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View Full Version : Feed Ramp modifications for AR-15


thesheepdog
August 12, 2010, 11:03 AM
Here is a picture of the ramps on my 6.5 Grendel upper. I had some FTF's because of rifle ramps, with M4 extentions, so I made the call of using a dremel to file them down, and I also made them a bit wider to help accomodate the larger 6.5mm round.

I know the work doesn't look great, but the issue has been fixed.

I still need to polish the ramps, just to make things even smoother.

Let me know what you think, good or bad.

zombieslayer
August 12, 2010, 11:21 AM
I may have to do this for my S&W's. The factory feedramps are pretty cruddy. I have 20 some-odd guns, and the M&P's have the ugliest of them all. I'm probably going to take mine in to my local gunsmith. Glad you were able to fix your problem!

thesheepdog
August 12, 2010, 11:23 AM
I have 20 some-odd guns, and the M&P's have the ugliest of them all.

Uglier than mine? :)

How do mine look? Do you think I did a decent job?

zombieslayer
August 12, 2010, 08:50 PM
They look better than mine! One of mine has smoother ramps than the other, but they look like a blind guy who got fired from Century went at them! Not bad sir! You said it fixed the problem so more power to ya. I'm a bit timid with the dremel myself, I've ruined a feedramp or two though.

thesheepdog
August 13, 2010, 08:17 AM
I'll post a pic when I get the ramps polished :D

thesheepdog
September 10, 2010, 03:20 PM
Polished ramps.

I still need a picture of it after i soaked the inside with some Break Free CLP.

zombieslayer
September 11, 2010, 01:15 AM
Nice!

c_jackson
September 11, 2010, 01:38 AM
I did the same thing with my 5.56 AR-15. It had a problem with Wolf and Silver Bear rounds. Using a bullet felt-tip on my Dremel, I achieved the same result. A little bit of polishing, good to go! I found out later on, lower-cost rounds equal HUGE problems with cycling. In the military, M855 rounds were the norm, out here in the civilian world, stick powder and nickel-plated casings lead to a lot of feed and ejection problems. Polishing the feed ramps with a felt tip along with Dremel 420 compound ( incidently, it's nothing but Cerium paste) diluted with some tap water solved all my malfunctions. If you're firing M179 through your thunderstick, I recommend using this. Those of you senior folks from Vietnam and the first Gulf War have taken your lumps just like me with ball-powder loads. We all know the rest of the story, so you guys can fill in the blanks.

Slamfire
September 11, 2010, 10:03 AM
I don't know what the "before" looked like, but the "after" has me worrying.

Polishing is OK in my book, but metal removal is bad.

How much of the supporting surfaces of the barrel extension were ground away?

I have a couple of buds who shoot the 6.5 Grendel or maybe the 6.5 Turbo in AR platforms. They have experienced cracked bolt lugs. I don’t know what the bolt thrust is on a Grendel but it is obvious that the increased thrust over a .223 has eaten into the safety margins and fatigue lifetimes of a design built for a .223 cartridge.

It looks to me that you have ground down the locking seat surface in the barrel extension.

Better check your bolt lugs and see if the increased stress, due to less metal supporting the lower bolt lug, is causing undue wear.

Technosavant
September 11, 2010, 10:09 AM
If you had rifle ramps on the barrel with M4 ramps on the upper, it looks like the result will work, but personally I'd probably just get a different upper. But your result should feed without bullets nosing into the crack.

thesheepdog
September 13, 2010, 08:08 AM
How much of the supporting surfaces of the barrel extension were ground away?

Not very much at all.

I did most of the grinding where the M4 extensions are. I did make the ramps a bit wider on the barrel; just for old time's sake.

I have fired about 30 rounds through it-this was before i polished the ramps.

I can see bolt lugs cracking if you are using hot loads.

Technosavant,

In very rare instances will the rifle ramps work with M4 extensions. Most situations it won't work because the tips of the bullets get caught up on that little lip between the ramps and extensions-exactly what happened to my Grendel rounds.

After grinding, cleaning and polishing the ramps; the problem has ceased and my AR feeds the AMAX rounds just fine.

rjrivero
September 13, 2010, 08:42 AM
I don't know what the "before" looked like, but the "after" has me worrying.

I understand your concerns, but I really don't think there is much of an issue here.

It looks as if the M4 Barrel Extension just didn't mate well with the upper. A new upper may "solve" this issue, but a little judicious use of a dremel with a proper stone and some polishing is hardly cause for concern.

The 6.5 Grendel is indeed loaded to 50,000 PSI, but .223 is loaded to some 62,000 PSI. Again, not much concern.

I think the lug issue that some folks are seeing is due to the fact that there are no "mil spec" 6.5 bolts out there, and some are just weaker than the "mil spec" available for .223.

The 6.5 is still relatively new, and I would expect some "growing pains" as the weaknesses in the 6.5 propietary parts are addressed.

Technosavant
September 13, 2010, 10:25 AM
In very rare instances will the rifle ramps work with M4 extensions. Most situations it won't work because the tips of the bullets get caught up on that little lip between the ramps and extensions-exactly what happened to my Grendel rounds.


I know. You can use a M4 ramped barrel with a rifle ramped (actually non-ramped at all) upper, but the other way around it doesn't work. The ideal answer is another upper with the right ramps, but competent work on the barrel extension will get the job done- IMO, it's *really* easy to screw stuff up with a Dremel (ask 1911 guys about Dremeling the feed ramp), and given that the barrel is the most expensive piece of the rifle, I myself would rather get another upper than risk trashing a barrel. Besides, that extra upper will end up becoming another rifle; we all know that's how it works... spare parts don't just sit there, they cry out into the owner's mind to build them into a complete firearm. :D


After grinding, cleaning and polishing the ramps; the problem has ceased and my AR feeds the AMAX rounds just fine.

That's the important part. As a wise man said, if it works, it ain't stupid.

thesheepdog
September 13, 2010, 02:43 PM
Well, I will be putting a range report out.
As soon as I can get some time to load up a bunch of ammo, I plan on doing some drills and such, and hopeully-I have confidence-my gun will function flawlessly.

DanThaMan1776
September 13, 2010, 02:52 PM
good.. because by doing what you did I don't think you invite any negative results and if it fixed the issue then kudos!

thesheepdog
September 13, 2010, 03:16 PM
Thanks Dan,

I've done a lot of metal work in my life-licensed welder-and from my experience, i think I did a satifactory job, given the constraints I had to deal with (time, money, tools, etc).

thesheepdog
September 15, 2010, 01:20 PM
This is a pic of my ramps after being cleaned with CLP and In my opinion, they look pretty darn good for a Dremel project. :D

Technosavant
September 15, 2010, 02:09 PM
Wow, nicely done.

thesheepdog
September 15, 2010, 02:11 PM
Wow, nicely done.

You mean that for reals? :D

I know some guys were bashing me for doing it myself with a Dremel, but I would like some honest opinions of how the ramps look.

Technosavant
September 16, 2010, 12:54 PM
Yeah, I mean it. It doesn't look like it was done at the factory, but given the level of Dremel ham-handedness I've seen in internet pics, that looks astonishingly good. Of course, it probably helps that you have experience in metalworking- my metalworking skills are even worse than my woodworking (which itself is mediocre at best), so I'd never try that myself. But your result looks well done and properly blended; I doubt you'll have issues with bullets nosing into cracks and hanging up.

thesheepdog
September 16, 2010, 01:15 PM
Well thanks TechnoSavant,

At least someone appreciates a budget minded job-well-done-DIY project.

I will admit it was scary trying to get the ramps just right, but i suceeded. :D

UniversalFrost
September 16, 2010, 02:09 PM
i have use a regular rounded file in the past to make m4 ramps in the extension and the upper then polish until perfect.

also if you get pmags you won't have to deal with this at all on .223 / 5.56 ammo (wish they made p-mags for my 6.8)... the p-mags sit higher in the magwell and keep the rounds higher than standard mags.

a quick google search will show some neat photos of p-mags and standard mags comparisions

thesheepdog
September 16, 2010, 02:24 PM
i have use a regular rounded file in the past to make m4 ramps in the extension and the upper then polish until perfect.

also if you get pmags you won't have to deal with this at all on .223 / 5.56 ammo (wish they made p-mags for my 6.8)... the p-mags sit higher in the magwell and keep the rounds higher than standard mags.

a quick google search will show some neat photos of p-mags and standard mags comparisions

I would use them on my 6.5 if indeed Magpul made the PMAG for 6.5.

I have like 6 PMAGS for my 5.56

FoxtrotRomeo
September 16, 2010, 02:36 PM
hmm...

My 16 inch AR has the standard feed ramp and not the M4 style. Never had a problem with Silver Bear 62 grain HP rounds since I broke in my mags. When my old man grabs the AR though, yeah jam is on the way. I dunno what he does to do that.

I'll keep this in mind when I get my 6.8 upper though for my new AR.

It doesn't have to be pretty. It just has to work and work right.

thesheepdog
September 16, 2010, 03:33 PM
I'll keep this in mind when I get my 6.8 upper though for my new AR.

It only will affect you if you have a rifle ramp with M4 extensions (custom build screw up). If you're buying a 6.8 Upper you shouldn't run into any problems.

UniversalFrost
September 18, 2010, 11:13 AM
for 6.8 you are strongly encouraged to have m4 ramps on the receiver and barrel extension.

you are welcome to check out the 6.8 forum for more information.