Gunsmithing Ar10 feed cone dimensions

[flyfisherman246]

I’ve been running a 30 degree feed cone going about .030” deep on ar10 chamber ends with JP extensions. If you go much deeper you’ll be loosing case support. The problem I’m having is getting 6 creedmoors to feed with berger hybrid bullets. The elds feed just fine but that long skinny nose of the hybrid slips through the feed ramp and slams into the back of the barrel below the cone. Does anyone have a feed cone dimension that has proven to work with 6 mm hybrids and they are willing to share? I would imagine .22 creed would be even worse and want to play around with some of those in the future as well. Thanks

 

[flyfisherman246]

Just heard back from JP and they basically told me to pick a different bullet. I guess a better question would be has anyone been able to get the 6mm hybrids to feed? If so what does the feed cone look like? Also what barrel extension was used? Thanks

 

[468shot]

Just heard back from JP and they basically told me to pick a different bullet. I guess a better question would be has anyone been able to get the 6mm hybrids to feed? If so what does the feed cone look like? Also what barrel extension was used? Thanks

I can't help much yet. I just chambered a 6 creedmoor with a JP extension, I cut the feed cone at 45 degrees to .030" depth(case web still completely supported). If the bergers don't feed I don't see many other options. The tenon can't be any longer and the cone can't be any deeper.

I'm contemplating the gas port size for a rifle +3 suppressed. Thinking of trying .0625" to start with.

 

[Badmonkey]

I can't help much yet. I just chambered a 6 creedmoor with a JP extension, I cut the feed cone at 45 degrees to .030" depth(case web still completely supported). If the bergers don't feed I don't see many other options. The tenon can't be any longer and the cone can't be any deeper.

I'm contemplating the gas port size for a rifle +3 suppressed. Thinking of trying .0625" to start with.

Did this 45* feed cone allow for proper feeding? I’m having a similar problem with a .243 and 107smk

 

[468shot]

Did this 45* feed cone allow for proper feeding? I’m having a similar problem with a .243 and 107smk

It would feed, but deformed the bullet tips. I switched to a 6.5 Creedmoor.

 

[Badmonkey]

It would feed, but deformed the bullet tips. I switched to a 6.5 Creedmoor.

I tried to feed a 6.5 round with 147eld by pushing the round out of the magazine with a pen and the tip hit in the same spot. A 308 round with 168eld fed fine.

I guess I’ll work on the feed cone and if I can’t get it to stop setting back my bullets I’ll move on to 6.5creed. What feed cone geometry are you using on the 6.5?

 

[padom]

Here a pic of a Rainier Ultramatch 6.5cm on top with gold extension that had issues feeding 140gr bullets, especially 140 Hybrids. They would stab into the tenon face. You can see its got more of rounded radius and lacks a defined feed cone.

Bottom barrel is one of my custom 6.5cm Bartleins with JP QPQ honed and polished barrel extension.

This barrel has the proper feed cone for 6.5cm and feeds 140s including Berger Hybrids like butter.

 

[47chevycoe]

I had a lilja 308 barrel extension on a 260 that wouldn’t feed well at all. I ended up buying a triune precision extension and chambering a new 260 barrel that has been flawless since.

 

[JR1200W3]

I tried a JP optimized extension in a Seekins SP10 and custom barrel. It didn't work. Those gaps in the lugs are still too wide and allowed the tip of a 140 Hybrid to drop down in between them and stab the tenon. I ended up getting a large frame extension designed for 22 Creedmoor from Triune.

 

[padom]

I tried a JP optimized extension in a Seekins SP10 and custom barrel. It didn't work. Those gaps in the lugs are still too wide and allowed the tip of a 140 Hybrid to drop down in between them and stab the tenon. I ended up getting a large frame extension designed for 22 Creedmoor from Triune.

Who did the custom barrel and install the extension? There needs to be the proper feed cone as shown above along with the JP extension to feed 140's. Ive built countless 6.5cm gassers with this combo and never had one that wouldnt feed140 Hybrids 100%

I have fixed a few 6.5cm gassers done by others that would stab 140s into the back of the tenon face. I also had one from a very well known smith regularly discussed on here that stabbed 140s in the tenon and had to send back to them along with pictures of a proper feed cone to reliably feed 140 Hybrids. They made the feed cone adjustment and sent it back and then fed 140 Hybrids fine.

 

[JR1200W3]

Who did the custom barrel and install the extension? There needs to be the proper feed cone as shown above along with the JP extension to feed 140's. Ive built countless 6.5cm gassers with this combo and never had one that wouldnt feed140 Hybrids 100%

I have fixed a few 6.5cm gassers done by others that would stab 140s into the back of the tenon face. I also had one from a very well known smith regularly discussed on here that stabbed 140s in the tenon and had to send back to them along with pictures of a proper feed cone to reliably feed 140 Hybrids. They made the feed cone adjustment and sent it back and then fed 140 Hybrids fine.

A very experienced gunsmith.

I think beveling the back of the chamber(feed come) might be a band aid fix. Ideally the bullet tip is held high and away from as many parts of the feed ramp and barrel as possible so the round feeds off the body. This isn't possible on the initial feed ramp unfortunately, but at least it can be avoided on the back of the chamber. And this is all assuming the more aggressive bevel you're doing isn't removing chamber material away from the web and increasing the potential effects of the case blowing out in a less than optimal headspace situation.

Using the 22 Creedmoor extension and polishing the lug abutments, I can chamber a round and extract it and you can barely tell it's been chambered. No scratches or dents on the bullet nose or tip. I think 100% feeding and lack of tip deformation is the litmus test and our method achieved this.

 

[padom]

A very experienced gunsmith.

I think beveling the back of the chamber(feed come) might be a band aid fix. Ideally the bullet tip is held high and away from as many parts of the feed ramp and barrel as possible so the round feeds off the body. This isn't possible on the initial feed ramp unfortunately, but at least it can be avoided on the back of the chamber. And this is all assuming the more aggressive bevel you're doing isn't removing chamber material away from the web and increasing the potential effects of the case blowing out in a less than optimal headspace situation.

Using the 22 Creedmoor extension and polishing the lug abutments, I can chamber a round and extract it and you can barely tell it's been chambered. No scratches or dents on the bullet nose or tip. I think 100% feeding and lack of tip deformation is the litmus test and our method achieved this.

No chamber or headspace issues on any of mine. My brass has tons of reloads on them with nothing more than a Forster FL sizing die. Agreed my litmus test for a properly built and tuned large from 6.5cm gasser is brass and bullets that look like they were fired in a bolt gun. No dents/ gouges on the the shoulder or bullet, no 2 drag lines on the neck. No raised burs and brass flow on the case head.

 

[JR1200W3]

No chamber or headspace issues on any of mine. My brass has tons of reloads on them with nothing more than a Forster FL sizing die. Agreed my litmus test for a properly built and tuned large from 6.5cm gasser is brass and bullets that look like they were fired in a bolt gun. No dents/ gouges on the the shoulder or bullet, no 2 drag lines on the neck. No raised burs and brass flow on the case head.

I should also mention that when we experienced the malfunctions with it, the bullet tips were low enough down on the breech face that a bevel wouldn't have helped. And it wasn't a situation of 1 out of 10 rounds wouldn't feed right. It wouldn't feed a single one.

 

[padom]

I should also mention that when we experienced the malfunctions with it, the bullet tips were low enough down on the breech face that a bevel wouldn't have helped. And it wasn't a situation of 1 out of 10 rounds wouldn't feed right. It wouldn't feed a single one.

Thats weird. And you think thats a product of the JP extension? Or the upper receiver you were using or what?

Ive had both Keystone and PVA build countless for me with that JP QPQ extension and none have that issue. Most on MEGA billet uppers and a few on Aero uppers. Im running one right now, MEGA billet upper, Bartlein from PVA with the JP QPQ extension +2 Gas, feeds and shoots 140 Hybrids 100% like a swiss watch.

 

[Badmonkey]

A very experienced gunsmith.

I think beveling the back of the chamber(feed come) might be a band aid fix. Ideally the bullet tip is held high and away from as many parts of the feed ramp and barrel as possible so the round feeds off the body. This isn't possible on the initial feed ramp unfortunately, but at least it can be avoided on the back of the chamber. And this is all assuming the more aggressive bevel you're doing isn't removing chamber material away from the web and increasing the potential effects of the case blowing out in a less than optimal headspace situation.

Using the 22 Creedmoor extension and polishing the lug abutments, I can chamber a round and extract it and you can barely tell it's been chambered. No scratches or dents on the bullet nose or tip. I think 100% feeding and lack of tip deformation is the litmus test and our method achieved this.

Are you using the 22 creedmoor extention on 6.5 and 6mm applications as well, or just .22 CM?

 

[JR1200W3]

Are you using the 22 creedmoor extention on 6.5 and 6mm applications as well, or just .22 CM?

Specifically and exclusively 6.5CM 140 Hybrids

 

[Badmonkey]

Specifically and exclusively 6.5CM 140 Hybrids

Thank you. Just wanted to make sure the smaller ramps wouldn't cause a problem for a larger caliber bullet. That might be the answer for my next 6mm barrel. I'm limited to playing with the feed cone on the current one.

 

[Badmonkey]

Here's what I'm dealing with. You can see where the meplat slams into the edge of the feed cone. The bullet slips right through the ramps and doesn't raise the round up at all. It will chamber and cycle. It shoot's mostly sub MOA somehow also, even knocking the bullets all the way back into the case. But it has a tendency to throw flyers as much as 2" out of a 3/4" group.

 

[JR1200W3]

Here's what I'm dealing with. You can see where the meplat slams into the edge of the feed cone. The bullet slips right through the ramps and doesn't raise the round up at all. It will chamber and cycle. It shoot's mostly sub MOA somehow also, even knocking the bullets all the way back into the case. But it has a tendency to throw flyers as much as 2" out of a 3/4" group.

View attachment 8764769

Yep. If you're relying on a feed cone that's a pretty small difference between GTG and smashing bullet tips. It would be better to have more room for error as it feeds because left and right sides probably feed differently. I would go with a new barrel extension. I actually went through two of them and tried 4 total. My Smith had to push the shoulder back on the tenon to clock the new extension and then push the chamber commensurately deeper.

 

[Badmonkey]

Well, this is a cheapo, off the rack barrel I threw on an upper to see if I’d like shooting 6mm out of a large framed AR for PRS style matches. I do like it, but the feed issues were worrying me. Seeing that there is a fix available I won’t have a problem coughing up the money to have a good barrel spun up. I just don’t want to spend money on a “good” custom barrel that has the same problems as my budget barrel.

 

[JR1200W3]

Well, this is a cheapo, off the rack barrel I threw on an upper to see if I’d like shooting 6mm out of a large framed AR for PRS style matches. I do like it, but the feed issues were worrying me. Seeing that there is a fix available I won’t have a problem coughing up the money to have a good barrel spun up. I just don’t want to spend money on a “good” custom barrel that has the same problems as my budget barrel.

This is why I use a smith that is local to me. I would call him a friend. He's done barrels for me for about 9 years. I can walk into his shop with a project and we can talk about it and generate ideas to solve potential problems. It's really hard to get that level of investment from a mail order guy, regardless of if he's using Bartleins or not. It took us about 2 months to get my barrel finished. Gas block journal was cut to be an almost thermal, friction fit. Gas port was drilled to function with my complete build. Contour was custom. We had to wait for 3 orders of barrel extensions, sequentially. I paid him 33% more than his normal price because he had a lot of hours into it. If I'm serious about accuracy in a gas gun anymore these days, it's getting a custom barrel. It's just the only way to do it. It's amazing how infrequently you get a real shooter from off the shelf AR barrels. Bolt gun barrels are way more forgiving. I've got McGowen blanks that shoot fantastic. In fact I've never had one that didn't. But, I don't think you can take those types of risks in a large frame gasser. The room for error just seems to be too small in them.