POF- UPPER /DPMS LOWER

[firechief]

I'M STARTING TO GATHER THE LAST FEW PARTS AND WANT TO BE SURE THE POF UPPER IS COMPATIBLE WITH THE DPMS PATTERN 80% LOWER I ORDERED.  oops sorry for the caps.

I read the few POF threads and see there's a problem with the carrier not kissing the face of the buffer sometimes. That should be an easy fix if true.

[Jgun]

This may not aply to you of your planning to finish your own 80% lower, But I had originally planned to put together a .308 AR rifle based on the POF .308 lower (which I really like) mated to a DPMS upper. You may already know all this, but The POF .308's use .250" takedown and pivot pins while most of the others use .277" pins. Now, when I was mating the DPMS upper (with .277" holes) to the POF lower (with .250" pins) I had to make up bushings to go into the holes in the upper in order to take the slop out of the upper/lower fit.  Your problem would be the opposite, unless your planning to machine the lower with .250 pivot and takedown pins. If so I suggest that you get yourself a set of the POF pins to check out because not only is the OD different than the Armalite or DPMS pins. but I seem to recall that the length was off which may give you trouble if you want to use the POF pins on a DPMS pattern lower.

[firechief]

Thanks, that helps a lot, so I can plan on machining down some larger pins or use the lathe to make up my own. Bushings that thin would be a bstrd to make but turning my own pins would probably be easier. 

<thumbsup>

[Jgun]

If your going to use a POF upper, (which would have .250" holes in the lugs that take the pivot and takedown pins) and your using a DPMS type lower, Your not going to need to make bushings, Your problem will be the opposite. If you use POF pins (which match the upper) You'll want to put .250" locating holes in the lower,but as I mentioned before, I would suggest that you double check to make sure the POF pin length works for you.  if you elect to go with .277" pins in the lower, you'd have to open up the holes in the POF upper to .277" (something I would strongly advise against). As far as making your own pins goes, turning the pins on the lathe is no big deal, but milling the channel for the retaining detents would be a pain (for me). Now I'm the kind of person that likes to do things differently than the other guy, so I would never second guess someone elses reasons for doing a project a certain way, but could you tell me why you have picked the POF upper/DPMS lower combination?  By the way, I'm sure you already know this, but since the POF upper is a piston operated system, you will have to use their bolt carrier group. I'm not sure how the other parts might differ from the DPMS parts, but you might do well to use the POF buffer and buffer spring to match the impulse from the piston (for proper cycling?)

[firechief]

:P

Yep, I did read the pin sizes ass backwards.

Milling a slot in a pin, not a big deal, slow feed, lots of coolant. If the POF upper has plenty of lug area material then a few thou with an adjustable blade ream to fit should be straight forward. I already hand ream my FCG pins on builds and probably have the correct ream in my set.

AS for the POF choice it's because of reading only good things about them. I could easily just go to a DPMS upper and make the first build real easy and unchallenging. Now if POF offered an 80% lower that would be nice but they don't so I accept the challenge.

Buffer's, that's going to be a learning curve for me, I'm guessing every BCG needs to be tuned since there all going to be different weights, gas, piston, plenty variables.

If it was easy it wouldn't be any fun.

I bet I end up with a butt load of extra parts for .308 just like my 5.56's, so many toys not enough storage.

[Jgun]

I'm in agreement with you. I find that my satisfaction with rhese projects seems to be in direct proportion to how many engineering obsticals I have to overcome.  When I said that cutting the slots was a problem I was referring I think more to how much labor would be needed to make a $5 pin I  don't wish

to sound like I'm second guessing you, ( see this more as an enjoyable echange of idea's) But you might want to think teice about reaming out the lugs in your POF uper to fit .277" pins from the lower. If you do that and later decide to sell or do something else with the upper, you'd have to bush it back down to .250" to use it on a POF lower, and I'm thinking you'd reduce the resale value in the process.

[Jgun]

Think I need to use spell check next time, LOL. That's what happens when I rush  a response so I can go have dinner.

[firechief]

I dreamt a solution, although it's got a draw back. Two piece take down pin with a .277 shoulder and threaded. Kinda like a fancy ambidextrous selector. Gona suck to crack it open because i'll need either a tool socket hole on the  end or design in a thumb  flipper lie a selector to unscrew it,  but saves reaming the upper. I'm gona have to give this more thought and maybe it will come to me.

Arg h, brain teaser, gona drive me nuts

I can't figure a way to get a bushing to stay reliably in the upper unless it's press fit on each side and then go to a .250 pin for the whole system, but pressing bushings that thin into place is gona definitely  need a drive tool or it will probably collapse. 

Gona need some test bench time, guess thats what makes me the special head banging type.

I bet I just ream the upper and call it sacrificed to DPMS, I doubt I'll ever sell it anyway.

Why lord didn't they just make a standard mil spec 7.62 AR for your children to enjoy !!

[Jgun]

As you say, You could actually, make a stepped pin that was .277" at the head end (where it passes through the rt side of the lower) and steps down to .250". You could then step it down further so that a .277" pin, possibly internally threaded 10-32 could screw on from the left side. That way you wouldn't have alter either the upper or lower. You also would do away with the need to slot the pins for the detente's, because they would be held in by the "caps" on the other end. You might want to have one pin come in from the right and the other coming from the left side (for strength)

[Syqraz]

So has any one attempted this. I also wanted to do this but was concerned that there are more difference than just the pin size. Can any one confirm if that’s the only difference? 

[98Z5V]

10 hours ago, Syqraz said:

So has any one attempted this. I also wanted to do this but was concerned that there are more difference than just the pin size. Can any one confirm if that’s the only difference? 

Judging that the last post on is was almost 10 years ago - we haven't heard anything like this since.  You're on Virgin Ground, if you attempt this.  Make sure you report back, so we have some closure.