Brand new Mauser barrel break in question

[johnnybar]

After installing a brand new carbon steel, 1:9.45", OEM barrel in a Yugo Mauser, what would be the proper breakin for plain and GC boolits? I'm guessing the originals were broached or cut rifled and will have sharp edges and some roughness that could take way too long to smooth with cast slugs. Would it be advisable to shoot surplus steel, cupro nickle or copper fmjs first? Advice welcome

[waksupi]

Shoot it first, and see how it works. Each barrel is an individual. I had a Douglas barrel that I fire lapped to bring it down to a good group. Another barrel from the old Bauska shop, shot cast wonderfully from the first shot.

[303Guy]

I would fire-lap it. One trick I have tried is to load up cast then smear Auto-Sol liberally over the boolit before chambering and firing. With grease grooves, I would fill the grooves with the stuff before seating. It doesn't matter if it gets into the chamber - all it does is polish the case. These must be fired straight away or the paste will dry and cause terrible leading (I'm not making that up!)

Here is another trick I've tried.

http://i388.photobucket.com/albums/oo327/303Guy/Fire-LappingPigGun014.jpghttp://i388.photobucket.com/albums/oo327/303Guy/Fire-LappingPigGun015.jpghttp://i388.photobucket.com/albums/oo327/303Guy/Fire-LappingPigGun017-1.jpg

That would be a half case or less of W438, then corn grits up into the neck topped with a card wad, then some grinding paste. A cast or paper patched boolit goes on to and that's it. The corn grits forms a plug with the abrasive being forced against the bore behind the boolit. That is for deburring the bore before the polishing trick.

[Dollar Bill]

Unless you have a lapped barrel, which you do not, I always break in barrels by shooting the heaviest jacketed bullet available (or the one with the most bearing surface, like a round nose) using the slowest powder at minimum loads. 5 rounds is all you need. After the first round, while the barrel is still warm, clean with Sweet's 7.62 or copper solvent of choice, run patches till bore dry. When bore is cool (ambient temp), shoot another round and repeat cleaning and cooling. After the third round, you will note a markedly smoother bore while cleaning. Spend an hour breaking in a new barrel properly will result in a life time of good shooting.