IP Law Daily, PATENT—Fed. Cir.: Distance-related claim terms not indefinite in firearm cartridge housing patent, (Jul 31, 2026)

By Jonathan Anderson

The district court conflated the standards for definiteness and enablement.

Distance-related claim terms in a firearm cartridge housing patent are not indefinite, the U.S. Court of Appeals for the Federal Circuit held, reversing the district court. A three-judge panel of the appellate court concluded that the district court erred by focusing its analysis on a skilled artisan’s ability to determine specific values for each distance to build an operable magazine housing. The appeals court said such considerations are irrelevant to the definiteness inquiry, which is distinct from the enablement and written description requirements (Schmeisser GmbH v. AC-Unity D.O.O., No. 26-1196 (Fed. Cir. Jul. 30, 2026)).

Background. Schmeisser GmbH owns U.S. Patent No. 10,866,045 (the ‘045 patent), which relates to “a housing for cartridge magazine for a firearm.” In 2021, Schmeisser sued AC-Unity and RTG Parts, LLC in the U.S. District Court for the District of Wyoming for infringing claims 1, 11, 13-15, and 17-19 of the ’045 patent. In 2023, RTG Parts was dismissed from the case after settling with Schmeisser. AC-Unity did not settle, and the district court entered a preliminary injunction against AC-Unity.

The court subsequently undertook Markman proceedings for the terms “first distance (A),” “second distance (B),” “third distance (C),” and “offset (V).” The distances corresponding to these terms are shown and labeled in figures of the patent. The court construed these distance-related terms as indefinite. Based on this construction, the court granted partial summary judgment of noninfringement and invalidity in AC-Unity’s favor and dissolved the preliminary injunction. Schmeisser appealed.

Jurisdiction. The appeals court held that the doctrine of pendent appellate jurisdiction applies, and therefore the court has jurisdiction to review the district court’s Markman and summary judgment orders. The parties did not dispute that the appellate court could review the district court order dissolving the preliminary injunction under 28 U.S.C. § 1292(a)(1). However, the parties did dispute whether the appellate court also has pendent appellate jurisdiction to review the court’s otherwise non-appealable Markman and summary judgment orders.

The appeals court reasoned that the district court’s Markman and summary judgment orders are inextricably intertwined with the preliminary injunction dissolution order because the dissolution was expressly based on the court’s prior orders. Thus, the appeals court said, it cannot review the merits of the preliminary injunction dissolution independently of the Markman and summary judgment orders. The appeals court added that it has previously exercised pendent appellate jurisdiction in similar circumstances.

Indefiniteness. The appeals court held that the district court erred by concluding the distance-related claim terms are indefinite. “The terms are clear on their face with each distance being well-defined by the claim language and readily measurable using conventional measurement tools,” the appeals court wrote. “The remainder of the specification explains and depicts what each distance-related term represents.”

The appeals court added that the district court “improperly focused on a skilled artisan’s purported inability to calculate or determine specific values for each distance to build an operable magazine housing.” The appeals court said such considerations are irrelevant to the definiteness inquiry, which is distinct from the enablement and written description requirements. The appeals court found that the claims at issue are definite because “a skilled artisan would be able, with reasonable certainty, to look at a firearm magazine housing, identify the claimed distances, measure them, and determine if the housing falls within the scope of the claim.”

Because the appeals court reversed the indefiniteness-related portions of the district court’s Markman order, the appeals court also reversed the district court’s grant of partial summary judgment in AC-Unity’s favor, which was expressly based on the erroneous Markman order. The appeals court vacated the district court’s order dissolving the preliminary injunction and remanded for further proceedings.

The Case is No. 26-1196.

Judge: Moore, K.

Attorneys: Michael J. Hartley (Lewis Rice LLC) for Schmeisser GmbH. Katrina M. Quicker (Quicker Law, LLC) for AC-Unity d.o.o.

Companies: Schmeisser GmbH; AC-Unity d.o.o.

Cases: Patent FedCirNews