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Posted: 7/23/2005 11:46:17 PM EDT
| How is headspace adjusted? |
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Headspace (HS) is defined as the distance from the bolt face to a datum point in the chamber. HS is set by the barrel maker who reams the chamber for a given rifle. The barrel extension (BE) is screwed onto the breech end of the barrel. The BE stops when it reaches the shoulder of the barrel. The bolt fits into the BE and then rotates to lock up into battery. HS is measured from the point of bolt lockup to a datum point in the chamber. A GO gauge is inseted into the chamber and the the bolt is inserted into the BE. If the bolt closes on the GO the chamber meets the minimum specification. The GO gauge is then removed and the NO GO gauge is inserted. If the bolt does NOT lock up correctly your HS is within spec. If the bolt does lock up on a NO GO HS is excessive. HS is adjusted by removing the BE and using a lathe moving the barrel shoulder forward exactly 0.0625 inches. The is 1/16 of an inch. BE threads are 16 TPI. Then using a chamber reamer the chamber is reamed until the GO will insert into the chamber with the BE installed and the bolt closed. Stop frequently and check often. A final check is made using the NO GO gauge so you will know that you have not excessively reamed the chamber. It is important to move the barrel shoulder exactly 0.0625 inches so the gas port will be on the top center of the barrel as it should be so the rifle will run correctly. Hope this helps. |
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