Altaros slugs... Next Generation performance!

[Centercut]

I've been shooting the .25 caliber Altaros ATP Smooth 49.5 grain slugs the past 4 or 5 months, at about 885 fps from my 600mm Panthera. The BC on these slugs is an astounding G1 BC of 0.21. Thats not a typo! They shoot very accurately at distances out to 286 yards (the farthest I've shot them). I shot them at the Long-Range Challenge in Oregon the end of April and went 25/25 (second place was 18/25).
Out of all the heavier .25 caliber slugs I've shot, including the ZAN 41 grain and NSA 43.5 grain, these are a revolutionary step up in performance. On a good day from prone, I could hit 8 of 10 at a 4-inch swinger at 200 yards in the wind with the two above conventional slugs. With the Altaros, I hit 10/10 or even 20/20 and the groups at 200 yards were covering not much more than half the 4-inch swinger...
They are also made in .22 caliber, in 32.3 grain weight with a BC of G1 0.18. One word of caution, DO NOT try to shoot them fast, or you won't like them. They are designed to be shot at speeds from 880 to 900 fps. Caviat Emptor!

 

[hameditor]

Mike, thanks for sharing your experience with Altaros slugs. HAM looked at some in .22 and they were definitely very beautiful. In fact, they looked almost too good to shoot!

However, there's a problem with the 0.21 BC claim. This is based on the G1 ballistic model which is inappropriate for slugs. The BC value increases with increasing velocity in the G1 model. So, the faster you shoot, the higher the BC value - at least when using the G1 model! There's more discussion of this phenomenon in this series of HAM articles.

In theory a BC value should be constant, irrespective of velocity. Altaros shoots the slugs VERY fast to achieve their claimed G1 BCs, which are not attainable at lesser velocities. There's a (much) more detailed explanation in Bob Sterne's HAM article here.

Note that Altaros does quote G7 BCs for some of its slugs. Why not all? I don't know.

If you look at the ATP Queen .25 cal slugs, Altaros quotes a G1 BC of 0.245. But they also quote a G7 BC 0.128. The latter is likely much closer to reality - as the company actually says on their website under the "Parameters of Slugs" page.

When HAM tested Altaros slugs in .22 caliber, we found BCs of 0.121 and 0.119 for the two models using the G7 model. This compares to the company's claim of around 0.15 (depending on slug) with the G1 BC model.

Of course, BC values have nothing to do with inherent accuracy. And Altaros G7 BC values - where they quote them - are extremely impressive, too. However the G1 BC claims are not realistic in my opinion.

 

[Centercut]

Actually, when I plugged in the values shortly after getting the .25 cal 49.5 grain slugs, I initially used the 0.21 G1 BC at 885 fps. The DOPE from Strelok Pro was spot on from 50 to 286 yards, which was as far as I tested them at the time.

Coincidentally, the Altaros guy (Ondrej) recommended a G7 BC of 0.111.
These two BCs give IDENTICAL drop from 50 out to 300 yards. The G7 uses a different drag coefficient than the G1 but the 0.21 G1 and 0.111 G7 give the exactly the same DOPE within 1/4” drop at 300 yards. And going out further, the G7 gives slightly more drop than the G1 and is more accurate past 300 yards for this slug. These Altaros ATP Smooth slugs are extremely consistent size and weight. They are BEST shot between 880 and 900 fps. Not sure what speed HAM tested them at? I think the reason both these drag models fit the ATP slugs is that we shoot them at 880 to 900 fps. In fact, my Panthera is tuned to 885 fps. These speeds are well below the transonic zone, and also well below the velocity region where BC is affected IMHO.

So I’m going to have to disagree with you Stephen, and I verified this BC both prior to and during the Long Range Competition in Oregon. AND THE DOPE WAS SPOT ON! Enough spot on to go 25/25 when the next best score was 18/25. FYI, my 5 shot group on the middle red swinger at 240 yards was only slightly larger than an inch!

 

[hameditor]

We shot the .22 Altaros slugs at 749 FPS for one, 765 FPS for the other.

 

[Centercut]

We shot the .22 Altaros slugs at 749 FPS for one, 765 FPS for the other.

Yes, way too slow. Like I said above, they perform best just below 900 fps. I use 885 fps because that gives me 20+ shots on reg from the .25 Panthera 600mm and that’s good enough for NRL-22 (86 fpe). Any higher than that, even if they shot well at 925 or even 950 would reduce the shot count to an unacceptable level, plus make the gun “jumpier” and harder to shoot accurately.

 

[rsterne]

These two BCs give IDENTICAL drop from 50 out to 300 yards.

That is only true at some velocities, which is why the drag model chosen should be a good match to the projectile you are shooting.... When I mentioned the poor match between the Altaros slugs (and others) to Ondrej, he told me that he uses the G7 profile when shooting at long range, as it was a much better match to his boattailed slugs....

As an example, the 106 gr. 7mm Bob's Boattail slug I designed has a BC (G1) when shot at 1000 fps of 0.26, but the BC (RA4) is only about 0.22.... However, as the slug slows down the RA4 profile, which is a better match, maintains a relatively constant BC, whereas if you check the BC (G1) at 800 fps, it is down to about 0.19, and continuing to drop.... Obviously, if you used BC(G1) of 0.26, and shot at long range, the slugs would drop more than a BC (G1) of 0.26 would suggest....

The Altaros slugs are great, it is good to see a manufacturer exploiting boattails to reduce drag, and a narrower mid-body to reduce bore friction.... things I have been using in my cast slug designs for a decade.... I hope that Ondrej's use of drag profiles other than G1 for airgun slugs catches on, as the manufacturers are NOT doing their customer service by claiming a BC unobtainable when the profile they choose is a poor match for their product....

Stephen's point is valid.... The BC you obtain will change with velocity if you use the G1 profile, because it does NOT match airguns slugs properly.... BC should NOT change with velocity if the match is good....

Bob

 

[AtlasAirguns]

Interesting read. I'll be following

 

[Centercut]

That is only true at some velocities, which is why the drag model chosen should be a good match to the projectile you are shooting.... When I mentioned the poor match between the Altaros slugs (and others) to Ondrej, he told me that he uses the G7 profile when shooting at long range, as it was a much better match to his boattailed slugs....

As an example, the 106 gr. 7mm Bob's Boattail slug I designed has a BC (G1) when shot at 1000 fps of 0.26, but the BC (RA4) is only about 0.22.... However, as the slug slows down the RA4 profile, which is a better match, maintains a relatively constant BC, whereas if you check the BC (G1) at 800 fps, it is down to about 0.19, and continuing to drop.... Obviously, if you used BC(G1) of 0.26, and shot at long range, the slugs would drop more than a BC (G1) of 0.26 would suggest....

The Altaros slugs are great, it is good to see a manufacturer exploiting boattails to reduce drag, and a narrower mid-body to reduce bore friction.... things I have been using in my cast slug designs for a decade.... I hope that Ondrej's use of drag profiles other than G1 for airgun slugs catches on, as the manufacturers are NOT doing their customer service by claiming a BC unobtainable when the profile they choose is a poor match for their product....

Stephen's point is valid.... The BC you obtain will change with velocity if you use the G1 profile, because it does NOT match airguns slugs properly.... BC should NOT change with velocity if the match is good....

Bob

Thanks Bob, I’ve been a student of your teachings for years. And yes, I’ve actually been using the G7 profile for the .25 cal 49.5 slugs of 0.111 since Andrej recommended it.
On a similar subject, can you tell me what this new G5 profile that is available in ChairGun Elite+ is all about? Would it be a good match for any of our Airgun slugs?
Thanks,
Mike

 

[rsterne]

The G5 is a spitzer boattail, not a lot different to the G7, and is not new....



The nose of our airgun slugs is significantly blunter than either the G5 or G7, or for that matter the G1.... The RA4, which is for the .22LR bullet is the closest of the "common" drag profiles.... Miles Morris, UK Ballistician (ret'd) has developed an improved pellet drag profile, the GA2, and two new profiles for slugs.... The SLG0 is for typical airgun slugs with a straight mid/after body, a tangent ogive nose, and a Meplat (usually with HP).... The SLG1 is for boattail slugs.... They are available in the "Easy BC" and "MERO" ballistics calculators from George Conway at:

GPC Ballistics Applications for Windows, MacOS and Linux

A few ballistics applications for Windows, macOS and Linux written in the PureBasic programming language.

gpc.fotosoft.co.uk

They are available for most operating systems / platforms.... and download (and use) is free....

Bob

 

[Pumacarl]

Yes, yes, and a big YES! More posts like this please! I follow what all of you guys write, and I really appreciate it! It's discussions like this that I really look for when coming to these sites. Thanks!

 

[Pumacarl]

I have a question about drag models for Zan BR30 56gr pellets. Tom Costan was recently shooting these pellets at 943fps with a b.c. of .078. When I shoot them at 846fps, I use a b.c. .06 and it works well. The b.c. to me, seems to be changing with speed, something you guys are saying shouldn't happen. Is it because we need to pick a speed to change drag profiles for this pellet, or should we use something other than the GA in the first place? Something else I noticed plugging the numbers into Strelok, the FX Hybrids slugs (b.c. .07) at 905fps using the G1 profile, match the trajectory just about perfectly of the Zan BR30 at 943fps using .078 as a b.c. on the GA profile out to 190y. I didn't check further because I typically won't shoot further. This kind of throws my whole idea of it's safer to shoot a skirted pellet than a slug, right out the window. It seems everything changes at some speed and weight. With pellets getting heavier is there going to be a need for a different drag profile that doesn't change its b.c. with speed? Is there one already? Thanks for the discussion topic, very interesting stuff!

 

[Centercut]

I know at least 4 shooters that use the ZAN 56 pellets, and all of them shoot them 860 to 880 fps. BC GA profile between 0.055 and 0.060. I’d have a hard time believing 0.078 especially that fast where BC tends to lessen with speed.

 

[CTAirgunner]

I love reading this kind of stuff even though I don't understand all of it yet because I can't learn with just paper I learn by doing. So when I was tuning my .25 huben for 33.95 , it would not shoot them accurately at all around 850-920 , once I cranked it up to 955 I could pull MOA groups at 100 with them. Isn't each situation / rifle different? Every barrel and pellet combination different? Sorry for my crude post in a thread full of expertise.

 

[Pumacarl]

I know at least 4 shooters that use the ZAN 56 pellets, and all of them shoot them 860 to 880 fps. BC GA profile between 0.055 and 0.060. I’d have a hard time believing 0.078 especially that fast where BC tends to lessen with speed.

Me, and a lot of Evol .30 shooters around here, will certainly let you know once we get our hands on the bigger plenums.

 

[Pumacarl]

I love reading this kind of stuff even though I don't understand all of it yet because I can't learn with just paper I learn by doing. So when I was tuning my .25 huben for 33.95 , it would not shoot them accurately at all around 850-920 , once I cranked it up to 955 I could pull MOA groups at 100 with them. Isn't each situation / rifle different? Every barrel and pellet combination different? Sorry for my crude post in a thread full of expertise.

Throughout history in just about all endeavors, "doing" has often produced results nobody was expecting or knew to figure for. It can be as good/bad as any method it just takes someone willing to do it. Keep at it Kevin!

 

[Centercut]

Me, and a lot of Evol .30 shooters around here, will certainly let you know once we get our hands on the bigger plenums.

Don’t forget many competitions like EFT limit power to 100 fpe. That would be 896 fps maximum with 56 ZAN pellets.

 

[oOmpH]

Don’t forget many competitions like EFT limit power to 100 fpe. That would be 896 fps maximum with 56 ZAN pellets.

Don't think there's much to gain going faster anyways?

 

[CTAirgunner]

Don't think there's much to gain going faster anyways?

Other than accuracy if that is what changes...

 

[Centercut]

Don't think there's much to gain going faster anyways?

I’d shoot them between 855 and 875. Going to try in my Delta Wolf in a week or two.

 

[MountainSportAirguns]

Actually, when I plugged in the values shortly after getting the .25 cal 49.5 grain slugs, I initially used the 0.21 G1 BC at 885 fps. The DOPE from Strelok Pro was spot on from 50 to 286 yards, which was as far as I tested them at the time.

Coincidentally, the Altaros guy (Ondrej) recommended a G7 BC of 0.111.
These two BCs give IDENTICAL drop from 50 out to 300 yards. The G7 uses a different drag coefficient than the G1 but the 0.21 G1 and 0.111 G7 give the exactly the same DOPE within 1/4” drop at 300 yards. And going out further, the G7 gives slightly more drop than the G1 and is more accurate past 300 yards for this slug. These Altaros ATP Smooth slugs are extremely consistent size and weight. They are BEST shot between 880 and 900 fps. Not sure what speed HAM tested them at? I think the reason both these drag models fit the ATP slugs is that we shoot them at 880 to 900 fps. In fact, my Panthera is tuned to 885 fps. These speeds are well below the transonic zone, and also well below the velocity region where BC is affected IMHO.

So I’m going to have to disagree with you Stephen, and I verified this BC both prior to and during the Long Range Competition in Oregon. AND THE DOPE WAS SPOT ON! Enough spot on to go 25/25 when the next best score was 18/25. FYI, my 5 shot group on the middle red swinger at 240 yards was only slightly larger than an inch!

No 1000 yard testing eh?