Thinking about rechambering a 7mm Rem Mag A-bolt to 7mm STW. I'd be interested in hearing from anyone who's performed this conversion as to what you would do different if you were to do it over again...any thoughts?

A good friend of mine converted a 7MM to a 7STW. My strong advice..Don't waste your time. You have to ask yourself, what are you really gaining in real world performance and at what cost?

Other than that the conversion went well of course he didn't have the feeding issues that will need to addressed on a bolt gun.

I've done both M700 and M70 the 700s being the easist. No real issues except the M70 did require the mag box, bolt stop, ejector alerations. Unless you have a 26" barrel I would leave the rifle as a 7mag. Even with a 26" I would have to do some serious soul searching. A STW is loaded to higher pressure than the 7mag. In a 24" loaded to equal pressure you are probably looking at 50-75fps gain with a LOT more powder and barrel wear.

Even in a 26" I found I really had to really push the envelop to even get in the ball park of many of the posted velocities.

I had the conversion done on a Sako. The gunsmith recommended setting the barrel back a half-thread in order to assure that the belt recess was minimum and that there were no surprises like the original chamber having too little taper to allow the STW to clean it up. This also turned the factory stampings under the wood so that the gunsmith's "7mm STW" stamp was the only marking showing. Of course, no front sight was involved, which is nice if you don't care for your sight on the bottom side of your barrel.

The work was flawless and nothing else was required. To achieve any meaningful increase in velocities it was necessary to utilize EXCEEDINGLY slow powder. At that time (15 or so years ago), the only such powders generally available were some surplus powders. By carefully working with those I was able to achieve some fairly impressive velocities.

However, to me the 7mm bore is neither fish nor fowl. If I want a long-range screamer for medium or light game, the 6.5 bore is a better choice. If I want to deliver lots of energy and momentum to heavy game, either close or far, then the .30 or .33 calibers offer a lot more. In the end, I found that the STW could do very little that one or another of my rifles couldn't do better. I sold it to a friend who, having the same experience as me, ultimately sold it to someone else.

About the only good reason I can think of for the conversion is IF you shoot only factory loads, then you'll find that 7mm Rem Mag factory loads are all over the place in velocity and power, with most of them being rather anemic. STW factory loads, pricey though they are, tend to deliver respectable velocities, though somewhat below advertised levels. If you are a competent handloader, there may be 50 to 100 fps difference in the two cartridges at similar pressures.

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I did it last year with a push feed Mdl 70 that started off as a Black Shadow version.
( AKA a WalMart special.)
It has a 26 inch barrel.
Yes the magazine and the bolt stop had to be modified.
My current load uses WC872 powder and a 160 Nosler Partition which is leaving the muzzle at 3320 FPS. As a 7Rem Mag I was getting around 3150 FPS.
Since my 'smith already owned a 7STW reamer he charged me all of $50.00 to do it.
Was it worth it?
Absolutely.

The only thing I would do different, I'd start with a Rem 700 Action. SAAMI spec for OAL on an STW is 3.600. That is exactly how long my magazine is. I have to load to an OAL of 3.590 in order to feed out of the mag.

Howard

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160 Nosler Partition which is leaving the muzzle at 3320 FPS. As a 7Rem Mag I was getting around 3150 FPS.
Since my 'smith already owned a 7STW reamer he charged me all of $50.00 to do it.

That is 100fps+ what I could get out of my 26" STW. That is closeer to my max load using 140 Accubonds.

Plus setback and rechamber for $50 what a deal.

The 7STW can best the 7mm Rem by more than 100-150fps without using dangerous over-pressure loads. A-Square had factory loads that I tested over a chrony and they met their advertised velocities and I saw zero signs of over-pressure in my rifles. I had two M700's built with high quality barrels. Getting 3500 with a 140 and 3350 with the 160 was no problem. I did even better than that with some specific tricks, one of which was using Winchester 300 H&H brass necked down and fireformed in my chambers, yielding a bit more powder space and a slightly larger combustion chamber due to thinner case walls..but at the expense of brass life as I could only get 3 safe loadings with it. The STW is still one of the flattest shooting cartridges and is right there with the 300RUM, with a lot less abuse to the shooter. Yes, I have a 300RUM too.

both rounds are excelent.
I had an stw, but realized that as a city dweller who does not get much chance to shoot 7mm rem mag gives me all the range i can use...tj3006

Woodrow S Could you please elaborate on why you were only getting "three safe loadings" from 300 H&H brass. Are your primer pockets loosening up after 3 loads or are the necks on your cases splitting or what????

The beginnings of case head separation. I cut the cases lengthwise after each loading during the experimental phase and noted the thinning of the case just above the belt. 3 max loadings was all I was willing to shoot to avoid any case head separations. I suppose I could have used just a neck sizing die and most likely could have gotten more case life...but back then when the cartridge was first written about in ST magazine it was hard enough just to get the FL dies and I did not want to shell out the $$ for custom die sets. The rifles I had built with 26" Lilja barrels sure were superb in accurracy..the 7STW has a lot more potential than most people realize. With the 120gr monometal bullets today moving at 3700-3800fps...what a great flat shooting medium game rifle that would make.

A fellow I know rechambered a 7mm REm in a Model 700 a few years ago and the chamber didn't clean up. As I recall about midway case length. Probably bad factory chamber.
I've got a STW and like it, but for my use I am sure a Remmy or Mashburn wildcat would do the job just as well. Mine is LH Mod 70 factory 26"

Thank you for the replies guys. Having formerly owned a 7mm Ultra, which was and still is a great rifle to its current owner, I'm either going to build an STW or rechamber my Abolt. Just have not decided how much money I want to sink into it yet as I find myself only in need of it a few times a year which was the reason I let it go int he first place.

a re-chamber on an A-bolt might be as much as building one on something else. With M70's or R700's its a matter of removing a magazine block and possibly some tinkering with the extractor and/or bolt stop but that is about it. For the A-bolt you'd have to source a new magazine and probably a new bottom metal. I'm not sure if Browning uses a one-size-fits all action like Rem/Win for their long actions. But, they do make a 375 H&H, so that would solve the magazine problem and possibly the bottom metal/floor plate if you can order that directly from Browning. Never really seen a market for used A-bolt parts like you do Win/Rem/Mauser, etc