PDA

View Full Version : Technical: receiver feed ramp- unibrow vs widow's peak


W.E.G.
January 11, 2003, 22:26
Here is a pic of the unibrow by Century.

This is an incorrect design.

It lacks the two scalloped ramps that feed the cartidges from the two respective sides of the magazine into the chamber.

I call it a "unibrow" because the area where the feed ramps are supposed to be is just a single "brow." The two red circles show where the scallops should be. There should be a "peak" between the scallops. The unibrow has no peak.

Some folks have rifles with this receiver that actually function. Others have complained that the design is a P.O.S.

W.E.G.
January 11, 2003, 22:34
Here is a pic of the correct design. (This is a FAC "Dan Coonan" receiver.)

Note the "widow's peak" between the two distinct feed ramps.

W.E.G.
January 11, 2003, 22:49
Sandra Bullock has a widow's peak too.

Here's a pic of her looking dreamy in the 1995 movie "The Net."

qwezxc12
January 12, 2003, 12:28
I too, have done a few comparisons...If I may, here are my observations on the subject.

ce
January 13, 2003, 09:51
rrotz, rrotz, look out fer that Vampire!

justashooter
January 13, 2003, 19:45
you guys are sick!

slikrickabn
January 17, 2003, 14:51
Seriously...

My Century L1A1 has the single feed ramp, and when I first fired the rifle, I found that the only malfunction with it was with some mags, the first round would fail to feed, hanging up on the feed ramp. I then polished the feed ramp and opened it up a little, and so far this has fixed the fail to feed problem. Maybe I'm just lucky???

Rick

Court in Fl
January 17, 2003, 22:14
The ramp on that Century receiver looks like a 1911.
I bet it would be good for one of those .45ACP FAL's.

Court in Fl.

Shrike
January 18, 2003, 01:19
Check out what I found in my century...
http://www.lasvegasmercury.com/2001/MERC-Nov-30-Fri-2001/photos/unibrow.jpg


Unfortunately, I didnt find this
http://www.hauntshop.com/images/products/zoom/24644-01zoom.jpg

surplusman2
January 28, 2003, 00:44
having sold about 30 of the century arms "unibrows" as an ffl dealer, i have had mostly good luck until the last batch.
somehow the 'unibrow' allows the nose of the bullet to lodge above the ramp, yet below the bottom of the barrel.
out of 29, i've had 3 with FTF. not bad unless you figure thats 10% in a potential battle rifle. i noticed the 'widows peak' on my aussie. parts gun, looks like a much better idea.

EMDII
January 28, 2003, 14:19
The lack of the central 'peak' or scallop keeps the buullet low during the feed stroke. Ergo, the tip strikes too low. The central peak makes the bullet ride up just a bit sooner, clearing the breech face of the barrel. Tricky dimension here. The FAL has 130 such critical dimensions.

Timing is everything.

Brizz
January 28, 2003, 20:50
I'll have to look at mine (Century R1A1). I'm not sure which one I have, but it works great. I've never had a failure with the inch mags, over 1000 rds. It doesn't work with the metric 5rd mag I got for hunting though.

BTW- Anyone know where to get 5rd inch mags?

Brizz

sobrbiker883
January 30, 2003, 21:35
Gary-it looks like you took a picture of my Century right before I heard about the Dremel grant to WECSOG.:) The brass colored areas are now gone and I even had to shave a tad off of receiver under barrel for right side last rounds to feed consistently.

Marty Morrill
February 04, 2003, 21:35
I 2 have a century with a uni-brow and it wouldnt fire the miliytary surplus FMJ's, only the expencive soft points but then i took out the dremel and re-worked the feed ramps and now it works fine. But im no gunsmith lol.

Speedfish
February 17, 2003, 19:47
Could someone post pics of their receiver after dremeling? I am thinking of getting a CAI L1A1 myself.

Thanks,
Speedfish

MikeyB
December 31, 2005, 14:33
I tried the dremel and polished the feed ramp on my unibrow Century POS. Still had issues with the bullet tip jamming between the receiver and barrel breech face. Ended up bending the magazine lips towards the front of the mag down to help guide the tip of the bullet towards the center of the breech face.
Wish there was a better way of doing this.

MikeyB

drakejake
December 31, 2005, 15:14
MikeyB,

You might try smoothing or breaking the lower edge of the barrel or chamber lip. On my FAL, the bullet tip was getting stuck on the sharp edge of the barrel face. Rounding it off seemed to help prevent this. I used one of the small stones from a Dremel kit, but I did this by hand, not with the Dremel. I have basically solved the jamming problem by raising the mag lips on a number of mags so that the round can release and rise sooner. I now have many mags which work. Although this is not an elegant solution, it is cheap, does not ruin the receiver, and makes the rifle work. If you have a dozen mags that work well in the rifle, that seems pretty good to me. Your rifle may seem to be a POS to you, but if it is in good condition and well-assembled, solving the feeding problem is well worth doing. Many of these Frankenfals have problems, no matter what receiver is used.

Best wishes,

Drakejake

MikeyB
December 31, 2005, 15:59
Drakejake,
I used a cone shaped bit on the dremel and worked the chamfer area just below the breech face. Seemed to help a little but still did it, and it was the round on the left side of the mag was the problem. Bending the mag lip down cause the round to cock to the center of the feed ramp sooner and not on the left hand side as before.
I modified all my inch and metric pattern mags with a ball peen hammer.

Figure I'll get it running good one day.

MikeyB

drakejake
December 31, 2005, 16:34
MikeyB,

I tried a number of the suggested solutions for feeding problems but had the most success from modifying the mag feed lips with pliers. I tried to accomplish two things: make the round ride up as high as possible and make sure that the case bottom sits up well so that the bolt can strip the rounds. Once the mag looks good, I try inserting it into the rifle. I want the mag to fit tight and just barely lock in with a slap on the bottom. If the mag won't lock in, I look for the high point on the feed lips that is preventing latching and bend it down a bit. I will sometimes use a file or some fine sandpaper to get the lips the way I want them. With two inch-type Bren 30 round mags, I filed on the back of the mag in order to get it to latch. I believe that the result of these slight modifications is that the tip of the round barely touches the feedramp, if at all, and goes right into the chamber. First I try handcycling with the firing pin out and the safety on. Mags that pass this test are then used in range firing. I have about a dozen mags that work fine in my FAL. Some mags cannot be made to work and I put them aside. By the way, I have observed that on both the unibrow and duobrow feedramps, the tips of the rounds do not touch the depressions anyway, but hit outside them. The problems with unibrow receivers have nothing to do with the fact that there is only one depression in the middle of the ramp, so far as I can tell. The problem is with some other specs of the receiver.

Best,

Drakejake

MikeyB
December 31, 2005, 18:57
Drakejake,

The fitment of the inch pattern magazine lips to the top of the magazine well in my Century receiver is tight. Bending the feed lips up would make it even tighter and would bend the lips back down when inserting a mag during my troubleshooting. Since the metric mags have a loose fit my guess bending the lips up would work fine.
In Feb I should be able to do a functional live fire test with all the mags fully loaded.:smile:

Thanks for the info.

MikeyB

drakejake
December 31, 2005, 19:30
Inch mags are very, very tight in my FAL; metric mags work much better. You can do some filing on the front lip of an inch mag to get it to fit, but I am not sure it is worth it. My inch mags are tight side to side as well as front to back. I have a couple of Bren mags which seem to be inch but have a smaller than usual beak or metal lip on the front. These work fairly well. If it is impossible to raise the feed lips and get the mag to lock in, you can do some filing and sanding instead and get the same result--allowing the rounds to ride high in the mag and escape the mag lips sooner than is customary.

Drakejake

MYFALRX
May 05, 2006, 16:28
Before I take my FAL in to getting checked by a gunsmith, would a magazine cause the bolt not to close all the way. I don't know if I have a metric or inch mag and when I load it up and try to chamber a round the bolt stays open about a 1/2 wide.

lantirnjock
May 07, 2006, 12:14
I originally had problems getting my Fal to cycle rounds. I have a mono brow style feed ramp which was giving me hell. After some careful grinding and polishing the feed problem is solved but now I'm having an issue with blowback. I tried all gas regulation settings with no fix. I manually pushed the gas rod back into the bolt to see if there was any noticable binding and it seemed to be ok. However while i was working on the rifle I had stretched the recoil spring out some. Though i dont see a noticable difference when charging the rifle, I'm wondering if that had anything to do with it. When firing the rifle i watched the bolt to see if it even attempted to cycle and it doesn't appear to move more than 1/8" to a 1/4". Any ideas?

W.E.G.
May 07, 2006, 12:18
Both of you new guys need to post your questions individually in the gunsmithing forum on this site.

You have posted to the reference forum. This forum is for reference, and not for original I-need-help queries.

lantirnjock
May 07, 2006, 12:20
I had the same problem with my bolt not closing all the way. After i ground my my ramp down some it stopped. Then again right I have to charge the weapon with each round fired due to lack of blow back. What i did was seperate the to halfs (upper from lower). Remove the bolt cover and load a mag with 5 to 10 rounds and manualy slide the bolt back and forth loading a round each time. This will give you a better look at the action and to possibly notice any hang up points. Its a good idea to remove the firing pin first just in case.:skull: