Im thinking of putting my Bergara 7 PRC in my MDT LA chassis.

I see magpul makes two AICS Pmags, one for LA Standard and one for LA Magnum. Same OAL, but for different case heads.  
I initially thought the Magnum version, But the 7 PRC has no belt, but its case head is .532.  So Magnum?

Standard:
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https://magpul.com/pmag-5-ac-l-standard.html


Magnum:
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https://magpul.com/pmag-5-ac-l-magnum.html

Magnum is what you want, but I wouldn't use mapul plastic mags..you can only load to 3.5" max, I would go Accurate mags and use their 3.850(gets you 3.715" OAL) Long Action Remington mags, as long as your chassis will take them, other wise the correct length to fit your chassis...And if your chassis doesn't accept 3.850" mags, I would use MPA who does take all 3 size mags including the 3.850"(you change a small shim to adjust for any LA mags)... Magpul is not the right choice for LA mags....I use Accurate's  3.850 mags made for 300rum(specific mags) they are extremely nice mags...

https://accurate-mag.com/shop/magazines/300-win-mag-sssf-magazine/


Edit TO ADD:.. You need to ask Accurate Mags, but I bet with the 7PRC you will have to use the 300rum/338lm mags or something else because the 7prc has a bigger cartridge diameter than 300wm...Call and ask them before you buy a bunch of stuff that won't work for you...


Might be 338LM mags...

https://accurate-mag.com/shop/magazines/338-lapua-mag-sssf-magazine/

Or maybe 300rum mags...

https://accurate-mag.com/shop/magazines/300-remington-ultra-mag-sssf-magazine/

It’s definitely not going to work in a standard LA mag and I doubt it would work in a 300WM mag that you can’t bend the fees lips on since the body taper is way different.

I’d call Accurate or MDT or both and ask them which of their mags they recommend for it and go with that. The magpul mags are not all that great.

Thank you both for the input here.

I have an MDT LSS chassis, Remington LA  

I have a 35 Whelen in there now, and modified some standard LA Pmags for it.  It woks, but I had to do a lot of work to get them 100% accurate.

I will look at Accurate Mags to find something usable.

300 Win Mag Accurate mags will work fine as the 7 PRC has a far shorter COAL than the 300 Win Mag.  
Ive seen plenty of 300 PRCs run fine from the 300 Win Mag Accurate mags, so dont sweat the idea that the PRC is fatter.  They use the same magnum sized bolt head.
FWIW, I run my 300 PRC from 300 RUM mags, but only because I want the extra COAL length for messing with reloads.

I would use the longer mags as well, simply because it cost the same but gives you options down the road if you need them...(I do run the 300 rum with Accurates 3.850" CIP mags)...

I have just acquired a magnum length rifle in 300 PRC.  It came with the Accurate Mag 3.850 for 300 RUM and feeds slick as snot.

It also feeds the 6.5 PRC no problem.  I have no doubt it will also work well for the 7 PRC.

300prc in the begera uses cip length.  The regular la magnum is too small.

Just an FYI, 7mm PRC fits and feeds from the Magpul LA Magnum magazine fine.  

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Good to know.  They would probably work fine for 6.5 PRC as well.  Might be a little short if you want run 300 PRC reloads with longer than factory COAL.