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Posted: 2/8/2018 9:15:07 AM EDT
[#1]
That's a fascinating pair of rails you've got there. Could you give us a better shot of em and tell us how they work?
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Posted: 2/8/2018 4:46:31 PM EDT
[#2]
@BartCarter
@60-Driver To all those having failures to eject: I had the same problem with a factory 45 build. The problem was the ejector spring - it was shorter and smaller in diameter than a standard AR spring. Still scratching my head on that. Swapped it with a new one. Zero problems! |
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Posted: 2/8/2018 7:00:25 PM EDT
[#3]
Quote HistoryQuoted:
That's a fascinating pair of rails you've got there. Could you give us a better shot of em and tell us how they work? Quote HistoryQuoted:
That's a fascinating pair of rails you've got there. Could you give us a better shot of em and tell us how they work? Quoted:
@BartCarter @60-Driver To all those having failures to eject: I had the same problem with a factory 45 build. The problem was the ejector spring - it was shorter and smaller in diameter than a standard AR spring. Still scratching my head on that. Swapped it with a new one. Zero problems! |
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Posted: 2/8/2018 9:25:12 PM EDT
[#4]
Quote HistoryQuoted:...To all those having failures to eject: I had the same problem with a factory 45 build. The problem was the ejector spring - it was shorter and smaller in diameter than a standard AR spring. Still scratching my head on that.
Swapped it with a new one. Zero problems! (BTW, my ejecting problem stopped 100% with my enlarging of the ejection port on my non-CMMG Guard upper) |
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Posted: 2/8/2018 9:41:59 PM EDT
[#5]
Quote HistoryQuoted: @BartCarter What kind of FTE's were you getting exactly? Was the brass staying attached to the extractor and coming forward with the bolt? I'm asking because I'm experiencing similar issues with my 45 build. Every 15 or so rounds, a spent case doesn't eject and "rides" the bolt back into battery resulting in a mangled case or stovepipe: I've clearanced the port to the same size as my DI45 receiver. Maybe I need to open more? I would think any interference would at least knock the brass off the bolt face and cause a jam/stovepipe, not allow it to stay seated in the bolt? I'm looking at the extractor next to see if maybe sharp edges are biting into the rim and holding onto it... Quote HistoryQuoted: @BartCarter What kind of FTE's were you getting exactly? Was the brass staying attached to the extractor and coming forward with the bolt? I'm asking because I'm experiencing similar issues with my 45 build. Every 15 or so rounds, a spent case doesn't eject and "rides" the bolt back into battery resulting in a mangled case or stovepipe: I've clearanced the port to the same size as my DI45 receiver. Maybe I need to open more? I would think any interference would at least knock the brass off the bolt face and cause a jam/stovepipe, not allow it to stay seated in the bolt? I'm looking at the extractor next to see if maybe sharp edges are biting into the rim and holding onto it... Quoted:
Quoted:
I took my new build from the CMMG Guard BCG/barrel/lower for sighting in and testing of magazines, etc. I was getting about 1 in 15 failing to eject. CMMG posted if you don’t use their upper, you may have to clearance the ejection port... So, if you are having any ejection problems with your Guard barrel/BCG build, I highly recommend clearancing the ejection port. Check my dimensions to see if you are close to the clearancing I did. I believe that the upper for the Guard .45 and 9 mm is the same. For a quick and dirty look, the upper clearance took out about half of the bolt bearing surface in the upper and the bottom cut came down to about the top of the lower bearing surface. |
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Posted: 2/9/2018 2:46:29 AM EDT
[#6]
Quote HistoryQuoted:
Here is what I posted with my 9mm: There are minor differences in the Guard BCG from a DI BCG. (See Mad Machinist post previously) This may come in place too. Check my dimensions to see if you are close to the clearancing I did. I believe that the upper for the Guard .45 and 9 mm is the same. For a quick and dirty look, the upper clearance took out about half of the bolt bearing surface in the upper and the bottom cut came down to about the top of the lower bearing surface. But the FTEs you were having...they were the same as this? Brass staying attached to the bolt? |
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Posted: 2/9/2018 3:08:49 AM EDT
[#7]
Quote HistoryQuoted:
That's a fascinating pair of rails you've got there. Could you give us a better shot of em and tell us how they work? 
Needless to say, the combination of all these random parts makes it harder to drill down on the root cause of the FTE's but overall the gun works. I get 1-2 FTEs average per mag, sometimes none. I've also experimented with a standard lower using UZI 45 and PPS-43 mags: 
I get the exact same FTE's with these setups which makes me think the problem lays somewhere in the upper, either the extractor or ejection port. I smoothed out the extractor with a file last night so I'll know more after my next live fire test tomorrow... |
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Posted: 2/9/2018 3:11:03 AM EDT
[#8]
Quote HistoryQuoted:
To be clear, you put in a standard AR spring, or you got a new one from CMMG? (BTW, my ejecting problem stopped 100% with my enlarging of the ejection port on my non-CMMG Guard upper) Quote HistoryQuoted:
Quoted:...To all those having failures to eject: I had the same problem with a factory 45 build. The problem was the ejector spring - it was shorter and smaller in diameter than a standard AR spring. Still scratching my head on that.
Swapped it with a new one. Zero problems! (BTW, my ejecting problem stopped 100% with my enlarging of the ejection port on my non-CMMG Guard upper) |
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Posted: 2/9/2018 10:12:02 AM EDT
[#9]
Quote HistoryQuoted:
snip I've also experimented with a standard lower using UZI 45 and PPS-43 mags: |
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Posted: 2/9/2018 10:58:58 AM EDT
[#10]
Quote HistoryQuoted: As mentioned it's a project gun I've been tinkering with - Rock River PDS upper receiver/recoil system, CMMG Guard BCG/barrel, Palmetto State KS-47 lower with HK USC lower shoehorned into the magwell (the short spring is just to keep the buffer in place):
https://i.imgur.com/UEPfYZl.jpg?1 https://i.imgur.com/qmglrFG.jpg?1 Needless to say, the combination of all these random parts makes it harder to drill down on the root cause of the FTE's but overall the gun works. I get 1-2 FTEs average per mag, sometimes none. I've also experimented with a standard lower using UZI 45 and PPS-43 mags: https://i.imgur.com/qDRaGa6.jpg?1 I get the exact same FTE's with these setups which makes me think the problem lays somewhere in the upper, either the extractor or ejection port. I smoothed out the extractor with a file last night so I'll know more after my next live fire test tomorrow... http://www.gwacsarmory.com/cav-15-mkii-ar15-stripped-lower-blemmish-ar-15-black/ You'd have to add the Hahn magblock. GWACS stocks it. |
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Posted: 2/9/2018 2:08:57 PM EDT
[#11]
Quote HistoryQuoted:
I'm think of moving to the UZI mag for my franken-Guard. This should allow me to put the mag cut exactly where I need it (and use a standard mag catch), no? Quote HistoryQuoted:
I'm think of moving to the UZI mag for my franken-Guard. This should allow me to put the mag cut exactly where I need it (and use a standard mag catch), no? Quoted:
That's a fascinating project. If you'd like to add more variables to the mix, the Cav Arms Mk 2 that takes .45 ACP Grease Gun mags is on sale as blems @ GWACS right now for $85: http://www.gwacsarmory.com/cav-15-mkii-ar15-stripped-lower-blemmish-ar-15-black/ You'd have to add the Hahn magblock. GWACS stocks it. 
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Posted: 2/9/2018 2:11:22 PM EDT
[#12]
Quote HistoryQuoted: I've used Uzi mags with my blowback uppers and always had a standard mag catch. Some have reported issues with the catch not being deep enough to engage the mag slot but I haven't seen it. Rock River and Spikes (I think) both make a specialized 9mm mag catch that has a catch which is a little deeper. |
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Posted: 2/9/2018 2:23:53 PM EDT
[#13]
Quote HistoryQuoted: Unmodified UZI mags don't have their slot cut anywhere near the standard AR15 spot - right? |
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Posted: 2/9/2018 3:34:00 PM EDT
[#14]
Quote HistoryQuoted: I'll probably open the entire port some more. I just noticed there're alot of brass marks on the back of the port. Like not on the deflector, but the actual port. Weird. But the FTEs you were having...they were the same as this? Brass staying attached to the bolt? |
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Posted: 2/9/2018 5:57:13 PM EDT
[#15]
I replaced it with a standard AR ejector spring. The failure was a case sticking to the bolt face.
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Posted: 2/9/2018 11:11:23 PM EDT
[#16]
Quote HistoryQuoted: @BartCarter What kind of FTE's were you getting exactly? Was the brass staying attached to the extractor and coming forward with the bolt? I'm asking because I'm experiencing similar issues with my 45 build. Every 15 or so rounds, a spent case doesn't eject and "rides" the bolt back into battery resulting in a mangled case or stovepipe: https://www.AR15.Com/media/mediaFiles/444683/IMG_0936-444984.JPG https://www.AR15.Com/media/mediaFiles/444683/IMG_0937-444985.JPG https://www.AR15.Com/media/mediaFiles/444683/IMG_0938-444986.JPG I've clearanced the port to the same size as my DI45 receiver. Maybe I need to open more? I would think any interference would at least knock the brass off the bolt face and cause a jam/stovepipe, not allow it to stay seated in the bolt? I'm looking at the extractor next to see if maybe sharp edges are biting into the rim and holding onto it...
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Posted: 2/9/2018 11:14:58 PM EDT
[#17]
Quote HistoryQuoted: I'm think of moving to the UZI mag for my franken-Guard. This should allow me to put the mag cut exactly where I need it (and use a standard mag catch), no? 
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Posted: 2/10/2018 1:27:45 AM EDT
[#18]
Quote HistoryQuoted:
Sorry, to be honest, I didn't pay that close attention, just than it did not eject. Quote HistoryQuoted:
Sorry, to be honest, I didn't pay that close attention, just than it did not eject. Quoted:
I replaced it with a standard AR ejector spring. The failure was a case sticking to the bolt face. |
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Posted: 2/10/2018 1:31:08 AM EDT
[#19]
Quote HistoryQuoted:
What bolt are you using??? If it is a Guard bolt , I'll check something on the one I have in the AM if I can remember..... Yep it's a Guard bolt & carrier. I'll remind you to check! 
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Posted: 2/10/2018 10:26:44 PM EDT
[#20]
Quote HistoryQuoted: Macon Armory mag and adaptor work perfectly with a guard upper.....as well as out DI upper... |
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Posted: 2/10/2018 11:24:21 PM EDT
[#21]
Oh yeah, Rudy here's your reminder....find anything of interest this morning worth sharing?
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Posted: 2/11/2018 8:53:57 AM EDT
[#22]
What's the highest roundcount some of you have on your CMMG guard?
Do you think the 9mm GLOCK fed Guard still needs some tweaking?? |
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Posted: 2/11/2018 1:46:14 PM EDT
[#23]
Quote HistoryQuoted:
Finished milling my upper to open up the ejection port. I milled the top front half 0.038" and the entire length of the bottom 0.110".
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Posted: 2/11/2018 7:25:39 PM EDT
[#24]
Anyone know where can purchase just the lower for the 45? I can justify buying half now paying for the stamp then buy the upper after approval.
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Posted: 2/11/2018 10:48:53 PM EDT
[#25]
If I read him right, Rudy says the Angstadt Arms lowers are @ the right height for a lugged bolt, but I don't know if they're doing a large mag frame.
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Posted: 2/13/2018 10:55:45 PM EDT
[#26]
Quote HistoryQuoted: @BartCarter - Don't suppose you have a picture of your ejection port? I got the dimensions you listed, just want a graphic of what it actually looks like. |
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Posted: 2/13/2018 11:04:53 PM EDT
[#27]
Not sure you can unless you're a member. Is there a 'Media' section underneath the box where you type a post? w/ "Select File" and "Upload" buttons?
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Posted: 2/14/2018 12:47:32 PM EDT
[#28]
Quote HistoryQuoted: Macon Armory mag and adaptor work perfectly with a guard upper.....as well as out DI upper... PM sent! |
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Posted: 2/14/2018 7:35:04 PM EDT
[#29]
Found a good picture. I saved it, opened it in paint program and enlarged it.
Guard article with pictures |
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Posted: 2/14/2018 9:42:00 PM EDT
[#30]
Quote HistoryQuoted: @BartCarter - Don't suppose you have a picture of your ejection port? I got the dimensions you listed, just want a graphic of what it actually looks like. LINK |
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Posted: 2/17/2018 1:37:45 AM EDT
[#31]
Thanks for the pics. I pretty much had the port opened to a similar size but went ahead and took a little more off the bottom half to see if it would help my FTE issue.
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Posted: 2/17/2018 1:56:22 AM EDT
[#32]
Took it out today for another test with the larger ejection port. Only shot 10 rounds with no FTE's but did discover another potential issue.
For those with Guard 45's...is a ~0.01-.02" gap between the barrel extension and bolt carrier normal? 
Carrier sticks out about 0.016" 
I noticed the gap when I first built the upper but figured it was inherent of the radial delayed system. Well after shooting a few hundred rounds, I've experienced several split cases (all factory new ammo). Initially I thought it was from sharp bolt lugs scoring the brass as it cycled, deeply enough to cause case failure. But I polished the lugs and the gouging went away. Then today, a gunsmith friend watched me shoot and found another split case. He suggested it might be firing a little out of battery. That's when I had my "aha" moment. Maybe it IS slightly out of battery. I stopped shooting after the 10 rounds. I took it home and compared to my Guard 9mm. It's kinda hard to see but there's definitely not as much gap: 
Another thing I compared was the back of the bolts. The 45 has about .010" more material on the back: 
I also tried a bunch of different configurations using other barrels, receivers, etc and had the same result. I have a question in to CMMG tech support so we'll see what they say. Anyone else experience this? |
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Posted: 2/17/2018 10:30:41 PM EDT
[#33]
CMMG's ejection port looks exactly like Anderson's 458 SOCOM upper receiver.
For my new Guard upper I used the 458 upper and will try it with CMMG's 9mm gas deflector and ejection port cover. My first one threw cases far enough back it could be a problem shooting lefty. We'll see how it goes... |
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Posted: 2/18/2018 5:38:07 AM EDT
[#34]
I pulled the spring out of carrier and found I've got about .025 gap. WIth barrel on a standard brownells upper my carrier is flush with the rear of the upper. No FTE's with a used carbine spring, hydraulic buffer, CMMG lower and Glock mags. Brass hits the right side of my chest,lands about 5 to 6 feet out in nice little pile. When I tried a extra power spring the LRBHO didn't catch, and the gun had nose dive on bolt close. Next thing is a flat wire spring and I might cut coils to get a perfect tune. Also will turn down the barrel dia to 5/8 no taper
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Posted: 2/18/2018 11:19:34 AM EDT
[#35]
Thanks for the reply. Well if the gap is normal then I'm back to the drawing board.
 In addition to split cases, my brass doesn't eject in neat piles. I'd say most go to ~2 o'clock but they kind of go all over. Only configuration I haven't been able to try is with an actual Guard lower. In hindsight I wish I'd started with a factory rifle that worked then dissected it to build my gun.
Side note, how heavy is your hydraulic buffer? |
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Posted: 2/18/2018 5:04:16 PM EDT
[#36]
Kind of sounds like bolt is open too soon and traveling to fast. Ejecting at 2 means the bolt is striking the empty on closing, and bulged cases. My buffer is about 4.5 oz. I'd try H2 buffer and get flat wire spring that should slow it down.
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Posted: 2/18/2018 9:13:50 PM EDT
[#37]
Strangely though, they don't seem to eject with too much distance. Yeah mostly at 2 o'clock but only a few feet from the gun. If the bolt had excessive velocity, I'd expect the brass to launch further than they do.
Right now total reciprocating mass is about the same as a stock Guard. I have 4oz & 5.5oz buffers I can try. That will make the total mass ~18.5-20oz. |
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Posted: 2/21/2018 11:59:43 AM EDT
[#38]
Sorry, I read multiple pages, but can't keep track due to all the variations.
Is a 9mm guard bbl/bolt combo g2g on a colt-style (QC10/spikes) lower with minor tweaks? If so, what needed to be done? Thinking of doing the conversion for my USPSA PCC rig. |
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Posted: 2/21/2018 12:02:10 PM EDT
[#39]
Quote HistoryQuoted:
Sorry, I read multiple pages, but can't keep track due to all the variations. Is a 9mm guard bbl/bolt combo g2g on a colt-style (QC10/spikes) lower with minor tweaks? If so, what needed to be done? Thinking of doing the conversion for my USPSA PCC rig. |
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Posted: 2/21/2018 9:25:37 PM EDT
[#40]
Seems like a lot of tinkering to get these guards running right.
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Posted: 2/21/2018 10:32:33 PM EDT
[#41]
To get Guards running with mags they weren't designed for.
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Posted: 2/22/2018 10:57:32 AM EDT
[#42]
Right.
I have a complete setup for PCC already, lots of mags, extensions, mag holders, etc and two other colt-style 9mm builds. Otherwise I'd just run the Glock mags (or an MPX) and be done with it. I have a dedicated 9mm lower, so it sounds like removing the ejector and filing down the mag catch might make it tick? Mag catch is easy enough to replace if I screw up I suppose. Just debating selling the whole kit and buying new vs. retro-fit. |
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Posted: 2/22/2018 10:59:12 AM EDT
[#43]
Quote HistoryQuoted:
Right. I have a complete setup for PCC already, lots of mags, extensions, mag holders, etc. Otherwise I'd just run the Glock mags (or an MPX) and be done with it. I have a dedicated 9mm lower, so it sounds like removing the ejector and filing down the mag catch might make it tick? Mag catch is easy enough to replace if I screw up I suppose. |
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Posted: 2/22/2018 11:09:08 AM EDT
[#44]
I'm going to say yes without being at home, but based on this pic it appears so. Something I can do with a dremel?
QC10 
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Posted: 2/22/2018 11:11:03 AM EDT
[#45]
Quote HistoryQuoted:
I'm going to say yes without being at home, but based on this pic it appears so. Something I can do with a dremel?
] |
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Posted: 2/22/2018 2:38:48 PM EDT
[#46]
Quote HistoryQuoted:
Right. I have a complete setup for PCC already, lots of mags, extensions, mag holders, etc and two other colt-style 9mm builds. Otherwise I'd just run the Glock mags (or an MPX) and be done with it. I have a dedicated 9mm lower, so it sounds like removing the ejector and filing down the mag catch might make it tick? Mag catch is easy enough to replace if I screw up I suppose. Just debating selling the whole kit and buying new vs. retro-fit. As for buying new vs. retrofit, I say it all depends on how much you like to tinker/modify your guns. If it's something you like to do as a hobby I say go for it. Some folks prefer buying a gun that runs right out of the box (a factory Guard or MPX fit that bill nicely). Me personally, I like to tinker. Besides I have too much invested in existing lowers to justify buying another one w/ new mags, etc. |
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Posted: 2/24/2018 10:31:48 AM EDT
[#47]
Wandered a little off the theme, this was about the guard gun, not trying to make the barrel and bolt work in some other thats lower was designed for blow back using glock mags.
For best result use their lower also |
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Posted: 2/26/2018 10:06:33 PM EDT
[#48]
Quote HistoryQuoted:
Wandered a little off the theme, this was about the guard gun, not trying to make the barrel and bolt work in some other thats lower was designed for blow back using glock mags.
For best result use their lower also |
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Posted: 2/28/2018 6:53:34 PM EDT
[#49]
Quote HistoryQuoted:
@badkarmaiii - Any chance you were able to measure the MPX buffer? Quote HistoryQuoted:
Quoted:
I can measure at work tomorrow. |
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Posted: 3/1/2018 1:39:12 AM EDT
[#50]
Oh thanks! Kinda forgot about that. Is that the length or OD?
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