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9/22/2017 12:11:25 AM
Posted: 9/9/2005 12:40:56 PM EDT
I keep reading that Colt 9 mm AR's are prone to breaking the bolt catch. Is this expensive to repair, where do you buy spare bolt catches for the Colt?
Link Posted: 9/9/2005 12:49:50 PM EDT
i read this too

most have said something about the buffer or something like that being the cause of it.

but heres where everyone linked to. specialized armanent

i ran mine this past weekend without a problem, 800rds

mine has a std. ar15 boltcatch and what looks like a second piece(extension) which the follower pushes up on.
Link Posted: 9/9/2005 1:41:23 PM EDT
I feel your pain!
I've broken 4 bolt catches this summer in about 2500 rounds. The cost of a 9mm bolt catch ranges from $20 to $30 bucks!! OUCH! I just quit running them. Switched back to the .223 catch. I tried several things to fix this, no luck. It seems that the bolt on a 9mm has a lot of over travel. The 9mm round is so much shorter than the .223 and the bolt has about a 3/4'' run at the catch. It's like pounding in a nail, if you raise the hammer 1/4'' above the nail and hit it, its hard to drive it in. But if you add an inch to you develop much more energy. When the last round is fired the catch comes up. SMACK.
To remove the excess travel I tried a spacer in the buffer tube behind the action spring, the thickness of 10 quarters( perfect dia.). Then removed the same amount from the action spring with a dremel tool. I thought I had it figured out but it ran about 300 rounds and broke again. I also tried a H buffer thinking thad would reduce the mass, that catch lasted about 500 rounds. I gave up! Any suggestions welcome…

Brownells, Garrison Mfg., JT dist. all have 9mm catches. Ive tried them all.
Link Posted: 9/9/2005 1:58:39 PM EDT
There is overtravel in the 9mm bolt/carrier assembly, but it has nothing to do with the 9mm round being shorter than a .223/5.56 round. There is no separate rotating bolt in the 'blowback' 9mm system, which makes the bolt/carrier about .750 inches shorter than a comparable .223/5.56 bolt and bolt carrier combination. You can go to most hardware stores and get a 1 inch wooden dowel or pretty much any type of rod (plastic/aluminum/titanium/whatever your heart desires) as long is it will fit inside the buffer tube. You can experiment with different lengths, but I ended up settling on a little over a half inch length to shorten up the excess overtravel. I run a 9mm buffer and haven't broken a catch in a long time. All you need to do is reduce the overtravel so the 9mm bolt/carrier can just get behind the bolt catch.

Please keep in mind that the 9mm bolt catch is only needed if you are using a block that does not have an actuator to work with the 5.56 bolt catch. If you are worried about the 9mm catches, just don't use them. Hahn makes a bottom load and a dedicated top load block that can be used with the standard 5.56 bolt catches.
Link Posted: 9/9/2005 8:14:21 PM EDT
so which bolt catch is everyone talking about?

i have a colt 6450 and it has two sections

one being the std ar boltcatch and the second being the actual part that is pushed on by the follower.
Link Posted: 9/10/2005 12:38:16 PM EDT
I've got the same problem with my Oly Glock9, went thru 2 catches already, thought the MIM casting were too weak, got a Wilson bolt catch coming, cnc machined, I'll ley you know how it holds up.....love the Oly though, thats been the only problem
Link Posted: 9/10/2005 1:13:06 PM EDT
just went and put another 800 rounds through my colt making it a total of 1600 and there are no signs of breakage or cracks. (knock on wood)

which system/magblocks are having these problems?
Link Posted: 9/10/2005 4:14:45 PM EDT

Originally Posted By eklikwhoa:
just went and put another 800 rounds through my colt making it a total of 1600 and there are no signs of breakage or cracks. (knock on wood)

which system/magblocks are having these problems?

The bolt catch breakage issue is primarily with the 9mm style Colt bolt catch. But, I believe there have been one (or a few) isolated instances of broken 5.56 bolt catches when used in a 9mm Colt style set-up (these were posted about here, but they may be archived already).

Round count isn't a great way to track the potential for bolt catch breakage, because just shooting the firearm isn't doing anything to the bolt catch. What you want to be more concerned with is how many times you empty a mag and the bolt catch posp up to keep the bolt open. In other words, if you fired 1500 rounds using full 30 round mags, that is about 50 times that the bolt catch will get hit by the bolt and remain open. If you fired that same 1500 rounds, but only loaded 10 rounds per mag, your bolt catch would (or should) hold the bolt open 150 times, making it 3 times more likely to experience a failure.

The bottom load blocks (and the new dedicated top load Hahn block) that have the built-in actuator which is used in conjunction with a standard 5.56 bolt catch, absorb some of the impact of the 9mm bolt/carrier after it overtravels and reduces the likelihood of the bolt catch breaking. The standard top load Hahn block and the garrison block need the 9mm style bolt catch if you want to have last round bolt hold open. The easiest way to reduce the likelihood of bolt catch breakage with this set up is to reduce bolt/carrier overtravel, so the bolt/carrier just barely travels past the bolt catch.

The real cause of the breakage though is when the 9mm bolt/carrier overtravels after the last round is fired and then starts to come forward, it builds up enough momentum to impact the bolt catch with enough force to cause it to break prematurely. As you can see in the pivture below, the bolt catch is impacted at the top by the bolt/carrier (big red bar). The bottom of the bolt catch (below the roll pin) is actually pushed towards the back of the receiver. If there is enough "slop", the bottom of the bolt catch can hit the back of the notch it sits in in the lower, which puts pressure on it and can cause it to break below the roll pin (usually at the yellow line), causing the bottom of the bolt catch (in the purple circle) and the spring and pin beneath it to go flying. If you reduce the overtravel, you can reduce the potential for this to occur (or continue to occur) which is what is likely causing bolt catches to eventually break. Lowers with different specs in the bolt catch area can be some of the reason why some people don't have any problems and others seem to be breaking bolt catches on a monthly basis.


Hopefully someone finds the above picture helpful.
Link Posted: 9/11/2005 7:51:08 AM EDT
thanks for the picture it help with the visual for sure!

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