Help! DBM and AICS Mag Over-Insertion

[Dunderhead]

That is the way it is.

when loaded, rounds in the mag will put downward pressure on the spring, holding the detachable mag down away from the bolt when the bolt is closed. When the bolt is opened, the weight of the loaded mag will keep it down unless you are cycling the bolt with the rifle help upside down.
If you are dragging the bolt across the top of the mag, you can add thin washers between the stock inlet and DBM bottom metal to slightly space it away from the action.

Thanks for the feedback! This just seems like such an oversight that any pressure upwards be it from resting on an pack etc, would cause an issue!

 

[Dunderhead]

Is the latch adjustable as some are?

Nope, not adjustable

 

[Shane Lindsey]

any pressure upwards be it from resting on an pack etc, would cause an issue!

Can do the same with an AR platform.

 

[Dunderhead]

Almost all DBM magazines only have a stop to keep the magazine from falling out, all will continue up like yours. Your action needs to have been ordered with correct magazine cut, such as RUM, Lapua, Magnum, standard Long action etc. You did not say what caliber it was.

I'm pretty sure all Zermatts simply come in short, medium, and long action lengths only. The TL3 is compatible with AW mags, but otherwise the cartridge length is only limited by bottom metal and magazine (long, CIP, CIP+)

And it's a 7PRC, btw, so standard long 3.715.

 

[Dunderhead]

I previously had issues with AICS with BHA SR2, and my GS's magazine lip adjustment tool resolved the issue. It may or may not solve yours, but here it goes.







Good luck!

Thanks I'll take a look!

 

[Dunderhead]

Can do the same with an AR platform.

Just pulled the ole scary rifle out to check. Upward travel is limited by the top of the magazine catch.

 

[ARlife4me]

the issue like that i've had was due to the bottom metal sitting to high. shimmed it and fixed the issue. the feedlip issue is only for proper feeding. bend them in to far and the lug/bolt face will catch the mag instead of the next round. the only time i've had (only because ar's were mentioned) is aero precision lowers don't work with acs mags. the ap catch sits ~.125" to high and a fix (if deciding to use the acs mags) is too file the top portion of the catch for it to sit lower.

 

[JAYgs8163]

Did you try with a loaded magazine as Lance mentioned as this puts downward pressure on the Mag.

 

[JAYgs8163]

Is your McMillan pillar bedded already or not? Some bottom metals come with pillars also and if your McMillan doesn't have pillar bedding already from the factory then they would need to be installed.

 

[MOA or bust]

I have a Defiant Classic in 7 PRC with Grayboe M5 bottom metal and Manners PH stock. I am using a 3 cartridge Accurate Mag AICS magazine with 3.850 length. The mag when inserted bottoms out on the receiver (under feed rails in the back and underneath the feed ramp in the front). What stops your mag when inserted?

 

[Dunderhead]

Thanks to all for the feedback and apologies for the delay. I wanted to complete the assembly of my rifle and get some actual loaded cartridges in hand to test the real world fit and function with this set up.

Parts refresher:
- Action - Zermatt Origin LA - which comes with Remington style feed lips. Capable of accepting AICS Long, CIP, and CIP+ length bottom metal and magazines.
- Bottom Metal - Grayboe M5 DBM "Long" 3.715"
- Magazine - Accurate Mag 5rd 3.715" (300win mag length)
- Stock - McMillan Game Warden LR - Inlet for Rem 700 Long Action clones - Pillars installed

With a loaded magazine and the bolt open, there is approximately 0.25" of vertical travel between the magazine bottom position where it is stopped by the mag catch, and the top position where the top of the magazine makes contact with the bottom of the action. I didn't note exactly where contact is occurring (to answer your question @MOA) but I can follow up on that, but I believe the magazine feed lips hit the action feed lips. The amount of vertical play still strikes me as excessive and seems like it would be temperamental with regards to feeding, and no surprise, it is.

With the magazine in the absolute downward position the bullet tips get pressed into the vertical portion of the action just below the feed ramp/bevel and will feed no further. This might be fixed with some tweaking of the front portion of the magazine feed lips. All of the mag tuning videos presented are for short action mags and suggest a consistent gap of 0.4". My mag body has a noticeable taper front to back and I can't seem to find any recommended spacing for the 7PRC/long action AICS Mags.

With the magazine pressed all the way upward the bolt gets stopped by (I believe) the back of the magazine. It might be the back of the feed lips. I will try and verify. There were suggestions to shim the bottom of my bottom metal, but that will simply exacerbate the problem described above where the round feeds too low and is being driven straight into the vertical face of the action. There were comment above stating that the weight of the loaded mag will hold the mag low enough to keep from being over inserted, however what happens after I fire 4 rounds and now I have a mostly unloaded mag?



My next step is to reach out to MDT and see if their adjustable mag catch could be modified to fit into my Grayboe bottom metal. Any other suggestions appreciated!

Perhaps it's the engineer in me, but I just can't figure out the sloppiness and excessive vertical play that seems to be considered acceptable in this system. Having a rock bottom stopping point only on the bottom direction of travel with no purpose driven limit at the top seems like a system destined for failure.

Thanks to all for your time and insight!

 

[eshell]

Just pulled the ole scary rifle out to check. Upward travel is limited by the top bottom of the magazine catch.

Yup.

 

[JAYgs8163]

You mention in the gear list: Accurate Mag but then you mention you may need to call MDT to see if the mag catch is adjustable? Do you have an Accurate Mag or a MDT mag?

In the last video are you pushing up on the mag to make it hit the feed lips?

 

[Dunderhead]

You mention in the gear list: Accurate Mag but then you mention you may need to call MDT to see if the mag catch is adjustable? Do you have an Accurate Mag or a MDT mag?

In the last video are you pushing up on the mag to make it hit the feed lips?

It is an Accurate Mag magazine, but MDT makes an adjustable magazine latch that I'm hoping might be able to be made to fit my bottom metal.

And the last video I with the mag pressed all the way up until it stops and then trying to chamber a round.