How does neck lube effect the neck tension?

[AussieShooter]

I have used the Redding carbide buttons with the Redding competion dies when I reload.

I have the powder measured down to 0.002 of a grain, case OAL aswell as COAL seating consistency of 0.002".

I am getting a velocity despertion of around 110 fps (2710 min & 2818 max).

I am using Lapua brass and 175 SMK's. I have no reason to doubt the powder.

Would implementing neck lube do anything to tighten up the velocity variation (help towards a consistent neck tension) or is it used solely to minimise the runout by minimising the force exerted on the case by the projectile when seating?

 

[agbm]

Are you annealing your brass?

 

[AussieShooter]

The brass is new and all of the same lot.

I was going to anneal after I have shot all of the first lot.

 

[djskit]

How are you cleaning off the lube you use to resize? Some lube in some of the necks might explain your trouble. I use spray lube and tumble all in untreated corn cob for an hour or so to make sure every bit is try - then I brush the inside of the necks to get rid of any residue.


Or maybe your chronograph is faulty, or one of the sensors had sun shinning on it and the other one didn't. First hand experience with that one.

 

[chefcam864]

Dude, if you're weighing charges down to 2 thousandths of a grain and getting an ES of 110 fps, nothing is going to help... As mentioned above, your chrono may be giving false readings (not uncommon). if you have access to a 300 yard range you could just shoot the rounds. A 110 fps ES will be easy to spot at 300, and impossible to deal with at 1k. If it's not the chrono, your components are just not compatible. Start looking for another powder/bullet/primer combo. I doubt very seriously if using neck lube will get you from 110 to <15...

I'm just curious, but what kind of balance are you using to weigh to .002gn?

 

[AussieShooter]

I haven't been using any neck lube. I have just used the titanium nitride collets as they are supposed to remove the need for neck lube. I was considering purchasing some imperial neck powder and giving it a go.

The Chrony is a PVM-21 so I hope it's not the Chrony. As for weather effecting the velocity reading the PVM-21 uses IR rather than sunlight so any change in lighting shouldn't effect the readings. I used to use the "Chrony" make and I know where you are coming from about the sun light.

The powder temperature was all the same and barrel was cool prior to each shot.

I'll shoot some targets at 300 and see the spread but I didn't know if not implementing the neck lube would effect the neck tension.

I use a Sartorius Precesion Balance for my powder measuring. I measure each charge manually which is time consuming but it would be worth it if I can find the reason behind the varying velocities.

If nobody has experienced the same issue I think I'm going to have to shoot the remaining 150 odd rounds (some at 300) and review the POI, then anneal and reload using neck lube and see if the lube makes a difference in neck tension consistency.

 

[jim_k]

When you seat your bullets, take note of the neck tension, and only test those that have similar neck tension, preferably the ones that have the least neck tension.
Jim

 

[chefcam864]

I doubt you have an instrumentation problem With a pvm21 and a sartorius that weighs to .002gn. I weigh my charges to .05gn on a cheap GemPro, and easily get SD's<10, and <5 with a good load. I shot a 1k match this weekend, and held 10-ring elevation. I use a Magnetospeed V1 to chrono. The only thing I can think of that usually helps is filling the case up with powder. In my experience, the denser the fill, the tighter the spread. I really do not think annealing or neck lube are going to solve your problem. However, neither of those things will hurt, so it's worth a try.
What is your load? That may be useful information for solving the problem. I've noticed problems like this with fast powders and heavy bullets. Specifically, H-Benchmark and 175's in a .308 Win.

 

[EXTREMEPREJUDICE]

The brass is new and all of the same lot.

It's your dime, but before I would start chasing the 100 FPS variance looking at detail such as neck lube I would fire-form first..............

 

[Blackbrush]

What cartridge? What powder? What primer?

 

[AussieShooter]

I think you might have something regarding the velocities pre-fireforming.

I thought the powder might have gone off but I used the same powder on fireformed cases and the ES was within 10fps.

I'll load some of the fireformed cases with the the same powder again with the same measurements and shoot both loads to see if the Chrony is working right.

Has anyone else seen similar fps spread prior to fireforming?

I use Lapua brass loaded to the suggested max of 45gr with CCI primers using ADI AR2208 (equivalent to Hogdan Varget) and 175 SMK's and seated depth approx 75% of the neck length.

 

[Blackbrush]

I'm assuming 308 Win. I run the same load basically but with Federal Match primers. My SD is single digit. What is your neck tension? There should be no lube in the neck.

 

[AussieShooter]

Yeah, sorry 308.

The prodgy (AKA projectile) is 0.308" + 0.015" (neck wall thickness) x 2 - 0.002" (neck tension of 0.001") = 0.336" collet (external neck diameter of 308 reload using previously stated components).

I just bought some Redding dry lube and applicator for the next time I reload to minimise over working the neck at a bare minimum.

I am still keen to hear any other experiences regarding the comparison between the variation in velocity between pre-fireformation and post-fireformation.

From a theoretical perspective if the components and measurements are the same of the pre-fireformed case then the velocity of those cases should be similar amongst that groups sample.

 

[Blackbrush]

I use prodigious amounts of Imperial sizing lube but clean cases thoroughly before loading.

 

[TwistedNerve]

It's your dime, but before I would start chasing the 100 FPS variance looking at detail such as neck lube I would fire-form first..............

I'd second this. Also, I assume you neck sized the factory new brass?

 

[chefcam864]

I can only speak from my experience, BUT I have never seen anything like a 110 fps es with new brass only to have that es shrink to 15 after fireforming. 95% of my experience is with the cartridge in question, .308 Win. I'm not saying it couldn't happen, but it seems thin...

 

[XTR]

If you were shooting new Lapua brass your neck tension as all over the place. New Lapua has at least 6 thou and and it can vary a whole lot from case to case and running it through a die doesn't change that.

Either get an expander mandrel for your new brass or run an expander button through it. You have to open that stuff up to get it to shoot.