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View Full Version : How to remove BCM front sight base gas block from complete upper?


zoglog
09-03-2010, 8:54 PM
Hey guys,

I just got my BCM upper and a front flip sight gas block and trying to change it out. However I can't seem to tap out the pins. It looks like they're riveted from the left and the right side! anyone had any luck?

Josh3239
09-03-2010, 9:12 PM
They are tapered so make sure you knock them out from the correct side. Just use a punch and a hammer and hit it hard. They'll come out. If you don't care about the pins or the FSB you can carefully drill them out.

zoglog
09-03-2010, 9:28 PM
Hmm I hit it pretty hard, maybe not hard enough.

Also is it necessary to have this thing to avoid damaging other parts?

http://www.brownells.com/.aspx/sid=44769/pid=20727/sku/AR_15_Front_Sight_Bench_Block?utm_medium=shoppinge ngine&utm_source=googlebase&mc_id=10000&gdftrk=gdfV21820_a_7c187_a_7c745_a_7c080000252_d_0 80000252_d_116

I'm so sick of the proprietary tools required for simple AR changes =/

these are the punches I got now

http://www.bravocompanyusa.com/AR15-Punch-Set-p/tool%20ar15%20punch%20set.htm

Been knocking at the pins from the left side w/ a mallet but nothing happening. I swear it looks like these pins are riveted on both ends...

IsaacGlass
09-03-2010, 9:38 PM
Hmm I hit it pretty hard, maybe not hard enough.

Also is it necessary to have this thing to avoid damaging other parts?

http://www.brownells.com/.aspx/sid=44769/pid=20727/sku/AR_15_Front_Sight_Bench_Block?utm_medium=shoppinge ngine&utm_source=googlebase&mc_id=10000&gdftrk=gdfV21820_a_7c187_a_7c745_a_7c080000252_d_0 80000252_d_116

I'm so sick of the proprietary tools required for simple AR changes =/

Yes, it will make it easier but you can do without as long as you have a flat stable surface and some 2x4 wood blocks. Perhaps, you are hitting on the wrong side?

zoglog
09-03-2010, 9:47 PM
I doubt it, I'm hitting from left to right like all the guides say.

Is it necessary to remove the gas tube or anything else before I start trying to remove the pins?

fusionstar
09-03-2010, 9:56 PM
Man up.. Hit the small side of the pin.

All I can tell you.

IsaacGlass
09-04-2010, 12:32 AM
I doubt it, I'm hitting from left to right like all the guides say.

Is it necessary to remove the gas tube or anything else before I start trying to remove the pins?

I usually punch out the gas tube pin first

zoglog
09-04-2010, 1:31 AM
Well I managed to get the gas tube pin out easily...

The other 2... I spent like 30 minutes hammering away.... damn thing won't budge........... Driving me freaking nuts! Does anyone know of a store near West LA that can remove this for me. I've just bout given up.

stevie
09-04-2010, 6:24 AM
AR-10.com

http://www.ar15.com/forums/topic.html?b=2&f=138&t=181708

If you are around Torrance, I have the brownells FSB block

CHS
09-04-2010, 7:08 AM
BCM's are damn near impossible to punch out.

I've done a few gas block swaps on BCM's and they always end up with yelling and screaming involved.

You need to get a large punch and a LARGE hammer and hit those pins as hard and as fast as you can to knock them free.

Use the Brownells FSB block.

It's also funny that you call these "simple AR changes". Swapping a gas block is not a simple change and that's why it requires special tools.

stevie
09-04-2010, 7:33 AM
Thinking of using a shop press to start the pins. Kinda like removing the BBL pin on a AK.

zoglog
09-04-2010, 8:39 AM
AR-10.com

http://www.ar15.com/forums/topic.html?b=2&f=138&t=181708

If you are around Torrance, I have the brownells FSB block

Yeah BCM sent me that link this morning O.o Weird thing is I searched google all night for BCM specifically since I felt something was up and didn't find anything.
Guess it wasn't just me. I was pounding on that sucker for awhile and nothing was happening. I kind of wished I had asked them if they would remove it while shipping.

It's also funny that you call these "simple AR changes". Swapping a gas block is not a simple change and that's why it requires special tools.

I mean physically speaking it seems like a simple enough change though. It's 3 pins, you punch em out. Slide the gas block on, slide a new one on. slap the gas pin back in and screw the clamps on. It would actually not be so bad if these tapered pins weren't such a $@^^^!#^. I think I nearly killed my chinchilla hammering that thing last night.

The DRis
09-04-2010, 10:25 AM
You don't want them to simply hammer out. Or they might come out while shooting. It's good they are tight.

You need to make sure you do it right from the beginning. Right punch, or nail set works better, and a big hammer. Hit it hard and fast. If you don't and just keeping hitting it but not moving it, you'll balloon the small side and make the job even harder.

dchang0
09-04-2010, 11:20 AM
Another option is to simply cut the FSB off with a Dremel, which is what I had to do when my pins wouldn't budge. Obviously, if you want to reuse the FSB, this isn't for you.

If you do go this route, cut slowly and carefully. If you do it right, you can actually cut the FSB without even scratching the parkerized finish under the FSB (if BCM's are parkerized under there).

Josh3239
09-04-2010, 3:41 PM
I think Randall at AR15barrels.com is in West LA and can do it for a cheap price. Also called Chris at Addax, he is in SFV and he'll do it.

themethod
09-04-2010, 4:14 PM
I have done this before and it seems impossible to get those pins out until they start to go then it's easy. I used a fairly large nail punch with a bit of a cup to the tip to avoid mashing the pins. Make sure you put the barrel on a hard surface that doesn't absorb the impact of your hammer, I used an old sock on concrete and that worked, a wood 2x4 was too soft.

Good luck.

ETA. The nail punch, I bought from a local hardware store... I have a set of punches like the link you provided and they weren't up to this task.

Noah3683
09-04-2010, 4:24 PM
I used an air hammer with a nice pointed punch tip. came right out. just make sure you feather the trigger.

zoglog
09-04-2010, 4:56 PM
Thanks for the link guys (That WLA barrel guy could be useful if I need to swap to another stripped upper :D)

Stevie has graciously offered to help me tomorrow. Hopefully we'll be able to knock these pins out.

damon1272
09-04-2010, 6:13 PM
They should not be that hard to knock out. Use a larger flat tip punch on the small side of the pin with a 12 oz hammer and support the barrel. A block of wood works. You could try a little heat on the front site base and they would come out without hurting the finish.
As posted elsewhere http://www.ar15.com/forums/topic.html?b=2&f=138&t=181708

ktom300
09-04-2010, 8:12 PM
I had to grind the pins flat and partially grind the FSB as well. I was tossing it anyway as it had been cut down.
Even then I had to hit it pretty hard and several times.

littlerocket
09-05-2010, 1:57 AM
I got them out by using a big punch and hit them until the are flush with the FSB. Then use a punch about the same size as the pins and you should be able to get them out. When you knock them flush in the beginning, they will be loose enough to remove. I had a hard time and BCM recommended this way after I emailed them.

zoglog
09-05-2010, 9:49 AM
mission accomplished thanks to stevie and his 20 ton press. Got to meet a great stand up guy too. hoorah... now just to wait till my lower arrives

ar15barrels
09-05-2010, 10:03 AM
Well I managed to get the gas tube pin out easily...

The other 2... I spent like 30 minutes hammering away.... damn thing won't budge........... Driving me freaking nuts!
Does anyone know of a store near West LA that can remove this for me. I've just bout given up.

:gene:

ar15barrels
09-05-2010, 10:11 AM
BCM's are damn near impossible to punch out.

I don't hammer out nearly as many taper pins as I press out these days.
The key is getting your press fixture optimized.
I finally found the strongest setup that won't bend my press ram tips.

CHS
09-05-2010, 5:47 PM
I don't hammer out nearly as many taper pins as I press out these days.
The key is getting your press fixture optimized.
I finally found the strongest setup that won't bend my press ram tips.

One of the projects I never got off the ground at Riflegear was building a press fixture so that I could get pins out this way using an arbor press.

Like I said, never got off the ground :) But I would like to revisit it someday.

ar15barrels
09-05-2010, 5:50 PM
One of the projects I never got off the ground at Riflegear was building a press fixture so that I could get pins out this way using an arbor press.

Like I said, never got off the ground :) But I would like to revisit it someday.

I tried that.
Didn't work.
Probably because I didn't have a big enough arbor press or because it was not bolted to the floor.
I suppose with a 2 or 3 ton model that was bolted to a bench that was bolted to the floor, it would work.