Rifling Pics for Noobs

[Bruce_in_Oz]

That bit about "eccentric" chambers is more than a bit off.

I suspect that this condition was assumed after examining fired cases with odd bulges near the head.

I have several drawings of "official" .303 chambers. I loaded the data into AutoCad on individual layers and then added the SAAMI data. No huge differences, just a few minor differences at the shoulder/ neck / throat area. (BTW, if anyone has chamber / barrel drawings for Bren, Lewis and Vickers barrels, I would like to expand the exercise. In my experience, machine gun barrel chambers are generally different from rifle chambers for the same cartridge.

What I suspect is that there were tooling variations, especially during wartime. Given the cost in time and labour to produce reamers, especially Pre-CNC, it would not be unreasonable for new reamers to be made a bit oversized.

This would allow the reamer to be resharpened a few more times before being scrapped as unusable.

Couple that with the common occurrence of "undersized" brass and some fired casings look seriously ugly.

Given also that military users are not known for reloading brass scavenged from the two-way rifle range. nobody really got too bent out of shape over the issue. Added extra reason for letting brass lie, would be the corruption of most (Commonwealth) .303 brass by mercury in the primer.

What still intrigues me is the horrendous tolerance on the groove diameter in .303 barrels. I think it is a hangover from the days of the Minie ball and P-53 Enfields. Yes, bullets (open based military ones, anyway) DO expand when booted up the backside by 45,000PSI or so. However, one cannot guarantee that said expansion will be absolutely concentric. Maybe the idea was that as the lands impressed into the bullet jacket, the displaced metal would flow outwards to fill the barrel grooves. That is vaguely possible, but see concentricity caveat above.

However, in the bad old days of cupro-nickel jackets, black powder and Metford rifling, complete bore obturation was very unlikely. Adding Cordite, which burns at a very high temperature, to the situation only made things worse by cheerfully eroding out the throat as the gases ate their way around the base of the bullet.

So, They changed from a perfectly functional form of rifling to a cruder system that worked with the ammo that was available. (Bullets are cheaper than barrels!) Note that the Type 38 Arisaka 6.5mm used Metford style rifling, (Your Arisaka barrel may not be "shot out";l it just looks that way)

[jmoore]

If I ever quit working overtime, I'll see what I can round up. I also have a Hawkeye bore scope, but haven't figured out how to adapt a camera to it yet.

Catagories that might be interesting:

New leade and crown
"burned out" leade
cord worn chamber, leade and/or muzzle
corroded bore
fouled bore
cupro-nickel fouled bore (might be hard to find- but it DOES look different and scary- I cleaned one out a while back...)
tight spots (the only one of those I have is a Winchester custom shop M70LH Ultimate Classic stainless in 25-06.)
bulge
bent barrel as seen through the bore- it'll be a tough camera shot, most probably! I used to have a couple...

Any other ideas? Maybe I can sort the bore scope fairly soon- Please be patient!

[CelticCollector]

Those sound like good pic ideas. I hope this somehow helps people like me, especially when looking at possible new aquisitions.

[bigduke6]

A bad case of corrosion, tried with a 1/4 " cutter as Peter suggested but didnt allow enough light for a pic so opened it up. will get the rest of this done and others at some point and post.

[Peter Laidler]

Brilliant................. One pic really dos describe a thousand words! What would be very interesting to see now would be a Mk2 barrel where the reinforce is shrunk on to the barrel and pinned. Got one of those handy BigDuke?

This opens up a very interesting question now........... (sorry about this.....) What would be the legal status of a 'barrel' cut/machined like this. If I had to give an expert opinion I'd have to say that it's nothing but asctioned length of barrel not capable of ever doing or being anything else, ever, in the future.

Great work Big Boy.....

[bigduke6]

Brilliant................. One pic really dos describe a thousand words! What would be very interesting to see now would be a Mk2 barrel where the reinforce is shrunk on to the barrel and pinned. Got one of those handy BigDuke?

This opens up a very interesting question now........... (sorry about this.....) What would be the legal status of a 'barrel' cut/machined like this. If I had to give an expert opinion I'd have to say that it's nothing but asctioned length of barrel not capable of ever doing or being anything else, ever, in the future.

Great work Big Boy.....

Think its a catch 22, regarding the status, if the chamber was cut in a way were it cannot support a round and a lot more of the barrel is sectioned (both sides etc) and the thread removed then cannot see it being a problem.

Again if it was just the rifled part and no chamber (barrel blank) then no licence required.

The other reason for the way i cut the chamber is i have the old brass for this barrel and can use these along with new brass to show the variation.

Can you shed some light on the Mk2 Barrel I gather we are talking about the Bren ?

[Peter Laidler]

Mk2 Barrels................ As a matter of interest, Mk2 rifle barrels were fabricated by ACCLES AND POLLOCK in the UK and made from a hammered length of barrel but the reinforced breech end was heat shrunk OVER the barrel and pinned on. Apparently they worked loose and these barrels were declared obsolescent in the mid 50's and culled or just re-barrelled. They seemed to shoot OK so I have been told but the bore was never shiny. As a result, a squaddy with one was always in the .......... er........, mire so to speak. Eventually an instruction was issued that supervisory staff should be aware of this.

I saw a couple of pinned barrels but never got a chance to section one - nor I suspect has anyone else. Nor are they known about.

I'll look up the technical info about them re the location of the pins etc and come back to you but GREAT work on the milling machine

[bigduke6]

"You learn something new every day", look foreward to the tech info regarding them, only thing i have seen similar is a .22 conversion which used approx the first 6" of the original barrel which had been bored to take the .22 barrel an easier option than boring the full length to take a liner, was an excellent job.