Prospero 12.8 gr. Field Line Pellets vs. Others

[rsterne]

Prospero USA sent me some of their 12.8 gr. Field Line pellets to test.... so I did some accuracy and velocity testing 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

[oldpink]

Excellent detailed review.
Really nice to get some hard data instead of just some random thoughts.

[rsterne]

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....   

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

[Addictedtoair]

Thanks for the review and information Bob.

Brett

[Smackey54]

Excellent display and write-up! Thanks for putting the effort into that. Very helpful! That is very helpful to me.

[rsterne]

Just a short report today.... I tested some pellets for velocity and accuracy today while working on my QB 78 HPA conversion.... Here are the results....



I didn't record the SD, but I did shoot some 5-shots groups inside at 20'....



You can see that the JSB Exact Heavies and the Crosman Premier Heavies both produced one-hole groups, followed closely by the H&N Baracudas.... The Prosperos shot about 0.2-0.25" C-T-C, which at this range is OK but not stellar.... The JSB Monsters seemed to hang up on loading in this gun, and I'm not sure if the group (similar to the Prosperos) was spoiled by a damaged pellet or not.... The H&N Rabbit Magnums were, once again, the worst of the bunch....

I seem to be getting similar results in all three guns, regardless of whether the Prosperos are shot at 12 FPE. 17 FPE, or 22 FPE.... Their accuracy is OK but not on par with the best in each case.... Further testing outdoors may have to wait until the spring....

Bob