Neck clearance on accuracy

[Frankm]

If shooting a bullet that you can’t get any closer to lands than .100 from due to a long throat, will a chamber with tighter neck clearance, say .003 tighter, typically exhibit better accuracy than a looser neck clearances rifle.

(I have 2 different rifles with same throat length and the one with the tighter neck clearance will shoot 1/2 moa vs 1 1/4 moa of the looser neck rifle) Both are jumping a 62 gr Eld vt .100 to the lands.

Be interested in what others have experienced. Thx

 

[ELR LVR]

If shooting a bullet that you can’t get any closer to lands than .100 from due to a long throat, will a chamber with tighter neck clearance, say .003 tighter, typically exhibit better accuracy than a looser neck clearances rifle.

(I have 2 different rifles with same throat length and the one with the tighter neck clearance will shoot 1/2 moa vs 1 1/4 moa of the looser neck rifle) Both are jumping a 62 gr Eld vt .100 to the lands.

Be interested in what others have experienced. Thx

I believe you mean to say the clearance in the freebore
The bullet is not being influenced by the neck clearanced part of the chamber since it is still inside the case
Once it leaves the case the base portion is in the freebore
Which is usually approx .001" - .002" over bullet dia.
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Anyway - in theory - a tighter FREEBORE - will keep the bullet better aligned concentrically
---to the center axis of the bore
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I don't see how a tighter neck will contribute to anything other than how much the brass work hardens
Also - Typically, approx .002 - .003" neck clearance is desired
But some of us cut it down to the gnats ass of maybe having .0005" neck clearance
Whereupon the brass neck expands just barely enough to let go of the bullet then shrinks back down
no resizing needed - this last feature of course depends solely upon how perfectly you turn your brass necks.

 

[Frankm]

No I m meaning neck clearance, in other words if brass expands upon firing and bullet has a long distance to engage lands then would s chamber with tighter neck clearance keep that bullet better aligned with the throat/lands since brass not expanding as much thus creating larger tolerance. ( these both are being shot with neck sizing only)

It would seem to me that theoretically the bullet in the looser chamber would have a little more opportunity to potentially get more out of alignment? Again, thinking out loud. And yes my tighter chamber shots more accurately!!

 

[ELR LVR]

No I m meaning neck clearance, in other words if brass expands upon firing and bullet has a long distance to engage lands then would s chamber with tighter neck clearance keep that bullet better aligned with the throat/lands since brass not expanding as much thus creating larger tolerance. ( these both are being shot with neck sizing only)

It would seem to me that theoretically the bullet in the looser chamber would have a little more opportunity to potentially get more out of alignment? Again, thinking out loud. And yes my tighter chamber shots more accurately!!

Good question then, good thought
Following since I am more inclined to think the freebore dia has more influence
as well as how straight your ammo starts off with in concentricity from the beginning
A tighter neck cannot cure ammo that is out of concentricity so to speak
Yet if it starts off straight - I am not seeing how a tighter neck will help much
since it should stay straight is it enters the freebore and continues on into the rifling.
Also depends on the caliber, the bullet used, how much of the base of the bullet is in the case etc
Such as if you only seat your bullet .050" into the neck vs all the way down at the neck/shoulder jct.
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I will say - a tighter neck should help keep "THE CASE" itself aligned better, hence also the bullet
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I mean i have guns that have like .008" neck clearance and shoot in the .2's
so I am more inclined to the concentricity of the chamber as well as the chambers dimensions keeping the case straight - which itself holds the bullet straight
I'm gonna say it depends more on if your Smith uses a 3 jaw vs a 4 Jaw when doing your barrel work

 

[clowdis]

In testing many rounds of .308 we have found that a neck with .002 clearance shoots no better than a neck with .004 clearance, assuming all else being equal. But this is with the proper throat distance in the chamber too, but mostly still jumping bullets around .020. So I don't think a tighter neck clearance would help you mitigate too long of a throat.

 

[ShtrRdy]

OP -- what is the freebore diameter of that chamber?

 

[Frankm]

Print is at Gunsmith so not sure of diameter. Length is .130 Standard 1.5 degree leade.

Thx

 

[Krogen]

Bruce has the credentials, so when he talks, I listen:

 

[Bronsin]

In my Varmint and other hunting rifles, they all have factory chambers and more clearance than I would prefer, but I found that turning necks for these chambers, even though it made more clearance, would all shoot much better. Is more or less clearance better? I can't say for sure, but the more concentric your rounds and centered they are in the chamber, the better they shoot even when the clearance is generous.

 

[Bill Norris]

In my Varmint and other hunting rifles, they all have factory chambers and more clearance than I would prefer, but I found that turning necks for these chambers, even though it made more clearance, would all shoot much better. Is more or less clearance better? I can't say for sure, but the more concentric your rounds and centered they are in the chamber, the better they shoot even when the clearance is generous.

Some big name F-class and B R shooters claim they get much better accuracy with more neck clearance than with the tighter clearance. From experience with the 30BR I have seen better accuracy with a .330 necked chamber by turning the necks to where my loaded neck rounds are measuring .327 rather than .328 or .3285. After listening to a conversation with Jack Neary concerning the carbon ring showing a pattern of sign-wave up and down the neck rather than a solid ring around the neck being more accurate I did a test and found better accuracy in both my 30BR rifles. (BR & Hunter) Some have said that was not the case with their testing and I'm certain every rifle is different in respect to tuning and accuracy. Again, as mentioned many times on the Forum it pays to test for ourselves to verify what works best for us.

 

[243winxb]

neck clearance

Zero Neck clearance after many firings, when the bushing only sizes 1/2 of the neck.

The .276" is same as chamber neck. No spring back after a while.