01-24-2016, 08:13 PM
About 30 years ago, I took up benchrest shooting. My first rifle was based on a Rem 700 action. My gunsmith who had assembled many very accurate rifles, some setting national records, explained that the receiver had to be trued. The theory is that everything must be square/parallel to the bore. He lapped the locking lugs, squared the bolt face, squared the receiver face, trued the receiver threads, and god knows what else. When all was done, I had a shooter!
Advance now to the present, and I'm into ARs. But I feel the same principles apply. I've bought a RRA in 223, and a PF in Grendel. Col Townsend Whelen's remark about "only accurate rifles are interesting" still guides my behavior. I am completely amazed that a semiauto, especially with all those moving parts can be so accurate. As I see it, the weak spots in an AR are the barrel to receiver fit, locking lugs, fit of bolt in carrier, and the carrier itself rattling down the receiver. Most of these areas require faith that there is a proper fit. The one area that you can control is the barrel to receiver fit.
Enter the lapping tool. Remember, the tool guides on the same raceway as the bolt carrier. So any adjustment to the receiver face will be square to the carrier, which in turn, will be parallel to the bore.
If you are assembling a new rifle from parts, it doesn't hurt to check it for square. If an existing rifle shoots to your expectations/satisfaction, then it ain't broke. If not, break out the lapping tool.
Advance now to the present, and I'm into ARs. But I feel the same principles apply. I've bought a RRA in 223, and a PF in Grendel. Col Townsend Whelen's remark about "only accurate rifles are interesting" still guides my behavior. I am completely amazed that a semiauto, especially with all those moving parts can be so accurate. As I see it, the weak spots in an AR are the barrel to receiver fit, locking lugs, fit of bolt in carrier, and the carrier itself rattling down the receiver. Most of these areas require faith that there is a proper fit. The one area that you can control is the barrel to receiver fit.
Enter the lapping tool. Remember, the tool guides on the same raceway as the bolt carrier. So any adjustment to the receiver face will be square to the carrier, which in turn, will be parallel to the bore.
If you are assembling a new rifle from parts, it doesn't hurt to check it for square. If an existing rifle shoots to your expectations/satisfaction, then it ain't broke. If not, break out the lapping tool.
Life is too short for cheap rifles, cheap bourbon, or cheap women.