I’d like to buy some taper pins for pinning low profile gas blocks. The standard A2 FSB pins are too long for my liking (and they interfere with the DD Lite rails). I’m surprised how hard it is to find these little guys. I’ve been able to find several places that carry the standard, longer ones, but not the shorties.
My BRDE fixture came with two. I took measurements off of one and found this to be my closest fit. Can anyone confirm I have the right pin before I order some? Or maybe suggest an alternative vendor?
These are 3/4" long. I think I measured my standard A2 pin at around .8xx". I measured the pins that came with my BRDE jig to be .127" x .140" x .668".
That is the same pack that I bought. Mine measure right at .750". I’m not sure if that is short enough to fit under a DD Lite rail?
You can go with a shorter taper pin if you are having clearance issues with the DD Light rail. I had a Vltor low-pro block that was pinned with a shallower taper pin (non-2/0 taper) that was just over 0.50" long. It was about flush with the sides of the GB when installed, but was a pain to get in and back out again. I had plenty of clearance under my rail, so I retrofitted it with the 3/4" long 2/0 pin using a hand taper reamer. The 3/4" pins are quick and easy to get in or out as there is a little tip protruding on each side (no punch needed, just hit it with the gunsmithing hammer).
So trim to length with a grinding wheel and eyeball the radius on the end?
I’m going to do some more searching to see if I can find out the hardness of the mil spec taper pins vs the 85 Rb that is shown on the McMaster-Carr website. I thought taper pins were supposed to be hardened. 85 Rc is not very hard at all. Green carburizing steel should come in around the mid 90s (~17 Rc). With this said, did you have any issues with it wanting to mushroom on you?
I trim with a thin cutoff wheel, then chuck the pin itself in the Dremel and radius with fine multipaper or whatever fine abrasive is closer to put a nice round head on it. Just make sure you set the pin to it’s final depth before trimming, or you can easily end up cutting too short. Also keep in mind that they don’t need to be driven in with Thor’s hammer- one stiff blow from a light ballpeen is all you need.
As to hardness… ? I’ve never heard anyone go there, for taper pins for gas blocks. I certainly don’t know everything, though. Pins will mangle from every manufacturer, if they’re too tight. On removal, anyway- if you drive them in right, they won’t mangle on install. I think you can buy them now, but long ago I concaved the tip of a 1/8" drift specifically for tapping rounded taper pins… keeps them clean.
I’ve removed 3 or 4 BCM FSBs. I could tell you that if those were as soft as I think these McMaster pins might be, I’d be afraid that I’d mushroom the small end and then I’d never get them out. But even after taking a beating, BCM pins showed zero deformation.
Not sure on the hardness issue, but I had no issues with the pins deforming. I installed and removed one several times during the reaming process with no deformation that I could notice. I used a brass tipped gunsmith’s hammer on the pin. Worst I’ve experience is getting a tiny dimple in the end of a S.S. pin because I removed it with a steel roll pin punch instead of a standard flat-faced punch.
They do, I have several, but they are longer for an A2 FSB, and too long when slipping a Lite rail over. I was looking for an easy way out that does not include me grinding pins to size. But maybe that would be the way to go.
Edit - If you’re worried about the hardening- the whole pin will be hardened through. “Case hardening” is for specific applications, and couldn’t even be applied to something as small as a pin… the whole thing is hard, if it’s hardened at all.
That’s a good point. I guess the purpose of this whole thread was to just learn what options were out there. I’m just going to take the hardened BCM pins and grind them down to desired length.
I’m new to it. I’ve only done 2. But I’m using a Brownells hand reamer. Slow, but very easy to get it just right. If you’re constantly power reaming, I could see easily reaming too far.
