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Posted: 8/3/2011 3:10:16 PM EDT
| Anyone else find the need to shorten their selector detent spring when installing a MIAD grip? I tried installing the grip twice, both times it seemed the pressure on the detent would not allow the selector to rotate without a lot of effort. I trimmed a little off the spring and everything seems to work OK now. Is this normal or do I have an out of spec grip? |
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We created this tacked thread in our forum here to explain the relationship between the pistol grip, detent spring (more specifically, spring pressure), selector and receiver.
Even if a single company manufactured all the receivers, pistol grips, selectors and springs, there will still be some dimensional differences due to tolerance. Speaking for our own products, since everything is milled from bar stock, tool wear does take place, tools and bits have to be replaced. We generally spend between $700 to $1000 for every 1000 selectors we produce. Right before the tools and bits are replaced, the dimensions of the units produced will be slightly different than the units produced when tools and bits were fresh. Cast selectors are less precise, and we've compared lots of cast selectors, and the dimensions of the detent groove do vary. MIAD and MOE grips have shallower spring holes than A2, which means springs will stick out more, exerting more pressure. Selectors with shallower detent grooves will provide more spring tension. Deeper detent holes have slightly less. Receivers are not all created equal, the hole for the detent spring and detent can be slightly out of spec, in some cases the detent isn't allowed to poke out of the hole as much as it should be, and bottoming out. 
In the above picture, imagine the detent is bottoming out and cannot protrude further UP because the hole in the receiver isn't drilled to spec. This will result in a mushy and soft detent engagement, no matter how much spring pressure is applied to the detent. This isn't what the OP is experiencing, but the opposite. I'm using it to illustrate the result of so many different parts, made by different companies, working together but not always nicely. Hope this helps 
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Quoted:
When I installed my MIAD grip, I didn't have to trim the selector detent spring, but I had to reuse the screw and washer that came with the standard parts kit instead of the one Magpul included. Why did you have to use the original screw and washer? Did it work ok? The instructions say not to use the original, but I don't know why. |
| I had to trim my selector detent spring for it to work well with my MIAD grip, though I did not just make a wild guess how much to trim, not knowing how much the spring was being compressed. I measured the OAL, I put it in the grip and measured how much stuck out, and the same with it in the receiver with selector and detent already in, then compare the differences. It turned out that the spring was being compressed about 6-7mm, which did not even appear to be physically possible because of how tightly wound the spring is, it didn't seem like there would be enough empty space between the coils to do it. I trimmed it so it was only being compressed ~1.5-2mm instead of ~6-7mm, before, the selector was ridiculously stiff, and now it feels more like the ones on most other AR's that I've held at stores. Keep in mind that when I say how much it was compressed, I mean when it would be at rest, not when the selector is moved, which would compress the spring slightly more. |
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