AR Sponsor
Posted: 4/27/2013 7:05:54 PM EDT
|
I'm not an expert, but I've done a few of these now. Hopefully this info helps someone.
0) Remove the gas tube by punching/pressing out the roll pin, pulling the gas tube back a couple inches then pulling the gas tube forward to around either side of the FSB. I suppose you can do any of the following work with the gas tube still in place, but it's much more convenient to just remove it first. 1) Use calipers to measure the diameter of the pins on both sides of the FSB. If one side of the pin has a smaller diamter than the other, you've got taper pins. To remove, hiit the pin from the side with the smaller diameter. If they are the same width on both ends, you've got straight pins. 2) Before doing any punching, make sure the FSB is secure with no movement. The FSB bench blocks work fine for most pins, but if you've got a real stubborn set of pins, you may need to hold the barrel near the FSB with barrel blocks and a sturdy vise. If you are planning to cut the FSB to lo pro, you can clamp the bayo lug with the vise, it has worked for me before. If you do this, remove the rear pin first. 3) Use a big punch with a larger diameter than your pins to break the seal that the pins may have. Slow and heavy hits with the hammer are better than lots of light hits. I just keep hitting the pins until they are flush with the FSB. Then switch to the 1/8" punch, which should easily drive the pins the rest of the way. If you plan to reuse the pins, make sure you match each pin to the original hole. 4) If you've got really stubborn pins, you can put the whole assembly (barrel or upper) into the freezer for 20 mins. Then secure the assembly as in step 2. Take a propane torch and heat the FSB but try not to heat the pins. The pins will stay cool (and slightly shrunk), while the FSB gets hot and the taper pin holes expand. The temperature difference is key here, a couple hundred degrees can make a big difference. 5) If the FSB is very tight to the barrel journal even after the pins are removed, you can repeat step 4. Same principle applies. Then smack the FSB with a rubber mallet. Reassembly tip: if you had to do step 5, you can get the FSB back on fairly easily by placing barrel in freezer for 20 min and FSB in oven at 300-400 degrees F for 20 min. Do not put any aluminum parts in the oven though. |
|
Almost all taper pins are installed right-to-left, but there are some that are backward, so it is good to check. And some builders use dowel (cylindrical) pins instead of taper pins, also important to know in advance.
Bravo Company has very well written instructions for doing this in their Industry Forum. They are specific to BCM only in that they install their FSBs to MIL-SPEC standards. Using a helper and a FSB bench block are highly recommended. On the other hand, those 10,000+ videos on line may or may not give decent instructions, safe procedures, or even workable steps. All it takes is a video camera and a computer to put a video online... |
|
Quoted:
Thank goodness this was posted as I would never have figured it out by the ~10,000 videos of it being done on YouTube...... This info will probably be moved to the "build it yourself forum" but I have seen a lot of youtube hack jobs do a lot of things incorrectly and post it online. Really no reason to be a dick especially with a screen name of Spoon fed GD is the other way 
|
|
Way I see it, every bit of info helps. If none of the info is new, at least I can reiterate that the freeze/heat method works. So well in fact, that I would use it for any FSB I disassemble in the future.
Quoted:
Thank goodness this was posted as I would never have figured it out by the ~10,000 videos of it being done on YouTube...... |
AR Sponsor