Upper/Lower Wobble

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  • hillbilly grandpa

    Active Member
    Jan 26, 2013
    962
    Arnold
    I'm researching, finding two different approaches: shim material on the underside face of the upper, and shim washers on the pivot and takedown pins. What's the collective wisdom here, and where do you buy materials?
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,820
    By wobble, you mean side to side or front to back?

    If you can insert a .020 feeler gauge anywhere along the crack between upper and lower, that's considered a no go.
     

    ToolAA

    Ultimate Member
    MDS Supporter
    Jun 17, 2016
    10,500
    God's Country
    Some wobble is totally normal. Some people seem to obsess about it and try to shim or install Accu-Wedges to limit the wobble. In general I would say unless you are building some super precision long range rig it's probably overkill. Get a .020 gauge like Outrider58 suggested and report back.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,820
    Some wobble is totally normal. Some people seem to obsess about it and try to shim or install Accu-Wedges to limit the wobble. In general I would say unless you are building some super precision long range rig it's probably overkill. Get a .020 gauge like Outrider58 suggested and report back.

    Yup.

    Worse thing people do is put the "little red rubber ball" under the rear takedown pillar.
     

    Bob A

    όυ φροντισ
    MDS Supporter
    Patriot Picket
    Nov 11, 2009
    30,695
    Barrel, upper receiver and sight mounts are all one tightly-assembled hunk of gun. As long as the sight picture stays on target, the lower wobble shouldn't make any difference, seems to me.
     

    SkiPatrolDude

    Ultimate Member
    MDS Supporter
    Oct 24, 2017
    3,332
    Timonium-Lutherville
    I just went through this with two spikes lowers attached to two PSA uppers. Wobble and audible rattle with standard pins, so I went to JP Rifles website and purchased an "Extra Oversized" front and rear takedown pin. Now, these are the tightest receiver sets in my collection. The front pin does need a small plastic punch to get out, but the rear can still be pushed out with the thumb for quick field strip. I suspect the front pin will get easier with use.

    They sell the oversized pins as a set, but for me it didnt eliminate the wobble completely. The extra oversized were the ticket, but they make you purchase the front and rear pin separately. Just FYI.

    I can deal with wobble but I could not stand the rattle cans these things were. Super happy with the JP extra oversized pins. Super nice fit and finish, too.

    I think the oversized are .249 and the extra are .250.

    I know people praise the accu wedge, but to me they aren't a real fix.
     

    hobiecat590

    Ultimate Member
    MDS Supporter
    Feb 2, 2016
    2,436
    Areoprecision (sp?) has a lower that has an adjustable bearing designed to take the slop out and eliminate the need for an Accu-Wedge. Anybody try these lowers?

    Joe Carlos in the "American Gunsmith" Vol XXXII-#4. April 2017, page 7, has a great article on the Accu-Wedge, tension pins and Brownells shims etc. He claims a 26% average group reduction from a machine rest using the $5 Accu-Wedges while he was with the Army Reserve Shooting Team. YMMV
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    If it matters to you, bed the upper to the lower with one of the typical stock bedding compounds. Use some release agent on the rear lug on the upper. Bed the rear lug to the lower.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,820
    I just went through this with two spikes lowers attached to two PSA uppers. Wobble and audible rattle with standard pins, so I went to JP Rifles website and purchased an "Extra Oversized" front and rear takedown pin. Now, these are the tightest receiver sets in my collection. The front pin does need a small plastic punch to get out, but the rear can still be pushed out with the thumb for quick field strip. I suspect the front pin will get easier with use.

    They sell the oversized pins as a set, but for me it didnt eliminate the wobble completely. The extra oversized were the ticket, but they make you purchase the front and rear pin separately. Just FYI.

    I can deal with wobble but I could not stand the rattle cans these things were. Super happy with the JP extra oversized pins. Super nice fit and finish, too.

    I think the oversized are .249 and the extra are .250.

    I know people praise the accu wedge, but to me they aren't a real fix.

    Areoprecision (sp?) has a lower that has an adjustable bearing designed to take the slop out and eliminate the need for an Accu-Wedge. Anybody try these lowers?

    Joe Carlos in the "American Gunsmith" Vol XXXII-#4. April 2017, page 7, has a great article on the Accu-Wedge, tension pins and Brownells shims etc. He claims a 26% average group reduction from a machine rest using the $5 Accu-Wedges while he was with the Army Reserve Shooting Team. YMMV

    Both 'solutions' open up the gap. If you're looking for a solution that will close the gap/wobble, JP makes a rear expandable pin, but is cumbersome. Demon Tactical makes a more user friendly rear pin, but in both cases, the pin must expand horizontally. Otherwise, the pin can rotate inside the ovate rear pin pillar and become loose again.

    Still waiting to hear from OP
     

    Doco Overboard

    Ultimate Member
    I think an accu wedge will show a difference with and without when you check your AR rifle. I used to put one in when I used the bob sled for single load. I believed the lack of pressure from the loaded mag made me shoot low and it did to some extent when I used to shoot that type of rifle alot.
    Youll really notice it from the bench with a front rest and then again while using a sling. Maybe for some but not for all.
    I tried out a bolt rifle i just put together last week and it was 4 moa from the bench and then to the mat but that's entirely different from an AR but same thing really.
     

    babalou

    Ultimate Member
    MDS Supporter
    Aug 12, 2013
    16,022
    Glenelg
    rubber ball feeler gauge

    Yup.

    Worse thing people do is put the "little red rubber ball" under the rear takedown pillar.

    himm. Not the feeler gauge size you like to use and the red ball gag that looks like your avatar nose. hahaha. j/k brah. hope you and fam doing well.
     

    SkiPatrolDude

    Ultimate Member
    MDS Supporter
    Oct 24, 2017
    3,332
    Timonium-Lutherville
    Both 'solutions' open up the gap. If you're looking for a solution that will close the gap/wobble, JP makes a rear expandable pin, but is cumbersome. Demon Tactical makes a more user friendly rear pin, but in both cases, the pin must expand horizontally. Otherwise, the pin can rotate inside the ovate rear pin pillar and become loose again.

    Still waiting to hear from OP

    I can't explain why, but the oversized pins actually closed the gap for me. With the extra oversized pins, there is almost zero gap. Can see a very tiny bit of light towards the rear takedown pin, but the oversized pins seemed to really force the upper into the lower receiver.

    After trying the accuwedge, I can say I much prefer the pins.

    The major downside to the expandable pin is that you cannot field strip the rifle without a tool.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,820
    I can't explain why, but the oversized pins actually closed the gap for me. With the extra oversized pins, there is almost zero gap. Can see a very tiny bit of light towards the rear takedown pin, but the oversized pins seemed to really force the upper into the lower receiver.

    After trying the accuwedge, I can say I much prefer the pins.

    The major downside to the expandable pin is that you cannot field strip the rifle without a tool.

    I think it depends on what is 'loose'. Is it the upper receiver or the lower?

    Demon pins require no tools. My point about the horizontal expansion is, the hole in the rear pillar is ovate. If you expand the pin vertically, it will tend to rotate horizontally and become loose again. This is all supposition until we hear back from OP.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    Joe Carlos in the "American Gunsmith" Vol XXXII-#4. April 2017, page 7, has a great article on the Accu-Wedge, tension pins and Brownells shims etc. He claims a 26% average group reduction from a machine rest using the $5 Accu-Wedges while he was with the Army Reserve Shooting Team. YMMV

    Machine rest probably clamped the lower.

    Since the sights are on the upper, with the barrel and bolt, any slop between the two in normal operation should not have an effect, unless there is a LOT.
     

    grimnar15

    Ultimate Member
    MDS Supporter
    Jul 21, 2019
    1,645
    I'm researching, finding two different approaches: shim material on the underside face of the upper, and shim washers on the pivot and takedown pins. What's the collective wisdom here, and where do you buy materials?

    Buy Sons Of Liberty Gun Works upper and lower receiver Combo and there is no wobble.
     

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