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Is there an accepted method of crowning between centres without skimming the muzzle for a steady? Only way I can think of is to make an adjustable ring to run in the steady so you an dial the barrel in. My headstock is 38” long… And while we’re on the subject, what’s a good method for cutting a traditional rounded crown? | ||
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Crowning between centers is an oxymoron; how can you reach the crown if it has a center in it? Have to hold the breech in a chuck and the end in a study rest. Or dial in your chuck to be perfectly true and hold the muzzle in that. Or use one of the many hand held tools on the market. Lots of ways to do it. For a traditional rounded crown, use this: | |||
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My old lathe was too small in the headstock to take octagon barrels, so to crown I had to use the steady. My technique was to use bondo (auto putty) and cast a donut near the muzzle. Turn the barrel on centers and true the donut. Run it in the steady, and then cut the bondo off after the crown is done. Could use a layer of electricians tape over the barrel before the bondo to protect the finish if the barrel is already finished. A more elegant and reusable solution would be to make a collar that would go over the muzzle and adjust with set screws, and then run the outside of that collar in the steady. | |||
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I like it | |||
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Sure but none of that is crowning between centers. Turning collars on odd shaped parts is good. | |||
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And how would you determone the concentricity between the ID and OD in the chuck? Jim Kobe 10841 Oxborough Ave So Bloomington MN 55437 952.884.6031 Professional member American Custom Gunmakers Guild | |||
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What does the spindle bore of your lathe look like? Is it line bored or a rough casting. | |||
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What does the spindle bore condition mean to anything. Nothing ever touches that. Everyone come on over and we'll do some crowning in various ways. | |||
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A friend of mine used a bearing steady, as pictured, and it worked very well for him. A barrelmaker friend just runs the barrel in the steady. He says, "I turned the barrel; it's concentric." A sleeve on the barrel, trued between centers, is as good a method as any, if done right. The barrel should be cut to length (+.1") before turning the sleeve. Regards, Bill | |||
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And the question about the "banana" shape/runout of the bore, like I mentioned before. Some are good and others, npt so. Jim Kobe 10841 Oxborough Ave So Bloomington MN 55437 952.884.6031 Professional member American Custom Gunmakers Guild | |||
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my apologies, I should’ve said crowning on a steady. I was just using the same lingo as people who say “chambering between centres” - meaning not in the headstock. If I put the barrel in the headstock, I could dial the bore in but it wouldn’t be square r the face, only central. I guess it wouldn’t be on a steady either due to the banana, but at least there’d only be one variable - my 4-jaw’s teeth aren’t overly true… With that tool - do you advance it into the muzzle on one plane, or change the compound for a few angles? And wouldn’t you need an outside and inside cutter with that style? I do like the idea of a sleeve or bondo. I guess you’d use a brass/alloy nipple on the tailstock to protect the muzzle while you’re truing it, or just take 0.1” off afterwards? | |||
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You can do it either way; I just cut off a bit where the center was. You do move the cutter to get the radius you want. Inside and outside cutter? Not sure what you mean. One cutter does it all. Of course if your steady rest is wiggley, or barrel crooked, nothing will work except maybe a piloted crowning tool. If your barrel is crooked then putting a sleeve on it won't help either. However, remember this; only the last 3 diameters of the bore determines where the projectile will go. Results of very extensive testing. (One of my jobs I was the AMC (Army Materiel Command) Program Manager for Muzzle Boresight Devices), and a lot of work went into that. In fact, many barrels are not straight at all, by design and manufacture, and that is all I can say about that. And we are hitting small targets at 3000 Meters. So really, all you have to do is insure that the last inch is running true. I do not use bent barrels however. | |||
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Can you not make a "spider" to fit on the far end of the headstock tube? Then you could dial in the position at both ends. Still doesn't really address the "banana" but I would think if the "banana" is bad enough to cause the crown to be uneven enough to be a problem it will manifest itself in other ways as well? Thinking about it now, if the machine's through-bore is big enough, and you have a spider and a longish gauge pin that fits the barrel well, could you in theory dial it in so that the last inch of the barrel is in line with the lathe, by clocking the gauge pin right close to the muzzle and again a couple of inches outwards? Please note, I am not making suggestions but asking questions. I am not a gunsmith, just an interested amateur trying to learn. | |||
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You're exactly on with both of your thoughts to how most of us do both a chamber job, and a crown. The difficulty with some lathes is the headstock is too long to allow for centering the barrel with a spider. I'm fortunate, mine has a short headstock but about 1-5/8" through hole. | |||
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by inside/outside I meant - that tool only has a radius ground that would contact the bore, if you wanted the radius to contact the outside of the muzzle it would need to be ground on the other side. But I guess you can use the flat at a few different angles. I don’t think my barrel is particularly bent, as far as they go. I was talking generally - as all barrels are bent/banana’d to some degree right? I assumed this means you can’t just chuck them up and centre them in the head stock without a rear spider | |||
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id love to, but as I put in my initial post, my headstock is too long | |||
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You're going to have to grind a bunch of relief on that tool if you're going to use it to crown the bore. Outside edge OK but this won't work for the bore. "Peace is that brief glorious moment in history when everybody stands around reloading". | |||
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Not all barrels are crooked but most are. If the curvature is excessive, the barrel is going to be a pain to fit and chamber, as well as crown. In the years I have been doing this, I have seen one barrel which appeared to be perfectly straight and a bunch which seemed close. Two which were so bad I didn't even try. In general, one does what he can to minimize the errors. Regards, Bill. | |||
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JGS, Coos Bay OR, as readers might know, makes excellent piloted crowing tools. Takes away all the fuss and drama. I've straightened a very few barrels. The object is to ty and determine : If the outside is straight and the bore crooked, I'd just send it back to the maker. Received an integral design barrel once that was visibly crooked..Not sure who was to blame, could have happened in shipping?? A 25 lb shot bag on the bench (or a spare tire), just bring down the barrel with a smack and let inertia do the rest. (Don't overdo the "smack" part) | |||
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I do not straighten barrels; I do not use bent ones; I get them from Douglas; straight, as manufactured. Other makes seem to be bent from what you are saying. I don't know; I don't use other makes. Again, only the last 3 calibers of barrel determines where the bullet goes, and only that part needs to be concentric with the muzzle. Which is why, if your barrel is bent, using a piloted crowning tool works. And my lathe crowning tool like the one in the picture, does reach the bore. That picture is just one from Brownells ad; don't take it too literally. They are also easy to grind and I use one I made. As always, come over and I'll show you how to do stuff. | |||
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thanks for the offer - and I would love to take you up on it if I wasn’t about 9000 miles and an ocean away. Maybe bent is too strong a word - a tiny bit of run out in the centre. Certainly can’t pick it by eye. When you say you only use straight ones - do they have no run out in the centre when on a steady? I ground a HSS bit (well modified a similar one I found in my box of random bits). Bored a bit of scrap alloy, put a wrap of paper round it, drove it on, trued it on the centre, ran it on to the steady and rounded the crown off. I’m quite pleased with how it turned out. What I’m not so pleased about is I’ve discovered this 7x57 barrel is 1:9.75 not the 1:8.75 barrel I ordered. I’m so fed up with this project being stagnant and don’t want to wait another 6 months for a replacement I’m going to run with it hopefully it’ll still shoot 173gr traditional bullets ok or I’ll just use lighter ones - it’s not getting a scope | |||
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Sorry, I missed that. | |||
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There is a very technical set of videos on youtube by Gordy Gritters on precise chambering and precise crowning, taking into account the swoop in the bore. To get maximum use of the scope adjustments, he wants the swoop to be pointed updwards when the barrel is done. Lots of indicating inside the bore. Russ Gould - Whitworth Arms LLC BigfiveHQ.com, Large Calibers and African Safaris Doublegunhq.com, Fine English, American and German Double Rifles and Shotguns VH2Q.com, Varmint Rifles and Gear | |||
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Just thought I clear up a point...The integral I spoke of.. (rib, quarter tib, half round half octagon )was done by a man of high repute, client did the ordering...Whatcha gonna do? BTW, the barrel shot better than "satisfactory" | |||
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I've got a crooked barrel that will kill a ground hog at 953 yards. I missed the one at 1136. How good does it really need to be? Nathaniel Myers Myers Arms LLC nathaniel@myersarms.com www.myersarms.com Follow us on Instagram and YouTube I buy Mauser actions, parts, micrometers, tools, calipers, etc. Specifically looking for pre-WWII Mauser tools. | |||
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I use a lathe with a precision spindle bore that's 2-1/16 ID. I use threaded collars to support the end that's inside the bore then dial in the end I'm working on in a 4 jaw. It's works and they shoot. I quit the steady rest method well over twenty years ago for obvious reasons. | |||
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Same here but my lathe does not have that big a bore, but ample. Jim Kobe 10841 Oxborough Ave So Bloomington MN 55437 952.884.6031 Professional member American Custom Gunmakers Guild | |||
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Is that called a Spider?
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I use a spider, and a 4 jaw; indicate both ends true. Doesn't matter what the inside of the headstock is doing in that case. It's all clearance. A spider has set screws that you center the barrel with. Called a spider because they look like legs sticking out from a center circle. You have to be able to stick the barrel end out of the rear of the headstock to use that. As for bent barrels; I don't like them and don't use them; sign of poor workmanship; however, as indicated above, that doesn't mean they won't shoot. The last K barrel I had here flopped around like a banana. But it shot acceptably. It has been well proven that the last 3 diameters of the bore determine where the bullet will go. One of my jobs was Army PM for Boresight Devices. We did a lot of experiments on that. Mainly with tank cannons. The rest is classified. | |||
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While serving my apprenticeship, we called them "Catheads" Jim Kobe 10841 Oxborough Ave So Bloomington MN 55437 952.884.6031 Professional member American Custom Gunmakers Guild | |||
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Let's see...near as I can remember... a barrel crown serves two purposes: A recess to protect the very end of the rifling from dings, bumps, etc. To allow the escaping gasses to exit the barrel all around the permitter at he same time. Obviously, if the end of the barrel were cut off a 45 degrees, the escaping gas would still be pushing part of the bullet and the gas would have already escaped on another part...Not a recipe for accuracy. So: a recessed crown perpendicular to the bore would accomplish both purposes. Anything else, that serves those purposes is a proper crown. A brass ball charged with abrasive will also do the trick. While at Gander Mountain, a 60 degree piloted countersink was used exclusively and I never saw any reason to argue about the result Oh! BTW,,, forget which book..might have been Clyde Baker, but there is shown a crowning tool bit used with a half center...darn thing works quite well. | |||
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With the prevalent use of suppressors on rifles here, this is the muzzle crown profile now being used. The flat outer perimeter of the crown screws tight against an internal stop in the over barrel suppressor forming a gas seal which protects the outer surface of the portion of the barrel inside the suppressor. I presume the gunsmiths setup to both thread and crown the muzzle at the same time. The image is of the set up for a magnum over barrel suppressor (8.5" over barrel, 5" forward of muzzle) on a X-Bolt 7mm WSM. | |||
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Exactly what I do when I have a barrel that needs to be threaded and/or crowned that can't be stuck through the headstock. If it will fit through the headstock, simple enough to stick a long, snug-fitting gage pin in the bore and dial off it. I've got sets of them just like reamer bushings in .0005 increments for each bore diameter. | |||
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