RMW Extreme Build. It has begun.

[Pablo]

Do you attribute the improvement to the new militec lube or the ammo?

Neither directly, although I think the Militec helps.

The improvement came from freeing up the bolt:

1) Honing and removing all burrs in the BC - the "cylinder" was very rough and nasty- I used metal polish and the old rings on the bolt. Made it very smooth. Suggested in this thread.
2) Replacing the gas rings with a one piece ring - JP Enterprises - these are still taking a seat, but seem to be making a better seal, hence better action. My idea.
3) Replacement of bent firing pin - this pin was consuming extra energy and was not right. Replacement pin is still straight. Should have been straight from the start (arrgh!)
4) Use of a Tubbs flatwire pistol caliber carbine spring - less resistance to gas pressure, of course less spring force on return, but now the trigger sets reliably. My idea, and used by .300 Blackout guys.


So basically I changed lots of things outside the chamber, and didn't have a:

A) Failure to eject - all spent cases appeared to fly out at 80°-120° from the rifle, most about 110°.
B) Double feed
C) Stove pipe
D) Failure to feed that didn't set the trigger

Not yet saying these things are eliminated, but simply didn't happen in 100 rounds of both Sig and Underwood 180gr FN (Now I should mention the Underwood felt significantly hotter FWIW)

The feed issue could very well be the magazines. Since I have no pictures or actual dimensions of what a proper adapted grease gun magazine should look like or measure, I am flying a bit blind here. The mag Ron sent is not perfect, so that really doesn't help.

Again - positive progress. Thanks!

Edited to add details

[mrpipesmkr]

Pablo,
  I guess I'm one of those old guys who is tech challenged! I had already responded to your post earlier and was editing it to clear some stuff up when I managed to wipe out the entire post! Sorry if you had already read it and I created confusion.
  I'll try to recap the post.
  I think I will get some of the Miltec and apply it with heat. I have been overlubing  fo break in but think both my builds are pretty much there. The Miltec treatment with a wipe down of light oil over it should allow the gun to run cleaner as it will trap less residue and allow the pressure to blow more residue out.
  The only consistent problem I have is an occasional partial feed requiring the forward assist. This usually happens with a new, tight mag , but also may be due to the chamber being tight. I am considering taking a wooden dowel and 600 grit paper to loosen it up a little.
   I used the white turtle wax early on with my piece to speed break in. I used it on the rings, the four rails the bolt carrier runs on in the receiver and the face of the hammer. Seems to me with these PCC's you are fighting for the most efficient use of the available gas pressure and anything you can do to eliminate friction and drag is a bonus.
  I still feel that reloading with Longshot will help your piece, clean and a good pressure curve.
  I can't emphasize enough that you should verify where the lugs on your bolt are contacting the round to strip it from the mag.  I became very familiar with this problem due to my old lower being out of spec.
  Put a couple of rounds in your magazine. Hold the bolt back manually with the charging handle. Insert the mag in the well and slowley allow the bolt to move forward. Observe where the lugs are contacting the round. If they are only contacting the upper portion of the rim it is contributing to your problem. The only thing you can do about it is figure out a way to raise the mag in the well to achieve better contact on the round.
  Sorry for the confusion with my first post but hope this helps!

[Pablo]

Yeah I thought I was losing it!

I actually get email notifications, so here is what you typed:

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The text of the reply is shown below:
Pablo,
  Wow, what an improvement! I'm happy to see your build come around to where it's at and hope the final kinks can be worked out.
  Freeing up the bolt group is something I did early on and seemed to help. That's why I suggested the white turtle wax polish for your rings.  I also used the same stuff on the four rails the bolt runs on in the receiver and the face of the hammer just to smooth them out. I for sure didn't over do it and maybe could have done more but I think it sped up the break in.  Break in is very important, it seems to me, on these PCC's because you are fighting for efficient use of available pressure.
  I still feel that doing your own loads with the Longshot powder will help overall.
  The only consistent problem I have now is occasional partial feeds that require forward assist. My chamber is fairly tight, which I like because it helps build pressure quicker and is easy on brass, but I may have to take a wooden dowel and some 600 grit paper and loosen it up a little. The tight chamber may be contributing to my occasional partial feeds, although tite, new mags seem to contribute also. Because I need good forward speed on the bolt carrier I have stuck with the standard recoil spring rather than something like your running.
  I can't emphasize enough to examine closely where the bolt lugs are catching the round as it sits in the mag.  Due to my old lower being out of spec I became very familiar with this problem!  Put a round or two in your mag, manually hold the bolt back with the charging handle, insert the mag in the well and very slowly let the bolt go forward. Observe where the lugs contact the round to strip it from the mag. If it is hitting only the upper portion of the rim this is contributing to your problem! I fought this same feed problem with mine. The only solution is to figure out a way to raise the mag in the well for better contact between the bolt lugs and the round.
  Anyway, I feel like you "over the hump" on you build and on your way to a trouble free shooter!  Congratulations !

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[mrpipesmkr]

Pablo,
  Glad you got and managed to save the post. Don't know how I managed to delete it!  Give me a car and I can take it apart. Give me a gun and I can figure it out.  Computers I can turn on and off, search a little and type, that's about it, and pretty slow at that! Generational thing, I think😁  Sometimes my daughter has to rescue me from my computer😳
  Anyway, hope our exchanges have helped you and anybody else following them.  They have provided me with new ideas and helped improve my builds!
  Keep us posted on your progress on your next range trip.

[Pablo]

So in the meantime I was working on other things. But I did try the slow feed per your suggestion.

It seems the slow feeding doesn't work at all, the bolt face or front surface of the lugs just kick the cartridge up so I get a different style of fail to feed jam. This type is nose down stop. Just drop the bolt hard and it feeds fine.

It's good to observe the bolt and top of feedlips relationship though. I cannot imagine the magazine any higher up. The specially machined BC base just rides the feedlips. In fact IF I rest the rifle on the magazine (ie forcing the magazine up), it collides with the BC.

So back to the magazines. I have to tell you, I have four GG magazines and they are all the same as far as construction, and even the machined (by RMW) mag catch slot are all the same. That said the feedlips are all different. (One is a bit mangled up with my ham fisted approach, so I set it aside. ) That said all mags seem to behave the same at the range.

Next range trip, I will take the one with the largest front spread, open it a bit more, make no other changes and see what happens compared to the other two.

[mrpipesmkr]

Pablo,
  Sound like your covered on the mag hight.  I was sure my experience with the low mag was related to your missfeeds but maybe not. Again not being able to actually see your action I have to visualize what's going on and can get it wrong.
  I did not think your piece would slow feed as they all need some velocity on the bolt and carrier to feed properly. I was just wondering where the bolt lugs initially contacted the round. With my old lower raising the round so the point of contact was lower on the head of the round made a significant difference.
  Apparently where your mag sits now you nearly have contact with the bolt lugs on the mag lips.  I had the same close tolerance with the Glock mags initially and I'm sure during firing the weapon was sometimes getting contact at those points. This slamming the mag around was contributing to the missfeeds I experienced.  To alleviate that I took a Dremel and stone and shaved the two feeding lugs on my bolt thinner, taking the material off the sides of the lugs that were contacting the mag lips. This extra clearance made a big difference. I left plenty of metal on the lugs to strip the round and lock the bolt closed but created as much clearence as I could.  If your two lugs are not ground a little thinner you can improve the clearance by taking a little metal off.

[Pablo]

Good stuff.

I just told myself: Step back for a moment. Breathe. Think.

So, say a problem happens every 8-10-12 rounds. On one hand, HUGE problem. Of course. On the other hand, some issue that doesn't happen every round or every third round, could be pretty subtle.

[mrpipesmkr]

Pablo,
  Here are the pics of the shaved lugs on my bolts. Pics aren't the best but maybe you can see what I did. I did the grinding on the 9x25 and Ron did the 10mm.
  As I hope you can see, I did not shorten the lugs at all, just narrowed them down from the side that was contacting the mag to provide more clearance.   You want to leave them long so they make contact as low as possible on the round.  We left them wide at the base and narrowed them down more at the tip to maintain strength and achieve the most clearance.
  If you are having any contact of the lugs and your mag this will help solve the problem.
  If you have any questions post or PM me.

[attachment deleted by admin]

[Pablo]

My lug is definitely not cut like that. Interesting.

[mrpipesmkr]

Pablo,
  The AR15 was designed to feed from both sides of the original magazine. When we change over to Glock mags and I assume, GG mags, the weapon has to feed from the center of the mag. The lips of the .556 mags are much farther apart because they hold two rounds, side by side. The single feed mags, such as Glock, have the lips much closer because they only hold a single round. To feed from the single the bolt carrier has to be narrowed so it will fit through the lips of the mag.  But, these narrow single feed mags also cramp the feed lugs on the bolt, sometimes causing contact between the lugs and the lips. If this is happening, that contact can cause the round to missfeed. By grinding the appropriate sides of the bolt lugs you are providing more clearance between the lips and the lugs, eliminating the problem.
   Here, I have to add that I am not real familiar with thr GG mags. Don't know what kind of clearances you have, but take a look and see. If they single feed chances are the clearances are close.

[Pablo]

This is a full work week for me. I need to study my rifle vs. what you are saying, just don't have time right now.

I didn't have any dummy rounds made up (easy I know) - but I scored some 10mm dummy rounds locally for low $. I was becoming uncomfortable chambering a live round! I'll see how they behaved and I will watch the bolt over the mag.

[mrpipesmkr]

Pablo,
  I know what you mean about chambering live rounds! I get queasy every time I have to do it!
  No problem if you are busy at work! We gotta make money somewhere to pay for our expensive toys! I just wasn't sure if I was making sense or not, trying to describe the work we did to the lugs on my builds and I wanted to be sure my meaning got through. I hope the pics made more sense than my verbal description. I know it was something that helped my builds and hopefully could help yours.
  Again, you have to be the judge as I have next to zero experience with the GG mags but if they feed from the center then it needs to be looked at!
  Did you decide on the 9x25?

[Pablo]

I won't get the 9X25 barrel until this one is running perfectly. Thanks!

[Pablo]

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.

[sgmtino]

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