 socom run form unaltered 5.56 mags and all use 5.56 bolt face. The rest use slightly modified 5.56 mags and a slightly bigger bolt face close to .30 remington (the 6.8 spc parent case)
 

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Discussion Starter #4
AR15 supports

204 ruger
5.56
6.5 grendel
6.8 spc
.300 AAC
.450 bushmaster
.458 socom
.50 beowulf

.204, 5.56, .300 AAC, and .458 socom run form unaltered 5.56 mags and all use 5.56 bolt face. The rest use slightly modified 5.56 mags and a slightly bigger bolt face close to .30 remington (the 6.8 spc parent case)
ok, neat.

300 aac? is that the 'blackout' I have heard about?

so.. 204, 300aac, 458socum are what I would look for if I only want to change the upper.. IE.. they run the same amg.

did I get that right?
 

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Discussion Starter #5
the bolt face thing won't matter ( to me ) right? cuz that's gonna come with the new upper? right.. usually complete bolt and charge handle? or?
 

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Discussion Starter #6
ahh.. 300 aac is 300 blackout I've heard about.

this seems ideal for a conversion.. what's the cartridge like? how does it compair in power to 223?
 

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Discussion Starter #7
wow.. just read up on the blackout.

less powder than a 556, was designed with the M4 rifle in mind.. and is more powerfull than a 762x39 even though it is a close 762x35


neat..

di i have to do any weird headspacing.. or does the complete upper constitue a true drop in replacement?

might be nice to have a 300aac upper in a seperate bag with some of it's own mags ( keep them segregated for safety! )
 

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If you buy a 300 AAC upper, it is a true drop in replacement.
 

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.300 AAC is a modern 7.62X39 when loaded with similar weight projectiles. Where the AAC accels is with the super heavys. It canb safely run 200+ gr projectiles at subsonic velocities for use with a supressor and they hit about as hard as a .45 colt. Lots of stopping power. for a 30 round AR.

My dream AR is a .458 socom tho. its one of the thumper rounds. Capable of launching 300 gr bullets at nearly 2000 fps, or 600 grainers at just under the speed of sound. Thats one hell of alot of power from an AR, but the trade off is, a 30 round 5.56/.300 aac mag becomes a 10 rounder for the behemoth .458. Think of it as a .45/70 designed to run in the AR15..
 

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Dont sweat the case head thing. it takes like 23 seconds to swap the bolts out, and 15 minutes to swap out barrels. You really neednt get complete uppers if you dont want. just a good vice, an action block and a 30 dollar armorers wrench. AR15 upper reciever is and AR15 upper reciever, same as a lower is a lower. Bolt carrier is a bolt carrier.. Only difference between AR compatible cartridges is the barrels, bolt heads (on some) and the mags they feed from (whether or not they use std. 5.56 mags)
 

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Let's say you wanted to convert to a 5.45X39 or 7.62X39. When you buy the complete upper (assuming you could even find any right now), it usually comes with the bolt carrier group and at least one magazine. That is not always the case, though, a friend bought a 7.62X39 upper a couple of weeks ago and it did not come with a magazine. I personally think the dealer screwed him on it.
 

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great information JLA, Is there any way I can save this info for later use? So I don't have to repeat this question in 4 months??
 

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Highlight and print.. Or add this page to a favorite on your browser toolbar.
 

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or just PM me.. I do this for a living and I answer questions on a daily basis. ;)
 

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Discussion Starter #16
Let's say you wanted to convert to a 5.45X39 or 7.62X39. When you buy the complete upper (assuming you could even find any right now), it usually comes with the bolt carrier group and at least one magazine. That is not always the case, though, a friend bought a 7.62X39 upper a couple of weeks ago and it did not come with a magazine. I personally think the dealer screwed him on it.
I got lucky. I called the dealer i got my m4 from and asked about uppers. he had none but game me a name of another co local. I went there.. they had a 6.8? grendel,( only had 2 17 rnd clips ) a 762x39 with 1 clip, a 5.45, and the 300accblackout I wanted. :)

worked a good deal on the complete and ready to drop in upper.. got a quad rail, and i picked out some sights and other rail doo dads I wanted.

My ar m4 was pretty basic.. no rails on the handguard, though I did add a lower for a fore grip.

so now I can push out 2 pins and swap over to 300accblackout and have the nice full quad rail. got a folding 'fal' style carry handle too.

i'm a happy camper.

on the downside, I had passed a store that had like 10 boxes of 300acc.. on my way back they had 1 :( i found 3 more on my way home, before work.. so i got 80 rnds to play with at the range this weekend.

thanks for the advice guys.

this platform with changeable uppers is neat. like having multiple caliber bbls with no headspace issues!
 

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Are all these mods considered "oddball" parts?
Not at all. the only thing 'oddball' about the AR is the russian 5.45 and 7.62 X39 chamberings.. Too dang hard to find mags..
 

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Discussion Starter #18 (Edited)
Not at all. the only thing 'oddball' about the AR is the russian 5.45 and 7.62 X39 chamberings.. Too dang hard to find mags..
i saw both of those at the show.. the 545 had no mags and no mags at the show.. the 762x39 had 1 single mag. the 6.8?grendel had a coiple 17 rnder mags.

that's why iwas really looking for the 300acc blackout.

ps.. I read that it fires 300 whisper as well?

will that cycle the bolt?

hows it for stopping power?

I know it is meant to shoot thru a supressed weapon..e tc
 

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They are the same round. SAAMI has tested and standardized the AAC Blackout, and the Whiper remains a wildcat. The Whisper is made by necking up and trimming .221 fireball cases, and the AAC is made by cutting 5.56 cases off at the shoulder and sizing them in a .300AAC die, then trimming. The AAC round will be around longer due to SAAMI standardization, but the Whisper was the original concept.
 

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Discussion Starter #20
ahh.. achieving same chamber size 2 different ways.. neat
 
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