Rast & Gasser M.1898


Designed in Ottakring, a district of Vienna, around the end of the last century  the M.98 was a technically advanced SA/DA revolver with some unique features. But it didn’t have a long service life as the dawn of the semiautimatic pistols was about to break. Though a rugged and reliable design, the M.98 was additionally hampered by its weak performance, the “8mm Gasser” cartridge, roughly equivalent to a hot .32 ACP or a hot .32 S&W long.


Field Strip

To field strip the M.98 you dont need any tools.

To remove the cylinder you pull down on the locking latch of the cylinder base pin below the barrel and turning it 90° left or right (doesnt matter which way). Now the cylinder base pin can be pulled out, pulling forward towards the muzzle and parallel to the barrel. Next open the loading gate and let the cylinder drop out. This is probably all you need for a field strip, as the parts to be cleaned can be accessed now.

To further disassemble the gun, pull the rear of the trigger guard forwards (in the direction the barrel points) thereby squeezing the trigger gard. This releases it from the back part of the frame, and you can see that it is hinged on the frame with its front part.

This operation releases the forward lock of the sideplate that covers the left part of the frame. The sideplate is hinged vertically on the back of the frame. Lay the gun on a table, muzzle pointing towards the left. Now you can open the sideplate like a book, by pulling on its left end and flipping it open towards the right.

Next you can remove the sideplate if needed, it is held by a large screw on the backstrap of the frame, this screw can be removed easily.

After the sideplate is opened or removed you can take out the left grip half by holding it on its upper end and tilting it towards you. The grip is held in place only by the sideplate (now removed) and two small studs on the lower part of the grip frame.

Full Disassembly

For the next steps you will remove the inner parts, so this is the full disassembly now. First you have to remove the V-type flat spring which serves multiple purposes: it is the hammer spring, sear spring, hand spring, and trigger return spring, all in one piece. The only other spring needed is the loading gate spring, a spring in the form of a flat “L” and the trigger guard, serving itself as a spring.

To remove the V-spring you need to remove the hammer link first. To remove the hammer link, you need to take the tension out of the hammer link. This can be accomplished by releasing the hammer tension, putting the hammer in its most forward position, then compressing the  V-spring by wedging a piece of wood against the frame, a wooden chopstick works perfectly here. Now the hammer link will be movable and you can pull it out of its notch in the V-spring. After this operation the V-spring can be gently further compressed by finger force – if you have strong fingers – or by the chopstick and pulled out of the frame upwards (if the gun is still flat on a table). You can see that the V-spring has a small lug where it is pinned in a hole in the grip frame. This tiny lug prevents the spring from slipping out of the frame. Be careful as the force of the V-spring is considerable.

After removing the V-spring the other parts can be removed simply by pulling them out. First tilt the hand to the right and pull it out of its notch in the bar. Then remove the bar, next remove the trigger and then the hammer. Now the frame is empty besides the L-spring for the loading gate. Unless the gate gives you problems, there is no need to remove that spring. It can be easily accomplished by removing the holding screw, the prying out the spring from its recess in the frame. But getting that spring back in is a different story.

As usual: assembly is in reverse order. The L-spring might give you a fight, also replacing the V-spring takes some repetitions, as the force of that spring is considerable AND you have to put its lug into the hole in the frame and at the same time compressing the spring. Chopsticks help here again.

Trigger Job

Getting a better trigger on a revolver with a V-type mainspring is not much fun unless you are an experienced (hobby) gunsmith.There are several schools of thought how to weaken a flatspring. In my personal opinion it is best to flatten it, making it thinner in the direction it serves as s spring. But you have to do this equally over the whole springs length. If you create a spot thinner than the rest it will have much more stress there and eventually break at that spot. So grinding / stoning a slightly curved flatspring uniformly thinner across its full length is tricky. Alternatively you can make the spring thinner by narrowing it. In this way the chances to create a weak spot are lower. But the thinned spring might not fit snugly anymore, as these springs are often only held by pins. A thinned spring can move up and down on the pin, creating uneven spring tension. You can see why wire springs are the norm today. They are standardized and you can weaken them much easier.

I decided to leave the mainspring as it is and concentrate on the trigger and sear interaction. This has the drawback, that the double action trigger pull will stay as it is, and it is stout to say the least. I have no way to measure it, but it must be in the 15-20 lbs range. Unusable for any competition, but very safe.

Working on the hammer notch is a delicate thing. I decided to go the safe way, just trying to get a full engagement area of hammer and sear by careful stoning with a FF india stone. To see how well these 2 parts interact take a felt tip marker (sharpie) in a well visible color (I use purple, dark blue and black work nicely, too) and cover the engagement areas liberally with ink. Assemble the gun and dry fire 2-3 times. Disassemble and look where the purple is gone. Stone only these areas carefully down, very carefully. Again use your marker, color areas, assemble, dry fire, disassemble, check where the paint is off, stone there. You will have to repeat this 5-10 times until you have the maximum engagement area of hammer and sear. In the meantime you will also be very experienced in assembly/disassembly, especially handling the stout mainspring.

I decided not to cut the hammer notch any shallower, I just made it square and maximized the area where these 2 parts rub against each other. The result is a surprisingly clean trigger break without any creep, but with approximately 4 lbs. Not a competition trigger, but good enough for me. Going any lighter would require stoning down the notch what I think is not needed.

Cartridge and Reloading

Getting factory ammunition for the M.98 is possible, but expensive like crazy (90€ for 50 cartridges currently); to make things worse, there is only one factory worldwide left that will produce the original load: Fiocchi in Italy. They produce a couple of thousand rounds every couple of years, the ammunition is barely available if you do not have good connections to historica clubs.

Also ammunition quality is bad I’ve been told, as they produce them according to the original (pre-CIP?) standards that require a very thin brass case that will often crack at the case mouth at the first shot and a nominal .319″ bullet (which is way too small in diameter for most worn-out leftover M.98s, see below).

So you begin to think seriously about reloading. Load data for the 8mm Gasser is scarce, the best source currently can be found here 8mm Gasser (the page talks about 9mm Gasser, but it is for the 8mm Gasser, fear not). Note that the load data given there is for reproducing the actual ammunition in terms of performance. This heavy loads together with current flimsy brass explains the case mouth cracks. The original 1989 was not comparable to a .32 S&W long (to that power I load my reloads), it was more like a .38 Special in performance.

What I did is first slug the bore of my antique for its diameter. Using Cerrosafe (recommended!) I got – after the 1 hour delay – my reading of .327″. This was quite a surprise, as the M.98 has a factory bore diameter of .319″. So whatever happened to the gun, its bore diameter is way oversize now.  Corrosion? Fabrication fluctuations during WW-I? Who knows.

I need to repeat this, and for that purpose I have now acquired a brand new Mitutoyo caliper which is capable of reliably reading 0,0005″. Unless you use a high quality caliper forget measuring to .001″, a 10 to 20 € Chinese built caliper will only work to 0.001″ if you measure differences, it will not be reliable with absolute values at all!

Getting bullets that would fit a .327″ and be in an acceptable weight range (less than 150 grains) could be a challenge. So I used the good old Minie Ball trick: I had very soft lead hollow base wadcutters of .312″ diameter. This is clearly way undersized, I can easily push that bullet into the M.98´s muzzle by little force of my fingers and drive it effortlessly all the way through with a chopstick. It doesn’t bind at all, nor does it rotate, and after being pushed through the full length of the M.98 barrel the .312″ bullet had no visible engravings of the rifling.

But when powered by a nominal charge of 1,8 to 2,0 grains of Hodgdon TiteGroup I assumed it should behave like a Minie Ball and expand due to the hot and powerful gases working on the super soft and hollowed bullet base and gain some additional thousands in diameter – at least in the base part of the bullet where the bullet walls are very thin.

First shootings with handloaded .32 S&W long 100 grain lead hollow base wadcutters of .312″ diameter (manufacturer: H&N, Germany) that I had produced a year ago for my ISSF center fire gun (a Hämmerli 280) confirmed this: surprisingly good accuracy and nice, sharp round wad cutter holes (no tipping of the bullets). I really was happy with the performance the .32 S&W longs showed without any tuning of load / length / crimp / powder type / etc. Just lucky? Maybe. Nevertheless I will experiment with other loads, too, as the 2,0 grains with a 100 grain bullet are really weak, they were designed for a target handgun. Mayby more powder will make the hollow base act more like a Minie Ball – but then, maybe not. After a nice trigger job (see here) which is definitely the first step in any precision tuning I will try again and report here.

Update: using starting load of 1,8 grains of Hodgdon TiteGroup and going upwards in 0,2 grain increments things didnt get better. 1,8 and 2,0 grains showed the same good performance, but with 2,0 grains some of my ages-old and probably tens of times reloaded but very thick-walled .32 S&W long cases ruptured lengthwise starting from the case mouth. This shows that a “8mm Gasser” is not identical to a .32 S&W in terms of case diameter. The 8mm Gasser cylinder bores are obviously a bit larger than an old .32 S&W case can elastically handle with a more “stout” load (if you can call 2,0 grains of TiteGroup a stout load at all).

From 2,2 grains onward more and more cases ruptured and accuracy declined very rapidly. With 2,6 grains all cases were dead after one shot and the bullet holes ware all over that target. So lesson learned: 1,8 is good for accuracy and seems to leave the case intact. Case settled, target load identified.

P.S.: I went down to 1,7 grains of Hodgdon Titegroup and won my club championship with the M.98 🙂

P.P.S: Went up to 1,8 again as there were some weak ignitions.

Front Sight

The factory standard front sight was too short or my used bullet weight (100 grains) and speed was too low, anyway the gun shot way too high. To cure this you need a new front sight that is larger (taller).

So I removed the tiny front sight from the M.98 which is fortunately fitted with a dovetail by driving it out with a brass punch. Not a big deal, it went out right away without any help from WD40 or such.

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Then I took an old thick nail, cut it squarely off and filed in a rough dovetail. I drove it by hammer force into the empty front sight dovetail of the M.98. This works as the M.98’s barrel is steel and the old nail is soft iron. So you dont hat to be very precise in filing the dovetail, it hast to be just close, the rest is adjusted by a trusty old hammer. Now using a file with a safe edge I slimmed the nail to form a tapered post and cut it off with a hacksaw. Filing it to the correct length (calculated) and width (estimated) resulted in a usable front post.

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For determining the correct width and height I made several trips to the range, afterwards adjusting the post with a file according to my notes written on the range. I ended up with a post of perfect width, but was a bit too aggressive with the file on one time and the front sight was too small again. Now I have to start over, but as this is not complicated work, it´s not a major issue. Only the range trips needed to determine POI are annoying, I´m now planning to set up a portable vise construction that I can use directly on the range.

Update: I just built a new front post, again from the old nail. This time I had the old front sight to measure and so it was a bit quicker to file the new one. This time it is way taller than the old one and shoot very low. I will devise a portable fixture for the gun and take it to the range, together with a file.