Mellow greetings fellow ARFers,
I have a problem with my AR15. (Bushmaster) I've read the FAQ, the List Rules, the Sample Post and the Glossary and couldn't find this exact problem. (None mentioned a jackass with an Allen wrench and a set screw) My lower is a Bushmaster that I've owned for a number of years and perhaps I should not have been trying this idea with my Bushies since they all seem to have tight threads for the pistol grip screw.  I usually stick  to stock guns but then I found this site and now there are so many neat things to try.  I have broken down the situation below.

THE IDEA:   I was attempting to use the JARD method to reduce the trigger travel by using a 1/4 X 28 TPI X 1/2" set screw to reduce the travel of the trigger and then my plan was to use a shortened pistol grip screw to hold the grip itself on.

PROBLEM: I have a 1/4 x 28 TPI X 1/2" set screw stuck at the top of the pistol grip screw hole in my Bushmaster lower receiver.  Half, about 1/4", of the set screw is protruding out of the hole.(inside of the lower receiver.)

PREP: I checked the threads to ensure they matched.

I ran my pistol grip screw in all the way without the grip to ensure that the hole was threaded all the way through.(The tip of the Pistol Grip Screw protruded into the lower receiver)

PROCEDURE: As I began to run the set screw in, I decided it would be easier to start the set screw from inside the lower receiver and back it out so that it would be at the top of the hole.(Thus eliminating the need to run it the whole length of the threaded hole) Once again, due to my Bushmasters all having rather tight threads when running the grip screw in I figured this would eliminate some of the hassle.  I placed my Allen wrench through the bottom of the threaded grip hole and into the receiver where I placed the set screw onto the Allen wrench and then turned the Allen wrench LEFT in order to back the set screw down into the hole. It was all going fine, certainly a bit on the tight side and then I stopped about 1/4" in. (I think I took a phone call) When I came back to continue the process the set screw would not budge.  It is seized in there but good. I do not believe I cross threaded the hole.

I have completely ruined my 1/8" Allen wrench ( turned it into a swizzle stick) and then cut the wrench to pieces as I attempted and re-attempted to unscrew the set screw from the receiver.  I have a long set of Allen wrenches and had used a pair of vice grips to clamp closer to the tip in order  to shorten the length of the wrench that I was using, but in the end the set screw appears to be winning.

After numerous attempts I called my father who suggested peening the set screw with a hammer and punch in hopes of loosening the threads. I tried this but to no avail.  I'm not sure if I was too hesitant to swing the hammer hard enough do any good (I'm leery of aluminum) or if this idea is just not a solution at all.

I'm open to ideas at this point.  My thought is to get a  3/8" socket with 1/8" Allen head tip (Snap on?) and use an impact wrench.  I would assume the rapid and multiple taps should drive it back out. I'm not overly worried about stripping the threads as I do not believe the grip screw even contacts that high up into the hole.  I certainly don't want to apply heat, but might I have to? (In the end my OCD would rather that no damage would be done to the receiver)  Anybody, "Been there-done that"? Please help me as I really really love my AR and I've been told you guys are the best. (Truthfully I got the idea from the "build it yourself" forum)

Thanks in advance.

"A rookie out of his league"

Sly

(Edited to add, I'm off line after 5pm MST)

If I were faced with this situation, I would first turn the receiver on its back, and fill the grip screw hole with my favorite penetrating oil, let sit over night.

Then, I would put the receiver (you have the internals removed by now?) in a toaster oven for 30 minutes at 250 - 300 degrees.

Then I would use an AMERICAN MADE allen wrench attached to a socket, and remove the screw.

If this doesn't work, I would try a large diameter cutoff wheel and cut a screwdriver slot in the top of the screw, then try to remove with the biggest screwdriver that would fit.

If unable to get to it to slot the screw, or it is a no-go, time to break out the drill set.  Start with a 1/8 inch bit, go up one drill size at a time.  Try an easy-out during the drill routine, it should come out.  You may have to drill just about the whole screw out.

Let us know how it progresses.

First off, the grip hole on receivers is threaded from the bottom up. This means that the starting tapered section on the tap (threading tool) is all that was ever run threw the top of hole, and the reasons that you insert the set screw from the bottom up.  This allows the setscrew to bottom out on the taper section, with only little loctite needed to keep the screw from backing once set.

Since you basically tried to enlarge the taper section from the wrong side, your setscrew forced the metal/threads open and chances are that the thread pattern no longer matches the rest of the threads down the grip hole channel.  Also, since doing this created heat, you semi bonded/wedged the screw to the receiver metal. By hammering at the screw after the fact, you only worsened the problem.

To fix the problem, step one is to get a new T-handle Allen wrench, and a long standard Allen wrench that you don’t mind destroying (softening by heating).   Pad the receiver, and insert it in a leather-padded vise (just enough to hold it securely and not crush anything).  Now insert the old Allen wrench into the setscrew (free standing), and heat the end of the Allen wrench with a torch to transfer heat to the setscrew (this keeps you from burning the finish off the receiver and keep the heat directed to the set screw to allow the aluminum to loosen up).   You don’t need the setscrew to glow, just to be very warm to the touch if you are feeling the tip of the setscrew from inside the receiver.  Once you get the setscrew heated, pull the old wrench, and use the new T handle wrench to spin the setscrew forward, and out/up into the receiver.

Once you get the old screw out, lube the threads in the receiver, then chase the threads from the bottom of the hole, up threw the receiver with a new set screw.  This will align the threads that you have marred.  Also, don’t try to fully thread the setscrew out into the inside of the receiver. You only want to realign the threads and keep the top of channel tapered.

Now to set the screw correctly, clean the threads of the receiver and set screw with alcohol and allow all the treads to dry.   Then install the setscrew into the receiver (from the bottom) until the screw tip is four threads down from the top of threads/ inside of the receiver.  Apply one drop of blue loctite to the tip of the setscrew, then thread the screw up, then back down to get the loctite into the threads.   Moving quickly, install the FCG (without installing the hammer), then set the selector to safe and use a small punch to put pressure on the selector detent to keep the selector in the correct lateral position as when the FCG is installed.   Using the setscrew, bottom the trigger against the selector flat, and then back the setscrew off only enough to allow you to get the selector out of the safe position.  For the first few tries, the selector will be tight coming out of the safe position, but will loosen up, so don’t back the screw off too much or you will have to reset the screw in a very short time.  Also, a little grease on the selector/receiver hole before you install it in the receiver will allow it to move more freely, and allow you to set the setscrew tighter from the start and still allow you to get the selector out of the safe position.

Hope this helps.

ar-wrench,

I tried the oil trick but not for an over-night.  The couple hours that I did let it sit didn't help.  Of course, my Allen Wrench set is made in the US...But still they didn't hold up.  I couldn't believe how tight that sucker is in there.

Dano523,

I will follow your advise tonight. But I am going to stop after I get the set screw out.  In the end I've decided that I'll stick with a stock set up for the Bushmaster.  (I have a cast Oly lower that I may try to tweak)

I'll let you all know how it all works out in the end.

Thanks for the advise guys.

Sly
(Note to self:  Bushmasters are for work, Cast Oly is for Play...Repeat)

Hello Again,

I haven't totally lost the war with the set screw yet.  Right now we're calling it a draw.

I tried to heat the set screw but it was like handling toxic waste with an oven mitt...A good idea but it wouldn't work.  The aluminum would wick the heat away.  I sat for about an hour with a torch heating a junk allen wrench.  It just never got close to being hot.

I then purchased a Craftsman soldering iron that advertised temperatures up to 700 degrees and also replenished the allen wrenches that I had ruined up to this point.  Using the soldering iron I was able to get the set screw fairly warm and the receiver nearly hot.  All I managed to do then was ruin some more allen wrenches.  BTW, the Snap on allen wrench that I ruined held up the best of the lot.

So for now, I have taken my dremel and ground down the protruding tip of the set screw until I could fit my trigger in.  In the end I guess this was what the idea was anyway.  There is nominal take-up on the trigger pull.  It just unsettles me that the mil-spec pistol grip screw can't be re-installed with the set screw stuck in there. (I cut a grip screw down to fit the grip onto the receiver)


Sly

Sounds like you have had a real time with that little screw.

On the receiver getting hot, that is exactly what you want.  If possible having the receiver hot and the screw cold will work to your advantage.  The coefficient of thermal expansion is greater for aluminum than steel, so as the part heats up, the aluminum hole will expand more rapidly than does the diameter of the screw.  We are talking about tiny amounts of expansion, but it usually helps.

That particular size screw is very common on structural panels on large aircraft.  Some I had to remove had 52 of those suckers on one panel that was less than 2 square feet in size.  It wasn't uncommon for 12 of the screws to have to be drilled and removed with an easy-out, the trouble came when an easy-out broke off in the screw.  The easy-out is as hard or harder than a drill, so no drilling them.

I mention this if you decide to attack it again.

Glad to hear the bushy is functional again....

I-M-A-WMD,

I think that you have missed something regarding my post.  When I informed you to buy a T-handle allen wrench, it was to buy the correct size/type.  You have to remember that there are two types of allen wrenches on the market.  The first type of allen wrench is an inch pattern, the second type is metric.  Somehow I believe that you have the wrong type, and the wrench tip is just loose in the socket and spinning.

Bottom line is that if you are just chewing up the tips of the allen wrench, you have the wrong type.  On the correct type, the allen wrench should either bend (not going to happen on a snap-on tool), the shaft snaps (not on a steel setscrew to the soft metal of the receiver), of the screw should thread out.  Since your marring up tips, you have the wrong type for the setscrew that is stuck in your receiver. Also, since it sounds like you have knarred the setscrew entrance using the wrong size/type of allen wrench, you may have to tap/hammer the correct size allen wrench into the entrance socket to get it past any burs that you have created.

As for using heat, if you used loctite, then heat was needed to break the bond. But, if you didn't use any loctite, the wrench alone should thread the setscrew back out. You only needed to heat the setscrew up once to break any loctite bond, then use the wrench to spin the setscrew out. Basically, you don’t need to keep the screw hot, just enough to slightly expand the metal of the receiver.

Since the rifle is back together and running, you really don’t need to remove the screw. But, if the fact alone bothers you that the screw is still present in the receiver, you may want to get another setscrew from the same source as the last time, find the correct type of wrench, and remove the screw on your next tear down of the receiver.

Food for thought.

Thanks AR-Wrench that may come in handy in the future.  That little bugger certainly keeps nagging at the back of my mind at odd times of the day.

The easy-out may be the only option. (EDITED TO MAKE SENSE)
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Thanks Dano523,

As far as the Allen wrench goes, I heard you right.  I guess I wasn't clear on as to how I was ruining the wrenches, Twisting the entire wrench...The tips are still fine but the wrench itself is noodled. (Yes even the snap on, I guess I'm an ape) Once the Allen wrench begins to twist, in the middle of it's body, I'm just not getting any torque.

Of course, I know that there are American tools and foreign crap.  The setscrew is Standard inch and the Allen is standard inch. (Read American) I'm nearly 100% certain that I checked the threads on this set screw but their is that .00000001% the fastener store happened to get a metric in the inch box.  But as I said, I believe I checked it all out.  In fact IIRC I also ran it into my Oly receiver so I'm positive it is a standard inch set screw.

The set screw is Grade 8 steel.  I haven't damaged the setscrew entrance as far as I can tell, it looks untouched.  

I even went as far as dremeling down a 3/16 Allen wrench to fit into one of the 10 spare set screws I purchased (They were $.14 each so I bought 10.) I figured this would eliminate the twisting of the wrench, which it did, but the result was the few times that I did get the shape and size right...The tip of my Allen wrench would break clean off.  This was several hours work to get a couple good bites but no lucky strike.  (Now IIRC, I left the last tip in the socket but it should come out OK by magnet or something)

I never used loctite, but riddle me this...Wouldn't you think that if it will twist my Allen wrenches up like that trying to get the screw out..It would have twisted the Allen wrench the same fashion going in?  As your earlier post pointed out Dano523, there must have been a build up of heat which caused a bond. The whole ordeal just sucks!

Thanks again for your ideas and encouragement.  

I think I need to see the Snap-On Dealer.  What I think will work the best is a 3/8 drive socket with about a 1-1/2" long x 1/8" hex head.  This would allow me to use my extended 3/8" ratchet for good leverage, allow less length on the Allen for less chance of twisting and if it were a snap on, I'm sure the receiver will let go before the Snap-On bit craps out. (When I went to sears it was my hopes to find a 1/8" socket either in 1/4 drive or 3/8 so I could just cut sections of my Allen wrench and fit to the socket but I couldn't find a socket that small)

Will keep you posted if I can find my Snap-On dealers card.  (It's been a while since my days as a welder/fabricator and mechanic)


Sly
EDITED TO MAKE SENSE CONCERNING EZ OUT.