6BR & neck tension

[kd4avp]

Tweaking loads on a new rifle. Thinking the neck tension needs to be tighter. Just curious what other 6BR shooters are using as a neck bushing?

 

[LHSmith]

Dependent on your chambers neck diameter, bullet diameter and powder used.

 

[Bill Norris]

.002 always worked well with unturned necks & 6BR.

 

[SKWERLZ]

I’m now running a .265 bushing on a .268 neck.

 

[Mike TackleBerry]

I'm using around .002 and my 6br with Peterson brass is phenomenal!

 

[rwj]

Was using a 0.002” bullet fit, but recently increased to 0.003” and realized a decrease in group size. You’ll have to find what works best for you!

 

[kd4avp]

Thank you all for the feedback.
Was out at the range this morning doing some test loads.
The barrel is a .272 neck with a 1:7.5 twist.
Cases were all 1.55" in length and sized with a 265 bushing.
105 grain Berger BT with 30 gr of Varget.
Only variable was seating depth.
Started out at 2.405" and increased up to 2.430".
5 shot groups at each one.
Was considering going tighter on the bushing but glad I didnt.
Seem to have found a nice combination at the 2.41 to 2.42 seating depth.
All shots were at 100 yds.

 

[DaveTooley]

I err on the side of more since the bullet acts like an expander when seated.

 

[Kracken McGraw]

Thank you all for the feedback.
Was out at the range this morning doing some test loads.
The barrel is a .272 neck with a 1:7.5 twist.
Cases were all 1.55" in length and sized with a 265 bushing.
105 grain Berger BT with 30 gr of Varget.
Only variable was seating depth.
Started out at 2.405" and increased up to 2.430".
5 shot groups at each one.
Was considering going tighter on the bushing but glad I didnt.
Seem to have found a nice combination at the 2.41 to 2.42 seating depth.
All shots were at 100 yds.

Any pressure signs at any of the depths?

 

[kd4avp]

Any pressure signs at any of the depths?

No...none at all. Everything looked great at all depths.

 

[Kracken McGraw]

No...none at all. Everything looked great at all depths.

Good to know then, just getting started in 6br and starting some Lapua brass with a max book charge with 4895. It’s still pretty tame to what this Forum shows, your results will give me something to compare to.
Are you in past touch point with your best group?

 

[kd4avp]

What is the OD of your loaded round at the case neck ?
And bushing test are tougher to evaluate at short range, test again when shooting longer ranges, it won’t change your tune.

I agree. Next on the list is to reach out to 200 & 300 yds. My home range max out at 300. Shooting some UBR matches at 100 yds, thus the test at 100 first. And good point on the OD at the neck. I did write it down when loading these in the shop. Just cant remember what that value was. The bolt closed so nicely on the 2.41s and 2.42s.

 

[kd4avp]

What is the OD of your loaded round at the case neck ?
And bushing test are tougher to evaluate at short range, test again when shooting longer ranges, it won’t change your tune.

Case neck measured .269 with the bullet seated.

 

[Dave M.]

Tweaking loads on a new rifle. Thinking the neck tension needs to be tighter. Just curious what other 6BR shooters are using as a neck bushing?

I’ve found that 3-4.5 thou neck tension shoots best in my Bat M 6 dasher rifle.
Dave

 

[SKWERLZ]

.272 neck
.269 loaded rd
.265 bushing
= .003 clearance
= .004 bullet hold

Got it, thx

That’s basically identical to what I’m running on my 6BRA.

 

[fkimble@charter.net]

Looks to me like all your groups are good, some just have a "pulled" shot in them. Go back and redo they test, being very careful not to pull any shots and if you do is it the shot out of the group? Was the 5th shot the one not in the group?

Frank

 

[6BRA]

That’s basically identical to whim running on my 6BRA.

Closer to.0035 or .003 with springback and whether or not you anneal. Resizing from the outside springs back to outside. Resizing with mandrel / ball springs back to inside. On paper .004. Bushings spring out.

 

[6BRA]

pin guages...are the only sure way to tell...especially if you arent turning necks.

 

[Dave M.]

That’s basically identical to what I’m running on my 6BRA.

Very close to what I’m running too

 

[Dave M.]

I am turning necks and I’m sure that I’m reading the tool correctly. Still no spring back, it doesn’t matter really, I just wouldn’t factor it into any bullet hold or neck sizing considerations.
J

No spring back on brass is a sign of over annealing brass. Essentially, you have turned the brass into a “dead” material similar to lead. One partial solution to this phenomenon is to significantly increase neck “tension” and allow the hoop stress of the brass hold the round. This is the down side to annealing brass. Brass can withstand a fair amount of over annealing before going dead. I’d like more details as to what led up to the brass not having any spring back.
Dave