Lr-308FUn Posted September 6, 2019 Report Share Posted September 6, 2019 I got a foster field gauge, I tried it out & it doesn't close on the gauge, I have about .20" space when BCG goes forward, even tried to use the FA to push it gently to see if it would go. Nothing solid lock up at that .20" gap. (see pics) I went with a field gauge cause when I build it I didn't head space the rifle before firing. I got around 300+ round I think through this, my note book I had all my info in on this rifle got wet at the range & was soaked. Couldn't read it, sucked. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted September 6, 2019 Report Share Posted September 6, 2019 13 minutes ago, Lr-308FUn said: I got a foster field gauge, I tried it out & it doesn't close on the gauge, I have about .20" space when BCG goes forward, even tried to use the FA to push it gently to see if it would go. Nothing solid lock up at that .20" gap. (see pics) I went with a field gauge cause when I build it I didn't head space the rifle before firing. I got around 300+ round I think through this, my note book I had all my info in on this rifle got wet at the range & was soaked. Couldn't read it, sucked. You already shot it? Didn't blow up in your face? Guess headspacing it doesn't matter much, then, all things considered. It's a Forster gauge - you bought ONE, and it was the Field Gauge? Wrong one for you. There are three headspace gauges, GO, NO-GO, and FIELD. Go gauge, chambers, NO-GO gauge doesn't chamber. They're usually sold in sets of both of them. That is what you need to determine in a new build - it clears the good one, doesn't clear the bad one. FIELD gauge is for in-service weapons ONLY, that are already functional. You ONLY use the field gauge on an in-service weapon that fails the NO-GO gauge. If the in-service weapon fails the NO-GO gauge, you test it with the FIELD gauge - if it DOES NOT chamber the FIELD gauge - that in-service weapon is still good to go. If that in-service weapon DOES chamber/eat the FIELD gauge - then you need a new barrel. You used the wrong tool for this job... Quote Link to comment Share on other sites More sharing options...
Lr-308FUn Posted September 6, 2019 Author Report Share Posted September 6, 2019 I was told that since I have several hundred round through it that a field guage would be needed. I guess you learn something new daily. Also to check as I shoot to make sure headspace stays true. I guess I could trade it for a NO-go gauge. I guess though since I didn't gauge it after I built it, since I thought it was like the AR15 which I have never headspaced any of those builds either. Oops. So am I still go to go since it didn't close on the field guage or should I still try a no go just to make sure. Quote Link to comment Share on other sites More sharing options...
willbird Posted September 6, 2019 Report Share Posted September 6, 2019 6 hours ago, Lr-308FUn said: I was told that since I have several hundred round through it that a field guage would be needed. I guess you learn something new daily. Also to check as I shoot to make sure headspace stays true. I guess I could trade it for a NO-go gauge. I guess though since I didn't gauge it after I built it, since I thought it was like the AR15 which I have never headspaced any of those builds either. Oops. So am I still go to go since it didn't close on the field guage or should I still try a no go just to make sure. Headspace ideally should not change. The only way it can is if something is wearing rapidly, or something important is being stressed past it's yield point, both are very BAD things IMHO. IMHO you have established that it is not really really bad :-), you shot it, and it works. At this point if you were reloading your brass over and over if it was at "no go" headspace your brass would not last as long, especially if you full length sized it back to SAAMI dimensions each time. You can get a SWAG idea of how much headspace you have with your ammo of choice by putting layers of address label on the back of a loaded round (observing all safety protocols) and see how many layers you can apply until the gun will not go into battery. Far more people check their guns than check their ammo, but if you think about it if excessive headspace is a terrible danger, there are two sources of it, a "long" gun or "short" ammo. Friend was or is a Thompson Center sponsored shooter, they took guns and ammo to Canada for a hunt, got a lot of "click" with an eventual "boom" if you kept trying the rounds. The issue was indeed excessive headspace, but the factory AMMO was the culprit not the guns, the guns were perfect. Bill Quote Link to comment Share on other sites More sharing options...
mrraley Posted September 6, 2019 Report Share Posted September 6, 2019 Well we do have proper instructions listed here that would explain everything you might need to know... Like here -----> Head space tech note Quote Link to comment Share on other sites More sharing options...
Lr-308FUn Posted September 6, 2019 Author Report Share Posted September 6, 2019 4 hours ago, mrraley said: Well we do have proper instructions listed here that would explain everything you might need to know... Like here -----> Head space tech note Thanks for the info. I really didn't think that there is much difference between the AR15/AR10, Lr-308 when it came to head spaceing the rifle. I am glad though that the field gauge didn't close, but I would like to still use a no-go gauge, just for peace of mind. Quote Link to comment Share on other sites More sharing options...
COBrien Posted September 6, 2019 Report Share Posted September 6, 2019 (edited) 1 hour ago, Lr-308FUn said: Thanks for the info. I really didn't think that there is much difference between the AR15/AR10, Lr-308 when it came to head spaceing the rifle. I am glad though that the field gauge didn't close, but I would like to still use a no-go gauge, just for peace of mind. Headspacing is a very real concern with large-frame AR-pattern rifles. Even using quality parts from reputable manufacturers, you can have an issue. I'm extremely fortunate that my "CSASS" rifle (Gibbz upper, Criterion barrel, Next Level BCG) didn't blow up in my face the first time I took it out. Chambered a round (or so I thought, from behind the rifle), dropped the hammer, and got a "click." Had to mortar the unfired cartridge out. I could swear I checked the headspace after I completed the build, but apparently I didn't. If I had, I would have known there was an issue. After checking the headspace, where the rifle wouldn't go into battery on a GO gauge, I sent the upper to Criterion to have a bolt fitted for it. I'd highly recommend having a full set of Forster headspace gauges (GO, NOGO, and Field), or at least GO and NOGO, for large-frame ARs. In my case, if I'd only had a NOGO and Field gauge, I still wouldn't have discovered the issue I had. Because, well, the bolt isn't supposed to close on either of those gauges. But it is supposed to close on a GO gauge. Edited September 6, 2019 by COBrien Quote Link to comment Share on other sites More sharing options...
willbird Posted September 7, 2019 Report Share Posted September 7, 2019 6 hours ago, COBrien said: Headspacing is a very real concern with large-frame AR-pattern rifles. Even using quality parts from reputable manufacturers, you can have an issue. I'm extremely fortunate that my "CSASS" rifle (Gibbz upper, Criterion barrel, Next Level BCG) didn't blow up in my face the first time I took it out. Chambered a round (or so I thought, from behind the rifle), dropped the hammer, and got a "click." Had to mortar the unfired cartridge out. I could swear I checked the headspace after I completed the build, but apparently I didn't. If I had, I would have known there was an issue. After checking the headspace, where the rifle wouldn't go into battery on a GO gauge, I sent the upper to Criterion to have a bolt fitted for it. I'd highly recommend having a full set of Forster headspace gauges (GO, NOGO, and Field), or at least GO and NOGO, for large-frame ARs. In my case, if I'd only had a NOGO and Field gauge, I still wouldn't have discovered the issue I had. Because, well, the bolt isn't supposed to close on either of those gauges. But it is supposed to close on a GO gauge. But if you had you taken the BCG apart and tried a ctg in the chamber and observed that the bolt itself would not rotate by hand into battery you would have known then that either that ammunition was long or your headspace was short ;-)....or some of both ;-). Bill Quote Link to comment Share on other sites More sharing options...
COBrien Posted September 7, 2019 Report Share Posted September 7, 2019 1 hour ago, willbird said: But if you had you taken the BCG apart and tried a ctg in the chamber and observed that the bolt itself would not rotate by hand into battery you would have known then that either that ammunition was long or your headspace was short ;-)....or some of both ;-). Bill True. I never said a GO gauge was the only way to get it done. But I have a tool specifically for that purpose. I’m a tool queer, and I freely admit it. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted September 7, 2019 Report Share Posted September 7, 2019 37 minutes ago, COBrien said: I’m a tool queer, and I freely admit it. I'm completely saving this for later... Quote Link to comment Share on other sites More sharing options...
98Z5V Posted September 7, 2019 Report Share Posted September 7, 2019 22 hours ago, Lr-308FUn said: I was told that since I have several hundred round through it that a field guage would be needed. You would need thousands and thousands of rounds through your barrel, before a Field gauge would be necessary. MANY thousands of rounds. You would need to put a rifle in service, and shoot it (perfectly, for years) until it hit the point of certain malfunctions - before that would lead you to using a Field gauge to test it. Quote Link to comment Share on other sites More sharing options...
COBrien Posted September 7, 2019 Report Share Posted September 7, 2019 6 hours ago, 98Z5V said: I'm completely saving this for later... No problem. So long as the quote is all there every time it’s used... Quote Link to comment Share on other sites More sharing options...
DNP Posted September 7, 2019 Report Share Posted September 7, 2019 Damn auto correct it changed tool to total when I reposted it.... Quote Link to comment Share on other sites More sharing options...
willbird Posted September 7, 2019 Report Share Posted September 7, 2019 9 hours ago, COBrien said: True. I never said a GO gauge was the only way to get it done. But I have a tool specifically for that purpose. I’m a tool queer, and I freely admit it. Thank you for sharing :-). Just overall I just encourage folks to think about the whole situation:-). It still makes me ponder that people obsess about gun headspace but never give ammunition headspace a second thought 🙂 Bill Quote Link to comment Share on other sites More sharing options...
Lr-308FUn Posted September 7, 2019 Author Report Share Posted September 7, 2019 Well thanks for all the information, I guess you can say I got lucky & got some quality parts. It still gives me a relief that it didn't close on the Field gauge. I knew I should have just got the set. Upon looking at my order from Amazon It did say No go gauge on the discription of the gauge that I was supposed to get. Oh, well. So would it matter now if I got a No go gauge & still checked it? Quote Link to comment Share on other sites More sharing options...
Lr-308FUn Posted September 7, 2019 Author Report Share Posted September 7, 2019 On 9/6/2019 at 10:06 AM, willbird said: Headspace ideally should not change. The only way it can is if something is wearing rapidly, or something important is being stressed past it's yield point, both are very BAD things IMHO. IMHO you have established that it is not really really bad :-), you shot it, and it works. At this point if you were reloading your brass over and over if it was at "no go" headspace your brass would not last as long, especially if you full length sized it back to SAAMI dimensions each time. You can get a SWAG idea of how much headspace you have with your ammo of choice by putting layers of address label on the back of a loaded round (observing all safety protocols) and see how many layers you can apply until the gun will not go into battery. Far more people check their guns than check their ammo, but if you think about it if excessive headspace is a terrible danger, there are two sources of it, a "long" gun or "short" ammo. Friend was or is a Thompson Center sponsored shooter, they took guns and ammo to Canada for a hunt, got a lot of "click" with an eventual "boom" if you kept trying the rounds. The issue was indeed excessive headspace, but the factory AMMO was the culprit not the guns, the guns were perfect. Bill What's the number of layers to tell if it's out or gtg. Just curious I might try this. Would name tag labels work? Quote Link to comment Share on other sites More sharing options...
willbird Posted September 8, 2019 Report Share Posted September 8, 2019 20 hours ago, Lr-308FUn said: What's the number of layers to tell if it's out or gtg. Just curious I might try this. Would name tag labels work? It is not a hard science really, just a way to get a rough measurement of how much headspace there is with that individual round, you would have to measure the labels you have and see how thick they are. More or less you are creating a peel washer in reverse by adding layers. It is a good method to know of you were to pick up an 8mm Rast and Gasser revolver and suspected it had excessive headspace (yes that is a real ctg hehe)...something totally off the wall that no headspace gauges are avail for. Bill Quote Link to comment Share on other sites More sharing options...
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