Reader Forum

Moly-Coated Bullets I read Paul Jewett’s letter in the February 2016 Reader Forum about moly-coated bullets and suspect he may have already ruined his barrel. Given the rapid up and down heat and pressure of firing, peaking at 50,000 PSI or so in some cartridges, molybdenum disulfide releases sulfur and will etch the barrel over time. Once embedded this way, it can not be removed. Before I found this out, it led to me ruining four barrels. What has your experience with moly-coated bullets been?

In reloading, this respondent has never tried moly-coated bullet since there are several non-suspect bullet lubricants readily available. Moly (molybdenum disulfide) was the slicker-upper used in the auto racing oil additive STP.

Small amounts of it in combination with hydraulic fluid makes an excellent lubricant for the slide-to-frame interfaces on target pistols, specifically, a Hamden, Connecticut-made High Standard Victor, an accurized M1911A1, S&W Model 41, and Ruger MK II plus the boltways in a bull-barreled pre-64 Winchester Model 70 .30- 06 target rifle used to win several local bench rest competitions. Remington Model 41 I have a Remington Model 41 in my shop and am unfamiliar with it.

The barrel and receiver appear to be a single unit. How can I adjust the boltway? The Remington Model 41 Targetmaster was only produced for three years in 1936 to 1939. Despite not putting a serial number on most of their firearms until the 1960s, Remington did serialize these. We have been unable to turn up a schematic or a parts list for it even after including a Remington Field Service Manual dated 1942. Perhaps a phone call to Remington requesting a contact with the company museum would be more productive.

We do have questions regarding your assumption the barrel and receiver area single unit. To our knowledge, Remington never designed or produced a bolt action rifle with its barrel and receiver inseparably united. We also have some advice: If you add material to the forward edge of the boltway where it contacts the bolt you may increase the 0.010 gap. Instead, reduce the contact area of the bolt by 0.010. Better Ammunition "Better Ammunition" by Joe Carlos in the April 2016 issue has inspired me S. D.

Shearman Artesia, NM to reexamine my approach to reloading and to try further steps to ensure my brass is as close to perfect as I can make them. Thank you for the great report. Your research emphasizes the importance of launching the bullets exactly in line with the center bore axis, which launched me on a concentricity binge. My goal is to use highly perfected ammunition to evaluate the accuracy of rifles.

I decided to "square up" some resized .308 brass using a Wilson trimmer case holder in my precision toolroom lathe. The Wilson trimmer case holder interior is machined to simulate the chamber of a firearm. With resized brass inserted, I put the case holder in a one-inch collet in the lathe. First, I cut the end of the case neck square, then turned the neck outside diameter using your criteria of cutting only about half the circumference.

I turned the Wilson case holder around so that the case head faces the tail stock instead of the neck and turned the case head square in the same manner. Both ends of the case are square to the bore axis, resulting in the loaded round being as concentric as I can make it. Dean Lake Because potentially increasing headspace is a concern when messing around with rim thickness, I removed only enough material to show a bright area on about half of the circumference, same as with the neck.

I am curious if you have tried squaring the cartridge head to the bore axis, and if you have, what accuracy changes did you note? For my own info, I did a comparison of case head "squareness" on a variety of brass from different manufacturers using a Gem Instrument precision dial indicator in my lathe. I found a variance from 0.0005" to 0.0015" on new brass and a little less on fired brass. I do not know if this is significant and would like your opinion.

Interestingly, I measured some old National Match brass on hand and found them almost perfect. I am not sure if that is from firing or from higher quality brass.

For those not lucky enough to have a lathe on hand, a Wilson case trimmer can be used to square up both ends of brass quite easily by modifying the cutter so the center is no longer "proud" of the cutter blades. This will allow the cutter blades to contact the case head and not be stopped by the center of the cutter. With care, the cutter blades can be modified to clear the primer on loaded rounds if you are brave, but this can be dangerous.

I do not recommend doing that or turning the case neck on alive round either. Ed Renaud Partridge Meadow Firearms, LLC Author Joe Carlos responds. Thanks for reading my article on cartridge concentricity. I always appreciate feedback on my articles and especially so for this one. When I queried the magazine about an ammunition article, I stressed the notion that inferior ammo will any rifle under perform no matter how diligent the gunsmith.

Regarding squaring case heads, I haven’t tried it because I primarily build Stoner rifles and there are several design flaws in the AR-15 regarding accuracy. One of the big ones is the way the upper fits to the lower with only two captive pins, resulting in accuracy robbing movement. Another problem is the way the barrel extension slides into the front of the thin-walled receiver and is held with just a barrel nut.

My March and April 2013 articles ("The Relationship Of Barrel Extension Diameter To Accuracy In The AR-15") discussed ways of correcting this. A third accuracy problem is poor alignment of the bolt face to the center axis of the bore of the barrel. Because we are dealing with a semi-auto gas gun there is a lot of slop in the fit of the bolt carrier. Bolt gunners look at ARs and just shake their heads. The back of the carrier tends to tilt down at an angle and that carries the bolt face at an angle.

It is amazing that the rifle shoots as well as it does. I certainly wasn’t the first person to discover this as Stoner’s contemporaries back in the 1960s recognized the problem. They tried some techniques to correct it that weren’t entirely successful and for nearly a half century since gunsmiths have buried their collective heads in the sand trying to pretend it wasn’t an issue.

I had been devising ways to correct this for a couple of decades before finally coming up with some "baby steps" that resulted in an average group size reduction of about 23%. Thus, I never pursued truing case heads because I feared that any improvements would be masked by the enormous variation in the position of the bolt from shot to shot. Now that I have taken steps to get the bolt face better aligned, I might be interested in testing some casings whose heads have been squared.

Your email reminded me of this topic being addressed in Glen Zediker’s Handloading For Competition. Zediker makes a couple of good points about head squaring. First, he says it will slightly influence the headspace of the cartridge in question. Second, if too much brass is removed from the head, the primer can end up extending above the head. For us gas gunners that could be a problem and might require cutting the primer pocket a little deeper to compensate.

He wasn’t too keen on squaring for cartridges used in gas guns and was more receptive for use in bench rest rifles. You didn’t mention what type of gun you were performing the squaring for. Adjustable Choke I’m looking for an adjustable choke for a single-barrel .410 shotgun. I’d prefer a unit similar to the old Poly-Choke. S. D. Shearman Artesia, NM The "old" Poly-Choke and Poly-Choke II is still available from Nitram, LLC (Poly-Choke.com, but they don’t list units for .410 shotguns.

Mossberg used to have their C-Lect Choke as an option for the 183 bolt action, which was a collet-type choke similar to the Poly-Choke. Technical advisers at Brownells will have more current information. Note, this query doesn’t provide the make or model of the firearm in question. Lacking this makes it less likely we can accurately and safely respond. Please include make and model information in all future Reader Forum questions. AG