6BR pressure signs low loads

[Dolomite]

So the above were virgin brass at 28.5 first firing, right? And no ejector swipe, or pressure signs. I would think they should rechamber just fine, but they are tight, correct?

Then you resize and get pressure signs, (swipe and hard bolt movement) at the same 28.5?

Thanks.

Jim

Yes that is correct. The sized brass would chamber and the bolt would drop nicely, following the Alex Wheeler method.

 

[Dolomite]

If you can load 28.5 in a case and fire it and not get ejector swipe, (using the same powder) than neither of the above are likely in this situation.

Jim

It’s the second firing that got the heavy bolt lift and ejector marks.

 

[pdhntr]

It’s the second firing that got the heavy bolt lift and ejector marks.

I agree with boltfluter. Try to find the area in the chamber (on the case) that is giving the issue of hard bolt lift. It can be hard to cut a case with a hack saw, but it doesn't take long to file it down in steps, and as he said, it works very well.

You also mentioned coloring it, that can work also.

Interesting problem, good luck.

Jim

 

[JFrank]

Bolt face has no burrs I double checked. I’ll try another lot of varget.

I’m not sure why I get heavy pressure and low velocity. is that from the powder being too fast?

I wonder if I could color up a piece of fired brass insert it into the chamber and look for any rub marks? If not I’ll try and find a way to cut up the brass as you mentioned.

I do have a 308 small base die which I could try. Would it be sizing the upper body of the brass too small? The 308 small base die really squeezes the upper portion of the brass down a lot.


I believe the blown out shoulder is causing by the heavy pressure which is causing the heavy bolt lift.

Measure before and after sizing at the csj and the .200 line as well as the length to record the amount of sizing your die is capable of.
Below I’m comparing two different dies, the one on the left gives me clickers

 

[Dolomite]

I agree with boltfluter. Try to find the area in the chamber (on the case) that is giving the issue of hard bolt lift. It can be hard to cut a case with a hack saw, but it doesn't take long to file it down in steps, and as he said, it works very well.

You also mentioned coloring it, that can work also.

Interesting problem, good luck.

Jim

I have a dremel, going to try and make it to the range to get some fired cases...

 

[Dolomite]

Measure before and after sizing at the csj and the .200 line as well as the length to record the amount of sizing your die is capable of.
Below I’m comparing two different dies, the one on the left gives me clickers

Funny thing I did that and the Redding is only getting the base down .0005. I had the same issue with my 308 and ordered a custom die from Whidden. Should be here in a month or 2.

I have a Forster FL non-bushing die on the way and I can check to see how that sizes the brass.

I wonder if I need a custom die from Harrels or Whidden?

Maybe a SAC die would work as it suppose to size the base smaller but $375 all in is hella expensive.

 

[243winxb]

I was trying to avoid neck turning

You measurement seem to point to no neck turning needed? But if the loaded rounds OD is like the drawing, turning is a must do. The
.2717" at the neck shoulder junction looks like a pinch point?

 

[Dolomite]

You measurement seem to point to no neck turning needed? But if the loaded rounds OD is like the drawing, turning is a must do. The
.2717" at the neck shoulder junction looks like a pinch point?

Is there a rule of thumb for enough neck clearance? like .004 would be a minimum clearance before having to neck turn?

 

[JFrank]

Funny thing I did that and the Redding is only getting the base down .0005. I had the same issue with my 308 and ordered a custom die from Whidden. Should be here in a month or 2.

I have a Forster FL non-bushing die on the way and I can check to see how that sizes the brass.

I wonder if I need a custom die from Harrels or Whidden?

Maybe a SAC die would work as it suppose to size the base smaller but $375 all in is hella expensive.

You may have found your problem .0005 is not enough sizing at the base, how about the CSJ measurements ?
Wilson makes dies.. so does Hornday , name on a door doesn’t mean squat only thing that matters is dimensions

 

[Dolomite]

Loaded round




virgin brass



I wonder if a non bushing die would size that part of the neck down better?

 

[Dolomite]

You may have found your problem .0005 is not enough sizing at the base, how about the CSJ measurements ?
Wilson makes dies.. so does Hornday , name on a door doesn’t mean squat only thing that matters is dimensions

Would the base be causing the high pressure or just a clicker?

My 308 would have the heavy bolt lift at the top stroke or clicker. Didn’t have any pressure signs.

 

[JFrank]

Loaded round


View attachment 1312458

virgin brass

View attachment 1312459

I wonder if a non bushing die would size that part of the neck down better?

Clickers’ mainly but I think that comes as the case expands under increased pressure
.270 That’s pretty tight for a .272 neck

 

[holstil]

No sizing lube left on cases right?
you chronographed both virgin and resized firings?

 

[Dolomite]

No sizing lube left on cases right?
you chronographed both virgin and resized firings?

yes I tumbled the cases after sizing. yes chronoed both virgin and resized and its about the same, in fact the speed dropped 20 FPS on the sized brass.

I guess the barrel still needs break in, I'm waiting to see if the barrel speeds up.

 

[holstil]

Try a cpl cases after sizing without tumbling.

 

[Dolomite]

Clickers’ mainly but I think that comes as the case expands under increased pressure
.270 That’s pretty tight for a .272 neck

CSJ is .459 sized and .461 fired.

I'm currently using a redding bushing die, I have a Forster FL die coming to see if that would make a diff.

If I end up with clickers definitely going with another custom die.

 

[Dolomite]

Try a cpl cases after sizing without tumbling.

that would be another good test, I thought the lube on the case affects the ability of the brass to grab the sidewalls of the chamber which causes heavy bolt lift and pressure signs on the brass face?

 

[holstil]

I believe it does.

 

[holstil]

I don’t like shiny chambers or brass.

 

[243winxb]

Loaded round. I wonder if a non bushing die would size that part of the neck down better?

The loaded measurement is taken where the bushing has sized.

Loaded round .270" ? Neck chamber .272" ? The bushing is not an issue, unless its hiding a donut.

A bushing die can NOT be used when neck turning.