Are M-15A4 Uppers Compatible With AR-15 Lowers?

The short answer is no, they are not. There really is no such thing as an M15A4.

The classic M15 is a squad automatic weapon variant of the M14 rifle. The catch here is that neither the M14 or the M15 has a split receiver, it’s a single piece.

So in other words, it’s not compatible at all with an AR-15.

If you’re looking for compatibility, the closest you may get is the following list of Ar-15 and/or Ar-10 parts:

• Buttstock assemblies
• Triggers and trigger springs
• Bolt catch roll pin (Armalite Style only)
• Hammers and hammer springs
• Pistol grips (a spacer may be needed for certain models)
• Receiver extension (Buffer Tube)
• Disconnector and disconnector spring
• Buffer detent
• Magazine release buttons and springs
• Safety selectors

AR-15 Upper & Lower Receiver FAQ

Can You Mix and Match AR 15 Uppers and Lowers?

Yes, most different brands of AR15 uppers and lowers are compatible. Please note that you may have some trouble assembling your rifle if you have a specialty receiver. If you’re looking for a lower receiver compatible with most uppers, browse our high-quality selection of 80% AR15 lower receivers.

What Uppers Fit an AR15 Lower?

All AR15 uppers, regardless of caliber, will fit all AR15 lowers to military standard specifications. This is what makes the AR-15 so versatile and loved by many. It doesn’t matter if you attach a 50 BMG bolt-action or a smaller 5.7 FN upper the customizations and combinations are endless. If you’re looking for some of the highest quality and American-made receivers, check out our AR-15 anodized billet 80% lower receivers

Do all AR 15 Lowers Fit All Uppers?

The lower receiver of an AR-15 is more than simply just a part of your gun. Our AR-15 raw forged 80% lower receivers are the foundation to the entire  AR build. It is a precisely machined American Made component that every other part revolves around.

Can I Put an AR 10 Upper on an AR15 Lower?

No, unfortunately you cannot put an AR-10 upper on an AR-15 lower. Even though some parts may be interchangeable, the bolt carrier group and receiver foundations are made to different dimensions. You can quickly recognize that the AR-10 magazines are larger and would not fit in an AR-15 lower receiver.