Gunsmithing Case blackening at the neck

[sobrbiker883]

Re: Case blackening at the neck

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: V-hunter</div><div class="ubbcode-body"> it does not happen on the first firing of new brass which is full length sized using a standard 308 full length sizing die <span style="font-weight: bold">then expanded on an expander mandrel, neck turned and sized back down with a redding 335 type S neck bushing die</span>. On every other firing the powder residue travels down 3/4 of the shoulder of the fired cases. Accuracy is not an issue the gun is shooting very well. I did not have this issue on the original factory barrel, by the way the rifle is a Savage model 12 F/TR.

Annealing the brass did rectify the problem but this is a timely process and I would prefer to prevent this from happening rather than having to deal with the problem of annealing all my new once fired brass..

V-hunter </div></div>

Why would you expand, then turn, then size again a neck?

And yet annealing is time consuming......

 

[Hateca]

Re: Case blackening at the neck

Stop turning the necks. Size new brass without turning the necks and go shoot it. If the chamber was cut with a no-turn-neck reamer you're wasting your time turning the necks and this is one thing that could be leading to your "problem".

 

[Lucks]

Re: Case blackening at the neck

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308saiga</div><div class="ubbcode-body">When he resizes what is the length of the casing? After he bumps it what is the length of the case? When he fires the round what is the length of the spent casing?
</div></div>
My questions as well.

Perhaps he's bumping the shoulder back more than he thinks. He may think it's .001" but it sounds like it's more than that. Setting up a resizing die to bump .001" isn't easy to do without gauges to measure your cases. Setting up by the old "first time the bolt closes easy" can make you bump it back .005" - .010" instead of .001."

The fact that it doesn't occur on virgin brass sure makes me think it's a reloading issue not a chamber/gunsmith problem....

 

[308saiga]

Re: Case blackening at the neck

I would like to know if he extends the bullets out to the lands? If so this could also be an issue, if you extend it out too much the bolt wont close? I suggest trying factory ammo to see if it closes properly..........

 

[V-hunter]

Re: Case blackening at the neck

Hey Guys

I size all my new brass with a standard full length sizing die, which sizes the necks of the cases all the way to the shoulder junction. I do this with them all so that they are all uniform and then expand them out with the expander mandrel in preparation for neck turning. I neck turn them (clean up)and have to size them back down for the correct neck tension. I only do this with new brass.

The new brass length is from 2.005" to 2.008" and I trim them all back to 2.003" before neck turning. The chamber of the rifle measures 2.040"

When reloading brass for the second and subsequent times I use a forster bushing bump die which only bumps the shoulder and leaves the rest of the case untouched which I find does not overwork the brass. My sized cases measure 2.003" in length and once they are fired measure 2.0045".

I have also tried various seating depts from a 10 thou jam to 20 thou off and still the problem persists.

For measuring the ammount of headspace and bump needed I use the Sinclair bump gauge which I find very accurate.

I have tried unturned brass and still the powder residue is present.

And it was not until this weekend that I tried factory ammo and it too has signs of powder residue on some (not all) of the cases.

If ye guys have any ideas how to rectify this problem I would really appreciate it.

V-hunter

 

[Greg Langelius *]

Re: Case blackening at the neck

I guess the rifle is staying where it is...

The brass cartridge case serves as a container and a pressure gasket. The open mouth of the case is intended to expand and seal the bore off from the area behind the bore.

It does this with varying degrees of effectiveness, and that effectiveness is not something that's either uniform or constant.

For the most part the critical issues are pressure and brass hardness. Less pressure and harder brass necks will impair the sealing process.

Honestly, at the pressures we're talking about, brass is pretty flexible. It will always expand to conform with the chamber dimensions. And further. Both the brass and the chamber are somewhat expanded at peak pressures. Then the brass springs back as the pressure is vented and everything shrinks back to normal. Too much pressure and the brass doesn't spring back enough, causing extraction issues, but that's not for this discussion.

I'll venture that the leakage and soot is being deposited as the pressure is beginning to build, before it can really wham that brass out to meet the chamber. Depending on the pressure curve and the neck hardness, the degree will vary.

But the point here is that no, read zero, harm is being done here, either to accuracy, or mechanically. Yes, the chamber and necks will require some cleaning, but beyond that, this is a non-issue. We expect soot to be present after firing, it's one of the main reasons brass gets tumbled. Chamber cleaning is customary as well.

What's more, beyond cleaning the brass, and maybe annealing it, there's not a damned thing any of us can do to prevent this. This is clearly not a gunsmithing problem.

Getting one's shorts in a twist about cartridge case sooting is about as relevant as complaining that it gets dark at night.

It happens, get over it; and quit wasting time and bandwidth over this non-issue. If this is the worst thing you have to complain about, you're already way out there ahead of pretty much most of us.

Move on, this issue is done.

Greg

 

[308saiga]

Re: Case blackening at the neck

In terms of reloading, I have read countless books that state that factory ammo casings, when bought from a shelf, are 2.015 in length and you are supposed to trim down to 2.005 max, even though when you buy a new bag all you do is load the rounds at 2.015 (different casings may vary). You are saying that you use 2.003 and trim your brass accordingly. I would recommend trying this find some brass that is greater then 2.011 and trim to 2.010 max, do not bump, load and fire..

I have great success using this length....

 

[tbeasley]

Re: Case blackening at the neck

I have an issue with your loading technique. Try leaving out the resizing the neck after the fact you "cleaned up the necks".
Try:
1) FL new brass (standard .308)
2)"clean up" brass if u like to FIT in ur chamber
3)Load primer, powder, bullet and SHOOT!!
4 NOW!!! Is when u use the Redding Type S bushing die to get ur required neck tension.

New Brass will have a tighter neck tension than u think. If the new brass is shooting lights out, then get inside measurements and try and duplicate that load the very best u can, This is how I load my 6.5-284 and shot several under 2" 5-shot groups at 600yds.

Hope this helps
-tim

 

[xs hedspace]

Re: Case blackening at the neck

I didn't read ALL this thread, but my 308 Palma rifle blackens the case necks, probably because I use Moly coated bullets. Just won a turkey on a 100yd bench rest event, with 4 guys shooting 6PPCs against me. OK, so I had to enter 6 times to win one bird, but all my shots were within 1/8" of center. Don't worry, be happy----

 

[TCA4570]

Re: Case blackening at the neck

It took 24 or 25 Posts before somebody asked about OPies load?

 

[Nessal]

Re: Case blackening at the neck

That is normal. If that scares him, I hope he never owns a AR15.

 

[raptorfendercash]

Re: Case blackening at the neck

Mikki you have handled this like a true professional which by reading all the post in this thread is alot more than some are willing to do.V-hunter good luck,sounds like you have found yourself a good smith,dont blame you for wanting to know why something is the way it is,problem or not.Most of the smart ass comments would never in a millon years get spoken if you were standing in front of some of these guys talking to them,guess the keyboard makes you a know-it-all bad ass.Good luck.

 

[gamma]

Re: Case blackening at the neck

Thanks for the kind words. Well to be honest I dont know that theres any other way to operate in business. You deal with every client as though he was your first, if you dont he could potentially be your last. Get a reputation of not sorting out clients needs and it becomes a very slippery slope.

 

[mscott]

Re: Case blackening at the neck

It sounds like you've done all you can to the cases, but have you tried a different powder? I use Retumbo in a 7mm RM and my cases are worse than those shown. I also anneal my necks, but it doesn't help. If I load with RL25 my brass comes out very clean, so it seems to be a powder issue for me. I like Retumbo better, so I just deal with it. I'm guessing it takes the Retumbo a milisecond longer to build pressure, but that's really just a guess. Can you just fire 5 factory rounds and see what the cases look like?