AI Mags Over Inserting?

[Lathe]

Greetings All.

I have recently inherited a customized Winchester Model 70 in 300 Win Mag. It features a Manners stock, barrel by McBros Rifle Co. and I believe CDI bottom metal. I am not sure, but I believe that this rifle has never been fired in this configuration. While testing the rifle, I noticed that I am unable to close the bolt when using AI magazines. It appears that the feed lips on the magazines are preventing the bolt from moving forward when they are fully seated. I have read other posts where people have filed these down to fit, but that it was mostly done when the bolt was dragging on them. Before I send this off to my smith, are there any solutions that I could try? I am not new to working on firearms, but I would love some opinions since this is my first custom rifle.

Any guidance is appreciated.

 

[Trigger Monkey]

If I remember correctly the magazine for .300 WM is the same between the AICS and AW, so it has follower that will hold the bolt open after the last round. Try loading a dummy cartridge and see how it works then to make sure it's just that and not the feed lips hitting the bolt. I believe you can contour the back of the follower so that the bolt rides over it after the last round.

 

[Lathe]

I checked again and while the follower does stop the bolt. I tried depressing it and the bolt was able to move forward a small amount before it made contact with the feed lips.

 

[Trigger Monkey]

Well, hmmmm. It could be the magazine itself causing the issue. I have a Remington 700 in a Grayboe stock that drags over Magpul mags horrendously but works just fine with metal AICS mags. I'd try is get one or two different magazines and try them out.

If you're still having issues, you may need to file some material off the magazine latch to let the magazine ride low enough to function properly so the bolt doesn't hit the feed lips.

 

[Mordamer]

Magazine latch is the easiest fix and also a cheap part that is easy to replace. Try to estimate how much interference there is with calipers. If there is .030" interference then take the mag latch out of the bottom metal. Grind it with a bench grinder or file it until you have removed the .030" or whatever you measured. Try to keep all angles on the mag latch the same. This is a pretty easy fix.

 

[SquarePizza]

Fellow Win M70 with CDI bottem metal here.

You can easily over insert with this setup. I am not sure if it is how CDI cut the bottom metal or it is the magazine catch. I do know that he had two styles of mag release lengths. I never had "too deep" issues when I ran the shorter release, but I had a lot of magazine play and feed errors.

Before he died, Jeff sent me the longer mag release, which solved half of the feed issues by holding the mag up just a little higher, but now if I smack the mag in it can seat too high up and the bolt catches on the feed lips of the loaded mag. If I insert without a smack on the mag, things work better, but I still have just enough feed errors to annoy me.

Honestly, the win 70 with CDI bottom metal is a modification I wish that I had never preformed and it has made me lose interest in that rifle, and really made me a little shy of ever converting any other rifles to a DBM setup.

 

[Lathe]

Thank you, everybody. I think I will try shortening the mag catch on Monday when I have more time. I pulled out a couple more AI mags and tested them and they all seem to have this same issue. Since those are the brand that I have the most of, those are the ones I am going to adjust the rifle to.

@SquarePizza I agree that this action doesn't seem to work as well as some others when modified for a DBM setup. My hope is that I can get this setup running smooth and consistent enough for range use. The barrel on this one is a beast and not something that I would want to compete with or take hunting. I also inherited a Defiance Deviant in 300 WM CIP that I hope will be a much more practical rifle.

 

[BAMAboy18]

I'm by no means qualified to troubleshoot your issue, but a thought did occur, you could try shimming the bottom metal as an experiment. My Howa has a PT&G that was carefully bedded into my stock, my 1st experience with DBMs. So far all my mags are MDT metal. I have a 2nd arriving today that's from Atlasworx, it has a pmag included with it, we'll see how it goes...