[ARCHIVED THREAD] - Contouring a HBAR

Posted: 9/22/2005 4:31:25 AM EDT

I've got a RRA middy coming, and I've got access to a full machine shop. I know there are companies offering to contour barrels, but I would like to do it myself if possible. Well, I havn't decided if contouring or just turning down to pencil-thin lightweight. Is it possible to do this or are their some special processes done to the barrel after machining, other than re-parking? Stress relieving, ect? Any help would be appreciated!

Posted: 9/22/2005 4:34:57 PM EDT

[#1]

No special processing after you profile, unless you want to send it out for Cryo.

Pull the front sight base off the barrel and put the gas block seat into the chuck so the extra barrel is inside the spindle bore.
Put a live center into the barrel extension.

Stay at least 0.875" over the chamber for at least 3" from the barrel extension and then stay at least 0.625" from there to the front sight base.

Randall Rausch
www.ar15barrels.com

Posted: 9/22/2005 4:54:38 PM EDT

[#2]

Randall, what does cryo do for the barrel? Do you get more life out of it? I work for a Harley dealer, we build hi-performance motors & race. As I understand it cryo relieves stresses in the metal which translate to longer part life and a stronger part overall. At least with engines. At least thats what the cryo people say! I can't say that I have seen the benefits of it first hand. It sounds good in theory but it's always been hard say conclusivly that this cryo'ed part held up better than this un-cryo'ed part. Of course, with racing parts they are typically rotated out of service pretty quicky, so we never had long term comparisons. Have you seen tighter groups, or less wear out of cryo'ed barrels? Also, are std carbide cutters OK? Are these barrels hardened or just like cutting std chromemoly? Other than that, thanks for the dimentions! That's alot better than the old cut and hope for the best!

Posted: 9/22/2005 5:25:28 PM EDT

[#3]

Cryo will just stress relieve the barrel which will make it wander around less as it heats up.
Lighter profiled barrels are more susceptible to this than HBARs.
You MAY get better groups because of less wandering.
I have not cryoed and "shot for groups" enough barrels to actually see if there is a difference.
Cryo is one of those things that can't hurt, but you also can't really quantify if it actually helps a specific barrel either, without before and after testing.

Regular carbide cutters will be fine.
There is usually not any heat treating on the chromoly after machining.

Randall

[ARCHIVED THREAD] - Contouring a HBAR

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[ARCHIVED THREAD] - Contouring a HBAR

[ARCHIVED THREAD] - Contouring a HBAR