By Bryce Towsley
“Only accurate rifles are interesting” — Col. Townsend Whelen
I can’t say I agree with the good Colonel on this, because I’ve had some poor-shooting rifles that were darn interesting. But I will concede that accurate rifles are a lot less aggravating.
If you have accuracy problems with a gun that has always shot well but has suddenly gone sour, my advice is to take these steps:
First, clean the bore until all copper fouling is removed. This can take an unbelievable amount of time and work to get it right. But in more than half the cases, it will fix the accuracy problem. When somebody brings a rifle to my shop that’s not shooting well, the first thing I do is clean the bore. Most of them will argue with me and say, “I already cleaned the gun, and you’re wasting your time.” So I don’t even tell them how I got the gun to shoot again. I just let them think I am a miracle worker.
Next, make sure all screws are tight and that the stock has not cracked or warped. Still not shooting? Replace the scope. If it’s still not back to its former accuracy potential, recrown the barrel.
The crown is the point in the muzzle that is at the end of the barrel. It’s the last place that the rifle has any physical influence on the bullet, and it is critical that it be perfect. The crown must be perfectly square with the bore, perfectly round and free from any defects. Even the slightest imperfection can impact the bullet as it exits the barrel and have an adverse affect on accuracy. One of the major rifle makers in the country told me that when a rifle comes in for repair with a poor accuracy complaint and no obvious defect is found, the first thing they do is recrown the muzzle. In a surprising number of cases, that corrects the problem.
I have seen a lot of poor crowns right from the factory. I have one .45-70 rifle that had a big ding in the crown when I received the rifle. It would only shoot into about 3 inches at 100 yards. I recrowned the barrel, and now it groups at half that.
A lot more rifle crowns have become damaged in the field. It only takes a moment of inattention to set the muzzle down on a jagged rock, and the damage is done. But the best way I know to ruin a rifle crown is by riding in the truck with the muzzle of the rifle down on the floorboard. The collected dirt and sand on the floor is abrasive, and it grinds away at the delicate edges of the crown. If you must have the gun pointing down in a vehicle, at least protect the muzzle with something to keep it out of the dirt.
The simplest way to correct minor crown damage is with an inexpensive Brownells Brass Muzzle Crowning Lap. This is a tapered “cone” of brass with a stem to allow it to be inserted into a drill. The idea is to “lap” the final edge of the bore until it is completely concentric and at a perfect 90-degree angle to the bore, smooth and free from any imperfections.
Before starting, plug the bore of the rifle with a tight-fitting cloth patch and leave it about 4 inches down from the muzzle. Put the lapping tool in a variable-speed drill, coat it well with 600-grit lapping compound and insert it into the bore until it contacts the muzzle. Start the drill and rotate the lapping tool at slow to moderate speed while slightly wobbling the drill. After 10 seconds or so, reverse the direction of rotation and continue to wobble the drill.
It’s better to work slow and check often, so stop and wipe the compound off the muzzle and check your progress. There will be a bright ring on the muzzle from the lapping compound wearing away the metal. It should be completely around the bore and extend to the bottom of each of the rifling grooves and to the top of the lands. The best way to inspect it is with a magnifying glass or with a magnifying headset like those used by jewelers. If the ring is still not complete, put some more lapping compound on the tool and continue.
When you have a clearly defined ring all around the muzzle, all the way to the inside edge and to the bottom of the rifling lands, you’re done. It’s that simple.
If you want a more professional and contemporary looking job, consider using Brownells Muzzle Crowning Cutter with the appropriate pilot. Brownells also offers a cutter called the Muzzle Facing Tool, which squares the muzzle to the bore. It’s not necessary to do this, but it makes for a more finished look. Just remember that the metal will be bare after cutting. You can leave it like that or reblue or finish it with a coating.
Use the muzzle-facing cutter first, and remember to use plenty of cutting oil with any cutter. Insert the pilot in the bore and turn the cutter until you have achieved the desired result. The cutter can be turned by hand or with a handheld drill. Then put the pilot on the crown cutter and cut an 11-degree crown. (Actually it’s 79 degrees, but it’s commonly called 11 degrees. That’s because 90 degrees, minus 11 degrees is 79 degrees.) Brownells also has a 45-degree cutter that can be used for a deeper crown that’s better protected from field damage. Finally, finish with a brass lapping tool to just break the edge.
Push the plug out of the barrel from rear to front. Then wipe the bore with a few solvent-soaked patches to clean the residual lapping compound. Always work from the rear or action end of the gun and push the patches out of the muzzle so that the gunk is not pushed into the action. Finish with a dry patch.
If the gun still doesn’t shoot well, it might be time for a new barrel or a trade.
(800)741-0015 / www.brownells.com
Reprinted from the September 2005 issue of Buckmasters GunHunter Magazine. Subscribe today to have GunHunter delivered to your home.