Вот классный обзор об китийских м14 и USGI: http://www.canadiangunnutz.com/forum/showthread.php?t=33068
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This information was put together by a very well
known M14 builder Ron Smith of Smith Ent.
USGI or U.S. Several USGI and commercial makers are available. USGI barrels have Chrome lined barrels and can provide very good accuracy. Most commercial barrels are not chrome lined and are going to be of match grade. Barrel accuracy can vary and it does not matter who the maker is. If the barrel is bad it is just bad.
CHINESE Equivalent to USGI barrels. There are two metric threads on the barrel, one for the "Gas Cylinder Lock" and one for the "Castle Nut". The Castle Nut threads are very close to U.S. threads and can be converted, but the Gas Cylinder Lock threads are too fine. We have Clients getting 1" groups with these barrels. They are generally very good barrels, but like U.S. barrels, you can get a lemon.
And here is the info from the rest of that sheet.
USGI: TRW, Winchester(66118), Springfield, Harrington and Richardson are forged and hard. Not all are the same just because they have the same manufacturer. There may be as much as .004" difference from one to another. Check headspace if changing bolts don't rely upon the same brand.
SPRINGFIELD ARMORY Commercial, have not seen many in the last few years but at one time Springfield put out Cast bolts. They need to be replaced.
CHINESE This is the real problem with these rifles. If you or anyone you know has a Chinese rifle, get the bolt replaced. Don't let just anyone do it. We have had many rifles come in that have had a "Gunsmith" or "Armorer" attempt to install a USGI Bolt. They have reworked the Bolt instead of the receiver, we have seen many a good bolt hit the garbage. Almost every Chinese rifle we have had come in to us, whether it has never fired or has had a few hundred rounds through it, has had an excessive headspace. Send us the rifle for our "Bolt Conversion
USGI Made of 416 Stainless Steel, Piston is 416 Stainless Steel, Cylinder Plug is also 416 Stainless Steel. Designed to fight corrosion. In our opinion, don't waste you money on "Titanium" coated pistons. Cylinder, Piston and Cylinder plug can be used on Chinese Barrels.
CHINESE Made of Chromoly Steel, Piston is hard chromed. Piston O.D. and Cylinder I.D. are larger than USGI spec., have had USGI Piston operate in Chinese Cylinders. Cylinder Plug is Chromoly and has metric threads as does the Cylinder Locking Ring. Cylinder, Piston and Cylinder plug can be used with US made barrels and are very reliable and sturdy.
USGI Forged and hard. Manufactured by Winchester, TRW, Springfield, Harrington and Richardson and Sako. Any are great if fit correctly to the receiver
SPRINGFIELD ARMORY Commercial grade are Cast and soft, we have experienced many that are gauled and bent. Replace them with USGI or Chinese.
CHINESE Have tested them and find them equivalent to USGI, they are forged and the last two tested showed a Rockwell between 38-42Rc.
WELDS They are USGI, but welded. We have encountered many that were very well done and usable. Look for bends and mismatched widths. Can be great and are better than cast.
REAR SIGHT ASSEMBLY
USGI Generally operate well on all receivers. Standard have 1" MOA windage and elevation correction and National Match have 1/2" MOA. NM sight assembles need proper attention during assembly. Parts are not interchangeable with Chinese.
CHINESE We have experienced very few that work well. Most of the time the Windage threads of the base were not properly tapped. This causes the sight base to be pushed into the top of the receiver. There is also the difficulty with getting the proper tension for the Elevation Knob so that the sight does not jump during shooting. We have been successful at times in getting these sights to operate at a serviceable level but still are not overly satisfied. Parts are not interchangeable with USGI.
USGI OR U.S. MFG Any stock in serviceable condition is useable. However, just because the wood looks nice does not mean the stock is serviceable. If the rear left corner of the receiver sticks over the stock it is not serviceable. If there is a crack, the stock is not serviceable. Walnut, Laminated and Birch stocks are available as are heavy and light Synthetic stocks.
CHINESE These stocks are dimensionally different and of a lighter wood, but they are serviceable, but we don't like them. If you want to put a USGI stock on a Chinese Rifle, the stock must be worked to fit properly.
USGI Desirable. Forged steel - Hammers, Triggers and Trigger Housing. We have had very few that were not serviceable.
SPRINGFIELD ARMORY Commercial. We have had a few M1A's come in with Cast Hammers and Trigger Housings. While serviceable we do not know how long the hammer will last so we recommend it be replaced. The housing is serviceable, if it is not distorted, but not very desirable.
CHINESE Equivalent to USGI. The last hammers we had tested measured between 48Rc and 51Rc. The hardness is not as deep as a USGI Hammer but we have many Clients that are still using them with no problem.