Author Topic: Checking Lower Receiver Pin Location  (Read 15902 times)

Offline ferretface

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Checking Lower Receiver Pin Location
« on: November 25, 2007, 10:40:03 AM »
Checking Lower Receiver Pin Location

If you read my thread on the Les Baer AR-15 unmachined lower receiver  >:( , you'll know why this is important. 

I started by taking a new 80% lower and trial fitting it with a Colt M16 upper receiver that I'll be mating this lower to. It's a nice tight fit.



Next I apply some bluedye to the front pin hole, since this is the most visible indicator of whether the machining operations are within spec or not. (Actually, I couldn't find my bluedye, so I used a Magic Marker).  ::)



I put my upper on the outside of the lower, flat against the lower side, and scribed a circle inside the front takedown pin hole.



Here's the scribed circle.



Next I set up the lower in one of Justin's jigs according to his instructions.



And I scribed a second circle through the jig hole. If the pin hole is located correctly, the two circles should be concentric or even concurrent.



Here's the lower, with the two circles scribed. They seem to be concurrent, so I'm happy that this lower has the top deck height correctly milled, and the front takedown pin hole correctly located.



Here's the front pin hole after drilling. Pretty close to being perfectly centered.  ;)



Finally, here's the lower with the 5 major holes drilled, and pinned in place with the upper. Nice and tight, no rattle or movement. Ready for the buffer tube hole to be bored and tapped.



Offline jwh02017

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Re: Checking Lower Receiver Pin Location
« Reply #1 on: November 26, 2007, 09:27:28 AM »
VERY NICE!!!  I've never seen anybody use the upper/lower mate method like you did.  I love looking at how others complete their projects.  Just goes to show there is more than one way to skin a cat... haha.

Justin

Offline john q publik

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Re: Checking Lower Receiver Pin Location
« Reply #2 on: December 09, 2007, 06:59:23 AM »
That's along the lines of how I set up mine.  Since I know Kevin's lowers are in spec on the top and back, I lined it up in the jig, and pinned an upper to the outside of the jig.  This way, I could use a straightedge across the back of the upper to see where it would line up with the lower, and adjust the fore/aft position of the lower in the jig accordingly for a nice tight fit.  Worked pretty well, as I kinda have to close the upper down on the lower in one swift movement, sort of like closing a shotgun, if you so it slowly, it doesn't like to close fully.  Nice job.

Offline ferretface

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Re: Checking Lower Receiver Pin Location
« Reply #3 on: December 14, 2008, 12:07:59 PM »
There's been talk here about the AR15Plus/Vida Rica 80% lowers being out of spec... 

I just received an 80% Vida Rica lower on 13 Dec '08; it has the FCG cavity and rear takedown lug area *partially* milled out, and the buffer tower drilled to 1" but of course not threaded...

I decided to check the Vida Rica lower to see how it stacked up in Justin's jig...

As you can see from my notes in red, the top plane was cut a little bit too high...the magazine release should be centered on its boss...and my scribed circle (and the center dot from a 1/4" drill bit) are just a bit too high also...



This is not a big concern...everything else is OK...and I've seen aftermarket lowers farther off than this...I'm just anal about stuff like this...   :-*

Here's a shot of the Vida Rica compared with one of Kevin's old style lowers, already finished...I don't know how well it shows up on your monitor, but the sides of the Vida Rica FCG area are ~.125"; much too wide...and the rear takedown lug cavity is ~.470", not quite enough to get the .500" upper rear lug seated...but the front lug "ears" are cut to ~.500", and a Colt upper fits nicely in there...



The magwell is right on; all my mags drop right through...

...After removing all the "kerf" on the machined surfaces...that's the sharp excess left on the trailing edge of a milled surface...it's sharp as hell; it'll cut fingers and leave scratches on finished parts if not removed by tumbling or filing...

The lower is certainly usable and it's actually machined very nicely...it's slightly different from Kevin's forging blanks; from the look of the right side of the buffer tower, I think it's an Anchor-Harvey forging...

All in all, it's worth the $$$ if you'd rather have the bulk of the FCG cavity milled out and don't mind drilling & tapping the buffer hole yourself...but you'll still have to finish it up; filing the hammer & trigger won't be enough...   ;)

Offline goober

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Re: Checking Lower Receiver Pin Location
« Reply #4 on: December 14, 2008, 12:34:24 PM »
great report ferretface!  ;D
its been a while since i've handled a vida rica lower.... but my experience was similar to yours.
i have heard of problems with some though... perhaps some models are better than others, or they vary from lower to lower or batch to batch.
which one did you use?
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Offline ferretface

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Re: Checking Lower Receiver Pin Location
« Reply #5 on: December 14, 2008, 02:07:52 PM »
which one did you use?

...Um...This one...   ;D

AR15Plus.com

Also...I took a closer look at the "old style" lower that I last got from Kevin; it also appears to be an Anchor-Harvey...(in fact, they appear identical, although the forging logo is milled off the side of the grip tang)...and has the slightly off-center mag release boss...but after drilling in Justin's jig, the front takedown pin hole came out centered/right on...



I'm going to have to order another of Kevin's lowers and experiment further...   ;)

Offline goober

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Re: Checking Lower Receiver Pin Location
« Reply #6 on: December 14, 2008, 02:42:27 PM »
which one did you use?

...Um...This one...   ;D

[
yeah that's the flavor i have used w/ success as well.
i think maybe some folks had probs w/ the HPS, the one that has the front pivot pin drilled already... maybe.
experiment on! ;D
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Offline ferretface

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Re: Checking Lower Receiver Pin Location
« Reply #7 on: December 31, 2008, 09:39:31 AM »
I finished widening the Vida Rica FCG cavity to .690", and the rear takedown lug cavity to ~.050"...and while thinning the boss above the selector hole, I noticed that there was something different about the Vida Rica 80% lower...   :o

You can see it in this pic...



It's not necessarily a bad thing...Just something to be aware of...   :)

Offline FNFAL762

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Re: Checking Lower Receiver Pin Location
« Reply #8 on: March 18, 2009, 12:26:56 PM »
I used the Vida Rica lower for my first build and found the information you posted on checking the lower pin location very helpful. That made for a very nice tight fit. The only problem I found with the lower was the buffer tube hole was in line with the upper but when veiwed from the top while mounted in the press, the casting was off just a little making the buffer tube hole look off center. After the hole was cut and tapped it went together very well and has seen 500 rounds without any issues.

Offline Ryo

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Re: Checking Lower Receiver Pin Location
« Reply #9 on: March 29, 2009, 09:55:45 PM »
Great idea.  I'm new to this and all the info on making a perfect lower is very helpful!!

Offline Beau52501

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Re: Checking Lower Receiver Pin Location
« Reply #10 on: March 30, 2009, 06:19:20 PM »
I also did a Vida Rica lower andI also had to widen out the FCG well a bit to make everything work right.
Wasnet to much work but the one I did from Dlask was just plain perfect in comparison, although more pricey

Offline jdl6mm

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Re: Checking Lower Receiver Pin Location
« Reply #11 on: April 12, 2009, 11:18:26 PM »
Well, I'm new here but I have a couple of things to say. I just purchased three AR receivers from Vida Rica and they are just fine. If you look at the pic close enough from ferretface you can tell from the buffer tube threads, that the two receivers are being photographed at two completely different angles. The lower receiver is tilted down so the hole looks off center. Also, as far as the FCG well is concerned, it is only 0.470". In the info sent with the receivers Vida Rica clearly state that. They also explain that using either a milling machine or Dremel tool that 0.015" needs to be removed from each side in order for the well to be 0.500". Next, in one of the remarks someone asked another member what 80% receiver he ordered from Vida Rica and he didnt know. In fact his answer was "this one", with a pic of the receiver. Who doesnt know what receivers they ordered. The HPS, the JFM, the bronz one, the titanium one, which one man?

Offline ferretface

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Re: Checking Lower Receiver Pin Location
« Reply #12 on: April 13, 2009, 03:00:30 PM »
If you look at the pic close enough from ferretface you can tell from the buffer tube threads, that the two receivers are being photographed at two completely different angles.

Which pic??? Ferretface posted a couple pics...  ;)

Quote
The lower receiver is tilted down so the hole looks off center. Also, as far as the FCG well is concerned, it is only 0.470". In the info sent with the receivers Vida Rica clearly state that.

No, the rear takedown lug cavity is .470". The FCG cavity is .660" and should be ~.690".

Quote
Next, in one of the remarks someone asked another member what 80% receiver he ordered from Vida Rica and he didnt know. In fact his answer was "this one", with a pic of the receiver. Who doesnt know what receivers they ordered.

The link was to the order page, not to the pic itself. Ferretface ordered the lower with the features he wanted, which was the receiver he linked. As for not knowing which one...Ferretface didn't know there was more than one...  :D

Offline goober

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Re: Checking Lower Receiver Pin Location
« Reply #13 on: April 13, 2009, 03:36:02 PM »
Well, I'm new here but I have a couple of things to say. I just purchased three AR receivers from Vida Rica and they are just fine. If you look at the pic close enough from ferretface you can tell from the buffer tube threads, that the two receivers are being photographed at two completely different angles. The lower receiver is tilted down so the hole looks off center. Also, as far as the FCG well is concerned, it is only 0.470". In the info sent with the receivers Vida Rica clearly state that. They also explain that using either a milling machine or Dremel tool that 0.015" needs to be removed from each side in order for the well to be 0.500". Next, in one of the remarks someone asked another member what 80% receiver he ordered from Vida Rica and he didnt know. In fact his answer was "this one", with a pic of the receiver. Who doesnt know what receivers they ordered. The HPS, the JFM, the bronz one, the titanium one, which one man?
welcome to the forum jdl6mm  :D
sounds like you feel the AR15plus/Vida Rica lowers are getting a bad rap here, and unfairly so.
i don't think anyone said they were poor quality.
there is a known issue of some of them being out of spec as far as their top deck and rear surfaces go. this can result in improper alignment in the CNC jig and incorrect hole locations, if it is not addressed prior to jigging up the lower.
i don't think anyone was saying that the need to widen the FCG pocket was in any way hidden, or anything other than a known operation that needed to be done. no one was accusing the vendor of sloppy work or trying to pull a fast one.
in any event, IMO they are "just fine" as you mentioned, but are not my first choice in 80's due to the factors that have been mentioned. i have completed projects using these lowers myself, and still have at least one on hand that i will finish someday.
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Offline mariodave

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Re: Checking Lower Receiver Pin Location
« Reply #14 on: April 18, 2009, 06:52:55 AM »
I have bought two Vida Rica lowers.One was ok except the top surface was .006" low in relation to the pre drilled pivot pin.The rear surface of the buffer tower also stuck out of the jig .006"The pre drilled buffer hole was not quite centered in the casting.Also when the upper is installed the buffer is not centered to the upper.It is close enough that there is no binding when you pull back the charging handle.
    The other one I have is .006" too tall on the top surface and .006" too long on the buffer tower back plane.The hole in the buffer tower is offset .015" in the casting.I don't know if I should file off the top plane to be flush with the jig or not.I think this needs to be done though.With the pre drilled pivot pin you cant just line up the top and rear surfaces.It is a pain although the pre drilled trigger guard is nice.My question is ,is the buffer to be centered in the casting or centered with the mag well or with the rear lug or what.Looks like the mag well and FCG cavity and pin lugs are centered.
    The jfm states that the buffer is centered,the vida rica just states that it is 1".I would reccomend the jfm based on that but I have not tried to finish one.Could be problems with those too.I dont know how hard it is to drill the trigger guard holes.
  Any one had experience with the JFM lower or ideas about the problems with vida rica lowers?

Offline goober

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Re: Checking Lower Receiver Pin Location
« Reply #15 on: April 18, 2009, 09:27:32 AM »
I have bought two Vida Rica lowers.One was ok except the top surface was .006" low in relation to the pre drilled pivot pin.The rear surface of the buffer tower also stuck out of the jig .006"The pre drilled buffer hole was not quite centered in the casting.Also when the upper is installed the buffer is not centered to the upper.It is close enough that there is no binding when you pull back the charging handle.
    The other one I have is .006" too tall on the top surface and .006" too long on the buffer tower back plane.The hole in the buffer tower is offset .015" in the casting.I don't know if I should file off the top plane to be flush with the jig or not.I think this needs to be done though.With the pre drilled pivot pin you cant just line up the top and rear surfaces.It is a pain although the pre drilled trigger guard is nice.My question is ,is the buffer to be centered in the casting or centered with the mag well or with the rear lug or what.Looks like the mag well and FCG cavity and pin lugs are centered.
yes for this reason i prefer their other 80% lower, the JFM, w/o the pre-drilled pivot hole (when i must buy from VidaRica). they still need to be checked for top/rear surface in spec. but at least you are not stuck w/ the pivot hole placement.

Quote
    The jfm states that the buffer is centered,the vida rica just states that it is 1".I would reccomend the jfm based on that but I have not tried to finish one.Could be problems with those too.I dont know how hard it is to drill the trigger guard holes.
  Any one had experience with the JFM lower or ideas about the problems with vida rica lowers?
see above. trigger guard holes are easy to drill.
regarding buffer alignment, it's generally not a good assumption that the existing 1" buffer tower hole in unfinished forgings is correctly centered. some are, but many are not. you might take a look at this and this  8)
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Offline noobert

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Re: Checking Lower Receiver Pin Location
« Reply #16 on: April 18, 2009, 11:27:10 AM »
my JFM had the buffer hole drilled not in center

Offline Twistedsteel

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Re: Checking Lower Receiver Pin Location
« Reply #17 on: April 18, 2009, 08:12:08 PM »
Man you guys are really bummin me out. I bought the Vida Rica HPS with the jig and also the Baxter buffer jig. Well I guess this will be my learning lower. The buffer jig is pretty much a joke, doesn't line up at all. The main jig seems to be ok, it has angled recesses on it for the grip and the buffer retaining hole. So you just stick it in your vise and the angle is set,which is kinda cool. But I wish I would have found this site earlier, I've learned alot already. I will say that I don't know very much about machining and such but I'm pretty good with tools and love workin with metal, so it should come easy. I had a nice caliper that mysteriously disappeared so I'm gonna have to order another. Could you guys recommend any other tools that will make this easier. I've got the bits and taps, and I'm gonna order the reaming kit instead of using the drill bit.

                                                                      Thanks, Albie

Offline ferretface

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Re: Checking Lower Receiver Pin Location
« Reply #18 on: April 20, 2009, 02:29:13 PM »
Man you guys are really bummin me out. I bought the Vida Rica HPS with the jig and also the Baxter buffer jig.

This was not intended to be a Vida Rica bashing thread. I think the Vida Ricas are excellent. The points I tried to make are the differences between the current Vida Ricas and what we've been used to with Kevins older style lowers, and now his newer style. The 80% Vida Ricas aren't 100% finished in any of the machining operations. But the bulk of the work *is* done. 

I've never seen the Baxter receiver or buffer jig (just the pics). I have seen and used the Tannery Shop jig. I don't use any jig to do the buffer hole; I use the upper I'm going to mate it to as a jig. There's a couple good threads here on doing the threaded buffer hole and having it line up exactly with the upper bore.

Offline Twistedsteel

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Re: Checking Lower Receiver Pin Location
« Reply #19 on: April 20, 2009, 08:06:07 PM »
Man you guys are really bummin me out. I bought the Vida Rica HPS with the jig and also the Baxter buffer jig.

This was not intended to be a Vida Rica bashing thread. I think the Vida Ricas are excellent. The points I tried to make are the differences between the current Vida Ricas and what we've been used to with Kevins older style lowers, and now his newer style. The 80% Vida Ricas aren't 100% finished in any of the machining operations. But the bulk of the work *is* done. 

I've never seen the Baxter receiver or buffer jig (just the pics). I have seen and used the Tannery Shop jig. I don't use any jig to do the buffer hole; I use the upper I'm going to mate it to as a jig. There's a couple good threads here on doing the threaded buffer hole and having it line up exactly with the upper bore.

Well the only problem I have is with the baxter jig, which I'm not going to use. I've ordered the reamer from goober and will line the hole with the upper.The baxter is also a jig for the rear takedown detent and the stock index hole but i'm not sure I trust it. I'm actually happy with the vida rica, I just like having the best and if I could have had something better I get bummed that I didn't get that one. That being said, I see a yellow logic reciever in my future.      Albie