Stripped bolt

[Willie]

I have always used a stripped bolt to determine my brass measurements, to set up bump and to measure base to lands, with the different bullets I shoot. This has worked great in every rifle I own, until NOW.
My latest build is a 6.5 Sherman on a Tac 300 action, fire formed .280 Norma brass. My 2x fired brass is measuring 2.157" base to datum with Whidden headspace gauge. All measurements show it to be fully formed.
I stripped the bolt, to check if I needed to bump shoulders and bolt wouldn't drop. I then set up my Whidden FL sizer and bumped shoulder back .001". Because on fired brass it only took light pressure to drop bolt, I figured one thou would do it. Same pressure, so I bumped another thou and so on. I ended up bumping .005" and pressure to close bolt was the same as I started with. What the heck?
The barrel had been nitrided, so I polished the chamber and neck and borescoped it and found nothing. I then marked up a case and chambered it, no marks.
The light finger pressure to close bolt is fine with me, but the slight drag on closing, makes it's very difficult to determine when a dummy, with bullet seated, is free of the lands.
I have been using this method for many years and never had this problem. So I need some input from guys using the stripped bolt method. What the heck is my problem????

 

[Homerange]

Could the chamber reamer and your FL die possibly have different shoulder angles ?

 

[hogpatrol]

WAG, base not being sized enough?

 

[joshb]

Hog prolly got it. It may be too big at the base. Measure unfired and compare. Check total length while you're at it. You might need a trim.

 

[LHSmith]

A bolt click on extraction is usually encountered when the base of the case is not sized enough. It could be problems induced by a poor ejector setup.

 

[Willie]

Forgot to mention, it's a 40* shoulder. Cases were trimmed to spec. There is no bolt click, when I ease bolt up for extraction. The only suggestion I haven't thought of is what HomeRange posted. The Whidden die might not match the shoulder angle exactly. If that's true, I bumped it well past where there would be any contact. It has to be in diameter, somewhere. Either in neck or case body. I'll prepare another totally marked case and double check for contact. Thanks guys.

 

[dmoran]

Is there any similar resistance when closing the "stripped bolt" with out a case?
If so, the bolt is contacting the barrel slightly.
Donovan

 

[Willie]

Nope, it falls easily, no resistance at all. Just like all my other actions. It has to be in the case, but last night I marked an entire case with felt tip and examined closely. Slid it under extractor and chambered it very carefully and removed it gently. Back under a magnifier, it showed no visible mark. I'm gonna try it again, as I may have missed something.

 

[Joe Salt]

Hog prolly got it. It may be too big at the base. Measure unfired and compare. Check total length while you're at it. You might need a trim.


Make sure you put the marker on the mouth of the case!

Joe Salt

 

[Willie]

Sure thing, Joe Salt. I also colored the mouth on case last night & even the extractor groove.

 

[tunered]

Whats the chance of having your gunsmith ream a die with the same chamber reamer.?

 

[mac86951]

Nope, it falls easily, no resistance at all. Just like all my other actions. It has to be in the case, but last night I marked an entire case with felt tip and examined closely. Slid it under extractor and chambered it very carefully and removed it gently. Back under a magnifier, it showed no visible mark. I'm gonna try it again, as I may have missed something.

May take a few cycles to wear off the marking if its a larger surface area.

 

[Willie]

I finally found the problem. I formed a false shoulder on the parent .280 cases and it was completely gone after two firings on the random cases, I measured (20 of 50). I started over this evening with a new dummy case and the bolt dropped easily with a .001 bump. Soooo! I went back and started measuring original case again. This case had a residual .015"x.020" false shoulder against the shoulder/neck junction, that I had missed. I had already set up my Turner, so I turned into the shoulder, cleaned case and chambered it. The bolt dropped half way. A .001" bump made it totally free. I checked the rest of the cases and found 6 more with a trace of the false shoulder. With a turn and .001 bump, they all chambered. Was my bad, that I didn't notice what was going on. I would like to thank everyone who offered advice or solutions. This is a great forum, would have been here earlier, but I'm technically inhibited.

 

[joshb]

Yay! I like happy endings. Glad you found the problem. This site is a great sounding board. It's good to get more eyes on the problem. Some times I get so myopic, I can't see the obvious.

 

[hogpatrol]

Thanks for the update.

 

[wildhog]

Good after action report .
REGARDS
JIM