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2/13/2008 6:57:51 AM EDT
I'm wondering if there is a difference in height with a OEM Colt bolt catch, vs the standard .223 catch ? I'd like to be able to manually lock the bolt open with a VM Hy-Tech 9mm Uzi magazine adaptor . Would swapping bolt catches allow this to work, or is my only choice to use a chamber flag when the line is clear ?
TIA,
DanG
EDIT: 2/15> I compared this lower to another, and this bolt catch does not rise as much, about 1/16" less travel.My other lower held the 9mm bolt back with no problem. I'll remove, compare, and either repair, or replace the bolt cath/plunger/spring.
Thanks for the answers guys.
DanG
2/13/2008 11:02:19 AM EDT
[#1]
I can manually lock my RRA 9mm bolt back whether I have a standard .223 bolt catch or the extended 9mm bolt catch.

I would think you should be able to lock your 9mm bolt back with the standard .223 bolt catch also, unless something is restricting it's movement.
2/13/2008 11:36:47 AM EDT
[#2]
I just double checked it, and if I really push hard  on the bottom of the bolt catch ( to engage it), it JUST catches the bolt. If the rifle is bumped, the bolt easily jumps forward. Now I wonder if my bolt catch is just out of spec( too low?).
Anyone else have any experience with this ?
DanG
2/13/2008 8:16:40 PM EDT
[#3]
You can remove the catch and file a small amount off  the bottom of the part you are pushing, (So it will go slightly higher) or try a different catch from another maker.  
2/13/2008 11:26:36 PM EDT
[#4]

Quoted:
I just double checked it, and if I really push hard  on the bottom of the bolt catch ( to engage it), it JUST catches the bolt. If the rifle is bumped, the bolt easily jumps forward. Now I wonder if my bolt catch is just out of spec( too low?).

That doesn't sound right.  Does it do this with a 5.56 upper on the receiver?  

I have a Hy-Tech block in my 9mm, but it has no bearing on the function of the bolt catch.  It works the same with any upper / bolt carrier combo, and as I said, the Hy-Tech block makes no difference.
2/14/2008 4:54:33 AM EDT
[#5]
It does work correctly with a 5.56 upper installed. I'll bring the 9mm home tonight, so I can compare/mount it to another lower.It appears that the catch is not moving as much as it should...
Details to follow.
DanG
2/14/2008 5:35:24 AM EDT
[#6]
The lugs on the gas gun bolt extend farther out and have more bearing surface on the face of the catch.

The COLT pattern 9mm bolt does not have the extra material radiating out, so the contact is minimal.

Might be that the 9mm catch has more surface area, I have seen a "9mm" bolt catch to know if face is same height as it gas gun counter part, other than the longer finger on the 9mm part.
2/21/2008 2:58:18 PM EDT
[#7]
I had the same problem with my RRA 9mm. The bolt would lock open after the last round was fired about half the time.  Even when it did lock open, or if you pressed the bottom nub on the hold-open lever, the engagement on the face of the bolt was so minimal that a slight bump would cause the bolt to slam closed. It was alarming because even inserting a loaded mag would be enough to cause the hold-open to slip, chambering a live round.

I used a diamond stone to remove a small amount of steel on the inside of the hold-open lever where it contacts the lower when depressed. This is the area where the spring detent pushes against the lever, holding in the downward position.

This was enough to allow the hold-open to engage fully. However I found that the magazine still lacked enough travel to press the hold-open lever up fully. I fixed this problem by shaving a small amount of the follower off where it contacts the left feed lip. Just look for the area of contact that stops the upward travel of the follower. By scrapping it a little or filing it down a bit, it will allow the stop on the back of the follower to apply more pressure on the hold-open.

This explanation may seem complicated, but once you figure it out, the repair is pretty simple.

Good Luck!
2/21/2008 5:12:30 PM EDT
[#8]
I ran into the same problem with the Hahn dedicated block and a 9mm RRA upper.  The block's BHO had more room to travel but it was limited by the bolt catch on the lower.  A dremmel job to remove excess metal and now it reliably engages the bolt and doesn't release without a good slap.  LPK was DPMS if that helps any.  Good luck!
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