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Headspace Head Scratcher

Jeffersonian

Help me figure out this head scratcher. I have a Winchester XPR in .30-06 for which I reload. It’s an accurate gun for a sporter. The only factory load I have shot is Winchester Deer Season XP which prints neat .75 moa groups.

Using neck sized or unfired brass I have not had the reloading success for which I hoped.
I have gotten approx 1-1.5 moa results with multiple bullet types and powders, kinda disappointing considering how it will shoot Winchester factory ammo.

Here is where it gets interesting. I have some ammo that I loaded up for my Garand with the 168gr SMK and I decided to try it in the Winchester. It uses IMR 4895 and brass that has already been fired from the M1 and resized just until it passes the head space gauge. Loaded to mag length about 3.35”.

The bolt closes somewhat hard with this ammo, it was however superbly accurate. Bug hole group, probably .3-.4 shot again a different day to confirm it is not a fluke.

I excitedly loaded up some neck sized brass with the same powder load and bullets to the same oal. Took to the range and got mediocre results.

I then decided to try some more m1 garand fired brass with that load, well lo and behold another bughole group.

The only difference that I could tell is the headspace measurement of the brass. Why might this be? In my mind it doesn’t make sense. The brass fire formed to my chamber by conventional wisdom SHOULD give better accuracy, shouldn’t it?
 
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Are you able to measure the velocity of those two loads? My initial guess would be the velocity is enough different that it works well with one load and not with the other. The reason this could happen is if one of the cases has to be 'blown out' to fit the chamber the velocity will be lower since some of the energy is being used to fire form.
 
Another option is that the chamber or neck only die is off somehow and the neck sized brass is not loading centered to the bore.

Check concentricity of a fired case and same case loaded after neck sizing.
You can try indexing the fired cases so they are chambered the same each time. Or simply try full length sizing.
 
Jeffersonian said:
Help me figure out this head scratcher. I have a Winchester XPR in .30-06 for which I reload. It’s an accurate gun for a sporter. The only factory load I have shot is Winchester Deer Season XP which prints neat .75 moa groups.

Using neck sized or unfired brass I have not had the reloading success for which I hoped.
I have gotten approx 1-1.5 moa results with multiple bullet types and powders, kinda disappointing considering how it will shoot Winchester factory ammo.

Here is where it gets interesting. I have some ammo that I loaded up for my Garand with the 168gr SMK. It uses IMR 4895 and brass that has already been fired from the M1 and resized just until it passes the head space gauge. Loaded to mag length about 3.35”.

The bolt closes somewhat hard with this ammo, it was however superbly accurate. Bug hole group, probably .3-.4 shot again a different day to confirm it is not a fluke.

I excitedly loaded up some neck sized brass with the same powder load and bullets to the same oal. Took to the range and got mediocre results.

I then decided to try some more m1 garand fired brass with that load, well lo and behold another bughole group.

The only difference that I could tell is the headspace measurement of the brass. Why might this be? In my mind it doesn’t make sense. The brass fire formed to my chamber by conventional wisdom SHOULD give better accuracy, shouldn’t it?
Click to expand...
Case capacity will come into play when the brass is F/L sized more than just enough to cause easy chambering.
 
Why you would only neck size cases for hunting escapes me. Some thing no one mentioned, why did the bolt close hard. Could be several reasons but the first that comes to my mind is seating depth. Is the bullet in the accurate ammo engaging the lands and the others jumping perhaps. Easy to ck. Polish the accurate round bullet with steel wool, load it, unload it, did the lands leave a mark. If so, problem solved.
 
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Stop neck sizing. Bad idea for a hunting rifle, not a good idea either for target rifle. Do not mix cases between rifle - dedicate a group of cases to a specific rifle and rotate their use. Reliable function is a key requirement for a hunting rifle. F/L sizing aids in assuring that.

You don't need bug holes for deer hunting, 1 to 1 /2 moa is good enough. However, I understand your desire to shoot better groups, I would have the same feeling. So, I'll offer some suggestions:

Using a bump gauge and caliber set you F/L die to zero shoulder set back. Check in rifle chamber for any chambering difficulty. If none, size the rest of the lot. If not, push back the shoulder .001 to .002.

It's been a long time since I shot the grand old 06. IMR 4895 should work in the 30 06 but with that weight bullet, I got better result with IMR 4350.
 
It seems to me that there are a couple of measurements of the cases that have been overlooked, the diameters at the shoulder and the diameter at the .200 line. You are only looking at cases in terms of one dimension. In my experience fit of the case body in the chamber is a relevant factor. The assumption that tighter is better often gets in the way of people understanding their results or finding the best loads.
 
My first question is why are you neck sizing?….
Second thought would be the m1 ammo most likely has a roll crimp which would tell me your Winchester likes more neck tension, this is backed up by the fact you say factory ammo shoots well which definitely has a lot of neck tension,… just my initial thoughts .
Wayne
 
Run a test, 10 fired brass sized to the new Win ammo brass dimensions, with twice the neck interference you have been loading on 5. See which 5 group similar to the factory ammo, that should give you a direction to test further. You may need Win primers to fine tune, but than again it is a deer rifle.
 
For a bolt action 30-06' rifle and 175 to 220 gr bullets I would use H-4831sc (should work with 165 gr bullets but Max load will be compressed). It has never failed me to deliver top accuracy in all cartridges I load it in.
Usually (not always) H-4831sc is most accurate not near the MAX load but more in the 3/4 range of the load data. So velocity "might" not be super fast.

With a 165 gr BTSP bullet, the MAX load of H-4831sc will probably be around 62 gr. But I would load from 58 to 61 gr. in 0.5 gr increments. If that doesn't shoot I'd be very surprised. 3.250" Coal is probably a good length to start as well.
 
Are we sure it's a headspace problem?

We know what the OP said shoots well (IMR4895 & 168 MK), but there is no load data for the stuff that doesn't shoot well. Not even bullet weight.

Maybe a similar IMR4895 load with some similar 165-168gr hunting bullets with a similar BTO measurement might solve the problem? Kinda hard to diagnose from here with the information given.
 
Tks Boyd, I should have added the reason, just thought it was common knowledge

"and resized just until it passes the head space gauge. Loaded to mag length about 3.35”

Last thing I would want in a M1 is ammo that loads hard! Just because it fits a case guage does not mean it will fit your M1! Find out why it fits/closes hard and correct it. Most likely one of two thing: either the shoulder needs another thou or two of bump or the bullet is seated too long and is hitting the rifling. High primers will do it also. Have you ever seen a M1 fire out of battery?

Frank
 
fkimble@charter.net said:
Tks Boyd, I should have added the reason, just thought it was common knowledge

"and resized just until it passes the head space gauge. Loaded to mag length about 3.35”

Last thing I would want in a M1 is ammo that loads hard! Just because it fits a case guage does not mean it will fit your M1! Find out why it fits/closes hard and correct it. Most likely one of two thing: either the shoulder needs another thou or two of bump or the bullet is seated too long and is hitting the rifling. High primers will do it also. Have you ever seen a M1 fire out of battery?

Frank
Click to expand...
These are good things to know about a m1 but a little off topic from the op’s question
Wayne
 
fkimble@charter.net said:
Tks Boyd, I should have added the reason, just thought it was common knowledge

"and resized just until it passes the head space gauge. Loaded to mag length about 3.35”

Last thing I would want in a M1 is ammo that loads hard! Just because it fits a case guage does not mean it will fit your M1! Find out why it fits/closes hard and correct it. Most likely one of two thing: either the shoulder needs another thou or two of bump or the bullet is seated too long and is hitting the rifling. High primers will do it also. Have you ever seen a M1 fire out of battery?

Frank
Click to expand...
The ammo in question is made for the M1, and loads in the Garand just fine.

It is however *slightly* tight in the Winchester XPR. It is not the primers which are flush, or the bullet seating depth being too long, as the casing without the bullet is just as tight.
 
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358WCF said:
Are we sure it's a headspace problem?

We know what the OP said shoots well (IMR4895 & 168 MK), but there is no load data for the stuff that doesn't shoot well. Not even bullet weight.

Maybe a similar IMR4895 load with some similar 165-168gr hunting bullets with a similar BTO measurement might solve the problem? Kinda hard to diagnose from here with the information given.
Click to expand...

It’s not really a problem at this point, I’m just trying to figure out WHY this combo which is counter-intuitive seems to be my “magic pill”
 
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