220 Swift case issue

[Bruce Mc]

I have a new lamp on my reloading bench with a large magnifying glass and on my last batch of fired 220 swift brass I noticed an irregularity on the tip edge of the neck. It appears that the first hundredth or so is tapered after firing. I can't say for sure if this has been occurring all along or if I just noticed it. What could cause this, the bullets were not crimped. Any idea?

 

[JD338]

Interesting. Maybe some carbon buildup in the chamber?

JD338

 

[300WSM]

Question...

Did you trim these cases at any point before?

It sure looks to me as it's some remaining type chamfer

 

[filmjunkie4ever]

Maybe your throat is just a bit short and the cases are a bit long?

 

[Bruce Mc]

These were new cases that I neck sized and deburred and i.d. chamfered. After firing they're still shorter than max.

 

[Bruce Mc]

Interesting. Maybe some carbon buildup in the chamber?

JD338

I'm gonna give the throat an good scrubbing with a carbon remover and see if it repeats.

 

[RL338]

Do you trim to the shorter side?
Just a guess that the new brass is longer and being pinched by a carbon ring as other have mentioned.

 

[NYDAN]

Although it is unlikely, if you think the chamber neck might be too short, you could check the length of the chamber neck with one of these: https://www.brownells.com/reloading...s/sinclair-chamber-length-gage/?sku=749000811

 

[Bruce Mc]

Seeing as the necks are always blackened after being fired I'm leaning on fouling. I'll get back after I give it a good scrubbing and shoot some more.

 

[300WSM]

Maybe your throat is just a bit short and the cases are a bit long?

If what you're suggesting is going on I would think the OP would definitely notice a different feel upon chambering loaded rounds

These were new cases that I neck sized and deburred and i.d. chamfered. After firing they're still shorter than max.

You didn't deburr thr O.D.? A lot of those tools do both

 

[300WSM]

Something going on there...

 

[SJB358]

Seeing as the necks are always blackened after being fired I'm leaning on fouling. I'll get back after I give it a good scrubbing and shoot some more.

Let us know what you see after the cleaning. Looking at the pic, I can’t say I’ve run across this.

 

[Bruce Mc]

Let us know what you see after the cleaning. Looking at the pic, I can’t say I’ve run across this.

Scotty that little taper mics out at 005" at the tip less than the neck. It goes away when the case is resized.

 

[jimbires]

something else to look at .

are you crimping ? if not , I'd check the die setting to be sure the body is high enough to not touch the brass case , when seating a bullet .

I don't crimp any rifle ammo , I'm not sure what it looks like after being fired .

 

[Bruce Mc]

OK, so here is where I'm at, I scrubbed the throat and the little taper on the fired cases persist. I did a dimensional check on the brass and found everything within spec. The cases were all new and unfired cases (Hornady flavor). The cases measured 2.195 before firing and 2.200 after. Of course the spec dimension for the Swift is 2.185 to 2.205. So I took a look at the chamber and geez, upon repeated measurement with a vernier I found the length of the chamber is 2.190. I measured it multiple times and the measurement was consistent. Then there is the bevel that blends into the throat. My thought is that due to I.D. tolerance the case is able to go into that bevel but upon fire it forms to the bevel. I don't have a precision id micrometer but the readings on the vernier are consistant. Would ya'll surmise the next thing to do would be trim a case to the minimum spec of 2.185 and see what happens?

 

[RL338]

A inexpensive Teslong borescope would go a long ways to see if that is your issue.

 

[Bruce Mc]

Fired off some rounds trimmed to minimum length (2.185) in both new brass and fired brass I resized to the chamber. I also fired brass trimmed to 2.200 on resized brass and untrimmed (2.195) new brass. Only the the new brass ended up with the tip of the neck tapered after firing. What the heck is this telling me? I'll accept OC as a response.

 

[RiverRider]

Hey Bruce, PM me your mailing info. I've been trying to peddle some perfectly good Norma .220 brass (100 pieces fired once mostly, some of it twice) and no takers. I'd rather give it to you than keep dumping the price.