Western Wa Smith for ar10 barrel ext work

osprey · Feb 6, 2019

I have a 308 AR barrel that I believe has a extension that has the feed ramps cut wrong. It jams tips of bullets into breech and will not chamber round. I have tried different combos of mags uppers and lowers and have come to the conclusion it is the extension itself. I am looking for a Smith that can handle a rework or replace the extension on this barrel. Thanks in advance.

NWCustomFirearms · Feb 7, 2019

We can work over the feed ramps but if that does not take care of it and the extension needs to be replaced you might be better off just sending the barrel back to the factory. More then likely they won't even try to fix it, they'll just send you a new barrel.

titsonritz · Feb 7, 2019

NWCustomFirearms said:
We can work over the feed ramps but if that does not take care of it and the extension needs to be replaced you might be better off just sending the barrel back to the factory. More then likely they won't even try to fix it, they'll just send you a new barrel.

This

osprey · Feb 7, 2019

Well it is a bit of a unique situation that I probably made worse by my actions. The barrel is a Fn chrome lined that came on a Gen 1 PSA upper. After putting this upper on one of my lowers I decided it was not going to work due to PSA's incompatibility issues. I did want the barrel though so I stripped the build down and ended up selling the rail and upper receiver. Fast forward to now and I built it out on a aero precision upper receiver and discovered the feed issue. After monkeying around with different mags lowers and yet another brand of upper I am of the opinion it is a feed ramp issue with the extension. Problem is I think it needs more material at end of ramp and I am not convinced it can be reshaped to work. That is why I asked about replacing the extension. Also being I stripped it out of a complete upper from PSA, I doubt they will warranty it and I really wouldn't expect them to. For all I know if I had bought one of their proprietary gen 1 lowers to go with the upper it may have run fine. So here I am with a very nice unfired Fn double chrome lined barrel that won't feed.

DirectDrive · Feb 7, 2019

I looked at some pics of the PA-10 feed ramps....kind of conventional looking dual ramps.
Then I looked at a POF 308
Looks like POF uses a 458 SOCOM type ramp
Maybe that would fix it ?

I would try blackening the bullet on a cartridge and see where the interference is.
Might also have to blacken the barrel extension.

PA-10 (from web)

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POF 308AR (from web)

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osprey · Feb 8, 2019

Yes mine is similar to first pic but I do not think the two path vs the uni ramp is the problem. It is the profile of the two ramp areas allowing the tip of bullet to remain too low and hang up just below breech face cone where I marked up the photo. I am considering using a dremel to make two slight lead in ramps on the breech face where I marked in red. I did something similar with a Fal years ago and it runs like a sewing machine to this day.

osprey · Feb 8, 2019

Thinking about it further it may be the lead in cone to the chamber is cut at too shallow of an angle. The proper fix may be to have this cone cut at a steeper angle so the leading edge of the cone is a bit lower.

DirectDrive · Feb 8, 2019

Something I've seen done is to tweek the feed lips of the magazine so the top round presents at a higher point.
Heres's one article that I remember.
Harrison of AR Performance talks about tuning 6.8 mags.
From the pics, it looks like the ramp area is out of play after the adjustments.
Recommended Mags

osprey · Feb 8, 2019

Well I got brave and chucked the barrel up in my lathe with some brass shim stock to protect finish and played around until I had very little runout. I then cut a steeper feed cone in the breech and polished it all up. It now feeds very well by hand and I expect it to do the same during live fire. I need to get a gas block for it and finish the build out and then on to live fire testing. I am hoping to get to it this weekend if I don't get snowed in.

osprey · Feb 27, 2019

Just an update on my hack machine work on this barrel. It fed three types of ammo with no hicuups during live fire with two brands of mags. It even fed mag length ballistic tip loads. I love it when things work out without costing me a pile of money. I don't think @Velzey is in any danger of me taking business away though. I would never do this on anybody elses barrel.

Freshman · Feb 27, 2019

Are you at all concerned about chamber support at this point? How does your brass look?

DirectDrive · Feb 27, 2019

osprey said:
Just an update on my hack machine work on this barrel. It fed three types of ammo with no hicuups during live fire with two brands of mags. It even fed mag length ballistic tip loads. I love it when things work out without costing me a pile of money. I don't think @Velzey is in any danger of me taking business away though. I would never do this on anybody elses barrel.

Nothin' that a good hammer and chisel can't fix.
Add style points for doing it on the kitchen table without the wife finding out.

osprey · Feb 27, 2019

Freshman said:
Are you at all concerned about chamber support at this point? How does your brass look?

I was a bit concerned but I really didn't take anymore material than another factory .308 AR barrel I had for an example. I did however examine and measure fired cases closely and can find no evidence of insufficient case support. I also checked headspace before I fired a round and all was good.

Freshman · Feb 28, 2019

Glad it worked out for you!

osprey · Feb 28, 2019

Freshman said:
Glad it worked out for you!

Yes it beats the alternative which could have been ruining an expensive barrel. I really didn't take any material where the case was supported, I just changed the cut angle on the feed cone so it ended up wider allowing tips of bullets to engage this taper.