Repairing a bent A-1 upper receiver
About a month ago, I bent my AR-15,A-1 upper receiver as I vised it in a receiver clamp. The bolt would no longer move freely in the chamber and could only be removed with some resistance. While many felt that it should be reamed or sanded, "A_Free_Man" suggested that I send it to him and he would try another option. He has since returned the upper and everything works fine; the bolt falls freely like it should. I would like to ask him exactly how he made the fix. Thanks for your help!!
Prebandana had posted about needing to buy an A1 upper receiver to replace a damaged one. During a rebarreling he had used an action block without the insert, which is necessary to prevent bending the receiver. He had apparently slightly bent the upper receiver, causing the bolt carrier to bind.
This is NOT an uncommon thing to happen, and can also occur from other causes. There is usually no need to discard the receiver. This can usually be repaired.
There was a discussion, some had suggested lapping in the bolt carrier (no, too much material to remove, and just unnecessary), and other fixes. I contacted him via AR15.com's mail and offered to repair it for him.
He sent it to me and I found it was not as bad as he thought. Where they usually bend is at the lower edge of the right side, at the rear of the ejection port (the weakest spot on the upper), and this is what I found here.
This is how I fixed it. Using a piece of leather to protect it, I placed the upper receiver in my bench vise, holding it by the carry handle. The receiver is positioned so as not to touch the rear sight area. Do not bind down hard on the vise, just enough to hold it steady. The bottom side of the receiver is up, and the rear of the receiver is facing you.
(Note: This repair may also be done with the barrel still on the upper receiver. If you discover the bolt carrier binding after mounting the barrel, there is no need to remove it. Just block up the end of the barrel to support it while in the vise.)
(more to follow)
Wipe the inside of the receiver and the bolt carrier dry with a clean cloth. You don't want to mask the problem with lubricant. Slide the bolt carrier into the receiver and find the place where it is binding. If you sight down along the bottom of the receiver, you can probably see the bottom edge of the receiver flex slightly as you slide the bolt carrier past the binding area. Mark the area with a pencil or light colored crayon.
I used two large combination wrenches as pry bars. (I know of no special tools for this repair.) The sizes I used were a 1" and a 15/16", but that is not critical. You could also use two very large screwdrivers. I taped the open ends with electrical tape, and also made a few wraps around the middle of the wrenches where they would contact the inside of the receiver.
The wrenches are placed with the open ends all the way down in the charging handle channel. One wrench is positioned just in front of the rear lug, the other is positioned so that the middle of the wrench contacts the receiver where the bind is... about even with the rear of the ejection port.
Be careful to not twist the receiver in the vise, just pull (equally) the two wrenches apart. The wrench by the rear lug is pulled to the right (with the rear of the receiver facing you), and the wrench at the binding area is pulled to the left.
(More to follow)
Pull the wrenches away from each other, opening the bottom of the receiver. Bend out a little at a time (it will try to spring back), trying the bolt carrier each time. As you gradually bend the receiver open and test the carrier fit, you will feel the bind become less and less, and suddenly free up. When you have it so that the bolt carrier slides freely with no bind, you are done.
After removing the receiver from the vise, you should find that the bolt carrier can slide back and forth in the receiver by gravity alone, by just tilting the receiver back and forth, with no oil.
Before proceeding with mounting the barrel, you may wish to thoroughly degrease the receiver and touch up any scraches or worn areas with Birchwood-Casey Aluminum Black. Just apply with a cotton swab. When it has darkened enough, wipe clean with a damp cloth. Allow it to dry and wipe down with an oily cloth. It won't be a perfect match if you look closely, but will improve the appearance.
Now you are ready to barrel the repaired upper receiver.
An aside... while you are at it... why not upgrade your A1 upper's sights, too? Replace the round A1 front sight post with a square A2 sight post. Replace the A1 rear sight blade with an A2 rear sight blade. The large hole is much better for fast target acquisition. Also replace the rear windage drum with the Rapidex 1/2 MOA Knob. This will give you iron sights that for all practical purposes are just as good as having an A2 upper. Zero with the small hole at 50 yards (ala Santose), then flip to the large hole for 0-200, and small hole for 200-300. This easy modification is much less expensive than replacing an A1 upper with an A2 upper.
A Free Man
HuWah...the-free-man izza brave man...a resourceful man...and an HONEST man ta boot. Thank you for sharing that Garage Magic free-man...that is just way too kool. I have to believe that prebandanna is damn glad he trusted you with the job...Bud
...Copied to archives...
A common-sense approach to gunsmithing...I like it!... [;)]
BTW: DPMS (and others) sell a 1" plastic dowel for cleaning-rod centering & protection; it's about 9" long, has a 1/4" hole through...But in a pinch, it can be used to reinforce the upper while rebarreling...If you don't want to buy the receiver block all over again...
Thanks for the tip on the plastic dowel. I'll definitely get one. By the way, when I got the fixed receiver back from "A_Free_Man", I installed the barrel without a hitch. It torqued to specs and the gas tube hole lined up perfectly. Not sure why I had so much trouble the last time. I certainly learned a lot from this experience.
Thanks for the accolades. This was neat and easy due to my experience.
You know what experience is? It means I screwed up that way already! Hah!
Yes, the insert is necessary when using an action block, but an old bolt carrier would work, too. The dowel suggested would be an excellent substitute for the original insert.