RMW Extreme Build. It has begun.

[Pablo]

Sounds a bit like you have a sticky bolt. I would do the stuff I mention to free up the bolt in the carrier and get a flat wire spring. None of these things will hurt and most likely will help. It is a bit odd that it improves as you shoot it for that session only . Are you starting with a clean gun? What lube? Outside temp?

[mrpipesmkr]

I have a di qc10  10mm ar that im trying to get the bugs out of as well my issue is the bolt doesn't close all the  way on the first 7-9 rounds and I have to eject the mag and slam the bolt shut till I get to about 5-6 rounds left then the weapon cycles fine I already have the updated lower receiver that helped a bunch any tips from you guys

Sgmtino,
  First of all, welcome aboard!  Always good to have another 10mm DI AR owner to contribute their experience to the board.  I think the idea here is that by pooling our knowledge and fixes we all can end up with reliable 10mm and 9x25 builds. A couple of us have builds that are running pretty good.  The 10mm in a carbine or SBR is just a whole lot of fun.
   Can you give us more info on your build?  Who did the upper, barrel length, Glock mag or other (QC does build other lowers) ect. This will help to compare yours to others.
   The first thing I would say to you is take the time to read all the posts on this board and see if any of the info and fixes can be applied to your build. There is a lot of info posted by the various members dialing in there builds and some of it will be useful.
I think I have experienced the type of problem you are dealing with and have, for the most part, cleared it up. I still have an occasional partial feeds with new mags but they are fewer than before. In my case the round was feeding straight into the chamber but stopped before the bolt fully locked. I usually just have to tap the forward assist to close the bolt.
  I think what was going on with mine was simply that the bolt carrier was not returning with enough force to close the bolt. I think this is because these builds tend to be quite tight when new, before break in. The 10mm does not have the gas pressure of say, a .556 so the carrier may not be moving all the way to the rear of the buffer tube and therefore does not close with enough force.
  As Pablo suggested I went in and used polishing compound to "loosen up" my bolt and smooth out the rings and bore that they run in. This takes some repetition but does take the stiffness out of the bolt. Pablo has also gone to the one piece ring and feels this was an improvement, I have not, yet.
Because these builds tend to be stiff due to the coating used on all parts I also decided to help break in my build by polishing some of the wear points in the upper and lower.
  I used a Dremel with felt pad and polishing compound to smooth out and remove the coating to cut down on friction and drag. You don't have to polish to a high shine on these wear areas but you do want to polish until they are smooth. Polish all four of the rails the bolt carrier runs on, the bolt and rings (as stated) the retainer pin, the tail of the bolt, the face of the hammer and the portion of the carrier the hammer runs against.
  This should help minimize the drag and improve the speed of the carrier as it moves forward.
  Also check to see if the bolt lugs or carrier is rubbing against any part of the mag causing a slow down.
  I have also ordered some of the Militec lube. I think if it is applied properly, according to instructions, it will help reduce drag.
  Let us know how it goes and we will all work together to perfect our builds. All in all, they are a ton of fun!

[mrpipesmkr]

Does make me wonder if the shouldered 9x25 would feed easier and my problem would be cured. I did receive my titanium firing pins last night. Wow they feel light.

Pablo,
  My experience is that the 9x25 does feed easier than the 10. Smaller bullet going in to a large chamber.  Less rubbing, less drag.
  The Titanium pins sound interesting, let us know how they work.

[Mongo]

You had me at titanium.

[Pablo]

It appears as if the Ti firing pin will work fine.

So I loaded up a magazine with 10 dummy rounds. I could really see how they chambered - first of all they chambered perfectly with released bolt catch, bam. That is as expected. Seems like this magazine is tuned correctly.

Then I restuffed the magazine and went slowly....

a) Bolt contacts round
b) Bolt pushes round
c) it looks like bolt slightly contacts mag lips
d) round actually releases and pops up
e) bolt pushes round in chamber (now in slow-mo) the round will hang sometimes, but will chamber with assist button.

My problem may be as simple as the design of the 10mm cartridge with the necessary case edge hitting and catching the AR chamber entrance.

The big difference between the dummy rounds and the rounds I have been shooting is the case crimp area. The dummy rounds is not pronounced at all while most all ammo types I have the lip is quite sharp.

[mrpipesmkr]

Pablo,
  I believe the titanium pin should be stronger than standard, no more bent pins!
  It s hard for me to say what your problem with feeding is without watching the action work. I believe the lugs contacting the mag lips is not a good thing if occasionally it causes a jolt to the mag which throws off feeding, but it sounds like there is no major contact between the lugs and the lips.
  If the round is going nose up as it exits the magazine causing a missfeed you might check and see if the front of the round or the case lip is contacting the front of the mag, throwing the nose up. If it appears this is happening, taking a little metal off the front of the mag would give better clearence.
  When the lugs contact the round are they hitting it low, below the rim, somewhere near the center of the case head? This would tend to make the round go straighter into the chamber.
  Anyway, it sounds as if most of the bugs are being worked out of your build! Let us know how your next range trip goes!

[Pablo]

I will now further examine the relationship between the lower bolt lugs and the magazine.

[Pablo]

I will now further examine the relationship between the lower bolt lugs and the magazine.

I believe polishing those two bolt lugs is nearly miraculous. The next round does not appear to be irritated in the least by the bolt traveling headed back. The lugs just glide over.

But allow me to summarize the most recent changes:

I'm still perfecting this 10mm, but the steps I have taken, have made it a lot better.

1) Oddly the firing pin was ever so slightly bent/out of round, cheap thing. Replaced with a titanium pin. Probably not a huge deal, but was slow in the bolt.
2) Bolt was nasty rough in the carrier. Honed with the stock rings and alloy burrs and carbon broke free, replaced rings with JP Enterprises one piece.
3) Polished the cam and associated parts.
4) Lubricated with Militec
5) Kept same buffer weight (tried a heavy buffer, with original and rifle would barely cycle if at all)
6) Replaced spring with David Tubb's pistol carbine flatwire spring (this probably has made the largest difference outside the BCG)
7) Buffed the bottom two bolt lugs to a mirror finish, after breaking the trailing and inside edges.
Replaced the extractor spring with a HD spring and core but no o-ring
9) Super buffed the extractor face and removed all the burrs and super sharp edges that tore up brass rims
10) Deburred and buffed the cam way and cam pin.

All these things made the rifle run a LOT better.  In fact you wouldn't believe how smooth the action is now since working over the bolt and carrier. I never felt any stock AR BCG this smooth and my very first AR is a Daniel Defense which now has around 12,000 rounds through it and is still not this smooth. Cleaning the bolt up makes that much difference, and is a must do on a 10mm AR.

[Pablo]

Took it to the range yesterday.

The gas system ran exceptionally well.

The only hang ups I had were case rim at the chamber entrance. I need to figure out if it's feeding issue or the chamber entrance is too tight. I contacted Ron earlier on this earlier and he suggested opening the chamber up.

[sstewart]

Very happy for you !!
You have worked very hard to get these results.
I'll have to look at doing some (or all) of the things you have done on mine.

[mrpipesmkr]

Over the past five weeks or so Pablo and I have been in close communication discussing our 10mm and 9x25 carbine builds from RMW extreme.  By explaining to each other improvements we had done to our builds and future plans to improve them we set up a situation where we brainstormed our way into making our carbines run very reliably.  They can be made to be very reliable, and when you reach that point they are a lot of fun to own and shoot.
  This excersize has proven to be a lot of fun for both of us and a learning experiance that is hard to match in terms of pistol caliber DI AR's.   But, we don't believe that every owner of an RMW extreme build would want to go through the many ideas and changes we have had for our builds.
  Our hope has always been to distill what we have done to our builds down to an easy to follow list of important improvements that others could use to improve thier builds.
  So, the following is a distilled list of things we have done. The list is in no particular order but is fairly comprehensive. We will add any other improvements we might have done should we recall them at a future date.

1)    installed Tubbs flat wound spring, Pistol and 300Blackout model.
2)    installed H2 buffer, weight 4.4 ounces
3)    made sure the buffer and spring were lubed
4)    used both the JP and standard rings, depending on build, well broken in
5)    Polished the bolt face until it shined, making sure any ridges were well rounded
6)     polished the cam pin, rails the carrier runs on, hammer face and the ramp the               
        Hammer runs against.
7)     used 600 and 800!grit paper to smooth the chamber walls
8)      polished the chamber walls including the cone at the start of the chamber
9)      polished the firing pin
10)    Trimmed, rounded and polished the bottom two feeding lugs on the bolt insuring that enough material
         was removed to insure the lugs cleared the magazine. Smooth polish eliminates drag on the
         next round feeding in the magazine


    Both Pablo and I will try to answer any questions you might have. The important thing to remember is that with a little tune up work you can have a very reliable carbine that is tremendous fun to shoot.
   It is important to remember that Pablo's build and my two builds are a little different.  Pablo's build is based on a lower that uses GG magazines. My builds both use the QC10 lower and run Glock magazines.  Still, the work we did on our pieces was very similar with a few small variations.

[Pablo]

If you look at my list above. And pipesmoker's more comprehensive list there is one thing that stands clear. A 10mm gas AR starts life fundamentally undergassed. Really almost all efforts need to start with this concept in mind, and the corny goal motto could be: If I can set my 10mm AR up to run on puny factory mouse rounds, it should be a very reliable rifle with hot slow burning powder rounds. Because frankly Ron at RMW does not at all set the BCG and springs up run with anything but the hottest home loaded ammo.

So the number one thing to take from these lists is make sure ALL moving parts are finely polished and move like a Swiss watch. Not only did I learn a lot about the AR-15 platform, I really came to appreciate just how smooth the AR can be, and how nice you can make ALL your AR's. You can get your magazines feeding nicely, your chamber feeding perfectly - but if your BCG is not freely moving, your rifle won't run.

Yes, we both feel qualified to help and guide. I have now had a couple+ people contact me. Either wanting to buy, questioning my motives, previous or current RMW owners. I too had my doubts at some points if this would even be viable. Others have given up. Ron has sent refunds. That can't be good for him. We want to succeed. We want others to succeed and we want Ron to have a successful business, despite what some people on arf.com accused me of (like this whole thing was junk I made up!).

So ask us. Start a new thread. PM us (we prefer public so all can gain) . Communication is good and love for 10mm Firearms.com is best!

[sqlbullet]

Sorry to be that guy, but I don't wanna dig back through the 10 pages.

You went to an H2 buffer.  What weight buffer did you start with?

I am a relative AR-noob, with only 2 completed builds (5.56 SPR and 300 BLK Carbine), and four in progress (CMP Service Rifle, 5.56 Carbine, 308 Win and 358 Win), and two yet to be started (260 Remington and an undecided 6.5mm in an AR-15).

It seems to me that an undergassed gun would want as little reciprocating mass as possible, aka a carbine buffer.  And possibly a JP Rifles low mass bolt carrier.  I have been reading the thread as you went and I don't recall these being discussed, but I may have missed it.

You I am curious of the H2 was chosen for additional momentum for feeding, and the gun was well enough gassed to drive it with a light-ish spring, or if I just am missing something.

[Pablo]

Sorry to be that guy, but I don't wanna dig back through the 10 pages.

You went to an H2 buffer.  What weight buffer did you start with?

I am a relative AR-noob, with only 2 completed builds (5.56 SPR and 300 BLK Carbine), and four in progress (CMP Service Rifle, 5.56 Carbine, 308 Win and 358 Win), and two yet to be started (260 Remington and an undecided 6.5mm in an AR-15).

It seems to me that an undergassed gun would want as little reciprocating mass as possible, aka a carbine buffer.  And possibly a JP Rifles low mass bolt carrier.  I have been reading the thread as you went and I don't recall these being discussed, but I may have missed it.

You I am curious of the H2 was chosen for additional momentum for feeding, and the gun was well enough gassed to drive it with a light-ish spring, or if I just am missing something.

YOU are exactly correct. I did not change my buffer, and in fact I bought the AIM low mass BCG (not modified and installed though) . I have the regular buffer and took out some mass out, but it didn't help all that much. A couple things going on here. First of all pipesmoker did use the H2, but he runs hot ammo, and as far as I know hasn't run lighter loads. PLUS more importantly all AR's need that dynamic mass in the buffer, so a lighter easier moving bolt is good, the impact smack is still needed. Mr Pipesmoker needs to now try a regular buffer with his cleaned up chamber and maybe try some factory dumb 10mm ammo.

[mrpipesmkr]

Sorry to be that guy, but I don't wanna dig back through the 10 pages.

You went to an H2 buffer.  What weight buffer did you start with?

I am a relative AR-noob, with only 2 completed builds (5.56 SPR and 300 BLK Carbine), and four in progress (CMP Service Rifle, 5.56 Carbine, 308 Win and 358 Win), and two yet to be started (260 Remington and an undecided 6.5mm in an AR-15).

It seems to me that an undergassed gun would want as little reciprocating mass as possible, aka a carbine buffer.  And possibly a JP Rifles low mass bolt carrier.  I have been reading the thread as you went and I don't recall these being discussed, but I may have missed it.

You I am curious of the H2 was chosen for additional momentum for feeding, and the gun was well enough gassed to drive it with a light-ish spring, or if I just am missing something.

Sqlbullet,
  No problem, I wouldn't want to read through 10 pages of old posts either! That's why Pablo and I decide to post our list on the board.  We will help all we can and try to clarify anything that seems confusing.
   I originally used a standard carbine buffer (app. 3 ounces) in my builds.
   Installed the H2 buffer in both my builds. You are right about the reciprocating mass and weight. I found that increasing the buffer weight (4.4 ounces) helped my builds to feed easier. I was having trouble getting proper feed out of my Glock mags when they were full.  Adding the mass seemed to help and both builds have enough gas to run the buffers. Pablo is right that I run somewhat hot loads. My standard is a 180 grain Hornady HAP pushed by 9.6 grains of Longshot with a standard primer. I have run other loads such as 155 gr with equal success.  Lighter bullets use more powder which in turn creates more gas volume and pressure.
  The Tubbs flat wound pistol and 300 blackout spring was a big help with this. It ran somewhat with the standard carbine spring and not at all with the Wolf extra power spring.
  The Tubbs spring is designed to exert equal force throughout its travel where the standard spring creates increasing force as it stacks up. This means the pressure created by theTubbs when the bolt is closed on a round is greater, requiring more pressure to move it, increasing lock up time and the available pressure to move the bolt and carrier.  As the bolt and carrier move back they encounter less resistance from the Tubbs spring than they would with the standard spring when it begins to stack. Therefore you don't lose much if any velocity on the bolt and carrier.
  It's important to point out here that my 9x25 build has an adjustable gas block on it which I can use to help tune it to the H2. I put the H2 in the 10mm, got it to run, liked it, and then put it in the 9x25 with a slight adjustment to the gas block.  The adjustable gas block cannot be installed on the 10mm because there is not enough room in the gas system for it and besides it needs ALL available gas.
  I hope this info helps clarify!