Model 10 feed issues for long 77gr HP

[Idaho]

I have a Model 10 in .223 with an 8 twist McGowan barrel so that I can shoot heavier bullets for long range chucks. When I load 75 gr A-Max to magazine length they slip right into the chamber with no problem. I've been trying to chase the lands with 77gr Nosler CC HPBT and can't get them to feed unless they are seated deep. From the ogive of the bullet they are over 1/10 inch from the lands. By loading a bullet slowly from the magazine the meplat of the Nosler catches on the very bottom edge of the chamber before the case shoulder touches the feed ramp. Research tells me that tweaking on the magazine ears is a looser. I'm wondering if a couple of small dobs of epoxy on the face of the ramp to effectively move it back just a bit might work. That way the case shoulder could ride up slightly to allow the nose of the bullet to lift into the chamber.

Any ideas?

[Idaho]

This must be a tough question. I see there are lots of complaints from others on here and other sites about this very issue. I'm going to try to put a couple of dabs of JB Weld on the leading edge of the feed ramp below where the bolt must slide across to see what happens. I can always polish it off with a Dremel tool if it does not work.

[sharpshooter]

The best fix is to cut a feed cone on the chamber mouth the same as an AR-15.

[Robinhood]

There are many of us who have experienced this specifically with McGowan 223 chambered barrels. Following freds instructions above fixed it for me.

[Idaho]

That's what I wanted to know. I assume that the barrel needs to be removed to make that happen and then done by a gunsmith. Also, does that cause the brass to weaken right where the cone is cut or is it so small that it's not an issue?

[Robinhood]

It has not effected my brass.

[Idaho]

It has not effected my brass.

Good to know, thanks

[RustyShackle]

Doesn’t this(machine work) defeat the purpose of a switch barrel rifle?

[Idaho]

Doesn’t this(machine work) defeat the purpose of a switch barrel rifle?

No. The notch that they mention is actually at the very bottom edge of the chamber that is part of the barrel. My understanding is that it need not be very big, a small radius actually.

[Idaho]

I've decided to order a Single shot DBM adapter from Sharp Shooter Supply. That will allow me to test load length before I get too excited about changing anything on the rifle.
If I get lucky and find a long seating depth that makes small bug holes then I will explore changes to the action.

[Robinhood]

No. The notch that they mention is actually at the very bottom edge of the chamber that is part of the barrel. My understanding is that it need not be very big, a small radius actually.


Actually, No. A feed cone is cut when the barrel is in the lathe an angle is cut that enlarges the mouth of the chamber slightly. What you describe is a feed ramp. If you look at the picture of this AR you will see the ramps at the bottom(2) and if you look at the chamber entrance you see a concentric ring. That is a feed cone. It allows the tip of the bullet to move towards the center of the chamber so the bolt can continue push the cartridge in.

https://images.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.asos1.com%2Ffirearms%2FIMG_495 3b.jpg&f=1
https://www.northwestfirearms.com/data/attachments/14/14476-8b187a1a0ab62669cf600847cbe5f3a8.jpg

[Idaho]

Actually, No. A feed cone is cut when the barrel is in the lathe an angle is cut that enlarges the mouth of the chamber slightly. What you describe is a feed ramp. If you look at the picture of this AR you will see the ramps at the bottom(2) and if you look at the chamber entrance you see a concentric ring. That is a feed cone. It allows the tip of the bullet to move towards the center of the chamber so the bolt can continue push the cartridge in.

I stand corrected and I'm glad that you came back and straightened me out. Thank you.
You've probably noticed that I have decided to order a temp ramp to test the longer seating depth. If I find a magical number then I will get the ramp cut as you describe.

[Idaho]

By the way. I kept seating a 77gr bullet deeper and deeper into the case until the round would not have any feed issues and I measured the COAL. It was 2.260 inches. Go figure. Savage engineered the feed ramp to lift the bullet with the case shoulder to properly align the tip to feed into the chamber at SAAMI length. Duh.

[Robinhood]

Is there a SAAMI Length for a 77smk? The Sierra manual calls for that length though.

[Idaho]

Is there a SAAMI Length for a 77smk? The Sierra manual calls for that length though.

Good question. I was referring to the standard COAL for most loads of 2.260 inches. The new Nosler Reloading Guide does not list the 77gr CC HPBT for the .223. (that was a waste of money)

That manual does list a COAL of 2.260 for the 5.56 loaded with the 77gr HPBT.

So yes. They are seated deep into the case.