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Any "large hole" AR uppers being made today?

17K views 27 replies 11 participants last post by  MrM 
#1 ·
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.
 
#3 ·
Can't you special order one from Bushmaster, DPMS or a similar venndor?
 
#4 · (Edited)
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.
 
#26 ·
Just to follow up, I think I'm going to get one of these. Thanks for the heads-up Mike. They're not the cheapest of uppers available, but since it's one of the only options open I can't really complain. And I'm sure the quality must be as good as it gets.

I still want to find a large-hole A1 upper, with no ramps ("rifle" type?), and preferably w/o the bump.
 
#8 ·
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.
 
#10 · (Edited)
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.:rock:

Seriously, though, why spend money on something oddball like an large pivot pin upper receiver?
 
#12 ·
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.
 
#15 ·
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. ;)

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.
 
#14 ·
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.
 
#17 ·
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.
 
#19 ·
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.
 
#20 ·
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-16-Mid-Length-Barrel-Stripped-p/bcm-brl-s-mid-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 "
 
#21 · (Edited)
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.
 
#22 · (Edited)
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
 
#23 ·
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.
 
#28 ·
Thanks zdragon. I've got one of those now on my existing setup. I'm trying to get away from the two-headed-offset-screw design. I'd like a receiver (two receivers actually) that doesn't require my fiddling with multiple screwdrivers when field stripping.

Badass looking rifle BTW.
 
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