09-30-2019, 01:17 AM
(This post was last modified: 10-10-2019, 02:26 PM by lazyengineer.)
There's mixed talk about how useful this really is, so I'm going to try it. I'm going to post some before/after data, and we'll see how this goes.
At present, I have a carbine gas-length 6.5 Grendel that shoots ... OK, but a bit below my standards. The gun is a PSA with a SS barrel, and has 968 rounds on it now. Reliability is excellent (though I did break an Extractor, so there's that).
I carefully took it out and shot it from a bench at 100 yards, for my "before" data. Two strings of 5 rounds each - averaged below. MR is Mean Radius, using a digital App on images of the targets:
Ranked in order of best shooting:
2.0 MOA: 129 gr SST w/ 27.8 gr Ramshot TAC: (0.8 MR)
2.2 MOA: 95 gr H Varm. w/ 27.0 gr LT-32: (0.7MR)
2.5 MOA: 90 gr TNT w/ 31.0 gr 8208: (1 MR)
2.6 MOA: Wolf Steel: (0.9 MR)
3.0 MOA: Federal 120 Gr Fusion factory: (1.2 MR)
Serviceable, but pretty MEH.
OK, so people act like lapping an upper is easy. It's not "easy". It's doable, but not the casual "easy" on par with basic simple stuff like taking apart a BCG for the gas-rings swap, or swapping out handguards. There are a few specialty tools and chemicals you're going to need for this. I do happen to have an upper vice-block, which helps. But be aware, it's a common one, and requires the ejection port flap to be closed (or removed, but you have to take off the barrel, before you can remove the ejection flap) and the optics to be removed.
So, step 1 - take off the scope (hate doing that).
Step 2 - pull off the handguard (just use allen wrench on the screws holding it on)
Step 3 - Mount into a vice, using a vice-block. which means pull out the BCG and handle, close the ejection door, and insert into the block. Then clamp down the vice.
Step 4 - Use a wrench and a decent amount of torque, to unscrew the nut.
Step 5 - Pull the barrel out of the upper. This took me a couple tries and a decent amount of force, but it came out. PSA apparently uses a rather snug fit.
(optional step - examine the barrel - the PSA barrel, crown, rifling, etc, all look quite good to the eye. Might as well give it a good cleaning while in-hand).
Step 6 - The latch of the ejection port door, will be in the way of the lapping rod (the rod goes all the way into your upper, to assure proper alignment). So... had to take it all out of the vice, and pull off the ejection port flap, which comes off easily now that the barrel is gone (the rod just slides out). And then, put back into the block and remount the upper into your vice.
Step 7 - Take out the lapping rod, oil the shaft part that goes into your upper. and put the lapping compound on the inside face, that rubs up against the ring-surface to be lapped. Chuck the whole thing in your drill. Mine came with a great big spring-shaft thing, that connects the lapping rod to the drill.
Step 8 - start drilling, occasionally reapply more lapping compound. Pull out and wipe every 10 seconds or so. I have no idea how much force to use when pushing against the upper, so I used... some.
Here's what it looks like after I'd say 45 seconds of lapping time. See how the bottom part is shiny, but the top isn't yet - which means that yes, the ring was not perfectly even, and the lapped version should in theory be more square now.
![[Image: Lapped-12-Grendel-upper-step-2-1.jpg]](https://i.postimg.cc/rFsbf00B/Lapped-12-Grendel-upper-step-2-1.jpg)
(update - it was an error to lap horizontally, as the device will tend to affect the bottom part more. So this was later repeated vertically, and described in some of the below posts)
Step 9 - keep going reapplying compound until the entire ring is shiny
Step 10 - wipe clean, oil, and put away the lapping rod
Step 11 - Thoroughly clean the upper. I used a copper cleaning brush tip to get the threads clean, which of course are coated in lapping compound. As is the inside of the upper. I then hit the threads with a jet of break-cleaner/degreaser.
Step 12 - Now you have to put the ejection port door back on (don't forget to do this). I have to say, that step was kind of a PITA, as I'm not practiced at doing that. Getting that little tip of the spring in the right spot while trying to slide the rod back in, wasn't easy. I'm sure there's an easy technique but I didn't know it.
Step 13 - Apply Anti-Sieze compound on your threads of the upper... Yea, so I checked the cupboard, and it turns out, we don't keep anti-seize next to the paper-towels after all. Sooo... project at a stop, until I get anti-sieze. Ordered whatever the standard spec is off Amazon, and it'll get here like... Wednesday. So, project now at a stop.
Also, because most common uppers today don't take a classic armors wrench, I'm not really sure how to properly torque the barrel nut back on. To take it off, I used one of these, and there's not exactly a slot for my torque socket wrench...
![[Image: large-thorsen-54032-chrome_1_8de8fc47b5d...ce27ca.jpg]](https://thumbs.worthpoint.com/zoom/images1/1/0417/07/large-thorsen-54032-chrome_1_8de8fc47b5d151ebb151ae39b8ce27ca.jpg)
(generic internet photo)
Soo, anyway, project on hold until the anti-seize gets here. While I certainly consider this project doable, it requires a number of specialty tools and potions, and involves a good bit more tear-down than an average AR15 shooter is typically going to do.
At present, I have a carbine gas-length 6.5 Grendel that shoots ... OK, but a bit below my standards. The gun is a PSA with a SS barrel, and has 968 rounds on it now. Reliability is excellent (though I did break an Extractor, so there's that).
I carefully took it out and shot it from a bench at 100 yards, for my "before" data. Two strings of 5 rounds each - averaged below. MR is Mean Radius, using a digital App on images of the targets:
Ranked in order of best shooting:
2.0 MOA: 129 gr SST w/ 27.8 gr Ramshot TAC: (0.8 MR)
2.2 MOA: 95 gr H Varm. w/ 27.0 gr LT-32: (0.7MR)
2.5 MOA: 90 gr TNT w/ 31.0 gr 8208: (1 MR)
2.6 MOA: Wolf Steel: (0.9 MR)
3.0 MOA: Federal 120 Gr Fusion factory: (1.2 MR)
Serviceable, but pretty MEH.
OK, so people act like lapping an upper is easy. It's not "easy". It's doable, but not the casual "easy" on par with basic simple stuff like taking apart a BCG for the gas-rings swap, or swapping out handguards. There are a few specialty tools and chemicals you're going to need for this. I do happen to have an upper vice-block, which helps. But be aware, it's a common one, and requires the ejection port flap to be closed (or removed, but you have to take off the barrel, before you can remove the ejection flap) and the optics to be removed.
So, step 1 - take off the scope (hate doing that).
Step 2 - pull off the handguard (just use allen wrench on the screws holding it on)
Step 3 - Mount into a vice, using a vice-block. which means pull out the BCG and handle, close the ejection door, and insert into the block. Then clamp down the vice.
Step 4 - Use a wrench and a decent amount of torque, to unscrew the nut.
Step 5 - Pull the barrel out of the upper. This took me a couple tries and a decent amount of force, but it came out. PSA apparently uses a rather snug fit.
(optional step - examine the barrel - the PSA barrel, crown, rifling, etc, all look quite good to the eye. Might as well give it a good cleaning while in-hand).
Step 6 - The latch of the ejection port door, will be in the way of the lapping rod (the rod goes all the way into your upper, to assure proper alignment). So... had to take it all out of the vice, and pull off the ejection port flap, which comes off easily now that the barrel is gone (the rod just slides out). And then, put back into the block and remount the upper into your vice.
Step 7 - Take out the lapping rod, oil the shaft part that goes into your upper. and put the lapping compound on the inside face, that rubs up against the ring-surface to be lapped. Chuck the whole thing in your drill. Mine came with a great big spring-shaft thing, that connects the lapping rod to the drill.
Step 8 - start drilling, occasionally reapply more lapping compound. Pull out and wipe every 10 seconds or so. I have no idea how much force to use when pushing against the upper, so I used... some.
Here's what it looks like after I'd say 45 seconds of lapping time. See how the bottom part is shiny, but the top isn't yet - which means that yes, the ring was not perfectly even, and the lapped version should in theory be more square now.
(update - it was an error to lap horizontally, as the device will tend to affect the bottom part more. So this was later repeated vertically, and described in some of the below posts)
Step 9 - keep going reapplying compound until the entire ring is shiny
Step 10 - wipe clean, oil, and put away the lapping rod
Step 11 - Thoroughly clean the upper. I used a copper cleaning brush tip to get the threads clean, which of course are coated in lapping compound. As is the inside of the upper. I then hit the threads with a jet of break-cleaner/degreaser.
Step 12 - Now you have to put the ejection port door back on (don't forget to do this). I have to say, that step was kind of a PITA, as I'm not practiced at doing that. Getting that little tip of the spring in the right spot while trying to slide the rod back in, wasn't easy. I'm sure there's an easy technique but I didn't know it.
Step 13 - Apply Anti-Sieze compound on your threads of the upper... Yea, so I checked the cupboard, and it turns out, we don't keep anti-seize next to the paper-towels after all. Sooo... project at a stop, until I get anti-sieze. Ordered whatever the standard spec is off Amazon, and it'll get here like... Wednesday. So, project now at a stop.
Also, because most common uppers today don't take a classic armors wrench, I'm not really sure how to properly torque the barrel nut back on. To take it off, I used one of these, and there's not exactly a slot for my torque socket wrench...
(generic internet photo)Soo, anyway, project on hold until the anti-seize gets here. While I certainly consider this project doable, it requires a number of specialty tools and potions, and involves a good bit more tear-down than an average AR15 shooter is typically going to do.
