The Supreme Court Cases on the three strikes rule had nothing to do with using a gun.
*California charged respondent Andrade with two felony counts of petty theft with a prior conviction after he stole approximately $150 worth of videotapes from two different stores. Under California's three strikes law, any felony can constitute the third strike subjecting a defendant to a prison term of 25 years to life. The jury found Andrade guilty and then found that he had three prior convictions that qualified as serious or violent felonies under the three strikes regime."
The opinion is LOCKYER v. ANDRADE at:
http://supct.law.cornell.edu/supct/html/01-1127.ZS.html