Muzzle counterbore?

[centershot]

I have an old warhorse, a Russian M-44 carbine chambered for the 7.62x54R cartridge. The bore slugs 0.314" except for the last 1/2" or so at the muzzle, then it opens to 0.317". It shoots "OK", but I'm thinking it could be better without the muzzle wear. Is it possible to counterbore the muzle to eliminate the oversize portion without dismounting the barrel or other dramatics?

[BLAHUT]

Try a larger diameter softer lead bullet and see if this helps your accuracy ? A couple of my target guns are like this, still shoot accurately. Some just lop off the 1/2 inch and recrown ??

[ascast]

I did this once to a Trapdoor Springfield. The bore looked like new from end to end. I could not hold a four foot group at 100 yds. A cerosafe "chamber cast" of the first 6 inches reveled a grove worn into one land deeper than the cut groove. A friend who was an understanding and competent smith counter bored it about 3-4 inches IIRC. Gun will now shoot about 3 inches at 200 or hold on rams all day with out much fussing around with loads. Made a night and day difference.

[LAGS]

I have had several mil surps that were counter bored or actually did a couple myself.
That is the way you can remove the area of the rifling that is worn at the muzzle from them cleaning the barrel with a steel ramrod.
In also refreshed the Crown , but Recessed inside the bore.
Doing that , I was able to keep the rifle looking original in barrel length , but get it shooting much better.
Now on the rifles that I sporterize.
I just cut off the muzzle area that was worn.
Then re crowned the barrel.
With all of the rifles.
I would slug the whole length of the bore.
Then shoot bullets that matched the bore diameter or with cast Boolits .001" larger diameter.

[Gtek]

Seen several Mosins over the years with counter bored muzzles, I have an SKS that was done by ?. A 44 has a round receiver and might not be that bad on the right lathe, by hand the correct pilot would be a must.

[John Taylor]

Lots of muzzle ware from cleaning rods. That's why many target shooter clean from the chamber end. I get old rifles in often with the last inch of the barrel cut off.

[centershot]

Judging from the replies here this would not be a difficult task for a competent gunsmith, yes?

[Der Gebirgsjager]

Assuming a gunsmith possessing the proper equipment, no, not a big deal. Ideally the rifle should be completely disassembled and the barreled receiver mounted in a lathe. This isn't a job for a portable electric hand drill and bench vise.

DG

[Rapier]

The throating reamer cuts either end of the barrel, most throating reamers, intended to extend a throat, are tapered, but not all. The internal brake throating type reamer recuts a square to the bore crown and removes the lands to the groove diameter. You do need to mount the barrel and the reamer in a lathe.

[john.k]

I bought a military gun that had been 'bevelled' at the muzzle with a drillbit ,well off centre......I think it launched bullets into space .........a 1/2" counterbore back to clean rifling and it shot well........my latest project is a 45 that had the muzzle slightly squashed to ruin accuracy before it was surplussed ........then it was reformed somewhat by heating red hot and driving a punch or drift into the muzzle.......bit of a mess .....however ,a 3/4" counterbore and a bit of press work and the barrel shoots well.

[GregLaROCHE]

What about cutting off the half inch and cutting a new crown. That is if you have the space to do so ahead of the front sight.

[Tokarev]

A cheap counterbore (yes, this is the name of the tool) from an industrial supply store can do the job. All it needs is a pilot of the proper diameter. Then it becomes a DIY job.
An 11/32" counterbore will ring you $30-40 depending on the source. A 5/16" pilot can be turned on a lathe, improvised, or bought for another $10.

[john.k]

The Swedish Mauser rifles had a armourer tool that would recut the crown without the use of a machine shop........if the cutting tool is properly guided ,you can cut a corrct crown or counterbore by hand .........I would think a hardware store 45deg bevel countersink would not be able to do this in a hand drill.

[barrabruce]

Generally, how much oversized would you need to cut the counter bore to work properly without issues of blow by effecting accuracy?

[DougGuy]

As Tokarev mentioned you can get an 11/32" interchangeable pilot counterbore cutter from MSC for $55. They sell a 5/16" pilot that fits in the end of the cutter for another $55 that can be turned to .314" but it won't be a "live" pilot. MSC is usually pretty pricey so some shopping around might save you some $$.

If you have access to a lathe or a good machinist, you can buy an inexpensive chucking reamer and have the first half inch ground to fit into a Manson pilot, flutes sharpened on the new end, order the pilot from Manson for $11 and you are in business. Or you could have it ground to .314" and do the same thing the interchangeable pilot reamer + interchangeable pilot would do, for a LOT cheaper.

Just out of curiosity, in case you don't have access to a lathe or a machinist, I looked up specs for 5.56 x 45 NATO and the dimensions reveal:

Neck diameter 6.43 mm (0.253 in)
Shoulder diameter 9.00 mm (0.354 in)

So it's entirely possible to rent a live pilot 5.56 x 45 chamber reamer and a .314" pilot and use this to counterbore your muzzle. The neck section of the reamer is sufficiently smaller than your bore so it wouldn't damage the lands, It would be tapered somewhat but if you are only reaming 1/2" of the muzzle, would the taper even matter? I don't see where having the crown on the angle the shoulder is on would have a detrimental effect, it would be concentric and easier to clean than a square cut crown.

If you shop around with as many small bore wildcats as have been adopted, you may find a chamber drawing more closer to your desired finished diameters than the 5.56 x 45, then see if you can rent that reamer. I just took a wild guess and typed in 5.56 to see the dimensions.

For comparison, the 11/32" counterbore cutter mics .343"

Food for thought... JS

[indian joe]

Generally, how much oversized would you need to cut the counter bore to work properly without issues of blow by effecting accuracy?

yeah that was my question
I counterbored a 45/70 sharps to get rid of rust marks that were causing leading - (previous owner lived near the coast and the gun had rusted at the muzzle - could barely see the marks when I got it and it shot ok if you cleaned between shots) so I went nearly two inches in seemed to be ok but didnt get all the rust and I finally bit the boolit and sawed four inches off it, recrowned it and recut the front sight dovetail - shoulda done it properly the first time ! was mainly trying to dodge cutting that sight dovetail - not that big of a deal once we decided to do it.
You would think the blowby accuracy thing would have to be a factor - no clue whether more clearance would be better or not - mine seemed not affected by the (bit less than) two inch boring - but the thought bothered me and more would seem to be worse ---however-- there are a lot of blokes with silencers on guns in the US and that is a big long counterbore and dont hear em complaining - ????????

[pworley1]

I have a couple of old 91 Mosins that have muzzles that look like funnels and they still shoot ok for 120 year old rifles that were probably in at least 10 wars.

[Tokarev]

Generally, how much oversized would you need to cut the counter bore to work properly without issues of blow by effecting accuracy?

1/16" on the diameter will suffice.

[barrabruce]

1/16" on the diameter will suffice.
Thanks.