I'm new to 9mm AR's and I just picked up a Rock River 9mm. I remember reading these need some kind of spacer or something in the gun gets beat up. I remember something about using quarters(coins) for the spacer. Does my Rock River need this and if so where do they go? Here is a picture of my buffer and spring and hopefully you can tell if this is good enough or if I need a spacer too. Thanks for any help!

The gun does not "need" anything added until and unless it gives you problems.  The spacer is to reduce overtravel of the bolt, which can lead to breaking the bolt catch.  I have a factory RRA 9mm carbine without a spacer, and running WWB it is smooth and fun to shoot, with no problems that point to needing a spacer.  My 9mm SBR runs fine without a spacer OR a heavy buffer, again with WWB.

If you find the gun feels harsh when you fire it, particularly when the bolt goes forward, you might consider a spacer.  If it isn't a problem, don't worry about it.

Do they make a spacer for this problem or do you have to make your own? Where exactly does the spacer go? Thanks!

There Are plastic spacers available from a number of source; search "9mm buffer spacer" for more hits than you'll know what to do with,

It goes in the receiver extension tube, big end in, and the spring goes in onto it.  Helpful?

This is my RRA LAR-9 with the Spikes Tactical buffer spacer installed.
http://i45.tinypic.com/f515bc.jpg

You have nothing to loose and everything to gain by doing the quarter mod.

The quarters (mine took 6- 7) get dropped down the buffer tube before you put the buffer and spring in.  The idea is to slightly limit backtravel of the bolt to the point where it just clears the bolt catch when you fire the last round of the magazine.  If you don't limit the rearward travel the bolt gains momentum as it travels forward and this momentum might break the bolt catch.  I put just enough quarters to allow the bolt to go about 1/4-1/8" past the bolt catch.

So, to re-cap

quarters<<spring<<buffer

If you put too many quarters, the bolt will not even travel far enough back to clear the bolt catch when it comes up after the last round fired.  It's easy to visualize when your looking at the bolt catch through the ejection port as you cycle the gun via the charging handle.

Hope this makes it somewhat clear.

$1.75 in quarters and an RRA 9mm buffer worked great in mine.

That put the fully retracted bolt about 1/8" behind the bolt catch.

Spend the money for a Q-buffer and be done with it.  Problem solved.

I just tried to buy the Spikes spacer and it is sold out. Anyone else make one or know where to buy one? I may try the Q buffer too. The bolt hold open does not work on the Rock River unless you manually lock it open.

I have not put my 9mm upper on my lower yet, so I don't know if it will work. This little rubber stopper is from the hardware store. it's for plugging a hose connection on my dishwasher. It is 1 1/16'' at one end and tapers down to 7/8" at the other. As im looking at it i was thinking how easy it would be to whittle this down to work in place of a 9mm spacer at the bottom of my buffer tube. plus it only cost me $1.

I ran 7 quarters in my RRA 9mm upper with a RRA 9mm carbine length buffer, at the time I wasn't running a long finger bolt catch so I wasn't too worried about the overtravel, later I did upgrade to a dedicated length buffer (Spike's ST-9X, discontinued) and it smoothed out the recoil, money well spent.

I would be concerned that a cheap rubber dishwasher stopper might eventually fail and/or cause other problems.  Conventional wisdom says a solid plug/button would be the preferred option - quarters, aluminum, delrin, etc...

Would anyone be willing to measure and share the dimensions (length) of the 9mm spacer?  My lathe is idle so may as well make my own.  Thanks!

pull BCG back, measure distance from bolt face to bolt hold open, subtract 1/8", get washers to fit.

So what is the better way to smooth out the gun and save wear on it....the heavy Q buffer or the spacer option? Can you install both options?

bump for anyone what might know the above answer? Thanks!

Sure you can use both at once.  But it is a solid rule of troubleshooting to make only ONE change at a time.  Use whichever you like first and see how it works,  the only "issue" from not using a spacer is excessive bolt travel, which can cause the bolt to go forward too fast and hammer the bolt catch on an empty mag.  A heavier buffer can help the gun run more gently, but you could have issues with lighter loads.  My SBR eats up WWB 115 gr loads all day long with a standard carbine buffer and no spacer, but hotter, heavier loads may call for a heavier buffer, which I keep in my range bag.

I use at rifle length spring and a Spike's 9mm buffer. My rifle eats everything (WWB, Russian stuff, reloads, JHP hollow points and anything else that I can get my hands on) no issues what so ever.

The 9mm Q buffer is longer than a standard buffer.  You cannot use the Q buffer and a spacer at the same time.

 

Thanks guys! Looks like some confliting information. Anyone what to try to clear it up? What is the best way to prevent the gun from breaking it's own parts? I also would like reliability to be as close to 100% as possible. Many thanks!

did you even read the post in this thread?
 

There's 17 pages of threads in this sub-forum and I'd venture a guess that there's more than a few that are about spacer and buffer options.  If you're going to give him grief over not reading this thread, why not just bust his balls for even starting this thread at all?  (Just an FYI: there's a half dozen threads about buffers/spacers within the first 5 pages of this sub-forum...)

See you all in the next thread about spacers and/or buffers later today or tomorrow...

Yes, did you? One guy above says "yes you can use both the heavy Q buffer and the spacer" and then next guy says "No you can not use both? So WTF is it before I buy one or the other?

In a carbine length buffer tube, you can run any carbine length buffer in any weight you want and you can also choose to add a spacer/quarters to reduce bolt overtravel.

In a carbine length buffer tube, you can run a specialty, extended length, 9mm buffer (i.e. one that is longer than a standard carbine length buffer) that eliminates the need for a spacer/quarters because the buffer is longer - basically the equivalent length of a standard length carbine buffer and an overtravel reducing spacer/quarters.

In a rifle length buffer tube, you can run a rifle buffer and you can also choose to add a spacer/quarters to reduce bolt overtravel.

In a rifle length buffer tube, you can also run a standard carbine length buffer, but you must run a spacer to take up the difference in buffer length between the rifle and carbine lengths.  This spacer is different than the overtravel reducing spacer/quarters which you can also add if you are running a carbine buffer and length spacer in a rifle tube.  Basically, there are two different spacers at play here, but you could make one spacer that resolves the overall travel reduction necessary.

In a rifle length buffer tube or a non-standard length carbine tube, you can also run a specialty 9mm buffer, but you need to determine how much of a spacer you need to add to adjust for the difference to the length of the rifle or carbine buffer that you would normally run in a .223/5.56 setup and/or the additional spacer length necessary for any additional 9mm specific bolt overtravel reduction.

You cannot run a rifle length buffer in a carbine buffer tube, unless you modify the length of the rifle buffer so it will work.

There's so many magical, specialty buffers that it is very easy for people to get them confused as to whether they are just a heavier than standard weight, longer than standard length, or both.

Actually I said BOTH things in one post but suggested that one should make only one change at a time.

This particular discussionthread has a single page of posts, and if one spent just a few minutes reading it in its entirety, one could learn a lot of details.  Some posts provide general information, some are aimed at solving problems, and others are expressions of experience.  Asking for clarification instead of restating the original question might be appropriate, but just asking the same thing again can make some of us who have bothered to post our experience and suggestions kind of irritable.

Perhaps this photo will help eliminate some of the buthurt here in regards to 9mm carbine buffer selection.  At the top is a 9Q buffer by member Slash.  At the bottom is a standard length buffer and a Spikes spacer.  When using a carbine length receiver extension, (buffer tube), you absolutely cannot use a 9Q buffer and a spacer at the same time.

What is the advantage of running a heavy buffer with 9mm?

I'm running a 5.6oz colt buffer in my 9mm with a cmmg 9mm bcg, and it cycles very slow. The bcg is extremely heavy also, so I'm not sure if it is necessary to run both!

I run the 9Q buffer when I am shooting subgun ammo, (IMI and Finnish).  This stuff is very hot and the big heavy buffer works well with this ammo for me.

Ok thank everyone.....I understand and will probably run both a heavy Q buffer and a spacer(not at the same time) depending on what ammo I use. Anyone have malfunctions/jams when using a heavy Q buffer? If so what ammo were you using? Anyone have malfunctions when using a spacer?

Remember, a Colt-style 9mm carbine is blowback, so the combination of bolt mass, buffer mass and recoil spring resistance is what holds the bolt closed until the bullet has left the barrel.  The hotter the load, the more resistance you need to bolt movement for the same (for lack of a better term) dwell time.  As I had said, my 9s run fine with standard carbine buffers and WWB ammunition.  They do fine with NATO loads too, but they feel rougher, which probably means that I could run my heavier buffer.  I simply haven't tried that yet.

My stance has been that if it works OK, I don't "need" to mess with it.  If that "roughness" starts to be a problem, I'll probably just stick the heavier buffer in and rock with that...and then see how the WWB runs too.