View Full Version : Head space after changing a barrel
markfische
05-20-12, 12:43
This is my first post on any forum ever so sorry if I ask a stupid question. I have an M16A1 (yes I have a class 3 permit to own it)I carried its brother in Vietnam, so I wanted one. It has the pencil barrel 1/12 and I have shot 10's of thousands of rounds through it. Including (stupidly, but it was fun) a 125 round snail magazine on full auto until it was empty. Now however even the 55 grain military bullits key hole at 50 yards and I have a 25 inch group. (actually great if you are a really bad shot). I have purchased a new barrel and have the choice of going to a gunsmith or replacing it myself. It turns out buying all the tools and equipment to do it is cheaper than going to a gunsmith except for the go/no go gauges.
I would like to do it myself, its who I am.
The article I read says I dont need the go/no gauges because any good barrel is already set for the correct head space. I've looked at the barrel, nut etc and there is no adjustment.
So. can I just screw on a new pencil barrel and be happy or am I being a moron trying to save $100.
Have you considered installing the barrel and then having the gunsmith gauge it for you?
markfische
05-20-12, 13:23
No I haven't. I haven't found a local gunsmith that is truely interested. Once again that makes me reliant on someone else and I would really like to know how to do it myself. I know I can do this, I just need the facts. Im not stupid. I have many other black rifles and would like to be able to maintain them, modify them, and be safe. I don't want my son to loose an eye because I'm poorly informed. I couldnt't live with myself. Thanks for your response.
mkmckinley
05-20-12, 13:37
Best bet is to find a USGI 'Field" gauge. Use the search function and you'll get an idea what's involved and buy Glen Zediker's book (http://www.zediker.com/books/BB/BB_main.html) or something similar. It's not rocket science but it needs to be done right and with the correct tools. BTW don't skimp out on the tools.
Headspacing has been discussed in several threads and searching the forums with diligence will yield a wealth of information. It is worth your time to gain the knowledge. It's a simple process once you understand it.
Short version is that the barrel & barrel extension are set to a master bolt so each is held to a specified tolerance. Bolts themselves are also made to a set tolerance. It is very rare that a new barrel assembly and new bolt combination will result in the headspace being off. Some companies offer to match bolt to barrel assembly for a extra fee
The simplest way to verify headspacing for the home assembler, is by using a round of quality factory ammo as a gauge. Contact Iraqgunz for a more complete description on how it's done.
Welcome to the forums. It would be awesome if you were to post photos and/or videos of your M16A1 in the "ARs In Action" thread stickied in the AR General Discussion forum
markfische
05-20-12, 13:53
As I've said Im new. I ordered the book you recommended (not cheap) but knowledge is priceless. Thanks for the response. I will try to go through the old information and get what is needed
Are you going to replace the bolt? If you have put 10’s of thousands of rounds through it then I think it would be a very good idea. Headspace is the relationship of the barrel and the bolt not just the barrel and barrel extension. If you are going to use the old bolt then you really do need to check the headspace.
I'd second replacing the bolt and with a full auto you definitely want the GO dimension set properly. I suspect your A1 is worth a small pile of money and ammo isn't cheap either, don't skimp on doing it properly.
blackjack_03
05-21-12, 05:58
I recently purchased this (http://www.brownells.com/.aspx/pid=6646/Product/5-56mm-223-HEADSPACE-GAUGE) to use on a build I just completed. It worked well for me. From my research all you need is a field gauge. It is inexpensive and shooting the way you do you should have one.
If I were you. I would look at a quality upper from Bravo Company and simply replace the entire Upper Receiver Group. I would then get a new BCG as well. Take the original upper and bunker it away.
If I were you. I would look at a quality upper from Bravo Company and simply replace the entire Upper Receiver Group. I would then get a new BCG as well. Take the original upper and bunker it away.
+1. That's also what I would do. Or, since you already have the new replacement barrel, I would buy a new upper receiver (perhaps an A3 flattop this time so you can enjoy the privilege, nay the pleasure of properly placed optics ;)) as well as a new BCG to go with it. Complete BCG's can get pricey, so if that's not an option, I'd at least get a new bolt to go with the new barrel and upper.
This way, you can store that old M16A1 upper and keep it for nostalgia, sentimental value, and simply for the fact that it's what came with the rifle originally.
Lots of guys don't check headspace after replacing a bolt or barrel. I do because I like seeing and haveing a relatively unscarred face.
You've got a ~$12k receiver you're going to risk instead of buying a ~$100 gauge set? Really?
H
Maybe $40, GO and FIELD. ;)
If I were you. I would look at a quality upper from Bravo Company and simply replace the entire Upper Receiver Group. I would then get a new BCG as well. Take the original upper and bunker it away.
I also agree with Iraqgunz. You have likely reached the end of your bolt's lifespan. Buy a complete upper.
markfische
05-25-12, 15:02
I want to thank everyone for their responses. Every one has been helpful.
I do want to keep the "classic" look of the M16A1. It has many memories for me so it does make the barrel selection and upper selection limited. I have the correct barrel now just with a different twist.
My new issue is some people seem to use bolt and bolt carrier interchangably. Do I need a new "bolt", bolt carrier or both. Also if I can find the exact specs and mine is still in them I should be ok.
Thanks again everyone.
If you put enough rounds through your barrel to wear it out then your bolt is toast or soon will be. Get a new bolt it’s like $60 for a good one.
You will need to replace the bolt.
I'm not sure you need to replace the carrier, but doing so is cheap insurance. I would buy a good complete bolt carrier group new
Even though you want to keep the same look, and swapping the barrel and BCG, it might be a good idea to get an extra upper anyway, so you can swap it out when you want to do classes, mount a red dot, go plinking etc. It will make the carbine more practical. and an extra upper never hurts. ;)
The bolt is going to break sooner or later.
If it was mine I'd save the old bolt (for a spare) and run the new bolt with the new barrel.
And I would also check both bolts for headspace before running rounds thru the rifle.
H
Personally I'd buy a new BCM bot and bolt carrier. If you have put that amount of rounds down range it's time for a new one. You could have some amount of wear in the cam pin track. Don't quote me on it but I think you can get a BCM complete bolt and carrier for ~$160. Try G & R Tactical!
I would also recommend a complete new upper.
Keep the original A1 upper for nostalgia
Use the new upper for fun, and to keep from wearing out/breaking the original upper.
Just my $.02
With the round counts you mentioned I would replace the bolt also.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.