Ri­fle bar­rels un­cov­ered

The world of ri­fles can be a tech­ni­cal mine­field, and gun­smiths like Jonny re­ceive end­less ques­tions from con­fused cus­tomers. Here, he be­gins a se­ries on the ba­sics of ri­fle buy­ing

Sporting Shooter - - Gunsmithing -

We get asked a lot of ques­tions about ri­fles on a daily ba­sis. This month, I will dab­ble in this po­ten­tial mine­field, cov­er­ing a few of the main topics – but please re­mem­ber that this is an in­tro­duc­tion, so the phrase ‘gen­er­ally speak­ing’ could be in­serted a lot more than it has been.

Many peo­ple be­lieve that there is a lot more to worry about tech­ni­cally when buy­ing a ri­fle than there is when buy­ing a shot­gun, from cal­i­bre and twist rate to bed­ding and bar­rel life. How­ever, my feel­ing is that if the ul­ti­mate ques­tions are ‘does it han­dle and fit well?’ for a shot­gun, the ul­ti­mate ques­tions with a ri­fle are sim­ply ‘is it ac­cu­rate and is it easy to shoot?’ So re­ally, in essence, buy­ing shotguns and ri­fles are equally sim­ple!

Bar­rel life

The first thing I should say with this is that a bar­rel’s life de­pends on a vast ar­ray of fac­tors. The main one is the de­gree of ac­cu­racy the shooter re­quires and the abil­ity of the shooter to har­ness that ac­cu­racy. A long-range tar­get shooter of any abil­ity will have stricter tol­er­ances and a lower round count bar­rel life than the av­er­age UK stalker who only re­quires 2-3 MOA.

If wor­ried about bar­rel life, it is im­por­tant to es­tab­lish a base­line on how truly ac­cu­rate a ri­fle is when you first ac­quire it. To do this prop­erly, you must be ca­pa­ble of touch­ing bul­lets con­sis­tently and have found a load that will make the ri­fle as ac­cu­rate as pos­si­ble. From here, you can mea­sure how large your groups get.

Ob­vi­ously, the bar­rel life will start tick­ing away from the first box of ammo; the speed at which that hap­pens will de­pend on which loads you put through it, what cal­i­bre it is, and how well you look af­ter it. As such, there are no hard and fast rules on bar­rel life, al­though it should be stated that more pow­der equals less bar­rel life. So, when packing your cases on the load­ing bench to achieve an ex­tra 100fps, per­haps don’t!

Case stud­ies

Time for some real life ex­am­ples:

Per­son A Howa .243 Stain­less Sporter Ca­pa­ble of ½ MOA out of the box, 1,500 rounds saw this ri­fle do­ing 1 MOA groups. By 2,200 rounds, this ri­fle had stretched to just over that, and was sold on (head shoot­ing was a nec­ces­sity for this gun). This ri­fle was shot with fac­tory Norma 100gr only, and only cleaned oc­ca­sion­ally, and used for a fairly hard stalk­ing life.

Just a quick aside – the ri­fle cost £500 new at the time and Norma cost £32/box or £3,520 for all 2,200 fired dur­ing its life. Not bad when you con­sider the ac­tual pro­duc­tion cost of a Howa bar­rel can’t be much more than £50!

Per­son B Howa .308 Varmint Blued Ca­pa­ble of sub-MOA con­sis­tency out of the box. This ri­fle fired 9,000 rounds of mixed fac­tory, home­load and cheap FMJ through­out its 10-year life, and with reg­u­lar cleaning only stretched out to 1¾ MOA, but still was gen­er­ally within this.

Per­son C Cus­tom 6.5x284 Used for long-range tar­get com­pe­ti­tion for the first 700 rounds when the ri­fle was ca­pa­ble of sin­gle holes at 100m, then used less so un­til a round count of 1,000 when ex­ces­sive throat burn meant the ri­fle lost mean­ing­ful com­pet­i­tive ac­cu­racy.

Per­son D An old Sako Forester.243 This ri­fle has been owned by D for around 30 years but was sec­ond-hand then. Ob­vi­ously, there were rounds fired be­fore, but ac­count­ing just for D’s us­age this stands at an es­ti­mated 12,000 rounds plus! This ri­fle shoots 2½" at 100m on a good day, but this is inside the owner’s

‘Af­ter shoot­ing, al­ways take your moder­a­tor off and wipe your crown and muz­zle’

ex­pec­ta­tions (be­fore any­one judges, the DSC re­quires 4" and plenty of peo­ple just scrape this.)

What can we take away from this? Well, noth­ing con­crete, cer­tainly! As a gen­eral rule of thumb, a long-range over­bore ca­pac­ity ‘hot’ round with high ac­cu­racy re­quire­ments will do around 1,500 min­i­mum, and af­ter that it is down to load and care, with prob­a­bly 2,500 for re­tained fac­tory ac­cu­racy and 6,000+ is well achiev­able with ad­e­quate ac­cu­racy.

I once asked an old-school long-range tar­get shooter how long it would take to wear out a bar­rel, and he gave me the clever an­swer of “about 3-5 sec­onds”. This is how long it takes 4,000 rounds to leave the bar­rel upon fir­ing. You can use this anec­dote if you like, but be­ware that peo­ple might think you are a bit of a mup­pet!

A fi­nal, but po­ten­tially less ac­cu­rate ac­count from a third-hand source, states an old .220 Swift that had been, al­most since the cal­i­bre’s in­cep­tion, used with “killing ac­cu­racy” for 20,000 rounds. It is ro­man­tic tale, which is nice, al­though the source I got the story from should give it cre­dence, so I couldn’t dis­re­gard it en­tirely.

Loss of ac­cu­racy

See­ing as this is rapidly turn­ing into a multi-faceted ar­ti­cle, I shall go down the rab­bit hole a bit more and talk about what hap­pens to make the ri­fle lose ac­cu­racy.

Throat burn is one of the big­gest fac­tors in de­grad­ing ac­cu­racy. The throat is the ta­pered part of the lands (the ridges of metal be­tween the grooves of a ri­fle’s bore). In sim­ple terms, it is the bit of the bar­rel just af­ter the cham­ber.

As the throat wears down, the lands also wear away from the cham­ber. When reload­ing, you will no­tice that as a bar­rel’s life goes, you will have to ‘chase the lands’ mov­ing your seat­ing depth out bit by bit on your reloads. An OAL gauge can be a use­ful mea­sur­ing tool for throat wear. As well as the throat ex­tend­ing out, there is also a cor­ro­sion as­pect that hap­pens in the first 3-4" of the ri­fling. This takes the form of tiny cracks and pits, and it is this rough­ness that ob­vi­ously will de­crease con­sis­tency as it dam­ages the bul­let’s jacket on its way past. This ero­sion is caused by heat and ox­i­di­s­a­tion, as well as the ac­tual move­ment of the bul­let and other par­ti­cles past it at high speed. Throat ero­sion will kill ac­cu­racy well be­fore ac­tual ri­fling wear makes any dif­fer­ence to ac­cu­racy, al­though long-term it is pos­si­ble to round off and smooth out the ri­fling suf­fi­ciently to fin­ish a bar­rel off. It is more than likely that the bar­rel would have to be short­ened from the cham­ber end, cut­ting off the eroded end, then be recham­bered and re­fit­ted to the ac­tion to truly wear the ri­fling out. Af­ter throat ero­sion, muz­zle ero­sion is the next wear con­sid­er­a­tion. This can take many forms, but the most com­mon cause of muz­zle ero­sion is lack of proper care and main­te­nance. The main blame goes to mod­er­a­tors – they do catch those gases beau­ti­fully in a way to re­duce noise, but they also re­tain the rather cor­ro­sive stuff right around the end of your bar­rel. If the mod isn’t re­moved af­ter shoot­ing, the gases will sit and eat into your muz­zle where they are con­tained (let alone eat the moder­a­tor and bar­rel in gen­eral, not that I can com­ment on cleaning of per­sonal sport­ing ri­fles). Af­ter shoot­ing, take your moder­a­tor off and wipe your crown and muz­zle as a very bare min­i­mum. But here’s the bad bit – even if you do clean your ri­fle, you have to do it prop­erly or you could risk dam­ag­ing the crown. A lit­tle bit damned if you do, damned if you don’t, I know. By ‘prop­erly’, I mean avoid­ing: go­ing in dry with your phos­phor bronze; yank­ing the phos­phor bronze back into the bore; and us­ing a scrub­bing mo­tion inside the bore (not so much crown­re­lated but just a no no).

Ev­ery­one will tell you dif­fer­ent ways to clean a ri­fle, but as long as you avoid these things, and keep it wet with cleaning fluid from start to fin­ish, and leave it very dry, you won’t go too far wrong.

Stain­less vs car­bon steel for bar­rels

Ev­ery shooter has their own idea of what a good look­ing ri­fle is, so is there any dif­fer­ence? Yes, there is. Be­fore say­ing any­thing fur­ther, it should be known that ‘stain­less’ doesn’t mean ‘100% guar­an­teed not to cor­rode’, and will likely pit and rot in the same way when abused.

As steel is an al­loy, it is also worth say­ing that stain­less bar­rels and car­bon bar­rels from dif­fer­ent man­u­fac­tur­ers will have dif­fer­ent in­gre­di­ents and most bar­rel steel recipes mix their in­gre­di­ents to lean to­wards strength over any­thing else. Gen­er­ally, the two bar­rels are made from two dif­fer­ent types of steel en­tirely and will there­fore have dif­fer­ent met­al­lur­gic prop­er­ties. The vast ma­jor­ity of match-grade bar­rels on the mar­ket are made from stain­less; the rea­son for this is that stain­less is marginally softer, which lends it­self to a slightly bet­ter in­ter­nal fin­ish – or an abil­ity to fin­ish it bet­ter more eas­ily. Car­bon bar­rels can be just as ac­cu­rate, but it is some­what harder to get them to the same fin­ish qual­ity. The fin­ish on raw stain­less ob­vi­ously can’t wear off, whereas blue­ing can, but luck­ily Cer­akote has solved this mak­ing the fin­ish hard as nails.

At the end of the day, I would say bar­rel qual­ity is more im­por­tant. A badly made bar­rel made from any steel won’t shoot as well as a well-made bar­rel from ei­ther, as it’s sim­ple as that.

Hunters might be happy with 2-3 MOA ac­cu­racy while tar­get shoot­ers will be far more de­mand­ing

A typ­i­cal .308 will re­tain ac­cept­able ac­cu­racy for many thou­sands of rounds

You need to take par­tic­u­lar care of the crown of your ri­fle bar­rel to main­tain ac­cu­racy.

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