To make a long story short: bought an inexpensive midway barrel in 35whelen a while back and decided to turn it into the 40 degree ackley version. Anyway, made cerrosafe chamber cast out of it after headspacing a second time and the cast came out with a defined lip toward the case mouth end. Here's the casting measurements:

larger neck diameter: .395"
smaller neck diameter: .388"
total neck length: .490"
length of narrow neck section: .060"

Now the barrel started .020" short, and I had to take off at least another .020" after screwing up the chamber cut the first time. For the life of me I can't understand where the little lip in the end of the chamber (neck) came from.

The chamber headspaces fine, I'm guessing about .002" past the go gauge dropping. An unfired factory round makes a nice tiny little shiny ring way up on the shoulder when chambered and extracted. Got a once fired case and compared it to the cast and the mouth ends up right in the middle of the narrow little band at the end of the chamber.

So did the barrel maker make too deep of a cut when they made the initial drill before finally short-reaming the chamber? Or did the reamer I rented have too short of a neck section? Is this something I should be overly concerned about or will I just need to have shorter than usual brass to keep it from pinging into the narrower section of the chamber?

I know the right thing to do would be to have the barrel set back a ways and recut the chamber, but that would mean renting the reamer and gauges again and I'm basically as cheap as they come.

Any thoughts on what the lip is or how it happened would be appreciated. Could we please keep the Midway and Ackley bashing down to a reasonable level also?

thanks,

irwin

quote:

Got a once fired case and compared it to the cast and the mouth ends up right in the middle of the narrow little band at the end of the chamber

Can you explain this in more detail?

Also will a bullet fall into the fired cases neck?

A chamber casting picture would help clarify it, but as I understand it, the larger diameter "ring" is to the rear, being cut away with the the rental reamer.

I would purchase a new 35 cal throater only reamer, but have the company measure to help "cherry pick" the size you need to cut it out, SAAMI dimensioned or not.

A 7mm RemMag I set back last month did the reverse in the shoulder area. The rental reamer I received had been sharpened too many times, lost too much diameter in the shoulder, and thus left an approximate 0.003" per side smaller stepped ring inside the shoulder of the chamber.

It shot very accurately, but I could not let it go back with the fired brass showing the step ring.

A brand new PGS reamer luckily removed the smaller shoulder step, without changing headspace. I say "lucky" because the new reamer could have been dimensioned shorter and cut the belt too deeply.

I'll see if I can whip up a picture tomorrow, but basically this is as best as I can describe it.

With the base of the casting down, measurements going up:

case body at body/shoulder junction: .459"
neck at neck/shoulder junction: .396"
larger of 2 diameters at case mouth: 394"
smaller of 2 diameters at case mouth: .388"
throat diameter: .3625"
final diameter: .358"

.3625"(throat) | |
| |
.388" (mouth) | |
.394" (neck) | |
| |
| |

I know that looks like a first-grader did it, but that's the best I can visualize it right now.

Savage, the once-fired case wasn't from my rifle, it was from a friend's of mine. Odds are that we used the same reamer to cut the chambers, though.

The spooky thing about all this is that I wouldn't even know there was something wrong (if there is) if I hadn't taken a chamber cast. It headspaces just fine and I was going to head out and give it the smoke-test this weekend.

thanks,

irwin

Ok, are saying is that there is a "sub shoulder"
at the junction of the ackley shoulder and neck?

AllanD

Can you chamber that fired case in your rifle? Does that crimp the neck? What is the dimension from the base as to where the chamber gets smaller on the neck? Is it less than the maximum length of a case?

Will the fired case from the other rifle accept a new bullet easily?

Hopefully this picture posting will work and might make it a little easier to understand:
[img=http://imagevenue.com/loc30/th_a0f_cast.jpg]

What a doofus I am!

The picture works, but it looks like the hosting service is a porn directory link warehouse. If anyone has a better place to host the pic at, let me know and I'll do it from there.

Probably should have checked out the site first.

Anyway, if you can disregard the lines in the cerrosafe you can see that the bottom section is the case body(.458"), then the shoulder, then the main part of the neck(.395"), and then the "sub-neck" at the case mouth(.388"), then into the throat(.3625") and rifling.

The distance from the top of the shoulder to the next diameter change is .425", and the length of the sub-neck at the very end is .070", give or take.

Savage, the unsized case from the other rifle chambers fine in mine, his were REM factory rounds that had a pretty heavy crimp on them and it didn't feel or look like mine crimped the end of the cases. I didn't get a COMPLETE chamber cast, I usually stick to from the top of the body to a little ways into the riflings.

I'm starting to think I got a crappy barrel from the outset. I'm not sure how the initial cuts are made, but it looks like there was an initial drill with just a standard bit to get most of the meat taken out and then it would have been "short-chambered" with a rougher/finisher. It seems like that initial cut just went too deep. If anyone else has any other ideas, I'd love to hear them. I think I'll eventually have to have the barrel set back and re-chambered, I was just trying to avoid it if I could.

thanks,
irwin

you ran a good reamer into a poor hole I suspect....In many cases with some calibers you will end up with a ring because of the difference in reamers...If you open a 222 out to a 223 you will sometimes get the same efffect.