User Panel
Posted: 7/16/2008 2:54:16 AM EDT
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 |
|
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). |
|
|
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.
|
|
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) |
|
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.
|
|
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.
|
|
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. |
|
|
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.
|
|
|
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. |
|
|
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.
|
|
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. |
|
|
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.
|
|
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. |
|
|
So you used about 1" (2x.5) of total spacer... is that correct? What's the 3/8 measurement on the bag? Thanks |
|
|
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.
|
|
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 |
|
I wonder why RRA does not install them in the 9MM's they build. Hmmm....
|
|
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? |
||
|
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? |
|
|
$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.
|
|
Thanks for the detailed pictures. If you decide to turn a few more, let us know how much $ ? |
|
|
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? |
|
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. |
|
|
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. |
||
|
+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 |
||
|
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. |
|
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. |
|
|
Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!
You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.
AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types.
From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 1996-2024 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.