Fps variation, I don't get this

U

Ub3rn00ber

New member
Hello all! I finally got a Crono and was very disappointed in the results with my 30-06 reloads.

I had 113 fps variation with 12 shots.

Every shell is a fire formed winchester, trimmed to specs. I am using 53.5gr of 4831, and 180gr hornady sst .308. This is the second load on the brass, every charge was thrown with a lyman auto, +.1/-.0 so I have very little variation. Every bullet was seated the same to +/- .001, OAL 3.233 +/- .001. Outside tempature about 100F. Crono set about 17-20 feet away, with IR shades.

I don't know if it matters but data started recording after 5 shots, it was not allowed to cool approximately 45-60 seconds between shots.

Below is a screenshot of the data.




Any advice, thoughts? Holding 1.25 5 shot group.

Edit: loaded on rock chucker single stage.
 
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Did neck tension feel any different?

Is the brass all from the same lot?
Did you weigh the brass to see if it came from different drawing presses?
Have you checked case capacity (grains H2O)?

Edit: There's at least a 130 fps spread in that data provided.
 
Neck tension was the same.

The lots shot be the same I bought the brass new from winchester, all in one bag.

I didn't weigh or check capacity.

Yea I missed that 2186 one.

So I'm correct in thinking this is too large a spread?
 
Extreme spread is a little high at 130 fps for sure. But the standard deviation is 44 fps. That's about what you'd expect from bargain commercial hunting ammo.

But what I think is happening is that you are getting inconsistent ignition, try a faster powder like 4350 or try magnum primers.

Jimro
 
My guess is that you're not up to operating pressure yet. The slow powder combined with low pressure is giving a wider deviation.
If you really want to operate at that velocity, switch to 4895.
 
I use H-4350 in my 30-06's and I set my chronograph @ 15'.

I'm not sure who's data your using and looking at Hodgdon data for H-4831 their start load is 54gr with 180gr Sierra and IMR-4831 is 53gr.
 
Hello all! I finally got a Crono and was very disappointed in the results with my 30-06 reloads.
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If I shot 12 rounds and all twelve rounds went through the same hole I would not turn the Crony on. So I ask; "How is accuracy?", Are the slow ones hitting low and or to the left or right and then there is high or down the middle with occasional flyers. If you had flyers were they running slow, fast or about just about the same speed.

Every shell is a fire formed Winchester, trimmed to specs.
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Fire formed and then what? Necked sized? Full length sized back to minimum length?

Forgive: Found it,
Holding 1.25 5 shot group.
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That leaves another factor; what rifle are you using. 1 1/2 groups at 100 yards could be the best the rifle is going to do and then there is the ability of the shooter and his methods and techniques.

F. Guffey
 
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Did neck tension feel any different?
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Neck tension was the same.
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More than curious; how did you measure tension?

I am the fan of bullet hold, I want all the bullet hold I can get. It is not a problem for me but about (+/- a few) 40 pounds is it. And then I have never wondered about the difference in 40 pounds of bullet hold and 10 pounds of bullet hold when it comes to time. And then there is the running start, I want my bullets to have that jump.



F. Guffey
 
With 180 gr bullets you should be getting around 2600-2700 fps. Closer to 2800 fps is an upper end load and many guys willing to push the envelope get closer to 2900 fps.

If the case isn't close to full the empty space allows powder to be in different positions when fired resulting in erratic speeds and accuracy.

I don't use this powder, but get the best accuracy with a powder that will pretty well fill up the case so it doesn't have any room to shift.
 
Fire formed and then what? Necked sized? Full length sized back to minimum length?
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Neck sized

If the case isn't close to full the empty space allows powder to be in different positions when fired resulting in erratic speeds and accuracy.
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This is a good point I didn't think about that, it isn't full.

Not knowing what powder is used IMR or H ?
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H

That leaves another factor; what rifle are you using. 1 1/2 groups at 100 yards could be the best the rifle is going to do and then there is the ability of the shooter and his methods and techniques.
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Rem 770
 
The spread is not terrible. Not great, but not terrible.
Possibilities in my opinion:
1. Poor load choice. Increase charge. Change powders.
2. Check case neck thickness.
3. Change primers
4. Weigh primers and use matched weight primers.
5. Load a box using Norma Brass.
 
The spread is not terrible. Not great, but not terrible.
Possibilities in my opinion:
1. Poor load choice. Increase charge. Change powders.
2. Check case neck thickness.
3. Change primers
4. Weigh primers and use matched weight primers.
5. Load a box using Norma Brass.
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1) I might go with 4350 as I just picked up a bunch at $14/lb
2) I will recheck them, after I fire formed I didn't do a second check
3) for the rest of the 4831 I have ill try some mag primers, as that is the cheapest fix.
4) I didn't even know people did that! does it make that big of a difference? A primer is what 2-10% of the charge depending on the caliber?
5) While I want accuracy I cant justify spending more on brass than I can buy OK factory loads, around here they run about $1-$1.15 a case for Norma. I can get the Winchester for $20/50pc

Does Winchester brass really have that much difference in tolerances?

Next go around on reloading these, ill try weighing every primer, case, and bullet, and use only the ones that are very close. Ill report the results with the 4831 as well as try some other powders.
 
Does Winchester brass really have that much difference in tolerances?
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Yes it does sir.

I understand you not wanting to spend the money on Norma or Lapua brass, the stuff is expensive, but in the end it is a much better product and worth it in my opinion. I only have one rifle left that I shoot loads that use Winchester brass and that is only because nobody else made or makes brass for the 7 WSM!
 
Really with a solid powder change like going to 4350, you will see differences in velocity and consistancy.
Switching to a magnum primer may or may not help, with some powders it's like chasing your tail trying powders and mag primers, and weighing brass is an awful lot of trouble for a fella just wanting to wring sub moa and low velocity spreads.
Neck tension, case capacity, and proper powders for certain bullets makes easy work in finding a consistant load.
If I were to be a little forward I take it your getting this load from the Hornady manual?
Sometimes I have a certain bullet and everything the manufacturer manual gives me leads nowhere I want to end up in the end, which is a consistant accurate load.
Try Remington and Federal brass, if it doesn't help and your still chasing the dream of making those 180 grain bullets consistant then look at another manual, sometimes it will offer different suggested loads for same weight and designed bullet, say maybe the Btip from Nosler, ( not same bullet, but close data).
I have a cousin that has a load for his 3006 featuring 150's in the Btip, and I have always used IMR 4350 with those to satisfactory results, he only had, at the time Rl19, and it works nicely.
Make absolutely sure the barrel is not copperfouled too much that will also screw with a chronograph, I know first hand.
 
The brass may not be the issue here.
But I ended up running with it, after I saw the question asked...

Does Winchester brass really have that much difference in tolerances?
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Yes, it does.

Sticking with weight and capacity, and ignoring neck thickness, runout, etc...

If one weight-sorts and/or checks capacity of a large (new!) lot of the common brands of brass, one will often find multiple peaks in the data, indicating that the lot includes brass from multiple drawing presses. ...And all presses are different, so they kick out cases that differ slightly.


For cartridges where it matters, I sort all 'non-premium' brass. It makes enough of a difference for me to feel the time is well spent.
And, just to remind myself why I do so, I keep the cases from the extreme ends of the spectrum to occasionally test against the carefully sorted 20/50-piece groups. The 'extreme weights' loads nearly always look like two distinct groups with a few flyers, whereas the sorted brass only deviates if some other variable is screwed up (like neck tension or powder charge).


With once-fired brass, mixed brass, or other brass of unknown origin, sorting by more than headstamp (and maybe capacity) isn't terribly useful for me. If I'm going to the trouble of sorting, then I want to do so with a good foundation -- new brass. For rifle cartridges, the only once-fired brass that I still use is .30-30. I still sort by head stamp and general condition; but I have not (yet*) owned a .30-30 worthy of 'high grade' ammunition.
*(There's one in work that has been shooting "bug holes" in early testing, but the rifles is not yet finished and does not have the final crown. So, fingers crossed...)



This is a snapshot of a portion of the data from some .270 or .30-06 brass that I sorted a while back (don't remember which brand). I sort after deburring flash holes, and trimming all cases to a uniform length, to eliminate variations caused by 'hanging chads' (incompletely punched flash holes) and the cases being trimmed on different machines.

Note the multiple peaks. There were likely at least three different drawing presses involved here. Though the difference between peaks illustrated in the graph isn't huge, when you add the rest of the data (spanning another 4 grains and containing 5 more peaks), it paints a picture of mass-produced brass that will be adequate for most people ... but it's nowhere near the consistency of Lapua. (I once weighed 200 pieces of Lapua .30-06 brass and found the entire lot to be within 0.1 gr!)

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And FrankenMauser I definitely agree, I don't have the app like yours but I believe my tools, and your right across the board.
The differences in brass is there, but what I did was to come to terms with what my end result was gonna be to satisfy my quest, and I found that since I have one 3006, and over 600 cases, (some in testing, some only oncefired), and this rifles purpose is to hunt, then weighing those cases was first off my list.
Now I still debur flash holes, and trim of course, but I'm tickled with this rifle shooting sub moa with what I'm feeding it.
The Op may want to glide deeper into more consistant cartridges, but it's a long hard pull for the rifle he's starting with...
 
What brand chronograph is it?

If it is a low-cost chrono (I.e. not an Oehler) you might want to try to check the chronograph. Easiest would be if you could borrow a magnetospeed or LabRadar and do a combined check shooting through your chrono while also using the magnetospeed or LabRadar. That would tell you if your chrono is providing correct readings, could be it's off.
 
You're loading 53.5 gr of H4831 and getting 30/30 velocities.
Hodgdon shows a max load of 60 grains. That's a compressed load that doesn't hit max pressure, so it looks like you can't fit enough H4831 in a 30-06 case with a 180 gr bullet to cause pressure problems.
You can probably find a good load somewhere around 58 to 60 grains.
 
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