New A1 failure to feed

[schuang]

Update: Even with H2 buffer and carbine chrome silicon spring swap, the feed problem still exists....

While cleaning T91 after shooting, I noticed there is a small gap between barrel feed ramp and receiver on the left side ramp (for my case, the bullet pushes inside of the case always happened on the left side of the feed). It prompts me to noticed that it always happened with HP bullet only -- the front edge of Hollow Point bullet occasionally catches the small gap causes all of my grief. I would think the pointed-nose-type bullet would probably do the similar thing (BTW everglade's Ver4 bullet is not quite pointed so they don't jam)

Furthermore, I did online search and found something interesting. I may just fix it as M4 ramp....

Sean

ar15barrels_feedramps2.jpg

[apex]

It prompts me to noticed that it always happened with HP bullet only -- the front edge of Hollow Point bullet occasionally catches the small gap causes all of my grief

Don't use hollow points or any open-tip projectiles in T91s. This is a common and known issue- they don't play well because of the feed ramps.

[SIMODshooter]

I wonder if the left side feed ramp can be modified? Mine did it only on left side... I bought the dam think for no DI and more reliability based on it being a military upper basically.

See how mine does next week with GI mags only.

I also added some pic rail to the oem handguns and vickers tactical sling. And hosed it down in spay paint camo.

[apex]

Sure it can be modified, if you have a file or a dremel lying around (do not attempt).
In all seriousness though you could always change the barrel extension to one with M4 ramps IF YOU ARE OR KNOW A QUALIFIED GUNSMITH WHO CAN PERFORM THIS INSTALLMENT. I stress this because fiddling with the extension is messing with the headspacing which if incorrect, could cause a kaboom.

Safest option is to not use hollow point/open tip ammo and stick with FMJ or anything else that has a pointy rounded nose.

[e292644]

Anyone having the feeding issues please share some photos like this one please.

ar15barrels_feedramps2.jpg

[SIMODshooter]

I have a local very good gunsmith who does LEO and tactical stuff I may take mine to him and see what he says about the feed ramp issue.

I thought about using one of the tools we use to port and polish heads at my shop.. then decided that was a bad idea

[schuang]

Anyone having the feeding issues please share some photos like this one please.

ar15barrels_feedramps2.jpg

After few weeks of firing test and careful observations, I concluded the root cause of fail-to-feed problem is indeed Wolf A1 uses Rifle ramp instead of M4 ramp.

I got second Wolf A1 upper (14.5in this time) and it also occasionally jams on the left side of the ramp. The problem is always the bullet pushed inside of brass and jammed between receiver wall and bolt carrier. Photo 1 shows copper fouling on T91 chamber after 50 rounds fired with one round failed to chamber. Photo 2 also shown a light mark on the left side of ramp. (the black bumps in the photo are powder because of the failed round)

Thinking how come my regular AR never jammed, so I took a photo of regular AR with M4 ramp cut right after the range time. On Photo 3, It's clear that few bullet tip also left copper fouling marks right on the receiver cut portion of M4 ramp. Since the receiver ramp is cut with M4 profile on a regular AR (Photo 4), the round would slip into the chamber without an issue. If this happened with Wolf A1 rifle ramp, bullet tip would hit the straight part of receiver wall and jammed. This also confirmed that jam is not due to the cycling method (direct impingement vs. piston driven) but rather fundamental feeding problem IMHO. BTW as I experienced, the jam happened regardless of bullet type.

I also observe three different mags (Pmag, Lancer, Hexmag) in the chamber and they do have minor tolerance differences but all have enough opening for a round to cumber properly. Every mag that I have sits a round high enough to clear the feed ramp, but I believe the bolt carrier in certain cycle that hits top portion of the the round bottom so hard that ammo tilted down and the tip of the bullet hitting the receiver portion of the ramp (or wall in case of Wolf A1).

Sean

[apex]

Sorry to see you keep having troubles
Since the same issue is occurring on two different T91 uppers in the same spot, here's another possibility/variable since I didn't see it mentioned: did you use the same lower each time?
Might be that your lower is out of spec/does not like T91's tolerances, several possibilities:
1. the takedown pin holes are drilled too high causing the gap between the upper and lower to be too great
2. the takedown pin holes are drilled at an angle causing your upper to tilt to the right
3. your takedown pins or holes are too loose and causing the upper to wiggle around too much
4. the holes and cutouts for the magazine claw were drilled and milled slightly too low
5. combination of two or more

An easy way to check the upper-lower fitment without taking measurements with calipers: on a "within spec" upper-lower gap it will be possible to slide a piece of copy paper up to an index card through the gap, but cardstock will not go through.

To check the magazine claw will require measuring however: the distance between the bottom of the claw cutout and the top of the lower should measure 0.9375in or 15/16ths in.

ar15-lower-measurements.jpg

Obviously this will vary to some degree depending on the manufacturer and their QC, but generally it should not measure over 0.95in, and if it's 1.0in or above you're in "woah nelly" territory.
Note: this does not necessarily mean your lower is "deflective"- since M4 ramps have become industry standard, how high the magazine sits in the magwell is now a looser tolerance and manufacturers have taken advantage of this

[schuang]

I use the same lower on both Wolf A1s and they mate fairly tight that there is no wiggle between upper and lower. Interestingly, my AR upper/lower is quite loose even though they came complete as a whole rifle but it never jam.
No worry, fix is on the way and the problem will be solved next time I post.

[SIMODshooter]

I ran three 30 rd GI alum. Mags through mine today ran great...and on the 4th mag it started short stroking....

I also put 4lb spring kit and bobbed the hammer with anti rotate pins ran like a champ until 4th magazine... trigger feels amazing now

I attempted to run some wolf HP since I accidentally bought 250 rounds
The HP sticks on left feed ram. Zero issues with the left feed ramp with the 55gr or 62gr ammo on left feed ramp..

I have the standard weight buffer in it now ordering a lighter buffer next week.

Hopefully I can get the dam thing to run without issues I bought a total of four 14.5 uppers