303 brit match chamber

[Killroy]

Does anyone have experience or insight with this chambering? I'm having a replacement barrel made for a Ross Mk3 restoration. There's lots of information about enfield military chambers and the such but not much about custom chambering, for obvious reasons, in this caliber.

I'd like to keep the chamber tight as possible for brass preservation but not so tight that I need custom loading dies. I'm just looking for a reamer recommendation and freebore length to go with if someone knows what has worked for them in the past. My initial thought was to give a dummy round to my gunsmith and request that that this CBTO measurement = a 20 thou jump. Im not a barrel smith, I just know enough to be dangerous and I'm trying to do a lot of the research for him.

 

[Sniperhandle]

I have a lot of experience shooting and reloading this caliber and I have a brand new reamer I will use someday in 303 British that is "CIP" specs and a custom 303 Epps reamer spec'ed out for .308 diameter bullets.

If you are really looking for a tighter chamber, I would assemble a dummy round using Winchester brass, As it is the best of all of the brass I have used, Although it's getting harder to find. PPU may be the second choice only because it seems to be available when you look. Then when you get the dummy round just the way you like it, Send it to JGS or Manson after you have spoken with them regarding what you want.

Because this round headspaces on the rim it will stretch some near the head, Neck sizing is what most guy's do to lengthen case life. Although getting your reamer made to tighter tolerances can mitigate some of the stretch, But the rear locking lugs on the SMLE will always cause some stretch due to the springing of the action upon firing. The 303 was and might still be used for Long Range comps in Britain, Laurie is a Gunsmith across the pond and may chime in and can give you more advice.

The Ross rifle may not have a problem with stretching brass because of the differences in the action and lockup.

Edit to add:
Pacnor makes a good barrel in .311 and X-caliber makes a good barrel in .310, I have chambered a couple of X-Calibers in 7.62x54 based cartridges and had good luck with them.

X-caliber only offers one twist and type of rifling for the .310 barrels but you can get them in a number of contours.

 

[Will Henry]

I have a 303 Match reamer which I got with a .3115 throat with enough freebore to allow the 174 Sierra Matchking to be seated just ahead of the neck/shoulder juncture. With a Shilen barrel on a somewhat modified P14, three consecutive five-shot test groups at 100 yd were under .320". ten shot groups at 300m ran around 1.5 to 2 inches. At one pretty competitive 300 meter match, I came in second over a bunch of 6BR's.
The next year, I bought a bunch of 174's and they were oversized. The previous bullets were .3112, the new ones were .3117, so they stuck in the throat. I ended up grinding the throat off the reamer and cut the throat separately, a .3125 throat in 311 barrels and a 3085 throat in 30 cal barrel.
Bottom line? The match grade reamer is just fine but the throat needs to be .312 diameter at a minimum. The P14 now wears a 30 cal barrel and so does the 303 Epps (Ruger No. One). By the way the match reamer is fine with the three different sets of dies I have. Hornady, Echo, Rcbs. WH

 

[Killroy]

Currently my brass is HXP. Barrel blank is being custom contured by KS Arms out of Alberta CA. It was the only place in North America that had a .303 blank 1.310" diameter and finish out to 31" that wasn't going to be 16 months wait. It should be a shooter

 

[Sniperhandle]

Currently my brass is HXP. Barrel blank is being custom contured by KS Arms out of Alberta CA. It was the only place in North America that had a .303 blank 1.310" diameter and finish out to 31" that wasn't going to be 16 months wait. It should be a shooter

If you send a dummy round in, It should be with new brass. That Greek HXP brass is very good, But I'm assuming it's once fired?