M16A1 Thumper- Disassembly of upper tutorial on pg 2

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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M16A1 Thumper- Disassembly of upper tutorial on pg 2

Postby 3rdgeargrndrr » Tue Sep 04, 2012 9:22 pm

I have been mulling over converting the 450b 20” upper to a retro inspired m16a1. I don’t want to go too custom and want to use as many off the shelf parts as available to minimize costs (i.e. no custom machining or one off parts). I would prefer to use actual surplus A1 parts as well.

So, I have some questions on how to achieve this. Can I use a generic A1 style stripped upper (or the actual one) and transfer all my existing 450b upper parts over to it? I have seen the picatinny rail detachable handles however they don’t look truly “A1” to me. I will go this route only if absolutely necessary.

Also a request, Can a 20” barrel owner measure the outer diameter of the barrel just beyond their faux front gas block so I can figure out if a Front sight block is available in that diameter? Yes, I plan on using triangle handguards. I understand that I might need to grind down the functional gas block to get it to fit. Thanks to all in advance on helping me build this.

Edit came together slowly; but rifle is finally done.

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For instructions on disassembly of upper, see first post pg 2
Last edited by 3rdgeargrndrr on Mon Nov 12, 2012 9:55 pm, edited 9 times in total.
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Re: M16A1 Thumper inspiration

Postby commander faschisto » Tue Sep 04, 2012 9:35 pm

Yo...welcome to our electronic campfire/asylum...glad to see another 450b addict! :)

The gurus will be along shortly to fill you in on the particulars of your proposed project...barrel diameter from the faux gas block is .750"
You'll have to do a leetle opening up of half of the ejection port, too, forward of the dust cover detent (recently described on the forum here).
I'm certainly not the expert on this, so wait for further guidance. Sounds like a fun project! Good luck... :P
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Re: M16A1 Thumper inspiration

Postby 3rdgeargrndrr » Wed Sep 05, 2012 8:32 am

Thanks for the info commander. (knock on wood) might be easier than i expected. I did read the posts on enlarging the ejection port so I can almost assume a standard upper should work fine. And thanks for the dimater measurement. I found a sight block at cmmg that should work perfectly.

*edit I just realized all if the information thus far have been in the forum. sorry for my laziness
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Re: M16A1 Thumper inspiration

Postby helidude350 » Wed Sep 05, 2012 8:44 am

:shock:
Now I want one too!!!!! :mrgreen:
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Re: M16A1 Thumper inspiration

Postby 3rdgeargrndrr » Sun Sep 16, 2012 1:47 pm

Ok, niggling question I thought of AFTER I purchased all of the retro parts- headspace gauges.

Does anybody know where to pick up go/no go gauges? do you pickup some win 284 and cut them to 1.70?

Bubba method (tape the end) with new brass?
:|
I'm stuck at this one.
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Re: M16A1 Thumper inspiration

Postby wildcatter » Sun Sep 16, 2012 1:51 pm

3rdgeargrndrr wrote:Ok, niggling question I thought of AFTER I purchased all of the retro parts- headspace gauges.

Does anybody know where to pick up go/no go gauges? do you pickup some win 284 and cut them to 1.70?

Bubba method (tape the end) with new brass?
:|
I'm stuck at this one.


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Re: M16A1 Thumper inspiration

Postby Texas Sheepdawg » Sun Sep 16, 2012 4:49 pm

Also a request, Can a 20” barrel owner measure the outer diameter of the barrel just beyond their faux front gas block so I can figure out if a Front sight block is available in that diameter? Yes, I plan on using triangle handguards. I understand that I might need to grind down the functional gas block to get it to fit. Thanks to all in advance on helping me build this.

It's gonna be .750 or there abouts.
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Re: M16A1 Thumper inspiration

Postby 3rdgeargrndrr » Sun Sep 16, 2012 7:22 pm

thanks to all for answers. This week I will be taking the dremel to the pristine "slick side" upper to open up the ejection port and picking up the stag arms lower. I've never ground down on aluminum before. I hope to keep my patience :lol:

I will using the leftover parts to build a 22LR upper for the wife and kids, when I'm done, :D

FYI:
TX Sheepdawg; Your YouTube videos helped me decide to return to and purchase this rifle platform and caliber. The video of you mushrooming the FMJ Magtech 230g was worth MORE than advertising for this rifle. I wont get rid of my 30-06 tack driver any time soon though.
Last edited by 3rdgeargrndrr on Thu Sep 20, 2012 8:00 pm, edited 1 time in total.
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Re: M16A1 Thumper inspiration

Postby Texas Sheepdawg » Sun Sep 16, 2012 7:46 pm

I've got more videos to make. I just need time and help setting up the gear. With these new cameras, the videos should have a better quality. I will still be using the Nikon camera for standard def stuff, but these Go Pros have already produced some very good quality HD work during my dove hunt. Unfortunately, the doves didn't cooperate like I wanted them to, so the video was more of a hunting video than a killing video.
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Re: M16A1 Thumper inspiration

Postby Hoot » Mon Sep 17, 2012 4:15 am

3rdgeargrndrr wrote:thanks to all for answers. This week I will be taking the dremel to the pristine "slick side" upper to open up the ejection port and picking up the stag arms lower. I've never ground down on aluminum before. I hope to keep my patience :lol:


While the strength of the slickside over a conventional receiver is a definite advantage, I myself would be lost without my forward assist. Since the charging handle floats, I'd imagine the worst feeling would be squeezing the trigger on a trophy animal and realizing the bolt was not in full battery. The time, loss of sight window and noise of recharging anther round would be agonizing. My 6.5 Grendel backup upper is a lo-pro and I worry about just that scenario. The good news is the Grendel is for long shots and at least the motion and noise is of less concern.

Just my $.02 worth...

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