Randall
04-07-12, 08:47
Background:
The rifle is a Daniel Defense M4, carbine length, standard H buffer, with 304 rounds through it after all of these tests
Range Day 1:
Ran 50 rounds of Remington UMC yellow box 55FMJ through the brand new gun without a hiccup.
Range Day 2:
Fire 50 rounds w/ no problems. 101st round through the gun is a bolt over base malfunction with the live round angled up the feedramp and the BCG wedged up against the angled round. Cleared the malfunction and continued with the same mag. 9 rounds later after the last round is fired the bolt doesn’t lock to the rear on an empty mag.
My guess is short stroking so I naturally want to figure out why.
I take it back to the house and give it a thorough cleaning and lubing, inspect the front sight base for gas leaks, carrier key for tightness, gas tube, measure buffer spring (11 1/8) etc. I take out the charging handle and set the upper upright with the muzzle on the ground. I slide the BCG into the upper as slowly as I can. When the carrier key touches the gas tube there is a little binding, enough to where the carrier key will barely sit on the gas tube without going forward. Now this only happens when I very gently ease the BCG forward with the upper off of the lower. When the rifle’s fully assembled I can feel the grittiness of the key and gas tube rubbing when I pull the charging handle but its not ever enough for it to prevent it from going into battery.
At this point I don’t know if the carrier key/gas tube binding is the reason but experience tells me to test the cheap fixes first in case it is an ammo related problem before tearing shit apart
Range Day 3:
I go to the range and use Remington UMC yellow box 55FMJ again and do single round in the magazine lock back tests to see if I can replicate the problem. I do 40 of these lock back tests (with five different mags) and the rifle fails to lock to the rear 2 times. The brass also fails to clear the ejection port 3 times (the brass wasn’t still chambered but sitting on top of the empty mag facing the correct direction (primer to the rear and case mouth to the front).
After this I guess that it’s the ammo and if I shoot some 5.56 instead of 223 then it might fix it.
Range Day 4:
I switch ammo to IMI M193 55FMJ and do 56 single round lock back tests (with 7 different mags). There are no failures to lock to the rear on an empty mag but I do have 19 instances where the brass doesn’t clear the ejection port in the same manner as before. (This happened with each of the mags at least twice so it isn’t a mag issue). At this point I wonder if this is a common thing with the last round in a mag (though I doubt it) and load up a full thirty rounder.
Round 1 of the full mag is fine and ejects normally
Round 2 is fired but the brass doesn’t clear the ejection port and the BCG jams against it and a live round attempting to go in the chamber.
I clear it and continue on. No more hiccups in that 30 rounder or the two more 30 rounders after that. (88 rounds)
After this I have four leftover rounds sitting out so I put them in different mags to do single round lock back tests again for the hell of it. The first and second brass don’t clear the ejection port same as before. Third and forth eject normally
So what gives? Is it common for the last round to not clear the ejection port either during lock back tests or normally? I wouldn’t be too too worried about it since they always drop free when the mag is dropped but then it happened once with a full mag too…
My guess is the UMC was a little underpowered and thus the reason for the short stroking, which is why the IMI doesn’t have a problem locking to the rear, but then why is the brass not ejecting? Ejector problems? How do I test/remedy this problem?
Any help would be greatly appreciated and thanks in advance.
-Randall
The rifle is a Daniel Defense M4, carbine length, standard H buffer, with 304 rounds through it after all of these tests
Range Day 1:
Ran 50 rounds of Remington UMC yellow box 55FMJ through the brand new gun without a hiccup.
Range Day 2:
Fire 50 rounds w/ no problems. 101st round through the gun is a bolt over base malfunction with the live round angled up the feedramp and the BCG wedged up against the angled round. Cleared the malfunction and continued with the same mag. 9 rounds later after the last round is fired the bolt doesn’t lock to the rear on an empty mag.
My guess is short stroking so I naturally want to figure out why.
I take it back to the house and give it a thorough cleaning and lubing, inspect the front sight base for gas leaks, carrier key for tightness, gas tube, measure buffer spring (11 1/8) etc. I take out the charging handle and set the upper upright with the muzzle on the ground. I slide the BCG into the upper as slowly as I can. When the carrier key touches the gas tube there is a little binding, enough to where the carrier key will barely sit on the gas tube without going forward. Now this only happens when I very gently ease the BCG forward with the upper off of the lower. When the rifle’s fully assembled I can feel the grittiness of the key and gas tube rubbing when I pull the charging handle but its not ever enough for it to prevent it from going into battery.
At this point I don’t know if the carrier key/gas tube binding is the reason but experience tells me to test the cheap fixes first in case it is an ammo related problem before tearing shit apart
Range Day 3:
I go to the range and use Remington UMC yellow box 55FMJ again and do single round in the magazine lock back tests to see if I can replicate the problem. I do 40 of these lock back tests (with five different mags) and the rifle fails to lock to the rear 2 times. The brass also fails to clear the ejection port 3 times (the brass wasn’t still chambered but sitting on top of the empty mag facing the correct direction (primer to the rear and case mouth to the front).
After this I guess that it’s the ammo and if I shoot some 5.56 instead of 223 then it might fix it.
Range Day 4:
I switch ammo to IMI M193 55FMJ and do 56 single round lock back tests (with 7 different mags). There are no failures to lock to the rear on an empty mag but I do have 19 instances where the brass doesn’t clear the ejection port in the same manner as before. (This happened with each of the mags at least twice so it isn’t a mag issue). At this point I wonder if this is a common thing with the last round in a mag (though I doubt it) and load up a full thirty rounder.
Round 1 of the full mag is fine and ejects normally
Round 2 is fired but the brass doesn’t clear the ejection port and the BCG jams against it and a live round attempting to go in the chamber.
I clear it and continue on. No more hiccups in that 30 rounder or the two more 30 rounders after that. (88 rounds)
After this I have four leftover rounds sitting out so I put them in different mags to do single round lock back tests again for the hell of it. The first and second brass don’t clear the ejection port same as before. Third and forth eject normally
So what gives? Is it common for the last round to not clear the ejection port either during lock back tests or normally? I wouldn’t be too too worried about it since they always drop free when the mag is dropped but then it happened once with a full mag too…
My guess is the UMC was a little underpowered and thus the reason for the short stroking, which is why the IMI doesn’t have a problem locking to the rear, but then why is the brass not ejecting? Ejector problems? How do I test/remedy this problem?
Any help would be greatly appreciated and thanks in advance.
-Randall