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1/22/2020 12:12:56 PM
Posted: 7/16/2008 1:54:16 AM EST
The bolt catch has broken twice on my RRA 9mm AR just below the pin that holds it in place on the lower receiver. I don't understand why.

I have a Q Heavy buffer which I though was supposed to alleviate such problems. Happened with the stock buffer too.

I'm using C-Products 32 round mags and Speer 124gr+P GDHP ammo.

Everthing else is stock.

Any ideas
Link Posted: 7/16/2008 1:23:54 PM EST
[Last Edit: 7/16/2008 1:24:10 PM EST by feld-hure]
You need a small spcaer in the rear of your buffer tube. The buffer goes back too far and gathers too much momentium then slams into the bolt catch.
Link Posted: 7/17/2008 3:12:40 AM EST

Originally Posted By feld-hure:
You need a small spcaer in the rear of your buffer tube. The buffer goes back too far and gathers too much momentium then slams into the bolt catch.


Is that with a stock buffer? I'm using a Q-buffer(Slash sells them in the EE).
Link Posted: 7/17/2008 7:58:56 AM EST
If I recall correctly you want to limit bolt overtravel to no more than .125 past the bolt catch. You'll have to measure to see if you're in spec.
Link Posted: 7/17/2008 8:40:52 AM EST
You could limit the travel to .062. Mike
Link Posted: 7/17/2008 5:26:16 PM EST
[Last Edit: 7/17/2008 5:26:35 PM EST by kevins_garage]
I looked into this a long time and compared some of my lowers. I don't think it is all the fault of the buffer hitting the bolt catch. The bolt catch has some front to back movement when the buffer hits it. If you look at how the bolt catch fits into the machined groove on the side of your lower, you should be able to see where it is contacting the lower when the buffer is pushing against it, which puts pressure on it and causes it to snap right at the pin hole (it's weakest point).

You may have to relieve the slot on the side of your lower for the bolt catch so the bottom half of the bolt catch below the pin won't make contact at the back edge of the slot below the pin hole. You could also modify the bottom back edge of the bolt catch by filing it a little so it doesn't contact the lower when the bolt closes. If none of the above work, the slot may just be too wide at the top and is allowing the bolt catch to go too far forward at the top - try swapping to a different lower.

After I broke my first bolt catch, I started to check all of my lowers and found a couple that had better tolerances in this area, so I dedicated those to my 9m guns and haven't broken a bolt catch in about 4+ years. (knock on wood)

Link Posted: 7/21/2008 7:43:17 PM EST
Try playing with you buffer spring tension. I would try a wolf xp. this should help slow things down a bit. There's a lot of slamming going on with that heavy bolt.
Link Posted: 8/3/2008 7:21:56 AM EST
I found this to be the same issue I was having. I JB welded a piece of .003 thick brass stock to my bolt catch, the portion that is inside the lower receiver to take the slop out and my catch has not broken in 600 rounds.
Link Posted: 8/3/2008 7:58:04 AM EST

Originally Posted By kevins_garage:
I looked into this a long time and compared some of my lowers. I don't think it is all the fault of the buffer hitting the bolt catch. The bolt catch has some front to back movement when the buffer hits it. If you look at how the bolt catch fits into the machined groove on the side of your lower, you should be able to see where it is contacting the lower when the buffer is pushing against it, which puts pressure on it and causes it to snap right at the pin hole (it's weakest point).

You may have to relieve the slot on the side of your lower for the bolt catch so the bottom half of the bolt catch below the pin won't make contact at the back edge of the slot below the pin hole. You could also modify the bottom back edge of the bolt catch by filing it a little so it doesn't contact the lower when the bolt closes. If none of the above work, the slot may just be too wide at the top and is allowing the bolt catch to go too far forward at the top - try swapping to a different lower.

After I broke my first bolt catch, I started to check all of my lowers and found a couple that had better tolerances in this area, so I dedicated those to my 9m guns and haven't broken a bolt catch in about 4+ years. (knock on wood)



I never thought of that. I have yet to break a bolt catch. I have always made sure my all my lowers were of the best in spec quality and have always put my own rifles together, I've never bought a complete AR. I have seen many lowers out of spec in a lot of areas.

The 9mm catch is more breakable, the Slash Q buffer does lighten the hit. Spacers are not very effeciant and if you go too far you will start missing the catch on the last round.
Link Posted: 8/3/2008 9:27:16 AM EST
I put about $1.75 in US quarters in my buffer tube behind the spring to limit the rear travel of the buffer. This works perfectly and is a really cheap fix. I heard about it here on this site a few months ago.
Link Posted: 9/10/2008 3:54:33 PM EST
ar15barrels sells a buffer tube spacer fix.



i'm trying to find the procedure to figure out if you're getting bolt overtravel.
Link Posted: 9/10/2008 4:01:56 PM EST
[Last Edit: 9/10/2008 4:03:27 PM EST by AC12]

Originally Posted By trinydex:

i'm trying to find the procedure to figure out if you're getting bolt overtravel.


Pull back the bolt. Look inside to see how far back past the bolt catch the bolt goes.

That spacer looks like a good option.
Link Posted: 9/10/2008 6:46:05 PM EST
Why not just run a heaver buffer?

Mike
Link Posted: 9/11/2008 11:12:28 AM EST
[Last Edit: 9/11/2008 11:19:14 AM EST by jdgray]
My catch broke a few weeks ago, and only after using hotter ammo. I can tell you, my bolt goes way back, passed the bolt catch. Over an inch. I tried the quarters, and maybe it's a coincident, but I started getting extracted empties, jamed lenghtways in my bolt. Not stovepipes. I adjusted my extractor closer to the bolt, and gonna give it another go. I'd hate to spring for a Q-Buffer, just to get another broke bolt catch.
Link Posted: 9/11/2008 2:11:21 PM EST
[Last Edit: 9/11/2008 2:11:51 PM EST by Azrael2004]
Here's my quick fix....

www.ar15.com/forums/topic.html?b=3&f=15&t=384829

800 more flawless rounds down the pipe since then.
Link Posted: 9/11/2008 3:19:55 PM EST
I think I have a piece of Delron around here somewhere from a project long ago. If I can find it I could try turning a "spacer" like the one pictured. (Pic originally posted by trinydex above)

Link Posted: 9/11/2008 3:33:53 PM EST
Quarters are an option too. Just slip enough quarters into the buffer tube to keep the bolt from going back too far, and it won't have any real inertia when it bumps into the bolt catch. I'm looking at this myself, because I don't want to have a breakage at the range-it's embarrassing.
Link Posted: 9/11/2008 5:22:45 PM EST

Originally Posted By acidman:
I put about $1.75 in US quarters in my buffer tube behind the spring to limit the rear travel of the buffer. This works perfectly and is a really cheap fix. I heard about it here on this site a few months ago.


Is there a need for something metal, or do you think any spacer material would work? I was thinking about making one from a Nylon plug of some kind.

Never heard of this spacer thing before, but it sounds like it would work.

Link Posted: 9/11/2008 5:55:12 PM EST

Originally Posted By Azrael2004:
Here's my quick fix....

www.ar15.com/forums/topic.html?b=3&f=15&t=384829

800 more flawless rounds down the pipe since then.


So you used about 1" (2x.5) of total spacer... is that correct?

What's the 3/8 measurement on the bag?

Thanks
Link Posted: 9/12/2008 12:29:21 AM EST
I like the spacer idea, the kind that goes inside the spring. That way you dont add more spring rate to the buffer moving forward. I forgot to mention that I relieved the back of the new catch, where it contacts inside by the plunger, so it had some clearance with the mag follower pushing up on it. Gun ran perfect last night, no more jams, with the milder ammo.
Link Posted: 9/12/2008 1:40:47 AM EST
I bought one of the RRA nylon/plastic spacers for the full length stock and after I found the overtravel measurement, I trimmed the spacer to fit. I haven't had a problem in thousands of rounds. (I probably went through 5 bolt catches before this fix.).

RRA 9mm parts
Link Posted: 9/12/2008 4:50:34 AM EST
I wonder why RRA does not install them in the 9MM's they build. Hmmm....
Link Posted: 9/12/2008 9:34:18 AM EST

Originally Posted By jdgray:
I like the spacer idea, the kind that goes inside the spring. That way you dont add more spring rate to the buffer moving forward.


Adding quarters or any solid spacer into the buffer tube will only change the amount of "preload" placed on the spring. It will not alter the "rate" of the spring.

Spring rate is typically determined by the diameter of material used and the number of coils. To change the "rate" of an existing spring, one would need to do something like cut a coil/s off of it or heat it to alter/collapse one or more coils.

Link Posted: 9/12/2008 9:58:53 AM EST
height=8
Originally Posted By kevins_garage:
height=8
Originally Posted By jdgray:
I like the spacer idea, the kind that goes inside the spring. That way you dont add more spring rate to the buffer moving forward.


Adding quarters or any solid spacer into the buffer tube will only change the amount of "preload" placed on the spring. It will not alter the "rate" of the spring.

Spring rate is typically determined by the diameter of material used and the number of coils. To change the "rate" of an existing spring, one would need to do something like cut a coil/s off of it or heat it to alter/collapse one or more coils.



I'm thinking the extra preload is what caused my jams, may have used the wrong terminology As long as Rock Rivers buying, I'll just wait for another catch to break. So your basicly saying that adding quarters behind the spring, wont change the force of the bolt moving back into battery?
Link Posted: 9/12/2008 11:01:00 AM EST
[Last Edit: 9/12/2008 11:03:20 AM EST by AC12]
I am no expert, but if the bolt travels an inch past the stop, it has an inch to gain momentum and speed before it hits the catch. If it only travels an eighth of an inch past, it can't possibly get up speed or momentum like it did with an inch plus travel. I am going to turn a couple of "spacers" like the one pictured above for JDGray and myself. We will see how it works. I like the idea of the captured spacer vs the RRA one which could float around in the spring.

I did not see the spacer pictured on the "ar15barrels" site. Maybe I missed it.
Link Posted: 9/12/2008 11:16:08 AM EST

Originally Posted By AC12:
I am no expert, but if the bolt travels an inch past the stop, it has an inch to gain momentum and speed before it hits the catch. If it only travels an eighth of an inch past, it can't possibly get up speed or momentum like it did with an inch plus travel. I am going to turn a couple of "spacers" like the one pictured above for JDGray and myself. We will see how it works. I like the idea of the captured spacer vs the RRA one which could float around in the spring.
I did not see the spacer pictured on the "ar15barrels" site. Maybe I missed it.


Does the RRA spacer actually float inside the spring, or go between the spring and the back of the buffer tube like the quarters fix?
Link Posted: 9/12/2008 12:34:38 PM EST
[Last Edit: 9/12/2008 3:10:49 PM EST by AC12]
Well, I may have misspoke. I don't have one and assumed (OMG) The more I look at it, the more it may be full diameter. I think the spacer in the pic above is a better solution because it will not cause any preload or jamming the spring in a smaller length of space when cycled back. I found some Delrin, or maybe it's Nylon stock, but it is 2" in diameter. I am going to get a 1" diameter piece to turn a spacer from.. I may also go with a bit heavier ST-X. My cases from it are more sooted than those exact loads fired in other firearms with locked breech actions. It could stand to eject a bit slower.

UPDATE

I got to thinking about it and as long as the buffer is there you don't have to worry about spring binding. I did not think that through earlier.

I ordered a piece of Nylon 1" round stock one foot long. It should be here Wednesday. I found a piece of aluminum in the shed, and even though it was not solid and would not work, I decided to turn a prototype Spacer to get some measurements.

It will fit tight on the spring just like the first 1/4 inch of the buffer, and will give 1/2" of "preload" which I decided might be a good thing.

It is .750 long with the fat part at .985 X .500, and the narrow part at .780 X .250. This gave me right at 1/8" (+ or -) travel past the bolt stop.

Now I am ready to go when the Nylon bar stock comes in.


Link Posted: 9/13/2008 5:55:14 AM EST
$1.75 in US quarters is the quickest, cheapest, and easiest way to prevent bolt overtravel. You can fix this problem in about 1 minute using readily available change floating around in your pocket.
Link Posted: 9/17/2008 2:51:49 PM EST
[Last Edit: 9/18/2008 5:08:22 PM EST by AC12]
I picked up the Nylon bar from Grainger today.



First cut off of it



Second turn - .980



Almost finished - Yea, I forgot to get an in between pic. Nylon is a booger.



With the spring and buffer and installed in the spring with buffer




I tried it in my RRA, and it gives around .100 overtravel. (.780 O.A.L. - .880 would barely let the bolt catch) Now all that is left is to go shoot with it. I am sending this one to JDGray as promised. I'll turn another later. Maybe tomorrow, maybe Saturday.
Link Posted: 9/17/2008 3:17:35 PM EST
[Last Edit: 9/17/2008 3:23:53 PM EST by RevMetric]

Originally Posted By AC12:
I picked up the Nylon bar from Grainger today.

i183.photobucket.com/albums/x37/Walkalong/NylonBar-Before.jpg

First cut off of it

i183.photobucket.com/albums/x37/Walkalong/NylonBar-FirstTurn.jpg

Second turn - .980

i183.photobucket.com/albums/x37/Walkalong/NylonBar-SecondTurn-980.jpg

Almost finished - Yea, I forgot to get an in between pic. Nylon is a booger.

i183.photobucket.com/albums/x37/Walkalong/SpacerAlmostFinished.jpg

With the spring and buffer and installed in the spring with buffer

i183.photobucket.com/albums/x37/Walkalong/SpacerBySpringAndBuffer.jpg
i183.photobucket.com/albums/x37/Walkalong/SpacerInstalledInSpringWithBuffer.jpg

I tried it in my RRA, and it gives around .060ish overtravel. Now all that is left is to go shoot with it. I am sending this one to JDGray as promised. I'll turn another later. Maybe tomorrow, maybe Saturday.


Thanks for the detailed pictures. If you decide to turn a few more, let us know how much $ ?
Link Posted: 9/17/2008 4:04:14 PM EST
Thanks AC, I'll test er out
Link Posted: 9/21/2008 4:03:48 PM EST
I tried the Spacer out today in my RRA9MM AR. It ran flawlessly, as it did without it. This should stop bolt catches from breaking. We will see.

How about yours JD?
Link Posted: 9/21/2008 4:47:23 PM EST

Originally Posted By AC12:
Well, I may have misspoke. I don't have one and assumed (OMG) The more I look at it, the more it may be full diameter. I think the spacer in the pic above is a better solution because it will not cause any preload or jamming the spring in a smaller length of space when cycled back. I found some Delrin, or maybe it's Nylon stock, but it is 2" in diameter. I am going to get a 1" diameter piece to turn a spacer from.. I may also go with a bit heavier ST-X. My cases from it are more sooted than those exact loads fired in other firearms with locked breech actions. It could stand to eject a bit slower.

UPDATE

I got to thinking about it and as long as the buffer is there you don't have to worry about spring binding. I did not think that through earlier.

I ordered a piece of Nylon 1" round stock one foot long. It should be here Wednesday. I found a piece of aluminum in the shed, and even though it was not solid and would not work, I decided to turn a prototype Spacer to get some measurements.

It will fit tight on the spring just like the first 1/4 inch of the buffer, and will give 1/2" of "preload" which I decided might be a good thing.

It is .750 long with the fat part at .985 X .500, and the narrow part at .780 X .250. This gave me right at 1/8" (+ or -) travel past the bolt stop.

Now I am ready to go when the Nylon bar stock comes in.

i183.photobucket.com/albums/x37/Walkalong/229MMSpacerPrototypePic1.jpg
i183.photobucket.com/albums/x37/Walkalong/239MMSpacerProtoypePic2.jpg


I found an extra A2 stock spacer I had laying around and noticed it's dimensions are:

.750 long with the fat part at 1" X .500, and the narrow part at .750 X .250.

If you could shave .15 off the outside diameter somehow, you would have a workable spacer.

Link Posted: 9/21/2008 5:25:12 PM EST
[Last Edit: 9/21/2008 5:30:00 PM EST by Azrael2004]

Originally Posted By RevMetric:

Originally Posted By Azrael2004:
Here's my quick fix....

www.ar15.com/forums/topic.html?b=3&f=15&t=384829

800 more flawless rounds down the pipe since then.


So you used about 1" (2x.5) of total spacer... is that correct?

What's the 3/8 measurement on the bag?

Thanks


Sorry, I just saw your post. The 3/8 is the thickness of the spacer. 1/2" was the ID.
Looks like some folks did what I was originally thinking, but sadly I don't have a lathe.

This is still working, but it has left a bit of indent on the plastic tailpiece of my buffer.
It's purely cosmetic, but it is a bit ugly after 800 rounds.
Link Posted: 9/24/2008 4:55:03 PM EST

Originally Posted By acidman:
$1.75 in US quarters is the quickest, cheapest, and easiest way to prevent bolt overtravel. You can fix this problem in about 1 minute using readily available change floating around in your pocket.

+1 Had A RRA 9mm that broke them often and tried $1.25 in quarters in the buffer tube, haven't broken one since.
Link Posted: 9/24/2008 5:18:45 PM EST

Originally Posted By bestiller:

Originally Posted By acidman:
$1.75 in US quarters is the quickest, cheapest, and easiest way to prevent bolt overtravel. You can fix this problem in about 1 minute using readily available change floating around in your pocket.

+1 Had A RRA 9mm that broke them often and tried $1.25 in quarters in the buffer tube, haven't broken one since.


Ok... looks like I'll split the difference and try a $1.50
Link Posted: 9/25/2008 6:30:59 AM EST
I, too, have $1.75 in my buffer tube. Only problem, though, is that it now won't operate with 115 grain ammo, with or w/o a suppressor. 147 grain ammo works half the time w/o the suppressor and 100% flawless with it. Also, the barrel is 5" so I guess that may effect it.

Also, have you guys been noting if you have a milspec or commercial stock with a milspec or commercial spring? I had always thought all the springs were the same until I took the spring from my non-functioning 9mm and compared to one straight from colt. The colt one came with a colt 9mm buffer and was easily 3-4 coils shorter than the spring I have been using. I had a longer spring jammed into a milspec tube, which I guess made it too hard to cycle. Once I swapped the shorter spring into the milspec tube it worked well, but mangled bolt catches. That's when I added the quarters.
Link Posted: 9/25/2008 6:37:42 AM EST
[Last Edit: 9/25/2008 6:38:10 AM EST by RevMetric]
Is there any additional buffer tube / spring noise when you quarters? Not that it really matters. I was just curious.
Link Posted: 9/25/2008 7:38:33 AM EST

Originally Posted By RevMetric:
Is there any additional buffer tube / spring noise when you quarters? Not that it really matters. I was just curious.


If there is, it isn't noticeable.
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