Neck Tension Question RE: Soot on Necks

[LawnMM]

Here are some pics of some cases I fired today, seems to be a good bit of soot on the necks. I had gone to .001 for neck tension as an experiment, didn't seem to affect accuracy, but my velocities with this load were low...around 2607fps.

This is a random sample of 10 cases from a group of 50 I shot today.

I went back to .002 neck tension and velocity climbed up to 2655-2660fps. I'm using Hornady 178 HPBTs, Winchester Brass 3x, CCI BR2s, and 43.8gr of Varget. Its shooting around half moa at 100 when I do a good job with my fundamentals.

My question to you all is, how much of a sooty neck is normal? Does this appear to be average, above average, excessive? It seems a bit sooty to me, and this was shot through a freshly cleaned barrel and chamber the night before. I'm wondering if .003 of neck tension might yield higher velocities and a more complete powder burn.

Rich

 

[oneshotkyle]

Re: Neck Tension Question RE: Soot on Necks

how far of a jump to the lands.

 

[LawnMM]

Re: Neck Tension Question RE: Soot on Necks

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: oneshotkyle</div><div class="ubbcode-body">how far of a jump to the lands. </div></div>

.008"

I get 2.240" to the lands with a chamber length gauge, ammo is loaded to 2.232". I shoot for 2.230" sometimes they wind up a little longer if I go a little easier on the ram.

 

[oneshotkyle]

Re: Neck Tension Question RE: Soot on Necks

one of my 22-250's that i have .003 of lands loaded with varget is just as dirty around the case and it shoots 1/2moa all day long. i wouldn't worry about the soot. just keep on shooting...

 

[LawnMM]

Re: Neck Tension Question RE: Soot on Necks

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: oneshotkyle</div><div class="ubbcode-body">one of my 22-250's that i have .003 of lands loaded with varget is just as dirty around the case and it shoots 1/2moa all day long. i wouldn't worry about the soot. just keep on shooting... </div></div>

Not worried about it as much as curious if more neck tension might yield a more complete burn and more velocity without jacking my pressure up much in turn. I may try another .001 of tension and see what happens.

Rich

 

[crewchef]

Re: Neck Tension Question RE: Soot on Necks

Something someone much better at this than I told me; "Look for load where carbon (soot) is about 3/4 down the neck and work from there." I'm sure neck tension can (does) come into play but my thought is adjusting the load is what you need to look at. Assuming you're not seeing pressure signs of course. My guess is that you're in a lower "node" and if you bump up load you'll find another accurate one somewhere around 45.0.

All that said, probably wouldn't worry with it unless you're trying to shoot 600+. Only thing that counts is holes in the paper and if it's shooting good wouldn't worry about carbon on the necks.

 

[oneshotkyle]

Re: Neck Tension Question RE: Soot on Necks

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LawnMM</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: oneshotkyle</div><div class="ubbcode-body">one of my 22-250's that i have .003 of lands loaded with varget is just as dirty around the case and it shoots 1/2moa all day long. i wouldn't worry about the soot. just keep on shooting... </div></div>

Not worried about it as much as curious if more neck tension might yield a more complete burn and more velocity without jacking my pressure up much in turn. I may try another .001 of tension and see what happens.

Rich </div></div>


oh ya im at .003 neck tension on mine. always did .002-.003 neck tension and never tried any more or less. id be curious to hear what others have to say about this.

 

[LawnMM]

Re: Neck Tension Question RE: Soot on Necks

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Crewchef</div><div class="ubbcode-body">Something someone much better at this than I told me; "Look for load where carbon (soot) is about 3/4 down the neck and work from there." I'm sure neck tension can (does) come into play but my thought is adjusting the load is what you need to look at. Assuming you're not seeing pressure signs of course. My guess is that you're in a lower "node" and if you bump up load you'll find another accurate one somewhere around 45.0.

All that said, probably wouldn't worry with it unless you're trying to shoot 600+. Only thing that counts is holes in the paper and if it's shooting good wouldn't worry about carbon on the necks. </div></div>

Correct, no pressure signs. However, I'm hesitant to adjust a powder charge on a load that's shooting in the .5s and carrying 2650fps at 15ft from the muzzle. At some point you reach the limit of diminishing return on raw speed. Do I really need another 50-100fps? Not really, if its at the cost of an even pressure load.

So as I type this reply I'm coming to the realization that I'm looking for ways to fix something that isn't broken. I have the speed I want with good chrono numbers and it matches my FDAC slide, verified at 600/800yds. So maybe I'll just let it be. Still interested in people's thoughts on the idea of neck tension affecting pressure buildup and how that affects powder burn efficiency in the case.

Reloading tends to bring these little questions to the front of my mind and my natural inclination is to start down the path of testing and eliminating variables. Sometimes I get so into the reloading hobby I forget I really just got into it to make my main hobby, shooting, more economical.

Rich

 

[TexIndian]

Re: Neck Tension Question RE: Soot on Necks

It is curious that reducing your neck tension reduced your MV. I know loads need a certain amount of resistance to get an efficient burn, but that extra bit of neck tension is really a tiny, tiny bit of additional resistance. I wonder what else might be at play? Like you, I start getting little questions in my head.

 

[targaflorio]

Re: Neck Tension Question RE: Soot on Necks

What leads you to believe there is a relationship between residue on the necks and neck tension or powder burn completeness?

 

[Greg Langelius *]

Re: Neck Tension Question RE: Soot on Necks

To answer the original question, the amount of neck soot shown does not appear anywhere near excessive. I would be more concerned if the soot was appearing on the shoulder portion of the case than with what's happening to the necks.

Soot is an indication of how well the case neck is expanding and sealing to the chamber/neck wall.

Personally, I believe it's telling me more about work hardening of the brass necks than about other things that may be happening. I don't see neck tension as a cause of sooting, but rather, the sooting tells me whether brass hardening is increasing neck tension on its own. If my surmise is correct, the more firings the cases experience, the greater the sooting.

I don't anneal, so sooting, combined with primer seating resistance, is how I determine whether my brass is ready for replacement.

Greg

 

[doc76251]

Re: Neck Tension Question RE: Soot on Necks

Everything that Greg just said!

Cheers,

Doc

 

[LawnMM]

Re: Neck Tension Question RE: Soot on Necks

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">To answer the original question, the amount of neck soot shown does not appear anywhere near excessive. I would be more concerned if the soot was appearing on the shoulder portion of the case than with what's happening to the necks.

Soot is an indication of how well the case neck is expanding and sealing to the chamber/neck wall.

Personally, I believe it's telling me more about work hardening of the brass necks than about other things that may be happening. I don't see neck tension as a cause of sooting, but rather, the sooting tells me whether brass hardening is increasing neck tension on its own. If my surmise is correct, the more firings the cases experience, the greater the sooting.

I don't anneal, so sooting, combined with primer seating resistance, is how I determine whether my brass is ready for replacement.

Greg </div></div>

Interesting point of view. I will watch for that. The brass pictured is after its 4th firing. I am not an annealer either so your point is intriguing as far as judging what life the brass has left. My bigger concern than the necks was head separation. A properly set die seems to have reduced most of that. I may sort through my brass after its all been 4x fired. Any showing prominent signs of head separation from over sizing prior to getting better dies will likely be discarded.

I may send the rest to one of the guys on the hide here that does steel media cleaning and annealing by mail.

Rich

 

[PeterN]

Re: Neck Tension Question RE: Soot on Necks

I have done a few neck tension trials and have never seen a velocity change between plus or minus .001 in sized neck diameter. Id look for other possible reasons for the velocity change. Temperature?Chronograph distance from muzzle? Sun angle? Cloud cover? Sometimes my crono just decides to misbehave

 

[Fuzzball]

Re: Neck Tension Question RE: Soot on Necks

I believe modest amounts of neck/body sooting occurs because of the total timeressure curve more than anything else.

A slower pressure rise will allow a tiny bit more gas to leak back around the neck before the neck seals. AND, a retained pressure that's insufficent to maintain that neck seal until the bullet exits will also allow gas to blow back outside the case. I think.

Try increasing your OAL maybe 3-4 thou and see if that doesn't increase pressure enough to get your velocity back without damaging your accuracy.

 

[LawnMM]

Re: Neck Tension Question RE: Soot on Necks

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: PeterN</div><div class="ubbcode-body">I have done a few neck tension trials and have never seen a velocity change between plus or minus .001 in sized neck diameter. Id look for other possible reasons for the velocity change. Temperature?Chronograph distance from muzzle? Sun angle? Cloud cover? Sometimes my crono just decides to misbehave </div></div>

I always place the chronological at the same distance confirmed by tape measure. No appreciable temp change, 10-15 degrees tops. That might account for a 10ish fps change but not 55.

 

[LawnMM]

Re: Neck Tension Question RE: Soot on Necks

As a late update, I went back to. 002 for the neck tension and velocity went back up. More pressure in the case before the projo starts its trip I suspect.

The sooting? Its a little grime from the bushing in the neck die attracting unburned powder. Even cleaning the bushing it comes back pretty quick, I've learned to live with it.

 

[ChrisGarrett]

Re: Neck Tension Question RE: Soot on Necks

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LawnMM</div><div class="ubbcode-body">As a late update, I went back to. 002 for the neck tension and velocity went back up. More pressure in the case before the projo starts its trip I suspect.

The sooting? Its a little grime from the bushing in the neck die attracting unburned powder. Even cleaning the bushing it comes back pretty quick, I've learned to live with it. </div></div>

How short are you trimming your cases? Sometimes you can let the necks grow a bit longer and they'll seal off in the chamber, better.

Chris