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Posted: 2/13/2006 2:02:01 PM EDT
Building my first (will all new parts:RRA upper, DPMS bolt group). While I understand the need for clearances, my bolt carrier clatters around pretty good at the rear end. With the carrier forced against one side the gap is .010. Then forcing it against the other side, the gap becomes .060.
So there seems to be a slop factor of .050. Seem about right? Given this guns future usage, if dirt, grime, and infrequent cleaning is the reason then I believe I could get by with a little less slop, if it were available which I doubt. I'm not a machinist or AR expert so please correct any misconceptions.


Link Posted: 2/13/2006 2:07:38 PM EDT
so you have slop in the carrier to upper reciever fitment?.... normal
Link Posted: 2/13/2006 10:28:20 PM EDT
1. You could get a tighter tolerance (smaller ID) upper such as a Les Baer
2. Get a larger diameter bolt carrier such as Baer or Young N.M.
3. or both 1 & 2 for a really nice, slop-free fit.
Link Posted: 2/14/2006 5:11:07 AM EDT
If you will notice, there are only guide rails at the front of the bolt carrier. It would be hard for the back of the bolt carrier to have guide rails that make a jump from the upper receiver to the buffer tube. Therefore the back of the bolt carrier is guided by the buffer's fit in the buffer tube. This is why the full circle bolt carriers are better.

rj
Link Posted: 2/14/2006 10:16:57 AM EDT
Full circle bolt carriers are better ..........than what? Didn't know there was a choice. Not finding any info on the differences. Please explain. This bolt carrier is a full circle as seen from the rear.
Link Posted: 2/14/2006 10:50:29 AM EDT
[Last Edit: 2/14/2006 10:50:57 AM EDT by rjay]

Originally Posted By leftyshooter:
Full circle bolt carriers are better ..........than what? Didn't know there was a choice. Not finding any info on the differences. Please explain. This bolt carrier is a full circle as seen from the rear.



Scroll down and look at the bolt carrier in this ad :

www.ar15.com/forums/topic.html?b=7&f=119&t=329076

rj
Link Posted: 2/14/2006 1:09:40 PM EDT
That carrier looks pretty much like mine. I measured the round part at 0.929.
Link Posted: 2/14/2006 2:18:53 PM EDT
sorry to say but there is a lot of bullshit here.

les baer upper? les baer carrier? full circle?


its normal and even with a lb carrier, i have a young match carrier and does the same. its all normal. dont like it? get a bolt action.
Link Posted: 2/14/2006 4:03:31 PM EDT

Originally Posted By leftyshooter:
That carrier looks pretty much like mine. I measured the round part at 0.929.



So you are saying that yours is open at the bottom rear like the one in the photo ? In other words , a 'half circle'. There are also full circle bolt carriers. The pressure the buffer spring exerts against the back of the bolt carrier is what keeps the back end of the bolt carrier square in the bore. The full cirle bolt carrier is natuarally going to be kept more square than the 1/2 circle bolt carrier. Colt made both. It is not that big a deal for a semi auto weapon. I have some of each.

The 1/2 circle bolt carriers are notorious for chewing up the face of the buffer.

rj
Link Posted: 2/14/2006 4:13:58 PM EDT
Now I get it. Thanks.
Link Posted: 2/14/2006 4:17:11 PM EDT

dont like it? get a bolt action.


chill man, I'm just trying to learn.
Link Posted: 2/14/2006 4:22:32 PM EDT

Originally Posted By leftyshooter:
Now I get it. Thanks.



You also have to remember that the magazine [ and the bullets in it ] and the hammer are pushing up on the bottom of the bolt carrier all the time. There's lots happening inside the receiver that most people don't even consider.

later
rj
Link Posted: 2/14/2006 8:01:25 PM EDT
Mr. Whoa:

Get the exact parts I have mentioned, measure their diameters, compare against the A/B/C parts, or the R.I.A "9 Million-Series" drawings and you will find that a tighter than GI fit is achievable at the carrier / upper interface.
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