I’m stumped, what am I overlooking?

[Lovellr653]

Okay I'm stumped. New unloaded Lapua brass from the same box, some chamber with no bolt resistance others there is significant resistance closing the bolt. COAL between the cases are the same, case web diameter is the same case length off the shoulder is the same (+/- 0.001"), neck OD are the same. What the heck am I overlooking? I ran a few cases that are hard to close the bolt on through a FL sizing die with no change. Also worth noting there is some bolt swipe on the case heads with the hard bolt closing brass. This is in a new Carbon6 barreled 300PRC that I cleaned up with an AW2 reamer and a terminus Kratos action. I triple checked with the go/ no-go gauges which checked out as good. Any ideas are welcomed.

Thanks

 

[vacrt2002]

New rifle or trusted rifle? It sounds like the shoulders need to bumped back in your die??

This happened on a new rifle and it was the chamber need to be cleaned up with a finishing reamer. Yeah it was a post BK Rem 700.

 

[Lovellr653]

New rifle, I just cleaned up the chamber with the AW2 reamer. I too feel like the shoulder needs to get set back on the brass. The FL sizer is maxed out for shoulder set back.

 

[vacrt2002]

Stumped this chump too!!

 

[RichCoyle]

Turn a few thou off the bottom of the die.

 

[Lovellr653]

Turn a few thou off the bottom of the die.

Honing down the shell holder would accomplish the same in a sense correct? I don't have a machine at my disposal to take off the die.

 

[Lovellr653]

Now that I'm looking at the shell holder it looks like it wasn't ground square at the factory. The bevel on the backside is noticeably taller than towards the front. Checked my other RCBS holders and they are not like this.

 

[lhouston78]

Order a bump shell holder set

 

[KNOTFERSAIL]

I have "polished" a few thousands off the top of some of my shell holder's, works great.
But…before you do that take your decapping pin out and put a strip of paper folded in half in your shell holder under the brass head stamp, run it up in the die, that will give you an extra 1-2 tho set back. If that solves your problems then polish it off the shell holder.
Paper shim goes here.

Hopefully makes sense.

 

[Lovellr653]

I have "polished" a few thousands off the top of some of my shell holder's, works great.
But…before you do that take your decapping pin out and put a strip of paper folded in half in your shell holder under the brass head stamp, run it up in the die, that will give you an extra 1-2 tho set back. If that solves your problems then polish it off the shell holder.
Paper shim goes here.

Hopefully makes sense.

Great trick! That's all it needed.

 

[ButterBean]

Did you pull bullets ?

 

[Lovellr653]

Did you pull bullets ?

Never even made it to that step of the process.

 

[Lovellr653]

So I think I figured it out gents. My initial measurements taken from the shoulder were good but not precise enough. Long story short I measured my go gauge with a comparator which came to 3.227". The brass that I couldn't close the bolt on were (I'm guessing here since my calipers don't read to this detail) 3.2775"-3.276". So if my reasoning is correct, my chamber is at minimum SAMMI spec. My FL match master sizing die wasn't able to knock back the shoulder enough. I took a couple thou off my shell holder and was able to bump the shoulders back to 3.275" and now they chamber without any resistance. I also found the first shell holder I was using wasn't milled square and had a significantly high edge on one side.

 

[victor3ranger]

Awesome