Bolt hard to close... Problem?

[Peakbagger46]

Got it fixed

Messed with the die this morning and found out it had more adjustment than I thought, the brass now chambers properly, and I am anxious to get out and shoot the perfected rounds!

Once again, thanks. I am not very mechanically inclined, and I appreciate all the help.

 

[counterclockwise]

What does moving the shoulder back mean...



It means moving the conical section of the case (top arrow) straight back, or in this diagram, straight down toward the case head (bottom arrow).

A properly sized, bottleneck, rifle case will register the assembled cartridge lengthwise in the chamber by contact at the case head surface against the bolt face when locked--and at the shoulder or conical surface of the case in the chamber.

The fit should be a slight clearance fit. In other words, there should be some rattle space between case, chamber, and bolt face. Most reloaders try to keep that rattle space down to a few thousandths of an inch.

When the round is fired, the case stretches lengthwise and closes that rattle space to zero. After firing, the case should spring back to almost the original length.

There are one or two exceptions to this lengthwise relationship--purposely driving the bullet into the start of the rifling before firing, or belted magnum registration, IIRC.

 

[JimKirk]

In the above drawing, the shoulder(angled) is the area from the upper black arrow to the beginning of the neck. The body is what that is between the two black areas. Thus if you shorten the case body it will move the shoulder back, but it is the shoulder that has to be moved.

Jimmy K

 

[Riss]

Now if you check and properly locate the bullet off of the lands, somewhere between .015 and touching and you just might close up those groups a little.

 

[Bart B.]

counterclockwise claims:

A properly sized, bottleneck, rifle case will register the assembled cartridge lengthwise in the chamber by contact at the case head surface against the bolt face when locked--and at the shoulder or conical surface of the case in the chamber.

Well, almost correct. You're forgetting the forces applied to the chambered round. Consider the chambering of a rimless bottleneck cartridge.......

First, the ejector. If you bolt's got a straight line ejector near the edge of the bolt face pushed forward by a spring, than spring's gonna push the chambered round as far forward as the chamber shoulder allows. For example, if the chamber has exactly 2.000 inch headspace (bolt fact to shoulder datum) and the case has 1.995 inch headspace, the case head will be .005 inch away from the bolt face with its shoulder pressed against the chamber shoulder. The front of the case is perfectly centered in the chamber by the coned case shoulder mating with the coned chamber shoulder

Second, the extractor pushes the case body's back end against the chamber wall. Extractors are spring loaded, too, as the press against the extractor groove. This ever so slightly cocks the loaded round at a tiny angle in the chamber. How much is determined by the diameter differences between chamber and case body.

And third, when the firing pin smacks the primer, that drives the case forward a few thousandths setting the shoulder back. The case now has less head-to-shoulder headspace than it originally did. But the case stretches back when pressure peaks pressing its head against the bolt face.

 

[counterclockwise]

That is true. By the time the primer ignites, the rattle space has shifted to the rear and shows up between the case head and the bolt face. Also, the fact that the body of the case gets cocked slightly is a function of the fit between case body and chamber wall. Lose fit, short neck, large jump-to-land assemblies, will usually not be as accurate as those that present the longitudinal axis of the bullet to the lands dead center and colinear with the bbl centerline.