Troubleshooting a .308 rifle

I really enjoy the custom Remington 700 .308 Winchester tactical rifle I built in Building a Custom Remington 700 .308 Tactical Rifle. After I wrote that, I did a few more modifications and posted them in How to cut and crown a rifle barrel and install a brake. I affectionately refer to it as my OD .308 (olive drab).

Built on a trued factory Remington 700 short-action and equipped with a McMillan A5 stock, Surgeon bottom metal, Timney 510 trigger, Surefire brake and Shilen #7 select match barrel, it is topped with a Nightforce 5.5-22x56mm scope. This rifle has been a constant companion to the range. It also fills an important role as my backup rifle for just about any important school or match I might attend. While I may have plans on shooting a more exotic cartridge in a more specialized configuration, a 22″ .308 can pretty much do anything (I think of them as the F-150 of the gun world).

Usually it shoots great, but, I would occasionally get an unexpected flyer.

It shoot well with the new brake. 10-rounds at 100 yards from 2 magazine fired off my pack. — 10-rounds at 100 yards from 2 magazines fired off my pack.

Above, a 10-shot group that made me happy. Occasionally, I would get an odd flyer, as shown below.

Note the flyer in the lower left corner.

Most shooters can rattle off the long list of potential rifle accuracy problems: loose mounts, bad optics, bolt handle touching the stock, bad bedding, loose action screws, etc. The list is quite long; and it seems, the more you know, the longer it gets. If your rifle has a forward mounted rail, get ready to add another one.

Inspection of the rifle revealed that the space between the Badger Embedded Front Rail (EFR) night vision mount and the barrel was fairly tight. The Shilen #7 contour barrel has a fairly heavy profile. As a blank (before machining it to fit the rifle) it has a 3″ long 1.250″ shank with a straight taper to .875″ (more information about Shilen contours can be found here). The space between the EFR and barrel was a concern (a minor one) when I originally built the rifle so I had relieved the inside of the EFR to provide greater clearance with some abrasive cloth.

Note how close the barrel is to the mount.

I cut a .005″ thick flexible plastic shim (from a sheet of overhead transparency) and placed it between the barrel and EFR. Depending on how I loaded the bipod, the shim would bind between the barrel and the EFR. It looks like the barrel may have been bumping the mount as it vibrated- this would explain the occasional flyer. Further research supported this theory. A few custom gun builders step their barrels down .025″ to provide ample clearance for the barrel. I decided this was the route I would take. Alternatively, the EFR could be machined, however, it is already epoxied into a stock and there isn’t much extra material on it to remove.

All lathe work is conducted on a Grizzly 4003G lathe with a Bald Eagle spider attached to the faceplate.

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I used the following items from Brownells:

3/8″ High-speed steel turning kit (080-000-835)
High-speed steel 35 degree profile kit (080-000-836)
Starrett Dial indicator (749-007-761)
Viper’s Venom cutting oil (100-013-369)
Lathe file (191-076-980)

After verifying the rifle is safe and empty, I mark the barrel where the EFR ends and remove the barreled action. — After verifying the rifle is safe and empty, I mark the barrel where the EFR ends. Note the shiny surface underneath the mount where is was relieved.

The barrel is mounted between centers. I use an old factory recoil lug to protect the tenon’s shoulder from the lathe’s chuck.

A high-speed steel turning tool is used to straighten the barrel profile where is is covered by the EFR. This provides .025″ of clearance.

I follow the high-spped steel cutter with a lathe file and abrasive cloth. Everything it now blended. — I follow the high-speed steel cutter with a lathe file and abrasive cloth. Everything it now blended.

With the cut blended, I need to focus on the crown. I adjust my steady rest on the muzzle brake’s tenon and secure a .420″ crown tool in a Manson floating reamer holder. I used to run my crown tools at 70 RPM, but have since upped the speed to 360 RPM. I find the finish superior at the higher RPM.

Since I had the lathe's live center in the muzzle, I used a .420" crown tool to cut a new crown. — Since I had the lathe’s live center in the muzzle, I used a .420″ crown tool to cut a new crown.

All parts are degreased and assembled. I take the time to verify the headspace is correct.

A view of relief cut I made on the barrel. I'll wait until after I shoot the rifle to repaint it in olive drab Cerakote. — Not too shabby. A view of the relief cut I made on the barrel. I’ll wait until after I shoot the rifle to repaint it in olive drab Cerakote.

Heading to the firing line, I'm cautiously optimistic things will work out. Since this is a field use rifle, I do my shooting prone, from a bipod, with a rear bag. — On the firing line, I’m cautiously optimistic things will work out. Since this is a field use rifle, I do my shooting prone, from a bipod, with a rear bag.

Success; a nice 5-shot group .411″ at 100 yards (.392 MOA). The rifle seems to be shooting well again. I fired 49 rounds with the new configuration and it looks like my flyer problem is solved.

The rifle shoots well. A fresh coat of Olive Drab Cerakote and it is as good as new.

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