Simple question

[fly boy]

Some silly noobie questions:

I know the AR-15 platform lower can take a range of ammo sizes, but what is the difference in the magazines?

What is different between the .223/5.56 and a 6.8 SPC II? Are there any calibers that can use the same .223 mag besides 5.56?

If the exterior of the Mag is the same for all calibers, what changes on the interior? I am guessing spring and follower for one, but what else?

[ray1970]

The .300 Blackout uses the 5.56 mags at full capacity. The 6.8 uses it's own proprietary mags I think. As do most of the other calibers.

[J]

Exterior of the mag is usually the same. The follower changes usually, the spring on occasion. The 300blk is the only round I can think of that actually uses the 5.56 mag, but others have gotten OK but not great results running other calibers in them unmodified.

[ray1970]

others have gotten OK but not great results running other calibers in them unmodified.

Yep. I have run 7.62x39 in a standard mag. Works OK if you only load five or six rounds after that it just gets ugly. I think the 6.8 is similar. A few rounds in the mag might feed but a full mag just isn't going to happen.

I did think of one more round that uses a standard magazine. The .458 SOCOM.

[fly boy]

I might have to try the couple 6.8's in a .223 mag, but I still was curious to what the difference is... Just for Gee Wizz info.

[SAnd]

Feed lips and mag curvature. Some cartridges require a different curve because the cartridge has more taper, the 7.63x39 and 5.45x39 mags curve more than standard AR mags. The feed lips are sometimes different, the .410 mags are noticeably different for example. If you do an internet image search you can find pictures of the differences.

Have fun.

[SideShow Bob]

.458 SOCOM works in a standard steel or aluminum AR magazine. Pmags need modifications to run this cartridge.