Fixing my Stag/RRA/DPMS mistake

AR/M4 AR Technical Discussion
1

This is my first time posting. I have numerous questions, thanks to Rob’s article in Surefire’s Combat Tactics.

Here is my AR line-up:

  1. LMT Complete Lower with Magpul CTR on mil-spec buffer ext., Stag 2HT upper with Samson free float quad rail
  2. RRA Complete Lower (gunsmith assembled with a DPMS LPK, Magpul CTR, MOE grip), Stag 2HT upper
  3. RRA Complete rifle, 16" heavy barrel, Troy MRF rail, Magpul CTR, MIAD grip
  4. DPMS Panther Lite 16, YHM drop in rail, ergo grip (in process of being sold at profit to update other ARs)
  5. DPMS kit gun with M4gery 16" upper, gun is built on a DPMS “K” lower, parts are all of unknown origin, gunsmith who assembled kit has since passed away. Since purchase, I’ve added a Troy MRF, and CAA stock, MOE grip.

All of the above rifles have Magpul winter trigger guards. All have commercial buffer ext. unless otherwise noted.
Above rifles have no modifications to Bolt carrier groups, unknown as to proper staking or if they have the correct extractor spring.

I also have 3 complete lowers:

  1. Gunsmoke Enterprises lower, CAA stock on comm. buffer ext.
    I intend to put a .22 upper on this lower for training
  2. DPMS lower, MOE stock on mil-spec ext.
  3. DPMS lower, M4 type stock on comm. ext.
    I intend to put a standard M4gery upper on this lower and put it away for sale after a possible future AWB.
    All are gunsmith assembled with DPMS LPKs
    All of the above rifles/lowers have standard carbine buffers

The first step I have taken is to order H buffers to replace the carbine buffers, which leads me to my 1st question:
What are the differences between H, H2, and H3 buffers, besides the weight? Am I ok replacing with H buffers or is my money better spent on an H2 or H3? Is there some advantage to the H2 or 3? I looked for this in the forums, and found no real answer.

Next, I’ve ordered the correct extractor springs and inserts, and a MOACKS tool from Michiguns to stake the carrier keys correctly.

I have an LMT upper on order, and I plan on putting an M16 BCG in this from Larue Tactical, I will put this upper on the LMT lower I already have.

I also have another stripped RRA lower that I will be assembling with a DPMS LPK, MOE stock and grip, commercial buffer ext, VLTOR receiver end plate, and H buffer. Any problems with this set up? Anything I should change before assembly?
I intend to move one of my Stag uppers to this lower, and replace the BCG with an M16 model from Larue. I also intend to replace the BCG on the other Stag upper with an M16 BCG from Larue.

This leads me to my next question: On my complete RRA rifle, do I really need to buy another M16 BCG, or will I be okay with properly staking the carrier key and putting the correct extractor spring in? Possibly moving one of the Stag BCGs over to it after completing these steps since the Stag uppers are brand new. Same for the DPMS kit gun. And will these BCGs be okay for back ups after completing the required upgrades?

Last 2 questions: What are these anti-rotating pins from KNS and why do I need them? And will I run into any problems from assembling these lowers with DPMS lower parts kits?

Sorry for the long thread, and I appreciate everyone’s help. I’ve wasted alot of money changing things around on these guns needlessly, and I’d like to get them right for the last time. Thanks.

2

Have you read this thread which addresses some of these questions?

3

yes I have, but it didn’t answer all my questions. Haven’t been able to find a reason for the H2 or 3 buffer, I’ve purchased a couple H buffers, and I want to find out if I should spend the extra for the 2 or 3. Tired of buying the same thing twice over and over again. I have bins of parts that were used briefly and probably will never be used again. I’m still wondering about the BCGs. I’d rather not have to purchase 5 or 6 M16 BCGs, but if I have to, I will. I’m interested in making all my rifles as strong as possible without breaking the bank, in the event the next AWB bans more than just flash hiders and collapsible stocks. Besides trying to acquire more lowers and uppers, should I be focusing on BCGs as well? Is fixing the problems with my current bcgs not going to be enough, even for back ups? Am I going to regret using dpms lower parts kits? I know my original post rambled a little, but I’m trying to cover everything. Thanks.

4

I didn’t read through your whole initial post, but my thought on BCGs is that as long as the firing pin is shrouded I wouldn’t worry about replacing them immediately. If the firing pin is not shrouded then I would replace it right now.

Also, if you have a known-good bolt, you can replace just the carrier. On the other hand, if you have a shrouded carrier you could replace just the bolt with an HPT/MPI one. If you read the article you’ll see that MPI is pretty pointless without the HPT, so be careful in that regard.

5

On buffers…

If you have a 16" barrel I’d put in an H buffer. Shorter than that you might try an H2, but an H would be fine too.

Some guns MAY work better with H2, H3, whatever. But, this requires some amount of tinkering to figure out which one works best in which rifle and for all ammo types you may fire in that rifle. The only way to do this is trial and error, so it can get time consuming and expensive in terms of ammo testing.

What I do, is keep buffers C-9mm (C, H, H2, H3, 9mm) around and try a couple in any new gun. Then I stick whichever one works best into the gun, and order a replacement of it for my testing stock.

In short, the standard H will probably serve you best with the least amount of hassle. But ALWAYS test-fire your guns for as many rounds as possible anytime you make any sort of change. Even something as innocent seeming as a BCG or buffer.

6

rob_s,

Thread hijack in progress. Did I understand correctly that Bushamsters are not HP/ MPI tested?

7

They batch test. This goes for bolts and barrels. They mark everything as if it’s tested, but they only test samples.

I wish I still had a barfcom account so I could search the archives for the post by Jarred at BM that admitted this years ago. It caused a HUGE shitstorm of people that couldn’t believe that BM would do this.

Some people initially thought that they were only marking the actual samples they tested, in which case everyone ran home, looked to see that their barrel was marked, and thought they were good. Until they all realized that every single barrel was marked, at which time BM came clean.

They are capable of doing the testing (or having it done) and I have heard mutterings from time to time that they will or have done all items for special orders or contracts, but the rifles they have sitting on store shelves are batch tested only.

8

thanks for the info, Rob, it was your article in Combat Tactics that brought me to this site and got me looking into this. Now where do I find pictures of what a shrouded and unshrouded carrier look like? As for the bolt being interchangeable, I read somewhere that you weren’t supposed to mix and match bolts and carriers? Last question, so if I replace the BCGs in my stag 2HT uppers with M16 BCGs from Larue, that should correct most of the problems brought up in your article? It seems most of the issues revolve around the BCG. Oh yeah, and what about the fact that I’ve built most of my lowers with dpms lower parts kits? Is this something I’m going to regret?

9

Rider,

Mixing and matching bolts and carriers means nothing. The bigger issue is swapping bolts between different guns and not checking the headspace. Some people say no big deal, but I check it no matter what.

10

The only time I’ve ever had a concern with swapping around bolts is going from one well-worn gun to another. New bolt in old barrel shouldn’t be an issue, and vice versa. Frankly I think the whole bolt thing comes out of a military environment where parts can get worn down to the point that they may not even be truly serviceable in the gun they came from.

This image stolen from a post by “m4builder” in this thread. From top to bottom

M16 Carrier (shrouded firing pin, extra mass at rear)
Shrouded AR15 Carrier (shrouded firing pin, less mass at rear)
Un-shrouded AR15 Carrier (firing pin exposed, no weight at rear)

I wouldn’t replace the one in the middle. Stake it and stick an HPT/MPI bolt in it at most.

11

Mine all look like the one in the middle, and I believe all of them need to be properly staked. Based on your chart, I guess my 2 Stag uppers don’t have the proper extractor springs in them either. I’ve already ordered those. I’m still going to order an M16 BCG from Larue for my Stag upper that I’m running on my LMT lower. At least then I’ll have a BCG for when I finally get my LMT upper. Will the pocket MOACKS be enough for what I need to do, or should I order the regular one?

12

What are these anti-rotation pins from KNS and why do I need them?

13

I prefer the pocket MOACKS

You don’t need the KNS pins.

14

Okay, last question. DPMS lower parts kits, are they okay to use? I have a couple LPKs from M&A, should I use one of these on my final lower build instead?

15

Okay, so I can’t find any MPI’ed bolts at the moment. For my Stag BCGs that look like the BCG in the center of the photo, what if I used BCM’s uprgrade kit? The one with the shot-peened extractor and all that? Would that be enough? I ordered the 3 pack of springs from BCM with the inserts, these are the ones I need, right? I thought they were supposed to have 5 coils? Maybe I’m counting from the wrong spot but the ones I got seem to have 3 or 4 coils. And again, what about using the DPMS lower parts kits?

16

don’t have an answer, but will throw in another vague comment … i seem to recall a conversation with an M4C mod who commented that DPMS lower parts kits have a lot of pot metal in 'em.

but i’ll wait for clarification to confirm this.

-slut

17

I guess I’ll just use one of the M&A kits that I have in the bin.

18

Rider, don’t let the minutia get you sidetracked.

IMHO what you need to do is pick one carbine and make that your best quality go-to gun. Get a quality BCG in the gun, get a quality LPK in the gun, ensure that all the parts are staked that should be and that the gun has the right buffer, etc.

If I were in your exact shoes right now, I’d use the LMT complete lower and look into selling off something else and/or trading with someone to get a Noveske, LMT or BCM upper. If you feel that you need a rail system on the gun, use a Larue or Daniel Defense.

Personally, I’d rather have at least one top-shelf gun with top-shelf parts on it than 5 that I’m trying to get up to speed.

THEN you can start working on the others.

19

Yeah, that’s my plan. I’ve been thinking about the Larue stealth upper with an 18 inch barrel and 13.2 or 12 inch rail. Partly for the availability. I’m waiting on an LMT from my local gun shop, and I’m got my email up for the notification on Bravo about the LMT or BCM uppers. Money’s not the issue, its the availability. If an LMT upper popped up right this second on Bravo I’d order it w/o hesitation. Until then I’m going to bring my Stag uppers up to the best standard I can get them to.
On a side note I did sell my DPMS Panther lite 16 yesterday for $1300. Ha.
I’m considering selling my other DPMS franken-kit-gun with the Troy MRF rail on it, I can get 1200 for it tomorrow, but I’m thinking about holding it for sale post- future AWB. Thoughts?

20

oh yeah, and what about the extractor upgrade kit BCM sells for 29.95? Would that work for my 2 Stag BCGs, since I can’t seem to find an MPI’d bolt?