One picture is worth a thousand words. Two pictures tell the whole story. Consider our jags and brush guides cheap insurance for your crowns.

Jags

45 Caliber Reverse Taper Rifle Jags with wedge points
and 8-32 male threads. We can provide any common
thread, be it male or female, that would meet the
customer's rod requirements. Male threads are
accomplished by installing the appropriate size
stainless steel set screw.
Jags from 40 caliber and up are made in this style,
either with wedge points or patch piercing points.

At this time I have designed jags for these calibers: .223, .243, .257, .264, .270, .284, .308, (32 cal., 325 WSM, 8mm), .338, and .375. I have also designed reverse taper rifle jags for the following: 40cal., .416 Rigby, 44 cal., 45 cal., .470, and 50 cal. More calibers will be added as time permits for design and testing to be done.
Two of the leading attributes of my jags are that the joint between the rod and the jag and the segments that hold the patch will never come in contact with your bore or crown after complete insertion into the bore. After the patch clears the muzzle, the long bore riding shoulder should allow you plenty of time to stop, thereby not allowing the joint between the rod and jag to come in contact with the bore and crown area. The long shoulder also prevents the patch holding segments from coming in contact with your crown when you pull the jag back in. The only thing that should ever come in contact with your crown, while using my jags, is a just under bore size gentle piece of Acetron GP.
A third attribute that many of my customers enjoy is the fact that the Acetron GP material that my jags are made of will not give off a false copper fouling indication like most other jags will.
The jags are designed to be used with round patches. Some square patches will work if they are not too big. If they are too big the tails from the folded over material will come in contact with the surface of the long shoulder and prevent the patch from passing down the bore.
The long guiding bore riding shoulders on my modern caliber jags, run about .006" under bore size. The long shoulders on the reverse taper jags are about .015" under bore size. Therefore, you can see if patch material tries to occupy this space you may not be able to get the patch and jag combination down the bore. The width and spacing of the segments that hold the patch are designed to provide optimal surface contact for each caliber when used with the appropriate patch.
The .223 jag uses 1 1/4 " diameter patches. The .243, .257, .264 and .270 jags use 1 1/2" diameter patches. The .284, .308, (32 cal., 325 WSM, 8mm), .338 and .375 jags use 2" diameter patches. Patches like those sold by Sinclair's International in Fort Wayne, In. 800-717-8211 (www.sinclairintl.com) are highly recommended. 
The reverse taper jags work equally well with either the 2" round arsenal patch or up to a 2 1/2" square cotton patch. The 2" round arsenal parches are available from Buffalo Arms Co. in Ponderay, ID. 208-263-6953 (www.buffaloarms.com). They are the preferred patch of the black powder cartridge rifle community
308, 243 and 223 Extra long jags.
This is an option that will allow patches to clear muzzle
brakes, tuners, etc. while a portion of the long bore riding
shoulder still remains in the bore
As you view the different jags, you will notice that some of them have what I refer to as a "wedge tip". This tip was developed to help assure that the patch falls off when pulling the jag back into the muzzle (especially important when wiping between shots). The wedge tip along with the patch piercing tip is offered on any custom jag I make at no extra charge. Custom jags are also threaded and tapered to match your specific rod requirements thereby eliminating the need for adapters. Male threads are accomplished by installing the appropriate stainless steel set screw into the end of the jag. I also turn a 60 degree inclusive angle taper on the rod end of all my jags to match the rod diameter. If you should by accident push my jags clear of the muzzle this taper allows you to gently pull the jag back in over the crown.
I also make custom jags for those rifles with tuners, flash suppressors or recoil reducing devices. I do this by making the jag with a longer then normal shoulder so that when the patch exits the device part of the long bore riding shoulder area is still in the barrel. These are custom made to various lengths depending on the length of the device that the patch has to clear. Note: The customer needs to provide the length from the end of the muzzle to the end of the device prior to us giving a quote. Prices for these are quoted individually upon request.