Dave Thompson, chief constable of West Midland's Police says the "fast parcel system" was becoming more common for criminals to smuggle guns.
Mr Thompson says criminals are using new tactics to import illegal firearms into the country, often sending component parts separately.
"We have to watch a trend of disassembling the weapons and sending them in component parts," Mr Thompson said.
However, firearms and weapons expert David Dyson told Sputnik that the smuggling of guns through the postal service "has been going on for years."
"There have been concerns about firearms being sent and received in the postal service for some time. Criminals wanting to get a gun into the UK will exploit every opportunity — that could be the postal service — or smuggling weapons through customs.
"The authorities have to concentrate on every potential avenue that criminals might exploit —not just one to stop the illegal gun trade."
There are fears that once firearms reach the UK, they could fall into the hands of potential terrorists. However, concerns that it is due to the "fast parcel system" have led to "a lot of pro-active policing," says Dyson.
"It could be that more component parts are being sent — or that the police are getting better at identifying them. Parcels do get X-rayed and if the authorities see it's a gun, they may even send an officer to deliver it and once it's signed for, they can raid the property," Dyson told Sputnik.
As the law stands in Britain, smuggling a component part of a weapon is considered the same offence as smuggling a complete barrel.
A man who tried to buy guns and ammunition on the dark web was recently sentenced to six years in jail. Montgomery Richard Kyle Byrne was arrested by Britain's National Crime Agency (NCA) in August 2015.
Officers searched his home and found a Smitt Ruben sniper/hunting rifle, a sawn off shotgun, a revolver and over 200 rounds of ammunition, cartridges and bullets.
They also found an ammunition press, firearms powder, bullet heads and percussion caps — components for producing ammunition that could be discharged by the various weapons.
Issuing a warning following Byrne's sentencing, Brent Lyon from the NCA's Armed Operations Unit said: "If you buy guns on the dark web you leave a digital footprint — and the NCA will do everything it can to identify you and hold you to account."