"The Bulge" opps make this the "The Squeeze"

[Kodiak99317]

I was searching for a case to use to fire form my 6mm/250 Manson from. Found the 6XC case will fire from into my new chamber very nicely. The reamer I will be using was designed to use 250 Savage brass as the parent case, so 257 Roberts, 243 and 308 brass would also work well after you run it thru a SB die first, since the body near the base is more like .466 on this reamer, in line with the 250 Savage brass body, were 308 is .469. 22/250 Rem brass will work but will leave a bulge at the base of the fired case, as it does in the 6XC I obtained yesterday made from a 22-250 case. By bulge, I mean, if you roll it on a flat surface you see a brighter line area in the body about 1/4" up from the base and on this 22-250 into 6xc (pictured) measured .466 and the area above the extractor grove measures .462, .004" thou bigger. Brass should match the reamer I guess eh... or visa-versa.

I checked the case I have formed on 250 Savage brass in another guys rifle made on this 6mm/250 Manson reamer (it has only cut 3 chambers so far) and it measures .466 down to .463, but it does not have "the bulge"... it tapers down to the .463. Stock fire formed 22-250 is .465 and no bulge can not be measured, you can see one ever so slightly. I know some of the case has to stick out of the barrel/chamber so the bolt can get at it and this is were "the bulge" is happening, I think. I've seen it on other cases too.

Good side of 6xc

Bad Side of 6xc

Question, could this "bulge" equate to problems on the target at LR due to case/chamber alignment? What do you guys think?? Or even pre-mature loosing of the primer pockets? I do not know myself, yet... or maybe I’m thinking too much about all of this… Your options ...

 

[Kodiak99317]

I think I figured it out now. While comparing the heights of separations vs "the bulge".

I once had a 308 Lapua case separate after only 65 firings, but I used two different rifles, while at a HBR match, resizing between reply’s and using a Wilson neck die.

This brass was fired approx 11 times per case in a Tikka with an approx .348 necked SAMMI chamber and I had a Redding FL 308 die that sized to .348 so, not bad brass movement wise. Then, using only 10 selected pcs of this same 100 lot of brass in a new chamber (308 .335 NK) from Sept to Dec, in the off season practicing, I added 50 more firings per case that year. I retired this original lot of brass after that year by shifting all the way right in my box and making new in the left 2 rows. In the four year, once the box was full, somehow I mixed two of these ancient cases with the new year lot. It was after the 3rd reply so 4 more firings including w/u, total 65 firings.

The separation occured while driving the prime out and left the body in the die, which I managed to pick out and get going again. I remember the case actually cost me to drop 2 points at 100yds that day. It fell out of the normal hit location for that day a good 1/2" low. After the separation, I checked the head stamp on all my cases I had in the match block and found one more with the old head stamp (Lapua 7.62x51 vs Lapua 308 WIN) and pulled it from the match lot.

At home that night, I sectioned the one case that did not come apart. You can see two different line areas or partial separations in this 66x case using two different rifles. You can see one upper line inside this case very well and is very pronounced. I think this line comes from pushing the shoulder way back for neck turning where converting the brass from the Tikka’s SAMMI neck to the Rem 700 tight neck. By creating excess head space I created this separation myself, IMO.

The next day I made 10 new pcs of the same lot of brass and used them for 138 times each for that year and sectioned another case. There is less of a line from the 138 times fired case than the old 66 times case. You can see the partial separations on the 171x and 100 plus case are at the same height as the deep line in the 66x case, so this is here the case sticks out of the rear of my rifle’s barrel or chamber, so the bolt face can come up to it and extract it.

“The bulge” I’m talking about is exactly at the true base of the case/body junction, indicated by an “>” on the 6XC case.

Actually the more I look at it and the measurements from yesterday, the more I think it is a small base issue on this practical original 22-250 case which was formed into a 6XC, so “The Bulge” has turned into “The Squeeze”.

I kind of push the 7 times fired and toss the brass rule since I only neck size my tight necked 308 brass unless it is a big match, then I make 10 more new cases! Just lazy I guess...

 

[Hitzy]

The offset buldge happens when your brass is a few thou undersized to your chamber. The head is solid brass so it won't expand (at normal load pressure anyway) so the budge starts at the web. When your case is in the chamber, it rests on the bottom of it (gravity), and when you fire it, it expands to fill the chamber. As it's already against the bottom of the chamber wall, it has no where to expand there so you get the buldge everywhere else around it.