Alan Waters

Found this question in a thread that had been closed. [seen plenty of videos and write up about headspacing, but no one ever talks about how to correct it! So you determine that your headspacing is wrong. Then what????? Please dont say take it to a gunsmith, the point of this is DIY.] Well, unless you are a gunsmith or a machinist you have to take to one. So, what is excessive headspace and how is it corrected? Headspace is the distance from the case head [where the primer is] to the face of the bolt when there is a cartridge in the chamber and the bolt is closed. The cartridge shoulder is being pressed firmly against the chamber shoulder. This stops the forward movement of the cartridge and the bolt applies pressure to the case head to hold the cartridge stationary when the gun fires. This distance should be Zero but usually is not. Why should this distance be Zero? Several reasons. Number one is safety. When the gun fires, if the brass cartridge case is not held captive by Zero headspace the case move to the rear as the bullet moves forward. This means the case backs out of the chamber until it contacts the boltface. It this distance is great enough, the cartridge case, unsupported by the chamber will blow a hole in the unsupported brass. Not good when 30 to 50,000 psi is that close to your face looking for a way out of the firearms action. Number two is also safety. If the case did not blow out it definitely stretched the brass, and if it is reloaded that brass now has a thin spot and may or may not fit in your chamber.The SAMMI spec. for .308 Winchester is two thousands max between go and no go. The field specs allow eight thousands. If you want to know what the headspace is, and you should, all you need is a go gauge of the proper caliber and a set of feeler gauges from the auto parts store. The flat leaf type used to adjust valve clearance. First, remove the extractor and the ejector. If you don't do this you are wasting your time. Cut a piece of the .001 feeler gauge small enough to fit in the bolt, up against the bolt face. Insert your go gauge and close the bolt. You will have to hold the rifle slightly barrel high to keep the feeler gauge in place. If the barrel is too high the gauge will try to slide back out so its a balancing act. If all fails place a TINY drop of oil on the bolt face under the feeler gauge.This acts as an adhesive to hold the feeler gauge in place. Understanding if you use the oil it may add a thousands or two onto the measurement. If the bolt will close on the one thousandths cut a piece of two thousandths and repeat. Keep going up in size until the bolt will not close. OK. Now suppose there is nine thousandths excessive headspace. How do you get rid of it. There is only one way. The barrel must be removed and place in a lathe. Nine thousandths material must be removed from the shoulder of the barrel where it fits against the barrel extension. Yes it could be removed from the barrel extension but the heat treat on those parts is very hard. In any event, the barrel chamber needs to move toward the boltface nine thousandths to achieve Zero headspace. Having done that, depending on how much clearance the front of the bolt locking LUGS had from the rear of the barrel, before the barrel was set back, it my be necessary to remove another nine thousandths from the rear of the barrel to allow clearance for the front of the bolt locking LUGS. If, by mistake, too much was removed from the barrel shoulder and the barrel goes too far to the rear, the only fix is to use a chamber reamer of the correct caliber to deepen the chamber to the point where the go gauge will fit properly. I have tried to write this so that the person with little or no knowledge of the subject may be able to understand it. That was me 40 years ago and all of you at some point. Note. Head space measurement on a blueprint will be read from a point on the shoulder of the chamber as can be seen in the drawing below. http://forums.thecmp.org/showthread.php?t=146769 Regards to all, Alan Waters

I have used both 620 and 680 to secure compensators to 38 Supers and .45's You have to bake the barrel at about 500f to break it down. Even then its a job for a wrench and barrel vise to unscrew.

http://www.6mmbr.com/gunweek090.html

Welcome.

I’ve been reading on 6BR forum for years but mostly about bolt guns.

10. Front/Back Bolt Play: If accuracy is the game, don’t leave a lot of front/back bolt play (keep it .003″ but no more than .005″). We’ve seen factory rifles run .012″ to .015″ play, which is OK if you need to leave room for dirt and grime in a military application. However, that amount of play is not ideal for a high-accuracy AR build. A lot of front/back bolt play allows rounds to be hammered into the chamber and actually re-formed in a non-consistent way, as they are loaded into the chamber. Excerpt from 6mm BR .COM ARTICLE ON THE ACCURATE AR

http://bulletin.accurateshooter.com/2015/05/what-makes-an-ar-accurate-whitley-offers-answers/

As former law enforcement officer, I would call that a good shooting. May not get a second chance to chamber a round at the gas pumps.

As former law enforcement officer, I would call that a good shooting.

Barrel extension is made by Dan Lilja. And yes they are hard. A file just skates over it. Not going to cut it.

Thank you Kiwi308. Understood.

Yes.

Yes. Too both questions. Pushing on the extension will push the carrier to the rear and the extension will seat properly. I will remove the bolt from the carrier in the morning and have a closer look. May have to face the extension about .030.

Front of bolt carrier contacts rear of barrel extension. Pushes barrel extension forward .025. How much clearance needed between the two?

Found it. Threaded take down pin hole right beside the safety detent hole under the pistol grip. Thank you all.

Well, I'm old and ugly, and I'll have to get Matt Cross to teach me how to post photos.

Bought my Aero M5 upper and lower from a local dealer a few months ago. Fed X delivered my care package on the Tuesday. BCG, small parts, Magpul PRS, Timney Calvin elite, buffer group. All from Aero. Assembled all. One problem. Safety detent pin would not protrude into safety. Either the shoulder in the receiver hole was machined shallow, or the detent pin was out of spec. with too much shoulder. Machined the hole shoulder deeper. Problem solved. Ended up with two extra roll pins and a tiny set screw [looks like a 4-40 x .125] left over. Finally figured out one roll pin would have gone into the bolt release. Aero has a threaded pin in place for that. That left one roll pin and the set screw. Spare roll pin maybe. As for the set screw. No clue. Bought the barrel extension from Dan Lilja. Nice work. Excellent fit. Tight. http://riflebarrels.com/shop/accessories/ar10-barrel-extension/ Hope to chamber the barrel next week. Regards to all, Alan A side note. Had a very enjoyable [ 2hours ] breakfast with Matt Cross this morning. Picked his brain. Thank you Matt,

Thank you all.

Anyone using the Law Tactical folding stock adapter? Pros, cons.

Anyone know a source for straight gas tube material?

Name the place and time. I'll meet you there.

Conover NC

Good stuff.

http://panhandleprecision.com