For many years Colt 9mm AR owners have added a ramp to the bolt prevent wallowed out lower holes.

I recently noticed my 22lr bolt from CMMG has very little ramp and it contacts the hammer much closer to the axis than a 5.56 bolt. I plan to use this bolt on a SBR lower. Should I keep an eye out for premature wear of the hammer pin and pin hole due to the lack of a ramp, or is this not an issue for low power 22lr?

22's are known for breaking pins. Not as bad as 9mm probably due to much less mass in the bolt, still, it happens. I don't think egging the pin holes is a big concern, just in case I use KNS pins on my lower

I've always thought KNS pins are a gimmick but now I understand their usefulness on blowback guns. Standard hammer pins have a groove in the middle which is where they often break. KNS pins don't have that groove so they're less likely to break.

Unfortunately I had planned a Geissele trigger for this build, they advise against KNS pins. I'll need to find another trigger.

I never used KNS pins until my dedicated 22 and then 9mm build. I had read of enough broken hammer pins to know that the solution was KNS pins and ramping the bolt in the case of 9mm. I only use KNS pins on one of my 5, 5.56 AR's. This is only because that lower has a CMC drop in trigger, the "anti-walk" pins that came with the trigger assembly were less than optimal..

Having said this, I wouldn't give up a nice trigger in favor of KNS pins.. carry a few spare pins Also, I think one of the 2015 shot show rumors was Geissele is working with KNS to make pins that meet his standards.

BTW, my dedicated 22 has a RRA varmint 2 stage trigger using KNS .1555 pins, pull is right at 3.5lb, I'd say its VERY close to my SSA-E. My 9mm has a stock trigger with JP reduced power springs and standard .154 KNS pins. Pull is about 4.5lb and I lucked out that this OEM FCG had very little creep or gritty feeling... not as nice as a higher dollar trigger but good enough.