Hard bolt pull?

[YZ-80]

Guys,

I got my Delta 5 shooting pretty good with the 6.5 CRDM barrel. Today at the range, however I had a bit of an issue on occasion pulling the bolt back. No heavy lift. It would happen about every 3rd or 4th round. I'm running 4th cycle gunwerks brass and I'm bumping .002 to 1.504" on the Sinclair comparator. No signs of pressure on the brass, no cratered primers, etc. Headspace is good. This is a 37.2 grain charge under a 143 ELD-X and I'm .003 off the lands. I'm wondering what gives? I have a theory that maybe the neck turning striations have created more friction in the throat upon expansion but I didn't have any loads that were un-turned to test this theory. Maybe that or dirty bolt raceways or mortises? Any ideas? It didn't seem to do this as a .308. Thanks in advance for any insight.

 

[milo-2]

Your die is not sizing your case base enough, do you get a click upon bolt lift?

 

[fabricator21]

do you get a click upon bolt lift?

What does a click indicate?

 

[milo-2]

To me it indicates your brass was too big in diameter before you fired the rd. Why it does it, cannot answer that.

 

[YZ-80]

Your die is not sizing your case base enough, do you get a click upon bolt lift?

This seems plausible because in order to only get a .002 bump, I'm just at shell holder contact with the bottom of the die with maybe a very minor cam-over. But if I follow the RCBS instructions I get a distinct cam-over and end up bumping the darned things .006 or better. Maybe if I bump .004 or so I can find a happy medium? Kinda bummed out cause it's shooting so well.

 

[L.Sherm]

As Milo stated measure at the .200 line on fired and sized brass.

 

[fabricator21]

To me it indicates your brass was too big in diameter before you fired the rd.

In that case wouldn't the bolt have resistance when closing?

 

[338 dude]

This seems plausible because in order to only get a .002 bump, I'm just at shell holder contact with the bottom of the die with maybe a very minor cam-over. But if I follow the RCBS instructions I get a distinct cam-over and end up bumping the darned things .006 or better. Maybe if I bump .004 or so I can find a happy medium? Kinda bummed out cause it's shooting so well.

Try a set of Redding competition shell holders you can reduce the sizing while still making contact with the base of the die

 

[L.Sherm]

But if I follow the RCBS instructions I get a distinct cam-over and end up bumping the darned things .006 or better.

This is why die instructions suck.

 

[L.Sherm]

In that case wouldn't the bolt have resistance when closing?

I think Milo was referring to the brass being big as the dies not sizing the brass enough down at the .200 line.
As you shoot brass they grow, so if your dies are not sizing the brass down far enough ( .001-.002) at the web they will get to the point were they can get hard to extract.
3or 4 firings are about were brass is be coming fully fireformed so let's say your brass are only getting sized by .0005 smaller just enough to chamber but get hard to extract after firing.

 

[L.Sherm]

Poor or no primary extraction can cause this type of issue also.

 

[rsmithsr]

DIRT.....CLEAN the extractor really well.
fix the cause, not the symptom

 

[L.Sherm]

The extractor is gonna have nothing to do with the bolt pulling back hard.

 

[Stiltsville]

OMG, the famous "click" appears on yet another thread.

If a case head swells so much that extraction is hard you have too hot a load or too soft brass.

It has nothing to do with the sizing BEFORE shooting. You can the bejesus out of a case and it still will grow to fit the chamber.

Doubt it ? Get some small base dies and use the same load and brass.