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Posted: 9/19/2012 12:55:23 PM EDT
| I just bought a RRA 9mm upper receiver to use with a Spike's Mag Block. I am wondering if I should get the bolt ramped. Does it reduce felt recoil? Is it worth having done in a gun that is semi-auto only? Thank you. Oops. Just read that M60Joe doesn't ramp semi-auto bolts. |
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Only know what I've read here, but it is my impression that the ramping is to reduce the load on the hammer pin, reducing or eliminating breakage.
Now whether this a common, really-need-to-worry-about-it problem, or only comes up with really heavy service..... this I don't know. Some here recommend KNS pins to protect the lower in the event of breakage; Colt has gone to stronger, stainless steel FCG pins as a response to the problem, tho' they run ramped bolts as well. Don't see how ramping would reduce felt recoil, which is pretty mild in any case. Moon |
| If you're using a lower with a standard 5.56 hammer, you have to ramp the bolt. If you're using the 9mm hammer you don't. No effect on recoil either way. ADCO ramped mine for $50 which is about the cost of a 9mm hammer. If recoil reduction is your goal run the heaviest buffer you can afford with a spacer. |
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Quoted:
Only know what I've read here, but it is my impression that the ramping is to reduce the load on the hammer pin, reducing or eliminating breakage. Now whether this a common, really-need-to-worry-about-it problem, or only comes up with really heavy service..... this I don't know. Some here recommend KNS pins to protect the lower in the event of breakage; Colt has gone to stronger, stainless steel FCG pins as a response to the problem, tho' they run ramped bolts as well. Don't see how ramping would reduce felt recoil, which is pretty mild in any case. Moon I can tell you with absolute certainty / first hand experience that running an unramped bolt and no KNS pins causes excessive stress on a lower, though maybe with light enough use it may never become apparent. Before I made the mental leap to mix my two hobbies (shooting and computers), I never bothered to look at anything shooting related online. I spent 8 or 9 years shooting 9mm out of my M16 with no ramped bolt or KNS pins, because I simply didn't know about the issue. Then one day I was shooting .223 and found that my rifle wasn't firing consistently. It turns out that the hammer pin holes were egging out, giving the hammer room to wiggle slightly side to side and/or twist left-right inside the lower, causing it to not strike the firing pin evenly/consistently. It wasn't a lot of play mind you, but it was apparently enough. I had to send it to m60joe for repairs. I'm thankful there are good 'smiths like him around that can/will do this kind of work, but ignorance cost me a lot of money. Never again - now every 9mm bolt I have is ramped and every NFA lower I own has KNS pins. -Raeth |
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Quoted:
If you're using a lower with a standard 5.56 hammer, you have to ramp the bolt. If you're using the 9mm hammer you don't. No effect on recoil either way. ADCO ramped mine for $50 which is about the cost of a 9mm hammer. If recoil reduction is your goal run the heaviest buffer you can afford with a spacer. If you use a std. 5.56 hammer, you do NOT have to ramp the bolt. You can run a DPMS/M16 style hammer or a 9mm hammer (possibly some others, but I'm not going to test them all) with a non-ramped bolt. If you run an ramped bolt, you should not run a 9mm hammer, but, and this is a big BUT, there are different people doing ramping to different specs and I know of some that are running certain hammers with ramped bolts that do not work with other ramped bolts, so YMMV. Just to clarify another point also - A 9mm hammer does not cost $50 - they are $15-20 at best.... Quoted:
I can tell you with absolute certainty / first hand experience that running an unramped bolt and no KNS pins causes excessive stress on a lower, though maybe with light enough use it may never become apparent. Before I made the mental leap to mix my two hobbies (shooting and computers), I never bothered to look at anything shooting related online. I spent 8 or 9 years shooting 9mm out of my M16 with no ramped bolt or KNS pins, because I simply didn't know about the issue. Then one day I was shooting .223 and found that my rifle wasn't firing consistently. It turns out that the hammer pin holes were egging out, giving the hammer room to wiggle slightly side to side and/or twist left-right inside the lower, causing it to not strike the firing pin evenly/consistently. It wasn't a lot of play mind you, but it was apparently enough. I had to send it to m60joe for repairs. I'm thankful there are good 'smiths like him around that can/will do this kind of work, but ignorance cost me a lot of money. Never again - now every 9mm bolt I have is ramped and every NFA lower I own has KNS pins. -Raeth This comes up a lot. There are plenty of people that run non-ramped bolts and std. pins and don't have issues, just as there are other folks that run ramped bolts and kns pins and have still broken pins. There is no easy way to say whether a given lower will break pins or not. The best thing to do is to run it for a bit and see what happens. If pins break repeatedly and rather quickly, your lower may be afflicted and require ramping and kns pins. If it doesn't break any pins, the money spent on ramping and kns pins may be a waste. As with anything in life, everyone needs to determine the level of risk they are comfortable assuming and how much they want to spend to mitigate that risk. For those with RR's that are worth 5 figures, expensive integrated lowers, or SBR lowers, spending $50-100 to reduce the potential for damage to it is a no brainer. As Raeth noted though, it isn't the end of the world as lowers can be repaired. The problem with egged out pin holes isn't just unique to 9mm though and is nothing new. There are a lot of folks with high-mileage .223/5.56 RR's that have worn out pin holes and required repairs. That's kind of what led to the development of anti-rotation pins that would reduce the wear to the lower and I'm sure what led some, like M60Joe, to offer some unique repairs including bushing and bearing inserts to repair worn lowers. kns also offers an oversize pin set if your lower is just a little worn or out of spec. For those with cheap Semi lowers that can be replaced for as little as $59-79, it may not make a lot of sense to pay $50-100 to ramp a bolt and add kns pins until you know if you will have any problems or not, but again, it's up to the individual to decide if they want to spend the money or not. As for felt recoil, it all depends. Some say the recoil of a 9mm is less than a .223/5.56 gun and others say it is more. I fall into the camp that believes the felt recoil of the 9mm is more than that of the .223/5.56 guns. Just my 2 cents. |
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Recoil is much more on a AR15 9m.m. That's why the MP5 is considered to be better in some circles. The blowback action will do that. The AR15 was also less than half the cost of the HK.
Ramping the bolt will save wear and tear on your lower. The standard bolt (which is for both full and semi) with the 9 m.m. hammer, are the lowest for recoil on a blowback AR. The reason is this... The mechanical advantage is "harder" with the 9 m.m. hammer. It takes more effort to cock it. Why would Colt do this, as it is WAY harder on the hammer pin ? To let the chamber pressure dwell time increase. therefore reducing perceived recoil. It didn't work well for longevity. AND it's recoil never equaled the MP5 in that regard. But the Police spend (hopefully) a limited amount of taxpayer money  . And you get more value with the AR system. 
That was the whole reason the AR 15/9 was created. AND A MOST HAPPY RESULT FOR US HOBBYISTS 
Now get those KNS pins and ramp that bolt. 
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A typical Colt-pattern 9mm AR will have a very different recoil "feel" from one in 5.56mm. Being blowback, you'll feel something more like a push than a tap, because the recoil impulse is transmitted through the bolt rather than the whole rifle. It feels longer lasting too, because of the nature of the heavy bolt and spring. With all that mass moving, you won't be able to feel any difference between ramped or unramped bolts, or heavy versus light hammer springs, or just about anything else.
As kevinsgarage has pointed out, there is little evidence that anyone "needs" a ramped bolt for a 9mm AR to be reliable, nor that either option gives better or worse longevity to the gun. The choice is a personal preference for most of us. The only thing I'd add to that is that the "9mm hammer" is a poor choice for any setup, as it has less mass and an odd face profile. I have DPMS-type hammers in all my lowers because they work with everything, and I like to keep my options open. 
I should point out that at one time Colt had a different "semi auto" bolt design, but currently available Colt-pattern 9mm AR bolts are all in Colt's "auto" style, which M60Joe will ramp. I had my RRA bolt ramped by ADCO, who did fantastic work and got it back to me quickly. I could not tell any difference in performance or felt recoil at the range between the bolt before and after ramping. |
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Just for the record, the 9mm hammer does work with .223/5.56 uppers, so if you don't ramp your bolt, you can run a 9mm or DPMS/M16 style hammer (stock or modded) and run 9mm or .223/5.56 uppers. Plenty of people have run 9mm hammers with .223/5.56 uppers and continue to do it. I think there are posts about it in the archive here from ~2004, possibly earlier...
I have run 9mm hammers, std. DPMS hammers and DPMS hammers modified to resemble JP speed hammers without issue with non-ramped bolts and I can't tell the difference between any of the hammers. They all work basically the same in my opinion. |
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Quoted:
Just for the record, the 9mm hammer does work with .223/5.56 uppers, so if you don't ramp your bolt, you can run a 9mm or DPMS/M16 style hammer (stock or modded) and run 9mm or .223/5.56 uppers. Plenty of people have run 9mm hammers with .223/5.56 uppers and continue to do it. I think there are posts about it in the archive here from ~2004, possibly earlier... I have run 9mm hammers, std. DPMS hammers and DPMS hammers modified to resemble JP speed hammers without issue with non-ramped bolts and I can't tell the difference between any of the hammers. They all work basically the same in my opinion. My RRA 9mm hammer stuck on my RRA .223 bolt the couple of times I tried it (manually), so I just went to all rounded, standard hammers. It was a matter of buying a $12 replacement hammer for my factory RRA 9mm carbine and then standard LPKs for builds. I've seen several reports of the 9mm hammer giving people problems itch .22 adapters too, though that's s different issue in my opinion. I've never tried it myself. At the moment i don't have the time to change out a hammer and try the various combinations, but I probably will check that out when I get to it, and I'll post details of what I find. |
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