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Discussion Starter · #1 ·
I believe I am having a feed ramp issue - I will leave the barrel company name out as I am trying to determines whos end this falls under to fix first. I recently purchased a barrel from a manufacture whos website states that it comes with M4 barrel extensions. I bought a new stripped PSA upper with M4 feedramps as well. When installed there is a "step up" where the upper feed ramps and barrel feed ramps meet. This is causing my ammo (Hornady 120 SST) to get a deformed bullet tip when it loads from the magazine as I can only assume it is hitting this step up. The rifle still functions but a deformed bullet tip will cause accuracy issues and is unacceptable. This "step up" can be felt with a toothpick when rubbed against them both. After looking at several other uppers of mine it appears that these feed ramps look more like "rifle" barrel extension than M4 ones and they certainly do not match up with the upper ramps like all of my other rifles- they have more of a rounded bottom to them then a traditional M4 barrel extension does.

What should my next steps be and what does it look like to you guys?

Here is a picture of the feed ramps in question:
Auto part Spoke Crankset Wheel Tire

Here is my MK12 build with matching M4 feed ramps and M4 upper ramps that match up perfectly:
Auto part Tire Wheel Brake Automotive wheel system
 

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Just take a chainsaw file or a dremel with chainsaw sharpening stone and blend the ramps.
 

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IMO those are rifle ramps not M4. BUT me being me I would hit them with a 3/16" chainsaw stone in a dremel rather than waste time sending it back.
 

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You also could flare your magazine lips to get the bullets to ride higher/nose up. This will reduce the interference between the tips and the ramps.

http://68forums.com/forums/showthre...Magazine-COALs&p=643823&viewfull=1#post643823

Factory 110 S&B shown in the image below


It doesn't take much. I try and get the nose of the bullet to sit at least a 1/10 of an inch higher than level with a goal of 0.15". I use needle nose, grab the lip and roll it up and out. It doesn't take much.

 

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Discussion Starter · #5 ·
Xman, I have seen those post in regards to modifying the magazine and have done it to a small degree but to me that is still sort of a bandaid fix to what I know a correct feed ramp/ barrel extension combo should be. I have contacted the barrel manufacture and will be sending the barrel into them tomorrow. I will update this thread with the progress. Thanks for everyone's assistance thus far.
 

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If you paid for a new barrel with M4 feed ramps, then you were sent the wrong barrel.

I would request the correct barrel.
^^^THIS^^^
let em keep it and order an ARP barrel, probably cost the same too.
when i'm sent something thats incorrect or bad, i make sure i'm not the 1 payin for their mistakes, not even any shipping, I demand it 1st with company, 2nd with my CC company if needed. I've never covered the funds for others goofs, best way to get them to have top notch service & quality control.
 

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^^^THIS^^^
let em keep it and order an ARP barrel, probably cost the same too.
when i'm sent something thats incorrect or bad, i make sure i'm not the 1 payin for their mistakes, not even any shipping, I demand it 1st with company, 2nd with my CC company if needed. I've never covered the funds for others goofs, best way to get them to have top notch service & quality control.
It's one of mine. It isn't the wrong barrel. Barrel extensions are sent to us hundreds at a time from AO. AO makes both kinds of extensions and it looks like 1 rifle found it's way into a box of M4s. My guy doesn't take each extension and slide it into an upper receiver to check the alignment since it's near impossible with hundreds of companies machining receivers. As far as I know it's the first one in 8 years out of tens of thousands of barrels.
When it happens to you you think the world is coming to an end but for them to only send 1 out of all the extensions I have seen in the past 8 years I think they are doing pretty good.
Metal Iron Nut Font Auto part
 

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Sogan, are you satisfied otherwise with the barrel? Is it accurate? Feed ramps aren't that hard to polish out.
 

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Sogan, are you satisfied otherwise with the barrel? Is it accurate? Feed ramps aren't that hard to polish out.
The barrel is coming back to me. If I can time an extension to the gas port I will, if not I'll send him another barrel.
 

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Discussion Starter · #11 ·
Sogan, are you satisfied otherwise with the barrel? Is it accurate? Feed ramps aren't that hard to polish out.
I don't think I can comment on the accuracy as I never loaded the magazines one at a time when testing accuracy. I think my results were skewed due to the feed ramp step up damaging the soft tips of the 120 SST. I understand that the ramps probably are not difficult to polish out but it's not something that I feel comfortable doing if the original company was willing to look at it and fix it accordingly - As constructor stated, I sent the barrel and bolt back to him. I also included the upper that I was using to ensure that the ramps match up perfectly before being returned to hopefully correct this issue on the first time around.
 

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Typical Customer Service from ARP. Stepped up and claimed the problem and providing a fix.
 

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I pictured a company mass sending out these with wrong description
No worries if its Arp/H's,
didnt know it was your's H,
goof makes sense in your case and we know goofs dont happen often with you and when it does you take care of it which is the important part for sure.
a lot I see when I have issue's with other companies is they dont want to take any responsibility for anything and it happens all the time with them even telling by the reviews of their item (i've learnt to check reviews 1st,lol. not many issues anymore)
 

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I routinely blend and polish feed ramps when assembling a new upper receiver and barrel. Its a simple job, using a 3/16" cone-shaped Gremel grinding tip, followed by their rubber polishing tips. Once your ramps are smooth and your magazines tweaked so the bullet tips are pointing slightly upward, failures to feed on this account are a thing of the past. FWIW, my last build involved a 6.8 ARP Scout barrel and a new Mega receiver. The ramps matched so perfectly, the usual blend and polish routine were not needed. - CW
 

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H and Arp are good people.
Had a missing JALmuzzle device for an order and I sent an email about it and the same day I had a new tracking number with replacement. A-OK in my book. Another plus 1 for ARP
 

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Discussion Starter · #16 ·
I have not questioned ARP customer service once. It is actually one of the main reasons I chose to go with their product over some of the competition - I have read plenty of threads on here about them and knew that they were active on this thread and most users regarded them as G2G. Constructor responded to my PMs quickly and I was not planning on even mentioning the barrel manufacture until the problem was resolved. I am sure ARP will work to correct any issue as I have seen time and time again on this forum.

I will keep this thread updated with the progress.
 

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Received the parts today and as it turns out the extension is a M4. Anytime the feed ramps extend into the diameter of the extension they are M4. Rifle extensions feed ramps stop at the corner, junction of the end and diameter. The photo looks a lot worse than it is. I went ahead and hit the ramps with a dremel for about 30 seconds to make sure there is no overhang of the extension.
There is no way that 100 different manufacturers of receivers and 4 or 5 manufactures of extensions can match up perfectly . As a "builder" it is your job to blend parts like this.
IMO the ramps in the receiver are a little on the small side and should be blended to the larger ramps of the extension. I didn't see any copper on the extension or ramps of the receiver but if you look in the top photo you posted you will see a streak of copper inside the chamber on the top like the bullet tip may be hitting the top of the chamber.
In that same photo you will notice a small yellow dot at 12 O'clock That dot is on the inside of the barrel extension in your photo. It is on the extension I am sending back proving it's the same extension. I placed a small orange dot on your receiver between the feedramps and took some photos that show both the extension and receiver.
Richard will return the parts to you on Monday.
This shows the difference between a rifle and M4 extension.
http://guns.jtrade.us/images/ARBuild/m4cuts0xk.jpg
 
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