The pull through threaded line looks like a good idea to me. I would be very careful, though, not to risk stripping the plastic threads and leaving a brush or jag snagged in the barrel. Beeman's makes a nice cleaning kit with a nylon-coated cable and brass fittings that comes with .17 and .22 cal brushes and a loop. I have one and it has served very well for my air rifles.
No expert on metallurgy here, but bronze and brass are both harder than lead. And bronze and brass alloys can vary significantly in hardness, depending on the composition (primarily tin and copper, as I recall, but also small amounts of other metals). Bronze and brass, like lead, can indeed accelerate wear and potentially scratch or damage the rifling or crown. Like all things air gun and fire arm -- use them carefully, and like most things in life, use them with moderation.
My return to the very dark side of powder-burning rifles in .17 HMR, .22LR, and .223 prompted me to purchase two high-end cleaning rods. I tried a Gunslick carbon fiber 36" one piece rod in .22 (from Sportsman's Warehouse) and a Dewey nylon coated 36" one piece rod in .17. Each was around $30 bucks. The Gunslick is probably the better rod, bot both are good. I also ordered a dozen each of the .17 and .22 bronze and nylon brushes and cotton gun mops, .17 and .22 loops, and a set of rifle jags. I also ordered some bulk round cotton patches in small and large sizes and already had some J-B Bore Compound and Kroil. All these are available at Brownells.
My previous cleaning rods had been the standard Hoppe's 3-piece aluminum types. I must say that either the Dewey or Gunslick rods are much MUCH better. The rods are seated with ball bearings at the handle so that the rod/jag rotate freely in the rifling, and they have precision brass fittings that mate with the cleaning attachments without a hint of any rough or exposed edge. The loops and brushes are all bronze, not steel, and have a small diameter looped end with absolutely no rough metal exposed at the tip of the brush. The old aluminum 3-piece rods are now delegated to cleaing shotgun barrels only.
My recent experience has taught me that it is much better to use a nylon coated or carbon fiber 1-piece rod with a properly fitted jag and patch to clean a rifle barrel. Two or three passes with the right rod and a properly fitting brush, jag/patch are much more efficient than dozens of passes with a piece of plastic weed trimmer line and a cloth patch. Fitted round cotton patches work much better than square patches. And for most air rifle barrels, I think I would suggest using a nylon brush with GooGone rather than a bronze brush, followed with dry cotton patches over a jag. This is a very efficient and safe way to clean the bore of an air rifle. If you are using powder solvent on a fire arm, bronze or brass brushes are fine. If you are using copper solvents to remove fouling from FMJ rounds, the copper solvents will also tend to work on the brass or bronze brushes over time, so I would suggest a nylon brush for application of the copper solvent, then leaving it "wet" in the barrel for a few hours or over night, then cleaning with dry patches until every trace of green is gone, then cleaning and oiling the barrel in the usual fashion. Penetrating, metalophyllic oils used sparingly seem to be what most of the pros use. Rem Oil and Kroil are frequently mentioned, but of course, these types of oils would not be what you want to use in a springer air rifle, because of detonation. I suppose that they could be used sparingly in PCP's and CO2 rifles with good results, though. I haven't ever used oil on an air rifle barrel, though.
If you must clean from the crown end, brass introducers are available to protect the crown. If you clean from the bolt end, as with the bolt action .17HMR, .22 and .223 rifles, there are introducer sets that protect the action from the cleaning rod and solvents. And if you are cleaning any sort of air rifle with baffled brakes (Whisper, shrouded PCP;s like the AA-S410 for example), an introducer like a soda straw should be used to make sure the cleaning rod or line passes through the baffles without snagging or doing any damage.
In short, consider carefully what you risk if you damage your barrel or crown cleaning an expensive air rifle improperly. Like many things in life, one mistake is all it may take to do irreparable damage to the accuracy of your favorite shooter. Take care. Be safe. Have fun.
