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Posted: 4/7/2025 10:29:42 PM EDT
[Last Edit: thindude][Edited]
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hey guys, looking for some insite. bought a complete AR45 pistol from Pro2A Tactical. I have 200 rounds through it and noticed the front of the buffer is getting ding marks and indents all around the outter edge from the buffer detent. the detent is bent forward toward the BCG.  i contacted pro2a and sent them photo's. and their responce was "If you did not change the buffer and spring then it’s your buffer tube. I suspect it is internally not the same length therefore causing excessive buffer travel - that is why it is bending that detent like that."  now, I did replace the buffer tube, but before installing it i measured their tube and my new tube, there was 1/8" internal difference so i installed a thick plastic washer to even out the depth difference on my new tube. the I.D. measurement of my new installed tube is .05mm smaller than their original tube and fits the buffer nicely. the buffer should stop tight against the BCG and never contact the detent during operation..? correct? is it even possible for a buffer tube to control how far forward a buffer travels? it should always come to rest against the BCG, or am I wrong about this? my BCG is flush with the rear of the upper / as is my AR15 i compaired it to. I suspect the detent hole is out of spec / drilled to far back. Pro2a Tactical is telling me "you modified the weapon to your liking and it was likely your modification that caused the problem." are they just blowing smoke up my ass? |
| I think you may have figured out the answer to your questions already. The retainer hole in the lower is supposed to have a 6 degree lean towards the front so a slight lean in the pin is normal but of course the denting on the outside buffer edge and any bend in the pin is not. |
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Granted that back of B/C or if single piece bolt in this case if blow back system, should be flush with back of the carrier when B/C-bolt is touching the barrel extension, which should push the buffer back off the buffer retaining pin, when the upper is locked home on the lower. So on that note, good look at back of B/C/carrier seated against barrel extension would help to see if something there is out of spec that needs to be solved on upper assembly/why back of BC or bolt is not pushing buffer back off buffer retainer pin. So here, need to see through ejection port window for how far the back of the barrel extension comes back, as well as the back of bolt to back of upper receiver when it seated against the barrel extension in upper, to see if problem is there instead. Or, could just be that buffer retainer channel was not drilled enough forward in receiver, and off set buffer retainer pin to move tip of pin forward, to so buffer is moved back enough of pin when upper is closes, to not contact pin during cycling.  "If you did not change the buffer and spring then it’s your buffer tube. I suspect it is internally not the same length therefore causing excessive buffer travel - that is why it is bending that detent like that." And calling bullshit on the above statement, since back of bolt in upper, should be pushing the buffer off the retainer pin when upper is locked home to lower receiver, and now way for buffer to move enough forward enough to contact the pin. So either buffer retainer pin channel too far rearward in the lower, Or the barrel extension in upper barrel socket or bolt not long enough, and it not able to move the buffer off the retainer pin is the channel is correct in the lower receiver. Granted that adding a receiver extension with deeper void, and not spacing the back of tube void if using the same buffer and spring, can allow the bolt to come back far enough back farther to break the lower receiver at is ring for the tube, when upper part of the bolt crashed into the threaded ring from over extracting farther back, it not going to allow the buffer to move any farther forward, since that is dictated by bolt against face of barrel extension And just a tangent, if you are going to use receiver extension shims, the shim has to be between the barrel nut and the front of the barrel extension on the muzzle side; not on the face of the barrel extension socket side.  You put a shim in this gap, then this means back side of barrel extension is going to be more forward in receiver void, bolt or B/C rear end going to be farther forward in upper, and will not push the buffer off the buffer pin when upper is locked home. The other thing that comes to mind, is barrel nut is coming loose, allowing the barrel extension to move more forward in the receiver to gap it against the upper barrel socket face/back of bolt now more forward in the upper with bolt against barrel extension back face, and this this may be the reason that the back of bolt is not able to move the move the buffer off the buffer retainer when the upper is locked home. |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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Originally Posted By RD20: If you have a large enough micrometer, the carrier should be 6.672 ± 0.005 inches. Make sure that yours isn't too short. Only works, when the back of the barrel extension protrudes in the upper receiver cavity the correct distance, so back of carrier (single piece bolt in this case) is correct distance to rear of upper receiver back end to push the buffer off the buffer retaining pin, when the upper locked home on the lower receiver. So again, need photo of upper receiver with bolt removed, from both the ejection port window, and from bottom of lower receiver, to get an idea of the barrel extension protrusion into the upper, then photo of single piece bolt in upper,and it back end to back of upper receiver. Granted that still want to check to make sure that one piece bolt is correct length, but want to make sure that barrel nut is not loose/not allowing barrel extension mating surface to gap to front of upper receiver barrel socket front lip, which could be causing the problem instead. Since is seems that you may not have the experience, much less the needed machinery to solve the problem if items need to be faced, may be time to just take the rig to Pro2A Tactical so they can check it out, and either send it back in, or have a local smith resolve the problem instead. |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
i stipped this little guy today, detent is bent, no other damages found there. i removed the handguard and checked the barrel nut = tight / no issues found there. photo's of inside receiver front from below.  with bolt istalled  from ejection port.  with the bolt installed, the bolt just barely extends out the rear, past the receiver. seems to be pretty good?  is there a measurement for the buffer detent hole? like center of hole to some other point i can measure to? p.s. are my photo's loading on site for you? or do you need to click on to see? i'm useing a new host. |
| Might be max distance something like 6.940" center of retainer hole at top to the center of front pivot pin hole "vertical center line up from pivot hole to same height as top of the retainer hole to get a straight horizontal line measurement ". |
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Problem is right here, with not enough of barrel extension protrusion back into the upper receiver void. If could be that the barrel extension from seating lip on it stop collar for upper receiver barrel socket, to back face of chamber section is too short. Or it could be that upper receiver barrel extension socket front lip is too long off inside back wall of upper receiver is too long , and barrel socket front surfaces needs to be squared and set back instead. Or as stated, could be barrel nut is coming lose,and this is allowing the barrel extension seating lip surface to gap to front of barrel extension face instead. Simply, when looking in from the side of the ejection port, the back of receiver extension face should be very close to the front of the ejection port window edge, which is not in this case in the above photo. As for lower receiver, below is a link to download drawings, to see if buffer retaining pin is drilled in the correct location on the lower receiver. https://cdn.shopify.com/s/files/1/1067/2310/files/AR15_Lower_receiver_blueprint.pdf?3587052860788957110 Simply, time for the upper to be broken down to check/remove barrel nut, make sure there is no derbies/barrel extension seated all the tight against the front of the upper receiver barrel socket, and it is, then front of upper receiver barrel socket needs to be lathe faced back to get correct protrusion of back face of chamber of barrel, to the it correct position in the upper receiver to semi bring the built upper back into spec.   Note, if the idea is to play dress up on the upper with different barrels over time, then maybe better to face the barrel extension seating surface towards muzzle, to semi bring the upper into spec/ the protrusion of the barrel extension chamber face inside the upper receiver void to to correct dimension of the needed slight protrude. Hence the single piece bolt striking the back of barrel face is normal (steel against steel), but if the protrusion of the face of barrel is not back enough off the front inside wall of the upper receiver, then bolt can start to peen the aluminum wall of the upper, to cause all kinds of problems. So in the above photo, notice how the back face of barrel extension is recessed in from inside surface of upper receiver back wall, and it should be the other way, with face of barrel every so sightly proud past that wall instead. --------------------------- As for buffer, and maybe even back of single piece bolt, not seeing any burs on the back of the bolt that is causing any problems to the buffer face, so buffer just needs to be checked up lathe to clean up the peen marks, and do a slightly edge chamfer of it in the end. Then at that point, it back to checking the actual stroke of the rig, but doing a full charging handle pull, and make sure that the face of the bolt only retracts past the bolt catch by 1/8~1/4", and that the last of charging handle pull the same in tension from middle of pull, to last of pull. If the bolt is allowed to come back past the bolt catch more then this, then will just be a matter of time before the bolt catch is broken. If bolt comes back past catch slightly more then this the above, then you can pull the buffer and spring, drop a quarter or two down the buffer tube as end of stroke spacers, to limit how far the buffer/bolt can retract in the tube. If way more than this, and the bolt is retracting back past the back of ejection port window, then time to get a buffer spacer the needed thickness, to use in the end of the buffer tube instead.  |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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Originally Posted By j3_: If the upper is in spec Its not, since you can see that the back chamber face of the barrel extension is recessed, not slightly proud of the back wall face of barrel socket of the upper receiver. Myself, would be the first that gets resolved, before single piece bolt starts to peen the hell out of the upper receiver aluminize face wall to start with (hence have lathe and not afraid to use it). With that resolves, may not need to go to off set buffer retaining pin, but as soft as the metal of the buffer appears to be, would still go with off set buffer pin, even with the back of receiver extension spacer'd correctly so bolt is not breaking bolt catch next. I bring the later up, since run 9mm major through the 9mm sub guns full time, and in regards to 45 carbine rigs, lets just say the same +P ammo that is used in my defense rigs as well. Note, the 45apc has a much lower working pressure than 9mm, even when both pushed to +p/major level, so really talking about a 124gr bullet in the major ammo that is pushing 2K fps in say a 14.5", verses the 230gr than is no where close to that speed with way more drop at yardage, so really comes down to the 45acp only being better if going to load to sub sonic speeds with suppressor in play instead. Also to add, on a blow back action sub guns with the hotter ammo at +p levels, need to run a heaver buffers (and in some cases stronger recoils springs as well), to control the stroke with that hotter ammo in the first place. So don't run such in rig, if rig is only set up to run standard ammo. |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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Originally Posted By Dano523: Its not, since you can see that the back chamber face of the barrel extension is recessed, not slightly proud of the back wall face of barrel socket of the upper receiver. https://i.postimg.cc/g0cD9XRf/DSC-0090.jpg Myself, would be the first that gets resolved, before single piece bolt starts to peen the hell out of the upper receiver aluminize face wall to start with (hence have lathe and not afraid to use it). With that resolves, may not need to go to off set buffer retaining pin, but as soft as the metal of the buffer appears to be, would still go with off set buffer pin, even with the back of receiver extension spacer'd correctly so bolt is not breaking bolt catch next. I bring the later up, since run 9mm major through the 9mm sub guns full time, and in regards to 45 carbine rigs, lets just say the same +P ammo that is used in my defense rigs as well. Note, the 45apc has a much lower working pressure than 9mm, even when both pushed to +p/major level, so really talking about a 124gr bullet in the major ammo that is pushing 2K fps in say a 14.5", verses the 230gr than is no where close to that speed with way more drop at yardage, so really comes down to the 45acp only being better if going to load to sub sonic speeds with suppressor in play instead. Also to add, on a blow back action sub guns with the hotter ammo at +p levels, need to run a heaver buffers (and in some cases stronger recoils springs as well), to control the stroke with that hotter ammo in the first place. So don't run such in rig, if rig is only set up to run standard ammo. The location of a reduction means nothing. The full smaller bore is allowed the full length if a maker chose too and even if they went to the allowed larger bore the reduced bore is required past the max barrel extension length at least .145" up to any point they chose. What you are visually pointing out is meaningless only actual measurements matter. |
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GREAT INFO GUYS! thanks alot. i appreciate all the insite given. and j3_ thank you for sharing. this has given me way more to go off than Pro2A has done. with the lower blue print measurements i found the detent hole is located .019" rearward. maybe with the combination of the upper's barrel extension and the detent location, these may be my issue. my offset detent should be here anyday, and off for another range test. p.s. speaking about ammo. I'm using 193gr reloads at sub speeds with a can. no +p's here. it has a 8oz buffer and spits cases out @ 2-2:30 without the can on. planning on upping the buffer weight soon. |
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Originally Posted By thindude: GREAT INFO GUYS! thanks alot. i appreciate all the insite given. and j3_ thank you for sharing. this has given me way more to go off than Pro2A has done. with the lower blue print measurements i found the detent hole is located .019" rearward. maybe with the combination of the upper's barrel extension and the detent location, these may be my issue. my offset detent should be here anyday, and off for another range test. p.s. speaking about ammo. I'm using 193gr reloads at sub speeds with a can. no +p's here. it has a 8oz buffer and spits cases out @ 2-2:30 without the can on. planning on upping the buffer weight soon. Just a fyi, but before you change out the buffer, drive out the buffer bumper roll pin, and see if there is any internal dead blow weights inside the buffer. Hence on the first full auto ar-15 rifle, the rifles did not come with a dead blow effect type buffer (just a plastic limiter piece of nylon to stop the bolt is the correct position behind the bolt catch), meaning no internal weights that would allow the back of stroke of the buffer to have a stall time, before it would allow the bolt to start moving forward, so ejection path on the first rifles was forward, not the 5:30 of the later A1+ rifles. Hence that the dead blow effect of the buffer was really to slow the auto fire rate of the rifle in the first place, with change is ejection path to now rear'ish was just coincidence of the dead blow effect to slow down the cycle rate, and Goverement had to issue snap on defectors for left hand shooter on these first rigs pre A1 rigs, so anyone shooting the rifle left handed would not get spent brass back in the face; until the updated A-2 receivers came out with defectors on the upper receivers.  I bring this up, since a quick search of the ar45 buffers, shows most of them solid, without internal dead blow weights, and even a heavy buffer if the same design solid, is still going to end up with spent case throw forward, since buffer will not have any internal buffer weights to allow the rear of stoke stall, and where the spent case are ejected off the bolt face to that 5:30 postion. https://jtactical.com/products/45-buffer-and-spring The second one, is that if the buffer does have internal weights, on a blow back action, the weights need to be spring loaded/kept forward in their cavity, to keep the weight forward in the buffer, to keep bolt forward as long as possible as well. Hence floating weight in buffer for a DI type action, rig aimed upwards, has the weights back in the buffer cavity , and until the buffer moves enough to get the weights forward again to help slow the bolt moving rearward at that point, you can have the case side walls expose enough out of the chamber walls at intial ingnitionto have a case blow out if the case walls have been thinned with enough reloading of the case. Or enough budging of the case just above the rim webbing over and over again, that with enough reloads on the cases, the case rim/lower web section just end up with head separation instead .  So since the rig is cycling now fine, it may not be a heaver buffer that is needed to get the case to eject rearward, but one that does have dead blow effect weight if your buffer is solid now, and again since a blow back action, then something like the MGW reduced rate buffer (about 10oz) that does have the internal weights spring loaded forward. Another option, maybe be a hydraulic buffer, since again, will create the back of stroke stall of the bolt so spent case can be ejected to the 5:30 position off the rearward stalled bolt face at ejection, and full internal weight of the buffer is forward at all times to keep bolt on barrel face as long as possible before it starts moving rearward.  https://c3junkie.com/?page_id=325 And to point out, since most of the blow back bolts now have ramped bolts, the hammer down against the back of the bolt, offers a lot less help of holding the bolt forward via the hammer on the back of the bolt during ignition, then the old Colt type flat back none ramped bolts isntead. None ramped bolt,  Ramped bolt,  |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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I pulled the roll pin on the buffer, it is a solid body / no weights inside. i've been researching a bunch of blowback9 and c3junkie's info before i even got this firearm. the work they do and info they share is awesome! they're 1 reason I've gone flatwire in my AR15. I've heard and seen some pics of the out of battery issues with the blow backs. but i bought one any how.  the moving weighted buffer will be my next replacement part. i think this would also help if i go frt or Super with it.I wanted to run a couple hundred rounds through this first to be sure everything cycled good, then i found the detent issue. I'm just try'ing to break it in, not break it first. thanks. |
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Yep, hard to incorpated a FP block on a single piece blow back bolt, since unlike the two piece gas system bolts, that if the bolt is not cam'd all the way into the lock postion, tail of FP is not protruding out of the back of carrier, to block the hammer from driving the FP all the way forward to ingite a round in the first place. But, that problems has been solved for the most part, via to the cmmg delayed blowback system with two piece carrier and bolt, and until the bolt is locked into the barrel extension to cam over in the cam pin slot/carrier tight against back of recoil extension, FP can not full produce out of the bolt face on hammer strike. Also, since delayed blow back unlocking, tend to keep the action cleaner/less blow back into your face when suppressed through charging handle slot than blow back action, and reduce felt recoil since does not need as heavy buffer at blow back as well (reciprocating buffer mass is where you get all the felt recoil in the first place. https://youtu.be/yfjiGrYiojM So if already running glock mags in lower in 45, then if it does come time for a barrel (and bolt change), or just getting tired of breaking hammer and trigger pins, may want to think about the switch over at that point to the gassless CMMG delayed blowback system via barrel and bolt swap. https://cmmg.com/radial-delayed-blowback-parts |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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Originally Posted By thindude: more great info, thanks. i haven't heard about broken hammers or pins yet.. ? common issue? Yes, the bolt ramping is to try to help reduce the amount of pressure that the hammer pin is going to see as hammer is slung back as the bolt comes back, but at the same time, this reduces that amount of force that that the hammer is holding the bolt forward as well. So with blow back, not a matter of if, but when your going to break at least a hammer pin. So semi solution to the problem, is anti walk pins. Not that your not still going to break a hammer pin, but when it does happen, rig is not taken out,since end bars are still holding the snapped pin in place to allow the rifle to still function.  And the funny one, is that the kits are kind of sold for the 223 that don't have the problems, since the kits for the blow back action, should come with a couple of extra trigger pins from the start (the trigger pin is the one with the groove in the center off the pin). So granted that you can save a few bucks on getting the reforce pin kits from some supplied, but if they don't offer just the extra replacement hammer pins, then may want to just order from the producer, so your not each the shipping cost of getting a few extra hammer pins at the same time. And note, on the radial delayed blow back, since its slowing down the initial rearward movement off the b/c at ignition, it should also greatly reduces the chance of breaking the hammer pin as well (maybe, since still need to do some torque tests on the system, running 9 major ammo in the first place through it). |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
If straight blowback with the bolt hitting the barrel on a chambered round....I'm betting the OOB you had was in rapid fire. The combo you have describe ensures that Bolt bounce is an issue, would need to measure cartridge protrusion, bolt pocket depth hand what spring you are using with the solid buffer to make suggestions. I run an 11.5 ounce buffer with moving weights and a standard 5.56 carbine spring with blowback 45's.....and I have built one or two with out issues over the years. As far as broken hammer pins in blowback guns.....if properly balanced it isn't an issue. With my very first blowback 45 I broke hammer pins and bolt catches with the prototypes...once I got the bolt/buffer mass and buffer length/design sorted.....don't remember breaking one in the last 15 + YEARS....and I know that is at least 35 to 40 thousand rounds as I test fire all the uppers I build, and own probably 5 different configuration blowback guns personally in 45 ACP alone....not sure how many 9mm's I have now. Rudy |
Manufacturer specializing in both DI and Blowback pistol caliber uppers. www.maconarmory.com
45 ACP, 45 Win Mag, 460 Rowland, 10mm, 40S&W, 9mm and 7.62 Tokarev.
45 ACP, 45 Win Mag, 460 Rowland, 10mm, 40S&W, 9mm and 7.62 Tokarev.
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i received my offset pin, wasn't happy with it. it seemed the offset pin was too thick to fit in the buffer tube slot properly, when i left it stick out of the slot it had enough room to rotate and possibly make contact with the bolt when cycling. so i took the original retainer pin "the bent one" cut it off flush, drilled a offset hole and installed a harden roll pin. https://i.postimg.cc/3RkjXdJj/DSC-0134.jpg i smoothed up the buffer edges, colored it with a black sharpy marker and fired off approx. 75 rounds = no issues / no more contact. however, i've been noticing the ejected cases look like this, they all have flat spots https://i.postimg.cc/8CtfnDny/DSC-0126.jpg when the bolt cycles back, the shell hits the ejector tab and the shell turns out the ejection port and slams hard against the outter part of the receiver causing the case to flatten. it's leaving a brass discoloration on the rear of the ejection port. is this common? i've ran the cases through the reloader, they've all straighten out fine, took bullets and re-crimped nicely. but i'm guessing the case mouth will split eventually. |
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Yes, no, maybe on the spent cases. What you have, is as the bolt is coming back, the ejector is going to tag the rim of the case to defect it off the bolt face, and so it all comes down to the ejector face really in the first place, that is knocking the spent case off the bolt face.  So from the start, you want the ejector to be riding as close to the bolt face in the channel of the bolt, but not binding on that channel side face. The ejector is hardened, so it if need to be tweaked, then heat will need to be evolved with it out of the lower receiver. Once that is correct, then we get into of the voodoo of 1911 ejector face beveling, so instead the the face of ejector being squared, its edge beveled to final roll the case off the bolt face (not just hard slap it off without control), with angle direction of entire face also tweaked so spent case is out center of ejection port as well. As for the case mouths being slightly dented now, not the end of the world, since sizer will correct that when cases are being reloaded. So on that note, need photo of where cases are tagging upper now, as well as a photo of bolt pulled back via charging handle until ejector is flush with bolt face, to see what kind of gap to inner side wall of bolt the ejector has now, and the angle of the ejector face to tram line of bolt face as well. Granted 9mm with hook ejector, but gives you the idea of what I want to see between ejector and bolt face on your rig.  |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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heres a pic, the ejector is square cut / no beveling or angles. appears to fit up pretty nice - no big gaps like your sample picture? the ejection pattern is all over the place, between 2 through 5 o'clock, it spits brass every where. https://i.postimg.cc/Rh9rdmBg/EJECTION-PORT.jpg |
 Ejection path out of the ejection port a touch high, but live-able. I say live-able, since if you lower the ejection path out, more of the thicker side wall protrusion of the upper receiver that the cases will needed to over comes instead. See inner ejector inner edge where finish as been worn off ejector, that edges needs to slightly chambered with diamond file to start with, and maybe even upper face of ejector on high side slightly cant angled as well, so spent case is more rolled off bolt face via extractor and ejection, verse the hard single point that the ejector edge is doing to just hard single point slap the spent case off the bolt face. As for how thick that the ejector port outer protrusion at back of window protrusion, not sure your every going to get the spent cases to clear that with the best of ejector tuning, even with longer ejector, and may just have to resort to sticky back Velcro strip on that edge, to soften the blow of cases as they tag that edge out. Hence way upper with wider ejection exterior surface is set up, since its designed to be a gas deflector to start with, and going to be very hard to tune the upper for brass not to tag it as well on the way out. Colt 9mm upper with gas deflector,  
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Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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