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Posted: 2/3/2006 12:37:24 PM EDT
[Last Edit: 2/3/2006 1:02:05 PM EDT by webtaz99]
I have contacted a local smith who is willing to replace the extension on my barrel.

(Before you ask why, let's just say I screwed up and leave it at that.)

Are there problems I should know about, in order to ask him to avoid it?

On my build I use a gas block separate from my sight base, so I believe the indexing does not have to be perfect.

He asked me to provide my upper, carrier and bolt to check headspace.

What else?
Link Posted: 2/3/2006 1:24:12 PM EDT
[Last Edit: 2/4/2006 6:58:43 AM EDT by M4Madness]
Your gas port timing will still need to be perfect in order for your gas tube to be top dead center. If you are set on using your existing barrel, you'll need to weld up the original gas port and drill a new one TDC after the new barrel extension is torqued.

Basically, it's easier to trash a barrel and buy a new one than it is to mess with another barrel extension.

EDIT: This is assuming that you have a chrome-lined barrel.
Link Posted: 2/3/2006 1:41:56 PM EDT
lining up the bbl extension would require more work than its worth.


replace the bbl.
Link Posted: 2/3/2006 7:51:01 PM EDT
I have done it but it requires having a lathe and an experenced operator. Timing the index pin to an existing gas port is finicky but possible. However, it does depend on the extention coming off clean. sometimes the index pin will destroy the existing threads when removal is attempted with the index pin in place. In that event your only option is go to the next shorter gas system and rethread, rechamber, and reinstall.
Link Posted: 2/3/2006 9:40:06 PM EDT
I always thoought it would be worthwhile for a place that re-barrels DCM guns to take the shot out barrels they take in & make thin into 18" barrels. They could cut off the barrel ends, re-set the extensions one full turn to re-allign the gas port, and reinstall the extension. Then, run the chamber reamer again.

They would be too short in length for DCM after that, but perfect for our uses. All those kreigers going to waste - sigh.

Link Posted: 2/3/2006 10:01:14 PM EDT
I have done that twice, first and last time...

I did it because buddy of mine wanted his 16" (Wilson or Olympic) barrel shortened to 11.5" and .223 Rem chamber modified to .223 Wylde. Reason for this was extremely bad jams, FTE, broken bolts, etc.

Before I started the whole project I bought quite bunch of barrel extensions to make sure everything goes right.
Handful of barrel extension makes minimum shortening possible, I had to shorten barrel less than .060" which is enough for the Wylde chambering to be in correct depth.

Long story short,

1. took the old barrel extension off
2. reamed new chamber roughly to dimensions
3. took the closest match of barrel extensions with alignment of index pin and gas port
4. torqued barrel extension
5. reamed chamber to correct depth/ checked headspace
6. test firing

This painstaking operation gave new life for the barrel and has been hundreds of shots w/o problem.

Was it worth it? Maybe, buddy of mine is happy and I learned a lesson not to do things w/o thinking twice...

NOTE! this works only on non chromelined barrels.

MN
Link Posted: 2/4/2006 6:37:31 AM EDT

Originally Posted By Toolman_556:
I have done it but it requires having a lathe and an experenced operator. Timing the index pin to an existing gas port is finicky but possible. However, it does depend on the extention coming off clean. sometimes the index pin will destroy the existing threads when removal is attempted with the index pin in place. In that event your only option is go to the next shorter gas system and rethread, rechamber, and reinstall.



Are you saying the index pin must be removed first?
Link Posted: 2/4/2006 9:42:44 AM EDT

Originally Posted By webtaz99:

Originally Posted By Toolman_556:
I have done it but it requires having a lathe and an experenced operator. Timing the index pin to an existing gas port is finicky but possible. However, it does depend on the extention coming off clean. sometimes the index pin will destroy the existing threads when removal is attempted with the index pin in place. In that event your only option is go to the next shorter gas system and rethread, rechamber, and reinstall.



Are you saying the index pin must be removed first?



Sometimes, yes. Some counterbore the barrel threads so that the index pin essentially locks the extension in place. Not all do, I believe, but it is quite common. And if they are in tight, they are a PITA to get out.

For the unknowing, this job has "OK, nevermind." written all over it.
Link Posted: 2/4/2006 7:57:25 PM EDT
Just buy a new barrel. The extension was not intended to be a replacement item.
Link Posted: 2/5/2006 11:11:36 AM EDT
[Last Edit: 2/5/2006 11:17:22 AM EDT by Russ4777]
If the gas port is already drilled in the barrel you are going to use then forget changing the extension. It is just too much work to do it right. Your smith is willing to do it because he is preparing to charge you WAY more than a new barrel to do the job.

If your existing chamber is chrome plated the job my be impossible since you cannot successfully ream a chrome chamber to get the correct headspace after installing the new extension.

Just go buy a new barrel and use this one as a tent stake, prybar, or a club.

You might also consider investing in a good maintenance/operator's manual to better familiarize yourself with the maintenance and operation of your rifle. This might help you avoid damaging another barrel in the future.
Link Posted: 2/6/2006 11:55:03 PM EDT
Link Posted: 2/7/2006 6:38:38 AM EDT
What is involved in setting the headspace on a brand new barrel?

I guess that the extension is torqued until the headspace is good, then pinned, and the gas hole drilled to match the pin. I also assume that if the extension needs it, some material (.001 or so) might be removed from the forward end.


Link Posted: 2/7/2006 6:56:54 AM EDT
Link Posted: 2/7/2006 11:01:46 AM EDT
Thanks for all the input. New barrel is on order.

That which does not kill me makes me wish I hadn't done it.
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