DIY 7mm STW

[Victor3Ranger1]

Here is a little project I have recently been working on for my father. This was more or less an experiment to see if I could successfully rechamber a 7mm Rem Mag barrel to 7mm STW. Here are my results:

So, my father had a Remington 700 ADL that he bought sometime in the 1980s. Until now, everything was factory original however the 24" barrel was not shooting well with any handloads (and we tried a lot). So, I thought it would be a good idea to take the factory new 7mm Rem Mag barrel that I took off of my Remington 700 to put a Shaw STW barrel on and rechamber it. These new RemArms 700 barrels come with a 1-8" twist from the factory and are 26", so why not?

First, (not pictured) I sanded off the factory finish and applied rust bluing to the barrel to try and match the high gloss hot blue of my father's receiver. Next, I rented a 7mm STW solid pilot finishing reamer, t handle, and belted headspace gauges from 4D Reamer Rentals (great people btw). Pictured below in the new take off 7mm Rem Mag barrel staged up in my vise to begin cutting the chamber.
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Here, I removed the ejector from the bolt and cleaned up the bolt face with a degreaser and a bristle brush.
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Here is the STW chamber reamer secured to the t handle and coated with cutting oil.
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So, I slowly inserted the reamer into the chamber and began cutting. I was applying moderate hand pressure and could get a good feel for how much material was getting cut away. I would remove the chamber reamer every 10 full rotations because I had a lot of material to remove in the beginning.
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After about 20 minutes of cutting the chamber in my vise, the belt-cutting part of the reamer was getting very close to where the existing belt cut-out was in the chamber. So, now was a good time to spin the barrel on the receiver to check my headspace and progress.
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Here, we can see that the bolt closes on the GO gauge and does not close on the NO-GO gauge. Realistically, cutting the chamber up until this point would not have affected the headspace because these gauges only measure the distance between the bolt face and the belt, so regardless of how deep the chamber was cut, it would only know if I went too far.
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So, as a quick and dirty way to check my cutting progress, I used a factory Nosler 160gr AB round and a virgin piece of Bertram brass.
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Continued below:

When you finish the reaming of the chamber do you leave it as is or do you polish it somehow?

 

[ButterBean]

Nice job

 

[JakeWes]

When you finish the reaming of the chamber do you leave it as is or do you polish it somehow?

I thought about it, but the fired brass comes out smooth with no marks or scratches. The marks on the fired brass in my picture are from my die and case trimmer.

 

[Bob Wright]

Congratulations! There are some nice options to how a rifle gets chambered these days.

 

[Victor3Ranger1]

I thought about it, but the fired brass comes out smooth with no marks or scratches. The marks on the fired brass in my picture are from my die and case trimmer.

I'm really curious because I have a STW reamer and would interested in knowing how to do this.

 

[VinceMule]

JakeWes, you may want to look into a Wyatt's mag box for your 7 STW. As handy as you are, with a dremel you can open up the mag well and change the bolt stop, easy. Use a carbide bit in the dremel tool.

 

[JakeWes]

I'm really curious because I have a STW reamer and would interested in knowing how to do this.

Sure, if you have any questions not already mentioned in my post feel free to message me.

 

[JakeWes]

JakeWes, you may want to look into a Wyatt's mag box for your 7 STW. As handy as you are, with a dremel you can open up the mag well and change the bolt stop, easy. Use a carbide bit in the dremel tool.

TBH I really do not need to extend my magazine since I mostly shoot Hammer bullets for my hunting purposes and I do not have case capacity issues. The 160gr Shock Hammers that I shoot jam into the lands at 3.600" so they are seated deep at 3.550".

 

[ButterBean]

I'm really curious because I have a STW reamer and would interested in knowing how to do this.

We did this a bunch back in the day, just take your time and it's not that bad at all