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BTW - what is ball-burnishing? Is it pulling a 'button' through the bore to iron the lands - or something similar?

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Thought I had something in the Tilley Files

Page 76 of The Parker Hale Gun Catalogue No 67 details Ball Burnishing as:
'The Ball Burnishing process consists of forcing very finely graded hard steel balls through barrels that have been selected from target quality production for all aspects of their internal condition.

The ball is first selected to match the initial bore size or gauge of the individual barrel; it is continuously passed through the bore and in succession balls of slightly greater size are used to level out any internal imperfections, thereby imparting to the lands a homogeneous work hardened surface which assists accuracy through improved parallelism whilst effectively increasing the resistance of the lands

Ball Burnishing enlarges the average bore by approximately one half thousandth of an inch, an almost infinitesimal amount which in no circumstances can cause detrimental effect.

New barrels are officially acceptable today when made between .301" and .304" gauge, but 98% of new barrel production is found to gauge between .301" and .3025".

After Ball Burnishing, these sizes may be increased to a maximum .30275" gauge.

Barrels when sectioned show that Ball Burnished samples have a dark mirror-like surface of the lands, whereas others not burnished although well-rifled disclose innumerable cross-cuts.
Even the finest boring leaves a series of tiny cross-cuts which tend to tear the metal from the bullet envelope during its passage up the barrel.
Not only does it improve the surface as stated above, but it is to be recommended mainly on new barrels to improve their initial levelness, to extend their normal life and to minimise the collection of metallic fouling.

It is not recommended for barrels that have been so worn as to round off the corners of the lands, for this reduces the area of contact to the ball in the burnishing process.

Nevertheless, a barrel that is not too badly worn can often have its accuracy improved by Ball Burnishing.

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What was your slow fire group like?

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This picture shows quite graphically, why I keep spouting off about making your brass fit the chamber if you want your brass to last.



Note the case on the left - it has the longest neck length. This means the body of that case is the shortest of the three and if that case is shot in a longer chamber, the body will blow forward stretching the case - usually at the web - causing premature case loss in a loading or two, ending in case head separations at the web - unfortunately normal for the .303 due ot sloppy chambers and failure to fit brass prior to it's being fired the first time.

The case in the middle has a slightly shorter neck than the left case, and appears in the middle of the two outside cases for neck and body length. Note the different shoulder of the far right case - having a slightly shorter neck and the shortest body length as well, due to it's sloping shoulder angle.

Brithunter - as you noted - the chamber walls are not sloppy like many military chambers show. They fit the ctg. base nicely and should promote longer than normal case life.

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Whoops must have been asleep to miss this post The funny thing is I only keep cases segregated for the Belgian Martini the others all use HXP 69 Brass with a few Winchesters sometimes. Despite loading for several different 303's and normally full length sizing I had yet to have a case separation on a hand load. Had a few partial ones with some milsurp ammo. My dies a a set of RCBS reload Special dies in the plastic clam shell packaging so nothing special really.

Only have five 303 chambered rifles now not including the Century Arms P-14 Centurion that I had re-chambered for .303 Imp having sold the Martini AC11 to make room for another sporting rifle for the collection in 2009. The BSA sporter retailed by Wm Powell had a new 39 dated surplus barrel fitted just before I acquired it yet despite being a surplus barrel it too has a nice chamber. I just must be very lucky on this score.

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Don't let the bastards grind you down!

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I don't think I'd get that fancy with cross sticks. I rest the back of my hand on the crossed sticks. That way, it shoots identically to the way I sighted it in, which is identical to it's poi when shot offhand.

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