M14 Forum banner

Some Bolt Help - Warbird, Ted Brown, M14Dan, Bill Ricca?

1309 Views 3 Replies 4 Participants Last post by  m14dan
Ok, I know I have like 3 posts below this about bolts and you guys are probably sick of answering questions about it, but I have searched Amback, this site, and Warrifles through all the bolt threads and still have questions. I'm hoping that you guys mentioned above will chime in since you are regarded as the experts (I'm sure there are others qalififed too so I don't leave anybody out). Here goes:

1) I guess my main question is, with all the talk about headspace all I ever seem to here is that it either fits or it doesn't. What exactly is a bolt that "doesn't" headspace. Does that simply mean that it either will not close on the GO gauge or it does close on the FIELD (or possibly NOGO) gauge. Is that the definition of a bolt that doesn't headspace. Is that all there is to it.

2) Beyond that, am I to assume that even if the bolt closes on the GO and does not close on the NO GO that I still have something to worry about concerning contact area? How do I determine contact area? If it passes the GO and NO GO test with the gauges how important is contact area?

3) I am totally confused about lapping. Is lapping adding material to the bolt, adding material to the receiver, or is it taking material away from either the bolt or the receiver? Or is lapping just a term used to say that your are changing the bolt a little to make it fit.

4) I have a bolt on the way. I have Forster .308 headspace gauges for GO, NOGO, and FIELD. I guess what I am wondering overall is this. I have a 2003 SAINC rifle with a USGI chrome lined Winchester barrel and SAINC forged bolt. I have a used, but good condition USGI Winchester bolt on the way to me. I want this Winchester bolt to be my backup bolt since I haven't had any problems with the SAINC bolt. If I take the bolt apart and use the GO and NO GO gauges and it closes on the GO and not on the NOGO does that mean that the bolt headspaces correctly and is safe to use? I want it to be able to shoot both surplus and commercial ammo. That is the meat and potatoes of my question right there. Or do I need to send it to an armorer or something?

I know I asked a lot, but in my other posts I got one person telling me one thing and then I got another telling me that the Forster NOGO is really the GI GO gauge. So it would be great to get a definitive answer.


See less See more
1 - 4 of 4 Posts
What is tripping you up is that there are 2 different headspace specs: NATO 7.62 and SAMMI .308 Win.

The civilian SAMMI spec is tighter (shorter) than the military NATO spec. That's why the NATO GO gauge is longer than the Forster NOGO gauge -- the Forster gauges are based on the SAMMI spec.

From what I've read on the net & from previous discussions on this subject, the rough rule of thumb is that if your rifle headspaces to the SAMMI spec you should be OK to shoot both commercial and milsurp ammo. If your rifle headspaces to NATO spec then you can shoot only milsurp ammo. The supposed "sweet spot" is 1.632.
At the beginning, the headspace should be "short". Just under specs.

"Lapping" he bolt helps lengthen the headspace to acceptable specs AND is used to create a flush and complete vertical contact area between the front receiver lugs and the back of the front bolt lugs. An abrasive compound, or "Lapping compound", is used between the two surfaces (lugs) and the stripped bolt is worked by hand into and out of "lock up". Every couple of strokes the "lapping compound" is removed and some "Blue Goo" (I can't remember what it's called) is applied to one lug surface and not the other. It is used to check the percentage of actual contact area. Once the "Goo" is applied to the receiver lug surfaces the bolt is then closed into "lock up" and opened. The surface that started "clean" is then inspected to see exactly where, and how much of the "Blue Goo" was transferred to it during the closing of the bolt. Ideally there will be 95% - 100% vertical contact between the lugs at the exact moment the bolt headspaces correctly. Lapping takes a very small amount of material off both the receiver lugs and bolt lugs to achieve both the proper headspace along with acceptable lug contact.

NOTE: The above explanation will be less than 100% correct and incomplete.

My experience with the questions you posed is that you won't get too many specific answers due to two things.

First is the "Safety Factor". Many qualified gunsmiths are hesitant to give intricate knowledge of their trade to "lay" individuals. We're dealing with demanding tolerances under a great deal of stress and pressure. It's a case of "Most modifications of this type are best left to professionals". And taking into consideration the amount of damage an unserviceable firearm can do, and the knowledge and experience level the average "Joe" has working on firearms, most people probably shouldn't perform certain operations on their own weapons.

Second. If I have the necessary experience, skill, and confidence to call myself a professional, or "Gunsmith" capable of performing these operations for others, for $$$, why on earth am I going to tell everyone else how to do "my" job. Don't get me wrong. I'm not bagging on gunsmiths. ('cept for one, see sig below) I'm just trying to inform you why possibly what you've read in your other posts hasn't been specifically what you're looking for.

See less See more
Some of the chicoms will accept a gi bolt as is. Most will not. You do need to get the gi feild gauge too just for the heck of it but maybe you should wait till you have the bolt and know more where you are. It is available as part of a match set or individually.
Lapping is gonna remove metal. All of us have our preferances on how to do it and I think we all do it different. The trick is not to remove too much. Gluing all those metal specs back where they came from is no fun.
Also on chicom barrels the rear most face of the barrel often has to be adjusted to accept a gi bolt. This is another reason we usually say to let the pros with the right gear do it. That is best done on a lathe although there are other ways.....

Whenever you do get to working on it just take your time, ask more questions and by all means call one of us if you get stuck. Don't take any risks.
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.