M14 Forum

Whatsinaname181

Ok, someone please enlighten me before i use this damn thing as a boat anchor or wrap it around a tree-

Im having feeding problems with an ar15. N4 noveske lower, krieger barrel.

rounds are getting caught on the feed ramp and getting pushed back into their casings. the thing is, it doesent do it all the time, only when it feels like it and usually it will start doing this for a while, then stop. I just had 7 rounds in a row get misfed.

i keep the rifle clean and use good magazines.


K.

YardDogOne

who built the rifle?

does it have the M4 feedramps on the Reciever AND Barrel?

need more info

pictures?

Whatsinaname181

Looks like its hanging up on the feed ramps. the right one more than the left, I think. yes, i believe they are M4 feed ramps.

My friend and I built the rifle. Hes built several and they all run well.

there seems to be a lip between the barrel extention and the lower... never noticed this before. All my open tip rounds that got pushed back into the case have a horizontal line across the top. it must be catching on this lip. what should I do?

Attached Images

100_1121.jpg (24.5 KB, 54 views)

2336USMC

The picture isn't perfectly clear, but it looks like you have a barrel extnsion with rifle feedramps installed on a lower with M4 feedramps. This means there is a gap on each side where the M4 feedramps are cut into the lower rec but the feedramps on the rifle extension don't match up where bullt points can hang up.

The underlying issue though, is that the bullet points should not be nosediving that low during feeding. This can be caused by weak magazine springs and by high cyclic rate, i.e. BCG is moving too fast and slams the round out of the mag so fast that the bullet does a nosedive and hits the feed ramps low. What type of buttstock are you running, what type and weight of buffer, what type of bolt carrier?

This type of problem is least likely to happen with a full weight rifle buffer and full weight USGI type bolt carrier (heavy total weight slows down the BCG, and it operates more like a bulldozer than a racecar), most likely to happen with a light carbine buffer and a cutaway lightweight semi-auto bolt carrier (light total weight makes the BCG cycle very fast.)

If you are running a carbine stock and buffer there are heavier buffers that will slow down the action, such as the H2 and H3 types developed for carbines to slow the action/cyclic rate and prevent this very problem.

Whatsinaname181

Sorry, I tried to get it as clear as possible. I am running an A2 type buttstock with a standard size recoil buffer. My BCG is a Rock River Arms semi auto BCG. It may be "USGI", i am not sure though.

I looked at my bushmaster that has never given me problems in 12,000 rounds, and it appears that it too has a bit of a lip where the feed ramp meets the barrel extention.

Mabye youre right about the buffer? If not, would i need to have work done on my feed ramps to correct this problem?

angelonm

M4 feed ramps
on barrel on receiver = good
on barrel not on receiver = ok
not on barrel on receiver = bad
not on barrel not on reciever = good for rifle = ok for carbine

Its not clear but it looks like you have M4 ramps on the upper receiver but not on that bbl extension. If that is the case rounds will catch.
You will need to change upper or open up the feed ramps on bbl. I recall seeing a how to on another forum. I will try and find it.

http://youtu.be/jMe0_HgkYEQ

2336USMC

Hmm...

Well, here's a link to a post on another forum that has some very good pics showing the most common 4 types of AR bolt carriers, from heaviest (USGI) to lightest (full cutaway semi auto). Which type do you have?

http://www.ten-41.com/showthread.php?t=502

Even if your rifle feedramps don't match up perfectly to the M4 ramps in the lower, the rifle should still feed fine with a rifle buffer... billions of rounds have been fired with rifle buffers and feedramps. Colt has been selling ARs with standard rifle feedramps and cutaway (slightly lighter) bolt carriers for decades and they feed just fine.

Just a bit of history. it was discovered very early in the development of the AR/M16 that the original buffer was too light. The early rifles had a cyclic rate of something like 1200 rpm, and had feeding problems. By the time the rifle was accepted as the M16A1 it had a much heavier buffer that slowed the cyclic rate to more like 650-750 rpm and the feeding problems went away.

There could be several things going on that make your rifle just go over the edge to not feeding well. Is the buffer known to be USGI design, weight, and construction? Is the recoil spring known to be USGI design and stiffness? What about the ammo you are using, USGI pressures at the gas port?

A well set up AR (well set up means very close to USGI spec) should have a wide tolerance for ammo and should feed anything from 40 gr to 80 gr 100%.

it might just be the mismatch on the feedramps. Cutting rifle feedramps to M4 design (deeper and steeper to match the lower) is a standard procedure from any good AR smith, should be pretty cheap, and won't affect your nice Krieger barrel in any way. You could even do it yourself with a Dremel tool, but I don't recommend that. A good AR smith will have a standard setup on his milling machine to make the cuts properly.

But I still suspect there is something else going on, something is not milspec... maybe a combination of little things, lighter semi-auto BC, recoil spring a bit stiffer than USGI, buffer a little lighter... this is the kind of thing you run into using aftermarket parts sometimes.

2336USMC

For reference, after shooting and cleaning about a gazzillion ARs and USGI M16s, the copper rub marks left on the feedramps of rifles are typically mostly about halfway up the ramps, with a few bullets hitting the ramp about 1/3 of the way up.

Your rifle should not be pushing bullets down into the lower receiver or into M4 feedramp territory unless something is out of spec...

82nd ABN

I know what the problem is. I had the same exact thing with a Krieger varmatch barrel. It's the barrel extention bolt lugs. Mine were sharp and too narrow and it would cause two lines to form on either side of the bullet. If you are getting the same lines that's your problem. I could have fixed it but Krieger insisted I send it back. They wound up polishing the edges of the extention lugs. The turn time was quick. My extention is an M4 extensions as well. You can look on your order confirmation, it should say M4 extention, they charge an additional $18 for them.
I'm basing this on your desription of the lines on the bullets.

Sorry retracked everything above. Misread what you said.

angelonm

True. ramps are mostly a guide. Bullet should almost be leaping in to the chamber.

82nd ABN

Ps it will tell you what extention got installed on your order confirmation.

82nd ABN

This picture might help you determine what you have and what is good to go.

ArmyCPT

OP, if you already haven't done this, go out and buy a PMAG, and see if that helps in rectifying the problem.

Yeah - of all things.

Whatsinaname181

82nd, my looks like the top right, but with a lip showing in the middle. and my invoice doesent say, it just tells me the make and that its an HBAR.

USMC, my bolt carrier group looks like the 2nd one from the top, like a regular FA bolt carrier, but milled 1/4 inch back. i have a few PMAGs laying around that ill try.

it has done this with USGI 30 rounders, with issue 20 round colt magazines and today with the new USGI magazines with the non-tilt followers.

im hoping i dont have to get this thing worked on... the issues are sporadic. it doesent do this all the time. i thought it had something to do with the 20 round magazines, so i started loading 18, then 15. seemed to help, but then it started acting this way again. sometimes it will go 200 rounds without doing this.

Oh yeah, and im shooting 75gr PPU .223 ammo. its good stuff.

its also done this with black hills 69gr and MK262 77gr i think too.

dcobra823

My advice is to learn how to build a rifle the right way!