AR10 FTFeed, FTE

Dale264

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Ive got a pieced together AR10, all Aero Precision M5 parts. This AR10 is a bit different as it is chambered in .45 Raptor. For those unfamiliar with that cartridge its a 460 S&W Mag with a rimless case. The barrel allows for an OAL of 2.35"+ and I'm using a custom mag from Scott Medesha at 45Raptor.com.

I am having issues with the bolt lugs digging into the brass of the next case in the mag to the point where it stops the bolt from closing (videos included). Im open to any suggestions. I have attached a couple slo-mo clips of the bolt closing and an image of the mag with a round showing the marring from the bolt lugs.

Im open to any suggestions on how to fix this.

Mag.jpg
.
 
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IowaGeologist

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Too much mag spring? Is the first round riding up too high in the mag to begin with letting the round below it to ride high?
 
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Dale264

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Thanks for offering little to no help in the form of additional questions.

Agreed the mag spring was too heavy. I have take the mag spring down to half it's original length and it's far better now but it's still not great. I'd like this rig to function better than 95% and it's still not in that ball park. 1 round feeding is iffy. It still seems to get a little hung up.
 

papershredder

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I wouldn't say he's offering little help. The experts here will need a lot more info. I'm by no means an AR guru, but it does look like it's trying to double feed and the top front of the magazine is showing a decent amount of wear. It could be rounds are high up in the mag or the magazine itself maybe too high up in the receiver or cocked. Try other magazines and see if the problem repeats itself. I would also double check gas tube/gas key alignment with the way your bolt is coming to a dead stop like that, in that particular spot in it's travel. Mark up some rounds with dykem and see what marks (other than the big gouge) are being left behind on the brass also, that could give everyone here a lot more info as well.
 

MPD142

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Looks like multiple issues. What does it do if you just toss a round in the ejection port with an empty mag and send the bolt home? Does this only happen when feeding off the left side of the mag or will it do it on both sides?

Watching the video you can see the same time the bolt is stopping the next round in the mag is being pushed forward and up. This could be contributing to your issue. How does the carrier fit in the upper? Looks like it may be almost a reverse carrier tilt or perhaps a carrier lift where the round is forcing the carrier up and the gas key could be hitting on the gas tube and also binding the carrier in the upper. I would look to see if there are any witness marks on both to see if they have been contacting each other.

What happens if you remove the mag when the bolt is stuck? Will it slam home or is it stuck in place?
 

Dale264

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the top front of the magazine is showing a decent amount of wear.
This is a brand new modified mag. Those wear marks are from the maker's hand fitting process.

It could be rounds are high up in the mag or the magazine itself maybe too high up in the receiver or cocked. Try other magazines and see if the problem repeats itself.
I've tried several other mags and none feed better than this. These wildcat straight wall cartridges are tough to tune.
I would also double check gas tube/gas key alignment with the way your bolt is coming to a dead stop like that, in that particular spot in it's travel.
Its not making contact with the gas tube.
 

Dale264

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Looks like multiple issues. What does it do if you just toss a round in the ejection port with an empty mag and send the bolt home?
The round feeds properly.
Does this only happen when feeding off the left side of the mag or will it do it on both sides?
It's more common to have an ftf off the left side of the mag but is too inconsistent to determine a clear pattern.
Watching the video you can see the same time the bolt is stopping the next round in the mag is being pushed forward and up. This could be contributing to your issue.
I removed several coils from the mag spring and it helped this issue substantially but there is still a bit of a catch in the bolt.
How does the carrier fit in the upper? Looks like it may be almost a reverse carrier tilt or perhaps a carrier lift where the round is forcing the carrier up and the gas key could be hitting on the gas tube and also binding the carrier in the
Everything is very snug in this setup so there isn't any play. The bcg doesn't contact the gas tube.

What happens if you remove the mag when the bolt is stuck? Will it slam home or is it stuck in place?

There are many occasions where the bolt has the round wedged in the extension/opening of the chamber. But in the case of that video clip the round chambered after dropping the mag.
 
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celltech

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Looking at both the single feed video, and the attempted full mag feed, it seems like the bolt is catching/pausing/stopping at the same point? Do those rounds need a smidge of taper crimp to help them into the chamber? And that bolt looks pretty dry...any help when lubed up?
 
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papershredder

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After watching the 2nd vid (didn't realize there were two) with the single round mag feed and comparing it to the first, it's looking like the issue is with that feed lip in the magazine. It looks to me like that feed lip in the mag might be a little low causing the double feed and also not angled properly for a smooth feed into the chamber. Whether the angle is too steep or not steep enough, I can't really tell from the vids, but try this: Put one round in the mag and install mag with bolt closed, pull back charging handle and slowly allow bolt to move forward while still holding onto the charging handle. See if you can get a round to jam in the chamber and if so, show everybody here a picture of the jam.
 

Dale264

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Looking at both the single feed video, and the attempted full mag feed, it seems like the bolt is catching/pausing/stopping at the same point? Do those rounds need a smidge of taper crimp to help them into the chamber? And that bolt looks pretty dry...any help when lubed up?
This could be it. I'm starting with Virgin starline and it has a pretty thick case wall and a sharp lip on it. However, being a straightwall cartridge I can't go too wild since that is how the cartridge headspaces.
 

Dale264

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After watching the 2nd vid (didn't realize there were two) with the single round mag feed and comparing it to the first, it's looking like the issue is with that feed lip in the magazine. It looks to me like that feed lip in the mag might be a little low causing the double feed and also not angled properly for a smooth feed into the chamber. Whether the angle is too steep or not steep enough, I can't really tell from the vids, but try this: Put one round in the mag and install mag with bolt closed, pull back charging handle and slowly allow bolt to move forward while still holding onto the charging handle. See if you can get a round to jam in the chamber and if so, show everybody here a picture of the jam.

20210715_190132.jpg
20210715_190328.jpg
 

msgriff

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I know that you said that it's all Aero parts, but that mag release button doesn't look Aero. Is the mag catch Aero? If not, is there a possibility that the mag is seated too deep in the well.
 
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kvpm

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I don’t recall any of your posts mentioning you’ve reached out to 45raptor.com for advice. You might start there.

You listed a COAL of 2.35”+. The cartridge drawing on 45raptor.com website shows 2.30”. Possibly seating bullets too long.

Maybe try bullets with different shape. They might have a tendency to feed better.
 

Earnhardt

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Barrel Length?
Gas system?
Buffer weight?
BCG brand/weight/double ejector?
What brand/weight buffer spring is it?
Have you tried any FTX/polymer tip style bullets?
Have you tried a modified 10 round P-Mag?
 

bfoosh006

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    Always wanted a .45 Raptor... but haven't gotten there yet.

    Just a few suggestions, polish the front of the bolt face smooth so the feeding case head can "glide" easily across it.

    I would attempt to crimp a little more.... or make sure any outside lip, from trimming is gone.

    Make sure the chamber is smoothly finished. Polish if needed. Again allowing the bullet as easy feeding as practical.


    As for your at hand issue, I would think the magazines passenger side front'ish portion of the feed lip needs to be slightly lower for your rifles dimensions. Or the mag needs to be slightly lower in the locked in postion, in the magwell. ( Your build is probably slightly different, dimension-ally, then the rifle Scott Medusha's used to produce the mag.... and the whole no Mil-Spec Guideline for Large Frame AR's )

    Before you start bending the passenger side feed lip... maybe the mag catch could be altered to allow a slightly lower "lock in" with the mag.

    Judging by the scrape mark... it might not need much.

    IE, get a spare mag catch and file some off the top of the actual catch contact point.

    I have no idea if this would work well.... so think it through be for diving in.... but to me the stack of rounds , in the mag, needs to be slightly lower.

    Also.. since poop happens... make sure the bolt lug that is making contact with the case doesn't have a burr or something wonky going on.

    And when your issue is fixed... I sure would like to know your impressions of the .45 Raptor.
     

    357Max

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    If it was mine I'd pull that damn aluminum block out from the front of the mag, flip it over square side up, & star over with the ramps.
    Start with your barrel extension and work your way back.

    Before spending any time on the mag. I'd check to see how much they shortened the feed lips compared to a stock mag? If to short then I'd throw it in the trash.

    Capture below shows the round that's feeding is going in with the nose about .150 (guessing) higher then the barrel extension feed ramp (visible in front of aluminum mag block. The only chance in hell to make the steeper approach angle work would be to shorten the feed lips (I suspect they are). Shortening the feed lips a little can help, but if shortened to much it will contribute to this problem Yugly.
    There is a ramp on the under side of the carrier just behind bolt & it's purpose is to push down the round below. As you shorten the feed lips, it allows the round below to pop up sooner before the carrier ramp has engaged it. As a result the carrier tries to drag the lower round forward.
    1626414796616.png


    The capture below shows the bolt still in motion, but dragging the lower round forward. The ramp in the aluminum block is to steep & extends to low allowing the lower round to start riding up the ramp. In essence your large frame has a wedgie.
    1626414927889.png


    Feed lips look like they've been shortened considerably.
    1626416453873.png


    My take on the mag is that whoever made it was trying to make something that would work with a stock unmodified barrel extension.

    For these straight walled AR cartridges the barrel extensions need work. Below is before and after on a 350 Legend barrel. Basically the small frame version of the raptor.
    IMG_5891-1.jpg
    350L X caliber.jpg
     
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    Dale264

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    I don’t recall any of your posts mentioning you’ve reached out to 45raptor.com for advice. You might start there.
    This is going to be my next step if everyone's suggestions don't help improve the situation.
    You listed a COAL of 2.35”+. The cartridge drawing on 45raptor.com website shows 2.30”. Possibly seating bullets too long.
    Space in the mags measures 2.360ish
    Maybe try bullets with different shape. They might have a tendency to feed better.
    I'll be looking into different bullets. So far I have only tried the 245gr .452 SP and 250gr .452 FTX from hornady.
     

    Dale264

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    Barrel Length? 18" Mcgowen
    Gas system? MID
    Buffer weight? Standard?? This is my buddies rifle.
    BCG brand/weight/double ejector? AERO, standard? Single
    What brand/weight buffer spring is it? Aero
    Have you tried any FTX/polymer tip style bullets? Yes
    Have you tried a modified 10 round P-Mag? Loaded longer and current length resulted is even worse feeding with a pmag
     

    Dale264

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    And when your issue is fixed... I sure would like to know your impressions of the .45 Raptor.
    I'll give your suggestions a try. From some other stuff I've read feed lips need to be messed with some.
    As for first impressions, I've single fed about 25 rounds through the gun tinkering with load development and its surprisingly accurate (3shots <1.5") and the power is insane compared to something like a 350 legend. Load data is tough to come by and I had some issues with 100% of the rounds ejecting but that's a problem for another day. An adjustable gas block will likely take care of that. If I can get this thing functioning 100% I'd say it's a great cartridge. So far thats yet to be seen.
     
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    Dale264

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    If it was mine I'd pull that damn aluminum block out from the front of the mag, flip it over square side up, & star over with the ramps.
    Start with your barrel extension and work your way back.

    Before spending any time on the mag. I'd check to see how much they shortened the feed lips compared to a stock mag? If to short then I'd throw it in the trash.

    Capture below shows the round that's feeding is going in with the nose about .150 (guessing) higher then the barrel extension feed ramp (visible in front of aluminum mag block. The only chance in hell to make the steeper approach angle work would be to shorten the feed lips (I suspect they are). Shortening the feed lips a little can help, but if shortened to much it will contribute to this problem Yugly.
    There is a ramp on the under side of the carrier just behind bolt & it's purpose is to push down the round below. As you shorten the feed lips, it allows the round below to pop up sooner before the carrier ramp has engaged it. As a result the carrier tries to drag the lower round forward.

    The capture below shows the bolt still in motion, but dragging the lower round forward. The ramp in the aluminum block is to steep & extends to low allowing the lower round to start riding up the ramp. In essence your large frame has a wedgie.

    Feed lips look like they've been shortened.
    The feed lips have been shortened but I couldn't tell you how how much since I don't have a metal mag to compare it to. You make a good point about the round feeding is too high. I'll be calling the maker for some info/tips since he seems to be a big source on this cartridge in ARs.
     

    Earnhardt

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    EVERY person I know who has used a mid-length gas system, and/or the mag set up you are currently using has problems with the 45 Raptor
     

    Earnhardt

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    My build
    Xanthos Upper/Lower
    24" barrel
    Rifle gas system
    SLR AGB
    9 oz buffer
    Tubbs Flat Wire
    Standard weight BCG
    Double Ejector bolt with small firing pin (.065")
    Modified P-Mag
    COAL 2.62" used in full length standard P-Mag without a spacer in front of the bullets

    Smooth as butter...but it took me a long time to get there

    Since you are stuck with the mid-length gas system, you will NOT be able to reload the 45 Raptor to its full potential
    The best example I can give you is this...look online and find some reload stats for guys who are using the 45 Raptor in bolt action guns and compare those results to what we are getting with the AR-10's...
    Yes, I know the AR's will not compete with the bolt guns in performace, but they should be able to come somewhat close right?..
    Well not with that mid-length gas system
     
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    Dale264

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    Since you are stuck with the mid-length gas system, you will NOT be able to reload the 45 Raptor to its full potential.
    Why do you say that? I had decent success (accuracy) with 45gr lilgun and 250 ftx. This was built for iowa whitetail so I don't necessarily need it to drop a t-rex.
    The best example I can give you is this...look online and find some reload stats for guys who are using the 45 Raptor in bolt action guns and compare those results to what we are getting with the AR-10's...
    Yes, I know the AR's will not compete with the bolt guns in performace, but they should be able to come somewhat close right?..
    Well not with that mid-length gas system
    EVERY person I know who has used a mid-length gas system, and/or the mag set up you are currently using has problems with the 45 Raptor
    Well shit... hahaha
    What bullet are you loading with?
     

    Earnhardt

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    Accuracy is one thing. But reliability and a fully operating gun is another. If your AR isn’t running like it is supposed to, you might as well just build a bolt action 45 raptor
     
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    IowaGeologist

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    This was built for iowa whitetail so I don't necessarily need it to drop a t-rex.
    Dang, after all the deer I've seen taken with a 350 Legend or 450 Bushmaster I'm curious why you thought you needed a large frame 45 Raptor for Iowa whitetail?

    Thing has to almost blow a softball sized hole out of them within 100 yards, which is about where you're taking 90% of your shots in Iowa from.
     

    Dale264

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    Dang, after all the deer I've seen taken with a 350 Legend or 450 Bushmaster I'm curious why you thought you needed a large frame 45 Raptor for Iowa whitetail?

    Thing has to almost blow a softball sized hole out of them within 100 yards, which is about where you're taking 90% of your shots in Iowa from.
    It's fun to be esoteric when things work well. It's currently biting me in the rear.
     

    Dale264

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    Update: fiddled with spring length and orientation in the magazine, increased OAL to max allowable length for mag, and crimped the cases.

    Now it feeds 4 of 4 when manually dropping the bolt. On to the range to work on ejection now.
     
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    Dale264

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    Update: Recent range trip resulted in reliable 3 round strings of fire. Unfortunately this midlength barrel is over gassed so an adjustable gas block is on its way. The majority of the rounds ended up near the 1 o'clock position and had some brass swelling indicating premature unlock. A heavy buffer will be on order if the gas block doesn't sort things out.
     
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    Earnhardt

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    How do the case rims look?
    Are they bent or chewed up?

    Are the empty cases covered with soot?