Schmeisser Gmbh v. Ac-Unity D.o.o.

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
SCHMEISSER GMBH,
Plaintiff-Appellant
v.
AC-UNITY D.O.O.,
Defendant-Appellee
______________________
2026-1196
______________________
Appeal from the United States District Court for the
District of Wyoming in No. 2:21-cv-00024-SWS, Judge
Scott W. Skavdahl.
______________________
Decided: July 30, 2026
______________________
MICHAEL J. HARTLEY , Lewis Rice LLC, St. Louis, MO,
argued for plaintiff-appellant. Also represented by ROBERT
M. EVANS , J R.; J ON A. BRAGALONE , Carson LLP, Fort
Wayne, IN.
K ATHRYN ALLISON VANCE, Quicker Law, LLC, Atlanta,
GA, argued for defendant-appellee. Also represented by
K ATRINA M. Q UICKER .
______________________
Case: 26-1196 Document: 39 Page: 1 Filed: 07/30/2026

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SCHMEISSER GMBH v. AC- UNITY D. O. O. 2
Before M OORE, Chief Judge, STOLL and STARK, Circuit
Judges.
MOORE, Chief Judge.
Schmeisser GmbH (Schmeisser) appeals orders of the
U.S. District Court for the District of Wyoming (1) constru-
ing certain distance-related claim terms in U.S. Patent
No. 10,866,045 as indefinite, (2) granting partial summary
judgment of invalidity and noninfringement in favor of AC-
Unity d.o.o. (AC-Unity), and (3) dissolving a preliminary
injunction previously entered by the court against AC-
Unity. We reverse-in-part, vacate-in-part, and remand for
further proceedings consistent with this opinion.
BACKGROUND
Schmeisser owns the ’045 patent, which relates to “a
housing for a cartridge magazine for a firearm.” ’045 pa-
tent at 1:18–20. In 2021, Schmeisser sued AC-Unity and
RTG Parts, LLC (RTG Parts) for infringing claims 1, 11,
13–15, and 17–19 of the ’045 patent. J.A. 2145–51. Claims
1 and 11–14 are illustrative:
1. A housing for a cartridge magazine for a firearm,
which extends along an X-axis, a Y-axis and a Z-
axis, comprising:
a front wall;
a rear wall;
a first side wall; and
a second side wall, inside surfaces of the
front wall, the rear wall, the first side wall
and the second side wall forming an inte-
rior space consisting of a first region and a
second region, between the first region and
the second region a transitional region is
formed which connects the first region and
the second region with one another;
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SCHMEISSER GMBH v. AC- UNITY D. O. O. 3
wherein the interior space is limited by the
inside surfaces of the front wall, the rear
wall, the first side wall and the second side
wall;
wherein the inside surface of the front wall
extends in the direction of the Z-axis in at
least one of the regions along a first circu-
lar path;
wherein the inside surface of the rear wall
extends in at least one of the regions in the
direction of the Z-axis along a second circu-
lar path;
wherein the inside surfaces of the front
wall and the rear wall in at least one of the
regions are located at a first distance (A)
from one another;
wherein the housing has a housing bottom
side and a housing top side, magazine lips
are formed on the housing topside, and the
housing bottom side is designed to be at
least partially open, the first region being
configured for accommodating four stacks
of cartridges arranged directly adjoining
one other and being offset in the Z-direction
relative to one another, the second region
being configured for accommodating two
stacks of cartridges arranged directly ad-
joining one another and being offset in the
Z-direction relative to one another,
wherein the inside surface of the front wall
has a first protrusion which protrudes in
direction of the X-axis into the interior
space of the housing and extends along the
Z-axis originating from the transitional re-
gion at least partially into the first region
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SCHMEISSER GMBH v. AC- UNITY D. O. O. 4
and also at least partially into the second
region, and the inside surface of the rear
wall has a second protrusion which pro-
trudes in direction of the X-axis into the in-
terior space of the housing and which along
the Z-axis features a start in the first re-
gion and an end in the transitional region
or in the second region.
11. The housing of claim 1, wherein the inside sur-
face of the first side wall in the transitional region
is along a first curved path and the inside surface
of the second side wall in the transitional region is
along a second curved path, wherein the curved
paths each have a respective turning point and ex-
tend from the bottom side of housing to the top side
of the housing before the respective turning point
in direction of a central plane, the curved paths, af-
ter their respective turning point, respectively fit
against a first and a second parallel relative to the
central plane.
12. The housing of claim 11, wherein the curved
paths are symmetrically identical.
13. The housing of claim 12, wherein the first and
second curved paths are arranged in a Z-direction
offset relative to one another by an offset (V).
14. The housing of claim 13, wherein the inside
surfaces of the first side wall and the second side
wall in the first region are located at a second dis-
tance (B) and in the second region at a third dis-
tance (C) from one another, the offset (V) is
between 7% and 35% of the difference between the
second distance (B) and the third distance (C).
’045 patent at 12:66–13:45, 14:25–45 (emphases added).
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SCHMEISSER GMBH v. AC- UNITY D. O. O. 5
The distance-related terms at issue in this appeal are
the “first distance (A),” “second distance (B),” “third dis-
tance (C),” and “offset (V).” The distances corresponding to
these terms are shown and labeled, for example, in Fig-
ures 1, 5, and 6 of the ’045 patent. ’045 patent at Figs. 1,
5, 6.
In 2023, RTG Parts was dismissed from the case after
reaching a settlement with Schmeisser. J.A. 2351. AC-
Unity, however, did not settle, and the district court en-
tered a preliminary injunction against AC-Unity.
J.A. 633–34. After Markman proceedings, the court con-
strued the distance-related terms as indefinite and denied
Schmeisser’s request for reconsideration. J.A. 9–36;
J.A. 37–51. Based on this construction, the court granted
partial summary judgment of noninfringement and inva-
lidity in AC-Unity’s favor1 and dissolved the preliminary
injunction. J.A. 52–55; J.A. 4–5. Schmeisser appeals.
D ISCUSSION
I. Jurisdiction
We have jurisdiction to review the district court’s order
dissolving the preliminary injunction under 28 U.S.C.
§ 1292(a)(1). The parties dispute, however, whether we
also have pendent appellate jurisdiction to review the
court’s otherwise non-appealable Markman and summary
judgment orders. Appellant’s Br. 2; Appellee’s Br. 1–4. We
agree with Schmeisser that the doctrine of pendent appel-
late jurisdiction applies in this instance.
“In rare circumstances, the doctrine of pendent appel-
late jurisdiction allows federal courts of appeals limited
1 The court granted only partial summary judgment
because it did not dispose of AC-Unity’s counterclaim that
the ’045 is unenforceable “due to deceit and non-disclosures
in the patent application.” J.A. 54.
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SCHMEISSER GMBH v. AC- UNITY D. O. O. 6
discretion to review a ruling that is not independently ap-
pealable if jurisdiction exists over another related ruling.”
Orenshteyn v. Citrix Sys., Inc., 691 F.3d 1356, 1358
(Fed. Cir. 2012). We may exercise “pendent jurisdiction
when the appealable and non[-]appealable decisions are
‘inextricably intertwined’ or when review of the non-ap-
pealable decision is necessary to review the appealable
one.” Id.
Here, the district court’s Markman and summary judg-
ment orders are inextricably intertwined with the prelimi-
nary injunction dissolution order because the dissolution
was expressly based on the court’s prior orders. J.A. 4–5
(explaining the preliminary injunction was “no longer war-
ranted” based on the Markman and summary judgment
proceedings). Thus, we cannot review the merits of the pre-
liminary injunction dissolution independently of the court’s
Markman and summary judgment orders. We have previ-
ously exercised pendent appellate jurisdiction in similar
circumstances. See Helifix Ltd. v. Blok-Lok, Ltd., 208 F.3d
1339, 1345 (Fed. Cir. 2000) (exercising pendent appellate
jurisdiction over an interlocutory grant of summary judg-
ment when “the district court based its denial of the pre-
liminary injunction request on its summary judgment
ruling”). We thus conclude that this court has jurisdiction
to review the district court’s Markman and summary judg-
ment orders.
II. Indefiniteness
On the merits, Schmeisser argues (1) the court erred
by construing the distance-related terms of the ’045 patent
as indefinite, and (2) this error infected the court’s subse-
quent summary judgment and preliminary injunction dis-
solution rulings. We agree on both points.
We review a district court’s determination of indefinite-
ness de novo. Ironburg Inventions Ltd. v. Valve Corp.,
64 F.4th 1274, 1284 (Fed. Cir. 2023). We review determi-
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SCHMEISSER GMBH v. AC- UNITY D. O. O. 7
nations about governing legal standards and intrinsic evi-
dence de novo, and any relevant factual findings about ex-
trinsic evidence for clear error. Id. “[A] patent is invalid
for indefiniteness if its claims, read in light of the specifi-
cation delineating the patent, and the prosecution history,
fail to inform, with reasonable certainty, those skilled in
the art about the scope of the invention.” Nautilus, Inc. v.
Biosig Instruments, Inc., 572 U.S. 898, 901 (2014). “Indef-
initeness must be proven by clear and convincing evi-
dence.” Maxell, Ltd. v. Amperex Tech. Ltd., 94 F.4th 1369,
1372 (Fed. Cir. 2024) (quoting Sonix Tech. Co. v. Publ’ns
Int’l, Ltd., 844 F.3d 1370, 1377 (Fed. Cir. 2017)).
The district court erred by concluding the distance-re-
lated 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. ’045 patent at 12:66–13:45, 14:25–45.
The remainder of the specification explains and depicts
what each distance-related term represents. Id. at 5:64–
67, 6:26–28, 6:55–67, 7:67–8:7, 11:24–30, Figs. 1, 5, 6. The
prosecution history also supports the definiteness of the
distance-related terms where, as here, (1) the claims were
specifically amended to successfully overcome an indefi-
niteness rejection issued by the examiner, see J.A. 216–17
(rejection), J.A. 191–96 (amendment), J.A. 129 (withdrawn
rejection), and (2) the evidence shows the examiner had no
trouble determining whether prior art references met these
limitations, J.A. 217–24 (issuing §§ 102 and 103 rejections
in view of the prior art). Indeed, the district court itself
admits it readily understood the scope of each distance-re-
lated term. See J.A. 19 (acknowledging “‘first distance (A)’
represents the interior distance between the front wall and
the rear wall of the firearm magazine”); J.A. 26 (acknowl-
edging “‘second distance (B)’ is the measurement between
the inside of the two side walls in the quad-stack region of
the magazine while ‘third distance (C)’ is the measurement
between the inside of the two side walls in the double-stack
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SCHMEISSER GMBH v. AC- UNITY D. O. O. 8
region of the magazine”); J.A. 31 (acknowledging “‘offset
(V)’ . . . is simply a ratio of the difference between” second
distance (B) and third distance (C)); J.A. 49–50 (admitting
“the distances are of course measurable once the magazine
is built”). This is all that definiteness requires. Nautilus,
572 U.S. at 910 (a claim term is definite if it “inform[s]
those skilled in the art about the scope of the invention
with reasonable certainty”).
Despite acknowledging the clear meaning and measur-
ability of the distance-related terms, the court improperly
focused on a skilled artisan’s purported inability to calcu-
late or determine specific values for each distance to build
an operable magazine housing. See J.A. 18–32 (focusing on
a skilled artisan’s inability to determine clearance values
necessary to prevent jamming); J.A. 12–14 (stating the def-
initeness requirement “demands that a patent be specific
enough for a [skilled artisan] to be able to build and employ
the claimed invention” (emphasis added)); J.A. 19 (explain-
ing that “if a [skilled artisan] could combine their
knowledge base . . . with the patent to build and use the
invention, 35 U.S.C. § 112(a), then the definiteness re-
quirement will be satisfied” (emphasis added)). These con-
siderations, however, are irrelevant to the definiteness
inquiry, which is distinct from the enablement and written
description requirements. See Augme Techs., Inc. v. Yahoo!
Inc., 755 F.3d 1326, 1340 (Fed. Cir. 2014) (rejecting “argu-
ments [that] appear to be based on the wrong legal stand-
ard, i.e., written description or enablement as opposed to
indefiniteness”). While the court below reasoned that the
distinction is not “so crisp and neat,” J.A. 46, it is a distinc-
tion our precedent has repeatedly recognized. See, e.g.,
Crown Operations Int’l, Ltd. v. Solutia Inc., 289 F.3d 1367,
1378 n.5 (Fed. Cir. 2002) (“[The definiteness] requirement
is distinct from the enablement and description require-
ments . . . .”); Process Control Corp. v. HydReclaim Corp.,
190 F.3d 1350, 1358 n.2 (Fed. Cir. 1999) (“[D]efiniteness
and enablement are analytically distinct requirements,
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SCHMEISSER GMBH v. AC- UNITY D. O. O. 9
even though both concepts are contained in 35 U.S.C.
§ 112.”).
Here, the claims are definite because a skilled artisan
would be able, with reasonable certainty, to look at a fire-
arm magazine housing, identify the claimed distances,
measure them, and determine if the housing falls within
the scope of the claim. That a skilled artisan might not be
able to make the design decisions to successfully build an
operable magazine housing based on the ’045 patent’s spec-
ification goes to the question of enablement, not definite-
ness. Because the court erred by conflating the standards
for these separate legal requirements, it incorrectly con-
cluded the claims were indefinite. Accordingly, we reverse
the indefiniteness-related portions of the court’s Markman
order.
Because we reverse the court’s indefiniteness conclu-
sion, we also reverse the court’s grant of partial summary
judgment in AC-Unity’s favor, which was expressly based
on the erroneous Markman order. J.A. 53–54. We vacate
the court’s order dissolving the preliminary injunction for
similar reasons, see J.A. 4–5 (justifying dissolution based
on the Markman and summary judgment proceedings),
and remand for further proceedings.
CONCLUSION
We have considered AC-Unity’s remaining arguments
and find them unpersuasive. For the foregoing reasons, we
(1) reverse the indefiniteness-related portions of the dis-
trict court’s claim construction and summary judgment or-
ders, (2) vacate the dissolution of the preliminary
injunction order, and (3) remand for further proceedings
consistent with this opinion.
REVERSED-IN-PART, VACATED-IN-PART, AND
REMANDED
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COSTS
Costs to Schmeisser.
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