NSA .20/18.9grain slug results

[Franklink]

Learned something interesting about these .20/18.9grain slugs in the last few days....

I mapped out actual trajectory from 20-100 in 5 yard increments with them going 865-870 and then compared what I had to Strelok. It needed a BC of 0.07 to line up.

I then mapped out actual trajectory from 30-100 (but only in 10 yard increments here) with them going 910-915. Comparing that trajectory arc to Strelok required a BC of 0.09 for actual to match predicted.

I've mostly shot them closer to 870-880 prior to this, always using a BC of 0.09. It appears that right around 865-870 there's exists a node of sorts where the BC isn't as high as when they're going faster.

A friend also shooting them is seeing a BC of 0.1, although it seems he's mostly shot them a bit higher yet, 920-930, if I follow him accurately.

Now, I understand that a the ballisticians amongst us will say that a BC shouldn't change with speed. But sorry, in the real world it does. And yes, that means the reference drag law isn't ideal for the projectile, but we work with with we've got.

The difference in speed (and therefore BC in this case) is that at 100 yards they need 2.6 mils of elevation with the 865-870. And they need 1.8mils of elevation at 910-915. Same scope zero of about 65 yards for both.

 

[Ballisticboy]

If the BC values you are using are based on G1, as the speeds increase above 880 ft/sec, then the BC will tend to increase. It would be interesting to hear if the same happens with SLG0 as it was an attempt to produce a reference curve which did not change so much at the higher speeds.

 

[Franklink]

If the BC values you are using are based on G1, as the speeds increase above 880 ft/sec, then the BC will tend to increase. It would be interesting to hear if the same happens with SLG0 as it was an attempt to produce a reference curve which did not change so much at the higher speeds.

Thanks Miles.

Because I'm working backwards from actual trajectory, and then playing around with the BC in Strelok til it matches, it would be whatever Strelok's default drag law is. (I'm not seeing a way to change it in the version I have).

If I had some downrange fps collected for each of the two starting speeds, I'd plug those values into EasyBC where I could change from G1 to SLGO0.

On page one of this discussion (months ago) I shared some screen grabs from EasyBC, using a starting fps of 882. For G1 BC was 0.092 and for SLG0 it was 0.095. That was uncorrected for elevation though.

Funny thing about the altitude correction, if I use the altitude-corected BCs the software spits out, the trajectory arc doesn't match actual. That was with them in that 875-880ramge I've mostly shot them at. Time will tell if it holds true for my new speeds of 910-915. So far 0.09 is what I need, even with new speeds, for true arc to match predicted, at least out to the 100yards that I've so far tested the new speed.

 

[Franklink]

Just took them to a new longest yet range, lasered 296 yards. Strelok tells me 192 clicks, @ 1/10th mil each so 19.2 mils. And I'm using 10 mils of turret clicks and another 9.5ish of holdover so a whole lot of ish here.

Strelok also says they should have about 15fpe still left at this distance.

And the dang things are staying in a roughly basketball sized desired impact point, repeatedly! Yeah that's not any sort of amazing precision, but for such a tiny pill and such a long range, I'd sure have a hard time believing even this was possible if I wasn't seeing it happen.

 

[Arzrover]

They shine pretty bright for me at 208 yards. I've been able to hit about anything I've put out there and consistent day to day as well.. Definitely my favorite slug...
I need to run some paper out that far sometime
Bob

 

[ChuckHunter]

Pretty interesting!
Did you guys know that Zan is now producing .20 too! 15/20/25 grain!
I have a couple .20 PCPs and the only slugs I've tried were the 14 NSA and didn't have great results! Thinking on ordering some 15/20 grain Zan and giving it another go.
My best candidate is a Daystate huntsman regal that at the moment is shooting the 15.89 JSBs at 890 fps but I can still increase the power a bit more!

 

[Franklink]

Pretty interesting!
Did you guys know that Zan is now producing .20 too! 15/20/25 grain!
I have a couple .20 PCPs and the only slugs I've tried were the 14 NSA and didn't have great results! Thinking on ordering some 15/20 grain Zan and giving it another go.
My best candidate is a Daystate huntsman regal that at the moment is shooting the 15.89 JSBs at 890 fps but I can still increase the power a bit more!

Please let us know how the Zans shoot. I suspect the 25grain will be a little long for typical airgun barrel twist rates, but I'm still curious to see some real-world results.

 

[Ballisticboy]

Please let us know how the Zans shoot. I suspect the 25grain will be a little long for typical airgun barrel twist rates, but I'm still curious to see some real-world results.

You may get away with normal twist rates, the slugs have a large hollow in the base which will shift the CG forward, helping you to get maybe sufficient stability. It is not just the length of the slug, it is also the inertias and the positions of the CG and centre of pressure.

 

[Franklink]

It's been awhile since I shared anything about these .20/18.9 NSA slugs but I've still been shooting them as my primary long range airgun projectile.

I had a run with a .20 Condor and after some barrel polishing it shot them quite acceptably. That makes three .20 Lothar barrels that I have personally shot the 18.9 grain NSA slug out of and have been pleased with the results from all three. And all three of those barrels are choked.

I'm weird about keeping all my empties and just counted and I'm in my 19th box of these slugs. At 300 per, I'm over 5500 total. I'd guess about 75% hunting/pesting and the rest just having fun hitting stuff a long ways off.

At my elevation and from the 3 barrels I've personally experienced...
At 850fps, they're good for a BC of 0.08.
At 875-880fpe, BC will be more like 0.09.
Above 910-915, and the BC is 0.099 (0.1).

They are dependably accurate from 850 to 930. And might be below and above that as well, just no personal experience to vouch for them at speeds outside those that I just listed.

This was from this evening....5 shot average at the muzzle and 10 shot average at 47 yards. The 10 shots at 49 yards had an ES of 18fps. That's mighty tight for a downrange fps over 10 shots. Seems the most accurate pellets or slugs always have the most consistent downrange ES.

And this is what I've been using for the past few weeks in the ballistics profile of the PARD digital scope that's on the gun I'm primarily using with the 18.9grain slugs.

And that ballistics info has been good for outings like this....
Skip this one completely if you're a critter lover. While some might consider them cute, these dudes are serious pests for the farmers. I've yet to be turned down when asking permission to shoot them on various properties. All up and down the little farming community where I live I've got people that have given me permission. Many of them I initiated, but some of them actually reached out to me, friend of a friend, etc.

Anyway, the wind was pretty stout this day. Check out the wind on the grass on one of those first couple clips in video. In the past, windy days like this would not have been a day I attempted getting after the pdogs, but these slugs make it not only possible, but quite successful. The hold off for the wind was pretty evident on some of these, even with a 0.09-0.1BC slug. Interestingly enough, BC and hold off don't seem to have a linear relationship. The BC of the 18.9gr NSA slugs is about double the BC of a good .20 or .22 long range pellet, but the hold off for the pellet in similar wind at these 100+ yard ranges is more like 3-4 times that of the hold off required for the slug.

Most shots felt like they were in the 70-125 yard range. What I included in the video are the cleanest kills from about 2hrs of shooting. I left in some misses. I also left in some hail mary's in the 215-220 yard range. Although even those hail mary's were just this close from connecting. The farthest obvious hit was at 169 yards, towards the end of the video, it was almost a double. There's also a solid 165 yard shot (death dance).

Even on the far shots these slugs zip right through the prairie dogs. With a good clean vitals shot they often run 20 or so feet and then flop over dead. I left a couple of those in the video too.

It's also interesting to watch the dust splash after one of these slugs goes through a dog. They often change directions quite drastically, deflection off spine/skull is what I figure.

Pretty dang cool to get this kind of long range accuracy from a tiny little pill at only 35fpe. Shot count's are the other end of the extreme when compared to the big bore/big fpe that many airgunners are using for these types of ranges. You get 8 shots per fill you say? Nice, I get 80 (EIGHTY). The .20/18.9grain NSA slugs are currently my projectile of choice for long range precision pesting fun. And it was a long road with a lot of wasted money testing other small bore slugs to get here. I don't foresee anything else nocking it out of my long range numero uno any time soon.