Posts Tagged ‘Diana smoothbore’

Diana 25 smoothbore pellet gun: Part 5

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1
Part 2
Part 3
Part 4

Diana 25 smoothbore
This Diana 25 smoothbore was made in World War II.

Today’s blog falls under the heading, “It’s not always a good idea to try everything.” Back when we were exploring the Diana 25 smoothbore airgun, we saw how incredibly accurate it was with certain pellets at 10 meters.

Diana 25 smoothbore JSB Exact RS deep-seated group
This 10-shot group of JSB Exact RS pellets was shot at 10 meters. The extreme spread measures just 0.337 inches between centers! It made us all wonder just how accurate a smoothbore pellet gun can be.

When I backed up to 25 yards, however, the groups opened up to between 2.5 and 3+ inches for the same pellet. Obviously, the pellet needs to be stabilized by both the high drag of its diabolo shape and by the spin introduced by rifling. Drag, alone, is not enough to stabilize the pellet.

One reader then asked me to try shooting round lead balls in the gun. Today, I’ll conduct that test for you.

Beeman Perfect Rounds
I shot Beeman Perfect Rounds, which are H&N Rundkugel but under the Beeman label. They weigh 7.7 grains, which is the weight of a medium-weight diabolo pellet.

The balls fit the Diana’s breech quite well, though one was slightly larger than the others. But the rest would not drop into the breech and had to be seated with the thumb — just as a pellet would. They did seat easily, however, and I noticed the gun’s powerplant seemed harsher than it is with pellets. I suspect the balls had less resistance than a pellet since they only touched the bore at their circumference, and there’s no rifling to engrave them.

Diana 25 smoothbore pellet gun round ball in breech
Except for one, each round ball fit the gun’s breech very well. Most stopped like this and had to be gently pressed into the bore with the thumb.

Testing at 10 meters
I began the test at 10 meters, thinking the gun was accurate at that distance with diabolos, so it should be accurate with round balls. I’m sure the reader who asked me to test round balls must have thought the same thing. But when I fired the first shot and could not find the hole on the target paper, I stopped shooting. Fortunately there were no new holes in the wall!

I then moved up to 12 feet and shot again — this time standing and using the door jamb as a brace. The shots now went to the bull at which I was aiming. But the group is hardly worth celebrating. Ten shots went into 1.166 inches at this distance. I’ve shot many BB guns that could do so much better than this that it’s embarrassing to consider.

Diana 25 smoothbore pellet gun 12 foot group round balls
Ten shots from 12 feet did make a group on the target, but that’s way too close for a gun like this! Group measures 1.166 inches between centers.

I guess the Diana 25 isn’t made to shoot round balls. If there was any doubt before, I hope this clears it up. I didn’t shoot any more groups because of how harsh the powerplant seemed to be. I didn’t see any reason to strees the mechanism more than I already had.

Darts?
Shooting round balls got me thinking about other types of non-pellet projectiles, and of course darts came to mind. I decided not to try them in this gun,as the powerplant is too powerful for them. It would bury a dart deep in wood, causing its destruction upon extraction. But that did give me another idea.

I was recently asked to conduct a retest of a gun I tested some time ago. Apparently, a blog reader felt my results were not typical of the gun I tested, so he called the manufacturer and they contacted me. That gun in question is a smoothbore, as well, and it’s a multi-pump, so the velocity can be controlled. I plan on testing darts when I test that gun for you.

Diana 25 smoothbore pellet gun: Part 4

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1
Part 2
Part 3

Diana 25 smoothbore
This Diana 25 smoothbore was made in World War II.

One thing that I really like about this blog is the fact that it affords me the opportunity to test certain things thoroughly. In fact, it somewhat forces me to test them thoroughly; because as I test and write, I think about you readers and all the questions you’ll have for me. So, I test to be able to tell you as much as I can about our mutual interests.

This Diana 25 smoothbore airgun that I’m reporting on today is one such subject. I get to work with a vintage airgun that’s very enjoyable, plus I get to test how well diabolo pellets stabilize and how accurate they are when they don’t spin. In turn, that reflects on the test of how the rifling twist rate affects accuracy.

I tested this airgun at 25 yards — a serious distance at which any and all airguns will show their true colors. And I used 10-shot groups, another tool in our growing bag of diagnostic accuracy tricks. Just one group can reveal significant findings, instead of five 5-shot groups or, worse yet, I shoot a bunch of 5-shot groups and show only the best one.

I was on the rifle range last week with a young man who was shooting a .257 Weatherby Magnum and trying to get it to group. He obviously knew what accuracy is because he wanted groups that measured under .75 inches at 100 yards. But he was shooting only 3-shot groups! That isn’t enough shots to make more than a good guess about a rifle’s potential accuracy. When I called him on it, he pointed out that he was pasting his targets to a backer at the same place every time, so all his shots would overlap on the backer as he changed targets. That told me he’s afraid of shooting large groups in case he makes a mistake. I’ve been there and done that, too!

Today’s test frankly frightened me, as I wasn’t sure the gun was accurate enough to hit the pellet trap all the time. I decided to use the JSB Exact RS pellets that performed so well at 10 meters. I seated each pellet deep in the bore with the Air Venturi Pellet Pen and Pellet Seater because the 10-meter test showed that was the way the gun likes it best. Let’s look at the two targets from that test before I continue.

Diana 25 smoothbore Beeman Devastator flush-seated group
The flush-seated JSB Exact RS pellets made a 10-meter group that measures 1.158 inches between centers.

Diana 25 smoothbore JSB Exact RS deep-seated group
The same pellets seated deep made this 0.337-inch group at 10 meters. It looks significantly smaller!

The test
The first shot at 25 yards did hit the target paper, but it was high and outside the bull. I checked it with a spotting scope immediately after shooting it. I also checked after the second shot, just to make sure it was also on the paper. It was, so after that I settled down and put 8 more shots into the target. In the end, they were all high and formed a group that measures 3.879 inches between the centers of the two widest shots. So that’s what the gun seems to be capable of, but I wanted another 10-shot group, just to confirm it.

Diana 25 smoothbore JSB Exact RS deep-seated group1 25 yards
The first 25-yard group of deep-seated JSB Exact RS pellets measures 3.879 inches between centers.

I lowered the simple rear sight elevator for the second group and fired 10 more JSB Exact RS pellets. The first shot hit the target in the black, so I knew I was okay to complete the 10 shots without looking. At the end, I had 10 shots in a 3.168-inch group. As far as I was concerned, those two targets demonstrated the accuracy potential of this smoothbore pellet gun at 25 yards with deep-seated JSB Exact RS pellets. But something nagged at me.

Diana 25 smoothbore JSB Exact RS deep-seated group2 25 yards
The second group of deep-seated JSB Exact RS pellets measures 3.168 inches between centers. It’s better than the first group, but it’s in the same general neighborhood.

How much worse would this gun shoot pellets that were only seated flush with the breech — in other words, loaded in the normal way? I had to test it. Once more, I shot 10 shots at 25 yards. This time, I was really scared because it looked from the 10-meter test that these pellets might not all hit the paper. Would this group be over twice as large as the other two — like the 10-meter group was? But the first shot went into the bull and the second one landed very close, so I calmed down and shot the other 8 shots without looking again. In the end, I had a 10-shot group that measures 2.421 inches between centers — the smallest group yet at 25 yards!

Diana 25 smoothbore JSB Exact RS flush-seated group2 25 yards
The first group of flush-seated pellets measures 2.421 inches between centers — the best group of the test!

What had happened? The gun was shooting more accurately at 25 yards with pellets seated flush, when it had clearly shot deep-seated pellets best at 10 meters? Not knowing what else to do, I shot a second group with the pellets seated flush. This time the group was larger, but at 2.957 inches it’s still the second-best group of the test.

Diana 25 smoothbore JSB Exact RS flush-seated group2 25 yards
The second group of flush-seated pellets measures 2.957 inches.

What have we learned?
This test demonstrates that diabolo pellets do stabilize from their high drag, alone. They do not require a spin to stabilize them because they all hit the target nose-first. But they’re not as accurate as they would be if shot from a rifled barrel. The spin introduced by rifling is important for accuracy, if not for stability.

A second lesson is this: Even though I shoot and record 10-shot groups, a single group may not be enough data. The difference in accuracy at 10 meters and 25 yards between deep-seated pellets and flush-seated pellets would seem to indicate that. Or it could just be that deep-seated pellets are more accurate at 10 meters, but flush-seated pellets are more accurate at 25 yards. If that’s the case (and I don’t know that it is), I have no idea of why it would be that way.

I think I need to test this gun once more and shoot 3 10-shot groups with each type of seating at each distance before we’ll know anything for sure.

Diana 25 smoothbore pellet gun: Part 3

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1
Part 2

Diana 25 smoothbore
This Diana 25 smoothbore was made during World War II.

What a topic to follow a twist-rate report — one about a smoothbore! Today, we’ll look at the accuracy of the WW II-era Diana 25 smoothbore airgun. This is a play-day for me because this gun is so non-finicky and trouble-free. It’s the way I wish all airguns could be. Just load and shoot. No special handling beyond the basic artillery hold, and no need to treat it like it’s a vial of nitroglycerin.

Shoot from 10 meters
I decided to shoot from a rest at 10 meters just because this is a smoothbore, and I had no idea of what results we would get. I hoped it would hit the paper with all shots. That would be good enough. But nothing beats shooting, so that’s what I did.

JSB Exact RS
The first pellet I tried was the JSB Exact RS, which is a .177-caliber favorite of blog reader Kevin and has become one of mine, too. It seems to work in most airguns, and it’s often one of the very best pellets. So, how would it do in a smoothbore?

I shot off a rest with the artillery hold. My off hand was back touching the triggerguard, but the gun is not muzzle-heavy. The first shot landed below the center of the bull — but actually at the point of aim, if a bit off to the right. So, the rear sight elevator was pushed forward to raise the sight. I didn’t care if it was hitting the center of the bull or not, but I wanted to keep the shots mostly inside the large black bull of a 10-meter pistol target because I could see the holes when they were in the white and distracted me.

The first 10 shots were fired with the pellet seated flush with the breech face. And the group turned out better than I had expected, though about as good as several readers had indicated they get from their smoothbores. It may not look that good to you, but notice how narrow it is compared to the height? That’ll become important in a moment. This group measures 1.158 inches between centers.

Diana 25 smoothbore JSB Exact RS flush-seated group
Ten JSB RS pellets in 1.158 inches, center to center, at 10 meters. The lone shot in the white was the first sight-in shot and is not part of the group.

Next, I shot another 10 rounds of RS pellets, but this time I seated each pellet deep in the breech with the Air Venturi Pellet Pen and PellSet. As before, the pellets all landed in the black bull, so it wasn’t until I walked down to change the target that I saw the group. Imagine my surprise to see a 10-shot group that could just as easily have been shot with an expensive target rifle! Ten JSB RS pellets went into a group that measured 0.337 inches between centers.

Diana 25 smoothbore JSB Exact RS deep-seated group
Ten JSB RS pellets seated deep in the breech made this 0.337-inch group at 10 meters. This is amazing for a smoothbore!.

You might shoot 5 shots some time and luck out like that, but 10 shots tell the truth. This airgun is very accurate at 10 meters, even though it’s a smoothbore. And it takes deep-seating the pellets to do it — at least with the JSB RS pellet. Now, I was curious. Would the two other test pellets show similar results?

Beeman Devastator
The second pellet I tried is one I don’t shoot a lot, but after it did so well in the Velocity versus vibration accuracy test I did a year ago, it has moved into the category of pellets I like to try when the circumstances are unusual. The Beeman Devastator is a hollowpoint that acts like a wadcutter at the same time. And a smoothbore is definitely unusual. The first 10 flush-seated pellets went into a group measuring 1.948 inches between centers. Not very good and more like what I’d been expecting from this airgun.

Diana 25 smoothbore Beeman Devastator flush-seated group
Ten Beeman Devastators didn’t group too well when seated flush with the breech. Group size is 1.948 inches between centers.

Now, it was time to shoot 10 Devastators that were seated deep in the breech. Would they also tighten up?

Well — yes and no. The 10-shot group of deep-seated Devastators measures 1.982 inches between centers, which is a little larger than the group of flush-seated pellets. However, 8 of those pellets did group into 0.691 inches. I would say that the deep-seating method still looks promising at this point.

Diana 25 smoothbore Beeman Devastator deep-seated group
Ten deep-seated Beeman Devastators made a group of 1.982 inches between centers, but 8 of those were in 0.691 inches. Deep-seating still looks good.

RWS Superdome
The final pellet I tried was that universal favorite — the RWS Superdome. The first group of flush-seated pellets was not that large, at 1.156 inches. If the deep-seating method held true for this pellet as well, it might beat the tight RS group when seated deep.

Diana 25 smoothbore RWS Superdome flush-seated group
Ten RWS Superdomes went into 1.156 inches at 10 meters. This is the best flush-seated group thus far.

A happy accident
As I was shooting the next group of Superdomes, I forgot to seat the second pellet deep and had to stop shooting the target. But the result on target was so dramatic that I photographed it, so you could see what happened. The deep-seated pellet is the high one and the flush-seated pellet is the low one. That shows more clearly than anything how deep-seating affects the shot.

Diana 25 smoothbore RWS Superdome mistake
The deep-seated pellet went high and the flush-seated pellet went low. This shows the dramatic difference deep-seating makes.

Deep-seated Superdomes
Then I got serious again and shot 10 rounds of Superdomes seated deep. They made a group sized 1.047 inches. While that’s only a little better than the same pellets seated flush, notice that these shots are centered in the bull much better. Not that I’m looking for that, but it’s a nice side benefit.

Diana 25 smoothbore RWS Superdome deep-seated group
Ten deep-seated RWS Superdomes went into 1.047 inches at 10 meters. It’s better than the flush-seated pellets.

What have we learned?
The first thing this test has taught us is that a smoothbore airgun isn’t that much of a disadvantage at 10 meters. I think the results of the RS pellets definitely call for another test of this airgun at 25 yards.

The next thing I learned is that deep-seating the pellets seems to improve their accuracy. Some improved more than others, but every pellet seems to have done better with deep-seating.

The last thing is that all of this shooting, all 63 shots, were fired with simple open sights. After some of the trauma you’ve witnessed me undergo in recent weeks to get some air rifles to group, this little Diana 25 seems to have breezed past all the big-name guns and taken the lead. I think that says a lot about what power levels are best for spring-piston air rifles.

Diana 25 smoothbore pellet gun: Part 2

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1

Diana 25 smoothbore
This Diana 25 smoothbore was made during World War II.

Oh, the things we think we know — how they vanish when we test! Today, we’re going to look at the Diana model 25 smoothbore that Vince sent me. You may remember in the last report that I was pondering when this airgun might have been made. Well, Kevin told me to look on the bottom of the butt, as the date stamp used to be there. Indeed it was! This airgun was produced in June of 1940, during the first part of World War II.

Diana 25 smoothbore date stamp
The manufacture date of the gun is stamped in small numbers on the bottom of the wooden butt.

The curiosity of a smoothbore is the extent to which the rifled barrel affects performance of the gun. I should have two identical airguns to test — one rifled and the other a smoothbore, but even then there would be subtle differences in their individual performance. I think it’s safe enough just to say what I expect from such a gun and then see what I get.

I would think a Diana 25 in good condition would give a muzzle velocity of around 625-650 with lightweight lead pellets. Remember — this is a .177. The last model 25 I tested was a Winchester 425 that was a rifled .22-caliber gun. That one gave an average velocity of 440 f.p.s. with 11.7-grain Hobbys, which I thought was a little slow. I expected about 525-550 from it with that pellet.

Preparation: Oiling the leather piston seal
To prepare for this test, I oiled the leather piston seal with about 10 drops of 3-IN-ONE oil. I just stood the gun on its butt and dropped the oil down the muzzle. By leaving it standing that way for a couple weeks while I was at the SHOT Show, the oil ran down into the compression chamber and soaked into the leather piston seal. I also oiled the leather breech seal at the same time so it would be pliable for this test. And I note that the gun now smells of burnt oil when it shoots, so everything was successful. We can be sure that the gun is performing up to the limit of its capability.

You may remember that Vince tuned this gun before he sent it. The mainspring inside was one he cut down from another rifle, so it isn’t exactly what the Diana had in it from the factory. But he took the spring from the harmonica gun that we suspect used to be a Diana model 27, so the dimensions of the spring are probably pretty close to original. We can guess and conjecture all day long, but a better way is to just shoot the gun and see what it does.

RWS Hobby
For the first pellet, I chose the 7-grain RWS Hobby. It’s a lead pellet that’s both lightweight and also a bit large, so it fits a lot of airguns very well. Since the gun was so well oiled, I actually shot three strings of 10, rather than my usual single string. The reason for this will soon be obvious.

The first string ranged from a low of 593 to a high of 627 f.p.s. The gun started in the 620s and progressively dropped in velocity as more shots were fired. That tells me it’s burning off some lubricant; and from the smell, I knew that it was.

The average for the first string was 609 f.p.s., but I believe that is too high. I think the dieseling caused by the excess oil boosted the velocity a lot. Immediately after the first string, I shot a second one.

I expected the second string to be slower and less variable, and I was right on both accounts. The average velocity for string 2 was 598 f.p.s., and the velocity ranged from 593 to 613 f.p.s. At the average velocity, the Hobbys produced 5.56 foot-pounds of energy at the muzzle. I don’t think the gun has settled down completely at this point, and I expect to see the average drop a few more feet per second as the gun continues to shoot. But there was still one more thing I needed to test.

Deep seating
I’d been seating the pellets flush with just my finger to this point. What would happen if I seated them deep with the Air Venturi Pellet Pen and PelSet? This time the average dropped to 594 f.p.s. and the range went from 584 to 621 f.p.s. What I make of that is that the pellet pen and deep-seating has little to no effect on the velocity of this rifle with a Hobby pellet. I think breech seating will be good, but I’m not going to leave it at that. I’ll also try shooting a group with the most accurate pellet seated deep, to compare to flush-seating.

Hobbys fit the breech tight and just a little of the skirt stuck out of the barrel. I expected them to increase in velocity with deep seating, but I guess this gun needs the extra resistance to generate all the power. It’s right on the cusp because deep-seating produces almost the same velocity, but the variability is greater; so I don’t think deep-seating is worth the extra effort.

Beeman Kodiak
The second pellet I tried was the heavyweight Beeman Kodiak. At 10.65 grains, the Kodiak is way too heavy for this gun. But that’s why I wanted to try it. I expect I’ll also try it for accuracy because who knows what it’ll do in this smoothbore?

After a couple shots that obviously dieseled, the Kodiak settled down to shoot in the mid 400s. The average was 461 f.p.s., and the range went from 443 to 470 f.p.s. At the average velocity, the Kodiak produces 5.03 foot-pounds of energy at the muzzle.

Just for fun, I also tried deep-seating Kodiaks that fit the breech very loose. This time the result was more positive. The average velocity dropped to 448 f.p.s., but the range tightened to between 439 and 455 f.p.s. That’s just 16 f.p.s., compared to the 27 f.p.s. spread for flush-seated pellets. I guess I’ll also try deep-seating Kodiaks in the accuracy test.

JSB Exact RS
The 7.3-grain JSB Exact RS dome was the last pellet I tested in the gun. These fit the breech even looser than the Kodiaks, but they gave an average 517 f.p.s. velocity with the tightest spread of the test. The low was 512 and the high was 525 f.p.s., so only 13 f.p.s. between the top and bottom. At the average velocity, this pellet produces 4.33 foot-pounds of energy at the muzzle.

Naturally, I tried deep-seating the RS pellet, as well. And to my surprise, the consistency grew even tighter as the average velocity decreased. The average was 504 f.p.s., but the spread went from 500 to 511 f.p.s., for an 11 f.p.s. difference. I guess I’ll deep-seat all the pellets during the accuracy test, as well.

Cocking effort.
The Diana 25 cocks like many vintage breakbarrel springers. It begins easy, then stacks toward the end. The max effort required is 19 lbs., which makes this a youth airgun in my book.

Trigger pull
The trigger is two-stage, and stage two is reasonably crisp. The first-stage pull is 1 lb., 8 oz., and stage two breaks at 5 lbs., 11 oz. It isn’t a target trigger in any respect, but it’s crisp enough that I know I can do good work with it.

Impressions so far
I’m finding that this smoothbore is, in fact, very similar to the rifled version of the Diana 25. The size, fit, trigger and feel of the gun give no indication that the bore is smooth. But this gun was made in 1940; and as such, has several differences from the Dianas of the 1970s that I’m used to. For starters, the sights are simpler, and there’s no rear base for a peep sight. Then, there’s the simpler trigger that cannot be adjusted.

I have to admit I’m very curious about how this gun is going to perform on target. I know it can’t be as accurate as a rifle, but I find myself hoping that it’s close. We shall see.

Diana 25 smoothbore pellet gun: Part 1

by Tom Gaylord, a.k.a. B.B. Pelletier

Announcement: Pyramyd Air has changed their Big Shot of the Week to the Big Shot of the Month, and the reward has been upped from $50 to $100. Guy Roush is this month’s winner of Pyramyd Air’s Big Shot of the Month on their airgun facebook page. He’ll receive a $100 Pyramyd Air gift card. Congratulations!

Pyramyd Air Big Shot of the Month

Guy Roush is the Big Shot of the Month on Pyramyd Air’s facebook page.

Diana 25 smoothbore
This Diana model 25 smoothbore is an old airgun!

This report comes to you courtesy of Vince, who sent me this Diana 25 to test for you. While I just recently tested a .22-caliber Diana 25, this one is quite different. It’s a .177-caliber smoothbore gun, and I think it’ll be the very first smoothbore pellet gun that I’ve tested since this blog began in 2005. There have been plenty of combination guns that shot both BBs and pellets, but to my recollection, they all had rifled barrels.

How pellets are stabilized
Diabolo pellets are so-named for their wasp waist and flared tail, which is hollow. They’re named after a juggling apparatus called a diabolo that a juggler works with a string. The wasp waist and hollow tail create lots of aerodynamic drag that both slows the pellet down and also keeps its weighted nose pointed forward. Because of how much the shape of the pellet affects its stability in flight, the question often arises whether the rifling in the barrel that spins the pellet is necessary.

I often see comments asking how much I think the presence of rifling affects the accuracy of such and such a gun, and I never know what to say. My best guess is that at close range, say 10 meters, a smoothbore is okay; but as the distance to the target increases, the smoothbore quickly falls behind the gun with the rifled barrel. Now, I have the means to actually test that, and we can all see for real!

The origins of this airgun
Vince acquired this gun recently, and I don’t think it was represented to him as a smoothbore. I think he even asked me if it was a smoothbore, and I told him to look for the word glatt somewhere on the barrel, as that would be the term they would use. Well, guess what? There are no words on the barrel of this gun, so what do I know? I think the early manufacture of this gun is the reason why things like being unrifled were left off.

In fact, other than the Diana logo and model number on the spring tube, there are no marks of any kind on this gun. There’s no serial number, of course, but that’s common for guns this old. But this gun goes even farther than most. Not even the caliber is marked, so I guess buyers either had to get that from the hang tag, or perhaps this gun was originally sold in Germany at a time when .22-caliber pellets were not common. I went over the entire barreled action with a tactical flashlight and a magnifying hood looking for other marks. It doesn’t even say Made in Germany, which leads me to think it wasn’t made for export.

This model is also a much earlier gun than the 1970s-era Winchester 425 (Diana 25) that I tested for you recently. Looking in the Blue Book of Airguns, 10th edition, I would say this is either a model 25 Improved that was produced 1933-1940 and 1950-1985, or it’s an even earlier model 25A. If I had to guess, I would put it in the earlier group for the lack of country of origin and caliber markings, plus the strange configuration of the breech (which I’ll show in a moment). It’s definitely a leather-seal gun with a direct-sear trigger. This will be the first direct-sear model 25 or 27 Diana I’ve ever tested, so I’m curious how well the trigger works. Naturally, it isn’t adjustable.

Diana 25 smoothbore trigger
The trigger on this rifle is old-school, with direct-sear contact.

What model is it?
I know it’s a Diana model 25, but that can be any of three different airguns. And here is a puzzlement. The overall length of the gun is 38.375 inches. That’s close to the 38.5-inch Blue Book-listed length of the earlier model 25A that was made from 1925-1934. The model 25 Improved is supposed to have a length of 39.7 inches, which is too much of a difference from the gun I’m testing. But the earlier gun is supposed to have a walnut stock, according to the Blue Book, and this one definitely has a beech stock. So, I’m thinking this might be an earlier gun and that the Blue Book might have overlooked the beech stock possibility.

Perhaps, the strange shape of the breech is a clue about which model it is. Instead of a conventional straight-cut breech with parallel sides, the action forks have strange-looking scalloped cuts on both sides of the baseblock —  and they really stand out.

Diana 25 smoothbore breech and rear sight
Here you can see the rather strange, scalloped breech shape. The rear sight adjusts for elevation, only.

As little as this gun is, it might look cheap at first glance, but all you have to do is break open the 15.4-inch barrel one time to feel the bank-vault quality that’s built into the locking detent. While the price was undoubtedly modest at the time, this is no cheap airgun. The beech stock is very slim, yet the pull is an adult 13.25 inches, making the gun pleasant to shoot for older children and adults, alike.

Vince went through the gun and tuned it before sending it to me, so I can’t comment on how the original powerplant might have felt. He installed the mainspring from the harmonica gun I reported on several years ago. A couple coils were cut to make it fit, and now the rifle cocks with great ease.

I’ve shot the gun several times just to familiarize myself with the operation. It shoots with the same authority that a more recent model 25 has. The buzzing is very low, which I must attribute to Vince, since I can see his work through the cocking slot. I imagine the original gun was probably a little buzzier.

The front sight is a tapered post that’s dovetailed to the barrel. The rear sight is leaf-type sight that’s adjustable for elevation only. It’s also dovetailed to the barrel.

Diana 25 smoothbore front sight
The front sight is a tall, tapered post.

Test plan
My plan is to test this gun exactly like I would test any airgun. I’ll check the velocity next, and then the accuracy in Part 3. If I can find an accurate pellet when I test at 10 meters, I might do a fourth test from 25 yards. Everything will be done with iron sights, as there’s no convenient way to mount a scope on the gun. But I think I proved with the El Gamo 68 that I can shoot iron sights at 25 yards.

Future plans
Once the gun has been baselined for accuracy, I plan to use it as a testbed for other tests with diabolo pellets. Finally, we’ll have a basis for comparison, rather than just guessing what might happen. Between this airgun and the Twist rate test, we should wind up with a pretty good idea of what rifling is doing for diabolo pellets.

The “pogostick” repeater

by B.B. Pelletier

Announcement: Here’s this week’s winner of Pyramyd Air’s Big Shot of the Week on their facebook page. He’ll receive a $50 gift card.


Shariq Bukhari with his Diana 350 Magnum on his farm.

Before we begin, it’s time to make all of you aware of an anti-gun movement taking place in California right now. California Senate Bill 798 will change the current code so that all airsoft guns and BB guns can no longer be black. They will have to be completely clear or all red or all blue or all green.

Even if you don’t live in California, this bill has the potential to affect you. Many of these guns are imported from China, Japan and Taiwan, and their ports of entry are in California. If the law passes in its current form, it will impose fines on those who distribute these guns if they aren’t clear or brightly colored. If this passes, it will embolden legislators in other states to pass similar bills — and perhaps even more stringent ones. To paraphrase an old saying, as California goes, so goes the nation.

To read more about the bill and what you can do about it, click here to read our facebook page, which has additional links to the bill in its current form, other web pages about the bill and videos about it.

Now, on to today’s blog.


Have you ever seen anything like this? It’s a single-shot breakbarrel modified into an underlever repeater.

Blog reader Kevin asked for this report, but several other readers have also indicated their interest. It was Kevin who also gave it the nickname pogostick. It’s really a homemade repeating spring-piston airgun that was created by a mad-scientist airgunner more than 30 years ago.

In fact, almost the only historical information I have on the airgun is that it was bought over 30 years ago by the man I bought it from. It was always his plan to get it working again; but now that he’s in his 80s, he has other priorities and was open to an offer.

I visited him just before the Malvern airgun show, and I was in his gun room looking at both firearms and airguns this past April when the odd shape of this long gun attracted my attention. The owner brought it down and handed it to me, telling me a brief tale of how he came to own it. Like me, he was attracted to the strange mechanism, and I think after you see it today you’ll feel the same.

Description
The airgun began life as some model of a Diana breakbarrel, probably an old model 27. The Diana trademark and name can just be made out on the spring tube, but I haven’t been able to pin down the exact model yet. I’m guessing it’s a model 27 because of the size. Of course, I’m referring to the pre-war 27 that was made without a forearm, as most pre-war Dianas were.


No doubt who made the gun originally. The model will be harder to determine, though.

And yes, it was originally a breakbarrel. You can see that the person who modified the gun started by brazing the breakbarrel joint shut and grafting in a new mechanism.


The pivot bolt was brazed in place.


Right side of the pivot bolt.

After brazing the joint, it appears to me that he cut the compression tube and spliced in an action block that houses both the repeating mechanism and the magazine. You machinists will appreciate the level of skill it takes to cut a spring tube, graft in a block of steel, then reattach the front of the spring tube and keep the whole assembly in perfect alignment. It has to be aligned pretty well because the air transfer port in the back part of the tube has to shoot air through the sliding magazine and into the rear of the barrel that’s grafted on. If my descriptions don’t explain it well enough, the photos will.

Then, he had to create a separate underlever mechanism, find a way to attach it to the gun and rig a link that connects the underlever to the piston while bypassing the new block he’s grafted in. Once again, the pictures show this very well.


When the underlever cocks the gun, the cam on the lever presses the steel shaft straight back. It acts on one of the three pins inside the action. That detail is shown later. The straight shaft is missing a spring to return it to the front when the cocking lever goes back to the stowed position.

Now, we come to the difficult part! This mechanical genius, and I mean that as a compliment, devised a way for the spring-loaded magazine to advance every time the gun is cocked. That’s where the pogostick look comes from.

To the right side of the action, he attached a steel magazine housing for the cylindrical magazine that holds 6 pellets. The magazine fits into the mag housing under spring pressure, and an escapement mechanism of two separate pins allows the mag to advance to the left, indexing the next pellet each time the rifle is cocked. I call it an escapement mechanism, because a watch escapement is the closest thing I’ve seen to it. One pin drops down out of the way when the underlever is retracted all the way during cocking. That allows the mag to advance to the next pellet hole. When the underlever returns home, the pin that dropped away pops back up to lock the mag securely. A spring that is missing from the mechanism’s shaft takes care of moving the shaft.

The other pin behind this middle pin must also move for the mechanism to work properly, but I haven’t figured out how it works yet. It’s spring-loaded, so maybe that alone is all it needs. There’s a headless screw in the front of the mechanism to keep the cylindrical magazine on its track.

The magazine has detents cut into a track in the base. These detents are angled, so the pins that work the action can slide over them under spring pressure when the action is working.


The magazine is shown out of the gun. The coiled spring and steel guide keep tension on the magazine when the gun is cocked.


A look at the operating escapement mechanism. The front pin is solid and is just there to guide the magazine in its track. The middle pin is connected to the straight shaft under the gun and retracts when the gun is cocked, allowing the magazine to advance to the next pellet. The rear pin is under spring tension alone, and I’m not quite sure of its function.


This track in the bottom of the magazine keeps it on track. I took the photo on this angle to show the detail of the detents. You can see how they’re sloped to permit the magazine to advance under spring tension every time the gun is cocked and the middle pin drops out of the way.


The gun came with these parts in a plastic bag. Those two pins are obviously for the escapement mechanism, but I don’t know where the spring goes. It’s too large for the escapement shaft.

The gun is 42.25 inches long. A Diana model 27A that was made from 1936-1940 is 41.3 inches long, so this could be made from that gun. But there’s no way of knowing for certain without a lot of comparison with similar Dianas that are in original condition. This rifle weighs 7 lbs., 4 oz. with the magazine and spring installed. The magazine itself weighs 6.2 oz., being made of solid steel bar stock.

At the current time, the magazine is outside the gun and will not install because the inner spring-loaded pin stands too tall and will not compress out of the way. My buddy Mac thinks the mag is supposed to be captive and has to be installed from the right side of the gun; if so, that’s a cumbersome way to reload a repeater. I don’t think the guy who could dream up this contraption would leave a detail like that unaddressed.

The gun cocks with 22 lbs. of effort. The sear does catch. Since the magazine cannot be inserted, there’s no way to shoot a pellet. The trigger does release nice and crisply, though. There isn’t the hint of an anti-beartrap mechanism, so the gun can be uncocked.

But wait, there’s more!
Our mad scientist wasn’t satisfied just building this impossible mechanism. He also made both the front and rear sights. While the folding rear sight is crude compared to the rest of the work, it’s an aperture that adjusts for both windage and elevation, though the elevation adjustment is nothing more than a sliding part held by friction. It’s an extremely tight fit, so once you get it to the correct positio it won’t shake loose.


A simple yet quite effective adjustable peep sight. It adjusts in both directions and also folds flat.

The front sight is a tall, slender pin in a dovetail. The bead on top is small enough to do careful work, though I think the designer’s mind was more focused on getting the gun to work at all rather than on accuracy.


A tall, graceful front sight with bead. This is also homemade.

I cleaned the barrel, to see if there’s any rifling. As near as I can tell, there isn’t. This is a smoothbore. The Blue Book of Airguns, 9th edition, says the model 27A did come as a smoothbore. The sights are nice, but the gun doesn’t warrant them. The difference between a gun and a rifle is the presence of rifling, so this doesn’t qualify as a rifle.

Harmonica gun
Although I call the gun by the name Kevin gave it, the correct name for a repeater of this kind is harmonica gun, for obvious reasons. They exist as black powder firearms, as well as other airguns like the IZH 61 and certain target air pistols.

What to do next?
I bought this gun because I was compelled to own it. I just had to be able to examine this mechanism closer, to report on it and maybe even get it working again.

Yeah. Right!

Well, I’ve examined it as far as I can without disassembly. Then, I took a long, introspective look at my schedule and realized that this is as far as I am probably ever going to go. Contrary to popular belief, I don’t sit around all day with screwdrivers, just taking apart airguns for my pleasure.

Like most of you, I would enjoy knowing if this gun can be made to work and would love to be able to give it a complete test with velocity and accuracy. Then, we’d really find out if our genius knew what he was doing. Short of voting eight days into a week, I don’t see it happening any time soon.

So, maybe in 20-30 more years, one of you younger collectors can add it to your collection.

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