SP10 6CM feeding issues

Have you tried a different magazine?

Is the bolt completely behind the round? Can't tell from the picture. Looks almost like it's short stroking a bit and riding the next round into the barrel too low.

Possibly the opposite as well, too much gas.

Leo. D said:

I have not. Just used 20rnd Pmag I got with the gun. All SR25 compatible magazines would work?

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Yeah it should be. If you have a mag where you can adjust the feel lips, try adjusting to where the tip of the bullet is pointed up a bit.

It's probably the magazine.

I built a 243 for coyote hunting and anything from 87 to 58 grain feeds no problem. If I load 107 RDF the long bullet slides through the feed ramps and jams in the barrel like that. 100 gr. Soft points feed 99% of the time probably from the rounded nose. If they made a barrel extension with narrower feed ramps would take care of it or a magazine that kicks the nose up would help to.

This is gonna hurt your wallet, but look for a kac or LaRue mag if you can swing it. The D&H isn't as good obvioulsy, but it should alleviate the feed issues.

The way the LR magpul mags tend to feed, they don't control the release of the round very well.

If you slow feed a couple of the "problem" rounds using a pmag(hand on charging handle), watch for the round to pop up or slightly to the side, and follow it forward. If it pops up out of the lips funny you will see it.

In your last photo... where it shows the bullet tip stopped against the breach.

I would suggest polishing that radius on the barrels receiver extension.

I have used a over sized shotgun bore mop ( over sized enough that it won't go into the chamber, but rides the area I am talking about ), attached to a piece of cleaning rod, spun via a cordless drill.

You WILL need a shotgun adapter for the mop... I tend to buy a cheap universal Hoppes cleaning kit that has the adapter.

IMPORTANT >>>>>MAKE SURE you blow out the fuzz from abusing / polishing with the bore mop, from the lug area.... that fuzz can lock up the bolt , into the RE lugs pretty danged tight if it isn't removed .... ( ask me how I know )

Frankly if it’s stock from Seekins. They’ll take it back and diagnose/repair-replace. That’s the easy button. You don’t want to be buying KAC mags and shit. You want it to run whatever I’d think.they’ll have you mail some of that ammo and the mag too

Leo. D said:

Yeah I will call them and see if I can send it in to get it fixed.

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Email will be quicker. They never answer unless you have an extension.
[email protected]

I believe the problem is the barrel extension. It appears that it was machined for a larger caliber like .308. The longer VLD style bullets aren't even contacting the barrel extension and simply running into the barrel. The shorter bullets actually make contact with the barrel extension before the tip hits the barrel and funnels them into the chamber. The manufacture needs to correct this.

B y r o n said:

I believe the problem is the barrel extension. It appears that it was machined for a larger caliber like .308. The longer VLD style bullets aren't even contacting the barrel extension and simply running into the barrel. The shorter bullets actually make contact with the barrel extension before the tip hits the barrel and funnels them into the chamber. The manufacture needs to correct this.

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Is the bullet supposed to hit the barrel extension or is the brass supposed to ride the feed ramps?

Isn't the creedmore case the same case diameter as the 308?

Shouldn't the brass riding up the feedramp be what's disengaging the round from the magazine, or should the magazine just let go of the round at a random point?

Leo. D said:

Yeah I will call them and see if I can send it in to get it fixed.

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I would suggest trying a better magazine first. If you ordered the D&H mags try those.

db2000 said:

SOLD - Knights SR25 20rd mags

I have a some 20rd Knights SR25 mags, that I don’t have a use for anymore. The used mags are lightly used less than 200rds through the set of 5. I WILL NOT ship to anywhere with mag restrictions, so do NOT message me if you live in one of those places. 5 used Knights mags - SOLD 5 new Knights...

www.snipershide.com

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I don't know why you find this funny. That's actually a good price for KAC, which BTW, I haven't seen any new for sale in forever. Larue are now 90 or so up from 60 something.

mettee said:

Is the bullet supposed to hit the barrel extension or is the brass supposed to ride the feed ramps?

Isn't the creedmore case the same case diameter as the 308?

Shouldn't the brass riding up the feedramp be what's disengaging the round from the magazine, or should the magazine just let go of the round at a random point?

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First question - The barrel extension is supposed to guide the round into the chamber. As you can see in you first picture the bullet is jammed into the barrel before the case even got to the extension. If the feed ramps of the extension were narrower they would have touched the bullet and assisted with guiding the round into the chamber.

Second question - You'd have to look a case dimension drawings because I don't remember all the dimensions but this has nothing to do with your problem.

Third question - The round will disengage from the magazine when the rim clears the feed lips of the magazine. Not random but the lips determine when.

The problem is 6mm, especially VLDs.

The AR-10 barrel extensions were never designed for 6mm bullet diameter and ogive, especially VLDs.

Because the 6mm is so narrow, it allows the meplat to smash into the breech without even hitting the feeding cone.

There are several geometries to take into consideration with a new cartridge design for feeding.

* The upper receiver extended feed ramps
* The barrel extension feed ramps and angles
* The feeding cone in the breech

These first 3 sets of surfaces all act as ramps and a cone to help get the meplat into the chamber. The existing AR-10 upper, barrel extension feed ramps, and feeding cone are all designed and spec’d for .308 Winchester/7.62x51.

Next:

The magazine feed lips need to control the cartridge orientation for initial feed angle relative to the upper extended feed ramps, barrel extension, and the feeding cone.

7mm-08, .260 Rem, 6.5 Creedmoor, and 6.5x47 Lapua work with most bullets because the diameters are larger and place the meplat higher relative to the feeding cone in the breech.

With .260 Remington, a lot of guys who chambered for it back in the 2000s found that Berger VLDs would have similar feeding problems getting smashed or sheared on the breech or feeding cone.

I lucked out and didn’t have that problem on mine with 130gr regular VLDs in .260 Rem, but I was already anticipating it since others had warned me about it.

When you step down to 6mm and want to shoot VLDs, it kinda requires a total feed system design approach with specific components shaped to place the meplats into the chamber and not hit the breech.

One thing I would consider is blending and polishing these surfaces:



See how your upper receiver and barrel extension feed ramps don’t blend together? I think your case shoulder may be hitting the little feed ramp cut into the upper and nosing down a bit. I’m not saying blending and polishing your ramps will solve the 6mm problem but I don’t like to see disrupted surfaces like that.

In my .260 Rem that GAP built for me, those surfaces are blended. I have never had a feeding issue with the rifle. It has run like a raped ape and shoots bug holes right along with some of the best bolt guns I’ve shot.

Buddy shoots a 22 creed, that feeds just fine. Why does that happen?

B y r o n said:

First question - The barrel extension is supposed to guide the round into the chamber. As you can see in you first picture the bullet is jammed into the barrel before the case even got to the extension. If the feed ramps of the extension were narrower they would have touched the bullet and assisted with guiding the round into the chamber.

Second question - You'd have to look a case dimension drawings because I don't remember all the dimensions but this has nothing to do with your problem.

Third question - The round will disengage from the magazine when the rim clears the feed lips of the magazine. Not random but the lips determine when.

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The question I still have is...is the feed lip supposed to contact the bullet or the brass? Does it guide via the bullet, or the brass case? Is it both? I can see how the bullet would make some contact momentarily.

So if the mag feed lips are plastic and the spring is loose, and the mags letting go of the round early, the case would pop up funny and not follow the feed lips and it would maybe poke into the inside of the extension instead of entering the chamber?

This is a well know problem with 6mm AR10's. The barrel extension was designed for 308 and the small diameter 6mm doesn't always allow the tip of the bullet to present directly into the chamber. It is made worse with long skinny bullets. Varmint bullets are shorter with the ogive close to the tip so they tend to work better. Add in magazine and magazine location variation, and you get feedway stoppages.

Try some ELDM if you haven't already. They feed easier than VLD.

Mike_in_FL said:

I don't know why you find this funny. That's actually a good price for KAC, which BTW, I haven't seen any new for sale in forever. Larue are now 90 or so up from 60 something.

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It’s funny because it’s being suggested he should buy $500 magazines to fix an issue with a rifle he already spent $2200+ for. Good deal or not, that’s a retarded idea IMO when Seekins will just make it right for free and he can run whatever the hell he wants with it.

db2000 said:

It’s funny because it’s being suggested he should buy $500 magazines to fix an issue with a rifle he already spent $2200+ for. Good deal or not, that’s a retarded idea IMO when Seekins will just make it right for free and he can run whatever the hell he wants with it.

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Thanks for the clarification. I agree about that. You can't purchase magazines hoping it changes the angle of entry into ramps that seem to be too big.

I don't know for sure, but I've got to believe they're not cut when the barrel extension is purchased. Seems like someone at Seekins was having a Monday morning and cut it for 6.5 or .308 rather than 6mm.

mettee said:

Buddy shoots a 22 creed, that feeds just fine. Why does that happen?

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Shorter COL doesn’t allow the meplats to smash the breech.

The shoulder lifts the meplat into alignment with the chamber before it has a chance to touch the breech.

22, 6mm, 6.5mm

Leo. D said:

Hornady elds have worked with no issues.

I'm just wandering what is seekins going to do about this because I know I'm probably not the only one with a feeding issue on an SP10/ar10 6 CM. What are some known solutions for diys and manufacturer solutions?

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Known solutions are using bullets that aren't VLDs and shortening the COAL. DTACs have a more friendly ogive location too. You can try different magazines but there's no guarantee they will work since it isn't specifically a magazine issue. Lancer mags are worth a try, they have metal feedlips and should present the cartridge higher than a pmag.

I was just going to suggest trying Lancer mags, but I really would have that double feed ramp mess cleaned up and blended. It makes me itchy just looking at it.

LRRPF52 said:

Shorter COL doesn’t allow the meplats to smash the breech.

The shoulder lifts the meplat into alignment with the chamber before it has a chance to touch the breech.

22, 6mm, 6.5CM

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Okay that makes better sense, I couldn't see the dimensional difference in my head.

LRRPF52 said:

I was just going to suggest trying Lancer mags, but I really would have that double feed ramp mess cleaned up and blended. It makes me itchy just looking at it.

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I can see the issue better now that you showed the dimension differences, thanks for that. You can see how if it was a 308 being loaded it would miss the breach face due to being higher.

Correct to say that the ramp should have been left higher so it lifted the round more?

Leo. D said:

I'll try this as well.

Does anyone know if this a seekins issue and I have to send this back? With the cost of this gun, I should be able to take any 6CM ammo and fire this thing. I just bought this like a couple weeks ago brand new.

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I have done it to a few different brand .308 / 6.5CM barrels, so I wouldn't say a Seekins issue.

My feeble mind tends to think it is tolerance stacking ... between the mag catch, the mags themselves, slight upper to lower differences... etc

Is your upper receiver cracked? Either debris or I see a hairline fracture. M4 feedramps would definitely help. I've transitioned to Lancer L7AWM mags. I've had problems with the magpuls properly presenting the round for feeding.

mettee said:

I can see the issue better now that you showed the dimension differences, thanks for that. You can see how if it was a 308 being loaded it would miss the breach face due to being higher.

Correct to say that the ramp should have been left higher so it lifted the round more?

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The ramps should blend and look like one seamless ramp between the upper receiver and barrel extension.

A slightly higher ramp might help feed the VLDs loaded to a long COL, but it’s a bit late for that.

LRRPF52 said:

Shorter COL doesn’t allow the meplats to smash the breech.

The shoulder lifts the meplat into alignment with the chamber before it has a chance to touch the breech.

22, 6mm, 6.5CM

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Pretty sure those are x47 cases. But your point is still valid. I'm done. Carry on. Learning a lot in this thread.

Looks like the taper on the breech is not machined right. I had same issue with another brand. Look at pictures of others and compare. Yours looks too flat. I went round and round arguing and ended up sending it back... went with different brand, changed nothing else, and the gun cycles flawless now and no more locking up trying to chamber like yours is.

surgeon260 said:

Pretty sure those are x47 cases. But your point is still valid. I'm done. Carry on. Learning a lot in this thread.

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I was going to challenge that but I think you might be right. I was looking for a photo that showed the difference between the common COLs for .224, 6mm, and 6.5mm and that one seemed to illustrate it well since .224 bullets don’t have the ogive length of the 6mm and 6.5mm tips.

A buddy of mine who is an OCD engineer who put himself through 2 different gunsmithing programs during and after his engineering degree at Cal Tech did some interesting work when he was playing with .260 Rem in ArmaLite AR-10s. He cleaned up the feed ramps and also added secondary feed ramps to the feeding cone, taking case web support into account to know how far he could go. I think it was Berger VLDs that drove him to do that.

He does a lot of feed work on other cartridges he loads for in bolt guns, chasing max COL and optimum shank placement relative to the Shoulder-Neck Junction. Great shooter and machinist who learned problem-solving on his own as a kid making home-made air guns and other engineering projects.

I would try Lancer mags first. I have seen some really nice billet AR-10s with top-shelf components all-around not feed from 7.62 PMAGs, then as soon as we tried Lancers, they ran fine.

Magpul went through a series of iterations and generations with the 7.62x51 PMAGs, so things changed along the way. My .260 Rem built by GAP runs on the 1st Gen 7.62 PMAGs like a raped ape.

For your 6mm with VLDs loaded long, you’re going to need feed lips that angle higher towards the open chamber, like what the Army did with M855A1 and Gen 3 PMAGs.

If Lancers don’t work, It would be easy to change the internal angle of feed lips on PMAGs since there is more meat there, rather than trying to bend feed lips on metal mags.

I would try making a mandrel wrapped in fine grit sandpaper, then spin it in a drill to adjust the feed lip angle inside a PMAG until you get the long COL VLDs to point into the chamber, skipping the feeding cone entirely.

I would also de-edge, blend, and polish the feed ramps so that no large scratches and gouges happen during feeding.

Now that I see the issue better, that extension is the problem. No matter what you do it won't be reliable like that. Gonna have to send it to seekins for a new barrel or to replace the extension.

Leo. D said:

The way I'm approaching this is that if I pay a premium for a gun I should be able to run any ammo with any mag obviously of the same caliber without any feeding issues. If a manufacturer sells guns they need to test it with different ammo and ensure it will work function with it otherwise state it when purchasing the gun that it would only work with xyz. It's not like I'm building a custom gun. This is a stock gun from Seekins.

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I feel you on that. Even with what I knew 15 years ago, when I had GAP build my .308 and .260 Rem, they asked me, “What bullet do you really want to shoot?” For the .308, it was 155gr Scenar, and for the .260 Rem, it was 139gr Scenar.

Both of them are hummers with those loads and some others. The .260 Rem shoots pretty much everything superbly. The “worst" bullet I tried in it was 140gr A-MAX, which shot .75” 5rd groups. At the time, my unrealistic expectations were that everything should shoot 1/2”, but even then, I knew that certain bullets might not feed correctly, especially the Berger VLDs.

To my pleasant surprise, 130gr VLDs run fine through my .260 Rem gasser and shoot bug holes at 100yds, group really tight at 1000yds. But I would not have complained if they didn’t feed because it was a known issue for many who had tried loading VLDs in AR-10s.

One thing you can do to help Seekins set the gun up for you is send them your long COL 6mm Creedmoor VLD loads, and they should be able to work the critical parts so that they will feed that load reliably.

You’re basically asking for a McLaren that will run on racing fuel, low-price unleaded, special, and premium fuels. It can be done with 3 of those, but it will take some tuning.

Dummy cartridges would work well for manual-feeding and troubleshooting, followed by live fire if they do all that.