6 dasher hard to close bolt

[6mmxc]

I have an Accuracy International AT-X with a proof barrel chambered in 6 dasher. I have found that when FL sizing alpha brass with a forester FL die I have to bump the shoulder 8 to 10 thousandths to get the bolt to shut without being hard. Does anyone know what could be causing this and what the fix is?
Thanks

 

[Gray420]

I have an Accuracy International AT-X with a proof barrel chambered in 6 dasher. I have found that when FL sizing alpha brass with a forester FL die I have to bump the shoulder 8 to 10 thousandths to get the bolt to shut without being hard. Does anyone know what could be causing this and what the fix is?
Thanks

I am going to tag along on this one. I have struggled with good or enough shoulder bump on my dasher with Alpha brass as well. I started with Redding die, then bought the Redding competition shell holder set, then went as far as getting an SAC die.
I use a Wilson in line seater die and when my shoulder is not correct it will let you know, the case has to be dug out with something it does not fall out like when properly sized.

Are you using an expander mandrel in your sizing die or expanding on separate die? There is a theory out there that expanding in the same process as sizing can pull the shoulder back out as the expanding ball returns out of the case mouth, especially without enough lube inside of the case neck.

Are you seeing swipes on your cases when you chamber them?

 

[Dolomite]

Call Harrells and get one one of their dies.

 

[William Vogel]

I have an Accuracy International AT-X with a proof barrel chambered in 6 dasher. I have found that when FL sizing alpha brass with a forester FL die I have to bump the shoulder 8 to 10 thousandths to get the bolt to shut without being hard. Does anyone know what could be causing this and what the fix is?
Thanks

Not enough information. Is this with new brass or with brass that fit and fired and now the brass must be overly sized to fit before loading with powder and bullet, test fitting? What have you measured on the before and after brass to help determine the misfit?

 

[Mike Casselton]

Sounds more like your brass is fat at the .200 line.
Take 5 pieces of brass, mark them 1-5 and measure the datum, the shoulder diameter, the .200 line and OAL.
Write these numbers down and compare it to a piece that fits your chamber.

Size a piece <.002 from a fired case and retake the measurements. Test in your chamber.
Do the same with another piece, but size it to <.004. Take the measurements. Test in your chamber.

Continue doing this until a piece of brass fits.

Compare the numbers and your answer will be there.

I'm betting it's the .200 line, unless you're beating the snot out of your brass...

 

[AlNyhus]

Before going too far, check the shoulder diameter of a fired case and compare it to a resized case that has had the shoulder back .002. The 'Tony Boyer' method for checking this is easy and will tell you if the problem is at the front end.

With 40 degree shoulders, some dies will let the shoulder push out before it pushes back.

 

[David Wiggins]

Your problem as already stated is at the .200 line most likely .When you push the brass into chamber does your bolt hit resistance about a 1/4” before bolt closure position? Also known as clickers . I use Eric Cortina expander die with a tight base to keep this in check. A 308 small base body die ( a lot cheaper) also will work but it pushes the shoulders out . Eric’s die doesn’t do this . This is my last step before charging the case.In a 30” bbl I push 108’s at 3000 fps , on about 10th firing , and no clickers.

 

[paperpuncher]

Had this exact problem Bras was not getting sized enough @ .200". Call Harrells send em some 3x fired cases and dont look back

 

[MasterYoda]

D4 from Harrell's

 

[Janeau]

Alpha brass work in tandem with their purpose made reamer. All other remedies are just a patch on a dimensions problems of the Alpha brass. Ditch it. Get Petersen or even better go the route of making first class Dasher brass out of Lapua 6BR until Lapua get their Dasher brass out by the end of the year.

 

[NZ_Fclass]

^^^

Alpha Dasher is a different size to Norma (CIP) Dasher. My Alpha works just fine - having the correct chamber. As far as I know, there is no SAAMI spec for the Dasher and most chambers are cut for the CIP spec. I use a Wilson FL die and Wilson in-line seater for reloading the Alpha, with no issues.

 

[cp255]

I have an Accuracy International AT-X with a proof barrel chambered in 6 dasher. I have found that when FL sizing alpha brass with a forester FL die I have to bump the shoulder 8 to 10 thousandths to get the bolt to shut without being hard. Does anyone know what could be causing this and what the fix is?
Thanks

I’ve had the exact same issue. You’re probably seeing inconsistent shoulder bump. I was using a MEC press, and the amount of force needed to feel the shoulder bump was ridiculous—hurt my hand and shook the whole bench.

Last weekend I tried sizing on a larger Lee press (originally bought it for 577/450 Martini-Henry) and it was a night-and-day difference. So much smoother and easier to size.

 

[Gray420]

I’ve had the exact same issue. You’re probably seeing inconsistent shoulder bump. I was using a MEC press, and the amount of force needed to feel the shoulder bump was ridiculous—hurt my hand and shook the whole bench.

Last weekend I tried sizing on a larger Lee press (originally bought it for 577/450 Martini-Henry) and it was a night-and-day difference. So much smoother and easier to size.

Interesting, I am using the MEC press as well and it feels like a tank. I have to screw my die in far enough that I am getting cam over. I am also using the hornady load n load bushings. Maybe I need to try some different. I will pay attention to this.

 

[cp255]

Interesting, I am using the MEC press as well and it feels like a tank. I have to screw my die in far enough that I am getting cam over. I am also using the hornady load n load bushings. Maybe I need to try some different. I will pay attention to this.

I don’t know why, but 6 Dasher has been a nightmare for me to size. For the longest time, I couldn’t figure out why it was so hard to close my bolt. I use the Redding competition shell holders, so I expect them to contact the mouth of my sizing die. One time, when I thought a case was fully sized, I noticed a decent gap between the shell holder and the die. I pushed a lot harder and suddenly felt the shoulder bump way back — probably around 8 thousandths.

The Lee press I switched to is much beefier and has a better lever ratio, so setting the shoulder back is way easier. I don’t know why 6 Dasher is such an issue — maybe the 40-degree shoulder just resists flowing. For reference, I’ve tried both Alpha and fire-formed Lapua brass, and had the same issue with both.