Installing and headspacing a new barrel on a bolt action receiver.

First, make a mandrel to hold the stripped receiver in the lathe and mill chucks.  This started out as a 14" piece of cold rolled 1.25" diameter steel rod.  The long section of rod should be turned to just be a slip fit through the receiver bridge.  The short section should be turned to just under the minor thread diameter of the receiver threads.  The lengths of the short and long sections are up to you, but should extend far enough from the receiver that it will turn on the lathe without hanging up in the vise jaws and with enough room to use a cutting tool.  Both ends of the mandrel should be center drilled and tapered for live centers.

 

 

Mount the receiver on the mandrel, chucked it up in the lathe, and trued the face of the receiver.  Take off only the bare minimum of metal needed to true the face.

The finished product.  The receiver will be re-mounted on the mandrel later and set up in a vertical rotary table on the mill so the rear sight ears can be removed while leaving an exact circular shape for the receiver bridge.

 

The new barrel turned on to the receiver and properly indexed (viewed from below).  If there are no index marks follow best practices for torque.  If the face of the barrel shoulder is suspect or damaged, the barrel can be chucked up in the lathe and trued in similar fashion to the receiver face.

 

Checking headspace.  "No go" gauge doesn't allow bolt body to close, which is good, but it looks like we may have a short chamber since the bolt usually closes about ten more degrees on the no go.  Be certain that the bolt body is completely stripped of extractors, internal ejectors, firing pin, etc.  Using a bolt that is not stripped can give false readings that can leave you with a chamber that is much too long.

 

Suspicions confirmed.  The "go" gauge doesn't allow the bolt body to fully close either - short chamber.

 

Finish reamer set up on a t-handle to extend the short chamber about 0.002".  This can be done either horizontally or vertically.  Either way, wrap a paper towel or rag into a “bag” at the muzzle of the barrel and tape it into place.  Dip the entire reamer into cutting oil, squirt cutting oil into the chamber, carefully insert the reamer and take a few light turns, then carefully remove the reamer.  Do not turn it backwards (“backwards” is generally counter clockwise as viewed from the handle) and do not get excited about cutting lots of metal.  Fingertip pressure is about right.  After the reamer is removed, clean it with compressed air and shoot air down the barrel from the camber end to clear chips and old oil.  The “bag” at the muzzle will catch the chips and oil and prevent them from splattering all over your shop.  Now, check the headspace again.

 

Success!  Bolt closes on "go" gauge with just the slightest bit of resistance.  That means a good, tight chamber.  “No go” gauge did not allow the bolt to close.

 

Headspaced bolt and US Model 1917 receiver set up with USGI magazine box and floorplate.

 

Temporarily set up in unfinished stock Next month we will take it all apart and start milling the rear sight base and protective ears from the receiver bridge.  The plan is to slightly re-contour the barrel to remove some dings and provide a "step" between the face of the receiver and the shoulder of the barrel.  Also going to cut the barrel back just enough to add a Shrewd brand muzzle brake while removing the keyway for the front sight and not disturbing the barrel manufacturer engraving.  The exterior of the brake will be tapered to match the barrel contour.  Then we add scope bases and rings, jewel the bolt, rust blue the barrel and receiver, inlet and bed the barreled action into the stock, finish the stock, mount and bore sight the scope, then zero it at the range.

 

Stay tuned!