Neck tension vs velocity

X

xingyc

Regular
Rating - 100%
16   0   0
Location
GTA, Ontario
Currently, I'm using Hornady brass. The brass are on 4th reload. as I seat the bullets, I felt the neck tension was inconsistent and weaker than previous reloads.
All the bullet, powder and primer are from the same lot number as previous reloads. Used the same reloading equipment and procedures.

I shot the reload yesterday, my zero at 130 yard has shifted up by 0.75moa, and my elevation adjustment at 550 yard and 800 are 1-2moa less than my DOPE. I didn't have my magnetospeed with me, so I cannot confirm the velocity.

Is neck tension my root cause? anyone with similar experience?

I'm considering to switch to Starline brass and incorporate annealing into my reloading procedures.
Should I start with the same powder weight and adjust powder weight to match current velocity.
 
Last edited:
Cut your Hornady brass in half, if no signs of case head separation its good to go. I am on number 8 or 9 with my Hornady brass, its still good, no thinning, but I have culled a few for loose primer pockets. I anneal after every firing. Still shoots as good as ever.
I am confused about the eagle eye dude, he seems to kinda go all over the place in his reloading process. I just think he shoots so much he eventually sorts it all out lol.
 
Lead hammer said:
Cut your Hornady brass in half, if no signs of case head separation its good to go. I am on number 8 or 9 with my Hornady brass, its still good, no thinning, but I have culled a few for loose primer pockets. I anneal after every firing. Still shoots as good as ever.
I am confused about the eagle eye dude, he seems to kinda go all over the place in his reloading process. I just think he shoots so much he eventually sorts it all out lol.
Click to expand...

My theory is, every time the neck grows, the case volume must decrease by minute amount, but after 5 or 8 firing, it might change the muzzle velocity. And trim brass after each firing is extra work.
Most importantly, Starline is cheaper. And someone achieved great precision with them on video.
 
xingyc said:
I get excessive neck growth with Hornady brass. Close to 6-8 tho per firing.
Starline is cheaper and youtuber [eagle eye shooting] uses Starline brass, he gets exceptional precision with Starline.
Click to expand...

The only time I got that much neck growth with Hornady brass was full length sizing and loads at the very top of the loading table. Does Lapua sell brass in that caliber?
 
I found a slight velocity increase as the inside of my cases got progressively dirtier with each firing. Ultrasonic cleaning eliminated that variable. It wasn't much, maybe 15 fps on average over 6 firings.

As your case necks harden with repeated firings and working the brass, your seating effort should increase, up to a point at which it will level off. The case doesn't get any harder after it reaches that point.

I anneal every 4th firing, the freshly annealed cases require noticeably less effort to seat bullets than the ones that aren't.

I don't find any significant velocity change between freshly annealed cases and those that aren't. Certainly not enough for up to 2 moa difference.

A velocity increase at this time of year is often a result of the ambient temperature affecting powder performance. Many powders aren't "temperature stable", meaning velocity increases as the temperature goes up, and drops when the weather cools down again.

Keeping loaded ammo out of the sun helps a bit, brass gets quite hot in direct sunlight.

What powder are you using, and in what cartridge/calibre?
 
xingyc said:
My theory is, every time the neck grows, the case volume must decrease by minute amount, but after 5 or 8 firing, it might change the muzzle velocity. And trim brass after each firing is extra work.
Most importantly, Starline is cheaper. And someone achieved great precision with them on video.
Click to expand...

If your worried about that small case volume change, you are probably not set up around the middle of a node. I trim every time. I mean if the case neck length and softness of the brass case to case is different, you have a problem.
Hardened brass will springback more and also reduce neck tension when loading.

I have Starline 357 brass. It’s been fine. Some new in package had oxidized spots in them and is still there. Never had a Hornady do that.
I would like to run Alpha brass but it’s not in the budget and I would probably need to neck turn. ( would like to do this anyway )
 
Chilly807 said:
I found a slight velocity increase as the inside of my cases got progressively dirtier with each firing. Ultrasonic cleaning eliminated that variable. It wasn't much, maybe 15 fps on average over 6 firings.

As your case necks harden with repeated firings and working the brass, your seating effort should increase, up to a point at which it will level off. The case doesn't get any harder after it reaches that point.

I anneal every 4th firing, the freshly annealed cases require noticeably less effort to seat bullets than the ones that aren't.

I don't find any significant velocity change between freshly annealed cases and those that aren't. Certainly not enough for up to 2 moa difference.

A velocity increase at this time of year is often a result of the ambient temperature affecting powder performance. Many powders aren't "temperature stable", meaning velocity increases as the temperature goes up, and drops when the weather cools down again.

Keeping loaded ammo out of the sun helps a bit, brass gets quite hot in direct sunlight.

What powder are you using, and in what cartridge/calibre?
Click to expand...

The DOPE I referred to is the same temperature. All ammo and rifle were kept in the shade.
The powder is H4831SC, cartridge is 270win.

I just remembered, the brass was sized 4-5 days before I seat the bullets. This was the only inconsistency in my reloading procedure. Maybe the neck sprang back during that time. Next time I'm going to test the neck diameter vs time.
Does old ammunition lose neck tension as time increase?
 
You must log in or register to reply here.
Back
Top Bottom