Sp101 38sp conversation to 357

Many older Rugers are already through-bored, only the markings are different. Can you see a step in the charge holes? If not, Ill betcha a .357 will chamber in it. If its an older one with a full-length stepped cylinder it could, theoretically, be bored to accept Magnum ammunition. The manufacturer will never tell you this is safe, nor will I, but it was a common practice with Ruger and S&W revolvers years ago.

On newer .38s, the cylinder is shorter and the barrel extension longer. These would require the barrel and forcing cone recut, as well as a long cylinder for conversion- probably more trouble than its worth.

You cannot shoot a .357 in a 38 or it will blow up.
Even if you could get a round in cus .357s are longer and won't fit.

This is a question for the manufacturer.

SSBN617b said:

Mine has the step. Perhaps a cylinder change would be enough?

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If you have the full-length .38 cylinder with the short barrel extension, then a .357 cylinder should fit.

We have covered this issue many times in the past and our members have contacted both Ruger and S&W. They will NEVER tell you this is ok or safe due to liability issues.
I am not saying it is safe or advisable either- however it is technically feasible and has been successfully done many times in the past.

Many older Ruger .38s were only marked as such for LE contracts for agencies that prohibited Magnum duty ammunition, such as the various French police orders. These were standard production .357 guns and only the markings were changed. It was an open secret that they would chamber and fire Magnum ammunition.

Revolvers that did have the long stepped .38 cylinders were bored out with such frequency by owners and gunsmiths that Ruger introduced the shorter cylinders specifically to make conversion impractical, once again for liability reasons.

We've seen the pleadings to not alter this or that classic and I usually agree. My argument this time is to not spoil the pure romantic 38 Special. Yes, 357's are special but not romantic to me. I have a number of 357's and the 38 has always eluded me. Plus, I wouldn't spoil that French Police trade-in. Thanks for hearing me out.

Massad Ayoob's gunsmith routinely rechambered .38 SP101s to .357.
They would only take short OAL Magnums as would early factory guns.
Later ones have longer cylinders.

They are the same gun; one's just drilled for 38 and the other for 357 magnum. I have both; check with Ruger.

My SP-101 3” Is a .357magnum w/bobbed hammer.
It will likely be cheaper to trade for a .357 than to rechamber.
Shipping two ways is cost prohibitive.

Besides, my wife keeps the Ruger in her night stand unloaded, with three speed loaders. (We have four curious grandchildren!). She much prefers .38+P to magnums.
My go-to revolver is a Taurus 856 6-shot .38 with +P 158gr SWC-HP.
It’s actually smoother, has a better trigger, and more accurate than the Ruger. And, has 6-shots.
You can buy a new .357 for little more than the cost of drilling your cylinder.

I used to have a 357 SP101.

Shooting 357 out of it wasn't painful, but it was work and the follow up shots were slow. I ended up shooting 38's out of it almost all of the time.

Is it just me or is it most people don't realize a .357 mag has twice the pressure of a 38 therefore .357s are built twice as strong and if you drill out a 38 to shoot .357s it may blow off your hand?

An interesting question, the manufacturer is not likely to tell us.
But I recall that when M. Ayoob was having SP101s rechamsbered, it was with Ruger's approval.

On the other hand, we had a poster who bought a GP100 marked .38 Special but chambered .357 Magnum.
He sent it back and they installed a cylinder that matched the roll mark.

plainsdrifter said:

Is it just me or is it most people don't realize a .357 mag has twice the pressure of a 38 therefore .357s are built twice as strong and if you drill out a 38 to shoot .357s it may blow off your hand?

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Almost four times the pressure: SAAMI has .357 Mag max at 65,000 psi, .38 Spl. at 17,500 psi. (+P is 20,000 psi, so its 1/3 the .357 Magnums max pressure.)

Some folks will alter their guns’ chambering, which of course is their choice. If the SP .38 can handle the .357 Magnum pressures then it is certainly an option.

Stay safe.

Riomouse911 said:

Almost four times the pressure: SAAMI has .357 Mag max at 65,000 psi,

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Not in my copy, which says 35000 ppsi MAP.

plainsdrifter said:

Is it just me or is it most people don't realize a .357 mag has twice the pressure of a 38 therefore .357s are built twice as strong and if you drill out a 38 to shoot .357s it may blow off your hand?

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The frame, cylinder thickness, materials, and heat treatment of the .357 and .38 SP101 are identical. This is also true of the K-frame S&Ws made in the last 50 years.

During some production runs, the cylinder LENGTH is different, as is the barrel extension to maintain a tight B/C gap. The frame windows are the same.

They are not built "twice as strong." For economy of production, the manufacturers design these pistols to handle .357 pressures and simply alter the machining processes as little as possible (or not at all) to accommodate .38 Special, then mark them as such.

It would be wastefully expensive for them to forge/ cast 2 different pistol frames and/or cylinders for these cartridges because they are dimensionally so similiar.

plainsdrifter said:

Is it just me or is it most people don't realize a .357 mag has twice the pressure of a 38 therefore .357s are built twice as strong and if you drill out a 38 to shoot .357s it may blow off your hand?

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It is just you.

SSBN617b said:

Plainsdrifter, I understand what you are saying. My question is the 38sp the same specs as the 357 but having 38 sp markings due to law enforcement regulations. I can’t understand that a company would bother to make two identical frames of different specs.

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The frames are the same. Cylinders may have been changed to protect the innocent.

Buy some Buffalo Bore .38 +P, save the money they will get you into .357 Range without all the fuss.

crstrode said:

It is just you.

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I think not.
I read my SP101 manual I got with my .357 mag (Ruger sends the same one for 38 special and 9mm) and no where did it say you can shoot a 357 mag out of their 38 special model.
Plus these guys also agree with me.

https://aliengearholsters.com/blog/can-a-38-special-shoot-357/

wcwhitey said:

Buy some Buffalo Bore .38 +P, save the money they will get you into .357 Range without all the fuss.

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And hurt just as much

The first/original SP101s were in .38spl only. I have one. Later after folks started to drill out chambers for more fun, Ruger came out with through drilled chambers themselves. Those first .357 guns were marked as 125gr only due to overall cartridge length. Later Ruger noted the differences with an 'X' in the serial or catalog number. Current production frames are all the same.

I don't know, but a thought occurs to me. I have a Ruger 9mm SP101. I believe the 9mm and .357 operate at very similar pressures. I have shot a wide variety of ammo in my SP101, with no issues whatsoever. Cases practically fall out of the chamber, even with some of the hotter stuff.

I've always wondered if major revolver manufacturers would go to the trouble of using different manufacturing processes, other than chamber dimensions, etc. when producing .38, .357 and 9mm cylinders. I've not worked in manufacturing, but would that be cost effective? This, along with the potential for a structurally weaker cylinder accidentally getting into the production of say .357 revolvers requiring a stronger cylinder...