Is there a downside to installing a Wyatt's Extended Mag Box?


Well-Known Member
Dec 18, 2009
I am considering the purchase of a new production Winchester Model 70 in .338WM. If I decide to go through with it, I intend to have a Wyatt's Extended Mag Box installed to allow me to load bullets like those offered by Cutting Edge and still be able to feed from the magazine.

Is there a down side to having this done?

Are there any issues regarding this that I should be aware of before I decide to go that route?
I am taking the lack of response to my question as an indication that no one has had any problems related to having an extended mag box installed. I will proceed then , at some point, with my plans.
No input but followed along as I have the same question. Hopefully bringing it back around catches the eye of someone who knows.
I have had them put in several rifles that I have shot before and after and never seen any affect on accuracy good or bad. Although you are taking metal out so it is weakening the action to some degree. I have had it done in a 300 win 2 300 ultras and a 375 ultra. I would think if it were gonna be a problem I would have seen it in my 375
Thanks Mike, I'm replacing the stock on my 338 RUM. I don't need the length currently but this is the 3rd barrel. Thinking maybe just do it all at the same time who knows what the future holds.
Thanks, Tikkamike, for your feedback.

My concerns involve the amount of metal removed, smoothness and reliability of feeding after the modification, and the fit of the bottom metal after modification (hindsight, guess I should have stated that up front).

I am glad to know that this modification has worked well in your rifles. I would have to agree that if you didn't have problems in your .375, the mod is probably pretty solid.

Thanks again!
As for fit, finish, functionality, I have no problems with this mod. Now, I have a philosophy of K.I.S.S. and it's just something else to go wrong. I have one on my 300RUM and it is nice but I have also found I can load the heavies in it at about max mag length and still get superb accuracy. I used standard BDL BM on my 280AI to eliminate the possibility of forgetting or losing a magazine in the mountains and finding myself bareassed up there. I'd like to say it will never happen but I have seen it happen personally both ways so I chose to eliminate that possibility with my next build. Just something to consider...
Installed one on my Darrell Holland built LR 6mm Ackley (1-7" Lilja, flinging the 107 Sierra easily into 1/2 MOA AT 1K!) on a Rem700 short action. VERY PLEASED that now I can seat the bullet out to match the cartridge capacity, instead of using the 243/308 length, PLUS Kevin (the owner) is a great fella to do business with! Highly recommended for those LONG cartridges, short or long action! :)
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