Interesting turn of events with my new (old) Ruger SP101

[bcp477]

I recently found a terrific deal on an SP101....too good to pass up. I wanted one for awhile, anyway. A check of the serial number online revealed that this specimen is 20 years old - made in 1994. No matter, as the gun showed VERY little wear. In fact, it appeared that the previous owner fired very few rounds through it (the very faint carbon rings on the front of the cylinder came off completely, with a bit of solvent and a light scrub). Of course, function, lockup, timing, etc. was/is perfect. Anyway, a good gun at a great price.

Oddly enough, though, the barrel had a tendency to lead with my regular 38 Spl. loads, which work perfectly (and are dead nuts accurate) in my S&W. These consist of 3.5 grains of Bullseye, under a 125 grain 0.357" diameter (BHN 12-15) boolit. A bit of investigation revealed tight cylinder throats and a tight barrel. 0.357" diameter boolits have to be driven through the chambers with a dowel and hammer. 0.355" diameter almost fall through the chambers (almost, but not quite). 0.356" diameter seem correct, for the cylinder (chambers)....but the unknown was the barrel. I did not want to attempt to fully slug the barrel, out of fear of sticking a slug in the bore, so I drove one into the muzzle, then out again. This indicated that the groove diameter was a bit over 0.355", as best I could measure.

Long story short, I tested the load listed above, except with 0.356" dia. boolits, at the range this afternoon. Much better accuracy than with 0.357" dia.....and no trace of leading in the barrel.

So, I have a 20 year old .357 mag SP101... with a 9mm sized barrel and cylinder. Interesting. I was afraid that I would have to ream the cylinder throats to get the right combination, but it turns out that I can just use the same cast pills as I load for my 9mm's anyway. Not a bad outcome, I think, even though I will have to continue with 0.357" dia. for my S&W. I can live with it.

I really like the gun and now that I know how to load for it, all is in order, as they say. An acquaintance at the range has the same model as I, but only a couple of years old....but it seems to have a "normal" barrel and cylinder.

Anybody else with an SP101 have a similar experience ? I am keenly interesting in whether this is a common phenomenon....or whether I have a true oddball.

[Petrol & Powder]

I've owned several SP101's and they are solid guns. IIRC Ruger has an odd number of lands in their rifling so I wonder if you're getting an accurate measurement on that slug from the barrel. Tight throats are classic in Ruger revolvers from what I've read and my own experience seems to back that up.
My guess is that you really have a groove diameter closer to .357". It really doesn't matter what the barrel diameter is because those throats are sizing the bullets to .356" anyway !
In any event if your combination is making it work then so be it.
If you really want to slug the bore I would used a well lubed .36 soft round ball and a brass rod to drive it all the way through the barrel. If your .357" bullets are working then it doesn't matter what the groove diameter is. Results and not theory, is what matters.
The early SP101's had shorter frames but around 1991, Ruger started making all SP101's with the longer frame to accommodate 357 magnums. The early 357 magnum models were limited to 125gr bullets due to the short 38 Special cylinders used in the early 357 mag models. Only about 3000 of those were made and they were marked on the barrel for 125gr bullets only. The gun was plenty strong but the cylinders were too short for the heavier 357mag bullets. Your example made in 1994 would have been produced long after they switched to the extended (current) frame/cylinder size. Its 20 year old age in NO way limits the usefulness of that gun. The SP101's are some of the strongest snubnose revolvers ever made and the age of yours is a complete non-issue. Enjoy your new gun.

[DougGuy]

If you send me the cylinder I will be glad to send it back to you with .3585" throats if you decide this is necessary..

[Petrol & Powder]

bcp477 - that's a good offer from DougGuy if you're going to be shooting cast out of that gun most of the time.

[bcp477]

Thank you for the offer, DougGuy. That is very kind of you. Actually, as it happens, I live in Raleigh, NC....so the logistics would not be difficult at all ! What concerns me is IF in fact the barrel is as tight as I think it is, then shooting .357" or larger boolits would involve the barrel really swaging them down (alot). As I said, the gun shoots very well with the .356" slugs I tried today. It shoots .357" not too bad, really (except for the leading) ....but MUCH better with the .356". So, I will have to think it over. In the meantime, I intend to obtain some dead soft slugs and properly slug the barrel. At that point, I should be able to make an informed decision.

Thank you both (for the information and the offer, respectively). I'll give it alot of thought.

[bcp477]

Here is a followup. I finished reassembly of the revolver a few minutes ago, after slugging the barrel. As best I can measure, the groove diameter of the barrel is indeed very close to 0.355". My read is just a hair over 0.355"....0.3551" or 0.3552".

At least the barrel dimensions are smaller than the chamber throats, which is the desired situation. You never want it to be the other way around (the chamber throats smaller than the barrel groove diameter).

This would tend to explain why 0.356" dia. boolits seem to shoot well in this revolver, with no leading and great accuracy.

I am still considering whether to ream the chamber throats a bit larger, to make use of "normal" 0.357" diameter boolits a better prospect. I am sure that I don't want to go as large as 0.358" or 0.3585"....as I think that would be too much of a jump down to (just over) 0.355" through the barrel. I don't intend to use larger than 0.357" pills in any case, so IF I enlarge the chamber throats, I think that just a bit over 0.357".....say around 0.3575", would be more correct.

[Petrol & Powder]

How did you measure the bore diameter?

[bcp477]

Slugged the barrel, using a dead soft slug made from a fishing sinker. I pushed it through the barrel, from muzzle to forcing cone, using a hardwood dowel I cut down to fit the barrel fairly tightly. Lots of oil, of course.

I measured the slug with an outside micrometer, as the usual reloading caliper is never precise enough. Took a number of measurements, rotating the slug a bit for each, then averaged the results. Not the easiest measuring job, as the barrel is a 5-groove one, so the grooves/ lands aren't directly opposed to each other....hence my "judgement call" as to the exact dimension.

I intend to slug each of the cylinder throats, to get an exact read on their diameter(s), as well.

Not the first time I've slugged a barrel, if that is what you are wondering.

[Petrol & Powder]

Didn't mean to imply you measured it wrong, just wondering how you compensated for the odd number of lands.

[Groo]

Groo here
Is the gun accurate with Jackets---/Plated/Powder coat or Hi-tec?
The tight barrel will be "slower" than a looser one.
Don't worry about a few thousandth .355 to .359 as a lead bullet will size down without trouble.
If you need a tighter boolet, use a 9mm with a crimp groove [order-able on the web].
We did this in our Pythons when 9mm was the only soft /hp bullet with a jacket in a lighter weight. [ Pythons have "tight barrels" you know]

[bedbugbilly]

As stated already . . . just how are you measuring the barrel slug? Somewhere on this site is a good explanation on how to do it . . . if I remember correctly it involves using shim stock wrapped around the slug, using a micrometer (not digital calipers) and then subtracting the thickness of the shim stock (twice the thickness to allow for the wrap).

Rugers are known for tight throats and if necessary, I'd take DougGuy up on his offer if your barrel measurement proves to be off. Not questioning your ability by any means but with the rifling that Ruger uses, the measurement has to be accurately taken. A .001 "mis-read" can make a lot of difference.

Or . . . if you've figured out what works in it . . you can load 'em that way and mark the boxes so that's the only revolver you shoot 'em in.

Sounds like a nice revolver . . good luck with it and have fun!

[FLHTC]

If that is a "125 grain ammunition only" gun I wouldn't touch it because it has collector value.

[Petrol & Powder]

If that is a "125 grain ammunition only" gun I wouldn't touch it because it has collector value.

The Op stated it was made in 1994 in the first post, so that would be well after the short frame/cylinder 125gr only models were made. But you're right about the collectors' value of those models.

[Sean357]

After reading this I went and pushed a few of my HSM .358" LRNFP through my 93 SP101 chambers. One is slightly looser but all required a little push to get through. They do mic to .358" also. Haven't slugged the barrel yet, no sinkers that size.

[MtGun44]

"as the usual reloading caliper is never precise enough." good to see another person
that is aware of this. So many folks insist that calipers are as accurate as mics and
read them to .0005 because they can see the pointer is between the lines.

Bill

[bcp477]

Another update: (the final update?) :

I had a chance to get to the range yesterday, to run a definitive test on the SP101, with 0.356" dia. boolits. I sized samples of all 3 of the boolit types I have on hand (truncated cone/ 125 grain, RNFP/ 125 grain, DEWC/ 148 grain).....down from 0.357" to 0.356", using my Lee push-through die. 100 of each. Lightly re-lubed them with my usual mix of JPW and LLA. I loaded them over 3.5 grains of Bullseye - my usual target load. I also loaded 50 more of the DEWC type with 3.9 grains of Bullesye, as a SD load test.

Put simply, the results were all I could want. Shooting at 10 yards, I was able to regularly get 2" groups, some smaller... and I had no problem putting them into the "bull" (a square 2" on each side), with each of the loads. I am not up to the standards of many here, only pretty good....but this was a good performance for me. The SD loads I tested in rapid-fire, mostly point shooting mode, at 8 yards. I did have a few fliers, but nothing off paper (8.5 x 11" sheet with the 2" square as a bullseye)....but those were me, not the gun or loads. I did manage to tear a large hole, just to the left of the centre, with most of them.

No malfunctions whatsoever and zero leading.

So, I must say that I am satisfied with my SP101 and with the outcome. I have decided, for now, that I will alter nothing - just continue with 0.356" diameter pills for this particular gun.

Not that it matters, but I wonder a bit about my SP101. Is this a factory "mistake" ? A 9mm sized barrel, stamped ".357 magnum cal"...with tight cylinder throats (that happen to work out nicely with the right sized boolits), but yet chambered for 357 magnum cartridges. ?? I know that Ruger used to make a 9mm version of the SP101. I wonder if my barrel was actually made for those guns, but mis-stamped for 357 mag. Whatever. For the price I paid and the way things have worked out, I feel lucky to have the gun (and quite happy about it).

Regardless, this SP101 is a keeper. I am adding it to my carry rotation as of now - so I will have something as a counterpoint to the soul- less, ugly Glocks I usually carry.

Many thanks to all that took the trouble to reply and make suggestions. Don't ya love it when things work out well ? I know I do !

[Petrol & Powder]

Sounds like a good outcome. I do not know if Ruger used barrels bored for 9mm on their 9mm revolvers or just used .357" barrels. The cylinders obviously had to be cut specifically for 9mm but I always assumed they simply used .357" barrels. Judging from 9mm barrels I've measured, .357" isn't that large in the 9mm world.

[bcp477]

I certainly don't know myself (obviously). However, consider that the "normal" (or should I say "standard") groove diameter of 9mm barrels is 0.355". J-word projectiles for 9mm are, to the best of my knowledge and experience, sized accordingly. A 0.357" groove barrel might well show very poor accuracy with 0.355" 9mm projectiles. Further, the barrels for the now-discontinued 9mm version of the SP101 are listed as a different part # than the 38/357 ones. Of course, that could simply be the stamping on the side. It certainly is not always absolutely true that an undersized J-word will produce lousy accuracy - there have been exceptions. It is almost never an exception with cast boolits, however.

You are quite right, of course, about 0.357" being not large (or uncommon) in the 9mm world. It would be interesting to know what standard was applied by Ruger for their 9mm barrels.....for all of their guns offered in this chambering. Did they strive to be at or close to 0.355"....or did/ do they go "sloppy" with their 9mm barrels, as some other makers definitely do ? I don't know, but I have doubts that they would have simply used 0.357" barrels on dedicated 9mm revolvers. Doesn't sound right to me.

Of course, this is all only a bunch of speculation on my part.

I might try contacting Ruger - perhaps they might be kind enough to give me a read on this.

In any case, it doesn't really matter, after all. The gun is very nice....shoots very well....and I am as pleased with it as I can be. I just have to be sure to feed it what it likes....but that is no problem.

[charlie b]

Welcome to the SP101 carry group :) I love mine too.

I don't know about bore dia. One of these days I will shove a bullet down the bore to see how it fits. It does shoot well at 15yds, which is my limit for this little thing. As in, they will all go in the head or center of chest on the target during rapid fire drills. If I want to do target shooting I get out my other pistols.

[bcp477]

Thanks for the welcome.

I get what you are saying, Charlie. The SP101 is certainly no target gun. However, I am a big believer in as much practice as possible, with any gun I intend to use for carry/ SD. So I will shoot my SP101 alot. "Carry what you shoot....and shoot what you carry"......as I like to say.

[bcp477]

Well, I thought it over.....and finally decided to lap out the chamber throats, to allow for 0.357" boolits. My S&W shoots them beautifully, so I decided that I didn't want to have to keep up with two boolit sizes (for the two different guns). Being myself, rather than taking the "normal" route (I am NOT normal....so I've been told a million times)....I decided to work out my own way to do this.

Concentricity - that is the key. It is (obviously) completely undesirable to simply hog out the chamber throats by any old means, because one stands the very real chance of making the throats out of round or off-centre. So, what to do ? What I came up with is quite simple.

I took a spare 357 mag case and drilled out the primer hole. I threaded in a long machine screw, with a hex head. Next, I drilled a carefully centred hole part way through a 0.356" DEWC....and threaded that onto the end of the screw (which protruded about 1/4" from the mouth of the case. I filled the case with epoxy and screwed the DEWC in so that just a small portion intruded into the case mouth. So, what I made is a "lap" that perfectly fits the chambers....with a slightly oversized boolit on the end. Of course, I removed all traces of lube from the DEWC before using it.

I started with 400 grit grinding paste, working through to 600.....and finally 1200 grit....slowly lapping out the chamber throats. I used a cordless drill with a hex bit to drive the lap - slowly and carefully. The grinding paste was carefully applied only (a thin coat) to the chamber throats, NOT the chamber bores themselves. I liberally oiled the 357 case, so as to not disturb the surfaces of the chamber bores. After a couple of hours of careful lapping, working through the different grits....I now have chamber throats perfectly sized to accept lubed 0.357" dia. cast boolits (needless to say, I carefully measured the lap boolit and the "test" boolits....and selected ones as close as possible to my needs for this project). Measurements were taken with an outside micrometer, to the nearest 0.0001".

As a final step, after thoroughly removing all traces of the grinding paste, I coated the "lap" (case and boolit both) with a thin coat of Flitz...and polished the chamber bores and throats. They shine like mirrors now.

So, there it is. Probably not the "best" way to enlarge the throats, or even accepted practice, but, nevertheless, successful. I doubt that the chambers are out of round or non-concentric, as well. The final final step will be to get to the range - and thoroughly test 0.357" diameter boolits, as well as 0.356". The throats are now loose with 0.356", of course, but perfect with 0.357" ones....but the barrel hasn't changed, of course. So, I think that I have a pretty good shot that the gun will shoot the larger pills well. If not, well I can always continue with the 0.356" dia.

(Sorry for the poor quality photos, but I don't have a good camera.)



131122131123131121

[Petrol & Powder]

I completely agree with your desire to have one bullet for all of your guns. I'm a big; no make that huge, fan of simple logistics.
That's a cleaver way to ream the throats without a reamer. Seems like a fair amount of work but little cost. Sounds like you have the best polished throats to ever grace a SP101.
Curious how that will shoot.

[bcp477]

Here is (another) followup..... (a followup of the followup ?).....

Anyway, I've put about 250 rounds through the SP101, since lapping out the chamber throats. It now handles 0.357" dia. boolits with aplomb. However, it still likes 0.356" ones just fine. (That's good, because I have more than a thousand 0.356's to use up.) Lovely.....how versatile ! Knew I had a reason to love this SP !

On another, similar note..... I have grown very tired of hunting for another 3" Smith & Wesson K-frame (at an acceptable price), to compliment my superb M10-8. Just was having NO luck on that. So, truly liking the Ruger SP..... I started looking for another one. An older one, as I am not a fan of the new-fangled MIM hammers they use now. Today, I found one. A 3", 38 Special version (which they no longer make). Marvelous condition - perhaps better than my other SP101. Smooth trigger, too (well broken-in, perhaps - but it doesn"t look it). I didn't get it quite as cheaply as the other SP....but not bad. (I managed to haggle them down to $365.00, plus tax). This one is even older than my other one - the serial number indicates late 1989 (the first year of production). 26 years young !

Interestingly, the cylinder throats on this (new to me) 3" SP101 are not really undersized. A carefully measured 0.357" test boolit passes through each of the throats with apparently about the same clearance as with my doctored 2" SP101 cylinder. Same with 0.356" boolits. So, it looks as if I may not have to do anything to this one - just shoot and enjoy!

Don't ya love it when a plan comes together ? I do !

[Wolfer]

I just received my first SP101 on Monday. Weather is bad and I only had about 20 rds loaded.
While it's certainly not as good as my full sized guns at putting a boolit dead on I have to say I was surprised at how well it did shoot.

Pointability was also very good for me considering I pretty much only shoot full size SAs.
Im quite impressed with the little booger.

[TCFAN]

I bought my SP101 in 1989.Gave it to my wife for our 25th wedding anniversary.Since it was stainless steel it kinda looked liked silver.
It likes .358 to .359 boolits just fine. Never had a need to slug the barrel or cylinder.The little revolver has never offered to lead the barrel at all.Mine is the 38 special only version......Terry

[bcp477]

Perhaps QC was better with the early SP101's. I'd rather not believe that....but, who knows ? I've only had the two, as of now. My 1994 manufactured one had very tight throats (near 0.356"). My "new" 1989 manufactured one seems to have throats a bit larger than 0.357"...perhaps 0.358". Your 1989 SP evidently has throats even larger. By no means conclusive - as that is only a sample size of three.

Regardless, I really like the SP101 and I'm darned glad to have them.

[Petrol & Powder]

I bought my SP101 in 1989..........
Mine is the 38 special only version......Terry
Those early 38 Special only SP101's are very cool guns.

[Petrol & Powder]

bcp477, You have a great pair of revolvers. The SP101 is a solid gun and will give years of service. A 3" barrel SP101 makes a fantastic companion to your 2.25" model. A little more sight radius, very strong action and just about indestructible. I've always found the 3" barreled 38 caliber revolvers to be a great combination when one wants just a little more gun than a snub nose but doesn't want a full sized 4" revolver. With the right grips they can be easily concealed in a simple pancake holster. The SP101 is a bit heavy for it size and a 38 Special model will have very little recoil, making it a pleasure to carry and shoot! The stainless construction and compact size makes it an ideal trail gun as well. Good luck with those excellent little Rugers!