hello folks! i have an older ar15, probably made in the early 70's, that i've thought about putting a shorter barrel on it and a colapsable butt stock. can i buy a short barrel and just screw it on the existing reciever using the original bolt carrier assembly or will it need to be headspaced? thanks for any info.
Do you already have all the tools to do a barrel swap?
You would need a vice, a receiver block, a barrel wrench/armorers wrench, punches, a torque wrench, and probably shorter handguards. Some handgaurds may require a special tool or two for installation if going with a free float set of hanguards.
It could almost be less expensive to buy a complete upper to just pop on to your lower.
Collapsible stock would require the appropriate buffer tube, buffer, recoil spring, end plate and castle nut.
As far as headspace goes, headspace is set when the barrel assembly is actually made. The barrel extension sets the headspace. Once headspace is set, the barrel extension index pin hole is drilled andthe index pin is installed, then the gas port is drilled. All ofthis has to be squared up so that the barrel will install right side up with the gas port upright as well, so the gas block will be lined up. The front sight base/gas block is installed andthe taper pin holes are bored into the base and the barrel at the same time, matching the FSB and barrel.
Now if headspace is off you are out of luck, because adjusting the barrel extension at all puts everything else out of alignment. Headspace is set to one dimension, and bolts are made to one dimension. There are no oversize or undersized bolts intentionally made to remedy a bad headspace.
So, the best you can do with a new barrel and bolt is verify headspace and hope that you have a badly made bolt if it is off. If the bolt is off it's trash, if the barrel is off it's trash, or at least very costly to salvage.
The military branches recommend that a bolt and barrel that are fired together stay together. A new bolt can be installed in an older barrel, but headspace must be verified.
I agree that simply getting another complete upper (around $350 or higher) would solve your problem and be LOTS simpler.
Even if you borrow the proper tools, you'll be trying to align that gasblock, get a working gas tube (some shorty's require a spiral), handguards that fit, ect.
Another vote for a newer upper receiver!
And then, if you should decide to sell later, you have an all original model with an extra upper.
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well, i guess my big idea of unscrewing one and screwing another on isn't easy. i was trying to come up with a simple, light, easy carry dog gun. thanks guys!
It's easy. But you need the right tools and all of the parts to do the conversion. The combination of the cost of the tools and parts makes it less worth while if only doing one upper. But there are lots of good manufacturers that make complete uppers. Then it is as simple as pushing out two pins and putting the upper on and pushing the pins back in.
It is one of teh nice things about the modular design of the AR. Special Forces had Special Purpose Receivers made to allow for more versatility of their light and short carbines. By pushing out the pins and popping on a new upper they had a 18" match barreled upper with a scope to use as a short range light sniping platform. If they were going close quarters they could replace the 11.5" barreled upper back on and viola they had a Mk18 carbine again.
My personal coyote rig has evolved from having a A1 length fixed stock and A2 upper to a 16" barreled flat top upper with a freefloat tube, and intermediate power scope, and a colapsible stock. It's great for walking to a place to set up and call in yotes, then move to another call location. I have another upper that has a 20" stainless match barrel and floated quad railed handguard and a 6-18 scope that I can put on it for a good prarie rat shooter, when I'm back out west, and likely to be more stationary.
But the Vltor stock gives a nice cheekweld for scope use, and the 2 stage match trigger in the lower is consistant from set-up to set-up.
thanks for the info. when i say "dog" gun i mean coyotes. they are a real nusiance in my area. one of the fears i had about new uppers is ending up with more in the gun then what its worth. its an old colt that hasn't been shot in years. thought about buying another gun but the black guns really make good sense as far as all weather varminters. i had noticed some flat top uppers in the $600+ range, not sure what a collapsable butt stock costs. i do have a barrel wrench and understand the taper pins, sights and gas tubes. i didn't know that a new barrel wouldn't readily index.
Oh it will readily index.
What I was trying to emphasize is that there is no real headspacing you can do. When you get a barrel it is either going to be right or it is going to be wrong, and afterthe fact there is nothing you can really do about it. Since manufactureres have to make them to the same dimensions this is usually no problem. All you need to do after assembling the upper and barrel is to VERIFY headspace. I've never found a new barrel and bolt that didn't headspace out of over 30 rifles I've helped assemble or assembled myself.
Some folks just think that normal wrenches and tools will work. And to an extent they can, but assembly is easier with the right tools.
You can pick up a M4 type collapsible buttstock assembly with the castle nut, and end plate along with a carbine buffer and spring for around $75 from J&T distributing.
You could just run the rifle stock if you prefered. Some folks like having the more stable stock, and having it always be the right length. Or run the rifle stock with the carbine upper for a while and save for a super duper collapsable stock.
My wife ran her carbine with an A1 stock for a while until we decided on a collpsable that she liked.
Oh, and I knew exactly what you meant by a "dog rifle". I built my coyote carbine with the idea of doing several coyote sets a day in mind.
My 'yote rig is on the far left. It needs a lighter handguard and maybe a lighter profile on the barrel as it gained some weight. But it is 'yote accurate to 250-300 yds with the right loads. Of course we try to call them in closer.
Might want to reconsider the collapsable butt... for a long time I wanted one for my AR build, but after trying a few I realized I didn't like them (except for the Magpul UBR @ $260!) and went with a 'shorty' A2. Just something to consider.
I would tend to agree with the others on a new upper. Believe me, your 'old' Colt is still worth it's weight in gold and I probably wouldn't screw with the upper... leave it be. In fact, if it's all original, you could probably sell it and make up a goodly amount to put towards a new upper (if that's what you wanted to do.)
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folks, it looks like a new upper is the direction i need to head in. SSGN_Doc the one you have on the right was the direction i thought about doing. thanks to everybody!