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  #1  
Old 10-26-2010, 09:42 PM
MrM MrM is offline
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Maybe I have my facts wrong, but from the little reading and looking I've done it seems that the uppers nowadays are of the milspec design, with the front pin hole of .25". Is this wrong?

The reason I'm asking is I have an old Colt SP1 lower, which has the larger .315" forward pin hole. Right now I'm using a funky eccentric screw holding the lower onto an ancient M16A1 upper. I'd like to find an upper I can use with a normal piece of hardware... as in, whatever the SP1 used originally.

I guess I should add that I'm not really looking for a vintage SP1 upper. I kinda like having a forward assist.
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  #2  
Old 10-26-2010, 11:44 PM
superdude superdude is offline
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i saw some recently at a manufacturers website whose name i can't remember. do a search and see what you can find. i don't recall, however, their configuration with or without forward assist.
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  #3  
Old 10-27-2010, 01:17 PM
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dsk dsk is offline
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Can't you special order one from Bushmaster, DPMS or a similar venndor?
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  #4  
Old 10-27-2010, 05:35 PM
MrM MrM is offline
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Quote:
Originally Posted by dsk View Post
Can't you special order one from Bushmaster, DPMS or a similar venndor?
That's an excellent question. I had not thought to ask them. Since they'd just need to make a bigger hole out of the smaller one, careful drilling/boring ought to be a simple job... or they could just start with an not-as-yet-drilled upper I guess. I might write to them and see what they'd charge.

What I'm most interested in is a true M16-A1 upper. The Bushmaster and DPMS versions are close, but they have the deflector bump. I guess that might be convenient in certain situations, but I don't care for it much. I shoot right handed and not worried about getting conked in the face by brass.

I have seen online vendors selling true A1 uppers (with the standard pin hole of course). I suppose I could find a smith that would modify it.

Not sure what I'll do yet, but thanks for the idea.

Last edited by MrM; 10-28-2010 at 09:36 AM.
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  #5  
Old 10-27-2010, 09:28 PM
Mike92GT Mike92GT is offline
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Daniel Defense makes a big hole flat-top upper:
http://www.danieldefense.com/?page=s...&product_id=19
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  #6  
Old 10-27-2010, 10:43 PM
M2HB M2HB is offline
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The hole is not only larger, but it is also offset.
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  #7  
Old 10-27-2010, 11:38 PM
Tonimus Tonimus is offline
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Don't know what you were looking at a M16A1 upper, but J&G had them at the gun show I just went to on sale for $500 for an upper kit with a new barrel in the white.
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  #8  
Old 10-28-2010, 09:40 AM
MrM MrM is offline
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Thanks. I noticed that the screw holding mine together has and eccentricity to it, so yep there's an offset of some kind. Makes it tricky to reassemble the rifle and get things aligned correctly. I'd assume that this is taken into account with the Daniel upper Mike referenced. If I decide on a flat top some day I'll probably look into that one.
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  #9  
Old 10-28-2010, 10:30 AM
GFW GFW is offline
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Big hole Upper

I have a Colt M16A1 big hole upper. Pm me.
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  #10  
Old 10-28-2010, 01:46 PM
Bitter Bastard Bitter Bastard is offline
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Not what you asked, but you can buy a new stripped lower with a standard (small) front hole for around $100, less if you look around.

To save money you can transfer all your existing lower parts to the new lower. I'd recommend spending the extra $50-60 and buying an LPK and then just moving your stock and buffer assembly to the new lower.

And then later on, buy a new stock and buffer assembly and have two complete lowers. And then make sure you have an upper to go on each one.

Seriously, though, why spend money on something oddball like an large pivot pin upper receiver?

Last edited by Bitter Bastard; 10-28-2010 at 01:48 PM.
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  #11  
Old 10-28-2010, 04:13 PM
herd48 herd48 is offline
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Quote:
Originally Posted by Bitter Bastard View Post
Not what you asked, but you can buy a new stripped lower with a standard (small) front hole for around $100, less if you look around.

To save money you can transfer all your existing lower parts to the new lower. I'd recommend spending the extra $50-60 and buying an LPK and then just moving your stock and buffer assembly to the new lower.

And then later on, buy a new stock and buffer assembly and have two complete lowers. And then make sure you have an upper to go on each one.

Seriously, though, why spend money on something oddball like an large pivot pin upper receiver?
I would tend to agree.
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  #12  
Old 10-28-2010, 04:40 PM
MrM MrM is offline
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Not a bad thought, just getting a more compatible lower at some point. Kind of puts me over-budget for this tentative project though, which started with my just looking at replacement barrels. And I am not sure what the legal hurtles would be for buying a lower here in CA, since it's a "gun", right? I might have to buy one of those stupid "need a tool to drop the mag" type receivers.

Truth is, I'm not really interested in acquiring another rifle. I'm just trying to make my one and only AR work a little better.
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  #13  
Old 10-29-2010, 01:50 PM
Bitter Bastard Bitter Bastard is offline
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Rebarrelling an AR upper is pretty trivial and now you're back down to just the cost of a new barrel. I didn't notice you were in CA.

Good luck!
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  #14  
Old 10-29-2010, 04:21 PM
jwc41 jwc41 is offline
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There was an outfit years ago (name forgotten) that made a conversion pin that enabled mounting a mil-spec upper to an SP1 lower. I didn't see them on the market much after mil-spec lowers started coming on the market, so that knowledge may not be of much help to you.
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  #15  
Old 10-30-2010, 08:41 AM
MrM MrM is offline
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Quote:
Originally Posted by Bitter Bastard View Post
Rebarrelling an AR upper is pretty trivial and now you're back down to just the cost of a new barrel. I didn't notice you were in CA.

Good luck!
I've been looking into that as well. It's kind of how this idea started. I haven't found exactly what I'm looking for yet---for the money I feel I should spend---but at least the choices are generally more abundant than this receiver thing. What I want is 16" mid-length barrel, gov profile under guard, and chrome lined. Cheapest/nearest I've found for a bolt-on solution is Del-Con's lightweight mid-length, but it's not chromed. (I might start a thread asking whether chrome and chamber lining is really something to hold out for.)

Next up from that would be Bravo company's mid-length upper. It's a lot more money than just a barrel, but the barrel itself it exactly what I want and I'd get another receiver out of the deal. And a flat top at that.

Bravo does sell just the barrels, but that's it: just their stripped barrels. No FSB attached. It puzzles me that they don't go just one step further. I'm not really set up for installing a blank FSB. Daniel and Sabre also make what I want but they cost almost as much as the Bravo upper I'm considering.

What I've thought about doing is buy the Bravo middy upper, pull the barrel off the receiver and put it on my A1 receiver, and use the new flat top to build another, longer barreled upper. It's what's called project creep.

Quote:
Originally Posted by jwc41 View Post
There was an outfit years ago (name forgotten) that made a conversion pin that enabled mounting a mil-spec upper to an SP1 lower. I didn't see them on the market much after mil-spec lowers started coming on the market, so that knowledge may not be of much help to you.
Yep. That's actually what's been holding my SP-1 lower to my M16A1 upper for thirty years. I was hoping for a less bastardly solution, but I made have to live with using the bolt.

They are still available. For instance, Bravo Company sells one made by DPMS for $3.
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  #16  
Old 10-30-2010, 12:29 PM
Mike92GT Mike92GT is offline
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You could go with a Rock River barrel. It will be a bit cheaper than the others, and still chrome-lined. Plus it won't have M4 feedramps, so it will match up better with your existing upper. Link, second one down on the page:
http://www.pkfirearms.com/Rock_River_Arms_Barrels/64/c
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  #17  
Old 10-31-2010, 08:57 PM
MrM MrM is offline
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Quote:
Originally Posted by Mike92GT View Post
You could go with a Rock River barrel. It will be a bit cheaper than the others, and still chrome-lined. Plus it won't have M4 feedramps, so it will match up better with your existing upper. Link, second one down on the page:
http://www.pkfirearms.com/Rock_River_Arms_Barrels/64/c
Mike, where did you see that it doesn't have the A4 ramps? I can't find it mentioned either on PK's site or on RRA's site.

I actually sent an email into RRA with this question, so if you can't get back to me in a couple of days, I might have the info from them.
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  #18  
Old 11-01-2010, 12:32 PM
Mike92GT Mike92GT is offline
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Not sure if you heard back from RRA, but to my knowledge none of their barrels are available with extended feedramps.

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Originally Posted by MrM View Post
Mike, where did you see that it doesn't have the A4 ramps? I can't find it mentioned either on PK's site or on RRA's site.

I actually sent an email into RRA with this question, so if you can't get back to me in a couple of days, I might have the info from them.
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  #19  
Old 11-01-2010, 04:12 PM
herd48 herd48 is offline
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M4 ramps are cut into the "barrel extension". They are not really "extended". And they have nothing to do with the barrel. If you buy a barrel......you will have to buy a barrel extension to go with it. Unless you can use the one that's on your present upper. Brownells and other places have a selection of barrel extensions. You should be able to find one without the M4 cuts.
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  #20  
Old 11-01-2010, 06:43 PM
Mike92GT Mike92GT is offline
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Actually this isn't quite correct. Pretty much any barrel you buy will have the barrel extension already on it. They are pressed on, and they are generally not something you remove or replace. It's considered part of the barrel. They why some barrels are advertised as having extended feedramps, and some aren't. Here is an example:http://www.bravocompanyusa.com/BCM-1...d-16%20std.htm The barrel in the link is "stripped", yet it still has the barrel extension on it. Note the description towards the bottom, " M4 Feed Ramp Barrel Extension "


Quote:
Originally Posted by herd48 View Post
M4 ramps are cut into the "barrel extension". They are not really "extended". And they have nothing to do with the barrel. If you buy a barrel......you will have to buy a barrel extension to go with it. Unless you can use the one that's on your present upper. Brownells and other places have a selection of barrel extensions. You should be able to find one without the M4 cuts.
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  #21  
Old 11-01-2010, 07:43 PM
herd48 herd48 is offline
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Quote:
Originally Posted by Mike92GT View Post
Actually this isn't quite correct. Pretty much any barrel you buy will have the barrel extension already on it. They are pressed on, and they are generally not something you remove or replace. It's considered part of the barrel. They why some barrels are advertised as having extended feedramps, and some aren't. Here is an example:http://www.bravocompanyusa.com/BCM-1...d-16%20std.htm The barrel in the link is "stripped", yet it still has the barrel extension on it. Note the description towards the bottom, " M4 Feed Ramp Barrel Extension "
Because the M4 ramps are cut into the barrel extension and the receiver(slightly), it makes sense that barrel and extension come together IF M4 ramps are desired. If not desired as in the OP's case. A barrel can be purchased by itself, and he could possibly use the extension already in the current receiver. His receiver has not been cut. "Pressed in" is a little misleading. Yes in most cases of a new build, it requires some slight tapping to seat barrel. But "pressing" the parts together is not a necessity. Just easier for factories. Barrel extension should be pre drilled and an indexing pin is required. But again, in OP's case where M4 ramps are not desired, I think it can be done without much trouble. There are a variety of replacement barrels sold without barrel extensions. I'm sure a call to the manufacturer of choice could result in the set up he desires. BTW- Del-Ton and CMMG are two places I would call that could probably provide a barrel, extension, and "F"marked FSB of your choice. Without M4 ramps. Already assembled. I would try them.
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Last edited by herd48; 11-01-2010 at 08:05 PM.
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  #22  
Old 11-01-2010, 08:14 PM
MrM MrM is offline
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I don't know if it settles any controversies, but I heard back from RRA about my question. As Mike already pointed out, they said, "We don't do no skeenking M4 receivers", or something to that effect.

And I also heard back from Del-Ton about their feed ramps, etc. Their rep said I could put one of their M4-ramped barrels in my A1 receiver and shoot it all day long. Again, what Mike indicated earlier. Basically, she described the scenarios shown in that feed ramp compatibility diagram linked above---where the worst would to try using a rifle-ramped extension in an M4 receiver; it would be jam-city.

They seem like good companies and I wish I could buy both their products. I'll probably get the RRA since it's chromed and "made for" my receiver.... even though it's almost $100 more.

EDIT:
forgot to mention that the Del-Ton rep said they could give me any ramp I wanted... so long as I ask.

EDIT AGAIN: Never mind my earlier question about F FSBs. I just looked it up. They're a little taller so as to be used with FT receivers. It's not something I'd want with this barrel.

Regards,

MrM, OP

Last edited by MrM; 11-01-2010 at 08:54 PM.
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  #23  
Old 11-01-2010, 09:08 PM
Mike92GT Mike92GT is offline
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Glad RRA confirmed that for you, I was 99.9% sure they didn't use M4 feedramps in any of their guns. None of my 3 had them. The F-marked front sight base is slightly taller than a regular sight base. They are preferred for use with a flat-top upper. I think either style front sight would work fine for you. I don't think RRA uses F-marked front sights either. I did misspeak on the barrel extension, they are threaded on (tight) and not pressed on. However it is still not a part that is normally changed out. The gas port is drilled and the taper pin holes are drilled after the extension is installed. If you replace it, chances are the barrel will never be timed right again. Generally if you buy a barrel without a barrel extension, it's just a barrel blank.
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  #24  
Old 11-01-2010, 09:17 PM
MrM MrM is offline
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Thanks. Typically, with the extension installed at the factory (or by a vendor?) can I expect the barrel to headspace correctly once the barrel it torqued into the receiver?
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  #25  
Old 11-01-2010, 09:24 PM
Mike92GT Mike92GT is offline
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It doesn't hurt to have the headspace checked, but it should be fine. I've built about 20 uppers and never had an issue. Generally the only times headspace will be off is if your bolt and / or extension is very worn, or the parts weren't made to spec to begin with.

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Thanks. Typically, with the extension installed at the factory (or by a vendor?) can I expect the barrel to headspace correctly once the barrel it torqued into the receiver?
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