I'm looking at maybe picking up an A4 varmint 20" upper (it looks like a DPMS) that I saw the other day and later mating it to a RRA lower w/ match trigger for a distance gun.  

This upper has the assist and charging handle, but no bolt/carrier.  How hard is it to obtain and install them (I understand that proper headspace is the issue)?  How much should I expect ot have to pay for parts and gunsmithing?

i would suggest talking to a gunshop person, youve got lots to learn..but for intertainment purposes here we go:


The upper you are gettin already has the barrel attached to the upper reciever? If this is true than the headspacing is already done at the factory

Go online to any AR manufactor and get what ever bolt and T handle ya want. (make sure its a complete bolt)

Get a good manual on how to operate, tear down and clean your AR, read it before ya ever go to the range, keep reading it, take your AR apart and put back together and function test it per the manual , BEFORE ever setting foot on a range

As far as putting the upper, bolt and lower together, it literary takes 30 seconds if all parts arent fucked up.

LSJ: Go to the Home page of AR15.com and go to "Manuals". Download the -10 Field Manual and read up on the assembly/disassembly of the M-16. Since you do not have the original bolt, the factory headspacing is history. The headspacing is done between the bolt and the barrel extension/barrel assembly. A new factory bolt will PROBABLY headspace correctly; however, this is one item you don't want to take a "probably" on. Either buy the headspace gages or have a competent smith check it. Bushmaster sells the gages as well as other big companies. A new bolt/carrier assembly should go for about $120. The lowest that I have seen was from Bushmaster at Camp Perry two years ago for $105.

Thanks ArmyOrdGuy.  That's the kind of useful info (as opposed to the other kind) that I was looking for.  You have confirmed what I thought was true, but wasn't really sure about, when using a non-original bolt.

This won't be my first AR, but it would be the first upper I've used that isn't complete from the factory.  I just want to avoid the avoidable problems if I can.  

Glad to help. One other thing: when you get your new carrier, slide the carrier ONLY into the upper and see if it hits on one side or another off the gas tube. If it noticably hits, carefully and firmly pry the tube to make alignment. The tube is tough and won't bend easy. Just do a little at a time until centered.

Whether or not the barrel is mounted on the upper receiever, it has nothing to do with headspace.  Headspace is not adjusted in assembly.  Headspace is set by machining the chamber and barrel extension, and the bolt face and lugs "to spec".  

So, no opinion can be made about the upper receiver and headspace without having a bolt.

You, as the end user, or assembler of such parts, can do nothing to adjust headspace.  BTW, the bolt carrier has NO EFFECT on headspace, again, that is a function of machining of the barrel parts and bolt.

OK, the easy part is this, you can take just about any new good quality AR15/M16 barrel, and combine it with any good quality AR15/M16 bolt, and chances are about 99.999999% of the time, the headspace will be OK. And that other .0000001% of the time, it will not result a kaboom if headspace is not within certain tolerances.

So, what you do is simply order a bolt carrier assembly and charging handle from [url]www.armalite.com[/url], [url]www.jtdistributing.com[/url], [url]www.bushmaster.com[/url], [url]www.dpmsinc.com[/url], [url]www.olyarms.com/usa.html[/url], Rock River, Fulton Armory, and I am sure I have left out a few others.  I have purchased from all of these places but RRA and Fulton (but they have a good rep).

A bolt carrier assembly will set you back about $110-$120.  That is carrier, with key installed, bolt with all parts, firing pin, firing pin retainer, ready to drop in and shoot.

Now, I am partial to the slightly more expensive Armalite charging handle, at $24, which is made a little heavier than others on the market.  On the other hand, this is not a high breakage item.  Anyway, Armalite's bolt carrier assembly is $110, and about the same as most others, pricewise.  The quality is good, and you could certainly do worse.

Now, simply assemble your rifle and go shoot.

As stated above, headspacing is done as part of barrel/extension assembly.  There isn't much we can do about it.  Put a new bolt/carrier in the rifle and shoot.  

Why are so many people suggesting he buy a new charging handle when he says that he already has one?

Ok I have a question. How about a used upper/barrel with a new bolt carrier? Is it "more critical" to use a go/no setup on a used upper? I assume the answer is yes, but that is what I'm faced with now?

Duh, I thought he had an upper half WITHOUT the bolt carrier assy and charging handle.  My mistake.  All he needs is a bolt carrier assy.

cgebhard asked:  "OK I have a question. How about a used upper/barrel with a new bolt carrier? Is it "more critical" to use a go/no setup on a used upper? I assume the answer is yes, but that is what I'm faced with now?"

If both the barrel and bolt were very old, such as some of those imported junk parts kits made from worn out M16's, or a very old heavily used rifle, I would say yes, check the headspace.  If the upper looked to be in pretty good condition, I would just drop in a new bolt and go shooting.

Be aware that .223 gauges in the AR15's looser chamber may not give a good indication of headspace.

Examine the fired brass for the shiny rings just above the base that indicate stretching.  If you see those, yes, the headspace is excessive.  But still, it isn't gonna blow up.  If you reloaded that same brass and used it in that same rifle several times, you will may a case head separation.  But if you were going to fire new ammo only, it would probably not give a problem.

If the used upper does not look trashy, is at all presentable, and the inside of the upper receiver does not look excessively worn, I would just chunk a new bolt in it and go shooting.  But that is what I would do.

I will note that more than a few guys have gotten very upset, and discarded perfectly good bolts and barrels from using .223 headspace gauges.  You can get eronious readings with new barrels and bolts.

There is a tacked thread about this, I think.