MG 42 Build:Headspacing a New barrel?

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Re: MG 42 Build:Headspacing a New barrel?

Postby along » Sun Jan 31, 2016 1:57 pm

thank you for the response, I could not find that tutorial, I will take a look at it.

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Re: MG 42 Build:Headspacing a New barrel?

Postby along » Wed Feb 03, 2016 3:01 pm

ok so the collar on my apex barrel seems to be large. I read in the headspace tutorial

http://www.mg42.us/viewtopic.php?f=39&t ... ace#p91369

that you can add a shim to fix a short chamber situation. Does anyone know the exact size of shim? I have a new chrome lined barrel from apex for 8mm Mauser.

I do not have access to have a lathe so take off a minimal part of the collar. However I wondered if it is possible to do with a mill?

thank you for any help

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Re: MG 42 Build:Headspacing a New barrel?

Postby JBaum » Fri Feb 05, 2016 10:21 am

Shim stock comes in a wide variety of thicknesses, depending on what thickness you need.

I'd suggest doing a Google search for "shim stock" and seeing what's out there.
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Re: MG 42 Build:Headspacing a New barrel?

Postby along » Sat Feb 06, 2016 3:03 pm

so looking up shim stock I see it is the actual roll of shim. Is it better to cut the stock to length , make it a circle , and then use shims that way as opposed to buying shims out of the box?

thanks for the help

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Re: MG 42 Build:Headspacing a New barrel?

Postby along » Mon Feb 15, 2016 12:29 am

How does this shim stock look? I think its small enough thickness, how does this look?

http://www.amazon.com/Steel-Stock-Tempe ... NDZABK1292

I wondered if the hardness was enough for the pressures that build up in the chamber?

thanks for the help

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Re: MG 42 Build:Headspacing a New barrel?

Postby along » Fri Mar 04, 2016 12:59 am

so I bought some .001'' steel shim stock. So far I have added 6 shims between the barrel extension and barrel, so only .006'' added. The go and no-go gauge are still going in. Is there a typical thickness it takes for the no-go gauge to not go in?

thank you for the help

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Re: MG 42 Build:Headspacing a New barrel?

Postby rodom » Fri Mar 04, 2016 9:30 am

Along, something doesn't sound right here. As for the shim stock, this is the only way I've ever used it. It comes on a roll, and you cut and trim to fit your needs. Don't worry about hardness of the stock. I don't know of any "pre - made" shims for this application, maybe others do.
As to the gauges, you're adding shims to make the chamber area longer. If the No-Go gauge goes in, it's too long already. The go gauge should just fit with light "thumb" pressure on the back of the bolt, allowing the bolt to close into the camming piece and barrel. If the No-Go fits into that "bolt locked" position, the chamber is too long for proper head spacing. The other builders need to add their expertise here, as it seems to me Along is moving in the wrong direction with this problem. Also, if you haven'd done this yet, the bolt is normally stripped of ejector and extractor components, so you are sure you're only working with the bolt face to chamber fit. The extractor/ejector will cause the gauges to not "seat" on the bolt face properly, incorrectly indicating a shallower chamber length than is actually present.
But as I said, the more knowledgeable builders need to step up and add their experiences here. Sounds to me like Along could use a friend here who has been thru this before.

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Re: MG 42 Build:Headspacing a New barrel?

Postby JBaum » Fri Mar 04, 2016 6:28 pm

The gauges "go in". What does that mean, exactly. Do the bolt rollers go fully outward? I've never needed to take off the extractor or take out the ejector pin, or the firing pin either. Everything depends on having the bolt rollers be fully outward when you measure the headspace with the gauge.

This is why original barrels are selling for $275. Setting headspace on a new barrel without the tools, understanding, and experience is a big pain.
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Re: MG 42 Build:Headspacing a New barrel?

Postby rodom » Fri Mar 04, 2016 7:14 pm

Hi John. That's why I asked for some of the more experienced builders to chip in. I've head spaced my FAL, using the bolt with the extractor and ejector removed to get the spacing correct. With those rifles, you use machinist pins of various sizes to determine which locking shoulder pin is the correct size. I've also done a Winchester Md 70 bolt action rifle, again with the extractor and ejector removed to determine if the barrel was "screwed in" far enough. I've never done an MG42 or M53, but what Along was describing didn't sound correct to me. I do believe you are correct in that since he's in over his head he should purchase an original barrel. Does anyone out there offer head spacing services? You might want to contact one of the manufacturer's to see if they might have tooling in place to perform this head space.

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Re: MG 42 Build:Headspacing a New barrel?

Postby JBaum » Fri Mar 04, 2016 7:40 pm

Many people have headspaced barrels, nobody likes it. I don't know of anyone who does it professionally, as setting the headspace is specific to the bolt, as there are variances. Someone would surely want to sue when there's a problem after they start swapping bolts. No offense to anyone on here, just being realistic.
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Re: MG 42 Build:Headspacing a New barrel?

Postby along » Fri Mar 04, 2016 8:03 pm

Would there be a point in buying a pre-headspaced barrel since I don't know if it will fit my bolt?

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Re: MG 42 Build:Headspacing a New barrel?

Postby JBaum » Fri Mar 04, 2016 10:17 pm

99% of the original barrels have correct headspace with 19 out of 20 bolts (my estimation). I've seen one out of 50+ barrels I've checked that was so far out it wasn't safe to shoot with any of the 10 bolts we tested it with.

Everyone else

I have 5 bolts and 8 barrels. Only one combination doesn't headspace correctly.

The point is, it's almost a certainty that a factory bolt will headspace OK with a factory barrel. At the worst, you might need to find another bolt head to get it to fit right, which is much cheaper than buying another barrel.

I'm not saying you can't get what you have to work, I'm saying for me, it wouldn't be worth the trouble. Fortunately, I've had my stuff long enough that I paid $35 for .308 barrels and $40 for 8mm barrels. At today's prices, I still wouldn't buy a blank and try to make it work. Time or money. Spend whatever you have the most of to save the other.
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Re: MG 42 Build:Headspacing a New barrel?

Postby along » Sat Mar 05, 2016 6:12 pm

Wow that is really good statistics for barrels working with factory bolts, I'm glad it is that good. Is there any work I can do to my bolt head, such as take off material to decrease the headspace? I certainly would like to save money (however I do have time as well). My factory barrel hasn't been modified or anything, and they're sold out on apex just recently, so people must be wanting to buy them. If I could find a buyer I would definitely sell it. Also what would be a good cost for a factory barrel? I would certainly wouldn't mind owning an original barrel.

thanks for all the input and help, really appreciate it

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Re: MG 42 Build:Headspacing a New barrel?

Postby JBaum » Sat Mar 05, 2016 8:53 pm

Technically it's possible, but being practical about it, there's nothing for you to do to the bolt head that would be a safe way to set headspace using the bolt. Besides if you did, it likely wouldn't work with any other barrel.

About 5 messages up this thread I said barrels were selling for $275...

People are buying new because they either can't find an original, or they think it's not much trouble to set the headspace.
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Re: MG 42 Build:Headspacing a New barrel?

Postby along » Sun Mar 06, 2016 4:21 pm

ah very true, thats right so $275 isn't too bad, especially if I could my new barrel. Do you know where they are selling for $275?

thanks for the help

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Re: MG 42 Build:Headspacing a New barrel?

Postby JBaum » Mon Mar 07, 2016 9:50 am

Check your private messages.
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