Absolutely and totally wrong.
Here is the overview with all details.
{...
It is legal for all adults unless they are prohibited from possession of firearms. Wisconsin state law 948.60(2)(a) states: "Any person under 18 years of age who possesses or goes armed with a dangerous weapon is guilty of a Class A misdemeanor." However, the exceptions are: “when a person under 18 possesses a rifle or shotgun” and "when the dangerous weapon is being used in target practice under the supervision of an adult or in a course of instruction in the traditional and proper use of the dangerous weapon under the supervision of an adult."
[8] Wisconsin statute 948.60(3)(c) states: "This section applies only to a person under 18 years of age who possesses or is armed with a rifle or a
shotgun if the person is in violation of s. 941.28 or is not in compliance with ss. 29.304 and 29.593."
[9]\...}
Here is the actual statute:
{...
(2)
(a) Any person under 18 years of age who possesses or goes armed with a dangerous weapon is guilty of a Class A misdemeanor.
(b) Except as provided in par.
(c), any person who intentionally sells, loans or gives a dangerous weapon to a person under 18 years of age is guilty of a Class I felony.
(c) Whoever violates par.
(b) is guilty of a Class H felony if the person under 18 years of age under par.
(b) discharges the firearm and the discharge causes death to himself, herself or another.
(d) A person under 17 years of age who has violated this subsection is subject to the provisions of ch.
938 unless jurisdiction is waived under s.
938.18 or the person is subject to the jurisdiction of a court of criminal jurisdiction under s.
938.183.
(3)
(a) This section does not apply to a person under 18 years of age who possesses or is armed with a dangerous weapon when the dangerous weapon is being used in target practice under the supervision of an adult or in a course of instruction in the traditional and proper use of the dangerous weapon under the supervision of an adult. This section does not apply to an adult who transfers a dangerous weapon to a person under 18 years of age for use only in target practice under the adult's supervision or in a course of instruction in the traditional and proper use of the dangerous weapon under the adult's supervision.
(b) This section does not apply to a person under 18 years of age who is a member of the armed forces or national guard and who possesses or is armed with a dangerous weapon in the line of duty. This section does not apply to an adult who is a member of the armed forces or national guard and who transfers a dangerous weapon to a person under 18 years of age in the line of duty.
(c) This section applies only to a person under 18 years of age who possesses or is armed with a rifle or a shotgun if the person is in violation of s.
941.28 or is not in compliance with ss.
29.304 and
29.593. This section applies only to an adult who transfers a firearm to a person under 18 years of age if the person under 18 years of age is not in compliance with ss.
29.304 and
29.593 or to an adult who is in violation of s.
941.28.
History:
1987 a. 332;
1991 a. 18,
139;
1993 a. 98;
1995 a. 27,
77;
1997 a. 248;
2001 a. 109;
2005 a. 163;
2011 a. 35.
Sub. (2) (b) does not set a standard for civil liability, and a violation of sub. (2) (b) does not constitute negligence per se. Logarto v. Gustafson,
998 F. Supp. 998 (1998).
...}
You have to go deeper into the hunting exception to read about gun length, and the point is the hunting exception simply becomes unusable if the rifle is too short.
Rifle length no way allows Kyle to be in possession.