Will a MK19 50AE bolt lock into a MK19 .357 Mag Barrel?

[TonyRumore]

Will a 50AE bolt run in a .357 barrel........you know, for rechambering a .357 barrel to 357-50AE.

Tony Rumore
Tromix

[MrBlackCat]

Kind of...
I will try to explain my tested and untested points of view on this... The bolt will pass through the bolt face of a 357 and appears to potentially lock up in a 357 IF it weren't for the rim catch of the 357... I think. (sorry if that is vague)

I am doing a caliber change from a 357 magnum barrel to 10mm Auto is why I even looked into different option of things to do with these guns. I don't reload ammunition, so wildcats like the failed 440 have been of no interest really. Then the 429 comes out. Excellent.

Anyway, because you would be changing from a barrel chamber designed to catch a rim (.357) to a shoulder head-spaced pistol cartridge, the rim stop would be machined away anyway, so the bolt would probably work fine but I have not done this to test.

Two very different ways this could be done...
A, you could re-chamber to some custom made 357DE Magnum you develop just by having a reamer built to match some brass you make or have made. This would eliminate the rim catch area in the barrel for the most part, or it could be machined to the appropriate depth.

B, you could just bore and sleeve a 50AE Barrel with a 357 magnum sleeve.

I was planning to bore/ream to size a 357 barrel to 40 caliber (10mm) and then rifle and chamber it. I had a reamer fail and damage the barrel beyond what I can repair however. So I found it necessary to switch to plan B, the sleeve method. I bought a Glock 10mm Auto barrel to turn down into a raw sleeve and then I have a chamber already built as well.

It can probably be done... but is probably less practical than the 429/440.

Lots of things to consider, but to answer your question, it is very likely the 44/429/440/50 bolt can be used in a 357 lug barrel with minor modifications, although I have never had a reason to try it. a 44 bolt does pass through, as the lug pattern is almost identical and the radius to outside of lugs is within a few thousandths of the 357 lug pattern. The extractor is different, but just a bit narrower.

That is all I can think of on the subject... so is this something you are seriously considering, or just an idea you were entertaining?

MrBlackCat

[GarrettJ]

My .44/.50 bolt will not physically fit into my .357 barrel extension. It looks close, so it may just be tolerances between the two. The major diameter appear to be the same on both. It looks to be hitting at the minor diameter, on the area of the barrel extension between the 3:00 and 6:00 locking lugs, when viewing the barrel from the chamber end. It looks like I should be able to grind a small amount of material off the barrel extension between those two lug openings to get it to fit.

All of my MK-XIX barrels are the older 2-piece type. Not sure if that makes a difference.

The .44/.50 bolt will fit in the L5 .357 barrel, but will not rotate into the locked position. But there are other dimensional differences between the L5 adn MK-XIX .357 bolts.