What Does "Pressing In A Barrel" Mean?
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lilguy
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For the older crowd who don't watch video, the AK and a lot of other traditional firearms literally force the barrel into the receiver under pressure, while simultaneously gauging the chamber length for head space. It's definitely technical and involves some equipment that isn't part of the norm for most home garages. The basic issue is that the locking lugs for the bolt are in the receiver but the chamber is part of the barrel, and the overall length has to be precisely set.
In barrel extension designs like the M-16, the head space is set by screwing the extension on - by hand operation - to set the overall chamber length. It's much faster, doesn't take a press, and increases accuracy while not requiring a gunsmith level technical education. Stoner's designs involved a lot of assembly improvements that go unrecognized. Because of that barrel extension, the bolt locks into it, not the receiver, which makes the upper and lower much less stressed. An AR barrel assembly can chamber a round, lock in the bolt, and be fired by a tap on the firing pin. A traditional pressed assembly would have the receiver attached to lock in the bolt.
This is why there is an incremental loss of weight for barrel extension designs as the receiver isn't stressed and doesn't need to be as heavy - so designers are free to use aluminum, carbon fiber, even polymer.
In barrel extension designs like the M-16, the head space is set by screwing the extension on - by hand operation - to set the overall chamber length. It's much faster, doesn't take a press, and increases accuracy while not requiring a gunsmith level technical education. Stoner's designs involved a lot of assembly improvements that go unrecognized. Because of that barrel extension, the bolt locks into it, not the receiver, which makes the upper and lower much less stressed. An AR barrel assembly can chamber a round, lock in the bolt, and be fired by a tap on the firing pin. A traditional pressed assembly would have the receiver attached to lock in the bolt.
This is why there is an incremental loss of weight for barrel extension designs as the receiver isn't stressed and doesn't need to be as heavy - so designers are free to use aluminum, carbon fiber, even polymer.
pdsmith505
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Unlike AR-15's, where the barrel is secured to the receiver with a nut, AK barrels are pressed into the front trunnion and secured with a pin. How far the barrel is pressed in at this point also determines the headspace of the bolt/chamber
lysanderxiii
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Not only AKs and Chinese SKSs, but the CETME and HK rifles use 'press-and-pin' to secure the barrel in the receiver.
It does allow for a slimmer design.
It does allow for a slimmer design.
lysanderxiii
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Only the Chinese SKSs made for import were pressed, as I recall.
None of the Russian ones though.
None of the Russian ones though.
caribou
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The Germans started such with their G-43 semi auto battle rifle series.
Pushed in and pinned, kinda stunnned the Americans , who studied such after the war....same amazment they had about the MG-42....they thought it was a 'last ditch' type weapon at first, being made of sheet metal and alll, but they eventually realized it was nothing more or less than expedient wartime manufacturing genius
Pushed in and pinned, kinda stunnned the Americans , who studied such after the war....same amazment they had about the MG-42....they thought it was a 'last ditch' type weapon at first, being made of sheet metal and alll, but they eventually realized it was nothing more or less than expedient wartime manufacturing genius
Jenrick
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Depending on the attachment of the barrel to the receiver, pressing the barrel can be a simple machining operation done by someone with no skill. The receiver end of the barrel can then be milled down (or lathe cut depending) by someone with more skill to create the correct dimensions for the chamber quickly. With the correct tooling, you could probably even trim the excess "chamber" portion of the barrel down without any real knowledge of gun smithing.
-Jenrick
-Jenrick
lysanderxiii
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Yeah, but we couldn't get one to work worth a damn...
"First Report on Test of the .30 Cal Light Machine Gun, T24"
Baron_Null
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Just in case the OP isn't too versed in mechanical concepts in general, here's a brief overview.
Pressing when it comes to assembly of mechanical parts usually refers to the act of using a tool to most literally press a part into a designated place on another part. This works because the hole in the part that is being pressed into is generally very precisely sized under the diameter of the part that is being pressed. This is referred to as an "interference fit." Because the material's inner structure usually doesn't completely deform to the new diameter, it is held in place. If one requires that the parts fit together and stay together under a good deal of force, you can use a pin that goes through both of the pressed parts at the same place, which will prevent them moving more than the pin will allow. To my knowledge (though I may be incorrect) most firearms with pressed barrels are also pinned.
This opposed to the other common method of barrel to receiver assembly, in which the barrel and trunnion are both threaded much like a nut and bolt, and assembled in much the same way.
Of course, they both have their upsides and downsides when it comes to assembly. What those are, and as to the potential upsides and downsides of either method, I'll leave to those with far more experience than I.
Pressing when it comes to assembly of mechanical parts usually refers to the act of using a tool to most literally press a part into a designated place on another part. This works because the hole in the part that is being pressed into is generally very precisely sized under the diameter of the part that is being pressed. This is referred to as an "interference fit." Because the material's inner structure usually doesn't completely deform to the new diameter, it is held in place. If one requires that the parts fit together and stay together under a good deal of force, you can use a pin that goes through both of the pressed parts at the same place, which will prevent them moving more than the pin will allow. To my knowledge (though I may be incorrect) most firearms with pressed barrels are also pinned.
This opposed to the other common method of barrel to receiver assembly, in which the barrel and trunnion are both threaded much like a nut and bolt, and assembled in much the same way.
Of course, they both have their upsides and downsides when it comes to assembly. What those are, and as to the potential upsides and downsides of either method, I'll leave to those with far more experience than I.
Sovblocgunfan
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For AK's (.30 cal versions, at least), instead of a barrel press you can also use a piece of allthread run down the trunnion and barrel with sturdy washers and nuts on each end. Turn the nuts on one end to tighten and the barrel pulls itself into the trunnion. The inclined plane on the allthread provides enough leverage to serve as a makeshift barrel press. It allows for pretty fine adjustment and doesn't require a special tool purchase for one build-only some hardware that doesn't cost much.
Actual barrel nut design on the AR incorporates teeth to act as a locking measure to keep the nut from loosening - the gas tube passes between them. Add a delta ring assembly on top of that and it does get bulky.
Other firearms designers pin the nut differently and the "bulk" is trimmed considerably. If that is part of a free float assembly for an AR it can all be done under the tube with nothing bigger than the upper dimensions continued. Not to forget Savage rifles use a barrel nut and there are no complaints about a bulky ring. http://www.shootingtimes.com/long-guns/longgun_reviews_stevens200_041106/
We are going to see more makers moving to barrel nut attachment as it's simpler, cheaper, and easier in assembly. Pressing a barrel into a trunnion is an old school dinosaur method that prevents owner modification. Makers can't have that or they won't be able to sell another gun.
Other firearms designers pin the nut differently and the "bulk" is trimmed considerably. If that is part of a free float assembly for an AR it can all be done under the tube with nothing bigger than the upper dimensions continued. Not to forget Savage rifles use a barrel nut and there are no complaints about a bulky ring. http://www.shootingtimes.com/long-guns/longgun_reviews_stevens200_041106/
We are going to see more makers moving to barrel nut attachment as it's simpler, cheaper, and easier in assembly. Pressing a barrel into a trunnion is an old school dinosaur method that prevents owner modification. Makers can't have that or they won't be able to sell another gun.
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