Did you load one round of your reloads to see if it locked the bolt back?
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Another fail to feed question
So I am having a failure to feed issue with my new PSA 6.8 upper on a colt lower. I first loaded up some 95 grain TTSX with 29 grains of AA2200 at 2.295 just like everyone else and planned to work up to 30 grains. I am using a brand new PRI 15 round 6.8 magazine. The feed ramps on the upper don't look too bad. I thought I should be doing okay as far as function. So I loaded up the magazine with my 95 grain loads and hit the range. While three rounds in I got a click. I rack the bolt and keep going. two or three rounds later same thing, just a click. The bolt doesn't seem to be picking up the round. So I decided to run some tests to identify the problem. I stopped by the store today and got a box of Federal Fusion 90 grain and took some more 96 grain TTXS loads ( this time shortened to 2.270 to see if that helped) to the range again. The TTSX loads acted the same, two fail to feed malfuntions in 15 rounds. Then I loaded one round of the fusion to check for a short stroke issue and the bolt locked back as it should. I then loaded 15 rounds in the magazine and fired them in a string, no malfunction. So the confusion to me is why would I just get random fail to feed malfunctions with the TTSX? Also my loads were using new SSA brass. I am hoping somebody can give advice.
Thanks
Bob
Thanks
Bob
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If I understand you correctly, the result was that the weapon cycled but did not pick up a round. The most frequent cause for this, I think, is a short stroke which can be caused by a few different issues such as underpower ammo, problem with gas system, or just excess friction on the action caused be either a very dirty weapon or one that just hasn't been broken in yet (so run it wet!). Another cause could be the bolt rides over the round due to a problem with the magazine or, rarely, a problem with the lower receiver or mag catch being out of spec and holding the magazine a bit too low. This should be pretty low probability with a Colt lower, though. If the feed ramps where you an issue, you'd get a strait out stoppage and have to clear out a jam.
I didn't, but I would not have thought my load would have less gas than the factory loads. My loads are pretty stiff and with heavier bullets. But that does make sense. I will check that.
I did completely clean the gun today today and assured the gas rings were not aligned. I was running it pretty wet and I have been using the Colt lower with the colt upper for a little while and have had no issues with it. Also with the factory ammo not malfunctioning, my only guess is it has to be something with my loads, but how could a heavier bullet loaded near max pressure short stroke when a factory load functions fine?
Fail to feed
I put two 6.8 SPC ARs together using AR Performance barrels. One has their 16" 6.8 5R Socom profile barrel which has a mid length gas system. The other one has their 20" 6.8 5R midweight barrel which has a rifle length gas system. The 16" one functions just fine but he 20" one fails to feed. Except for the barrels, rails and gas tubes, the rifles are identical. Both are using Geissele SS gas blocks. Both rifles have AR Performance Bolts and carriers and standard AR carbine buffers and springs. The ammo I was using was Hornady 110gr BTHP. Any suggestions on how to solve this problem or what to check first.
Both guns are brand new. For the very first round, I loaded a single round in the magazine. When that went well, I loaded two rounds in the magazine. The bolt cycled, ejecting the fired case but did not pick up the next round. Tried again with two rounds and same thing.
I put two 6.8 SPC ARs together using AR Performance barrels. One has their 16" 6.8 5R Socom profile barrel which has a mid length gas system. The other one has their 20" 6.8 5R midweight barrel which has a rifle length gas system. The 16" one functions just fine but he 20" one fails to feed. Except for the barrels, rails and gas tubes, the rifles are identical. Both are using Geissele SS gas blocks. Both rifles have AR Performance Bolts and carriers and standard AR carbine buffers and springs. The ammo I was using was Hornady 110gr BTHP. Any suggestions on how to solve this problem or what to check first.
Both guns are brand new. For the very first round, I loaded a single round in the magazine. When that went well, I loaded two rounds in the magazine. The bolt cycled, ejecting the fired case but did not pick up the next round. Tried again with two rounds and same thing.
IF your rounds are over gassed (might need an adjustable gas block)--- what can happen is that the brass "sticks" in the chamber for just a bit more time than factory loads, thus when the BCG tries to extract the MT shell casing it has a hard time trying to eject the brass and it slows the carrier down (as it is sticking in the chamber still) and it can show symptoms of being under-gassed.
if this happens, you will often see "cloudy" brass as it is trying to extract the brass while it is still expanded in the chamber (also known as "scuffed brass")
Best way to fix an over gas problem is to add an adjustable gas block and turn down the gas, easiest way to diagnose an over gas problem is if you have an extra spare heavy buffer to try and see if it helps-- other ways are also adjustable gas keys, and adjustable carriers
for a side note here is a thread on mag lip and spring tweaking that you could read up also : http://68forums.com/forums/showthread.php?61145-Mag-Lip-Adjustments
and general tips : http://68forums.com/forums/showthread.php?57071-Hints-Tips-and-general-information
if this happens, you will often see "cloudy" brass as it is trying to extract the brass while it is still expanded in the chamber (also known as "scuffed brass")
Best way to fix an over gas problem is to add an adjustable gas block and turn down the gas, easiest way to diagnose an over gas problem is if you have an extra spare heavy buffer to try and see if it helps-- other ways are also adjustable gas keys, and adjustable carriers
for a side note here is a thread on mag lip and spring tweaking that you could read up also : http://68forums.com/forums/showthread.php?61145-Mag-Lip-Adjustments
and general tips : http://68forums.com/forums/showthread.php?57071-Hints-Tips-and-general-information
http://68forums.com/forums/showthread.php?55097-SHORT-STROKING-PROBLEMS-build-tipsI put two 6.8 SPC ARs together using AR Performance barrels. One has their 16" 6.8 5R Socom profile barrel which has a mid length gas system. The other one has their 20" 6.8 5R midweight barrel which has a rifle length gas system. The 16" one functions just fine but he 20" one fails to feed. Except for the barrels, rails and gas tubes, the rifles are identical. Both are using Geissele SS gas blocks. Both rifles have AR Performance Bolts and carriers and standard AR carbine buffers and springs. The ammo I was using was Hornady 110gr BTHP. Any suggestions on how to solve this problem or what to check first.
Both guns are brand new. For the very first round, I loaded a single round in the magazine. When that went well, I loaded two rounds in the magazine. The bolt cycled, ejecting the fired case but did not pick up the next round. Tried again with two rounds and same thing.
Other tips to everyone when describing problems.
failure to extract- failure to remove case from chamber
failure to eject- failure to toss case out of receiver
Failure to feed- will not strip a round from the mag and put it in the chamber
failure to lock back...short stroke - the bolt and carrier does not travel rearward enough to engage the bolt catch
How much gas is being developed? 2200 powder usually makes plenty of gas provided it gets a good hot spark to start it off. Are you using mag primers? Another thing is using new brass. Fireforming is going to eat up some of the energy and may contribute to short stroking. Try loading the same load using once fired cases to see if there's any difference.I did completely clean the gun today today and assured the gas rings were not aligned. I was running it pretty wet and I have been using the Colt lower with the colt upper for a little while and have had no issues with it. Also with the factory ammo not malfunctioning, my only guess is it has to be something with my loads, but how could a heavier bullet loaded near max pressure short stroke when a factory load functions fine?
Another type of short-stroke to look for: the carrier "locks back" (on the mag I think) but the bolt is still extended forward. Need to look carefully (I used single shots to isolate this symptom) to see before you cycle the charging handle.
Other suggestions I followed on breaking in a new barrel.
1. Polish the inside of the chamber, sometimes it is still a touch rough. Contributes to friction and brass scuffing. This "polishing" also basically takes place as you cycle your first 50-100-x (pick your favorite number...) rounds
2. Swap out and use a known-good carrier, some newer ones could be rough enough to contribute excess friction.
3. ARPs are typically drilled for carbine buffers and springs, are you using a rifle length on either?
Rifter's note on the primer is an easy one to miss. 2200 needs the mag primer (like cci 450 or etc) for best result.
Other suggestions I followed on breaking in a new barrel.
1. Polish the inside of the chamber, sometimes it is still a touch rough. Contributes to friction and brass scuffing. This "polishing" also basically takes place as you cycle your first 50-100-x (pick your favorite number...) rounds
2. Swap out and use a known-good carrier, some newer ones could be rough enough to contribute excess friction.
3. ARPs are typically drilled for carbine buffers and springs, are you using a rifle length on either?
Rifter's note on the primer is an easy one to miss. 2200 needs the mag primer (like cci 450 or etc) for best result.
Hand work the action a couple hundred times, clean BCG and locking lug area, relube and hand cycle a couple hundred times again. Clean, relube, and test fire again.I put two 6.8 SPC ARs together using AR Performance barrels. One has their 16" 6.8 5R Socom profile barrel which has a mid length gas system. The other one has their 20" 6.8 5R midweight barrel which has a rifle length gas system. The 16" one functions just fine but he 20" one fails to feed. Except for the barrels, rails and gas tubes, the rifles are identical. Both are using Geissele SS gas blocks. Both rifles have AR Performance Bolts and carriers and standard AR carbine buffers and springs. The ammo I was using was Hornady 110gr BTHP. Any suggestions on how to solve this problem or what to check first.
Both guns are brand new. For the very first round, I loaded a single round in the magazine. When that went well, I loaded two rounds in the magazine. The bolt cycled, ejecting the fired case but did not pick up the next round. Tried again with two rounds and same thing.
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