223 hard chambering question

[DLT]

I have been pulling my hair out over my 223 bolt gun that has had a hard bolt close (lapua brass). I first thought it was my shoulder bump, I have tripple checked it several times in the last couple weeks. It measures ok and consistent, I anneal after every firing and my sized brass chambers fine. I then thought i must have screwed up somehow finding my lands. I have rechecked that dimension also. I’m well off them, and bullets are seating consistently. Then I thought I’ll look for a carbon ring with the scope, there was one there and I got it removed and knew then I had the problem solved. Checked with a loaded round again, same hard bolt close. HOWEVER when I load up Nosler brass or lake city brass the rounds chamber fine. My lapua loaded rounds measure .250-.251 while my fired Nosler and lake city rounds measure .255 so it tells me there’s clearance around the neck. What could it be only thing I have not tried is trimming them but sized unloaded rounds chamber fine. The problem does seem to be getting worse as far as how much pressure it takes to close bolt which could warrant possible trim length or maybe even a chamber issue at the case mouth that only long loaded brass reaches. Any tips I would certainly appreciate it.

Discovered early this morning my sized lapua brass case mouth is bell shaped or flared after sizing but prior to having a mandrel open up the necks. Once a bullet is seated I can’t see it or measure it.

 

[CaptainMal]

Measure that Lapua about .200" above the base of the cartridge. See if there is a difference there. That is the reason for the small base sizing dies.

I doubt you will find anything wrong there but a try. Otherwise, you missed something like maybe a thicker rim touching the extractor on the bolt face.

 

[DLT]

Measure that Lapua about .200" above the base of the cartridge. See if there is a difference there. That is the reason for the small base sizing dies.

I doubt you will find anything wrong there but a try. Otherwise, you missed something like maybe a thicker rim touching the extractor on the bolt face.

They measure the same. I get .375 on Nosler, lake city and lapua. Sized, unloaded lapua brass chambers just fine.

 

[SeabeeKen]

Zooming in on that picture you can see quite a large bulge at the case mouth. Almost like a ring. have you tried a chamfer on the outside of a case to see if it makes a difference> Blacken the necks with a sharpie and chamber a round and see where it is scratched off. Neck thickness?

 

[Coyotefurharvester]

Take a sized case that is less than 1.760 in length and chambers correctly, NO primer/powder. Start with the bullet seated out long, seat deeper until dummy cartridge chambers. Otherwise if fitment issue is a tight tolerance, a proud primer can tighten up the bolt closure.

 

[Rocketvapor]

Loaded rounds only?
Bulge from seating without adequate chamfer?
Check length of your trimmed brass with a borescope.

 

[L.Sherm]

Size a case without running a mandrel in the neck then try chambering the case.
Do it without a bullet seated process of elimination.

 

[DLT]

Take a sized case that is less than 1.760 in length and chambers correctly, NO primer/powder. Start with the bullet seated out long, seat deeper until dummy cartridge chambers. Otherwise if fitment issue is a tight tolerance, a proud primer can tighten up the bolt closure.

I will this evening. I have made sure my pockets are the right depth and primers seated below case head. I did that a couple weeks ago I have been all over this thing, Trim length could have threw me a loop because they chamber without a bullet seated

 

[DLT]

Loaded rounds only?
Bulge from seating without adequate chamfer?
Check length of your trimmed brass with a borescope.

View attachment 1564566

I will do that this evening. And yes loaded lapua rounds only. And seems to be getting worse

 

[LCazador]

That bulge on the mouth could be the case hitting the expander cut at the top. Maybe you have a tight chamber so try without doing the expander step. Otherwise I'd say the problem is at the base of the case. My Lapua brass measures .001" larger at the base. If you have a custom chamber it may have a smaller dimension at the base. Measure base where extractor slot ends not at .200" line.

 

[DLT]

That bulge on the mouth could be the case hitting the expander cut at the top. Otherwise I'd say the problem is at the base of the case. My Lapua brass measures .001" larger at the base. If you have a custom chamber it may have a smaller dimension at the base.

The die have been using is standard rcbs full length with the guts removed, I believe the die is open at the top.

 

[DLT]

The flare is gone on loaded rounds. Dont know if it is after my mandrel is run through them though as I just noticed it this morning

 

[LCazador]

Yes it should be open at the top. I thought you were using expander after sizing.

 

[DLT]

Zooming in on that picture you can see quite a large bulge at the case mouth. Almost like a ring. have you tried a chamfer on the outside of a case to see if it makes a difference> Blacken the necks with a sharpie and chamber a round and see where it is scratched off. Neck thickness?

I have not tried that. I only noticed the bell this morning.

 

[old codger]

If a sized and empty case will chamber easily then you are doing something to the case during the bullet seating operation that is causing the problem. How thick are your necks?

 

[DLT]

If a sized and empty case will chamber easily then you are doing something to the case during the bullet seating operation that is causing the problem. How thick are your necks?

I don’t have a ball mic to get a good measurement on it. The flare at the end really prevents the standard calipers from getting a good reading

 

[memilanuk]

Polish the cases so they are nice n shiny. Not because it matters in and of itself, but because it'll make the next part easier to see.

Take a loaded round, coat it head to tail, stem to stern, with a black Sharpie, let it dry a few minutes, and chamber it. You'll likely see exactly where the problem is.

 

[sfinn1]

I have seen this before. Measure loaded outside neck dimensions of different case brands. I have a .223 rifle that does not chamber Lapua brass well but will chamber Winchester with no problem. Not all .223 reamers are the same.

 

[DLT]

I have seen this before. Measure loaded outside neck dimensions of different case brands. I have a .223 rifle that does not chamber Lapua brass well but will chamber Winchester with no problem. Not all .223 reamers are the same.

It’s just weird that a fired case measures .255 and a loaded round is .250. If a fired case was .250 I would know that’s what where the interference was.

Here at work I turned down the bell on one of the cases even with rest of the neck. The neck dia is .005 smaller.

 

[C.E.Smith043]

If you have your seating die down too far it will sometimes bulge the shoulder area, and or could possibly be causing a slight crimp that may be contributing to the problem.

Back the die out at least half a turn and run the seating stem in further to make up the difference