6.5 BPC: N sized brass Won't chamber??

[Vassal]

Hello, I have been a reader of the bulletin and other great features of the sight for a while now; I thank you for all of your guys hard work. I decided to post for the first time because I have a problem that I can not get to the bottom of, and I don't where else to go. Communicating complex problem and answers in notes like this is tough,,, but I've got to try.
I recently recieved my Savage SA back from the G-smith. He trued and rebarrelled with a HART (shilen)#7 barrel in 6.5 BPC (from Pacific tool) This is basically the 6.5 grendel. I broke the barrel in and sighted it in during the first range trip. I collected some velocity and pressure info and used it to make my first "real" loads. I am loading Lapua brass with various bullets, but we will talk about 120M Kings. Powder and primer aren't relevant right now. Heres the rub
The virgin brass chambered and extracted without trouble. BUT when I tried to chamber the N sized only brass it wouldn't go. It isn't just a little sticky, it is really tough. In fact after attempting to chamber a piece of the N size brass, tou could clearly see a rub, graduating to a gouge or cut (meaning it got tighter and tighter) on both the bullet (near the spot where the brass is - i.e. bottom) AND the base of the brass. The strange part is that they are on the same side.
I came home and went through every measurement that I can think of - concentricity is great to OK - the headspace is not the issue as best I can tell - length et cetera. I tried the FL sizer set to bump the shoulder .002" and those brass work fine. BUT if I size only 1/2 way (sizing the neck half way down with the FL die) it is sticky, in the same way.
I can easily chamber the fired brass without a bullet loaded in any orientation. I can chamber brass that has been fired and then N sized only Without a bullet loaded in any orientation also. If I use the N sizer to pinch just enough of the neck to hold a bullet it will chamber, but it fells like ther MAY be the begining of some resistance, I can't really tell on that one.
I compared a vigin case (that I dropped or something - I can't remeber why I marked it) which has .007" runout on the shoulder and the bullet, and chamber FINE,,, to a N sized only round which has essentially NO runout, and will not chamber at all!
The chamber is from a no turn reamer. the shoulder measures XX21" on virgin brass and XX31" on fired brass, BUT the FL die leaves the shoulder at XX29" - XX30" and they work fine. I have also tried setting the bullet back farther - NO LUCK.

PLEASE HELP IF YOU CAN. This is my first Smithed rifle and I had really high hopes for a good introduction to some new shooting disciplines. If this is what it's like I have NO desire to build a "real" BR gun!

PS I dont know what to think!? Is it the chamber/ throat? probably not, but it could be. Is it the N die;? but then why would 1/2 way using the FL die still leave resistance? I just don't know.
PSS For now I am using Hornady dies, including their "universal" 6.5 n sizer. I know these aren't the best, but I wanted to see how things went before commiting to top dollar dies. Clearly they are the first suspect, but the concentricty is fine to great..? shouldn't I be able to find something if the die was bad? I mean, it only touches the neck. If the seater is bad then it should show up in new or FL sized brass also, and/or the concentricity.., but its all fine. I really can't get this one.

 

[RonAKA]

Let me see if I have it straight?

Works OK

- Virgin brass, loaded or not loaded
- Necked only brass, but not loaded
- FL sized brass, loaded or not loaded

Does not work - rubs

- Neck sized only and loaded
- Partial FL sized case -- half way down the neck

Do I have that right? Or, missed anything?

Just a guess, but I'm suspecting that the neck must be too tight. How does your loaded round neck OD compare to the ID of the chamber in the neck? I believe 0.003" clearance is close to minimum.

It would seem that your chamber behind the shoulder is not perfectly concentric with the neck and/or bore. Are you jamming the bullets? If your body is sized then this allows the cartridge to move enough to self align with the neck and bore. If the body is tight fitting (fired without a resize), then the room to self align is gone, and you get the jam. The fact that the necked only case fits without a bullet, but not with a bullet, indicates that the difference in neck OD with and without a bullet is enough to cause the problem. In my gun that is only 0.001". So, that is a very small amount, indicating the neck clearance may be too tight, if that is all it takes to get into trouble.

If this happens to be right, there are a couple of solutions. One just to FL resize. The other would be to neck turn, to restore sufficient clearance.

And by the way, welcome to the forum. I'm sure if I have not guessed right, others will get it figured out for you. Lots of experience here.

 

[gunsandgunsmithing]

What does the neck sized brass measure, from the datum line on the shoulder to the base, compared to a fired piece at the same points? Sounds like the FL die, being adjusted to only neck size, is sizing down the body partially and the shoulder is moving forward, but not being bumped back into place.--Mike Ezell

 

[Vassal]

THanks R.AKA & G. SMITH I appreciate the help...
RAKA, yes that is an accurate account of the situation. I AM jamming the bullets. If i back the bullets out -way out - it does seem to alleviate the problem, perhaps even fix it. I will be doing more testing of that scenario today. But it seems to me that if the Gun was straight that I should be able to load FL & N sized brass to the same length!
GSmith, I am nearly certain that headspace is not an issue. I am using the Hornady guages to read headspace on the brass.

The necks read XX90" on the new brass as well as the N sized brass. If I remember correctly ( I am waiting for a copy of the reamer print) the neck on the diagram was just short of XX95. Thats not real loose but it should be alright,,,-If thats what it really is. I asked Grendel guys about the best "no turn" neck dimension and they said that XX95" was it.

Unfortunately I don't have a neck turning mandrel for 6.5 on hand. I figured I'd wait untill I was able to get some Hornady or European brass.

It seems like we're on the right track. I think that the chamber is relativley tight and a bit crooked; thats a bad combo. I didn't really have the money to be doing this in the first place, and I really don't have the money to fix it! I should have known better than to try this stuff.

 

[Vassal]

Well after some more hair-pulling and thinking I am coming more and more to the conclusion that the chamber is eccentric to the bore. changing the neck thickness does not seem to make any difference. I did notice however, that even when loading new Lapua brass (which has a suprising .008" + of clearence in the shoulder diameter) and backing the OAL off to the point where the bullets do NOT contact the rifling that the same mark appears on one side of the bullet. It is hitting the leade in the bore and skidding forward.

 

[gunsandgunsmithing]

"I tried the FL sizer set to bump the shoulder .002" and those brass work fine. BUT if I size only 1/2 way (sizing the neck half way down with the FL die) it is sticky, in the same way."

The statement above is a recipe for the problem you describe and is why I posted about it above. I know you say it's not a HS issue, but do you mind giving us the actual numbers please?(fired case vs. nk sized case) There simply is not many things that will do this and it should be pretty straightforward to diagnose. Quite honestly, and I may be wrong but, I think you are barking up the wrong tree with the crooked chamber/leade theory. Someone here will be able to steer you in the right direction with enough info.--Mike Ezell

 

[CZ550]

Is there a ending to this story I wanna hear it ?

 

[gamma]

Is there a ending to this story I wanna hear it ?

Yes, how did you get on with this, I too would be interested in the outcome.