New barrel issues 6mmbr

[Panama Evans]

I recently put a new barrel on my wife's and my savage 12f's. We are in the process of breaking them in, and have run into an issue with hers. See using 105 Berger hybrids her bolt closes fine, but when we try 108 Berger target bullets her bolt is extremely hard to close. Bellow are the things I've tried to figure out the problem, and am hoping someone here may have ran into this before, and can help me fix this.
So far I've tried 105 Berger hybrids and no problem even with this bullet touching the lands.
I've tried a full length resized lapua case and a new lapua case. No binding at all and the closes normally.
I've tried backing off the 108's as much as 40 thousandths and still no change
I've checked and triple checked the head space with go and nogo gauges. No problem there.
Now I did replace the head bolt, lug, and barrel nut with cnc machined parts.
So any ideas would be great on what else to look for.
Oh and yes I have sent off an email to the place I had the machine work done on the barrels to see what they say, but I wanted to see what people here might know.

 

[BoydAllen]

Is this a tight neck chamber? Repeat the tight bolt close with the case and bullet completely blacked with a larger marker to see where the point(s) of interference is. Perhaps your neck clearance is marginal with the other bullets and the 108s are just a smidge larger.

 

[Alex Wheeler]

108s have a lot of bearing surface. They will be much farther down the neck. If they are into the neck/shoulder junction and there is a slight doughnut the bullet can push it out causing a tight case.

 

[Panama Evans]

108s have a lot of bearing surface. They will be much farther down the neck. If they are into the neck/shoulder junction and there is a slight doughnut the bullet can push it out causing a tight case.

Wow I didn't even think of that. I tried some new brass and it worked perfect. So from what I can see your 100% on. Well now I'll get to put my new neck turner to use lol. It will be a pain but worth the $ in savings since I have about 700 rounds I sure don't want to toss out.

 

[6MMsteve]

Oh No THE dreadededededed dounut I know how you feel, mine was jelly at least

 

[Alex Wheeler]

Id get a throater and not worry about it.

 

[GSPV]

I *think* that what Alex is saying is that even when/if you take care of the bolt closing issue by turning the necks a smudge, you’d still be hitting the donut with the bearing surface of the 108s. That’s not desirable. Use a throater to lengthen the freebore such that the junction of the bearing surface and boattail is above the donut with some engineering margin thrown in.

You might not have to turn necks at all. Just me, but I’d check to see if I had all the neck clearance that I wanted. Having them too tight causes inconsistencies.

Take it for what it’s worth. I’m just a duffer.

 

[Panama Evans]

I *think* that what Alex is saying is that even when/if you take care of the bolt closing issue by turning the necks a smudge, you’d still be hitting the donut with the bearing surface of the 108s. That’s not desirable. Use a throater to lengthen the freebore such that the junction of the bearing surface and boattail is above the donut with some engineering margin thrown in.

You might not have to turn necks at all. Just me, but I’d check to see if I had all the neck clearance that I wanted. Having them too tight causes inconsistencies.

Take it for what it’s worth. I’m just a duffer.

Good thoughts
Last night I did try some new brass and things were perfect. I did use a sharpie and maybe I was wrong. No donuts, ugh to a long day and being exausted equals me looking foolish.
I'm wondering if it maybe I'm not bumping the shoulders back enough. I remember my die moved on me at on point, as I didn't have it locked down enough. See some brass worked and some didn't. I'm going to do some more testing to sourt this out. And yes only when I'm rested lol.

 

[GSPV]

The donut develops over time as you fire and reload. But, it isn’t consistent.

I was shooting BIB 95 flat base in my 1:10 6BR. Shot like a laser in new brass. As soon as the donut developed...and you could really feel it seating those 95 FB pills...everything went to hades in a hand basket.

I would imagine that the feel would be pretty subtle with a boat tail.

 

[rwj]

...late reply... hope problem is resolved... but if not, check for a donut on the neck ID...

 

[Panama Evans]

...late reply... hope problem is resolved... but if not, check for a donut on the neck ID...

I finally figured it out with help from southern precision rifles where I purchased the barrels. It was a head space issue between the two rifles. It took me 4 tries to get both barrels exactly the same. Now the dreaded donut LOL that started to show up. luckily I purchased a hornady neck turning tool months ago, and that has been another have to have tool.
Unfortunately we were in a rear ending accident, not our fault, and this has set me back horribly being able to spend the time needed to get going for the season. Hopefully these injuries won't keep me down as we all know the hours needed ugh.
Thanks for the reply and thinking of me.

 

[Dusty Stevens]

If theres a donut youll know it when it tries to go past the neck shoulder junction. Itll just stop solid.

 

[GSPV]

Yep. Feels like it runs into a shelf there.

But, there are times when your seating depth with a specific bullet is touching the donut in just a few cases but not touching in most. It can be very frustrating.

Far better to avoid the donut all together.

 

[JFrank]

Yep. Feels like it runs into a shelf there.

But, there are times when your seating depth with a specific bullet is touching the donut in just a few cases but not touching in most. It can be very frustrating.

Far better to avoid the donut all together.

I'll keep an eye out for that, if I missed it on this thread forgive me but from what process does the dreaded donut develop?
Thx
SPJ

 

[Boyd L.]

I'll keep an eye out for that, if I missed it on this thread forgive me but from what process does the dreaded donut develop?
Thx
SPJ

Since brass is malleable it is subject to the forces of firing (& perhaps sizing) and will move forward from the shoulder into the neck. At this junction the sizing of the neck forces this excess into a concentric ring (or doughnut) just inside the base portion of the neck.
Or so it seems.

 

[GSPV]

I’ve never seen the donut, but you can sure feel it if you seat a bullet deep enough. Especially a flat base.

It’s most troublesome when it’s there, just barely there and just a few actually touch the bullet. It can drive you bananas.

 

[JFrank]

Thx
I'm already bananas! So my wife says.
SPJ

 

[nfa1eab]

If using a full length bushing die for sizing, would it be better to outside neck turn, or inside neck ream to remove the donut?

 

[Dusty Stevens]

If using a full length bushing die for sizing, would it be better to outside neck turn, or inside neck ream to remove the donut?

what donut? and if you do get a donut who cares? (if you have the proper freebore to keep the bullet base in the neck it doesnt matter)