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View Full Version : UPDATE: Imbel shaving brass. Where do I dremel?


LongGun
April 08, 2002, 15:00
Already checked the threads & archives but I'd appreciate some more specific info.

BACKGROUND INFO:
DSA's refinished G-1 on a new Imbel Receiver
Had FTE problems first time out, drilled gas port to 7/64", FIXED.
Gas system is fine, no binding or wobbling.
Recoil springs are clean.
Bolt/Bolt carrier do not bind at all when there is no magazine in place. Very sharp.
However, I am still experiencing intermittent FTF when the magazine is in place.
Used a couple of different mags.
The round gets caught up half way into the barrel.
Brass shavings found between the feed ramps and the barrel.
Substantial brass markings on the bottom of the bolt and a nice gouge on the top of the following round.

I'm thinking it's a combination of two things.
1) Botttom of bolt dragging along next round in the magazine and
2) Friction of the round travelling over the feed ramps.

Please, any suggestions are greatLy appreciated.

Dave

[ April 08, 2002: Message edited by: LongGun ]

[ April 23, 2002: Message edited by: LongGun ]

ce
April 08, 2002, 15:08
Mebbe a weak recoil spring. Is it kinda wambly and easy to pull back on yer charging handle, or is it stiff and tough ?
What's your gas setting?
It vouldn't hoit if you should polishing your feed ramps with some 400 grit, already.
Vhat's a little sandpaper, it's too much to ask?

LongGun
April 08, 2002, 15:37
Gas setting at 4.
Anything past that just kicks the crap out of my shoulder.

It's not real tough to manually charge but it is stiff. When the mag is empty & I use the bolt release, she snaps shut with authority. I was thinking about the recoils spring, but what really concerns my are the signs of fricttion: gouged casing & metal filings.

ce
April 08, 2002, 15:53
Yeah, I'm not so bothered by brass shaving, all that stuff is clangin' around pretty good, and when brass meets steel...
You don't notice or care til the gun stops workin', and then it's what's all this stuff?
With healthy recoil and all, springs sound good, but the newness and refinishedness of your stuff may be causing the friction, or the feed lips on the inside of the mags may be cutting some metal off the cases.
Smooth and polish.
If that doesn't work, try polish and smooth.

ByronF
April 08, 2002, 16:04
There was some talk a while back about smoothing out the underside of the receiver lips (just above the magazine). Some careful sanding seemed to have been the fix. Someone had even posted some pictures of the trouble spots. Maybe edit your title to read "Imbel shaving brass. Where do I dremel?". I think the author advised knocking off the sharp corner on the underside of the lips. You should be able to see where the cartridge hangs up. There might even be some brass marks on the suspect area.

FWIW, my Imbel does it too if I drop the bolt on a full mag using the bolt-hold-open button. Instead I rack it like an M14 (pull handle fully rearward and release smartly).

Byron

W.E.G.
April 08, 2002, 16:28
Originally posted by LongGun:
<STRONG>Gas setting at 4.
Anything past that just kicks the crap out of my shoulder.</STRONG>

Sounds to me like you are running on as little gas as you think you can get by with. This is a mistake.

When you run the balance that close, the bolt may not cycle all the way back. If the bolt does not cycle all the way back, it may just barely grab the rim of the case as it rams the case forward. All the springy-sproingy slam-bammery then allows the bolt to slip over the base of the case as it goes forward. So, you get bolt-over-base malfunctions.

If the recoil bothers you, hold the rifle more firmly into your shoulder and/or stick a towel or something under your shirt. Close the gas all the way. Fire the rifle. Tell us whether you are still getting rounds "caught up half way into the barrel."

"Eh, wot's that you say recoil???"
http://users.erols.com/gary.jeter/scowler1.jpg

Don't worry about the brass shavings. This is normal. Blast the shavings out with compressed air.

LongGun
April 08, 2002, 21:18
Jeter,
No stranger to recoil. 7mm mag, 30-06. All I was saying is that the rifle cycles fine on 4 and up. After drilling the port, the gas hasn't been a problem. I'm convinced its friction. I've read earlier posts and Byron reiterated about slightly polishing the rails below the bolt (receiver rails). Know anything about it?

W.E.G.
April 08, 2002, 21:22
I'd turn up the gas before I removed metal from the receiver.

YMMV.

LongGun
April 08, 2002, 21:25
Jeter,
I know. Already cranked the gas all the way up and same problems. What about the gouged cases? Doesn't that say anything?

LongGun
April 08, 2002, 21:27
It's also not the shavings I'm concerned about, its the unfired case stickin half way into the barrel.

W.E.G.
April 08, 2002, 21:43
OK.

I think I follow you now. At first it sounded like you were saying the problem did not occur when the gas was turned-up.

I have the pics Byron is talking about on my other computer. I'll hunt them up for you tomorrow.

LongGun
April 08, 2002, 21:45
Thanks Jeter,
Any help will be greatly appreciated.

W.E.G.
April 08, 2002, 21:51
Scott S
Member


FALoholic # 355
posted February 22, 2001 11:15
--------------------------------------------------------------------------------
A week or so ago I posted a message regarding a recent range trip where I experienced several failures to feed Hirtenberger with my DSA standard length. Extraction and ejection worked, but the bolt would stop after stripping a cartridge about halfway out of the mag. This failure to feed occurred after firing shots and after dropping the bolt using the release. Called DSA and spoke to their 'smith. Said that I should adjust my gas setting, and that a slightly more vigorous cycle might be all that was needed (same comment I got from Gary J.). Haven't been to the range to test the gas adjustment fix.
However, that fix doesn't address the feed problem when dropping the bolt using the bolt release tab/button (Norman74 and Mt Guerrilla also reported this problem). Looked at this problem last night. Every time I inserted a full mag and hit the bolt release, the bolt would fail to completely strip the round from the mag. Tip of cartridge would go into the chamber a quarter to half inch, but the rim/head would still be in the mag. With a mag of less than 10 rounds, dropping the bolt chambered the round every time. So, it seemed that full mag tension against something caused enough friction to prevent complete feeding. Looking closely at the action as I cycled it slowly with my hand on the charging handle, I could see that the shoulder of each cartridge was scraping on the edge of the receiver feed rails. This scraping left a mark that looked like the cartridge had been rubbed with the edge of a piece of 120 grit sandpaper. Just one small spot on the feed rails caused this scraping. Look from underneath the rifle through the mag well into the action. At the back of the mag well the receiver feed rails are parallel to each other. Going forward, they diverge. They then converge and finally become parallel again. The *very* shallow angle where the convergence ends and the front parallel part begins is where the rounds were hanging. When you insert a mag with rounds in it, the body of the cartridge just behind the shoulder touches this point on the receiver. Shining a flashlight into the mag well I could see a thin layer of brass on the rails at this point. This edge was sharp enough to dig into the case shoulder, slowing the bolt just enough to stop it on full to nearly full mags.

In lieu of running several hundred rounds through the gun to help polish this sharp edge, I opted to go the Dremel route. Used a little, hard rubber-tipped bit impregnated with a fine abrasive to ever-so-slightly break the bottom edge of the rails at this point. I also polished the inner rail surfaces and lower rail surfaces for a quarter inch in each direction--just enough to remove the parkerizing. I went very slowly, checking my progress very often. Screw this up and you're hosed.

Now, when I insert a full mag and drop the bolt using the release, the cartridge slides home without a hitch. And the cartridge doesn't have the small scrap on the shoulder--just a tiny polished-looking mark in the same location.

W.E.G.
April 08, 2002, 22:01
What I need to know is are you getting bolt-over-base failures or is the bolt simply stopping with the bolt engaged against the base of the cartridge? If the latter, the Scott S. solution may work for you. If it is bolt-over-base, I think there are other forces involved.

ratas calientes
April 08, 2002, 22:04
LongGun -

I'm with ByronF on this one.

My first build is an Imbel on an Entreprise "file-to-fit" receiver. Skipping all of the sordid assembly problems . . . when I took it to the desert for the first test, the only problem that it had was a failure-to-feed on the first round out of a full 20-round magazine. The round only made it half-way into the chamber. The rifle would chamber the 19th and all subsequent rounds. I was sure to pull the charging handle all the way back and sharply let go.

When I got home, I decided to compare the profile of the receiver "lips" (just above the magazine) with those on my DSA StG58A. So I loaded an odd and an even number of rounds into two magazines. I inserted these into my DSA rifle, and traced the profile of the lips with a Sharpie pen onto the top round in the magazine. I then inserted these mags into the Entreprise rifle. Guess what? The receiver lip on the left side (that corresponds with the first round out of 20) did not have the correct profile. So I filed it back to match. I also "broke" the lower edges so that it was no longer "sharp". I did this with an automotive point file. You don't need to take off a lot of material to break the edge, so I would shy away from a Dremel if you tend to take off a lot of material fast. Sandpaper would also work, but it would be slow.

I then removed the firing pin, and I tested feeding the first round from a full mag. It now works fine (in the garage!). I plan on testing it in the desert this next weekend.

I also remember reading about this in a previous post a few months ago, complete with pictures, but I don't remember how I found it.

Hope this helps.

Ratas

:cool:

[ April 08, 2002: Message edited by: ratas calientes ]

LongGun
April 08, 2002, 23:04
Jeter & Ratas,

The situation Scott described seems to be the problem. I had read this post earlier today and that is what prompted me to consider filing the rails. I'm going manually cycle some rounds tommorrow night to verify before I start removing any material. I'll post my results as soon as I can. Thanks Again.
Dave

Upside Down @ 100 MPH
April 08, 2002, 23:39
Originally posted by LongGun:
<STRONG> What about the gouged cases? Doesn't that say anything?</STRONG>


Yeah, that the receiver needs to be de-burred. If the gun is making brass shavings it isn't functioning 100%. Two places need to be worked on. First, the underside of the receiver rails that sit above the mag. You can do this with sandpaper by hand. Just break the sharp edge. The other place is the top of the feed ramps. A dremel is beter for this job. Just break the sharp edge, that all.

The gun will cycle better and it won't gouge cases after this is done. I have no idea why this work isn't performed at the factory. It should be.

ratas calientes
April 08, 2002, 23:57
Yep, that's the post that I remember reading.

From Upside et. al. - sounds like another vote for edge breaking.

Let us know how it works -

Ratas

Upside Down @ 100 MPH
April 09, 2002, 00:58
http://www.printroom.com/_vti_bin/ViewImage.dll?userid=gregrrr&album_id=62841&image_id=3&courtesy=1

This is a pic of my Group Buy Imbel on an Entre'prise receiver. If you look closely you can see where I radiused the top edge of the feed ramp. The original angle is left alone. You can also see where the bullet and casing "color" the ramp and the barrel but there are no shavings to contaminate the breech.

Upside Down @ 100 MPH
April 09, 2002, 01:02
http://www.printroom.com/_vti_bin/ViewImage.dll?userid=gregrrr&album_id=62841&image_id=2&courtesy=1

This is a pic of the receiver rails. It's pretty self explanatory. All you do is knock down the sharp edge so the rail doesn't scrape up the casing.

Ichabod
April 09, 2002, 07:51
Rather thing hitting the rails with powertools right away:try using some Scotchbrite on the rails first.I usually use the maroon to clean up the rails.This seems to be enough to de-burr.I had the same problem with both my imbels and numerios bolt actions.Concentrate on the underside primarilly.
Good Luck

Aifwikir
April 09, 2002, 08:52
Here's my solution

http://www.printroom.com/_vti_bin/ViewImage.dll?userid=Aifwikir&album_id=25819&image_id=13&param=45414

Use some fine emory cloth and shoeshine buff the areas in the picture. It will solve the FTF and stop the brass gouges.

:D
Aif

LongGun
April 09, 2002, 08:55
Thanks for all the help guys. :D
Dave

W.E.G.
April 09, 2002, 16:48
Aif found the pic I was looking for last night.

LongGun
April 10, 2002, 15:23
Guys,
What's the easiest way to dummy out some 7.62? I know there is that plastic hammer thingy, but not looking to buy anything. WECSOG style please.

P.S. Jeter-just read your post "barreling a Hesse receiver - crunch...grind...swear... (WECSOG)"
ROTFLMAO http://www.stopstart.fsnet.co.uk/smilie/rotfl.gif

W.E.G.
April 10, 2002, 16:40
I reckon if I had to make dummy rounds without reloading tools, I'd fire some rounds with the gas turned off, and manually eject the spent cases. (This should keep the bases from expanding so much as they do in semi-auto mode.) You might need to do the WECSOG-pogo to get the spent cases out if you fire them with the gas turned off.

Once I had a supply of gas-off spent cases. I'd slam them in the chamber a few times to "resize" 'em. Spray some lube on the cases first. That will make it easier to yank 'em out of the chamber.

Next, pull some bullets from some live rounds. You can probably do this with pliers if you are persistent. Use one of those doily thingies from the table to pad the pliers.

Burn the leftover gunpowder in the back yard at dusk while your neighbors are on their deck. Helps if you chant and wear your kid's indian headdress while you do it.

Spray your bullets and fired cases with carburetor cleaner. Best to do this outdoors. Carb-cleaner does kill the grass.

Now, fill the empty cases with corn meal. I trust that you do eat cornbread with your pinto beans. Keeps your personal gas port going.

If you don't use corn meal, or some such, as case-filler, the bullets might get rammed back into the cases during experimental feeding operations.

The bullets are going to be kinda loose in the necks. Figure out how much corn meal you need to get the bullets to sit where you want 'em in the cases. Then, mix up some JB Weld. Splop the JB inside the case necks to glue the bullets at the right spot.

Let the glue dry & Voila!

ratas calientes
April 10, 2002, 17:55
LongGun -

So, ya gonna practice feeding the rifle in the garage like I did? Not a bad idea to make up some dummy rounds. Like I mentioned earlier, I just used live ones AFTER I removed the firing pin. Really not the best thing to do. (I was impatient.) When I did it, after the first round fed, I yanked on the charging handle again to feed the second round. The first round went flying off into a bunch of junk piled on the garage floor. Of course, I had to go fishing for it. The wife would not be too happy finding the odd 7.62 round in her pile of sewing odds and ends. ;)

Ratas

John Culver
April 10, 2002, 19:27
"bunch of junk piled on the garage floor." and the "her pile of sewing odds and ends."

So does that mean they are the same? :)

ratas calientes
April 10, 2002, 23:18
Sometimes :D :D :D :D :D - RC

LongGun
April 11, 2002, 09:23
Yeahh, the woman aint too happy when the gun goes boom in the bedroom, well at least not the rifle. (nudge nudge) You guys should also see the container of various sorts of ammo by the laundry machine. I have a mission to collect one of each & sometimes forget they're in my pocket.

Woman: "WHAT IF I WERE TO THROW YOUR PANTS IN THE DRYER WITH AN F'N BULLET IN THE POCKET?! :mad:

Me: "Well at least you'd know when the load was done." Hehe! :D

Me: sleeping on couch. Hehe. :D

Thanks again guys.

ratas calientes
April 11, 2002, 14:53
I had better leave this one well enough alone - RC ;)

Proud FAL Shooter
April 12, 2002, 23:35
Anyone ever noticed dented FMJ tip? When I let the handle go, the bullet gets half stripped, the tip is caught on the feed ramp. I could ram the charging handle to force the round to chamber (forward assist :D), but it'd dent the bullet tip. I can see visible brass shaving and dented bullet when I extract the unfired round.

I'll try the polishing rails & feedramp. Great tips.

[ April 13, 2002: Message edited by: Proud FAL Shooter ]

LongGun
April 23, 2002, 15:30
HERE's THE UPDATE:

Polished the feed ramps & receiver rails with some 400 grit. Went upstate this weekend and she cycled like a champ. Went through about 200 rounds on gas setting of 4. Not a hick-up.
Thanks to all for the help.

ratas calientes
April 24, 2002, 08:58
Glad to hear that you got it runnin'! - RC

[ April 24, 2002: Message edited by: ratas calientes ]