Preparing A .375 Ruger Alaskan for Africa (2): An Unexpected Technical Setback

Updated: Aug 23, 2020

The owner has not posted lately as an issue has become evident with the rifle: the bore for about 4-5 inches from the muzzle is very rough - to the extent that the lands have grabbed a great deal of copper which due to the still burning propellant all the way to outside the muzzle has been brazed onto the bore metal. Worse however is that there appear to be hairline cracks in the chamber of the stainless steel barreled rifle. Linear scratches caused by previously used gritty, dirty cases are also evident.

He sent me some photos and video taken with his nifty bore camera:

The non-linear appearance of the mark suggests a micro crack following the micro structure of the somewhat brittle stainless barrel steel.

Only a dye penetrant test will confirm whether the "cracks" are real or not.

Very rough bore the last 4-6 inches from the muzzle grabs and retains copper from bullets and which no amount of scrubbing can remove. This is a sign of copper brazing taking place as often suffered by short barreled rifles. Still burning propellant out the muzzle causes surface corrosion as many shooters try to increase muzzle velocity with hot loads of slow burning powders.

Other surface blemishes in the chamber

To be sure, until a proper dye penetrant test had been done and examination with a focused borescope the possible micro cracks are just a first order observation.

Marks and possible cracks and blemishes in the chamber

Copper deposits embedded near the muzzle are due to the bore being roughened by still burning propellant heating the surface tremendously. This is exacerbated by the expulsion of the still burning propellant and hot gas which causes a rapid suckback of oxygenated air into the muzzle and over the super-heated bore surfaces - creating burn corrosion and surface stressing. The metallurgical action is similar to an over lean fuel-air mixture in a turbocharged engine causing damage to the exhaust valves.

The owner of course is disappointed with the inside condition of his new pride and joy and contacted the seller as well as Ruger, and also a few independent barrel manufacturers for a quote on a new barrel should replacement be necessary. Ruger had the strange response that they would not - even if the owner paid for it - install any other type barrel than an original 20" stainless steel. The owner requested that they installed the 23" carbon steel barrel as used in the "African" model - but Ruger refuses to do that without explaining why. For somebody outside the culture of American firearms manufacturer that approach is very alien.

The option for another non-Ruger barrel exists - but only one supplier is prepared to remove a barrel from any Ruger rifle and install a new one, apparently due to the receiver being cast and not forged.

The rifle will be taken to Ruger for examination and confirmation of the integrity status or not of the chamber.

Other chamber and bore views, including massive copper fouling and possible micro cracking.

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