I am sitting here looking over a bbl that has straight taper pins in the FSB, and the taper pins measure .125". It appears that the hole drilled through the FSB and the bbl measure .125" as well. Tim at Kotonics actually sent pins that are just pieces of straight rod (probably tool steel of some sort) that have been “peened” in the middle, in order to promote a tight fit. He calls them “peened”, but honestly, they don’t look just to be peened. Rather, if you can imagine someone smacking the middle of these straight pins, with a regular wood chisel (with the angled tip), that would be what they look like. It’s almost as if there is a little triangular shaped “chunk” that has been taken out of the middle of each pin. This of course, enlargens the pins slightly, and also puts a SLIGHT bend, or “bow” in each pin, and therefore these straight pins hold tightly in the FSB. Tim also suggests using red Loc-Tite to help hold the pins in.
I honestly would much rather use taper pins in this setup, and I think it will be very possible to do so. In fact, the Colt taper pins that I have in a 6920, also measure .125" at the SMALL diameter end of the taper pin. SO, I’m thinking that it will indeed be possible to convert this bbl and FSB to use taper pins.
I have just a couple questions as follows:
On a taper pinned FSB (such as on a Colt 6920), are the holes drilled with a regular .125" bit, thus resulting in a STRAIGHT, PARALLEL hole? OR, is some type of special tapered bit, or tapered end mill used, in order to produce a TAPERED HOLE? IF a truly TAPERED HOLE is needed in order for taper pins to work properly, I think I could convert this bbl over to taper pins, since the diameter of the Kotonics drilled hole is .125". (.125" is the small-diameter of the taper pin)
I just want to know if Colt drills some type of tapered hole, or if they drill a .125" hole, and just kind of “force fit” the pins in (for lack of a better term)??
IF indeed I must redrill/mill this bbl and FSB, to create a tapered hole, then what type of drill or end mill is used to drill the tapered hole? I have seen somes sort of tapered drills before, but I don’t know if there is a special size I need, or if there is something else I need? I would assume a cobalt cutting tool would be best, but not totally necessary. HSS will work, but cobalt is always stronger IMO.
What do you guys think? Anyone ever converted a straight pinned FSB/BBL combo, over to a taper pinned setup?
I know it’s quite possible. Just looking for some pointers. I would just much rather tap taper pins in and out, when I want to disassemble my gun, INSTEAD of having to deal with red loc-tite and bent pins (which aren’t even black finished BTW). These Kotonics straight pins are shiny silver, and I just like the black Colt pins better.
Most importantly however, is the ease of tapping taper pins in and out, without having to use bent pins and red loc-tite.
You can get a taper pin reamer from Brownells and run it through yours for true taper pins. What I would do is put one straight pin in and then ream the other hole. Then install the taper pin and ream the other one.
Cool, thanks for the info gotm4.
Does this mean that the Colt 6920’s/etc using taper pins, have a TRUE tapered hole?
I will check the size of the taper pin reamer from Brownells, but I’m assuming you know for a fact, that it’s the proper size for these taper pins?
I’ve actually got a Brownells Military/LEO Armorers Catalog, so hopefully it’s in there. I have found many tools that are actually NOT in the Armorers catalog though.
We’ll see. Thanks so much for the info gotm4. I had not thought about “taper pin reamers”!
My understanding- If taper pins are used to affix the FSB to the barrel and for some reason force is exerted on the pin head, they will become loose and drift out.
If straight pins are used, even with partial removal they will still retain the FSB with the same amount of force.
It seems to me that straight pins would actually work better. Is there a flaw in my reasoning?
I don’t know. I can say that I’ve worked on several hundred ARs and have never had a taper or straight pin walk…Maybe one can, I’ve just never seen it.
Guys,
I received my 2/0 taper pin reamer last week, and just today, I have started reaming out the STRAIGHT holes in my FSB/BBL, with the taper pin reamer (thanks gotm4).
Anyhow, I just wanted to ask if anyone can tell me how far I should take the reaming? I mean, when I take the new taper pin, and put it down into the newly reamed hole, HOW FAR should the taper pin seat down into the hole loosely, before I slam it in with a hammer?
I’ve just about got the holes reamed out to the point that the new taper pins seat down into the holes about HALFWAY (or half the length of the pins themselves)
SO, I’m just trying to decide HOW FAR I should ream the holes, or HOW FAR should the pins seat down in the holes LOOSELY, before I quit reaming?
Do any of you armorers who constantly remove taper pins, know off the top of your head, how far a taper pin should fit down into the hole before hammering into place?
I have a good idea, but I want to be absolutely sure, before proceeding.
Thanks again gotm4 for the taper pin reamer suggestion, and also thanks to comp1911 for the correct “2/0” size. (Brownells was out of stock the other day, so I had to order a 2/0 from MSC, and knowing the proper size really helped!).
I keep testing the taper pin for depth, knocking it in with a brass hammer, if it won’t go all the way through ream some more. I keep reaming until the taper pin sticks out the other side of the FSB about 1/16" or so after knocking it in with a brass hammer. I like to get them so that both sides sticking out of the FSB are just about even. Just go slow taking your time. You’ll usually need to ream much further than it appears you need. Then once done you can reuse your old taper pins. Whenever possible I like to use brand new Colt taper pins.