Is this something that a person with no gunsmithing experience can do. Was thinking of putting a BM M4 barrel assembly on my Oly upper. Will this work and can I do it or is it best left to a gunsmith. Thanks for the help.

Download  

TM 9-1005-319-23 (2.6MB PDF)
Unit And Direct Support Maintenance Manual M16A2, M4, M4A1

at [url]http://old.ar15.com/books/[/url] and look for yourself.  Section 3-10, about page 150~ish.

Not that hard, but does require some tools:

torque wrench
barrel wrench
barrel or receiver vise
molybdenum disulfide lubricant
correct size punch for gas tube

I'm doing my first one this week.

Not hard at all. f4yr gives some good advice on what tools you'll need - the only thing missing that I can see is a USGI field-guage to check for headspace.  Price of tools will add up quickly - so If you think that this is a one time deal - it may be cost effective just to have a 'smith do it.

Get the reciever vice block, it's more expensive than the barrel vice blocks, but much better.
[url]www.brownells.com[/url] has tham.

You should post questions like these in the Build It Yourself forum.  Not only will you get better, more specific answers, but it will also give me an excuse to restart the barrel torque/headspace flamewar with Dave_G.  [:P]

You know - there are other forums on this board besides General Discussion.  Take a look at them and you'll find a much better S/N ratio than this trash.

Just did my first barrel changeover last night.  I had the right tools and took my time but looking back, it was pretty easy.

I even screwed around with removing a front sight and reinstall....

Don't be afraid of what you don't know in this case.

If you are going to do this and acquire the tools mentioned, think about saving up for a new upper and bolt carrier assembly.  You will need a new, shorter, gas tube anyway. and hand guards also (I think).  For a few hundred more you can then easily switch back & forth.

Ditto on the headspace.  You can get "go" and "no go" gauges which I think are a better set up than the "field" gauge.  The field gauge is meant to avoid a disaster from excessive headspace, but will not tell you if you have insufficient headspace.  That can be dangerous. too.

With the "go" and "no go" set, you can try different parts until you get a good fit.  Read up on it first.

It's good to learn this stuff and how to maintain & repair your rifle yourself.

Headspace is set by the barrel assembler, hence while it's a good idea to check it, it's not something you need to "set"

In fact you can't really set it at all. You can only check it.

Actually, you even don't need a torque wrench.

In reality, there's only one notch on the barrel nut that will line up with the gas tube at anywhere near the correct torque.  So just use a breaker bar or one of those combo barrel wrenches with a built-in handle.  All you have to do is turn the barrel nut until it starts to get tight, then lean on the wrench until the next notch lines up.  That's it!

I get scorched in Build It Yourself regularly by a certain small faction of TM Worshipers who feel that the Army Way is the Only Way, and if they really think it makes a difference, then go ahead.  But I also frequently see messages from first-time rebarrellers who have tried and failed because they can't seem to get the right torque reading on the wrench and now they've stripped something or given up.  Unfortunately they don't realize that the AR upper receiver is a non-stressed part, and the only reason you need to tighten the barrel nut is to keep the rear sight from wobbling around in relation to the front.  They lose sight of what's important and get fixated with "torque on the brain."

One of the first times I tried to rebarrel an AR, I, too, had torque problems, so I stopped and called a buddy of mine who was a US Army SF Weapons Specialist and armorer in VN.  He laughed, and told me to get rid of the torque wrench and replace it with a breaker bar, then tighten the barrel nut by feel.  He said you should be watching the rifle, not the wrench!

So that's it - buy yourself a combo barrel wrench with a handle and a set of action blocks (much better than the aluminum vise jaws) and you're all set to begin rebarrelling ARs.

Next time I'll tell you why you don't need headspace gauges.  [:D]

[Edited to ficks speling misteaks]

Steel_Rat,

I can't really disagree.

The TM calls for torquing it 3 times to 30 lb-ft, and then cranking it the final time until it's lined up, anywhere from 30 to 80 lb-ft.

That's a pretty wide range.  80 lb-ft is a little more than the lug nuts on my car!  So the barrel nut can be cranked pretty good w/out worry.

"Set", as in "set of gauges"

I had one that would close easily on the "No Go" gauge, and cured it by trying a number of different bolts  until I found one that wouldn't allow that, but still was OK with the "Go" gauge.  That's about as close to "setting" headspace as you can get in the garage.

After reading all the tools needed and the cost to acquire them plus the extra parts you'll need it seems like it better to have gunsmith do it.

ASR