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Posted: 8/18/2014 7:37:40 PM EDT
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I thought I knew but now have to ask.
What is the difference between regular rifling and button rifling? http://www.mcgowenbarrel.com/barrels.htm The rifling is called lands and not grooves? |
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Cut rifling uses a tool to scrape the grooves into the barrel
Button rifling drags a hardened "button" down a bored barrel impressing the rifling Hammer forging is a process where a rifled mandrel is inserted into a slightly oversize bore and then the barrel is hammer forged into it. The mandrel is then removed. |
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The lands are the rifling as I understand it because they are what engraves the bullet and causes it to spin.
There are different ways to rifle a barrel you can have cut rifling which requires multiple passes of the cutter to cut each groove individually. There is broach cut rifling which isn’t really done any more because the broaches are expensive and wear out quickly Button rifling is quick to do and cheap as well as being very consistent and repeatable. It involves a button i.e. piece of tool steel with riflings cut into it and it is then forced down the barrel sometimes using hydraulic pressure. Cold hammer forged barrels are hammered around a mandrel with the riflings and sometimes even the chamber already formed on them. This method produces a finished bore and chamber quickly and with very close tolerances but the forges are cost prohibitive for most manufacturers. Button rifled barrels don’t seem to require as much lapping in my experience when compared to cut rifling but when you look inside a cold hammer forged barrel you will see absolutely no tool marks with the naked eye. It’s a matter of different techniques. Hope that helps |
| Cold Hammer forging is generally considered to produce a longer lasting barrel, though not necessarily the most accurate. CHF barrels can, under conditions of identical use, often exceed twice the round counts of barrels produced by other methods. Some of our Steyr AUGs have 20K+ rounds through them, and still produce acceptable accuracy. |
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Quoted:
Cold Hammer forging is generally considered to produce a longer lasting barrel, though not necessarily the most accurate. CHF barrels can, under conditions of identical use, often exceed twice the round counts of barrels produced by other methods. Some of our Steyr AUGs have 20K+ rounds through them, and still produce acceptable accuracy. The main benifit of the hammer forge method is uniformity. All the barrels from the same mandrel will theoretically be the same except for minor surface wear on the mandrel. So if you get 1000 uses before a mandrel is out of spec then all 1000 should be nearly the same. Hand cut multi pass is normally the most accurate of the methods. It's hardest to reproduce, discard rates are higher, and even the most skilled barrel smith can have a bad day. Button rifling seems to fall somewhere in the middle. |
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Lands and grooves are a pattern of rifling.
Button rifling is a manufacturing method. Apples and produce trucks. Button rifling pulls a round swaging tool that's cut to the opposite of the desired rifling through a smooth bored hole in the steel bar to create rifling in a single pass. Cut rifling (aka single point rifled or single point cut) uses, unsurprisingly, a cutter with a single point that methodically cuts out the grooves in the barrel using many pulls though the barrel. Hammer forging uses a very hard mandrel with the opposite of the desired rifling, it's inserted into a hole in the steel bar, and massive presses compress the barrel steel around the mandrel to form it against the rifling. There are long-mandrel and short-mandrel forges, long is where the mandrel is the full length of the finished barrel and the barrel does not move in relation to the mandrel. Short is where the mandrel is just long enough to fit the forging area, and the barrel moves over the mandrel and is progressively formed. Long mandrel forging can create the rifling in the bore, as well as the chamber and even the exterior barrel profile depending on the complexity of the forge. Short mandrel just creates a rifled blank which has to be chambered and finish machined just like a rifled blank from cut or button rifling. Here's some more info including a few other processes like broach cutting and electrochemical machining. Click the "next page" link at the bottom to go through the various pages: http://projects.nfstc.org/firearms/module04/fir_m04_t06_05.htm |
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