Balistic information on iStrelok .223

[Blacknsilver]

I have just started working on load developing a 77 grain Sierra tipped match king bullet. N140 powder 22.2gr Lapua case. I put in the ballistic information into iStrelok being 0.415 ballistic coefficient 2450 ft./s and the remainder of the information needed I then added 600 yards to the calculator and 10mph full value wind. It came up with

128in of drop

42in windage

 

I did the same range with the 53gr v-max - BC 0.290 and 3300 fps H4895 powder 3300fps

It came up with

80 in of drop

44in windage

 

The TMK was getting delvloped for the range of up to 600 yards but if the 53 gr pill can do what the app says then why bother with the 77s?

[treetop]

I run the 53's out of a 20" barrel @ 3150 fps

And that sounds about right..

 

I use strelokPro & it's not far off, I do have to tweak it a bit as I fond that the BC given is not exactly true,

[bradders]

Firstly, you're about 2-2.5gns down on what you can push those with and your velocities are 250-300fps less than what is achievable, and if you put those numbers in you will see a much bigger difference

 

Also bear in mind that max velocity for an MoD range (if that's what you mean) is 3250fps

[Blacknsilver]

The load on the 77gr I started at 22gr and worked my way up. I stopped at 23 going up in .2. I am getting a degree of crush even at 22.2. Only slightly but would hate to hear what 24.2 would sound like.

22.2 gave all shots through same hole. I have loaded up 10 round to see how they shoot. After checking the difference between the 53s which are shooting great I am wondering if I should bother developing the 77s.

[bradders]

The load on the 77gr I started at 22gr and worked my way up. I stopped at 23 going up in .2. I am getting a degree of crush even at 22.2. Only slightly but would hate to hear what 24.2 would sound like.

22.2 gave all shots through same hole. I have loaded up 10 round to see how they shoot. After checking the difference between the 53s which are shooting great I am wondering if I should bother developing the 77s.

Compressed loads with heavy bullets and extruded powders in .223 are very common and nothing to worry about

[Blacknsilver]

I need to twiddle with the figures on the app and see if it's worth persevering with.

Firstly, you're about 2-2.5gns down on what you can push those with and your velocities are 250-300fps less than what is achievable, and if you put those numbers in you will see a much bigger difference

 

Also bear in mind that max velocity for an MoD range (if that's what you mean) is 3250fps

I have the application for for Altcar rifle range where I hope to go. I am on the border line with the 53gr. I am just guesstimating at the fps as I have not yet put the 53gr on the chrono yet.

Would the range chrono your rounds?

Thanks for the heads up.

[bradders]

I need to twiddle with the figures on the app and see if it's worth persevering with.

I have the application for for Altcar rifle range where I hope to go. I am on the border line with the 53gr. I am just guesstimating at the fps as I have not yet put the 53gr on the chrono yet.

Would the range chrono your rounds?

Thanks for the heads up.

No the range wont crono anything, and to be honest it is something that would probably never be checked, but as with all things if something was to happen....then someone has to be held to account

[Blacknsilver]

I agree. The book stops somewhere. And I don't fancy it being with me. I am

Waiting for the rental service to kick off so I can try out the V3 chrono. The last one I used was such a nightmare. Can't go through that pain again.

[bradders]

I think your 53gn wind drift is wrong, I

[Blacknsilver]

It's coming out at 44.2in at 600yds with 10mph and 90' wind

No idea how accurate it is. Only used it to 350. But that was on the .204 round.

[VarmLR]

Something doesn't sound right at all. I don't believe that a 53gr will perform anywhere near the potential of the 77 TMK at 600 yards, in fact I know it won't as I've tried it! I was getting close on 2650fps from the 77TMK with N140, and pushed that harder using RS50 (over 2700fps) and that wipes the nose of my 60gr rounds zipping out at close on 3200 fps at 600 yards, never mind the lower BC 53gr rounds. Doesn't sound right at all. The 77gr TMK is a good accurate and very consistent bullet to 750 yards in the .223. The 53gr, any 53gr, is not.

[Blacknsilver]

That's what it can't work out. Put the relevant info into the app and that's what it's coming up with.

Like you say something isn't right.

[VarmLR]

I wonder...are you using the manufacturer's claimed G1 profile for the 53 gr? G1 won't work well past 300 or so yards I've found. It's way too over optimistic for the claimed BCs in G1 once past that range. G7 is a better fit for many modern bullet BT profiles. Get out and shoot some, then calibrate your app based on actual drop data and measured velocities. It's the only way of fudging app data to more closely predict accurate trajectories imho. I usually end up modifying either BC or MV (or both!) until my measured drops are within spitting distance of app predictions.

[gbal]

Mark makes some good cautions here-the MV for the 77s is up to 350 fps low (all data given here are to SAAMI specs,not estimated,fudged,or 'adjusted'....Strelok is actually quite accurate,for what it is,but can only do the maths on the input data;and the data for the 53 g BC might be optimistic too....Varm's general point-BC drops with fps,but lets assume it does so about the same for all these loads,or near enough.

 

So what does 77g in a 223 do (all data 24 inch barrel-again comparative for all data,so iif a differnt rifle ec,we have toassume a similar decrement/increase....the comparisons still hold (the actual inches might vary a little):10 mph wind,drop/drift" at 600 given

 

Cor Bon 77 HPBT @2800 BC .350. 92/44

Rem 77MK. @ 2790. BC .362. 91/42

Fed 77MK. @ 2720. BC.372. 94/42

B Hills 77 SMK. @ 2750. BC .390. 89/39

Nosler 77 CComp. @2600. BC.340. 112/51 (note consistency with first 4,then when Nos BC and MV drops significantly,d/d increases accordingly.

 

Let's try the Vmax-I have no 53g data,but enough 50 Vmax to get some idea...

 

BHIlls 50 Vmax @ 3300. BC .242. 86/58

Fiocchi 50 Vmax. @3300. BC 242. 85/58. Consistent.

 

What does more velocity do-look at same 50 Vmax in 22/250(same 224 cal,so can comare on MV)

 

Cor bon 50Vmax @ 3700. BC.242. 64/49

Hornady 50Vmax @ 3800 BC.242. 60/47

B hills 50 Vmax. @ 3700. BC .242. 64/49. Yep,very consistent 100fps has a small effect.

 

And 22/250 with the 53g Vmax...

 

Norma. 53 V max @ 3700. BC .237. 64/50 Yep,note comparison with the 50g

Cor Bon 53Vmax. @ 3550 BC .240. 72/52. And 150 fps make a differnce...at 600y

 

Whew! But that allows most sensible comparisons to be made,looking at MV and BC, where it is reasonably comparable,and what changes in either/both really affect drop/drift.

Note the consistency (minor rounding up),across manufacturers-this isn't fudged data,twisted to fit some dubious assumed oher 'input' data/wishful thinking etc-not deliberate,of course...but such inputsare error prone.Strelok isn't- but can only compute on the input. If your actual data isa little differnt,then remember rifle etc variances-and those would allpy near enough equally over loads.

 

The essential issue is these data are comparable wrt 77g performance over 50/53 vmax performance in 224 cal at 600y (77TMK will do slightly better than the 77SMK data,too-just making the point even more so,or at least minimising any advatage in BC the 53 might have over the 52 Vmax). But the analysis is it's pretty close to 'apples to apples'.

 

TAKE AWAY: Yes,it is possible to so underload the 77g as to lose any advantage over 53g,but when both are loaded to SAAMI specs,the 77 performs rather well over the lighter bullet ballistically at 600y,especially for reduced wind drift.

 

Physics holds true,again.

 

gbal

[VarmLR]

Yep...looking at "guesstimated" MV's you're way under on the 77's. I must have been blind not to read that before but I had only skim-read so mea-culpa.

 

I did some tests a week or two back on these and seated to 2.29 I was getting 2640 fps with 23gr RS50 which was my accuracy load. At 2640fps, the bullet will still be above transonic at 700 to 750 yards which is more than the 53gr will be.

 

You'll be a little down on that with N140, but I would expect closer to 2550fps using 22.5gr N140 under the 77gr, not 2450.

 

I loaded up to 24.2gr without any pressure signs for about 2850fps (again, RS50) so I would expect 2750 to 2800fps using N140 loaded up a bit from where you are. It wont match RS50 for velocities but should still do well and produce an accurate load.

 

It's a pointless exercise getting worked up about ballistic performance, or lack of, when you don't actually know what your MVs are. You need to invest in, or borrow a chrony instead of wasting time/energy on guesswork.

[Blacknsilver]

Agreed on the guess work. It's all a learning curve. What I did was look at the reloading books starting MV and the max MV and looked at what I had loaded and guessed at what it would be. It was done purely to get an idea. Mistake made.

I stopped at 23gr as I mentioned before about the 'crush' felt and hearing while seating the bullet.

I tested the 22.2gr last night and worked well on grouping at 100.

I will load a few more past 23gr and see what I find.

Thanks again for all help given. Well appreciated.

Mark

[deadcenter]

I think you are doing well getting good accuracy from 53gr and 77gr in the same rifle. What twist is it?

 

My 1:9 twist shillen barrel loves 69gr, hates 55gr and groups open up with 77's.

 

Slightly off topic I know, was just curious about your set up.

[Blacknsilver]

It's a 1-8 twist and 26in Stainless Archer barrel.

Struggling to upload pictures. Says file to big.

[deadcenter]

Sounds nice, no need for pics, thanks for the info. Good thread

[VarmLR]

Agreed on the guess work. It's all a learning curve. What I did was look at the reloading books starting MV and the max MV and looked at what I had loaded and guessed at what it would be. It was done purely to get an idea. Mistake made.

I stopped at 23gr as I mentioned before about the 'crush' felt and hearing while seating the bullet.

I tested the 22.2gr last night and worked well on grouping at 100.

I will load a few more past 23gr and see what I find.

Thanks again for all help given. Well appreciated.

Mark

 

I reckon you should find a good node between 22 and 23.5 loaded to mag length (which for mine is about 2.29"). I like the TMKs a lot (they're remarkably consistent in manufacturing tolerance) and for mine, the accuracy node for RS50 was 23gr. I usually look for the lowest vertical dispersion as a good pointer for being on a node.

[Blacknsilver]

Ok. So I loaded some more using same seating depth etc and moved up the powder increments again in .2s 

23.8gr of N140 seems like a possible. I will load 10 at that and then if it's shooting the same borrow a chrono and test at 300yrds 

 

[VarmLR]

Wow..that's quite a stiff load of N140 for a 77 TMK!  Do you know your  MV at that?  I was using 23.6 N140 with the 69 TMK and that was quite a zippy load.  By contrast, I'm using 23gr RS50 with the 77's for about 2650 fps and bug hole groups.  I find that with both bullets (ie 69 and 77 TMKs) they like a jump and performed better loaded to mag length than close up to the lands.

[Blacknsilver]

Don't know the MV. Looking to borrow a chrono soon. It's .4 under max load. Not showing any pressure signs. 1.738 to ogive. OAL is 2.263 

i have not tried any other seating depth. 

[VarmLR]

That seating depth should be fine.  They're designed for mag length and seem to jump really well.  I'm trying out some tomorrow at 2.29 with some RS50.

[Blacknsilver]

I have a AI mag system. There is a bit of crush when loading. I might play with seating depth after loading 10 and see how they fair.