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Neck tension variation on target

Tod Hendricks

Gold $$ Contributor
While testing light or less neck tension I had 5 cases that ended up with no tension or grip on the bullets. So light if I turned them upside down the bullet and powder would fall out. I kept those 5 separated for foulers.

When I loaded them in the gun I eyeballed the OAL so it was close to the length of the rest of the box, but they varied widely. I also closed the bolt very slow.

Ive never done a controlled test with zero neck tension, so I was a bit surprised how they grouped, so much so I decided to shoot a few more into the group with the test rounds with 5-10 psi seating pressure. The difference on target velocity and elevation is very significant, way more than I would have ever expected.

The loads are identical other than neck tension and OAL, they were all jumped over .020”, the no tension loads were probably .020” to .050” jump. I’m visualizing the light tension bullets moved to a touch/jam point very rapidly in the firing sequence. Aim point is the same on all shots.

Anyways it produced a very interesting target to ponder.
 

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While testing light or less neck tension I had 5 cases that ended up with no tension or grip on the bullets. So light if I turned them upside down the bullet and powder would fall out. I kept those 5 separated for foulers.

When I loaded them in the gun I eyeballed the OAL so it was close to the length of the rest of the box, but they varied widely. I also closed the bolt very slow.

Ive never done a controlled test with zero neck tension, so I was a bit surprised how they grouped, so much so I decided to shoot a few more into the group with the test rounds with 5-10 psi seating pressure. The difference on target velocity and elevation is very significant, way more than I would have ever expected.

The loads are identical other than neck tension and OAL, they were all jumped over .020”, the no tension loads were probably .020” to .050” jump. I’m visualizing the light tension bullets moved to a touch/jam point very rapidly in the firing sequence. Aim point is the same on all shots.

Anyways it produced a very interesting target to ponder.
Did you single load each cartridge into the chamber? The low tension cartridges are going to be highly affected by the speed you operate your bolt closure. When you say you "eyeballed OAL", did you measure cartridge base to bullet tip or cartridge base to ogive, CBTO. I think the modern thinking is more neck tension vs. less or no tension this prevents upset of the bullet in the neck for better concentricity.
 
@Tod Hendricks years ago I was getting a load worked up for the BCRA Provincial @ Chilliwack BC. I had a new (at the time) Sav 12 FTR in 223 Rem, and the equally new B82BT. Somehow, in the course of load development I forgot to size the necks of five cases (I was doing it as a separate step with a LCD back then). When I went to sit the bullets in the mouth of the charged and primed cases, it just went 'thunk' and sat on top of the powder column. Whoops!

I didn't want to dump the powder and decaps the rounds just to size the necks, re-prime and hand trickle five more charges (like I said, it was a while ago ;)) so I figured I'd just use those rounds for foulers/sighters. Had to be *veeeery* gentle loading them into the chamber. Thank goodness I didn't have to extract one, because the case was rather full - the bullets were a good 30 thou into the lands.

At the end of the range session, I had to pivot and change direction a bit. Those five rounds went into a nickel sized group - at 300 yards, off a bipod no less. By far the smallest group of all my seating depth testing. And wonder of wonders, it repeated - several times.

In the end, I had to use *some* neck tension to have a functional load to take on the road... but it was far less, and with the bullet at lot further into the lands, than I would have normally ever tried. Even did pretty well in the Provincials, too ;)
 
I was going to ask the crony question as well Tod. That target velocity is getting to be a whole node slower, so I wonder if the lower node would be worth looking into also. I've never seen tension tests move the speed, or poi very much like this.....BUT I've never tried "0 holds" before lol.

Tom
 
I did this on accident once. I neck turned some new brass forgot to change my bushing it shot great. I was having a conversation with someone about bushings so I was reading my notes and did the math annd it said I had zero neck tension and kept thinking what did I do wrong. So I went and grabbed a loaded round and pushed the bullet in with my finger. nope I did the right math definitely had no neck tension. I couldn’t help but laugh out loud at my self. I couldn’t believe I didn’t notice.
 
While testing light or less neck tension I had 5 cases that ended up with no tension or grip on the bullets. So light if I turned them upside down the bullet and powder would fall out. I kept those 5 separated for foulers.

When I loaded them in the gun I eyeballed the OAL so it was close to the length of the rest of the box, but they varied widely. I also closed the bolt very slow.

Ive never done a controlled test with zero neck tension, so I was a bit surprised how they grouped, so much so I decided to shoot a few more into the group with the test rounds with 5-10 psi seating pressure. The difference on target velocity and elevation is very significant, way more than I would have ever expected.

The loads are identical other than neck tension and OAL, they were all jumped over .020”, the no tension loads were probably .020” to .050” jump. I’m visualizing the light tension bullets moved to a touch/jam point very rapidly in the firing sequence. Aim point is the same on all shots.

Anyways it produced a very interesting target to ponder.
So is that a 1000 yards or six 600
 
To what degree do discerning shooters trust the velocity readings offered by ShotMarker?

Do the ES/SD numbers tend to be similar? Shotmarker vs. muzzle...
 
To what degree do discerning shooters trust the velocity readings offered by ShotMarker?

Do the ES/SD numbers tend to be similar? Shotmarker vs. muzzle...
That tends to be a "it depends" answer.

On very windy days, you tend to get more noise in the SM velocity numbers.
On good days, the numbers narrow down and tend to match up well with expectations from ballistics estimates.

So, the general answer is to take them with a grain of salt. They don't cost you anything and I am happy to have them in the data. When they go wonky, usually there is also something wonky with the ammo , but not always.
 
@Tod Hendricks years ago I was getting a load worked up for the BCRA Provincial @ Chilliwack BC. I had a new (at the time) Sav 12 FTR in 223 Rem, and the equally new B82BT. Somehow, in the course of load development I forgot to size the necks of five cases (I was doing it as a separate step with a LCD back then). When I went to sit the bullets in the mouth of the charged and primed cases, it just went 'thunk' and sat on top of the powder column. Whoops!

I didn't want to dump the powder and decaps the rounds just to size the necks, re-prime and hand trickle five more charges (like I said, it was a while ago ;)) so I figured I'd just use those rounds for foulers/sighters. Had to be *veeeery* gentle loading them into the chamber. Thank goodness I didn't have to extract one, because the case was rather full - the bullets were a good 30 thou into the lands.

At the end of the range session, I had to pivot and change direction a bit. Those five rounds went into a nickel sized group - at 300 yards, off a bipod no less. By far the smallest group of all my seating depth testing. And wonder of wonders, it repeated - several times.

In the end, I had to use *some* neck tension to have a functional load to take on the road... but it was far less, and with the bullet at lot further into the lands, than I would have normally ever tried. Even did pretty well in the Provincials, too ;)
LOL, what you did is what we call a benchrest jamb. Often we will expirament with a 20+ jam but using a .0005 or .001 neck tension. In actuality the bullet really isn't jamed into the lands 20 grand since it slides back into the case neck. For some unknown reason from time to time this will yield greater accuracy compare to a "0" or "+" seating.
 
LOL, what you did is what we call a benchrest jamb. Often we will expirament with a 20+ jam but using a .0005 or .001 neck tension. In actuality the bullet really isn't jamed into the lands 20 grand since it slides back into the case neck. For some unknown reason from time to time this will yield greater accuracy compare to a "0" or "+" seating.

In that particular situation... I don't think it got shoved very far back into the neck, given that the case was rather... full. That +30 jam was with the bullet sitting on the powder column. Just sayin'.
 

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