View Full Version : Extra Hole In Striped Lower
OldNavyGuy
06-25-09, 08:37
i recently bought a striped lower that had an extra hole in the lower next to the threaded hole for installing the pistol grip.., what is it for ?
thank you.
i recently bought a striped lower that had an extra hole in the lower next to the threaded hole for installing the pistol grip.., what is it for ?
thank you.
Does the rear take down pin detent go in there?
Failure2Stop
06-25-09, 08:47
I assume that the stripped lower is a SunDevil.
It sounds like a tensioning screw used to eliminate the dreaded wiggle between the upper and lower. Performs the same function as an AccuWedge by pressing up into the rear takedown lug. Necessity is definately questionable but is not as likely to cause FCG issues as the wedge.
That sounds more like a trigger pre-travel adjustment screw similar to those used on Defensive Edge ("Sully") and Territorial Gunsmiths SLR15 lowers (https://www.m4carbine.net/showthread.php?t=26420).
Failure2Stop
06-25-09, 14:21
Yup, it could be one of the pre-travel screws as well.
Is the threaded hole in question in front of the grip screw, toward the trigger angled toward the FCG at about a 45 degree angle, or behind it, near the grip radius pointing straight up toward the take-down hole?
i recently bought a striped lower that had an extra hole in the lower next to the threaded hole for installing the pistol grip.., what is it for ?
thank you.
Since you did not state the extra hole is threaded, is there a possibility it is the hole that the safety lever detent and spring goes into??? Looking from the rear of the stripped receiver, it would be to the right of the grip mounting lug.
:rolleyes:
Rather than making everyone guess wtf you're talking about. Howz about posting a picture or a more detailed description, such as position, lower brand, measurements/location of said hole, something to go on besides the nebulous scraps you've given us so far...
Since you did not state the extra hole is threaded, is there a possibility it is the hole that the safety lever detent and spring goes into??? Looking from the rear of the stripped receiver, it would be to the right of the grip mounting lug.
Tactical Innovations lowers have the extra hole for the tensioning screw that is threaded from the top only (appearing unthreaded from the bottom). Could be that.
Could it be an air pocket from a poor casting? What about a place to store extra ammo? I know, I know, it's an extra hole!
Do you have a picture perhaps?
OldNavyGuy
07-01-09, 09:36
:rolleyes:
Rather than making everyone guess wtf you're talking about. Howz about posting a picture or a more detailed description, such as position, lower brand, measurements/location of said hole, something to go on besides the nebulous scraps you've given us so far...
geeeeze...., why so hostile ?
OldNavyGuy
07-01-09, 09:38
+1 for picture request.
sorry there sir, but i do NOT have photo posting connections, i could take a photo but how to post it ???
sorry there sir, but i do NOT have photo posting connections, i could take a photo but how to post it ???
You do not have to host the pic, you can simply attach it to a post.
C4
OldNavyGuy
07-01-09, 09:52
Yup, it could be one of the pre-travel screws as well.
Is the threaded hole in question in front of the grip screw, (no, it is to the very rear end of the P. grip threaded hole, it is vertical and does appear to be an upper tensioning screw that as mentioned prior a replacement for the "Accu-Wedge") toward the trigger angled toward the FCG at about a 45 degree angle, or behind it, near the grip radius pointing straight up (that is it !!) toward the take-down hole?
the stripped lower is from LWD and is very well finished, it also has the "nubbs on the front of the mag well."
CleverNickname
07-01-09, 17:34
I imagine it looks something like this:
http://img33.imageshack.us/img33/5688/tensionscrewdetail.jpg
When I first saw the thread title, I thought I might see something more like this:
http://img9.imageshack.us/img9/4484/groupm16a1strippedleft.jpg
OldNavyGuy
07-02-09, 08:37
I imagine it looks something like this:
http://img33.imageshack.us/img33/5688/tensionscrewdetail.jpg
When I first saw the thread title, I thought I might see something more like this:
http://img9.imageshack.us/img9/4484/groupm16a1strippedleft.jpg
thank you sir.., for the photos, that is exactly what mine look like.
when i looked it in my lower, my first thought was could that set screw be drilled out a small high tension spring and a nylon plunger be installed.., always looking for ways to improve on someone else's design
My Firebird Precision lowers have both trigger pre-travel and upper tensioning screw holes. If you over-tighten that tensioning screw it is a bitch to push out the take down pin, but it does eliminate the small bit of play between the upper and lower.
OldNavyGuy
07-03-09, 08:47
Snappy, i hope this is not too dumb, but how are these "tensioning" screws accessed ? does the P.grip have to be removed when adjusting ? will the "trigger pre-travel" set screw work on a standard AR-15/M4 weapon ? i ask this because one of my favorite M4 type rifle has an exceptionally long and "scratchy/bumpy" trigger pull, i just may pull it out, put it on my trigger/hammer block and stone it with a hard Arkansas stone till it is at least smoothe.
how are these "tensioning" screws accessed ? does the P.grip have to be removed when adjusting ? will the "trigger pre-travel" set screw work on a standard AR-15/M4 weapon ? i ask this because one of my favorite M4 type rifle has an exceptionally long and "scratchy/bumpy" trigger pull, i just may pull it out, put it on my trigger/hammer block and stone it with a hard Arkansas stone till it is at least smoothe.
The P-grip does have to be removed to access the trigger pre-travel screw. It is the hole closest to the trigger guard "ears" in the photo of my stripped Firebird lower. Notice that the upper-tensioning screw, (the hole closest to the receiver extension tube), is in a completely different place than the one pictured earlier in this thread.
The second photo shows both a stripped lower with the upper-tensioning screw accessible behind a stock Stag lpk grip, and a complete lower with the upper-tensioning screw covered, (made inaccessible), by an Ergo grip. A small drilled hole in the Ergo grip would fix that. I just got a Magpul Miad and the modular backstraps, if left unpinned, can be slid down to access that screw without removing the grip.
The trigger pre-travel screw works fine with my 2 fire control groups, a Geissele SSA and a stock Stag. I'd bet that some conservative stone work to smooth your hammer and sear surfaces, (be careful here!), and some pre-travel tuning would make your favorite M4 feel better. Hope this answers your questions and is helpful somehow.
OldNavyGuy
07-05-09, 09:25
I'd bet that some conservative stone work to smooth your hammer and sear surfaces, (be careful here!), and some pre-travel tuning would make your favorite M4 feel better. Hope this answers your questions and is helpful somehow.
my friend, you have helped immensely, this photo https://www.m4carbine.net/attachment.php?attachmentid=2739&d=1246780509 of the lower clarifies the positions of the holes i had questions about, i just took some photos of my lower, but for some reason (not familiar with system ??) i can not get them to the forum, the rear most screw hole has a set screw in it and has a green plastic/nylon insert, i am fairly certain it is the upper tensioning screw, can you please describe how the trigger pre-travel screw functions ?
thank you sir for your very informative photos.
Yup, it could be one of the pre-travel screws as well.
Is the threaded hole in question in front of the grip screw, toward the trigger angled toward the FCG at about a 45 degree angle, or behind it, near the grip radius pointing straight up toward the take-down hole?
I think you nailed it with your reply.
Can anyone provide the size of the set screw typically used in CY6 and Territorial lowers used for the pre-travel setup?
Thanks
can you please describe how the trigger pre-travel screw functions ?
First off, nice job resizing the pic that I tried to post. Couldn't figure out how to make it show up in the post other than as a link.
Secondly, I am no expert at gun smithing and will attempt to pass along my limited experiences here, but certainly welcome any correction or advice from the forum members et al. Please take this info as amateur advice and research as much as you can so that you can avoid any dangerous conditions that can come from messing with hammer/sear engagement angles etc.
As you tighten, (screw in), the trig pre trav screw it starts to press up on the underside of the trigger, (the horizontal part up inside of the lower, not the part you actually touch with your finger to shoot), causing it to pivot forward on the trigger pin. As you tighten the screw you can see the trigger slowly moving back as the distance needed to pull it to break or release the hammer lessens, (this distance is the pre travel and is what you are adjusting). Essentially you are creating a shorter more efficient trigger pull by taking up the slack before the point where the trigger releases the hammer and fires. If you go too far the hammer will not reset/engage as it should and you'll need to loosen the screw to allow this to happen. CAUTION: You need to test this engagement by pulling and holding the trigger in as you cock back the hammer manually. As you let out on the trigger it should "click" into engagement with the hammer holding it back, as would happen when you fire your weapon in semi auto mode and the bolt goes back and forth readying you to fire again with another pull of the trigger. If the hammer doesn't stay back it will follow the bolt forward thus firing the next round without you pulling the trigger again. Your weapon could end up in full auto fire without you having the ability to release the trigger to stop it, which is seriously dangerous and seriously illegal in most places. I turned the pre-trav screw until reaching the point of not engaging the hammer and then backed it off by about a 1/2 turn and tested it thoroughly. Push down repeatedly on the hammer face once it is engaged to ensure that it won't disengage without the trigger being pulled. I was able to adjust/lessen pre-trav in both lowers without adversely affecting hammer engagement. This is long winded and, again, amateur so I welcome any correction or clarification from the forum. If it doesn't make sense please refer to more professional resources before messing with your trigger to be on the safe side. Hope this is helpful somehow.
OldNavyGuy
07-07-09, 10:09
Hope this is helpful somehow.
it most definitely was and thank you very much :D
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