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Slavia · Moderator

INTRODUCTION

I recently got the opportunity to test some new pellets. Prospero U.S.A. was kind enough to send some of their 12.8 grain field pellets, so I put them through the wringer. I tested them along with 9.3 grain RWS Supermags and 10.5 grain Crosman Ultramags to put their performance in context with familiar heavier pellets.

I have no connection with the good people at Prospero, other than agreeing to do this test. My bias going in was positive - I’m always hopeful over the opportunity to find something new that works.

PROSPERO L.L.C.

Prospero L.L.C. (Note 1) and its counterpart Prospero U.S.A. (Note 2) came out with a pellet holder late in 2010, and introduced a unique cylindrical .177, 12.8 grain pellet in July of 2011. They are developing an 8.17 grain pellet of similar design in that caliber, and also offer lead BB‘s. My sample came from Prospero U.S.A. in Washington state, but was labeled “Made in E.U.” (European Union). The telephone number at www.prosperoco.com has an Estonian country code. Videos promoting their pellet holder (Note 3) and manufacturing process (Note 4) are on YouTube and can be linked from the websites.

Prices from Prospero U.S.A. are $3.50 U.S.D. for the holder, $11.00 for the holder with 150 pellets, and $10.00 for the holder with five hundred 8.17 grain round balls. European prices are €2.90, € 8.00, and €7.00 respectively.

THE PRODUCTS

The pellets arrived intact and well packaged, both inside the shipping box and within the pellet holders. (Fig. 1)

I inspected each of the pellets in one container and found no visible defects. There were no lead flakes or dust visible in the container. (Fig. 2)

The pellet holder is designed to hang from a belt or be fastened to a buttstock. Unlike some plastic pellet boxes that I’ve used in the past, this one actually works. It opens wide enough to allow easy access all the way to the bottom, yet not so wide that it risks spilling. It can also be opened completely for use on a bench. I found it more useful to hang it from the corner of a front pocket than from the belt. (Fig. 3)

Prospero’s video suggests that the container design will prevent spills in the event that it falls, so I dropped it. Falling from belt height it sprang open on impact and sprayed all over. Happily I had substituted cheaper steel BB’s for the pellets. That aside, I like the holder. (Fig. 4)

The pellets themselves are reminiscent of proprietary Sheridan .20 cylindricals, but with slightly more curve to the sides and a shallow hollowpoint “dimple.” (Fig. 5) They are smooth and gray, but don‘t leave the fingers dirty. There is a slippery feel that suggests some kind of lubricant. Instead of a thin skirt that flares under pressure, they have a driving band at the rear. Like the Crosman Ultramag, the Prospero pellet‘s rear measures 102% of the nose diameter. The RWS Supermag is more flared at 107%. Prospero promotes the pellet as being an exact 4.50 mm, and the average measured head diameter was right on at 4.499 mm. The pellets are lead with 3.5% Antimony. (Note 1) (Fig. 6)

With that average head diameter and an average length of 6.253 mm, the Greenhill (Note 5) formula suggests an optimal barrel twist rate of one turn in 19.” This is in the same range as the Crosman pellet at 18” and the RWS pellet at 20.”

The nominal weight of these pellets is 12.8 grains, but they averaged only 12.6 grains. Both the Crosman and the RWS pellets averaged the same as their nominal weights. The Prospero head diameters averaged 4.499 mm, skirt diameters 4.603 mm, and lengths 6.253 mm.

I found two things about this pellet to be ergonomically awkward. First, without corrected vision the cylindrical shape made the front and back appear similar. I found it necessary to put my bifocals on between shots - no problem if you’ve got younger eyes. Second, I have a habit of snagging the head of domed diabolo pellets in the breech and then rotating them in. The Prospero pellets have to be fed straight in, coaxial with the bore. Again, no problem if you’re using a bolt action with a probe to feed them into the breech.

TESTING METHODS

Prospero indicates that the pellets are for P.C.P. rifles and springers over 12 F.P.E. (Note 1) I don’t own a P.C.P., but my Crosman G1 meets the 12 F.P.E. criterion. The rifle is equipped with a Crosman A.O.3-9X32 scope. (Fig. 7)

Measurements were taken with a micrometer (+/-0.001 mm), a digital caliper (+/-0.001“), a household “weather center,“ a Shooting Chrony F-1 (+/-1 F.P.S.), and a Lee beam balance (+/-0.1grains). Sample sizes were ten (10) pellets, except for five round target groupings. (Fig. 8)

Testing was done outdoors at 66 Deg. F., 73% relative humidity, 29.5mm Hg, with a slight overcast. Wind was estimated at a steady 5 M.P.H. from 75 Deg. relative to the sight line. The range is located at 1120’ A.M.S.L.

CONSISTENCY

Linear Dimensions - All three brands had nearly the same variability in head diameter, skirt diameter and length, with standard deviations around 0.020 mm. The Prospero pellets were clearly superior in the head diameter dimension with a S.D. of 0.008 mm.

Velocity - The RWS pellets had the highest kinetic energy, probably because they were the lightest and closer to the “sweet” spot of the power plant. The Prospero pellets equaled the kinetic energy of the Crosman pellets, had less variability, but had a very “harsh” feeling shot cycle.

The Prospero pellets averaged 667 F.P.S., with a standard deviation of 4.36 F.P.S. (12.4 F.P.E.). The Crosman pellets averaged 722 F.P.S., with a S.D. of 9.03 (12.3 F.P.E.). RWS averaged 796 F.P.S. with a S.D. of 4.06 (13.1 F.P.E.).

Weight - Both the RWS and Crosman pellets averaged the same as their nominal weights, with standard deviations of 0.078 and 0.046 grains respectively. The Prospero pellets averaged 12.6 with a standard deviation of 0.162 grains, which is lighter than nominal with much more variability.

ACCURACY

Three five-round groups were shot from a bench at 25 yards with each brand of pellet, using a sandbag rest. The “X” and “Y” coordinates of each shot were measured with a digital caliper, and the calculations were done with a computer spreadsheet. Group diameter (maximum dispersion), group center, and mean radius (average distance from center) were calculated. Figures shown are for the best of each brand’s groupings. None of the three brands showed evidence of “key holing,” and none dieseled.

The mean radius for the Prospero pellets was 0.47,” and the group diameter was 1.56.” This was the largest grouping among the three brands (Fig. 9).

BALLISTIC COEFFICIENT

Two groups of five rounds were shot at 25 yards (zeroed) and then at 50 yards to measure pellet drop. The measurement was taken from group center to group center. Chairgun 3 v.1.0.4c was used to calculate a B.C. of 0.0131 at 667 F.P.S. (12.6 F.P.E.). Compare this to Chairgun’s data base putting Crosman at 0.0250 and RWS at 0.012. (Note 6) The nose of the Prospero pellets is more like the wadcutter design of the RWS Supermags, and the B.C. reflects it.

PENETRATION

Shots were fired into bars of Dial Gold soap at a distance of 2“ from the muzzle. None of the three brands showed significant mushrooming, although the RWS Supermags did shorten a bit (and penetrated less). Penetration was similar for the Prospero and Crosman pellets at slightly less than 3.” Note the wider channel at the entrance where the RWS and Prospero pellets “hammered“ the soap, while the round-nosed Crosman pellet pierced it. (Fig. 10)

CONCLUSION
The pellet case is well designed and worth the $3.50 being charged. The pellets themselves are beautifully made and carefully packaged, but shot harshly in the G1. Their performance in that gun was inferior to more readily available (and much less expensive) alternatives.

Still, every gun has its preference, and these pellets might be just the thing for your gun. While Prospero’s websites say the pellet can be used in +12 F.P.E. springers, the inference is that it was designed for P.C.P. guns. I have no interest in the Prospero lead BB‘s, but I would like to see the 8.17 grain pellets when they become available.

NOTES

1http://www.prosperoco.com/
2http://www.prosperousa.com/
3http://www.youtube.com/watch?v=AVNCOl8CrO4
4http://www.youtube.com/watch?v=2de1DECtQfc&feature=related
5http://kwk.us/twist.html
6http://www.hawkeoptics.com/apps/chairgun-pro.html

rsterne · Moderator

Excellent write-up.... I would like to try the 12.8 gr. Prospero pellets in a PCP up at around 20 FPE.... they could be interesting providing they group well....

Bob

Alstone · Moderator & Site Supporter

Seeing as Slavia has wrote an excellent report on Prospero pellets there is not much point me repeating things not that it would be as comprehensive a report has his, so here is my findings using Prospero 12.8g heavy pellets in .177 cal.

The Prospero Field Line pellets to test were what they call “Heavy Rifles” which is springers 12flb and over and PCP rifles, the pellets themselves are 0.83g / 12.8gr in weight, and are made of lead alloy with antimony content of 3,5% which gives them high penetration ability. The pellets are shaped along the pellet axis and calibrated. The unique shape of the pellets is specifically designed to reduce the influence of wind on the pellet trajectory. Pellets are designed for long distance shooting to increase accuracy.

To test these pellets I am using an Air Arms TX200 HC .177 and a Air Arms S410 Classic also in .177 cal.

Using the 25m range at the club I started off with the TX this is shooting at 11.5flb the Prospero pellets were a bit tight on loading but fired with no problems. I did notice that the TX kicked back a bit more than usual, this is probably due to the fact that I usually shoot Between 8.4 & 10.5g pellets and these were tighter in the barrel and weighed 12.8g.

Shooting 25m from a bench I was getting 10mm groups a 6mm low on the bull when I normally get 6mm groups using 8.4g AA fields, I put this down to the extra kick and weight

On the 40m range the grouping was 20mm and 20mm low, where I think my TX was running out of steam due to the pellet weight.

The AA S410 was FAC rated and running about 16flb, once again the Prospero pellets were a tight fit. On the 25m range the grouping was 6mm with no drop, moving to the 40m range 10mm groups and 6mm drop. The fps was between 730 -740fps.

Shooting at some knockdown targets later on these pellets certainly deliver a hefty whack on the target, in some cases dinting the metal, but this was only with the AAs410.

Next I went to a farm where I go ratting and pigeon shooting, for this type shooting I use Bisley Pest Control 8.9 g hollow nose pellets the Bisley performed excellent as normal, but the harder Prospero’s just passed through and unless you got a head shot the rat seemed to go on it’s merry way, where as with the Bisley the pellet head would splay out and do a lot of damage.

The boxes they came in are quiet good for carrying in the field and are pretty much anti-spill, but just a bit tight getting your fingers in. but are well worth the price.

So my conclusions are that for anyone requiring a heavy pellet in a .177 PCP gun running above 12 flb these would fill the bill although I’m not sure what you would use them for, as I don’t consider them a hunting pellet especially for game you would shoot using .177 cal, whereas in a .22 running 16flb then it may come into it’s own.

This is the diffrence between a Bisley hollow point hunting pellet and the harder Prospero, both were shot into modeling clay, the Bisley would stop a rat dead in it's tracks but the prospero would pass stright through.

Al

Slavia · Moderator

Addendum:

Just for the heck of it, I shot the Prospero pellets through my Chinese B3. That gun likes RWS Superdomes, and the Prospero pellets were equally accurate. The big surprise was that it was much, much smoother.

Well, maybe it shouldn't be a surprise - the B3's transfer port is visibly larger than my other .177 guns, so I should have guessed that it might favor heavier pellets. Still, it's ironic that my McDonald's gun would have cordon bleu tastes.

rsterne · Moderator

Prospero USA also sent me some of their 12.8 gr. Field Line pellets to test.... Slavia and Alstone have already written excellent reports on the pellets, so I'll just add some accuracy and velocity testing I did with my Diana 34 today....

The Prospero pellets are to be used in rifles over 12 FPE, and my Diana just qualifies, as you will see below.... As these pellets are on the heavy side for this rifle, I decided to test them only against similar pellets.... and that meant only those over 10 grains.... Here are the results of the velocity tests and preliminary accuracy screening....

The coloured columns on the left indicate how the pellets performed on my indoor range of 20 feet.... You may think it impossible to differentiate between pellets at such a short range, but I use washers to place over the groups to grade them GREEN (covered by a 3/8" washer), RED (not covered by a 1/2" washer), and not marked (in between).... I have never found a pellet that graded red that was worth even testing outdoors.... Likewise, my pellet of preference nearly always comes from the green group.... Of course every gun is different, so my results may not be typical of those using another gun.... possibly not even another D-34....

You can see by the energy developed that as the weight increases above 10 grains in this gun the energy drops off.... FPE numbers in blue are over 13 FPE, those in black 12-13 FPE, and those in red under 12 FPE.... The Prospero pellets just made the cut at 12.16 FPE.... Note that the Standard Deviation in velocity for the Prosperos was higher than average at 11.0, but not the worst of the group.... Most of the groups I shot with this pellet were between 3/8" and 1/2" OD at 20 feet.... I have to make a comment here about the H&N Rabbit Magnums.... First of all, they were so tight you couldn't push them into the breech with your finger, I had to seat them with a rounded plastic probe.... Just to give you an idea of how bad they performed, check out this target....

I fired 10 shots, only 8 of which are shown.... The other two were off the paper to the right.... making a group of over 1.5" at just 20 feet.... BAD!!!.... The other target above shows how this gun shoots with it's favourite pellet, the 7.8 gr. JSB Express.... about 0.08" C-T-C at the same distance.... Now on to the group testing with some of the pellets I shot today.... I shot two 5-shot groups with each pellet, one above the other....

Left to right: H&N Baracuda 10.2 gr.; H&N Baracuda Hunter HP 10.2 gr.; JSB Exact Heavy 10.3 gr.; Benjamin Discovery HP 10.5 gr....

Left to right: Crosman Premier Heavy 10.6 gr.; Propsero Field Line 12.8 gr. (two sets); JSB Exact Monster 13.4 gr....

The scope was not adjusted during the two-group testing.... The vertical POI change, while in the correct direction relative to the velocity, is way too great to be due to the velocity difference alone.... so we are left to assume that barrel harmonics, or the way the springer responds to the difference in the shot cycle is the culprit.... The rifle was supported on a sandbag at the center of gravity, and loosely held against my shoulder with my left hand under the butt of the stock.... I have found in the past that this technique works extremely well for shooting this rifle off the bench, and you can see for yourself how consistent it is....

The tightest groups were the JSB Exact Heavy 10.3 gr. closely followed by the H&N Baracuda 10.2 gr.... The H&N Baracuda Hunter Hollow Point 10.2 gr. was nearly as good.... The Prospero pellets, while turning in a couple of good groups, shot them to slightly different POIs, and the other two groups reflected this slight vertical stringing.... The Crosman Premier Heavy 10.6 gr. and the nearly identical Benjamin Discovery Hollow Point 10.5 gr. were clearly not as good, the groups becoming "cloverleafs" instead of ragged holes.... The JSB Exact Monster 13.4 gr. pellets exhibited severe vertical stringing, and although my preliminary assessment had them in the "middle" accuracy group, I have reclassified them to the "red" zone as unsuitable in this gun....

In summary, the Prospero Field Line 12.8 gr. pellets are well made, and fit fine into the breech in my Diana 34.... I thought I noticed a very slight difference in how they loaded, and this may be reflected by the slightly higher than normal SD and the slight vertical stringing.... They certainly shoot well enough to warrant further testing at longer ranges.... I plan on doing some shooting outdoors, weather permitting, and measure the downrange velocity to calculate the Ballistics Coefficient.... In addition, I also plan to test them in my "Uber-Pumper", a 2200/2289 crossbreed that I can shoot at over 15 FPE to test them in a slightly more powerful gun....

Bob

SMP · Silver Status Member

I have also been asked to test the new PROSPERO Field Line pellets 12.8 gr 177 cal. I was able to take advantage of reading the excellent reviews from Slavia and AlStone before I even started my testing because my trigger finger wasn’t up to snuff.

That worked out to my advantage because now that they have covered all the technical details I can basically just go play…perfect .

Because I live in Canada I have chosen to use a Canadianized Crosman Quest with a 4x32 Centerpoint. My reasoning’s are very simple in that the Quest B18/19 variant probably represents over 50% of the air rifles in use in Canada and it is still in “out of the box” stock condition. The only work that has been done to this rifle would be considered “free” tuning. It’s my wife’s rifle so the shorter Canadian spring allows her to cock it easily.

My first impressions of the pellets were that the packaging is very well designed and indeed I feel it is worthy of being a product in its own right. The pellets are simply perfect. The dies that formed these are obviously brand new and the process is very refined. Each and every pellet is well finished and uniform with a light sheen of lubricant. No flaws, die marks or blemishes could be seen on any pellet.
More about the case…This thing is an absolutely brilliant gadget. It clips onto your belt or waistband with a very well made spring steel clip. I found the clip was secure after wearing it clipped to my waistband for the entire day. The container stays securely closed until the release point is pushed. The container can be opened and closed repeatedly without jamming or binding on the contents. When open I can easily get my fingers inside and pick out a pellet. At the bench the whole unit will flop completely open and sits flat.

Testing
The manufacturer claims that the pellets unique shape and weight improve performance in wind

Hypothesis
The pellets unique shape and weight improve accuracy in windy conditions.

Methodology
a) Conduct ten meter group tests with a large variety of pellets to determine if the Quest is a suitable platform. This will be done indoors under controlled conditions
b) Conduct group size tests at longer distances in moderate to strong crosswinds using a broad range of readily available pellets

Data
a) For this test 5 shot groups were fired and the center to center group size was measured using dial face vernier calliper.

Group data
Crosman Premier Field Target 0.233”
Crosman Premier Super Match 0.251”
RWS Superpoint 0.264”
Prospero 0.305”
RWS Superdome 0.343”
RWS Hobby 0.427”
Crosman Premier UltraMag 0.513”

I decided that the Crosman Premier Ultra mag would be dropped from the data set and would not be used for further testing. The Prospero pellets meet the SUM/AVG of the remaining data set so therefore I conclude that the Crosman Quest is a suitable platform to continue to the next test.

b) For this test I waited until I was at work. Work sits on a mile long peninsula that sticks out into Lake Ontario. The winds are very consistent and I have access to accurate weather monitoring equipment

Conditions
Time 7pm
Temperature 2deg C
Wind 12Kn/14mph/22kph at 90deg to line of fire from left to right
Distance 40m/44yds

Group Data
RWS Super Point 0.875”
RWS SuperDome 0.910
Crosman Premier Field Target 0.975
Crosman Premier SuperMatch 0.982
RWS Hobby 1.240
Prospero 2.840

Note: the group sizes are the average from 3 separate strings

Conclusion

Based on the collected data the manufacturer’s claims that the unique shape and weight improves the performance in windy conditions are not supported. The group data would suggest that the stability of the pellet breaks down rapidly. It is possible that barrels with a greater twist rate would stabilize the round better.
The two domed pellets performed the best in windy conditions in fact the CP Field Target showed almost no left to right deviation from wind effects.
The wadcutters as could be expected showed the most left to right deviation however the group size remained consistent showing the stability was not affected.

rsterne · Moderator

Good report, Sean.... My only comment is that a Canadianized Phantom (ie under 500 fps) would only deliver about 4 FPE.... while the Prospero pellets are intended for rifles over 12 FPE....

Still, it's an interesting test which shows how important a good ballistics coefficient is.... Mr. Green

Bob

SMP · Silver Status Member

Actually Bob that little "only free mods" meant I plugged the vent hole shhhhh Evil Plot

depending on the pellet it.s 11.9 to 12.1 fpe This represents the MOST you would ever get out of Canadian B18/19 without parts. and to be honest most would be lucky to see 10.5fpe

rsterne · Moderator

Ahhhhhhhhh... got you.... did you measure the velocity and energy with the Prosperos?.... Should be fairly close to my D-34....

Bob

AirGunEric · Site Admin

A regular Phantom/Quest 1000/G1 etc. achieves about 15fpe, the 'detuned' versions obviously vary by country- i.e. Canada, the UK, and so on.

That being said, I'm not so sure that "testing for a market" is entirely useful overall- if the pellets claim the rifle should be at least 12fpe, by ignoring this the test validity can be more easily questioned. Likewise, someone could have a "market specific" .25 caliber rifle shooting 10fpe, but trying to test 43.5gr pellets in it would be pointless except perhaps over extremely short distances.

Alstone · Moderator & Site Supporter

You have got a point there Eric, I have tried some of these pellets in a QB78 putting out 10 fpe @ 600 fps, and find them ideal for putting a lot of kinetic energy at the point of impact to a maximum range of 25m, whereas at higher fps the pellet would pass through a rat, at these lower fps the pellet seemed to do a lot more damage and did knock them over.

But I still think they have a bit of a niche market in .177 cal (But what it is I am not sure). A lower weight around 8.5 gr would be interesting in .177 or maybe a higher one in .22 cal?

Al

SMP · Silver Status Member

Eric, you have an excellent point. I will re run the exact same test using a B18/19 that has been tested at 16.5fpe

rsterne · Moderator

SMP · Silver Status Member

Your absolutely correct Bob. The true FPE is dependent on ...well absolutely everything, caliber, pellet weight even temperature and whether the gun can recoil.

So I wont know the true conditional fpe until the actual test. But I'm confident that 16 fpe is a good guess.

This is the F1 version B18/19. After receiving a high power gas ram , custom piston and custom transfer port .... well it's not really an "anything" anymore.

In fact it's not even mine, I'll have to borrow it back from the guy I transferred it to Embarassed

rsterne · Moderator

Boy am I BEAT!.... I just finished a pellet testing session with my Uber-Pumper at 20 pumps per shot.... Yes, folks, that's 100 pumps per target.... OH! and then for good measure I did an extra test with the Prosperos at 30 pumps.... Rolling Eyes

Here is the gun I used.... it's a crossbreed between a 2200 and a 2289.... The pump has 50% more swept volume, so 20 pumps on this gun is like 30 on a 2289.... and after 10 pumps the effort goes up and up.... At 30 pumps it's a BEAR!!!....

The good thing about this gun is that it's a tack driver, and it's not particularly pellet fussy.... I'd never shot it with pellets over 10 grains, so I selected a bunch of pellets, including the new Prospero Field Line, and started shooting.... Here is a table with the detailed results....

You will note one significant difference between this high powered pumper and a medium powered springer.... Basically, the heavier the pellet, the higher the FPE.... With pellets under 8 grains, the gun is around 14 FPE.... With pellets in the 10 grain range, the gun is in the high 15 FPE range.... With the heavier pellets, it's over 16 FPE.... At 30 pumps with the Prospero pellets, it was over 18 FPE, which is 50% more energy than with my Diana 34.... Because of the inherent accuracy of this gun compared to a springer, I used slightly smaller washers to grade the red/green accuracy part of the chart.... Green indicates you could cover the group with a 5/16" washer.... Red indicates you couldn't cover it with a 7/16" washer.... No colour was in between.... The Prospero pellets fell, once again, into the middle group at both velocities.... Their SD was narrower than yesterday, at the high end of the group still, but better.... I notice that as the velocity increases, the SD seems to be coming down.... Here are the targets, once again shot indoors at 20 feet....

I was not surprised when the 7.8 gr. JSB Exact Express shot the tightest group, virtually just a ragged hole well under 1/4" across.... it's always been this guns favourite.... I was very pleased to see lots of other pellets shoot extremely well, however, including (in order) the H&N FTT, H&N Baracuda, JSB Heavy, H&N Baracuda Hunter HP, JSB Monster, and the JSB Exact, all of which produced 5-shot groups you could cover with a 5/16" washer.... The new H&N Econ pellet and the boxed Crosman Premier Lights ended up in the "red" zone although both groups were still under 1/2" OD.... The remaining pellets, the RWS Hobby, Benjamin Discovery HP, boxed Crosman Premier Heavies, the Prospero Field Line, and the H&N Rabbit Magnums all fell in between.... although the Prospero pellets fired at 800 fps ( 18 FPE) were VERY close to being covered by the smaller (5/16") washer.... Both groups with the Prospero pellets would have been inside the 3/8" washer I used in yesterdays tests with the Diana 34.... Incidently, this is the first gun I have ever had that would group the H&N Rabbit Magnums rather than spraying them all over, so they may have an application in some higher powered guns....

In conclusion, the Prospero Field Line 12.8 gr. pellets definitely shoot well enough in this gun to warrant further testing outdoors at longer ranges.... Their heavier weight is an advantage in a higher powered Pneumatic airgun (pumper or PCP).... and they seem to keep getting better as the velocity increases.... Unfortunately, I don't have anything powerful enough to drive them into the 900s, but that might be interesting for those who have a suitable gun (something in the 25 FPE class in .177)....

Bob