Wyatts Extended Box

[feelinducky]

I'm thinking about putting an extended box magazine into my Remington 270WSM. It will add approx. .10" to the OAL of my reloads. The 270 WSM bullets are seated very deep into the case in the stock magazine and my current seating depth is to magazine length. I'm not sure how far off the lands I am right now but the extra .10 is not enough to get me to the lands. The bullet I want to shoot is 140g Berger. It is a hunting rifle not a benchrest. So, before I take the rifle to the gunsmith and spend a $100 My questions are..

1) What can the extra .10 do for me?
2) With the extra case capacity will I see a decrease in pressure?
3) With the extra case capacity will I see an increase in velocity?
4) What if any are the downsides of installing the extended mag?

If you guys have answers to any other questions that I might be missing please let me know.

Thanks

 

[Daveinjax]

The extra .125" will give you more room to find nodes , add powder , and get more of the bullet out of the case.
Might reduce pressure but that all depends on what you add or subtract.
I had a few case feed issues at first but a stronger spring and a different loading made it go away.
I'd do it again in a heartbeat. It allowed me to find a load the rifle liked and went from a 1" ish rifle to a sub 1/2" rifle all day.

 

[Garycrow]

Keep in mind that it's .100", not .010" you're adding, that's quite a lot. If it's .125" as ducky said then that's a pretty good bit, 1/8". I'd be surprised if you couldn't touch the lands with that. As for the pressure, what really matters isn't where the bullet is seated but how much of a run at the rifling it has so I doubt it's going to affect your pressures much, at least not until you start seating close to the lands where pressures tend to go up.

 

[Hired Gun]

1) What can the extra .10 do for me? Allow .1" longer seating depth

2) With the extra case capacity will I see a decrease in pressure? Yes

3) With the extra case capacity will I see an increase in velocity? Yes if you increase the charge to restore the pressure as long as you don't touch the rifling. If it the bullet touches it can redline the pressure.

4) What if any are the downsides of installing the extended mag? Costs of installation and the box it self. I believe the going rate is about $100. $32 for the box plus shipping.

Getting really close to the lands is not always the best combination for accuracy. For myself I like to get the bullet base or last of the bearing surface even with the bottom of the neck for case capacity.

MBE-4 Magazine Box

This box is designed for the Rem. M-700 Short Action.

It incorporates the same windows and break-point as the MBE-2 for ctgs. such as the WSM.

It extends the O.A.L. of the ctg. approx. .110".

Outside length is 3.070". Inside length is 2.995".