Help me improve the accuracy of my Remington 798

[BornFighting88]

The Mauser threads are not metric in pitch. They use the old British Whitworth thread, as mentioned by Clemson, so it has a 55° thread profile instead of the 60° profile used most of the time these days. When I was messing with Mausers, I bought a special 55° profile threading tool from Brownell for the barrels. I later concluded I could have worked around it as the lathe's toolpost can be set to angle a 60° threading tool 5° tailward and the top slide under it may be set to the 55° angle, then the 55° threads produced by turning the cross slide in a little at each threading pass until the depth of cut is adequate. You don't get the ideal radiused peaks and valleys of the Whitworth profile without modifying the tip of the threading tool, but you do get something that fits, and it is something any gunsmith with a lathe should be able to do.

Other than that, if you buy your barrel from Douglas, McGowan, Hart, Shaw, they offer rebarreling services to include installation. I'm sure some other brands do as well.

Last I remembered, Mauser 98’s used 1.100”x10 TPI, and a standard 60 degree tool will cut them just fine. I think the compound adjustment at the 60 degrees is 0.087” (.866/TPI, hence .866/10 = 0.0866”). I have found when single point cutting threads, it is best to start by making your last pass about .005-0.010” shy of your calculated depth. Only cutting a max of 0.001” per pass until you have seated your threads to a satisfactory fit.

I digress. Usually glass bed, free floated barrel, and properly torqued action screws go a LONG way to starting you on your accuracy journey.

 

[HiBC]

Just to list a back up reference source, I searched "98 Mauser Barrel Shank Thread data"

One of the sources that came up was a "Practical Machinist Forum". They had a thread on the subject.

It verifies 55 Deg Whitworth thread form, 12 threads per inch, 1.100 major

You may do your own search,or look here:

https://www.practicalmachinist.com/vb/gunsmithing/mauser-barrel-specs-175198/

Note one post confirms truing the receiver face face using a mandrel.

Consider most (if not all) Mauser Military barrels did not have a shoulder that seated against the forward surface of the receiver ring. The largest diameter of the barrel was the major diameter of the threads.

The extreme end of the barrel,at the level of the chamber mouth,stopped against the diaphram within the receiver ring.

At least on a Military 98,nothing rested on the forward surface of the receiver ring. I have no idea what the original machining strategy was for the 98 Mauser, but they had no real good reason to make the face of the receiver a precision surface.

The common way of fitting barrels to Mausers today,the forward face of the receiver ring is THE foundation surface the barrel extends from.

Since the scope (line of sight) is attached to the receiver,and the axis of the bore is the barrel, how the barrel seats to that foundation is CRITICAL to accuracy. We want it square,straight,and solid.

Anything that amounts to a high spot or out of square condition introduces play,or a "cracked baseball bat" into that joint.

I might be wrong, but IMO, some "bedding solutions" such as a pressure point,worked because they provided a preload to push the barrel to take the rattle out of the barrel receiver joint. A rattling free float barrel won't work so well.
But flat,square fitup of precision surfaces will likely make full free float the most consistently accurate bedding method.

Other folks ,I'm sure may disagree, but when I tighten guard screws,I want the flat bottom of the receiver to be the one and only surface (think horizontal datum plane "A") the screw is loading. The floor. On a Mauser,depending on the bedding strategy,it might be the guard screw bosses, or the sides of the receiver rails that provide a vertical datum plane "B" to align the receiver . The fence. And the recoil lug,Datum "C", or the "Stop".
Just like a machine setup.

I DO NOT want two surfaces arguing over which is in control. Like tang versus recoil lug. Or sides of guard screws contacting the stock.

And I DO NOT want torquing up the guard screws to put a side load on the breech end of the barrel!! You do as you wish.

 

[Scorch]

Mausers are a little bit different to bed than a lot of rifles. Flat bottom keeps them from torquing when fired. The rear of the recoil lug, the flat bottom of the front receiver area, the rear pad, and slight shoulder areas at the front ring and rear tang are the only places that should contact the stock. If the rear of the tang touches the stock it will split it eventually.

Do the barrel any way you want, free-floated or bedded, but put a shoulder on the barrel that contacts the front of the receiver ring. Original Mausers were barreled that way, the barrel had a shoulder that seated against the front of the receiver and the breech seated against the internal gas ring. We used to go to a lot of trouble to make sure both the receiver ring and the internal gas ring made contact when the barrel was seated, but I have seen a lot of them that were not done that way that shot just fine as long as the threads were tight.

And yes, Mauser threads are 12 tpi, both on small rings and large ring Mausers.