Bugger. For some reason I saw R hop, but seeing as I've written it I'm not going to delete it!
For flat hop I've done stock packings with eraser nubs, but the easiest way to do it is the Modify Soft Flat Hop and nub for around a tenner. Works a treat.
Idon't know about wide bore barrels but a flat hop works great in stock brass barrels, Prometheus 6.03, ZCI 6.02...
Personal opinion /experience YMMV etc.
Don't bother buying pre made patches. They're a waste of money. Instead buy a metre of EPDM auto hose for a couple of quid.
http://m.ebay.co.uk/itm/250911445211?_mwBanner=1
That gives you plenty to practise on.
Next you'll need a cutting guide to get the patches right for your barrel. Find something that is a snug fit in the barrel and then file /grind a flat on one side so that when you put it into the breech end of the barrel, the flat lines up exactly with the depth of the hop window. I'll get a picture in a bit cos that's a rubbish description.
You can then put the cutting guide into the end of the rubber hose and using a sharp razor blade, slide it along the flat to cut a slice off the side of the hose. With any luck there will be a bit in the middle of the slice that has nice parallel sides. That's the bit you want. Make a nice square cut across the sliver then another to cut the patch to the exact length of the hop window. It should drop into the window without force so it can move without binding. With the patch in place look down the bore and check that it doesn't intrude into the bore AT ALL.
Next put a little chamfer on the front and rear edges of the inside of the patch (just the bit that fits the bore. This is to prevent pinch jams. A bit of 400 grit wrapped around the cutting guide works well. Half a dozen light passes with the abrasive is enough.
Clean the hop window and put the tiniest amount of super glue on the flat faces of the hop window, but only on the edges away from the bore. Stick your cutting guide back in the breech so the rounded side is in the hop window and use this to locate the patch and stop you squashing it too far into the bore.
One the glue has gone off take the cutting guide out and use the razor blade to check the front and rear of the patch aren't stuck to the barrel. It should only be stuck at the sides. Then hold the barrel muzzle down and drop a BB into the breech. It should fall past the R hop patch or at the very most take the minutest amount of pressure to push it past.
For the rubber I like to use Maple Leaf, because they give a great air seal and they're really easy to sand the mound off.
For the nub I use a piece of hard eraser. Remember the stuff from school that was suposed to rub out pen but just wore a hole in the paper? One of those from the discount store should keep you in nubs for a while. Cut it 5mm long, a smidgen under 4mm wide and 3mm tall. File the location bits off the hop arm, drop the nub onto the assembled bucking through the window in the hop up, tiny drop off super glue on the top and press the hop arm down onto it. Done.
If you get this far I'll tell you how to tune it if it's a bit off.
