Sticky bolt on hand loads

[RustyRick]

My brother and I bought 2 - Model 660 Remington in the 6.5 Rem Mag caliber in a 18.5 inch barrel about 40 yrs ago. I didn't keep mine for very long for the reason below.

Factory loads eject NO problem. For all HAND loads I need a 2x4 and a light tap to pull the bolt back. The lift is usually OK, but sometimes a wee bit stiff, BUT NOT OFTEN and not bad.

Now before you say it's excessive loading, hold on. I've been loading for close to 50 yrs. This is the only gun I've ever see do that predictably. No let me list for you the loads.

Sierra HP Varmiter 85 gr, 4350 @ 52.5 gr and up to 55.5 - all stick, every one.
Hornady Spire Point 140 gr, 4831 @ 49.5 to 51.5 MV avg 2500 fps
Nosler AB 140 gr, 4831 @ 51 to 53 MV avg 2500 fpc

Factory Rem Core-Lokt 120gr, MV 2800+ fps

Primer pockets aren't stretching, I have around 5 shots out of the bras and no sign of cracks. Primers aren't moon cratered any more from my light loads to the heavy loads.

We're sure looking for a lightbulblightbulb idea.

 

[Clark]

Sticky bolts are mostly caused by plastic deformation of the brass.
Deformation that will do that can be made with a lot less pressure of the lug abutments in the receiver are dented from previous heavy loads. Shooting the rifle with the barrel full of rain water will do it.

 

[RustyRick]

Rain water would be a scary situation for sure. Both guns did it from the get go.

I've never heard of plastic deformation. What's that?

 

[Clark]

When you deform something, and it goes back to where it was afterwards, that is elastic deformation.

When you deform something, and it does not go back to where it was, that is plastic deformation.

Brass cases are elastic for the first ~.001 or .002", and then plastic.

 

[Gunpoor]

Have you tried to neck size only on the once fired factory brass, or tried new brass? Have you done any measurement comparisons on brass between once fired factory ammo and your handloads after firing to see where the brass is expanding so that it is sticky? I wonder if you are over-sizing and this is causing the sticky situation.

 

[SidecarFlip]

Sounds to me like the old headspacing issue. Ever check the datum on a fired case and then bump the shoulder back 0.001-0.002 on the resized case per chance?

Not hard to do, even with a non bushing FL resize die.

I never neck size anything, I should sell all my NS dies as I never use them.

 

[RustyRick]

Here are some measurements with SAMMI specs for what ever their worth.

 

[RustyRick]

What's datum?

A fired case has to be the dimensions of the chamber. So why would a person ever use FL case sizing dies if the case is going back into the gun it was fired from?

I was about to order NS dies for this caliber.

Thanks everyone for your input!

 

[Canadian Bushman]

A datum is the place a mesurment is toleranced from. Concerning headspace its the head of the case or the boltface.

A fired case isnt always the size of the chamber. It typically is about .001 - .002 inch smaller than the chamber because of the elastic properties described by clark. Unless it is acted upon by high pressures deforming it permanently, which is more common with magnums.

Some folks like fl dies because it assures a case will feed and chamber easily and some people also get better accuracy with loads in cases that have been bumped among many other reasons. There is actually a really good thread on this subject in here somewhere.

http://www.longrangehunting.com/forums/f28/neck-size-full-length-size-50053/

 

[Clark]

Datum in literally the singular of data.

In engineering, Datum line is a line to which serves as a reference.

In the context of SAAMI drawings and headspace, datum is short for datum line.

In belted magnums there is a datum line, where the shoulder is .420" in diameter, but that is not how the headspace is defined by the drawing. They use the belt.