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Posted: 8/22/2009 4:45:09 AM EDT
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I have just built an upper from a DPMS KTA2-ll. Used a Foster GO gauge to check headspace & the bolt does not fully close. Tried the gauge on my Colt sporter A2 & bolt does fully close.
However, I have read some places that I should remove the ejector to properly use the gauge. Can someone please definitely tell me about the Foster gauge & removal of the ejector? Second, I have tried to chamber 4 different rounds with poor success –– only 1 would chanber & it got stuck such that I had to remove the upper from the lower, put the upper in a vise block to finally get the round out. Bottom line ––- anyone have thoughts about what is wrong ??????? Any help will be much appreciated. |
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To accurately check headspace, you have to know what your chamber was reamed for to begin with. Headpacing is measured from the back of the cartridge case to the datum point in the chamber cone. There is a difference between NATO and civilian, Forster and Clymer and sub variations (Wylde, Noveske, etc.) amongst those groups for the reamers used to cut the chambers. I would start by asking DPMS what type of chamber they use on that particular barrel and what the appropriate headspace gauge is used for their chamber. Only then will you be able to obtain the proper gauges and know for certainty that your gauges are giving you correct info. There is no one-size-fit-all gauge. From Brownells on proper use of the Colt 5.56 Field Gauge: http://www.brownells.com/userdocs/learn/Inst-300%20Colt%20HS%20Gauge.pdf Proper use of this gauge is absolutely critical. Improper use can lead to inaccurate measurements, causing an unsafe rifle to be fixed, with great potential for injury to the shooter. Follow the manufacturer’s recommended procedure and remove the Bolt Carrier Assembly from the Upper Receiver. Strip the Bolt after removing it from the Bolt Carrier. By removing the Extractor and Ejector, you prevent the possibility of a false reading, caused by pressure or tension from these components on the Headspace Gauge. In addition, the amount of force required to cam the Bolt into the locked position is greatly diminished. This is especially important in situations where the Bolt will barely close on a headspace gauge. If the Extractor and Ejector are present, they can prevent the bolt from closing on the headspace gauge. After the Bolt is properly stripped, the Bolt face should be cleaned to remove any dirt, carbon or foreign material that can cause a false reading. The chamber should also be inspected and thoroughly cleaned. Finally, the Headspace Gauge itself should be checked and any oil or grease removed. Reinstall the Bolt Carrier with the stripped Bolt in place and position the Bolt far enough to the rear to allow the insertion of the Headspace Gauge into the chamber. Place the Headspace Gauge in the chamber, then GENTLY, CAREFULLY, move the Bolt Assembly forward. DO NOT SLAM THE BOLT CARRIER FORWARD! EXCESSIVE FORCE WILL RUIN THE HEADSPACE GAUGE AND MAY DAMAGE THE CHAMBER! Use only your thumb and forefinger to move the Bolt Assembly forward. If headspace is excessive, the Bolt WILL cam into position and the Bolt Carrier will move forward so that its rear is flush with the rear of the Upper Receiver. If the bolt DOES NOT cam into the locked position, the rifle does not have excessive headspace. Remember, the Bolt should NOT close on a field gauge. |
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The ejector and extractor does have to be removed to properly check headspace.
Using the field gauge the bolt should not cam into place, if it does that indicates excessive head space. if the bolt does not cam into place and the rear of the carrier extends past the end of the receiver then head space is ok. |
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Thanks for gauge info. I will talk to DPMS about the barrel & gauge.
Here is the other info requested: The DPMS barrel has nothing stamped on it as to calibre. I even took the hand guards off to be sure. Must be .223 Remington. The Colt barrel is 5.56 HBAR The Foster GO gauge is labeled 223 Remington 1.4636" DPMS barrel - DPMS bolt carrier group bolt will not lock on gauge DPMS barrel - Colt bolt carrier group bolt will not lock on gauge Colt barrel - Colt bolt carrier group bolt does lock on gauge Colt barrel - DPMS bolt carrier group bolt does lock on gauge NOTE: I did the above before reading the post about stripping the bolt. However, I had NOT slammed or pushed hard on the bolt. Using the Colt barrel, both bolts lock with 'gentle' force. My conclusion: The DPMS barrel is defective. However, I would like to hear others views based on the above info. Of course I will talk to DPMS. Thanks |
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I agree, it's something to do with the DPMS Barrel. Both bolts close on the GO-GA in the Colt. Now you can strip the bolt if you want but I doubt there will be a change in status for the DPMS.
Excerpt from link: DPMS marks their barrels ".223", though they actually have 5.56 chambers. Read entry #7, about half way down the page...... http://www.co-ar15.com/forums/showthread.php?t=12741 Good Luck, Spec |
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I talked to DPMS about the problem –– did not get into the discussion of .223 vs 5.56 chambering because:
DPMS simply said they would send me a new barrel/bolt carrier assembly & I could return what I now have. Great! No hassle, no fuss. What more could I ask for. I know some might say it should not have happened in the first place and of course that would have been ideal. However, when anyone is willing to do the 'right thing' that is all I ask. |
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