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Posted: 7/9/2012 11:27:41 AM EDT
| My Daniel Defense DDM4V3 just passed 11,000 rounds, and yesterday when cleaning it, I noticed one of the lugs has a small crack on the corner of its front edge. I have a new BCM bolt and carrier sitting here ready to go in. Do I need to do anything other than put it in and check the headspacing with go/no-go gauges? No need to change the barrel/barrel extension, right? (I searched and haven't found any direct answers to this question...just a lot of arguing over 'if it isn't broke, don't fit it.') |
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Thanks for the input. I have gauges in the mail on their way to me...I will see if the new bolt/old barrel measure in spec.
I know the barrel should be pretty well shot-out, but it still holds under an MOA on sand bags with match ammo (100m target distance). That is about the same as it did when new. I wasn't planning on changing the barrel until my accuracy went downhill. |
Just as an update for future searches - my headspace gauge arrived and both the new bolt and old bolt are well under the maximum value. I will shoot her some more this weekend with the new bolt (and Geissele SSA trigger that the mailman also brought  ).
Thanks to all for the help! |
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I think I would contact DD and let them know.DD might replace the bolt,and very possibly would like to have your old bolt for T&E.
Their quality assurance policy is a force in my experience. ETA I'd just replace the bolt. No need to replace the carrier unless it has an issue as well. Save the new BCM carrier for another build or as a emergency spare. |
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What are you calling max value? Which gage passed and which gage failed for a given combination of bolt/barrel? Just curious. 11k is a lot. I was using the Brownells 1.4736" 5.56mm "Colt Headspace Gauge." From what I read, 1.4736" is the maximum permissible value. All combinations failed to 'lock' on the gauge... and were far from locking. Out of curiosity more than anything, I am going to pick up an 11 piece Forster Gaige set to get an actual measurement. 11k really isn't that much if you shoot a few hundred rounds every other weekend. 
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What are you calling max value? Which gage passed and which gage failed for a given combination of bolt/barrel? Just curious. 11k is a lot. I was using the Brownells 1.4736" 5.56mm "Colt Headspace Gauge." From what I read, 1.4736" is the maximum permissible value. All combinations failed to 'lock' on the gauge... and were far from locking. Out of curiosity more than anything, I am going to pick up an 11 piece Forster Gaige set to get an actual measurement. 11k really isn't that much if you shoot a few hundred rounds every other weekend. I only use a USGI Field Reject.The Colt Field II from Brownells is a bit larger,but beyond that its all you need to know...pass or fail on the field reject.So I wouldn't worry about exact headspace,muchless spend the kind of money a full set of headspace gages will cost you.Otherwise save your money for more ammo etc. and continue on. |
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What are you calling max value? Which gage passed and which gage failed for a given combination of bolt/barrel? Just curious. 11k is a lot. I was using the Brownells 1.4736" 5.56mm "Colt Headspace Gauge." From what I read, 1.4736" is the maximum permissible value. All combinations failed to 'lock' on the gauge... and were far from locking. Out of curiosity more than anything, I am going to pick up an 11 piece Forster Gaige set to get an actual measurement. 11k really isn't that much if you shoot a few hundred rounds every other weekend. Meant it was a lot of rounds for most barrels, not that it was a lot to shoot. My take is 1.4736” is max for new mil-spec 5.56mm ammo. Reloaded cases or possibly even some new commercial ammo maybe not so much. |
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What are you calling max value? Which gage passed and which gage failed for a given combination of bolt/barrel? Just curious. 11k is a lot. I was using the Brownells 1.4736" 5.56mm "Colt Headspace Gauge." From what I read, 1.4736" is the maximum permissible value. All combinations failed to 'lock' on the gauge... and were far from locking. Out of curiosity more than anything, I am going to pick up an 11 piece Forster Gaige set to get an actual measurement. 11k really isn't that much if you shoot a few hundred rounds every other weekend. I only use a USGI Field Reject.The Colt Field II from Brownells is a bit larger,but beyond that its all you need to know...pass or fail on the field reject.So I wouldn't worry about exact headspace,muchless spend the kind of money a full set of headspace gages will cost you.Otherwise save your money for more ammo etc. and continue on. The military uses new mil-spec ammo. Trained amorers TI military weapons on a regular basis. The military deadlines weapons that fail the military field gage. Also while the military may take the simplistic approach at the unit level that is not the case when the weapons are built. As someone who builds ARs to ensure headspace is ok I think at least three gages are needed because the range new headspace should fall in is less than the max headspace allowed. I also manage my personal weapons to keep headspace within the SAAMI limits not military limits. |
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What are you calling max value? Which gage passed and which gage failed for a given combination of bolt/barrel? Just curious. 11k is a lot. I was using the Brownells 1.4736" 5.56mm "Colt Headspace Gauge." From what I read, 1.4736" is the maximum permissible value. All combinations failed to 'lock' on the gauge... and were far from locking. Out of curiosity more than anything, I am going to pick up an 11 piece Forster Gaige set to get an actual measurement. 11k really isn't that much if you shoot a few hundred rounds every other weekend. I only use a USGI Field Reject.The Colt Field II from Brownells is a bit larger,but beyond that its all you need to know...pass or fail on the field reject.So I wouldn't worry about exact headspace,muchless spend the kind of money a full set of headspace gages will cost you.Otherwise save your money for more ammo etc. and continue on. The military uses new mil-spec ammo. Trained amorers TI military weapons on a regular basis. The military deadlines weapons that fail the military field gage. Also while the military may take the simplistic approach at the unit level that is not the case when the weapons are built. As someone who builds ARs to ensure headspace is ok I think at least three gages are needed because the range new headspace should fall in is less than the max headspace allowed. I also manage my personal weapons to keep headspace within the SAAMI limits not military limits. Unless I totally misread something Im not tracking on the point being made. But yeah,having a set of headspace gages(GO,NO-GO and FIELD reject) would be a good topic for building "new" rifles from "new" parts which need verification of "new headspace." Was previously discussed here even further most recently: http://www.ar15.com/forums/t_3_4/578194_Does_everyone_check_for_headspace_.html&page=1 But at the moment we are talking about a bolt defect due to wear and replacement of the same in a 5.56 NATO chambered weapon that has 11,000 rounds down the tube.Mostly concerned with inspection of FIELD Reject status as detailed per the -23&P in this situation. Which the OP has already made verification of this status Colt Field II reject. Beyond that,I certainly do not see any reason to buy a 11 piece set of SAAMI spec .223 Rem headspace gages to verify headspace dimensions to the .001" on a 5.56 NATO chamber .Especially a well used barrel in excess of 10,000 rounds service. Thats what I was trying to say. |
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Unless I totally misread something Im not tracking on the point being made. But yeah,having a set of headspace gages(GO,NO-GO and FIELD reject) would be a good topic for building "new" rifles from "new" parts which need verification of "new headspace." Was previously discussed here even further most recently: http://www.ar15.com/forums/t_3_4/578194_Does_everyone_check_for_headspace_.html&page=1 But at the moment we are talking about a bolt defect due to wear and replacement of the same in a 5.56 NATO chambered weapon that has 11,000 rounds down the tube.Mostly concerned with inspection of FIELD Reject status as detailed per the -23&P in this situation. Which the OP has already made verification of this status Colt Field II reject. Beyond that,I certainly do not see any reason to buy a 11 piece set of SAAMI spec .223 Rem headspace gages to verify headspace dimensions to the .001" on a 5.56 NATO chamber .Especially a well used barrel in excess of 10,000 rounds service. Thats what I was trying to say. The whole thing has been previously discussed several times in the last few weeks. One point is the military does not use the variety of ammo that is used by civilians which would include reloads. In other words some of us think that the max military headspace may be too much for some ammo. Another point is that the military field gage is not a solution for someone who wants to keep their weapon in SAAMI specs. Another point is some people like some warning before their weapon fails whichever field gage they are managing their headspace to. FYI SAAMI headspace range is a sub-set of the 5.56mm headspace range and the Forster 11pc match gage set covers both. I can’t speak to the OP’s intentions, but for some reason most people on the board seem to have BRD. |
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