Posted: 3/29/2005 2:11:35 PM EDT
|
Recently I purchased a Colt Bolt. It is almost new condition with very little wear. On examination though I notice that there are small divets, or some kind of machine marks, that extend a few milimeters back on a 45 degree angle behind each lug. I have never seen this before. They appear to be machining marks of some kind and are consistent all the way around the bolt. My question is, will these affect function in any way? I have no problem if they are cosmetic. After all it is a bolt. I just want it to work right. Let me know what you think or if you have ever seen this before. 
|
+1 I have even seen DPMS bolts with the same cuts in them. |
| my new 6721 with m16 bolt carrier does not have those marks.hock.gif |
|
All bolts currently manufactured should have the 45 degree locking lug relief cuts around the back side of the engaging lugs. Have not seen an M16 / M4 or Colt weapon yet without the reliefs. The marks that appear in the photo that are lower than the lugs are not normal but consistent with the machining process in cutting the lugs. Probably from a batch where tolerances were not checked prior to the production run. Either way those marks will not effect the operation of the bolt. JohnM at Home |
New production bolts don't have them. The 45 degree cut on the bolt lug edge no longer cuts into the bolt body. Here is a early 60's AR-15 bolt, it has the cuts in the bolt body (so have all the 60's bolts I have had).  This is a 1970's M16A1 bolt, also with the cuts in the bolt body (all the 70's bolts I have had have cuts):  This is a 1995 Carbine bolt, no cuts in bolt body (never seen a 90's bolt with them):  I don't currently have a 1980's bolt, but far as I know they don't have cuts in them either. Edit: Bonus tip, check and see if it has an extractor buffer, and if so what color. 1960's to early 1970's bolts did not have them, mid 70's had white buffers, late 70's had red/orange. |
Certainly not, 1970's bolts are up to speed. Almost seems like you are looking for something wrong with it? |
No, not at all. The bolt is in excellent shape and was a great deal when purchased. Once determined that the marks were normal I was curious as to what caused them or why they were put there. Those kind of things peak my interest and amazingly AR15.com always seems to provide an answer. As far as the metal differences between then and now...this bolt group was parted out between two rifles. The M16 carrier replaced my half circle carrier in the LE6920 and the bolt went into another build. If the current bolts and carriers are of better metal quality I was just going to swap the half circle back into my LE6920 and use the M16 carrier also for the build (range gun only). By the way, thanks Elkie for the good deal and info too  .
|
Did you get the bolt from me? |
This is a Bushmaster bolt purchased from BM in 2004 This is a bolt from my 1964 SP1. It has those machining marks on the lower part of the bolt body.  This is a Colt M4 bolt from a Colt M4 SOCOM upper. Barrel dated 11/00  All the bolts have the relief cuts on the lugs. As they should. It appears that the early bolts are those that have cuts in the bolt body. I will post some more photos from my units Colt M16A2's, both Colt and FN. Also will grab a couple pics of our new M4 bolts as my unit is transitioning to M4's and we just got the newest production units. JohnM at Home |
Seems to me that the cuts in the bolt body are a result of the end mill bit that but the beveled edge on the locking lugs. I don't think those cuts are a required spec, but are instead simply caused by bolt lug edge milling. Some individual early bolt lack these cuts, and I think that is simply a variance on how the mill was set up, and not the norm. At some point tooling was changed so that the mill no longer got into the bolt body. I don't know exactly when this happened, because I don't have any 1980's bolts, and those that do give conflicting info.
A good portion of the 1991 COLT MFG CO rifles were made up up left over COLT FIREARMS DIV parts. So a pretty good chance that is a 1980's bolt. Again, some say thier 80's bolt have them, and others don't. Not sure what to make of that. |
Does your wife/significant other know you keep AR bolts in the jewelry box????? Ya redneck......  .
|
|
Ekie is right. All bolts have the 45 degree cut on the lugs. If the cut extends into the body, it is a side effect of the process used to cut the angle in the lugs. I have Colt bolts with and without the cuts extending into the body. I've also noticed on many of the older bolts the cam pin hole is rougher around the edges. On newer bolts they are much smoother. This was probably done to normalize and evenly distribute the stresses on the edge of the cam pin hole. |
|
I'm just shocked (flabbergasted!) because I've been told by more than one very reputable person regarding Colt products that the cuts extending into the bolt body are biproducts of the manufacture process. I guess the question now is what purpose do they serve? I see none. Also, why would recent production bolts not have these cuts extending into the bolt body? |
