saltydecimator 482 Posted July 7, 2015 Report Share Posted July 7, 2015 Quote Link to post Share on other sites
blkgunlvr 31 Posted July 7, 2015 Report Share Posted July 7, 2015 Surface area for bolt carrier cooling? Quote Link to post Share on other sites
HB of CJ 1,263 Posted July 7, 2015 Report Share Posted July 7, 2015 I do not understand nor comprehend. Just dummy me. Pictures? HB Quote Link to post Share on other sites
saltydecimator 482 Posted July 7, 2015 Author Report Share Posted July 7, 2015 Underside of carrier. Either side of where the hammer interfaces to re-cock Quote Link to post Share on other sites
HB of CJ 1,263 Posted July 7, 2015 Report Share Posted July 7, 2015 M16 profile? Can you see the firing pin within the BCG looking up through the mag well? If you can not, then it has the M16 profile. I think it may be crud, dirt, muck, mud or excessive lube/gas escape routes, but I am still not tracking here. I dunno yet. Sorry. HB Quote Link to post Share on other sites
saltydecimator 482 Posted July 7, 2015 Author Report Share Posted July 7, 2015 Perpendicular to the yellow lines I like the lack of fouling or for blow by etc likeyiubsay, as a reason. So where do I go to get shallower cut carriers Quote Link to post Share on other sites
forsaken352 235 Posted July 7, 2015 Report Share Posted July 7, 2015 I do not understand nor comprehend. Just dummy me. Pictures? HB I believe this is what he means: 1 Quote Link to post Share on other sites
saltydecimator 482 Posted July 7, 2015 Author Report Share Posted July 7, 2015 Exactly right thank you. What I am going by is I have a 300 ossm upper (that I am trying to sell btw) that is diff than 556 carriers in the way I mentioned. The rim on the 300 ossm is the same as the 410 shotgun shell, wink wink hint hint Quote Link to post Share on other sites
HB of CJ 1,263 Posted July 7, 2015 Report Share Posted July 7, 2015 Now I understand. Sorry, bad day here. Same answer. Muck channels? I really do not know. Good question. HB Quote Link to post Share on other sites
forsaken352 235 Posted July 7, 2015 Report Share Posted July 7, 2015 So what determines how or why those cuts are on either side of hammer ramp? Lookin at you old coot How deep they are that is. Mainly cause I wNt a fatter dia bolt It's difficult to get a good read on it because the channel is not perfectly flat, but my calipers measure ~.200" from the flat area the hammer rides to the bottom of the channel on my 5.56 carrier. However, measuring the thickness between the bottom of the channel to the wall closest to the channel which the bolt rides in, I'm reading ~.030". The reason for them being there is unknown to me. Hope this helps. Let me know if you need pictures of what I'm trying to describe and I'll see what I can do. Quote Link to post Share on other sites
YOT 3,743 Posted July 7, 2015 Report Share Posted July 7, 2015 Twinkie holders. Like stated, I'm certain they are "muck channels". I would also think the depth/width would depend on the tooling tolerances of the manufacturer. Quote Link to post Share on other sites
ChileRelleno 7,071 Posted July 7, 2015 Report Share Posted July 7, 2015 (edited) This is how I understand it. Those grooves separate the Lands* from the hammer ramp & contact surface. If those grooves were not there the lands would not ride properly within the bottom of the receiver and the BCG would not be aligned properly. *Lands are the flat ridges on the outside of the grooves, and the are two more to either side of the gas key.) About the exterior of the bolt carrier are a series of usually four (4) lands and usually accompanying grooves which extend from the forward end of the bolt carrier (as it is mounted in the firearm) rearwardly for a distance of about one-half the length of the bolt carrier. A land can be defined as a raised portion on the exterior of the bolt carrier which contacts the interior surface of the upper receiver of the firearm. Such lands are generally equally spaced from one another about the exterior of the bolt carrier and are generally parallel to each other. The exterior surface of the lands make contact with the interior surface of the upper receiver of the firearm and serve to align the bolt carrier within the receiver. Edited July 7, 2015 by ChileRelleno Quote Link to post Share on other sites
Capt Nemo 882 Posted July 8, 2015 Report Share Posted July 8, 2015 I believe that they give clearance for the magazine feed lips when the bolt is closed. 3 Quote Link to post Share on other sites
forsaken352 235 Posted July 8, 2015 Report Share Posted July 8, 2015 I believe that they give clearance for the magazine feed lips when the bolt is closed. You are onto something there. I just took my carrier out, unloaded a mag, and fit the feed lips into the channels. Near perfect fit. 1 Quote Link to post Share on other sites
saltydecimator 482 Posted July 8, 2015 Author Report Share Posted July 8, 2015 prob a combination of everything, like has been suggested... ya, cuts maybe so the bullets can ride higher in mag, or ride higher into path of bolt that is, for feeding...on the single stacks its not the same so you dont cut as deep....maaaaaaybe? i will post pics in a bit of my 300 OSSM carrier compared to a 556 carrier 1 Quote Link to post Share on other sites
saltydecimator 482 Posted July 9, 2015 Author Report Share Posted July 9, 2015 Here's top Here's showing shallower cut Profile of thicker bolt. By about .110" 1 Quote Link to post Share on other sites
HB of CJ 1,263 Posted July 21, 2015 Report Share Posted July 21, 2015 Thank you everybody. Now I grok it. Mag lip clearances. Much less on specific carriers for single stack mags. I took me awhile. Average. HB Quote Link to post Share on other sites
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