FPS powder reloading question/jabber

[j.galloway]

Sorry about the long post, but I like figuring and playing with numbers 

Recently I bought a Chrony Beta to compliment my reloading arsenal.
http://www.amazon.com/Chrony-9436-Beta/dp/B000JZ5VPU/ref=cm_cr_pr_product_top

I set it up and it was working fine

I loaded up some fresh 223 rounds using Nosler 55gr varmageddon and 55gr ballistic tips and headed to the range.

using a savage stevens .223 22" barrel 1-9 twist.
Noslers book says they used a 1-12 twist 24" barrel

Loading  with IMR 4895 23.5gr the book says it should be going at 2988.
Loading  with IMR 4895 24.5gr the book says it should be going at 3083.


Here is the 
result... all in fps

23.5gr4895  Ballistic tip
2647
2640
erred
2693

23.5gr4895  varmageddon
2695
2676
2679

24.5gr4895  Ballistic tip
2827
2779
2790

24.5gr4895  varmageddon
2844
2856
2840



just for the of it
I fired one partition I had loaded about 6 months ago, just to see,
the book claims a 60 gr partition IMR4895 23.5 should push it at 2860
I actually got 2590

The weather conditions at the time was 47F 85%humidity 42%dew 30.26in at an altitude of 1100ft

so.. is this the norm for a barrel that's 2" shorter... about 300fps slower on average?

I noticed another difference... the primer they used where rem, I am using CCI 400. I heard primers would make a difference accuracy wise, but never really thought about if primers changed velocity?


I have some 30-06 rounds ready but I haven't tested them yet, I was hoping too after this weekend after my new scope gets delivered. My barrel is again 2" shorter than whats in the book... should I be expecting a large fps drop like that? I actually found this real nice area to do some long range shooting in, I was hoping to use my 06 for several hundred yard shots, but I find that most rounds only will expand at 1800fps+, so that's limiting distance (or is it? ) .

If the book is right, (and using the available powder and bullets I have) I can fling some 180grains at 2400fps  (ehhh I know its on the slower end of the 180s even in the book, but it was the only powder available at the store) anyway it would drop to 2100fps and make effective range less than 200yards... that extra 300fps would give me another 50 yards for this particular Sierra.


The projected future round that hopefully will be coming soon, will be using different powder and higher BC bullet and a medium load. The claim is about 2650 fps which would put 1800fps around 500 yards, which for all practical purposes, at 1MOA is just about the furthest shot the rifle alone can make on any accurate shot on coyote or deer. If however we drop 300fps, it will drop 1800fps down to 350yards. In that case it might be better to look at 150grains just to keep fps up. (bad timing though after I have already ordered 300 180 grains    )


annyyway... long story short, am I doing something wrong, or why am I loosing 300fps? or am I loosing fps anyway, or is it possibly the Chrony is not calibrated, or is it the shorter barrel and its something Ill just have to live with?

[JimmyHoffa]

I think the difference in barrel length should only account for about 30 fps difference. Yes primers affect velocity, maybe upto 50 fps, sure more is possible.  The lighter primers depend more on powder igniting adjacent powder than the primer, so it takes a little longer for the initial pressure.  I think the big factor you describe might be temperature.  Could also be seating/crimping/jump. 

[AWS]

you might want to try some winchester whitebox loads or any factory load with a known velocity to check your chronograph.

[high country]

How far out out is your chronograph? Did you shoot at long range to see who's numbers were right? I would fire a few other guns over it to see if the calibration is good, but don't be surprised if it is......chrongraphs have made many guys cry.

[suga]

you might want to try some winchester whitebox loads or any factory load with a known velocity to check your chronograph.

I had to send my unit back to the factory to be calibrated - happens with some of them.

[j.galloway]

How far out out is your chronograph? Did you shoot at long range to see who's numbers were right? I would fire a few other guns over it to see if the calibration is good, but don't be surprised if it is......chrongraphs have made many guys cry.

 

you might want to try some winchester whitebox loads or any factory load with a known velocity to check your chronograph.

I went out today, I brought my 06 along. Unfortunately I do not have any factory ammo for it, (actually that rife has never fired a factory round yet  ) Good news though... I found someones 223 rounds on the ground, hopefully can clean them up and be ready for a few more rounds

weather:
50F 80%humidity, 44Fdew @ 30.25

but I do have factory Hornady 223 40gr vmax. It claims 3800 fps at muzzle.


I have reloaded 06 rounds slightly warmer using imr 4895 49 grains with 150 grain nosler BT and accubond (only shot the BTs) which by the book should result at 2837

here's the results
Hornady 223 vmax 40grain
error
3437
3440
error

30-06 150grain BT
2622
2637

I think the difference in barrel length should only account for about 30 fps difference. Yes primers affect velocity, maybe upto 50 fps, sure more is possible.  The lighter primers depend more on powder igniting adjacent powder than the primer, so it takes a little longer for the initial pressure.  I think the big factor you describe might be temperature.  Could also be seating/crimping/jump. 

I use Lee Deluxe for 223 and (RCBS for 06) and they don't crimp, but I do load the rounds at near-max COL of 2.25, because for some reason the rifling doesn't start until half inch past max COL, which is interesting since on my 06, a nosler BT will jam on lands at 3.32 COL so I backed off to 3.28. So I could try seating the rounds deeper to see how much that effects fps, but really I would rather have a slower bullet than a less accurate bullet 

So it seems to be around a 300ish-fps lower than quoted.

Tomorrows' supposed to be rainy so Sunday what I'll do is sight it in very precisely at 200yards, then make some long range 700-900 yard shots and see how they compare to this ballistics program. 

[high country]

How far from muzzle to chrony?

[j.galloway]

How far from muzzle to chrony?

Oh sorry forgot to answer that... it was 10' exactly, from barrel to first.. eye?

[duckmen1]

One thing to keep in mind too is your barrel length. If you have a shorter barrel than what was tested for the test in the book than you will be going slower. My 300 wsm has a 3 inch barrel difference than the tested guns resulting in slower speeds. I have a 23 inch and they tested with 26 inch. Will make a big difference

[Fl0und3rz]

I forget where I got these rules of thumb (maybe Chuck Hawks):

For rifles with muzzle velocities in the 1000-2000 fps range, the change in velocity for each 1" change in barrel length is 5 fps. 
For rifles with muzzle velocities in the 2001-2500 fps range, the change in velocity for each 1" change in barrel length is 10 fps.
For rifles with muzzle velocities in the 2501-3000 fps range, the change in velocity for each 1" change in barrel length is 20 fps.
For rifles with muzzle velocities in the 3001-3500 fps range, the change in velocity for each 1" change in barrel length is 30 fps.
For rifles with muzzle velocities in the 3501-4000 fps range, the change in velocity for each 1" change in barrel length is 40 fps.

So for the barrel difference, you would expect about 40 fps loss. 

Primers can be a factor.  This link shows differences on the order of 50 fps, but it will depend on which primers compared, the cartridge, and the load (powder, bullet, etc).

http://www.accuratereloading.com/primer.html

The same link shows about a 50-80 fps difference (slower) comparing whatever the ambient was to loads that were frozen, then fired. 

Another factor is that, all else being equal, a slower twist barrel should see higher velocities than a faster twist.  I don't know that there is a rule of thumb, because there are so many variables related to the barrel, the bullet, etc.  But I would expect a velocity drop from numbers that used 1:12 versus the 1:9 that you are using.  I just can't quantify it or give a ballpark estimate.

Another thing that was not clear was whether the Nosler numbers you used were for that exact bullet, for a different bullet of the same weight, or a composite of many different bullets that Nosler offers in that weight.  I would not expect different bullets to have the same velocity numbers, but I would not necessarily expect bullets from the same manufacturer and of the same weights to be too drastically different, unless you were using say a solid bullet with a larger bearing area (more friction) versus data obtained with a traditional jacketed lead core bullet.   

[yorketransport]

My understanding is that you only fired one of the 60 gr partitions loads over the chronograph, is this correct? If that's the case then the single shot is statistically insignificant.

Chronographs are finicky  machines. How was your cloud cover? Did you have the diffusers on there? Had you moved the machine between this shot and the previous readings? Did you shoot through the screens at a different height? Was the one shot you fired possibly an under charge? It seems like a lot of little things could have added up to the low reading. The only way to know for sure is to load up some more and try it again.

Andrew

[j.galloway]

My understanding is that you only fired one of the 60 gr partitions loads over the chronograph, is this correct? If that's the case then the single shot is statistically insignificant.

Chronographs are finicky  machines. How was your cloud cover? Did you have the diffusers on there? Had you moved the machine between this shot and the previous readings? Did you shoot through the screens at a different height? Was the one shot you fired possibly an under charge? It seems like a lot of little things could have added up to the low reading. The only way to know for sure is to load up some more and try it again.

Andrew

Yes only took one shot, I only have a few partitions left and its little hard to find supplies right now.  oh and every round I load, I usually have to powder measure throw .1 grain low and use a powder tickler to bring it up to weight, and I weigh every single charge. (not because I have to, I just want to )


Anyway, it is usually always cloudy over here  and yes these where 2 different locations, this last time I went to the local pit at an altitude of around 400ft. I had defusers on both times, except yesterday it kept erroring, so I took them off and then they finally started recording.

so speaking of finicky, I found this

http://www.snipershide.com/2012/11/easy-chronograph-set-up/

I noticed that he really precisely measured the laser above each eye. I only used a level which of course is only a rough level, but over 10' it probably will have made it very in-precise.

That then add barrel length, ambient temp, primer, twist rate and imprecise method of measuring, may have all changed the fps

Another thing that was not clear was whether the Nosler numbers you used were for that exact bullet, for a different bullet of the same weight, or a composite of many different bullets that Nosler offers in that weight.  I would not expect different bullets to have the same velocity numbers, but I would not necessarily expect bullets from the same manufacturer and of the same weights to be too drastically different, unless you were using say a solid bullet with a larger bearing area (more friction) versus data obtained with a traditional jacketed lead core bullet.   

The nosler book says both
55gr Solid Base Ballistic Tip (orange)
-and-
55gr CT Balllistic Silvertip both on the same page.

I assume the BT is the varmint BT, now that you mention it, I look at the difference between a 'solid base BT' and 'CT ballistic ST' and in the front of the book (pg 10) the silvertip has this lubalox exterior coating, which claims it "reduces fouling pressure and friction between bullet and bore providing longer barrel life easier cleaning and enhanced accuracy"

Suppose this coating could also effect speed, since there seems to be an, (albeit slight) difference between BTs and Varmageddon just from the flatbase/boattail design.

[high country]

One thing to keep in mind too is your barrel length. If you have a shorter barrel than what was tested for the test in the book than you will be going slower. My 300 wsm has a 3 inch barrel difference than the tested guns resulting in slower speeds. I have a 23 inch and they tested with 26 inch. Will make a big difference

You might be very surprised that there is actually little difference. Frank green and Charlie sisk did tests on a single barrel cut down and shot each cut and it will surprise you. The difference from one barrel to another is usually the factor.....some are just faster than others.

[snowpack]

Do you know someone else with a chronograph?  If so, then just put them in line with each other and shoot through both at the same time.

[j.galloway]

Do you know someone else with a chronograph?  If so, then just put them in line with each other and shoot through both at the same time.

Aww they delayed my shipping, now my scope wont get here till Tuesday 


Anyway I know one and but it would be a friend of a friends so unlikely to get access to it,

I'm thinking the best test might be to zero at 200 then try for 800 yards and check bullet drop.