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Posted: 12/31/2008 12:10:41 PM EDT
| I'm waiting for UPS to drop off my RRA 9mm upper and I'm looking for any suggestions for ways to "tune" or improve the shootability of it. Do comps work on a 9mm? Spring/buffer combo? any other ideas? Thanks |
| Make sure your ejector is as close to the center of the bolt as possible. It may be straight and not close enough to the center and just touch the edge of the case. This will cause erratic ejection and will drive you nuts. You will think it is a feeding problem, bad magazines, etc. Search here and you will find the fix, it is easy. |
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I have seen conflicting post on ramped bolts.
For example, if the rifle has a standard ar15 hammer then it is better to have ramped bolt. If the rifle is a dedicated 9mm with a 9mm hammer then there could be trigger issues with a ramped bolt. Others have said definitely get a ramped bolt. Anyone know for sure. I have a Colt 6450 mike |
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Quoted:
Great info, thanks. I did the search and found some info about adjusting the length of the ejector spring is that what you were refering to? No, the ejector itself (Olympic arms use an upper mounted ejector and spring, that is different than frame/magwell 9mm conversions). I can't find the link now either, it might have been moved to the archive or something. The idea is that a lot of ejectors are straight and not close enough to the centerline of the bolt. You need it to contact the brass as close to the center of the base (think primer area) as possible. Here is a picture of my ejector: 
Top view, you can see that I bent it towards the center of the mag well. I tried to keep it even, bending it at the base, rather than just the tip. I wanted the force from the round to push straight back on the ejector rather than forcing the ejector at an angle. I did have to bend it up as well. It is OK for it to ride the bolt a little, just make sure it doesn't slow it down or bind it up. 
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Quoted:
I have seen conflicting post on ramped bolts. For example, if the rifle has a standard ar15 hammer then it is better to have ramped bolt. If the rifle is a dedicated 9mm with a 9mm hammer then there could be trigger issues with a ramped bolt. Others have said definitely get a ramped bolt. Anyone know for sure. I have a Colt 6450 mike The ramping mimics the ramp on an M16 bolt carrier, which is not only "what the lower was designed to work with," but also reduces the stress on the hammer pin. Significantly. That little 9mm hammer has a different face profile that should work OK with the stock bolt, but unless you're NEVER going to use that lower with anything but 9mm, I'd change the hammer for a bobbed M16 hammer (aka the DPMS hammer) and have it available for any upper. |
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Quoted:
What lower are you going to use with that upper? What magazine block? In general, I recommend adjusting the Rock River block lower than it comes from the factory-down to where the magazine catch just clears the top of the cut out. That doesn't impair how it works with Uzi magazines, and should also give you a known location for when/if you remove the block for cleaning or maintenance.
I'm waiting for UPS to drop off my RRA 9mm upper and I'm looking for any suggestions for ways to "tune" or improve the shootability of it. Do comps work on a 9mm? Spring/buffer combo? any other ideas? Thanks |
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I've been running non-ramped bolts for 5+ years with the dinky little RRA 9mm hammer. The 9mm hammer has a notch in the face to mimic the effect a ramped bolt would provide when used with an M16 style hammer. The 9mm hammer also works just fine with my .223/5.56 uppers. I am a firm believer in not wasting money where one doesn't have to. I'd buy a $12 hammer any day, over spending the money on a ramp job. To each his own though.
As far as other tuning, depending on your configuration and the ammo you are using, it may be beneficial to try out different buffers (both heavier and lighter than std. 5.5 oz 9mm) and different action springs (both heavier and lighter) to find the combination that performs the best with your ammo and provides a recoil/feel that allows you to shoot best. |
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I'm sure I'll be able to figure out alot more when I have all the parts in hand and get a few range outings under my belt. I have a DPMS lower with DPMS hammer, RRA mag well wtih CP mags. I have a couple buffers and springs to try and a 9mm hammer if the DPMS doesn't work.
The ejector pictures clarified that issue for me...thanks. I'm leaning toward ramping the bolt. Having a less violent movement during the cycling has to remove some of the unneeded gun movement as well as longer reciever and trigger/hammer life. Anyone try shortening the bolt carrier rearward movement? |
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Any other threads that cover this topic?
From the pictures it looks as if the ejector has been shortened not just bent. I'm having jamming issues with FTF and FTE. Rock River upper with Spikes lower, Hahn bottom loading mag block and Spikes STX buffer. I'm going to try a RRA mag block. Also want to be sure the ejector is positioned correctly, but the picture aren't quite clear where the ejector has been adjusted. |
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