Posted: 10/15/2010 7:50:41 PM EDT
[Last Edit: Duffy][Edited]
|
We have received couple of questions regarding our selector's seemingly ease to flick out of Fire/Safe. We hold very tight tolerance on our selectors, as anyone knows, this can't always be said of other parts on the AR, especially cast or plastic parts.
The following are our initial findings re: detent spring tension, pistol grip and their effect on the perceived stiffness on the engagement/disengagement of the selector. Detent springs aren’t created equal, just the two I happened to have on hand are of slight different lengths. One of them is about 1.5 coils longer. Pistols grips (USGI, Magpul MIAD, Tango Down Battle Grip, etc.) aren’t created equal. The part we are interested in is the depth of the detent spring housing/hole. With the same spring inserted in these three (USGI, Magpul, TD Battle Grip) grips, the spring seats deeper in the USGI than Magpul MIAD and TD Battle Grip, by about 2 coils. Can spring length make a significant difference? Depends on which spring and which grip are being used. A shorter spring inside a USGI grip will yield less spring pressure on the detent, than a longer spring inside a MIAD or TD Battle grip. I was able to test and verify this. A shorter spring inside a MIAD or TD Battle Grip doesn’t feel significantly different, but without precise instrument to measure the pressure, I’d say one can hardly feel the difference. The difference of a shorter spring + grip that seats the spring deeper, and a longer spring + a grip that seats the spring just right, is noticeable when the selector is rotated out of Fire/Safe. Short spring + USGI = sloppy feel, less positive click, easy to rotate out of position Longer spring + MIAD or TD Battle Grip = more force is required to rotate out of position Pictures to come. |
Battle Arms Development
http://battlearmsdevelopment.com
http://battlearmsdevelopment.com
|
More on the perceived looseness on 0.005 percent of the receivers.
Cast selectors are not precision machined like ours, this can be a bad thing (mostly not so good, but easily overlooked) and good (just one). When a cast selector is installed, you can most likely move it side to side inside the receiver. The reason for this is the detent holes are much bigger than the detent (ours are 0.005 larger in diameter than the detent itself), there's quite a bit of slack. The side to side movement doesn't hinder the operation of the weapon. It can serve to accommodate out of spec detent/detent spring housing if it's drilled not where it's supposed to be drilled, e.g. a little bit too forward toward the muzzle, a little bit more toward the rear, a little to the left or right. Because of the slack, the detent usually has no issue seating in its general area. Our detent holes are far more precise (0.005 larger than the detent). In a receiver where the detent/detent spring hole on the receiver isn't drilled to spec, the detent may not seat squarely in the detent holes on the selector. When the detent isn't fully seated, it then can be more easily rotated out of Fire/Safe. While spring tension (length of the detent spring, the depth of the detent spring hole inside the pistol grip) can play a part, chief among the reasons our selector can feel loose has to do with the receiver. We're investigating making our selectors more compatible with this aspect of the tolerance issues on the receiver, we could make the detent holes less precise, and have more side to side movement as a result. In PIP1, we made the selector flat area diameter smaller to accommodate triggers that are not of USGI specs. In PIP2, we increased the width of this flat area to accommodate slightly out of spec receivers when a DMR trigger is in use. It's about impossible to make it fit every receiver made, and receivers that haven't even been brought to market, the tolerance issues will be with us forever. |
Battle Arms Development
http://battlearmsdevelopment.com
http://battlearmsdevelopment.com
All the major changes in our selectors have been made to accommodate other components that are either very unforgiving to out of spec receivers, or components that are not original spec.
In PIP2, we specifically widened the selector's center flat width to accommodate the use of this match trigger in slightly out of spec receivers. In out of spec receivers where the detent/detent spring hole on the receiver isn't drilled to spec, it may seat the selector off center. The trigger's rear extension then could not seat on the selector center's flat, but hitting the sides instead. This wasn't so much a problem years ago, but now with so many manufacturers making receivers, not all of them adhering to specs, this can cause all kinds of weird issues, not just with triggers and selectors. Note the gap on the right of the selector's center. We widened it as much as possible without weakening the selector's structural integrity, especially the wall next to the detent holes and groove. |
Battle Arms Development
http://battlearmsdevelopment.com
http://battlearmsdevelopment.com
|
regarding the receiver.
The receiver will not allow the detent to go through the detent hole. On my receiver, the detent protrudes about half way and is stopped. 
If your receiver's detent hole isn't drilled properly, it will stop the detent from reaching up as far as it should be allowed to, the detent bottoms out and can only go so far, where no amount of spring tension would help the mushy/spongy feel. On such receivers, a detent that's not protruding into the selector hole in enough length is enough to engage the factory selector that has a shallow detent groove. Our detent groove is deeper to prevent the selector from being backed out when rotated out of the detent holes, and this would cause the mushy feel issue. |
Battle Arms Development
http://battlearmsdevelopment.com
For LE/MIL discount, please email me at:
[email protected]
http://battlearmsdevelopment.com
For LE/MIL discount, please email me at:
[email protected]
|
Isn't it frustrating when others can't hold their specs and force you to muddy yours? ;)
I just ordered my first bad cass semi auto and an act trigger off your website for my current build. Can't wait to try it out. From the tremendous positives, I have a feeling it won't be my last. Maybe you can offer them in 2 or 3 packs? Anyways here's my question, in my past couple builds, I have tapped the detent hole and used the following: Flat point set screw 18-8 SS 1/8" long, 302 SS spring .375"long .125 O.D. .016 wire dia. And a 302 SS 1/8" ball bearing. The first one is like butter. The second one I had some issues of it becoming locked into the fire detent. I was able to grind a slightly more obtuse path from detent to groove which fixed it. Obviously I want to use a captured detent. Do you see my use of a ball bearing becoming an issue with your safety? |
Hm, I'm not sure. For one thing, the selector's detent groove and holes aren't designed to be used with a ball bearing, so you might be able to over rotate 
|
Battle Arms Development
Improvidus, Apto quod Victum
http://battlearmsdevelopment.com
For LE/MIL, and firefighter discount, please email me at:
[email protected]
Improvidus, Apto quod Victum
http://battlearmsdevelopment.com
For LE/MIL, and firefighter discount, please email me at:
[email protected]
|
The safety of a weapon is important, I'd use the parts that come with our kit or your lower. The detent is a wear item, while a ball bearing might wear much slower, it doesn't have the pointed tip that engages the unidirectional detent holes to stop it from over rotating.
We know that with sufficient pressure, even with the use of a detent, you can over rotate the safety to a position it's not supposed to. I'd imagine it'd be easier to do that with a ball bearing. |
Battle Arms Development
Improvidus, Apto quod Victum
http://battlearmsdevelopment.com
For LE/MIL, and firefighter discount, please email me at:
[email protected]
Improvidus, Apto quod Victum
http://battlearmsdevelopment.com
For LE/MIL, and firefighter discount, please email me at:
[email protected]