7 PRC Tikka AICS Magazine Troubleshooting

[StenTheAwesome]

Hey All,

I'm working on a 7 PRC on a Tikka action. Knowing what I know now I probably would have gone a different route, but it all started with a good deal on a Tikka in a good stock. If I can get some feeding issues sorted I think I'll be out of my rabbit hole (mostly).

Anyways, the rifle is running a Red Snake Tactical LA DBM at the moment. I purchased a .300 Win Mag AI magazine and went to go test it out yesterday but noticed a few issues.

1) The rounds don't strip cleanly from the magazine. The rounds appear to need more of an upward angle to exit the magazine. Currently the rounds are binding on the two small fingers forward of feed lips. If I he-man my bolt forward I can get it to feed, but those two fingers leave nice long scratches on the brass and it seems the rounds dive a bit hard into the feed ramp. The hard stop can be felt stripping rounds my hand without the magazine in the gun as pictured.

2) On an empty magazine the bolt stops on the rear of the follower. This also makes it difficult to seat an empty magazine. Not sure if this is a bug or a feature, but I understand MDT magazines have a 45 degree slope to the rear of the follower and this can probably be fixed with a few minutes on the file.

First time needing to adjust a magazine so before I go bending and grinding on my magazine here I have a few questions:

1) Should I have just bought a .300 RUM MDT magazine instead / will any modification to a .300 WM magazine even work?

2) I have a feed lip adjustment tool on the way. It looks like the rear of the case should sit a touch lower and the bullet tips should point a bit more skyward. Mostly wondering where to bend more to achieve that.

I figure it's a combination of closing the gap on the rear of the feed lips slightly, maybe opening up the front, and probably bending the retaining fingers down a bit. Are my ideas on the physics incorrect here? Does anyone happen to have good rear / front gap measurements for a 7 PRC in a 300 WM magazine that work for them?

Thanks in advance!

 

[ma smith]

As a general rule, magazines only work (ie, 'flawlessly') for a single brass/cartridge design. The culprit here (in theory) is tolerance stacking. You end up with stacks of "new" cartridges don't behave the same, as the "original stack" of catridges the designer planned for.

IMHO, This thread is worth reading for reference.

AI ASXR 300 PRC Magazine Issue

We recently had a customer drop off an AI ASXR in 300 PRC to have the barrel shortened for suppressor use and the scope mounted. When we did an initial function check, the rifle would feed a few rounds and stop due to rounds tilting nose down in the magazine. The stack could be reset by...

www.snipershide.com

 

[UpSideDown]

Hmm, I have a Tikka 7PRC using factory mags, and I also have a Redsnake LA bottom metal and a 300WM LA AICS mag. I haven’t tried the AICS in the Tikka yet. It’s a used Tikka set and someone prior had opened the front of the feed lips on the mag a hair, which is likely exactly what you’ll need to do. Imagine having your round loaded in the mag, grabbing the bullet and pulling the cartridge upwards to the angle you want it at; picture how that will move the feed lips. I would start at the front of the lips bending them open an hair and see what that does, and not bend the rear of the lips inward. Also polish the inside of the feed lips.

I also don’t remember my mag having the little tabs on the front section, maybe I missed them, I doubt they have been cut off.

What length magazine do you have? I think tikkas are supposed to use a 3.515” or so length and the standard AICS is 3.615”? Something like that, I think my dimensions are off.

 

[Gtscotty]

Hmm, I have a Tikka 7PRC using factory mags, and I also have a Redsnake LA bottom metal and a 300WM LA AICS mag. I haven’t tried the AICS in the Tikka yet. It’s a used Tikka set and someone prior had opened the front of the feed lips on the mag a hair, which is likely exactly what you’ll need to do. Imagine having your round loaded in the mag, grabbing the bullet and pulling the cartridge upwards to the angle you want it at; picture how that will move the feed lips. I would start at the front of the lips bending them open an hair and see what that does, and not bend the rear of the lips inward. Also polish the inside of the feed lips.

I also don’t remember my mag having the little tabs on the front section, maybe I missed them, I doubt they have been cut off.

What length magazine do you have? I think tikkas are supposed to use a 3.515” or so length and the standard AICS is 3.615”? Something like that, I think my dimensions are off.

How is the 7 PRC feeding out of factory Tikka mags? That's my tentative plan for when my barrel comes in.

 

[StenTheAwesome]

Thanks for the replies so far. Once I get my feedlip tool in I’ll post my results opening up the front lips slightly.

 

[UpSideDown]

How is the 7 PRC feeding out of factory Tikka mags? That's my tentative plan for when my barrel comes in.

It works 100%, it’s been flawless for me. You cannot handload them longer than SAAMI spec, but they do work. I’ve run 175 ELDX and 180 ELDM and they work great, feeding, ejection, etc. I really like it and it’s become my primary hunting rifle.

 

[4O6shootist]

Get a feed lip adjustment tool. A 300win has way more taper than a prc, so they lips are tighter. Open up the front and rear slightly. Like very minor. Get your caliper, measure widths front rear middle, prior to any opening. Now spread each by about 0.010, insert a cartridge and put it into the rifle. Check the case head presentation to the bolt, the case rim should overlap the bolt face some, maybe 0.050-0.080, once thats tuned now you want to open mid and front of feed lips just sligthly till the case has just a slight upward angle, this will let the case easily go up feed ramp and strip from mag after bullet enters chamber. If your lips are too loose and the nose is too high it can release from the mag lips prior to the bullet tip being inside the chamber and could cause a jammer miss feed. Properly tuning a magazine is an art sometimes. Try tuning a wyatts center feed bdl mag box, they're a real pain in the ass!

 

[StenTheAwesome]

Get a feed lip adjustment tool. A 300win has way more taper than a prc, so they lips are tighter. Open up the front and rear slightly. Like very minor. Get your caliper, measure widths front rear middle, prior to any opening. Now spread each by about 0.010, insert a cartridge and put it into the rifle. Check the case head presentation to the bolt, the case rim should overlap the bolt face some, maybe 0.050-0.080, once thats tuned now you want to open mid and front of feed lips just sligthly till the case has just a slight upward angle, this will let the case easily go up feed ramp and strip from mag after bullet enters chamber. If your lips are too loose and the nose is too high it can release from the mag lips prior to the bullet tip being inside the chamber and could cause a jammer miss feed. Properly tuning a magazine is an art sometimes. Try tuning a wyatts center feed bdl mag box, they're a real pain in the ass!

This is probably the most thorough paragraph on tuning feed lips I've seen. Exactly what I was after. I'll give this a shot when the tool gets here. Thank you!

 

[4O6shootist]

This is probably the most thorough paragraph on tuning feed lips I've seen. Exactly what I was after. I'll give this a shot when the tool gets here. Thank you!

Glad to help my man, best of luck. Have any more questions I'll be following.