As long as you rely upon the flow of water through that pin for water pressure, increasing the flow rate is impossible. You're along the right lines.
The only method I know of to have the water flowing at mains pressure is to buy a proper brass outside tap of the type shown here:
http://www.toolspot.co.uk/product/brass-outsid e-garden-tap
This type of tap has a 15mm compression fitting at the supply end. You'll need to turn the rising main water supply off and then drain the cold water out of the pipe by turning on the nearest house internal cold water tap until the flow stops.
The next step is to remove about 30cm length of the copper pipe into which you screwed the supply valve for the outside tap. Replace the length with new sections of copper pipe using compression couplers at either end but also fit a compression T piece somewhere along on the new pipe. You can then take a feed from the T piece to the outside tap either via more copper pipe into the tap compression fitting or fit a suitable flexible hose section, which is available from most plumbers merchants or DIY superstores.
Others will tell you to use Speedfit or plastic push fit connections for this job. It's all down to personal preference. I prefer solderable fittings myself but I've also used compression fittings.
Finally, don't forget to protect the pipework from frost if it's against an outside wall.