Sig M17 military magazine question

[AR10ShooterinNC]

What size magazines are the military issued,17 or 21 rounds?

 

[USMC6094]

Both I believe

 

[Jim C.]

Both I believe

Yep. Here's one of my surplus M17s. The 17rd mag and one of the 21rd mags were used, and the other 21rd was new. They're shipped to the military packaged the same way, with two 21rd mags and one 17rd mag.

 

[Derek8404]

I see both on the vests and in the weapons of the gate guards daily.

 

[Unaballer]

Both, Can confirm.