Gunsmithing 300 PRC feeding issues, Remington 700

[flyfisherman246]

700 Long action in a KRG stock using .338 lapua CIP length AICS mags. Already cut 1/4" notch on the feed ramp .125" deep. The tips of the rounds still occasionally find their way under the feed ramp. I don't want to cut any deeper into the ramp. Factory Hornady 225 ELDM ammo. Any ideas of how to go about this?

 

[LRI]

If this were me, step one is reviewing the amount of case overlap you have with the bolt face. The term I use is "figure 8".
Imagine the receiver bore as a complete circle. The primer pocket needs to be tangent to that arc. On a push feed action, this has shown me to be a pretty reliable means of setting up the case presentation. My guess is that if your using a 338LM magazine there should be plenty of overlap just because the feed lips are a bit wider allowing the PRC to sit "higher". Never hurts to check though.

The other thing you may be fighting is the shoulder/rib retention on the magazine. Throwing the two cartridges on my optical comparator (338LM/300PRC) there's only around .04" worth of height difference along the shoulders, however, when I put the two in a magazine the PRC has a whole lot more forward/aft slop with where the rib structure is. It would be interesting to see what a CIP (3.88) length 300 Win Mag magazine would do for you.

Hope this helps.

 

[flyfisherman246]

It actually started with a .300 win mag magazine and that took a whole lot of opening up feed lips to cycle. I have heard the .338 lapua mags are the way to go on the PRC. I think you might be onto something with the should/rib location. What mags are guys running smoothly for .300 PRC's?

 

[Jscb1b]

What is your overall cartridge length? I was running factory berger 215 in a .300 wm. This is in a krg w3 CIP length. There was enough clearance from bullet tip to the inside of the front wall of the mag, that when chambering a round, the cartridge underneath the top one was pulled under the feed lip. I made a binder plate for the mag. No more problems. Can you switch to non CIP magazines?

 

[Terry Cross]

700 Long action in a KRG stock using .338 lapua CIP length AICS mags. Already cut 1/4" notch on the feed ramp .125" deep. The tips of the rounds still occasionally find their way under the feed ramp. I don't want to cut any deeper into the ramp. Factory Hornady 225 ELDM ammo. Any ideas of how to go about this?

Your mag lips nor the amount of protrusion into the bolt path likely matter here.

If your cartridge is moving vertically in the feed stack as it feeds up in the magazine and is still getting under your feed ramp, it is more likely a function of where your magwell is in relation to the receiver.

Place a cartridge in your magazine.
Insert magazine into rifle with bolt forward.
Once mag is latched into position, pull your bolt to the rear until it hits the bolt stop.
Before it hits the bolt stop, the cartridge will pop up into full contact with mag lips as the bolt body moves out of the way.

How far does the bolt travel between the time the rim of the cartridge pops up and when the bolt contacts the bolt stop?


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[Terry Cross]

Here is better way to examine the mag position.
Strip the floorplate and follower/spring out of your magazine.
Insert and snap into position.

The rear wall of your magazine box ("A" in the image below) should be just far enough to get in front of the protrusion in the rear of your receiver's mag well ("B" in the image below.

Here is another angle looking through the bottom of the stripped magazine body up toward the receiver's feed ramp.

If the rear of the box is in the proper point in space under your receiver, the front edge of the magazine body should be even with or slightly toward the rear of the feed ramp. Ref image below.

The Rem 700 long action receiver has just enough room to correctly position a CIP magazine.
If positioned properly, your magazine is incapable of getting the tip of a round under the ramp.
You should never have to notch a feed ramp.

If the front of your magazine body is forward of the feed ramp, your stock or bottom metal is positioning the magazine at the incorrect point in space.

Remington M700 LA mag receiver and Accuracy International 338LM CIP mag shown in these pics.


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[flyfisherman246]

Thanks for all the help. The customer brought in the rife and it wasn't even the feed ramp it was hanging up on. It was catching on a tab sticking into the magwell on the KRG chassis itself.