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Discussion Starter #1 (Edited)
I have a 1942 No4Mk1* that was sporterized before I got it but it was inexpensive and it looked good. So I bought it, and added a few mods of my own to make it personal, my own. In the process of "making it my own" I ended up having to shorten the barrel. I cut it off right behind the front sight. I thought the cut was straight, NOT. I'm currently looking for a tool or method that I can use to re-crown the barrel, and make it shoot straight again. Any tips or information will be put to good use. Thanks


Also if anyone knows any information about a marlin Mod57 lever gun. I have one that is .22LR, and it has stopped firing reliably. I've tried many defferent types of ammo, of ten different types of ammo they all fire abut the same. I disassembled the rifle to find that back end of the firing pin where the hammer strikes the pin has been mushroomed. What I'm wanting to know is if anyone knows how long the firing pin would be if the rifle were new. I've have found a new firing pin, but if I can do a little welding and some filing and fitting, I'd rather try that first, and if I can't get that to work then I'll spend money. Any information on this will be appreciated as well.... Thank
 

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The Troll Whisperer (Moderator)
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First, you've got to square the cut made at the muzzle. Put the rifle in a vise and get the receiver absolutely level. Use a small hand level on the muzzle and square the cut up with a file until perfectly vertical.

You now need to get a crowning kit from www.brownells.com for the .303 brit. Crown to the desired 11 degree cut. Be sure to clean the bore of cuttings prior to firing.
 

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I agree with Kdub on the squaring. Brownells sells a piloted hand cutter that will do that and the 11 degree crown cutter that uses the same handle, if that's what you want? Harold Vaughn did a lot of research on crown angles, though, and found they made no difference as long as true symmetry was achieved. He didn't know who came up with the 11 degree number, but said it had some significance in aerodynamic shapes (Vaughn is a aerodynamics engineer) that is properly applied to a flying object, and thought someone may have confused it with having significance to a barrel crown, which he had demonstrated it did not.

If you can, find someone with a lathe to square the muzzle for you. A 90 degree cut on a lathe does not require perfect centering to be symmetrical (all other angles do), so a three jaw chuck fed through the spindle would be close enough. If not, you may be out of pocket for the squaring cutter? If the barrel is a military type with steps rather than a taper, though, you can use a square to validate your file work.

Once you have it square, one option is to lap a crown angle into place. There is a .PDF file at my file repository that you can download free for instructions on lap crowning.
 

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The Hog Whisperer (Administrator)
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I have hand-crowned a few barrels with a Lee case-trimming tool. No kidding! If you have a bunch of pilots around, find the one that comes closest to fitting the bore size. A few wraps of aluminum (muffler) tape will bring it up to the correct diameter.

Turning by hand will work, but if you have a hand drill with a 1/2" chuck it will go faster.

You'd be surprised how well this will work. If the barrel is larger than 1/2" at the muzzle, well, just tell your friends you have a fancy recessed crown ;)
 

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If you use MikeG's method with a drill use a very slow speed. Reamers and cutters like trimmers are slow speed tools. Use too much speed and it will chatter which will compound your present problem by making more work cleaning up those chatter marks.
 

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I cut the barrel on my 1903 Springfield with a hacksaw and used a square to check it. Yeah, had to file a bit but I was able to get it all squared up nicely. Then I took a round headed bolt and chucked it into a 1/2 drill motor and put a piece of 100 grit carborundum cloth on the bolt. Went at it. Turned out welll. That was in 1960, I was 15. And the rifle will still put them in a minute and a half with the original Weaver 4X. It wasn't brain surgery.
 

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Use a file and a small square to square the end of the barrel. Move the sqaure around checking at different locactions and you can get if very square. Go to the auto parts store and get you some valve lapping compound, usually comes with two in the package, course and fine for about $7. Find you something with a round end that's hard and won't fall into the bore. Valve push rods work great if you can find one that's large enough for a 30cal bore. Chuck it up in a drill and keep lapping the end with the fine compound until you get a nice, clean recess to all the lands, Works great. If you have time and can't find something like a push rod, the ball out of a ball bearing will work but that's takes a whole lot of hand twisting to get-r-done.
 

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Discussion Starter #8
Thanks for the tips guys, don't really know who's I'll try first, they all seem easy enough, and it doesn't seen like brain surgery, should be simple to do, I was just wanting to know some tricks of the trade before I really get into this thing so I don't have to replace the barrel. Thanks again...
 

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The square only works when the sides of the barrel are parallel. If you have a barrel with a taper near the muzzle, you'll be looking for same-size light cracks all around. I think Mike's idea of using a Lee trimmer cutter for the initial squaring is the best economy suggestion. Those are like $10 with a pilot stem. The square cutter from Brownells costs a good bit more. The pilots fit tighter, too, but if you get one long enough on the Lee it will still keep the cutter pretty square.

I've seen the bolt head and drill method done a couple of times with success. But when I went to try it myself after seeing it mentioned in a magazine article many years ago, I discovered most "round head" bolts actually have heads with an elliptical profile. So you either have to center the drill perfectly or err evenly all around while cutting to get true symmetry. A ball bearing with some lapping compound grooves Dremeled in with a cutoff wheel will center and be symmetrical regardless of it being biased a little off-axis by whatever turns it. That way it better guarantees a symmetrical crown. I still rotate the barrel part way every few lapping cycles to ensure that. It probably takes me five minutes to do the coarse cutting of a crown by that method. Gun barrels aren't all that hard.

The other issue is more cosmetic than practical, but as anyone who's lapped valves for an engine will tell you, rotating the lap in just one direction creates score marks. The back and forth motion of the old eggbeater type valve grinding tools eliminates that, as does the palm motion described in my .PDF file. The crowns then come out uniformly smooth, and if you want to prove it to yourself, you can step up through abrasive grit grades to a polish to take one all the way a smooth, scratch-free mirror finish. I usually stop at 800 grit, figuring that will cold blue, rust blue, or Parkerize nicely, which it does.
 
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