Sub MOA How Far

I went to the range today to try 100m, 200m, 300m, 385m.

I had loaded Strelok Pro since my last outing and plan on replacing ChairGun as my main ballistics app.

I played around at 100m and 200m to verify my dope. I made some adjustments. And then dialed for 300m. I took three shots to verify and all three hit metal. I walked down range and painted a pig at 300m and a turkey at 385m for fresh targets to try 5 shot groups. I had only ten slugs left from what I brought that day.

5 shots at single 300m (328yds) group for the day. About 3.4" c-to-c spread which equals about 1moa at 300m:





I dialed for the turkey at 385m (421yds) but only connected one of five, so no group. It seems to open at some distance between 328yds and 421yds. Conditions were good so I can't blame that. I have some powder coating for the slugs that I want to try before going that long again.



Edit: the turkey required a combination of clicking (+75moa) and holdover (+10.5moa).

That’s awesome! I also love the targets.

Is this your 257 rifle?

mike

That’s awesome! I also love the targets.

Is this your 257 rifle?

mike

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Yes. .257 TJ 1:14 twist barrel. Arsenal 71.5gr 257420 BT slugs at 995fps.

It's a high power NRA silhouette range, so that's the targets that are out there, chickens at 200m, pigs at 300m, turkeys at 385m and rams at 500m. I can knock the chickens over at 100m if I hit them high. The 300m pigs and farther just makes a mark. I might have rotated the turkey a little with the only hit on it that was a little low and left.

Very good Scott!

I'm just going to blabber on a bit....

Its always interesting to me how at some point at farther distances each projectile at whatever velocity and BC begins to falter in precision.

Sorry to be OT here but I'm just giving personal examples below with centerfires.

Even with expensive 22rf ammo tested for precision at the Lapua facility, using that in my 22rf capable of 1 moa fairly often at 100Y, provided the wind is cooperating, that at 421Y its very hard to hit our steel turkey, but at 328Y on a steel pig it wouldn't be very difficult. I don't have a pig sized steel but instead use a steel that is 1 foot wide by 15" tall not including the head. My vertical is more like 2.5 moa though at 300Y because the ES is 30-ish fps.

Then if I use my 5mmFBI which is a little centerfire varmint cartridge, 32's/.210BC at 3750 fps, its pretty easy to hit that steel turkey at 421Y, at 500Y its still working well too, but by 675Y its faltering and getting tough to hit our 10" steel.

The 10" steel at 675Y isn't hard to hit with my 6mmBR with 95gr/.495BC at 2950 fps but yesterday at 1150Y a 14" steel wasn't easy to hit. Granted it was windy though so at some point I'll try again in calmer conditions. My friend used his 7mmSAUM yesterday too at 1150Y which uses 180gr .68 BC bullets going 2850 fps and the steel was easier to hit.

And so on as the projectile BC goes up with ample velocity which I've experienced with a big 30 caliber, and taking it further using a 375CT.....

Impressive shooting Scott. Hopefully I get to shoot that gun at RMAC in June this year...

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Even with expensive 22rf ammo tested for precision .... My vertical is more like 2.5 moa though at 300Y because the ES is 30-ish fps.
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I don't know about an ES of 30-ish fps, because that does not tell me anything about probability. But for this type of shooting, (subsonic 100yds, 200yds, 300yds) I like to see an SD of about +/- 1/2% (+/- 5fps) for the farthest targets. Even that SD gives a vertical spread of 1moa, meaning only about 1/4 of my groups will be under 1moa vertical spread. So, at best, that case means it's three fourths luck to get a 1 moa group. And that assumes everything else was perfect (no wind, no wobble, etc). I guess we really need an SD of +/- 2fps for an even chance of 1moa at 300yds. From what I have seen so far at long range airgun competitions, the more reasonable goal is to be able to hit 4moa steel, 1st shot and almost every shot. Hitting 1 foot wide by 15" tall consistently (including 1st shot) at 300m is good for a subsonic airgun.

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Even with expensive 22rf ammo tested for precision .... My vertical is more like 2.5 moa though at 300Y because the ES is 30-ish fps.
...

Click to expand...

I don't know about an ES of 30-ish fps, because that does not tell me anything about probability. But for this type of shooting, (subsonic 100yds, 200yds, 300yds) I like to see an SD of about +/- 1/2% (+/- 5fps) for the farthest targets. Even that SD gives a vertical spread of 1moa, meaning only about 1/4 of my groups will be under 1moa vertical spread. So, at best, that case means it's three fourths luck to get a 1 moa group. And that assumes everything else was perfect (no wind, no wobble, etc). I guess we really need an SD of +/- 2fps for an even chance of 1moa at 300yds. From what I have seen so far at long range airgun competitions, the more reasonable goal is to be able to hit 4moa steel, 1st shot and almost every shot. Hitting 1 foot wide by 15" tall consistently (including 1st shot) at 300m is good for a subsonic airgun.

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I like the "balance" your custom .257 has. Not much recoil/=more so low gun upset, great shot count for the FPE, slug with a decent BC, decent velocity, and all with good precision.

I would love to see you cut that group in half size wise. It looks doable.

I need to get mine working. Very intriguing.

mike

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I would love to see you cut that group in half size wise. It looks doable.

I need to get mine working…

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If I shoot a bunch of five shot groups, and pick the best one, I"ll eventually get a half size group. I’m more interested in the typical accuracy and group capability. What do you need to get working? A .257?

I now have a digital pressure gauge on the gun. When shooting for accuracy, I try to keep it within a +/- 10psi range, and I used slugs within a +/- 0.4gr range when I shot that last group. I could tighten up those tolerances a little more and it might improve my odds a little. But I think that this gun is shooting about as accurate as can be reasonably expected. I just want to go for doing it consistently. Anything much better for the short term is going to involve some luck.

Amazing Work! I'm very impressed with that gun of yours! I've been planning on putting a .257 into my collection soon. I've reading up on barrels, platforms and ammo. Possibly this spring I'll have one. I will be happing if it was only half as accurate as the one you have! LOL!

Scotchmo,

Agreed!

But I also enjoy when i shoot a magic group. When the fifth snuggles right into the small group…for me, there is nothing quite like it. 


no magic below…

Scotchmo,

Agreed!

But I also enjoy when i shoot a magic group. When the fifth snuggles right into the small group…for me, there is nothing quite like it. 


no magic below…
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A chronograph might tell you. What is the velocity and velocity spread you are getting? Those slugs at 900fps +/-1% can have a vertical dispersion of greater than 2". So that's as good as can normally be expected outside of a lucky (magic?) group. That's great consistency for 187yds with a subsonic projectile.

I polish all of my barrels very gently and carefully with JB bore paste…I rarely clean my barrels after that process.

It is very cool showing the slugs afterwards. I’ll be honest, I am shocked by the difference. A smooth barrel is a good thing.

mike