COBrien Posted June 15, 2018 Report Share Posted June 15, 2018 Working on building up my CSASS-type rifle, and realized I might need/want to lap the front of the upper receiver. This is a DPMS-pattern build. PTG makes an "AR-10" upper receiver lapping tool... http://pacifictoolandgauge.com/ar-tools/10318-ar-15-upper-receiver-lapping-tool.html If this is, truly, an AR-10 tool, is there any reason (I.D. of the receiver, specifically) it shouldn't work for an LR-308 pattern receiver? Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted June 15, 2018 Report Share Posted June 15, 2018 I have used that tool for a Matrix and Fulton Armory uppers, both LR-308's, with excellent results. The Fulton might not count as it was very even to start, more confirmed it was square than squared it. 8 minutes ago, COBrien said: If this is, truly, an AR-10 tool, is there any reason (I.D. of the receiver, specifically) it shouldn't work for an LR-308 pattern receiver? Quote Link to comment Share on other sites More sharing options...
COBrien Posted June 15, 2018 Author Report Share Posted June 15, 2018 Just now, jtallen83 said: I have used that tool for a Matrix and Fulton Armory uppers, both LR-308's, with excellent results. The Fulton might not count as it was very even to start, more confirmed it was square than squared it. My upper will be Fulton, as well, so that's great to know! As an aside, I recently lapped 2 Fulton AR-15 uppers. One was perfect from the start -- perfectly round shiny spot after "touching" it with the lapping tool, just as a guide. The second one, on the other hand, was a beast... Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted June 15, 2018 Report Share Posted June 15, 2018 Just now, COBrien said: The second one, on the other hand, was a beast... Two DPMS AR-15 uppers pretty much ruined my AR-15 lapping tool they needed so much off. These tools are an expendable thing unless you get a machinist to reface them after wearing a groove and they would most likely charge as much or more than a new tool. Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted June 15, 2018 Report Share Posted June 15, 2018 13 minutes ago, jtallen83 said: These tools are an expendable thing unless you get a machinist to reface them after wearing a groove and they would most likely charge as much or more than a new tool. I know a machinist who would do it for you free if you paid the shipping cost. Quote Link to comment Share on other sites More sharing options...
COBrien Posted June 15, 2018 Author Report Share Posted June 15, 2018 58 minutes ago, Matt.Cross said: I know a machinist who would do it for you free if you paid the shipping cost. Bookmarking this post... ? Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted June 15, 2018 Report Share Posted June 15, 2018 1 hour ago, Matt.Cross said: I know a machinist who would do it for you free if you paid the shipping cost. If I hear of some of those carrier weights becoming available I might drop it in the mail so the shipping can be cost averaged a bit, suckers are heavy! Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted June 15, 2018 Report Share Posted June 15, 2018 12 minutes ago, jtallen83 said: If I hear of some of those carrier weights becoming available I might drop it in the mail so the shipping can be cost averaged a bit, suckers are heavy! I can make you a one-off any time. Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted June 15, 2018 Report Share Posted June 15, 2018 1 minute ago, Matt.Cross said: I can make you a one-off any time. Can you do both large and small frame versions? I may just take you up on that come late summer/early fall when I will be around home a bit. Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted June 15, 2018 Report Share Posted June 15, 2018 16 minutes ago, jtallen83 said: Can you do both large and small frame versions? I may just take you up on that come late summer/early fall when I will be around home a bit. Sure can, as far as I know there's no difference in the specs, but that's a trivial problem if any. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted June 15, 2018 Report Share Posted June 15, 2018 39 minutes ago, jtallen83 said: If I hear of some of those carrier weights becoming available I might drop it in the mail so the shipping can be cost averaged a bit, suckers are heavy! 22 minutes ago, jtallen83 said: Can you do both large and small frame versions? They're identical - same part, dimensions don't change. I have one in a 16" 5.56 precision gun, and one in a LR-308. Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted June 15, 2018 Report Share Posted June 15, 2018 26 minutes ago, Matt.Cross said: Sure can, as far as I know there's no difference in the specs, but that's a trivial problem if any. 20 minutes ago, 98Z5V said: They're identical - same part, dimensions don't change. I have one in a 16" 5.56 precision gun, and one in a LR-308. Can they be made in different weights? Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted June 15, 2018 Report Share Posted June 15, 2018 1 minute ago, jtallen83 said: Can they be made in different weights? Long answer short, yes. It's basically a housing that carries different weight inserts. You can use the housing by itself, or in conjunction with inserts of various types and weights. Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted June 15, 2018 Report Share Posted June 15, 2018 If there's a lot of interest in this, I'll go ahead and make a batch of them. I just need numbers for how many everyone wants. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted June 15, 2018 Report Share Posted June 15, 2018 29 minutes ago, jtallen83 said: Can they be made in different weights? 1. Housing alone. 2. Housing with steel insert. 3. Housing with Tungsten insert. 3 total possibilities. Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted June 16, 2018 Report Share Posted June 16, 2018 1 hour ago, 98Z5V said: 1. Housing alone. 2. Housing with steel insert. 3. Housing with Tungsten insert. 3 total possibilities. Tungsten, Carbide, Steel, Aluminum, Plastic.... The insert possibilities are endless, the housing necessarily needs to be machinable, but there's also many possibilities there. Quote Link to comment Share on other sites More sharing options...
COBrien Posted June 21, 2018 Author Report Share Posted June 21, 2018 Just to bring this thread full-circle... I ordered one of the PTG tools last night. Quote Link to comment Share on other sites More sharing options...
COBrien Posted June 25, 2018 Author Report Share Posted June 25, 2018 Now, then, we know this will work in DPMS-pattern uppers. Will it work in Armalite uppers? I have a buddy who's just bought a complete AR-10 who wants to install a JP handguard on it. While we've got it apart, I'd like to lap the upper for him. Does anyone have a blueprint and/or measurements for the I.D. of an LR-308 upper vs. an AR-10 upper? Quote Link to comment Share on other sites More sharing options...
98Z5V Posted June 25, 2018 Report Share Posted June 25, 2018 2 hours ago, COBrien said: Now, then, we know this will work in DPMS-pattern uppers. Will it work in Armalite uppers? I have a buddy who's just bought a complete AR-10 who wants to install a JP handguard on it. While we've got it apart, I'd like to lap the upper for him. Does anyone have a blueprint and/or measurements for the I.D. of an LR-308 upper vs. an AR-10 upper? Blueprint not necessary. It will work. I have an AR-10 barrel mounted in a DPMS-based rifle - fits. It'll work. Quote Link to comment Share on other sites More sharing options...
COBrien Posted June 25, 2018 Author Report Share Posted June 25, 2018 1 hour ago, 98Z5V said: Blueprint not necessary. It will work. I have an AR-10 barrel mounted in a DPMS-based rifle - fits. It'll work. 'Preciate that, brother! Quote Link to comment Share on other sites More sharing options...
willbird Posted December 16, 2018 Report Share Posted December 16, 2018 (edited) The problem with lapping an anodized surface is how hard the surface is. Some say it is as hard as sapphire. IMHO looking at the tool you could lay a emery cloth on something truly flat, say plate glass, and carefully dress it flat again. A lap works be embedding the abrasive into it...but there is a contest between the lap and the work, if the abrasive becomes embedded into the work (because it is softer than the lap) then the work starts cutting the lap. With a hard anodized aluminum part the anodized surface is very hard, the aluminum underneath is very soft (in comparison). So once you get through the anodize odds are that the abrasive loads into the aluminum then starts lapping the tool. One thing that will help is to make sure there is NO loose abrasive present. A lap should be loaded with abrasive then any loose abrasive should be rinsed off. There is a lot more to lapping than meets the eye :-). Many folks at first think that a huge amount of loose paste between the two parts is what is wanted/needed, the reverse is true. Loose abrasive is an uncontrolled process basically. Bill Edited December 16, 2018 by willbird Quote Link to comment Share on other sites More sharing options...
willbird Posted December 16, 2018 Report Share Posted December 16, 2018 Before surface grinders and magnetic chucks became so good and widespread most fine finishing was done by lapping, ultra fine finishing still is. But old school was to have 3 lapping plates, and with 3 of them you can work with them and make them all flat. They still use a lapping process to come in and make granite surface plates flat again. For the receiver lapping tool cast iron might actually be a very good material choice for the portion that does the cutting once loaded with abrasive. No reason you could not have a series of laps to use on that tool, keeping one for the final finish..and others to do the rough work if needed. Bill Quote Link to comment Share on other sites More sharing options...
Russdog12 Posted August 29, 2021 Report Share Posted August 29, 2021 On 6/15/2018 at 1:43 PM, Matt.Cross said: I know a machinist who would do it for you free if you paid the shipping cost. Hi Matt, I sent you a an Email on this Forum. Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted August 29, 2021 Report Share Posted August 29, 2021 5 hours ago, Russdog12 said: Hi Matt, I sent you a an Email on this Forum. Yes, and thank you for doing so. I've changed jobs quite recently and no longer have access to the required equipment, unfortunately... Quote Link to comment Share on other sites More sharing options...
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