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Axkiker
08-10-2015, 01:53 PM
Im about to undertake a project where a guy will need a gun part made from stainless. He has requested 303 but really doesnt know anything about the different alloys.

From an alloy perspective what do you all recommend? Is 303 really okay? Seems like I have read most want in the 400 range to be considered a quality stainless. Machining wise ive heard horror stories about work hardening etc. This project will require a combo of milling and drilling.

Any advice.

Thanks

Toolguy
08-10-2015, 02:09 PM
The 300 series is pretty soft, but can be a bear to machine. The 303 is very easy to machine. Most gun stainless steels are 410 or 416. It depends on what part this is and what it does as to which alloy would be most appropriate. The 300s are more rust resistant than the 400s.

doctordoctor
08-10-2015, 02:12 PM
Toolguy is right on. Stainless alloys arent quality or not based on their composition specs. They all have different purposes and strengths and weaknesses. If you are trying to put as little effort as possible into the metal selection, then copy whatever alloy is currently proven to work in this application.

Axkiker
08-10-2015, 02:18 PM
he says this is a custom gas block... I know very little about guns so feel free to educate me. Based on the drawing this is a very easy part to make

wierdscience
08-10-2015, 02:18 PM
+1 for application specific alloys,especially when strength may be a greater issue than corrosion resistance.

If it's a gas block for an AR then almost any stainless will work,since many of those gas blocks are Aluminum.In that case 303 should work fine.

Axkiker
08-10-2015, 02:37 PM
+1 for application specific alloys,especially when strength may be a greater issue than corrosion resistance.

If it's a gas block for an AR then almost any stainless will work,since many of those gas blocks are Aluminum.In that case 303 should work fine.

Its an AK but I would assume 303 still should work based on whats been stated.

wierdscience
08-10-2015, 03:08 PM
Its an AK but I would assume 303 still should work based on whats been stated.

That might be a good question,I know AK gas blocks are made from steel,but what steel exactly I don't know.

Brian H.
08-10-2015, 10:54 PM
From someone who has modified his AK fairly extensively (though not the gas block, yet): don't overthink it too much - AKs are designed to be incredibly tolerant, and nearly any steel would "work" for the gas block from a strictly functional perspective. Your friend probably specified stainless for corrosion resistance, given the fact that even the so-called "non-corrosive" bulk (i.e. cheap) ammunition will cause rust over time if the rifle isn't thoroughly cleaned. 416 ought to be nice material, but it's quite expensive and you may not be able to find it in the ideal size if you want to use rectangular bar. 316 is much cheaper, still machines halfway decently and is highly resistant to corrosion, particularly chlorides. That may be especially beneficial if the primers in the cheap ammo contain potassium chlorate. Price of a 6" long bar in the approximate size you would need is $35-$45 from McMaster (link (http://www.mcmaster.com/#standard-stainless-steel-sheets/=yfx0tf), 9083K21 or 9083K15); you could save maybe $5-$10 by going with 303 instead. 316, then, would be my recommendation.

Incidentally, a couple of notes on the gas blocks in general: first, they are meant to be an interference fit on the barrel. You need a measurement of the barrel diameter at the mounting location, and it really should be from HIS barrel, not a generic value. You'll need to have the existing gas block off to take that measurement as there's typically a step on either side of the gas block itself. I would try for .0003"-.0006" interference; give the breech end a small chamfer to help it get started. Also, unless this is a new barrel, trying to match the location of the holes for the retaining pins is going to be difficult at best. If it is a new barrel, go ahead and drill the pin holes - otherwise, consider making the gas block "taller" and leave room to split it on the bottom. Then, you can use clamping screws that go through holes perpendicular to the split. Make the ID of the hole for the barrel the same size as the barrel or slightly (<= .001) oversize if splitting the block.

-Brian