Step 1,

Single loaded round in the mag, insert the mag, charge the round and fire the single round with the empty Mag still in the mag well.

Did the bolt lock back on the bolt catch (bolt catch in front of the bolt, and not just under the carrier isntead).

If the bolt is locking back, then the stroke is fine/ heavy buffer is fine and we don't have to worry about that.
If the bolt does not lock back, then chances are the buffer it too heavy instead (and not don't start clipping recoil spring coils, since they will just end up with feeding problems).

So with the above fine (bolt locks back on the single fired round test), lets move on to why the bolt is not fully locking up on the second round to allow a cleaner primer strike to the primer to set off the round.


1. Is the mag catch assembly threaded tip flush with the face of the mag release button.
2. Are you using USGI mags, or some clone knock offs that may be causing with feed problem.
3. Do your barrel extension feed ramps match the upper.


4. Is your FCG springs installed correctly, especially the hammer spring.

[/img]http://oi43.tinypic.com/2hd1kqb.jpg[/img]

5. Look at the front of the lower receiver cavity just in front of the hammer, and make sure that the J spring in the  bottom of the hammer is not falling out and binding up on the front wall to slow the hammer down.

6. Remove the Bolt from the carrier and dry fit the bolt with carrier into the upper receiver.  Is the key too wide and binging up on the upper receiver slot. when the carrier gets about a inch from touching the face of the barrel extension, the gas tube should enter cleanly into the carrier key (tube does not need to be index tweaked).  Hence you should be able to stick your finger in the back of the carrier, and with little tension, it should glide all the way back, and forth with ease.  If you have any binding, then pull the charging handle to try it without it as well to weed out problem with the charging handle alone.

7. With the upper receiver still shotgun open, take a look at the index of the barrel extension in the upper receiver barrel socket. Use the center of the gas tube channel and the center of the front take down lug to make sure that the barrel extension did not rotate when the barrel nut was being tightened, and now the lugs are not indexed correctly in the upper.

8. Back the bolt, remove the extractor.   If you find a O ring or D fender about the extractor spring, remove it and put it aside.   Hence if all the above checks out, it could be that the extractor tension is too strong, and not allowing the extractor to open cleanly to snap over the case rim at loading; and what is preventing the bolt from locking up fully instead.

9.Rifle cleaned, lubed and back together, pull all the way back on the charging handle and confirm that the face of the bolt stops about 1/8" to 1/4" in front of the back edge of the ejection ports.

As for basic, make sure to correctly clean the rifle to start with  (including using a Chamber brush with CLP by hand to clean the chamber before the gun is every fired, then to correctly lube the upper receiver bearing areas with CLP before the gun is fired as well.

Lastly, if you are running reloads, get a ammo check gauge to run the ammo through to make sure that the cases not only first size correctly to start with, but to run the ammo through after it has been fully loaded to make sure that you did not over bullet crimp to slightly buckle the shoulders on the cases.

To add, you have a ton of needed information missing from your post, such as what brand and type rifle, if a factory build or you built it, and if it has any after market parts.  If you can clue me in on this, than may be something else specific to your rifle that I may need to add to the list to check out as well.

Could use a side view of the height of the bolt catch, but does not look like the catch is being raised up high enough/ all the way up via the empty mag follower.
Is the catch binding in the lower receiver slot, and did you check the catch spring channel when installing the catch to make sure that there was no debris in it before installing the catch, and sure that you have the correct spring install for the bolt catch.



A closer photo of the barrel feed ramps would be better, but right now it looks like the upper receiver ramps are not mating with the barrel extension ramps, and the barrel extension/barrel looks to be rotated in the upper receiver/against the feed ramps.

Break the bolt down to a cleaning level (extractor and FP removed) and double check on if there is a O ring in play.

If the bolt is not fully locking up to start with, with the hammer coming down to drive the FP stop collar into the back of the carrier (back of bolt tail still blocked by the back of the carrier), and the force will just drive the carrier forward to finish locking it up, but not enough rapid impact of the FP to the primer to set the round off).

Look at the B/C, and understand that until the bolt is cam'd over in the barrel extension/ all the way back in the carrier, the FP can not protrude out of the bolt face.

So again, the reason that the round will not ignite, is the bolt is not fully locked up (front face of the carrier tight against the back face of the barrel extension).

So problem could be that the extractor spring is too strong and not allowing it to climb over the round rim at load to begin to slow the bolt and not allowing it to fully lock up, or could be the tips of the rounds slamming the barrel extension feed ramps protruding edges, and slowing the load down that way so the bolt does not fully lock up instead.

Hence once you fire the first round, and look inside the ejection port window before trying to fire the second round, will notice that there is a gap between the front of the barrel extension and the face of the barrel extension.  When you pull the trigger again, the hammer comes down to drive the carrier forward/locks the bolt up, but since the power of the hammer was lost driving the bolt forward, not enough force of the FP alone into the primer cleanly to ignite it instead.

Can you provide any info on the barrel like length, carbine or mid-length gas, chrome lined or nitride finished, hammer forged or not, etc?

CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123