454 ammo and Chrony Number s

[Powers92]

In search of bulk ammo at a relatively inexpensive price I decided to try the HS 454 200g PHP rounds.

Also this was an opportunity to test out Caldwell Chrono that I got for a cheap price.

My power wheel is all the way twords the buttstock.
Chrony is 5 feet from the muzzle. I don't know if it makes any difference but I had only one sunshade on the chrony.... the front one. 

Here's my shot strings.
454 200g PHP

1st at 3600ish (might have been a bit over)
745 fps

2nd at 3400psi
1036fps

3rd at 2800psi
1022fps

4th at 2600psi
1008fps

5th at 2409psi 
978fps

Filled up and started at a lower psi.

1st 3200psi
857 fps

2nd at 3100
1024 

3rd at 2900
1017

4th at 2600
992

5th at 2400
958

6th at 2200
957 fps

Shot string number 3
1st 3200psi
1033fps

2nd 3000psi
1020fps

3rd 2800psi
997fps

4th 2600psi
976fps

5th 2400psi
946fps

6th 2200psi
925fps

7th 2000psi
909fps


Now due these look normal to you guys? 
There's on average 200 psi loss per shot.

I'm going to use this primarily for hunting.
The accuracy at 50 yards was not phenomenal (some of that is due to my shooting) but satisfactory I think on deer, coyote and coon out to 50yards. Although my hunting shots are usually under 50yards. The 454 rounds fit all the way inside the chamber with some side to side give. 


For a hundred yard test I hope to tighten up the groups a bit. Any critique and advice is welcome.

 

[Loren]

The accuracy at 50 yards was not phenomenal (some of that is due to my shooting) but satisfactory I think on deer, coyote and coon out to 50yards. Although my hunting shots are usually under 50yards. The 454 rounds fit all the way inside the chamber with some side to side give. 


For a hundred yard test I hope to tighten up the groups a bit. Any critique and advice is welcome.

The bullet should insert into the chamber and stop when it touches the rifling. If the bullet is sliding into the chamber and is loose then it is too small in diameter (which I would expect for a .454 dia bullet) for a .457 Texan. That will be a BIG part of your accuracy problem.

.457 Texan at 100 yards. First time out with the rifle. I think you can expect like results with a well fitted bullet.

 

[Airgun-hobbyist]

It looks like you figured out that the lower fill pressure produced the best, most manageable shot string. A fairly consistent shot string dropping off like that is easy to compensate for as you shoot. As Loren said, getting some .457 diameter ammo that for the bore will tighten up the group size. Check out the selection of NSA swaged slugs, offered in three different diameters for the different .45 barrel's. Because that gun is shooting that strong already with those 200 grain slugs, you may want to go to a bit heavier slug to get some down-range knock down power. The 254 and 302 grain slugs have been reported to be pretty accurate for long range shots.

https://nielsenspecialtyammo.com/collections/45-cal

 

[Powers92]

Yeah I figured the 454 diameter would rob me of some accuracy. But, HSupply has good prices on 100 rounds. So I will order some 457 rounds to plink with/ hopefully find some accuracy from sub-par ammo. 

I have used NSA ammo 350BTHP and the 254BTHP. Expensive rounds to use just for fun shooting.

The 350BTHP have a 8 some inch drop at 100 yards. Easy to compensate for bit from 3600psi fill I get 3 good shots. 

Now lets say that the 254 NSA rounds travel 950 fps that would yield some 400+ fpe. And approximately 5 good shots on a fill. ( I am looking at this as my go to hunting ammo).

Why would my first shot travel consistently at lower fps then my second or fallowing shots. And how does one deal with that when hunting? 

 

[Loren]

First shot is probably low because of the light bullet not providing enough back pressure on the valve for the max filled tank pressure. I think if you had a heavier bullet you may not see such a big reduction on that first shot.

 

[Powers92]

So heavier bullet.....and or power wheel adjusted forward.

What has better knock down power/penetration a heavier bullet travelling at a slower rate or a lighter bullet at higher speed. Assuming that the only difference between the two rounds is their perspective weight?

At what speed do you achieve better penetration and mushrooming of the hallow point? 

 

[Airgun-hobbyist]

So heavier bullet.....and or power wheel adjusted forward.

What has better knock down power/penetration a heavier bullet travelling at a slower rate or a lighter bullet at higher speed. Assuming that the only difference between the two rounds is their perspective weight?

At what speed do you achieve better penetration and mushrooming of the hallow point? 

Because airguns do not have near the velocities of powder burner's, sacrificing some speed to get a heavy and big slug down range will hit harder and carry itsi momentum going through the hide, ribs and and flesh better. Check out the Strelok Pro app for your smart phone. It is a ballistic calculation app that you can play with, manipulating the numbers for each slug.

For example, in these all that was changed was the weight of the slug. The slug shoots at 950 FPS for both. They are the 254 and 302 grain NSA HPBT slugs. The 302 grain slug has the higher muzzle energy out if the gate, and at 100 yards is still above the starting energy of the 254 grain slug.

 

[Loren]

Kind of true, but that is not a completely fair comparison. The 254gr will have higher velocity than the 302gr. Probably 50-75 FPS faster.

My goal would be an accurate mid weight 250-350 grain bullet shooting in at 900-1000 FPS

His is real world numbers.

Your 200gr at 1025 fps. equals 467 FPE

My 289 gr at 940 fps equals 567 FPE. and the 289 gr is going to be a longer bullet so will have a better BC, so will retain the energy better than the shorter 200gr bullet.

Ultimately find a bullet you can accurately hit the target with at distance. The 45 caliber HOLE will do the rest.

 

[Airgun-hobbyist]

Kind of true, but that is not a completely fair comparison. The 254gr will have higher velocity than the 302gr. Probably 50-75 FPS faster.

My goal would be an accurate mid weight 250-350 grain bullet shooting in at 900-1000 FPS

His is real world numbers.

Your 200gr at 1025 fps. equals 467 FPE

My 289 gr at 940 fps equals 567 FPE. and the 289 gr is going to be a longer bullet so will have a better BC, so will retain the energy better than the shorter 200gr bullet.

Ultimately find a bullet you can accurately hit the target with at distance. The 45 caliber HOLE will do the rest.

Very true Loren. I was being overly general, just showing the difference between projectile weights with the same speed, BC, etc, to give examples of retained energy down-range of a heavier slug. It was definitely not real-world comparison, as everything changes with each given projectile and it's characteristics.

 

[Loren]

You are spot on with heavier can be better, but wanted to keep some prospective for our new big bore shooter.

Lots of variables to play with, which is what makes it challenging and fun.

 

[Powers92]

I have used both of the NSA 350 and the 254 slugs and they both do well.

NSA will use for hunting and 254 are what I am looking at as a deer slug. I will test out the speed of the 254 BTHP next time I get out to the range. 

Hunter supply are cheap and somewhat inconsistant as far as some slugs fit tight and others a little loose. I have gotten some accuracy but maybe if I go up to 455-457 it will improve.