planeflyer21 Posted February 14, 2013 Report Share Posted February 14, 2013 If the manufacturer of the aluminum gas block has properly hard anodized the aluminum, wear shouldn't be an issue.Jon Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted February 15, 2013 Author Report Share Posted February 15, 2013 Sure, they take calls. Talked to them a week and a half ago, about the timeline between ordering and shipping for the 308 matched upper/lower. Their answer was: Every order placed right now will be ready to ship somewhere between 3 and 4 months.They'll answer, you just need to be persistant. I got through the first try.There's a thread pinned in the DPMS section that tells you how/what to measure. Thanks, I got my barrel today so I thought i would measure while I had it out. I found the sticky and also several other sites say the same thing."To find out if you have a newer model or older run, the easiest way to measure is with a caliper from the bottom surface that mates to the lower to the top of the rail. The new versions measure 2.003 and the old versions are 2.063. "Mine is 2.083 so i guess this tells me nothing... Quote Link to comment Share on other sites More sharing options...
Jgun Posted February 15, 2013 Report Share Posted February 15, 2013 You have a new model. It might be out of spec. (don't know what tolerance they allow), but as long a s you don't try to mount an optic that bridges the upper and the top rail of the handguard (never a good idea), .020" shouldn't cause you any trouble. Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted February 15, 2013 Author Report Share Posted February 15, 2013 You have a new model. It might be out of spec. (don't know what tolerance they allow), but as long a s you don't try to mount an optic that bridges the upper and the top rail of the handguard (never a good idea), .020" shouldn't cause you any trouble.I hear what your saying but I didn't pay $650 (on sale) for out of spec billet matched set and it is not acceptable. I will contact JD and see what they say. Quote Link to comment Share on other sites More sharing options...
EasyEJL Posted February 15, 2013 Report Share Posted February 15, 2013 I don't know that given the lack of standardization of the 308 AR platform that you can call a slight difference in the height of a rail "out of spec". Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted February 15, 2013 Author Report Share Posted February 15, 2013 I don't know that given the lack of standardization of the 308 AR platform that you can call a slight difference in the height of a rail "out of spec".It's enough to make me dump the project... I dunno maybe their lower is a different spec for their matched set and everything will line up, I don't know why they would do that though... I guess I will find out if they ever get back to me. It might require me to drive down there to get an answer though, they are about an hour from my house and I had to make 2 trips just to pickup the lower because they don't answer phones or emails anymore. I have contact info for someone there, but they are usually slow to answer as well. Quote Link to comment Share on other sites More sharing options...
Jgun Posted February 15, 2013 Report Share Posted February 15, 2013 When I said out of spec, I was referring to their design specification. As stated above, being that there is no mil spec as with the small platform, Mfgs can do anything they want, an example would be DPMS deciding a couple of years ago to raise the height of the rail on their uppers .060". As I recall, some of the rail manufactures adjusted and offered an old style and new style DPMS rail, but some chose not to. I don't know what JD's designed upper rail height is, but it ought to match the height of some Mfgs rail, if not I would say it's "out of spec" . I would think that if it is they ought tp replace it with one that will match the height of a standard (new style?) DPMS compatible rail. Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted February 15, 2013 Author Report Share Posted February 15, 2013 When I said out of spec, I was referring to their design specification. As stated above, being that there is no mil spec as with the small platform, Mfgs can do anything they want, an example would be DPMS deciding a couple of years ago to raise the height of the rail on their uppers .060". As I recall, some of the rail manufactures adjusted and offered an old style and new style DPMS rail, but some chose not to. I don't know what JD's designed upper rail height is, but it ought to match the height of some Mfgs rail, if not I would say it's "out of spec" . I would think that if it is they ought tp replace it with one that will match the height of a standard (new style?) DPMS compatible rail.Actually DPMS lowered their rail, but I do agree, they should meet some DPMS spec lower or taller, since they don't really offer complete rifles it would make no sense to have a rail that isn't flush with other existing parts, and I would consider it "out of spec" Of course this is all speculation because I do not have a way to do the measurement properly (from the centerline of the barrel)...I have seen several completed JD rifles in a 308 ar thread on Calguns and all their rails are flush. Maybe if the matched set uses a non standard lower then the rail could end up the proper height but that is rather strange to imagine as well. If the upper was taller on the bottom portion rather than the top where the rail is, then the rails could still line up, but then I think the lower would have to be shorter for the trigger to work correctly, That's why I think mine might not be correct. Quote Link to comment Share on other sites More sharing options...
Jgun Posted February 16, 2013 Report Share Posted February 16, 2013 OK, please bear with me if I've got my facts mixed up. As I understand it you are taliking about a JD upper (of which I have not worked on). I may be mistaken, but as I remembered it, DPMS raised their rail not lowered it, but I could have it wrong. I recall buying one and it being high and having to locate an older upper to complete the build. Now, the way you are measuring may not be the best way. All of the DPMS pattern uppers should measure the same from the center of the BC bore to the mating surface of the upper/lower. Where they will vary will be from the BC bore to the top of the rail. I do not have the exact measurements but I saw a tutorial on one of the handguard Mfgs site's where they told you to measure from the top of the rail to the surface of the upper where the charging handle mounts. I thought that on the older DPMS pattern uppers this dimension was be smaller than on the newer DPMS uppers. the point is that the relation between the barrel bore and the location of the trigger have not been altered (and are the same between Armalite and DPMS AFAIK) the only thing that was changed was the raising of the height of the top rail in relation to the barrel centerline. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted February 16, 2013 Report Share Posted February 16, 2013 OP, just measure the tab on the back of the upper receiver - much easier. That's described in the thread, and has a picture. <thumbsup> That gives you a height-over-bore measurement, but from the top of the BCG instead of from the center of the BCG.Also, when doing precision measurement, the first thing you do it calibrate, or check, your measuring equipment. Not saying this is the case here, with you, but if you're coming up with a non-standard measurement, the first thing you go back to is the measuring device, and check it, before going any further. Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted February 17, 2013 Author Report Share Posted February 17, 2013 OP, just measure the tab on the back of the upper receiver - much easier. That's described in the thread, and has a picture. <thumbsup> That gives you a height-over-bore measurement, but from the top of the BCG instead of from the center of the BCG.Also, when doing precision measurement, the first thing you do it calibrate, or check, your measuring equipment. Not saying this is the case here, with you, but if you're coming up with a non-standard measurement, the first thing you go back to is the measuring device, and check it, before going any further.I'll give it a shot.Anyone know if this will work under the JP Handguard?http://shopwilsoncombat.com/Adjustable-Lo-Profile-Gas-Block-937-Rifle-Length-Straight-Gas-Tube/productinfo/TR-AGBL-R/Will any of these straigth gas tube systems work or will I need a larger diameter handguard?I can't find any specs... Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted March 6, 2013 Author Report Share Posted March 6, 2013 (edited) Just an update: I ended up going with the wilson combat adjustable gas block. The finish is nice and it hasa frontal gas adjustment screw so that the handguard will not interfear. That said I also picked up a syrac ordinance gas block for my AR15. The Syrac block is a work of art. The precision of the machining is amazing. The Wilson combat has a similar fit an finish to the Syrac, but I'm not sure abou tit because it only has a set screw option. I'm hoping the clamp on style of the Syrac block eliminates my short stroking issue on my AR-15 (Had a troy LP gas block on there before). It seemed SUPER secure. I hope I don't have any issues with the wilson block being a set screw style like the troy... I don't have the JP Handguard yet because they are backordered for another month or so still. But once I get it I will confirm that it fits properly. Edited March 20, 2013 by Justintoxicated Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.