How much neck clearance is considered too much? I had a reamer ground with a 0.298" neck. Using Lapua brass it leaves me with 0.003" neck clearance. Going to try some Rem brass and the loaded rd measures 0.290" which will leave me with 0.008" clearance. How much is too much? Thanks krw
Gunsmithing Neck clearance in the chamber
- Thread starter krw
- Start date
Re: Neck clearance in the chamber
.297" is SAAMI but I try to not go larger than .005" over as a rule. Sizing your neck down more than .005" at a time after firing will cause run out and thats an accuracy killer.
For the RP brass in a 260 the .295" Nk is perfect
For the new Lapua brass in a 260 the .297" neck is perfect
I run a .295" Nk in all my personal 260's
.297" is SAAMI but I try to not go larger than .005" over as a rule. Sizing your neck down more than .005" at a time after firing will cause run out and thats an accuracy killer.
For the RP brass in a 260 the .295" Nk is perfect
For the new Lapua brass in a 260 the .297" neck is perfect
I run a .295" Nk in all my personal 260's
Re: Neck clearance in the chamber
I can think of little practical reason for such tight neck clearance.
So that you don't overwork your brass? Please... We're talking about a few thou less "working".
For proper/better cartridge alignment in the chamber? Somehow, factory rifles with a LOT of empty real estate surrounding the neck shoot very, very well.
With little clearance, you lose the tolerance of having some dirt/debris in the chamber and still have nice easy chambering. You run the risk of not getting a clean bullet release from the case. You will be required to follow excellent brass prep protocol, as even a tiny burr left over from trimming may prevent chambering. You'll have to be careful to check any ammo you didn't load and QC personally, before using it.
I know BR folks sometimes run so little clearance they don't even have to resize a case (even neck sizing!) to reload/reuse it.
I think, unless you're doing something really specialized, .003/side is a minimum, and I wouldn't be the least bit sad at .005/side.
I can think of little practical reason for such tight neck clearance.
So that you don't overwork your brass? Please... We're talking about a few thou less "working".
For proper/better cartridge alignment in the chamber? Somehow, factory rifles with a LOT of empty real estate surrounding the neck shoot very, very well.
With little clearance, you lose the tolerance of having some dirt/debris in the chamber and still have nice easy chambering. You run the risk of not getting a clean bullet release from the case. You will be required to follow excellent brass prep protocol, as even a tiny burr left over from trimming may prevent chambering. You'll have to be careful to check any ammo you didn't load and QC personally, before using it.
I know BR folks sometimes run so little clearance they don't even have to resize a case (even neck sizing!) to reload/reuse it.
I think, unless you're doing something really specialized, .003/side is a minimum, and I wouldn't be the least bit sad at .005/side.
Re: Neck clearance in the chamber
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">With little clearance, you lose the tolerance of having some dirt/debris in the chamber and still have nice easy chambering. You run the risk of not getting a clean bullet release from the case. You will be required to follow excellent brass prep protocol, as even a tiny burr left over from trimming may prevent chambering. You'll have to be careful to check any ammo you didn't load and QC personally, before using it.</div></div>
Agreed. For a "tactical" or "field grade" rifle, function must come first. I've had a couple occurrences of difficulty due to an excessively tight neck combined with a minor variation in ammo, and it is very frustrating.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I know BR folks sometimes run so little clearance they don't even have to resize a case (even neck sizing!) to reload/reuse it.</div></div>
Sounds like a totally awesome time-saving tip!
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">With little clearance, you lose the tolerance of having some dirt/debris in the chamber and still have nice easy chambering. You run the risk of not getting a clean bullet release from the case. You will be required to follow excellent brass prep protocol, as even a tiny burr left over from trimming may prevent chambering. You'll have to be careful to check any ammo you didn't load and QC personally, before using it.</div></div>
Agreed. For a "tactical" or "field grade" rifle, function must come first. I've had a couple occurrences of difficulty due to an excessively tight neck combined with a minor variation in ammo, and it is very frustrating.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I know BR folks sometimes run so little clearance they don't even have to resize a case (even neck sizing!) to reload/reuse it.</div></div>
Sounds like a totally awesome time-saving tip!
Re: Neck clearance in the chamber
When you guys talk about clearance in necks, please specify if you are talking total diameter clearance, or clearance per side.
0.003" PER SIDE is a good place to be on a field gun.
Benchrest will run down to 0.001" or even less PER SIDE.
Factory guns designed to shoot factory ammo will often have up to 0.005" or more of clearance PER SIDE.
When you guys talk about clearance in necks, please specify if you are talking total diameter clearance, or clearance per side.
0.003" PER SIDE is a good place to be on a field gun.
Benchrest will run down to 0.001" or even less PER SIDE.
Factory guns designed to shoot factory ammo will often have up to 0.005" or more of clearance PER SIDE.
Re: Neck clearance in the chamber
For a practical field gun, I see little benefit to using non-SAAMI chamber specs.
While such practice makes serious concentricity efforts less helpful, the basic compromses built into the SAAMI spec just simplify handloading and reduce the number of potential problems to the point where they basically become non-issues.
I believe the factories utilize the SAAMI chamber spec as a way of forestalling liability issues, but those issues are a good reason for SAAMI specs, especially when one contemplates transferring a firearm. The same reasoning also makes practical sense, despite its initial conflicts with concentricity efforts..
All is not lost, however. I do partial length neck rsizing, where a rearward portion of the case neck remains at its expanded diameter. This serves to better center the case neck in the chamber, while managing to retain the neck expansion clearance adequately for the forward portion of the neck.
I mainly use this as a quasi-management technique to add some measure of control over neck tension. How much neck length remains expanded, and how much grips the bullet is a ratio which can be adjusted to either aid retenion for feeding or reduce tension for accuracy with single-fed rounds.
Either way, as long as some rearward portion of the case neck remains unresized, case concentricity within the chamber neck is enhanced.
Greg
For a practical field gun, I see little benefit to using non-SAAMI chamber specs.
While such practice makes serious concentricity efforts less helpful, the basic compromses built into the SAAMI spec just simplify handloading and reduce the number of potential problems to the point where they basically become non-issues.
I believe the factories utilize the SAAMI chamber spec as a way of forestalling liability issues, but those issues are a good reason for SAAMI specs, especially when one contemplates transferring a firearm. The same reasoning also makes practical sense, despite its initial conflicts with concentricity efforts..
All is not lost, however. I do partial length neck rsizing, where a rearward portion of the case neck remains at its expanded diameter. This serves to better center the case neck in the chamber, while managing to retain the neck expansion clearance adequately for the forward portion of the neck.
I mainly use this as a quasi-management technique to add some measure of control over neck tension. How much neck length remains expanded, and how much grips the bullet is a ratio which can be adjusted to either aid retenion for feeding or reduce tension for accuracy with single-fed rounds.
Either way, as long as some rearward portion of the case neck remains unresized, case concentricity within the chamber neck is enhanced.
Greg
Re: Neck clearance in the chamber
I like .002 to .003 per side. Skim turning the necks and using bushing dies for .003 to .004 neck tension makes straight ammo for me. Straight ammo makes for good shooting.
I like .002 to .003 per side. Skim turning the necks and using bushing dies for .003 to .004 neck tension makes straight ammo for me. Straight ammo makes for good shooting.
Re: Neck clearance in the chamber
Here is some recent (as in the last 2 weeks) experience in regard to neck clearance in my 284.
Beware of neck clearance in your 284s, fellas!
My chamber neck diameter is .317". Fired brass measures .315-.316". I've been seeing a lot of fliers, to the point I was questioning if I can even shoot. Also, I've been noticing weird pressure. My initial ladders showed 55gr H4350 to be stout but OK. However, throughout load development, I'll sometimes see signs of pressure with nearly any reasonable charge, from 50gr and up. Sometimes pressure signs were there, sometimes not. Accuracy was poor. I'd stack a few, then drop a shot 3" away (200 yards). I was also seeing poor extreme spread and standard deviation...like ES of 70fps, SD of 15-20...
The necks on my loaded cartridges measure ~.313", which *seemed* like plenty of clearance, but NOT being able to drop a bullet through a fired case bothered me, so I neck turned to achieve .003-.0035/side neck clearance.
Problem solved. The pressure swings are gone, ES of a 10-shot group is 10fps, and SD is 2fps. The rifle HAMMERS. Ive gotten a 1/2" 10 shot group @ 200 yards, but I bet that the rifle can do better
Here is some recent (as in the last 2 weeks) experience in regard to neck clearance in my 284.
Beware of neck clearance in your 284s, fellas!
My chamber neck diameter is .317". Fired brass measures .315-.316". I've been seeing a lot of fliers, to the point I was questioning if I can even shoot. Also, I've been noticing weird pressure. My initial ladders showed 55gr H4350 to be stout but OK. However, throughout load development, I'll sometimes see signs of pressure with nearly any reasonable charge, from 50gr and up. Sometimes pressure signs were there, sometimes not. Accuracy was poor. I'd stack a few, then drop a shot 3" away (200 yards). I was also seeing poor extreme spread and standard deviation...like ES of 70fps, SD of 15-20...
The necks on my loaded cartridges measure ~.313", which *seemed* like plenty of clearance, but NOT being able to drop a bullet through a fired case bothered me, so I neck turned to achieve .003-.0035/side neck clearance.
Problem solved. The pressure swings are gone, ES of a 10-shot group is 10fps, and SD is 2fps. The rifle HAMMERS. Ive gotten a 1/2" 10 shot group @ 200 yards, but I bet that the rifle can do better
Re: Neck clearance in the chamber
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Edds</div><div class="ubbcode-body">How did you measure your chamber neck diameter? </div></div>
I haven't directly...
I ordered a reamer with a .317" neck (which was suggested to me by Dave Kiff).
I mic'd the neck of the reamer.
My fired brass neck's measure ~.315-.316, which is a reasonable number including springback, for a .317" chamber neck.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Edds</div><div class="ubbcode-body">How did you measure your chamber neck diameter? </div></div>
I haven't directly...
I ordered a reamer with a .317" neck (which was suggested to me by Dave Kiff).
I mic'd the neck of the reamer.
My fired brass neck's measure ~.315-.316, which is a reasonable number including springback, for a .317" chamber neck.
