milsurpcollector Posted December 9, 2006 Report Share Posted December 9, 2006 They way we lap the muzzle of a barrel after crowning seems very imprecise to me. After using precision tools to cut the muzzle a perfect 90deg to the barrel we take a brass screw or other round object and lap with lapping compound. Is this really the best and only way to do this job? Does anyone know why this works so well? Even brownells sells a lapping tool that looks like the head of a brass screw Link to comment Share on other sites More sharing options...
ken98k Posted December 9, 2006 Report Share Posted December 9, 2006 I believe it's the best method available for those of us without a lathe. Link to comment Share on other sites More sharing options...
Doble Troble Posted December 10, 2006 Report Share Posted December 10, 2006 What kenak said +1. I can't imagine being able to cut the barrel with precision without a lathe either. Link to comment Share on other sites More sharing options...
rebel49 Posted December 10, 2006 Report Share Posted December 10, 2006 The tooling is available from Brownells for cutting muzzle crowns, they also have laps to finish lap the crown. It's not cheap, the crown cutters are piloted to the bore. They will get you to within .001" of concentricity with the bore if you are careful. You can also get the lapping compound there, or McMaster-Carr has it. Rebel49 Link to comment Share on other sites More sharing options...
milsurpcollector Posted December 10, 2006 Author Report Share Posted December 10, 2006 I have a brownells crown cutter, and a lathe. I was wondering how the pros lap their muzzles I am still using the brass bolt with lapping compound Link to comment Share on other sites More sharing options...
fritz Posted December 10, 2006 Report Share Posted December 10, 2006 Here is a pic of the hand-turned tools sold by Brownell's. I have used them for years with good sucess--- http://img.photobucket.com/albums/0603/fritz/MVC-029S.jpg fritz Link to comment Share on other sites More sharing options...
680guy Posted December 10, 2006 Report Share Posted December 10, 2006 I don't have a lathe, so I use a hacksaw , round grinding stone and carriage bolt described on Steve Wagner's website. I really had my doubts, so when I cut down a turk barrel, I cut it at 26" figuring if it didn't work a gunsmith could fix it. That rifle is shooting 1/2" groups at 100 yds. Here's the strange part, when I put my Leopold magnetic boresighter on it after it's sighted in, it shows it way high to the left. On my other rifles with factory crowns, once sighted in, all center in the boresighter. This makes me believe that my muzzle cut is not square but somehow the rotary action of the round grinding stone and the carriage bolt with valve grinding compound cut concentric to the bore. Just a theory but in any case the carriage bolt works. Link to comment Share on other sites More sharing options...
eric123 Posted December 10, 2006 Report Share Posted December 10, 2006 I use a bullet (one or two calibers larger than the bore I am lapping)...I cover this with lapping compound and go to town... Link to comment Share on other sites More sharing options...
bilurey Posted December 11, 2006 Report Share Posted December 11, 2006 The NRA ran several interesting tests using M1903A3 milsurps. One test dealt with firing under water to determine results of water filled bore, no explosions or cracked/split parts, just large cloud of black water. Another test dealt with 90 degree muzzle cut, and, fall off in accuracy if this angle was opened. They began milling off the muzzle of a 1903A3 commencing with 90 degrees and increased to an unbelievable angle before point of impact or accuracy were altered. Unfortunately the shifting sands of time have managed to bury most of my memory, believe it was in the 70s. Lots of pics. Any NRA member could likely get the info from them. I've had an on-off relationship with the NRA since the 1970s due to the way members were treated like a herd of sheep. Am currently in the Off mode. I always felt bore wear at muzzle was far more important than crown. Many milsurps have oval bores from careless, but enthusiastic cleaning. I sold my favorite hunting rifle, Win. M95, 35WCF. with 24 inch barrel, as the bore was oval enough to blow every 3 shot group with one wild one. Killed 2 deer and a pig with it, no problems. Even shot a squirrel through the head after listening to him prance around in dry leaves sounding like a buck for about two hours. Then I missed a standing shot at less than 50 yrds., if front of 2 friends, guess it was my time to get a blown shot while hunting. Loved that rifle, but, also had a M95 30-40 carbine which shot where it was pointed. Bill Link to comment Share on other sites More sharing options...
z1r Posted December 11, 2006 Report Share Posted December 11, 2006 Yup, not until the angle got pretty severe (around 45+ degrees) did the affects show. After this point, the angle of departure was quite pronounced. Can you say, "shoot around corners?" Link to comment Share on other sites More sharing options...
odies dad Posted December 11, 2006 Report Share Posted December 11, 2006 I've noticed that many of the AK47's have a slanted muzzle brake. Are these counter bored to lessen the effect of the slanted crown? I would think that the gas deflection that would hold the barrel down would also deflect the bullet up. I guess these aren't designed as target rifles. Link to comment Share on other sites More sharing options...
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