James Fraughan was arrested after police recovered the semi-automatic Baikal handgun at a property in Coral Drive in Bootle.
Police said officers attended the property at around 4.10am, on Sunday, July 22, 2018, following reports a man had a gun.
Fraughan, 29, of Markfield Road, Bootle, and Sam Taylor, 28, of St Alban's Square, Bootle, were arrested later that day.
Fraughan was charged with possessing a prohibited firearm, a firearm without a certificate, and ammunition without a certificate.
At a hearing on Friday he admitted possessing a firearm without a certificate and ammunition without a certificate. The charge of possessing a prohibited firearm was dropped by the Crown.
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Taylor faces four charges in relation to the weapon, all of which he denied in a previous hearing.
He denies possessing a prohibited firearm, the same weapon without a firearms certificate, and possessing ammunition without a certificate.
Taylor also denies possessing the gun when prohibited from doing so, because he has previously served a 40-month sentence in a young offenders institution.
Cheryl Mottram, prosecuting, said a trial, estimated to last two days, could be held on the week commencing July 5 next year.
Judge Garrett Byrne remanded Taylor on bail until that date.
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On Friday, Judge Stuart Driver, QC, said Fraughan would be sentenced on a date to be listed at the conclusion of Taylor's trial and remanded him on unconditional bail.
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