neck bulge after firing

[jesse1004]

I had my 6-284 rebarreled 6 months ago and just got around to start load development on it. Before I had a 10 twist now I went with the 8 for the heavier bullets. I went to the range on monday and fired 2 shots. After the first shot I noticed a bulge on the neck of the case (.008 worth of bulge). So first off I checked for any kinds of pressure signs on primer and there were none. I was only loading 45 grs of N560 which should be on the light side. My next thought was maybe the case necks needed trimmed but they are .02 under saami specs so that shouldn't be the issue. keywords -"shouldn't be." So hoping it was a fluke deal I fired another shot and I got another bulge. Needless to say it was the last shot. Any ideas what could be causing it? I will say that when I had this rifle rebarreled I let the smith know I would be using 105-115 gr bullets. Well he must not of understood what I was saying because there is almost no freebore. Could the overseating of a bullet be the cause? With the 115gr vld I have .78 of bullet exposed and .57 of bullet seated into the case, which is a lot considering the neck is only .265 long. Also neck tension is only .002. I have tried contacting the gunsmith with no luck to talk to him or possibly get a reamer print. Any ideas would be appreciated.

 

[stacy]

IS THE BRASS BEEN TRIMMED TO LENGTH ALSO DID U SIZE WITH A EXSPANDER DIE OR BUSHING DIE

 

[jesse1004]

redding bushing die and the brass is trimmed to 2.155. Saami specs are 2.160 and 2.170 max

 

[Milo 2.0]

Take some more pics of the case mouth and post them. Looks like a distinct line above the bulge, like the neck was under reamed. I'm not implying, but if that's the case, you have issues!
Are the rounds hard to chamber?

 

[jesse1004]

It actually chambers very nicely. Just ever so slightly harder than with no round in the chamber

 

[jlow]

The times I have seen this happened, it is with thin neck brass fired in a chamber with generous dimensions i.e. factory chamber. The mouth of the neck will not expand out as much as the rest of the neck perhaps because it is not as soft and this is what you get.

 

[jesse1004]

I do have some hornady brass with a .014 neck thickness. Now I am using lapua trimmed down to .011. So that would give me another .006. Right now loaded rounds are .265 and the widest point on the neck is .281. That is a whole lot of neck expansion

 

[243winxb]

widest point on the neck is .281"

Maximum chamber. Try a hotter load, to expand all of the neck.

 

[Old Navy]

I do have some hornady brass with a .014 neck thickness. Now I am using lapua trimmed down to .011. So that would give me another .006. Right now loaded rounds are .265 and the widest point on the neck is .281. That is a whole lot of neck expansion

That is excessively large diameter for a 6/243 caliber....... I foresee further issues, sorry to say !
I suggest to talk to the gunsmith.

Donovan

+1 Later! Frank

 

[Keith Glasscock]

While it would be hard to determine over the internet, I would suggest that you take a chamber cast. It looks like you have a 6.5-284 chamber or a 6-284 with an excessive neck diameter.

Better to have a cast in hand before talking with the smith. If you need cerrosafe and don't want to pay the price, rotometals has a low temp melt metal that works good.

 

[243winxb]

FY1

Loaded round maximum Neck diameters 6.5-284 is .297" The 284 is .320" OP has .281" almost the same as a maximum chamber in 243 win. Yes its big for a 6mm.

 

[liljoe]

The pitfalls of using a reamer your gunsmith owns and probably doesn't have a print for, and no idea what the specs are for it.

You need to find out what the neck diameter is, a chamber cast is the easiest way to do this.

Joe Hynes

 

[Milo 2.0]

You need to find out what the neck diameter is, a chamber cast is the easiest way to do this.

Joe Hynes

Sorry Joe,
The best thing to do is have your smith measure his reamer, while the op has a mouthful of his butt, either in person, or on the phone.

 

[queen_stick]

couple of things,

I agree that's too big of a neck for a 6mm. It will work, but your brass life is gonna be terrible.

Also, I've only seen cases do that when I loaded a primer ONLY. ( I did this just playing around, to see how far the primer would expand the case on its own). The cases came out looking just like yours. With that said, I also agree with above posts about upping your charge... If you decide to keep the" huge-necked chamber", you'll have come up with the charge to blow the cases out 100%