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Posted: 12/5/2009 2:25:07 PM EDT
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Finally shot my October special 7.62x39 upper. I had the BCG chromed by Metaloy (excellent work BTW) for easier cleanup, switched out the goofy-ass FH that came with it for an A2 6.8mm one, and had the upper Duracoated Colt Gray. Got it all done and went to try it out.
Motherfucking sonofabitch!!! 
Short-stroking out the ass, with a few failures to eject (which are probably related to the short stroking). Also had several light strikes, even though the primers looked like they got a decent hit. Between all the problems it never got two rounds in a row off. It was Wolf ammo and the lower was my S&W 5.45x39 lower that has the extra power hammer spring in it already. I got pissed and threw the mag, which dented it up pretty good. *Almost* wrapped the upper around a tree but thought better of it. I have a shitload of $$$ sunk into this POS already so I had to get it working. My buddy is a gunsmith so I went over to his shop and he saw the look on my face. He was the one who Duracoated it so he knew I was chomping at the bit to break it in. He also knows my fuze is short and when he saw the mag he shook his head and laughed (fucker). We ended up removing the FSB and opened up the gas port the next drill bit size. Of course this fucked up the Duracoat on the barrel but WTH can you do? So now cycling is not an issue, but still getting light strikes on Wolf ammo. Tried some of the Hornady 7.62x39 I bought and it fired the 4 rounds I loaded with no issues which I thought was odd as Hornady uses Russkie steel cases (maybe their own primers? I dunno). At any rate, FUCK BUSHMASTER and what they were no doubt going to say if I called: "Send it back in". I hate packing shit up and running to UPS, then of course waiting for them to send it back *possibly* fixed. For the $600+ I spent on the damn thing it oughta work right as is. This really fucking pisses me off. I have a feeling their ignorant asses would have spewed some shit about voiding the warranty by having the BCG chromed and the upper Duracoated. So, now that I have voided the warranty by opening up the gas port on my own, what can be done about the hammer strikes? Like I said, the lower I used already has a stronger hammer spring and it actually looks like the primer got a decent whack. My buddy fired the light-strike rounds from his AK just to make sure they weren't dud rounds and they worked fine in the AK. I have no intention of buying brass cased stuff as this upper is useless to me if it won't shoot Wolf. Aren't there special firing pins for 7.62x39? Also, isn't there a mod you can do to the firing pin so it protrudes more? One more thing: how many 7.62x39 rounds can you reliably load and fire from a 20 or 30rd 5.56mm USGI mag? Thanks in advance. ETA––-I've been told not to mess with a 7.62x39 AR, that it was destined to fail. Lesson learned from the school of hard knocks. However, my 5.45x39 S&W works fine. Go figure..... |
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I am surprised that you didn't have mag problems. I think that once you fixed the other issues, you'd run in to mag issues. Was the mag CProducts? Was it empty when you threw it? Not surprised that it was damaged just from that. It was a Bushmaster mag but I'm told (by ARFCOM) that they're made by C-Products. It had maybe 10 rounds or so in it when I chucked it. *If* I get any more C-Products mags I'm gonna get the Wolff 5% extra power springs for them as one ARFCOMer did this and said it fixed his mag problems. Still gotta deal with the light(er) strike issue. |
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Quoted: Quoted: I am surprised that you didn't have mag problems. I think that once you fixed the other issues, you'd run in to mag issues. Was the mag CProducts? Was it empty when you threw it? Not surprised that it was damaged just from that. It was a Bushmaster mag but I'm told (by ARFCOM) that they're made by C-Products. It had maybe 10 rounds or so in it when I chucked it. *If* I get any more C-Products mags I'm gonna get the Wolff 5% extra power springs for them as one ARFCOMer did this and said it fixed his mag problems. Still gotta deal with the light(er) strike issue. Better springs might fix feeding issues, but the body of the mag is still weak... |
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Is it possible the the chrome on the BCG is too thick and causing it to hang up? This is just a stab in the dark question because I've never considerend and after market chrome job. Yes it is. It's possible there are uneven points. Its possible the gas key may have not been properly reinstalled. But of course, the assumption is that Metaloy was on their A game that day and Bushmaster wasn't. I wonder if his smith knows the correct spec for the gas port and verified that it was out of spec, of if he just took a fucking drill bit to it. Yeah, this thread has fuck Bushmaster written all over it 
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Is it possible the the chrome on the BCG is too thick and causing it to hang up? This is just a stab in the dark question because I've never considerend and after market chrome job. Yes it is. It's possible there are uneven points. Its possible the gas key may have not been properly reinstalled. But of course, the assumption is that Metaloy was on their A game that day and Bushmaster wasn't. I wonder if his smith knows the correct spec for the gas port and verified that it was out of spec, of if he just took a fucking drill bit to it. Yeah, this thread has fuck Bushmaster written all over it
Nope, don't know the spec of the gas hole but he has a set of fine 'smithing bits and found one that barely fit then went the next size up. It apparently worked. The BCG moves smoothly with no binding. You can flick the wrist and the bolt pops forward like with a USGI one. My S&W 5.45x39 BCG has also been to Metaloy and it works fine. Is that really so hard to believe? Oh, I MOAK'ed the carrier key before I sent it to Metaloy and it was the same on return; IIRC last time they told me they didn't remove it (?). There is another thread on here as well as on TOS that has some good, some bad reports on the Bushy uppers. My luck of the draw is why I don't gamble. 
So, any tips on the strike issue? How about the USGI mag and 7.62x39 capacity? |
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The firing pin should protrude .029-.. 035, the bolt should be 2.800" long if it is longer the firing pin hits the back of the bolt and comes up short.
A quick fix is to take a few thou off of the tail of the bolt but only a few thou. then shoot it to test. If you take off too much then the firing pin could pierce the primers. Someone does make a thicker firing pin, close to AR10 size. With the mags there is a easy tweak to keep the front of the follower from diving, bend the front spring loop up or the hook down so when the spring is held straight up the front loop touches the front of the follower at the same time the hook does, the follower should be level. check this thread. It is for a 6.8 but the principle is the same. Some springs are formed better than others and are close to touching the front of the follower. BTW typing paper is .004" thick so you only want to remove about half of that from the rear of the bolt at a time. http://68forums.com/forums/showthread.php?t=9593 |
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Quoted: The firing pin should protrude .029-.. 035, the bolt should be 2.800" long if it is longer the firing pin hits the back of the bolt and comes up short. A quick fix is to take a few thou off of the tail of the bolt but only a few thou. then shoot it to test. If you take off too much then the firing pin could pierce the primers. Someone does make a thicker firing pin, close to AR10 size. With the mags there is a easy tweak to keep the front of the follower from diving, bend the front spring loop up or the hook down so when the spring is held straight up the front loop touches the front of the follower at the same time the hook does, the follower should be level. check this thread. It is for a 6.8 but the principle is the same. Some springs are formed better than others and are close to touching the front of the follower. BTW typing paper is .004" thick so you only want to remove about half of that from the rear of the bolt at a time. http://68forums.com/forums/showthread.php?t=9593 what he said. I had light primers strikes and the only thing i changed was I got a MGI bolt and firing pin the firing pin is a bit beefier and makes a bigger strike on the primer and it pertrudes out a little further since then I never had a light primer strike again my trigger is a RRA NM 2 stage and has worked fine since the bolt change. I bet your having the same problem I also had problems from time to time with a round sometimes hitting the upper reciver just below the feed ramps. So I took a fine file and just made my own feed ramp extintions into the upper reciver like what the m4 has and never had that problem again. |
| They take some tuning, but mine has been running 100% lately. Mine was built using a Model 1 kit, uses a heavy trigger spring for the harder primers and I replaced the standard C-products mag springs with the Wolf +5% springs. I have 600 rounds through it now with 1 failure to feed from a Wolf black-box hollow point. I don't have M4 feed ramps so hollow-points can be an issue still. Good luck!! |
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I am surprised that you didn't have mag problems. I think that once you fixed the other issues, you'd run in to mag issues. Was the mag CProducts? Was it empty when you threw it? Not surprised that it was damaged just from that. It was a Bushmaster mag but I'm told (by ARFCOM) that they're made by C-Products. It had maybe 10 rounds or so in it when I chucked it. *If* I get any more C-Products mags I'm gonna get the Wolff 5% extra power springs for them as one ARFCOMer did this and said it fixed his mag problems. Still gotta deal with the light(er) strike issue. Better springs might fix feeding issues, but the body of the mag is still weak... I have two that have sat loaded, with the heavier springs, for a couple weeks now...not seeing any issues with them yet. However, C-Prod is also saying that the new gen mags are "100% reliable..." Not sure what they changed, but I'll pick a couple up and see if they are any better... http://www.ar15.com/forums/topic.html?b=2&f=216&t=181457 |
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Hmm..., I've got a Bushy 7.62x39 barrel inbound so I guess I'll find out for myself soon enough if the gas port's a weak link.
You might take a look at user M4FNG's experience on page 12 of the older 7.62x39 thread. Loading a standard 5.56 mag with 7.62x39 works with 5-6 rounds. While I have a C Products 30 rounder that works, I use C Products 10 rounders and USA frankenmag 20 rounders most of the time and they work just fine. While the MGI enhanced 7.62x39 bolt and firing pin combo worked with the eastern european steel case ammo, the extractor broke at ~1100 rounds and I've been unable to get a replacement from MGI. That gun got an LMT bolt and a standard firing pin as replacements. With a Geissele SSA trigger it fires Monarch steel case almost 100%, but still fails to light off Wolf about half the time. That gun has a 14.5" barrel from Model 1. It's quite accurate. |
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"I made a lot of modifications single upgrade of chroming the BCG to my rifle before I shot it and it doesn't work; therefor it is the original manufacturer's fault!" Fixed it for ya. I've had chroming done before and never had a problem. The Duracoat is a moot point as the inside of the upper was not done, so that's cosmetic. If you read what I posted above, there are several threads here and elsewhere that point to *some* people (not all) having issues with the Bushy 7.62x39 upper; light strikes and short-stroking (with NON-chromed BCG's BTW) as well as failures to extract and eject. So yeah, it rests squarely on Bushmaster. |
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Hmm..., I've got a Bushy 7.62x39 barrel inbound so I guess I'll find out for myself soon enough if the gas port's a weak link. You might take a look at user M4FNG's experience on page 12 of the older 7.62x39 thread. Loading a standard 5.56 mag with 7.62x39 works with 5-6 rounds. While I have a C Products 30 rounder that works, I use C Products 10 rounders and USA frankenmag 20 rounders most of the time and they work just fine. While the MGI enhanced 7.62x39 bolt and firing pin combo worked with the eastern european steel case ammo, the extractor broke at ~1100 rounds and I've been unable to get a replacement from MGI. That gun got an LMT bolt and a standard firing pin as replacements. With a Geissele SSA trigger it fires Monarch steel case almost 100%, but still fails to light off Wolf about half the time. That gun has a 14.5" barrel from Model 1. It's quite accurate. Thanks for the info. You and I were both in that thread. Although his wasn't a Bushy, the problems were similar. Like I said, there are a few threads here and elsewhere about Bushy uppers. It appears most 7.62x39 AR's suffer from similar maladies. Maybe it ain't designed to run out of an AR after all? 
If it wasn't so much $$$ I'd get one of those AR-47 lowers from MGI (?) that take AK mags, but then you've got to buy the carrier with the special cuts in it made for AK mag clearance. |
| Isn't there a way to remove "stuff" from the firing pin instead of the rear of the bolt tail? Like on the forward side of the firing pin flange where it butts up against the bolt tail? It basically does the same thing––-makes the pin protrude further. I'd rather adjust the (cheaper) firing pin than the (more expensive and harder to fin) bolt. |
| On my Model 1 upper, I use the MGI bolt and firing pin and have the RRA trigger installed. No heavy hammer springs. While I've not used Wolf, I have shot a lot of copper washed Chinese and East German lacquered ammo without a single problem. I also use the C Products 10 round clips with nary a hitch. So far, this combo has proven ultra reliable in my gun. |
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Regarding the firing pin modification, I'll just quote from the older thread:
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Hi guys, Im new here. I just got my AR kit from JT distributing (7 days from order to ship) last friday. Im currently waiting on the MGI bolt and firing pin. While im waiting (apparently telling the customer its shipping next week happens every week whether its shipping or not) what do you guys that have shaved some material off the 5.56 firing pin used to do so? this is the pic ive seen here.  Hepexamendios.....That mod did not work for me by removing material from the shoulder that you are showing as my Model 1 firing pin was bottoming out in the bottom of the fireing pin hole in the bolt. After ruining one firing pin, I finally determined that I had to remove material from the final taper near the firing pin tip for the protrusion to increase. I believe my firing pin protrusion started at .034" and I increased it to .041" because my AR worked with all ammo that I threw at it. I chucked firing pin into a dril press and pressed a file against the taper removing a little at a time until .007 was removed. I also use a Wolff heavy hammer spring and have a RRA 2-Stage target Trigger. My set-up is GTG. Your results may vary. I would suggest that you measure your firing pin protrusion from the bolt face before you start Mod. I used a dial caliper to measure the depth. You can see here the difference in the taper of the tip of MGI's enhanced protrusion firing pin tip and that of standard firing pins (both lower ones are standard): 
The MGI enhanced bolt has a distinctly larger hole for the firing pin: 
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There are modification you most do to run steel cased ammo in an AR-15 7.62x39. The stock gas system works fine, it's the buffer spring that must be replaced with a Wolff Springs XP buffer spring and hammer spring. I modified the stock bolt myself. I have all to skills and tool to do the job, but you can by the an aftermarket bolt or use Winchester 7.62x38 ammo. They work with no modification. The new Cproducts 5,10, and 30 round mags work, that what I use. I started to reload 7.62x39 and 223 rem, I can reload them for less that steel cased ammo and they shoot alot better. That's IMHO
Mike |
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I don't really see how this is bushmasters fault in the slightest. You made modifications to the rifle before even a function test? It's been stated all over these forums that most combloc steel ammo WILL cause problems with light strikes unless the stock firing pin is modified and or you get one specifically made for the combloc steel. For the issues on the mags, buy the AK wolf +5% springs and you should have all of your feeding issues resolved. If you want to put x39 in a 5.56 mag you can fit at most 5 without issue.
For my setup I am using stock model1sales bolt and pin with monarch steel and have yet to have issues. Stock buffer spring, unmodified CMMG 2 stage trigger as well. |
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There are modification you most do to run steel cased ammo in an AR-15 7.62x39. The stock gas system works fine, it's the buffer spring that must be replaced with a Wolff Springs XP buffer spring and hammer spring. I modified the stock bolt myself. I have all to skills and tool to do the job, but you can by the an aftermarket bolt or use Winchester 7.62x38 ammo. They work with no modification. The new Cproducts 5,10, and 30 round mags work, that what I use. I started to reload 7.62x39 and 223 rem, I can reload them for less that steel cased ammo and they shoot alot better. That's IMHO Mike this is pretty much my rub with these and other 762 uppers. 99.9% of shooter will be running wolf or other comblock milsurp ammo through them. to require the expense of a new BCG to make the damn thing run is unacceptable. why not just build it right to begin with. VERY few people are going to buy these with the intent of running winchester ammo in them. |
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If I was Bushmaster, you might just get a letter that starts: "Hello, my name is John Doe, and as attorney of record I am advising you that a lawsuit is being filed for libelous slander." Mmmmmkay......
Hope you're not giving up your day job, as it evidently ain't law. |
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There are modification you most do to run steel cased ammo in an AR-15 7.62x39. The stock gas system works fine, it's the buffer spring that must be replaced with a Wolff Springs XP buffer spring and hammer spring. I modified the stock bolt myself. I have all to skills and tool to do the job, but you can by the an aftermarket bolt or use Winchester 7.62x38 ammo. They work with no modification. The new Cproducts 5,10, and 30 round mags work, that what I use. I started to reload 7.62x39 and 223 rem, I can reload them for less that steel cased ammo and they shoot alot better. That's IMHO Mike this is pretty much my rub with these and other 762 uppers. 99.9% of shooter will be running wolf or other comblock milsurp ammo through them. to require the expense of a new BCG to make the damn thing run is unacceptable. why not just build it right to begin with. VERY few people are going to buy these with the intent of running winchester ammo in them. You hit the nail on the head. FWIW my buddy the gunsmith traded me a (slightly used) 5.56 carbine upper for the 7.62x39 Bushy upper. He is going to decide whether he wants to mod the firing pin or get a new bolt/firing pin combo. He has wanted a 7.62 upper for a while and I was more than happy to trade it to him. He will likely chuck up the firing pin in his lathe and precisely remove the necessary amount from the flange as well as taper the end so it will protrude further. |
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