CIP Length Magazine Compatibility: What You Need to Know About 3-Round Polymer & Steel Mags

UNDERSTANDING CIP LENGTH VS. STANDARD BOTTOM METALS

One of the most frequently asked questions we get at Grayboe involves magazine compatibility—specifically regarding 3-round polymer and steel mags. If you’ve browsed our site and found MDT polymer mags listed for purchase, you might notice that they’re specified for “3.850 bottom metals.” So what does that mean?

Let’s break it down.

Standard bottom metals are 3.715 inches in length, while CIP length bottom metals measure 3.850 inches. This difference is important because it determines which magazines will fit your rifle properly.

MDT POLYMER MAGS (3-ROUND)

These magazines are manufactured by MDT, not Grayboe—we simply resell them for your convenience. They're 3-round polymer mags designed specifically for CIP length bottom metals. You’ll find versions for popular cartridges like:

- 6.5 PRC

- 7 PRC

- .300 Win Mag

If your rifle uses a standard 3.715” bottom metal, these polymer mags will not fit.

ACCURATE MAG STEEL MAGS (3-ROUND)

We also carry 3-round steel mags from Accurate Mag. Like the MDT polymer versions, these are designed only for 3.850” CIP length bottom metals.

So whether you’re considering polymer or steel, the critical point is the bottom metal length. Always check your rifle’s specs before ordering.

CONCLUSION

When ordering mags for your rifle from Grayboe, pay close attention to bottom metal compatibility. Both MDT polymer and Accurate Mag steel mags in the 3-round configuration are designed for CIP length (3.850”) setups only. For best results, double-check your measurements and match them to the mag description on our site.