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Posted: 9/14/2016 3:15:32 PM EDT
| Hi all, I've read the sticky by Tweak on short stroking as I'm am in the mist of figuring out my ordeal. I pulled my buffer out and I weighs 2.9 oz. this is on a mid length upper. Firing end ejecting are fine but will not hold back on last round. Should the 3 oz buffer work or do I need something else ? Bolt,gas tube all are smooth and don't see anything loose or out of spec. I did notice the cases were not shiny so I bought a chamber brush and swab/cleaned and polished a the chamber a bit. |
| Everything is new, the only rang that was open only allows fangable rounds but tomarrow I am going to my range with different types of ammo. Upper is a PSA 16 mid that is complete wo BCG or charging handle. I only had a 10 rd Magpul mag at the time but I have a 30 rd and a metal 30rder to try out tomarrow. The lower I bought complete but no nothing about it other than pulling the buffer to weigh it. |
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Try different combinations of mags and ammo and see what happens.
It might just be a new build and the gas block needs to seal itself better. Do you see gas leakage on the barrel around the gas block? It looks like carbon streaks or burn marks. Also, make sure the BCG is lubed very well. Run it wet. You should see oil on it heavy enough that it is visible. Especially when brand new. Put a drop or two inside the bolt cam pin recess and work the bolt back and forth. Lube the bolt lugs and the four rails on the bolt carrier (two upper, two lower). Put a couple drops on the hole for the gas rings (or take the bolt out of the carrier and do this directly). AR-15 Lube Points |
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Two quick checks to try after you have cleaned the chamber with a chamber brush and clp, then correctly CLP lubed the bearing areas.
Pull all the way back on the charging handle, and see where the bolt face stops against the back of the ejection port window. The face of the bolt should stop about 1/8" to 1/4" in front of the back edge of the ejection port window. Also as you are pulling the charging handle back, the amount of tension to pull it the last 2 inches all the way back should not increase in tension. If the tension increases, pull the recoil spring and check it's length. For a telescoping butt stock receiver extension that uses the Carbine lenght buffer, the spring should be about 10.5". If the spring is 11.75", it the wrong spring (for a full lenght fix stock receiver extension instead. If the correct spring and the correct buffer are in play, and you still can't get the bolt face all the way back just short of the ejection window the distances noted above, pull the buffer and spring, and measure the distance of the tube void from the front top lip, to the bottom of the void. On a carbine receiver extension (again, telescoping butt stock) the void depth should be 7". If your coming up with 6 3/4" void depth, then you have an air soft receiver extension in play, and it either needs to be replaced with a real receiver extension for the AR rifles, or you have have to shorten the buffer bumper to get the combo to work isntead. Next, shotgun the upper open and work the bolt catch by hand. The spring tension should be pulling it down, but the movement of the catch should be fluid in the receiver slot with no binding. If the catch is binding in the slot, then some CLP and work the catch until is loosed up. Now the fun one, load a emtpy mag into the mag well with the upper still shotgunned open ,and confirm that the follower will lift the bolt catch up full height (what you can pull the catch up via hand). Now with the catch at full height via the mag follower, push the follower all the way forward in the mag body, and make sure that the catch tab is not slipping off the back side of the follower rear shelf. Hence on some plastic mags, the catch tab is not long enough to work with the mags since the follower can walk forward enough in the body, and this prevent the bolt catch from being activated correctly after the last shot instead. If such is the case, and you plan on using these mag, then you may have to modify a 9mm catch for the rifle so the catch tab is long enough to not miss the back of the follower rear shelf with the follower all the way forward in the mag body. http://www.ar15.com/forums/t_3_66/479984_Problem_bolt_catch__help_____Fixed_01_29_2010________.html If the it's not a catch tab problem, but the fact that the good working mag follower will not lift the bolt catch all the way up, then bank that either the wrong spring is in play for the bolt catch, or crap in the bottom of the spring channel causing too much tension (blasting media that was not cleaned out of the channel), or the spring channel itself not deep enough, with such causing too much tension on the mag catch return tension, and the mag follower tension not strong enough to over come such tension instead. 
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| Everything seemed to check out. I took the BCG apart and cleaned it then oiled it completely "wet". I did oil it lightly when putting it together but maybe not enough ? The brass coming out was clean "no scratches" I think polishing the chamber a little helped too. Fired Perfecta,BMC,Fusion and independence with no problems and very pleased with the accuracy. Thank you gents for helping getting everything squared away. |
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