Converting a 9mm Blackhawk cylinder to .357/44 Bain & Davis

[Wiking]

I'm looking to convert my 9mm Ruger Blackhawk cylinder to a .357/44 Bain & Davis. I have the reamer but my problem is that I can't find a gunsmith to do the job. The 2 best in the country don't have time, and the 3rd best refuses to do it, and then there is a few that I don't trust... so my list of possibles grows thin.

I know 2 guys who have a company, one is a very skilled machinest and the other is a gunsmith. I think I managed to pursuade them to do the conversion. But I would like to know a little more about the procedure. It took me a year and a half to find a reamer, and had to pay $400 for it in Germany (no US conpany would sell/rent me one). I talked to another guy (yes I have talked to half the country during the last 12 months) he said that the chambers need to be pre-drilled and that the reamer only polished the chambers to the final fit. From looking at the reamer I just assumed that it is used to drill the cylinders, and not just for the final finishing, as the "steps" on the reamer seem to correspond to the shoulder angles on the Bain & Davis brass.

So basically I'm looking for some info on the actual conversion, so i know a little about what has to be done. This is just my paraniod way of ensuring that my reamer is used correctly. When looking at the cylinder and the reamer, it seems like a walk in the park, but then again i'm not a gunsmith and I do not know to which tolerances the cylinder must be made in order to avoid set back issues.

Any help or advice is greatly appreciated!!

[gunnut69]

I've not heard of this onversion for many years.. The 38/45acp was pretty popular for reliable feeding(read easier to get) of wadcutter level loads in the 1911. Then they just broke down and altered the 1911 for softball loads. The setback issue was never solved in the normal sense. There was a version that used a plastic sleeve around the neck of the case that was ejected with the fired hull. This worked but presented dangers with ammo interchange being especially dangerous. The pre-reaming issue is to spare the finish reamer wear. It is designed to cut the last few thousandths and to leave a very precise chamber..If you hog the bulk of the chamber out with it tolerances can change and the reamer will dull quickly. That can equal poor tolerance controls.. It can be hogged out with a lathe or even drilled out as long as tolerances are maintained so that the hole will clean up and (AND) remain aligned correctly. Any angular or paralell misalignment of the chamber will ruin the cylinder. Also you are aware that the 9mm bore is a bit tighter than the standard 357 is. This will create pressure problems as well as accuracy problems in all likelyhood. If the die set you have will allow smaller diameter bullets a sort of 9mm./44 might be produced but perhaps I'm wrong about the bore diameter.. Will the Blackhawk cylinder allow the chambers to be cut and retain a safe amount of steel to control the pressure levels you expect to produce? A good machinist will know the process for align boring those chambers..a good smith will know weather to attempt to, and a really good smoth has to know his limits... Best of luck with the project...

[Wiking]

Thank you very much for your answer, Gunnut 69.

Many blackhawks have been converted over the years. I tried one a few years ago... nice, packs a decent punch.

As for the bore diameter. I'm not really sure what you mean. The gun is a .357 with an extra cylinder in 9mm (for cheap practice I suspect), there were sold this way. Not many liked the 9mm cylinder as the smaller 9mm bullets were under boresize. I slugged my bore long ago, and seem to remember reading .3575 or 358! I can't imagine the revolver sold with the additional 9mm cylinder has smaller boresize than the original.

I found 2 guys willing to do the job, the find it interesting. One is a machinist and the other is a gunsmith... that sounds like a good combo 

[John Traveler]

What gunnut69 was describing was that the 9mm Blackhawk cylinder often has undersized throats for the .357 magnum. They can be as tight as 0.355", which is too small to properly guide a .357 pilot shank.

What is needed is to first ream out the cylinder throats to proper .357" diameter, and then use step drills to hog out much of the chamber material before using the .357-44 finish reamer. Each of these drilling and reaming operations is done using piloted drills and reamers, with the pilots properly sized to fit the reamed bore. These operations need to be done on a properly aligned vertical milling machine and a cylinder holding fixture. At the minimum, an accurate drill press and cylinder holding fixture can also be used.

The machining is well within the capability of an experienced machinist and gunsmith team. They would be well aware of the hazards of undersized chamber throats and finish reamer wear issues.

[gunnut69]

Thanks JohnT! It sounds better if explained a bit. The conversion would work but There will likely be difficulties with hot loads tieing up the pistol. The article I saw used plastic (delrin?) sleeves to avoid the setback issues.. Looked like a pain to me.. As always there are solutions such as ensuring a clean dry chamber with NO lubricants and perhaps even avioding a high polish?? The problem seems to be with the shulder growing and the case stretching and high pressures locking the case to the rear. The Ruger has a lot of leverage built is the hand but eventually this will cause problems in my opinion. If you do the conversion I'd like some feedback on the weapons operational problems if any.. Thanks and good luck..

[huntducks]

Have you called Bain & Davis.

Last time I was there Red was still around you might get some good info.