Bearing surface depth

[chadrp]

How big of a deal is having the bearing surface below the neck shoulder junction?

I'm curious after hearing Scott talk about it. My factory hornady 6.5cm 140eldm look to be seated with bearing surface below the neck shoulder junction and they have a slight jamb in both of my rifles. As I start to reload and looking at all the things, seating deeper to jump instead of loading to factory length with a slight jamb, it of coarse makes it "worse". Just curious on effects or problems to look for or if I should switch to shorter bullets.

 

[Supersubes]

I don’t have any Hornady in front of me, but the bearing surface would be right down near neck/shoulder. Meaningless in virgin brass. If you had high mileage brass with a donut at the bottom of the neck you could have some issues with consistency. That would be mitigated by using either a mandrel or an expander ball to iron it out. What’s weird is the ammo is jammed in your chamber. What’s up with your chamber?

 

[Steel head]

It’s been a non issue to me.
I have seen donuts on my necked up 243 brass but neck turning and a die change eliminated that years ago.
I do see it useful to To get a slightly better ES but I’m not going the chase Possibly a1-3 FPS advantage.
Certainty something I’d consider whenIF I build the 375 I want eventually.

 

[chadrp]

I don’t have any Hornady in front of me, but the bearing surface would be right down near neck/shoulder. Meaningless in virgin brass. If you had high mineage brass with a donut at the bottom of the neck you could have some issues with consistency. That would be mitigated by using either a mandrel or an expander ball to iron it out. What’s weird is the ammo is jammed in your chamber. What’s up with your chamber?

Ok, thanks. I'm just loading the 2nd firing so I guess I won't get too shook about it but keep an eye on it. I use a mandrel for expanding.

As far as the chamber, you would have to ask the well known Smith on here who i got the prefit from. I'm not saying I was perfect at finding the lands as it was a pain keeping the bolt head pin in place on my Nucleus while doing it, but here is a picture of a factory Hornady 140eldm round from it.

 

[918v]

It looks like plenty of freebore.

 

[Steel head]

It looks like plenty of freebore.

Yep
Riding right on the cut portion of the rifling.

 

[chadrp]

Yep
Riding right on the cut portion of the rifling.

Ok, maybe this a dumb question(s), but are you saying this not a slight jamb? Also how can you tell that there is plenty of freebore?

 

[Steel head]

Ok, maybe this a dumb question(s), but are you saying this not a slight jamb? Also how can you tell that there is plenty of freebore?

Is it sticky on extraction or pushing the bullet back?

 

[chadrp]

Is it sticky on extraction or pushing the bullet back?

I've not noticed it ever being hard to insert or extract a round nor have I ever measured a new round verses inserting and ejecting to see if ita pushing the bullet in deeper. Maybe I just assumed since it was leaving rifling marks on the bullet that its was being jambed.

 

[Steel head]

I've not noticed it ever being hard to insert or extract a round nor have I ever measured a new round verses inserting and ejecting to see if ita pushing the bullet in deeper. Maybe I just assumed since it was leaving rifling marks on the bullet that its was being jambed.

Love rubs.

 

[chadrp]

Here is a photo of a comparison of what I came up with of a factory round on left versus my no touching the lands on the right. Maybe I should go back and do it again as I have a the new generation extractor for my nucleus that doesn't rub on the receiver like the old one did when I did this. I was doing it per the wheeler video but it was a pain trying to keep the pin and bolt head in place and may be the extractor was making it feel like it was still engaged into the lands??

It was much easier to tell when I was finding the lands on my bartlein imact action than when I did it on my Nucleus

 

[Snuby642]

From that picture are you sure those marks are rifling / lands.
The factory round on the left?

 

[chadrp]

From that picture are you sure those marks are rifling / lands.
The factory round on the left?

Yes

 

[morganlamprecht]

was it cut with a saami .199 fb reamer?

if your barrel is cleaned well and thats supposed to be saami spec, it looks like a chamber was cut with a worn/slightly undersize freebore section on the reamer...it shouldnt leave those marks or touch that deep

 

[Snuby642]

So the left cartridge hits the lands aproxamatly. 100 thousands before the right cartridge and they both chamber?

The chamber bolt face to lands lets say is a fixed measurement (less 2500 rounds).

So one of the rounds is jambing .100 thousands?

Wow

 

[chadrp]

was it cut with a saami .199 fb reamer?

if your barrel is cleaned well and thats supposed to be saami spec, it looks like a chamber was cut with a worn/slightly undersize freebore section on the reamer...it shouldnt leave those marks or touch that deep

Yes it is supposed to be sammi spec. I didnt order anything specifically otherwise.

 

[morganlamprecht]

if you scrub it good, and its still doing that...its rubbing where it shouldnt

 

[Snuby642]

Agree 100% with @morganlamprecht
Lands on my rifles leave sets of "teeth marks" evenly spaced not circular mark.

 

[Snuby642]

Will the long cartridge even fit in the magazine?

 

[chadrp]

Agree 100% with @morganlamprecht
Lands on my rifles leave sets of "teeth marks" evenly spaced not circular mark.

The circular marks are not the marks im referring to in referencing jambing . It is the marks on the picture on post #4. The higher circle mark on the tall cartridge is from me turning my seating stem down on the bullet to get a starting seating reference and the lower circle is from spinning the round in my forster compararor. Yes the long round id factory Hornady 140s with plenty of room in my non binder mag.

 

[morganlamprecht]

im talking about the rub marks in post #4 also, not the rings

 

[Snuby642]

Sorry gentlemen, my eyes are getting old.
I can not distinguish any landmarks on any of the 3 bullets.

Not intending to stirr up anything.

I use the crappy little Hornady gauge to find my lands because it is easy
and reasonably a constant with respect to I get the same feel each time.
I estimate a +/- of .005 error max and don't go closer than .010 off anyway.

It looked disproportionately long amount of bearing surface outside of cartridge
for some reason to me.

I apoligise for not getting it, it happens.

 

[chadrp]

It has been awhile since I have ran factory ammo and I guess I was wrong. It isn't really hard to close but there is a slight resistance closing the bolt. When I opened it I did have to smack the handle to the rear to get it to open. Here is the round. It is definitely jambing on factory Hornady 140eldms. Left 5 nice marks and no marker necessary to see them.