If I’m planning to turn down a .809″ barrel for 3/4″ threads instead of 5/8″ – Do you think I’ll need to install something like this collar? Thanks for your advice.

Later, Frank

Even just cutting and crowning the muzzle if you hit a residual stress point the bore can open up. This is also a reason I would never flute a button rifled barrel as well. Residual stress. No barrel maker can measure for it and it’s more prominent or problematic in a button rifled barrel.

Later, Frank
Bartlein Barrels

The conventional wisdom is that button barrel bores expand when you contour them, hammer forged bores actually shrink, and cut rifled stay the same.

Removing the flash hider resulted in bullets printing an inch low at 100 yds. Replacing the hider brought them back on target.

I never could figure out why until I saw this video.

Let’s go WAY back to Lee Enfield barrels.

They were NOT buttoned or gang-broached, but cut with MANY passes of a traditional single-tooth cutter.

But it gets more interesting. The basic “blank” was a “forging” that started out as a bar of steel not much bigger than final diameter. The breech end was formed on this billet by heating and “upsetting”. (No, not being rude to it), but by heating it up in a forge and literally hammering /dropping it on that end to make it bulge out to form the bulk needed at the breech reinforce. This probably also had the useful side effect of “rearranging” the crystal / grain structure in this area to provide better resistance to the radial shock of firing.

Once the bar was roughly formed it was checked for straightness, adjusted, stress relieved etc, before being drilled and reamed.

I have several MINT barrels for the No1 (SMLE) rifle here and they ALL show some “belling” of the lands at the muzzle. I strongly suspect that this is a result of the final lapping.

Having said that, VERY early SMLE barrels sere TAPER lapped. Why? they were attempting to approach the velocities of the earlier “long” Lee Enfield barrels by reducing the height of the lands as they approached the muzzle. (This with the 220gn, hard nicked-jacketed Mk6 bullet as well!

The peculiar thing about Lee Enfield barrels, apart from the 5-groove, left-hand twist, is the dimensions of the rifling. The “bore” size was very tightly specified at: 0.301″Min / 0.304″Max. HOWEVER, groove depth runs from 0.005″ to 0.008″. Thus you could end up with a maximum “acceptable” groove diameter of 0.320″! This with a 0.311″ diameter bullet.

The past is a very foreign country, indeed.

So, the British .303 cartridge was essentially that very “modern” thing, a “bore-rider”.

The advent of the “high-velocity” Mk7 spitzer bullet threw all of the previous practices out the window and from about 1913 onwards, all barrels were parallel bored and rifled. The only problem was the muzzle belling resulting from over-zealous final lapping that continued to the very end of production.