Interference fit between bullet body and case neck

50wt

50wt

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Answers are out there but want to hear from some people on here.


What will increasing the interference fit between the neck and bullet result in? Standard seems to be about .002 interference but say you want to resize to .004 under.

will you achieve better sd's ? More speed? Early pressure signs with an ordinarily safe load ?
 
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Jacketed bullets in a rifle. Good point about the swaging. I think the jacket is thick enough but ill measure some pulled bullets from some .003 under brass.
 
Too many variables to answer simply but at minimum I’d expect your initial pressure spike to increase some amount. Velocity may accompany that spike.
 
Im curious , at what point does under sizing the neck have a negative impact
Like forcing the bullet into a overly tight neck will it cause a increase in bullets not seating straight ?

Theres bench rest shooters who use light neck tension and having bullet touch the lands.

I also think will a tighter neck tension retain that tight fit or will the brass just be sized back a touch when seating a bullet.

I never got to that point , my stint into “precision” rifle shooting ended once I had kids. I bought a palmer rifle got it zeroed at 200 yards and never made it past that point. Sold that set up
 
I thought this thread would be about guitar setup. Or maybe backrubs.

Nevermind.
 
Precision rifle (or anything Precision) is about removing variability.
Neck tension keeps the bullet positioned solidly in an auto loader and helps get the pressure up earlier in the burn to achieve a good ignition.
But neck tension varies even if you neck turn and anneal. So precision shooters work to minimize both the variability in the tension and the level of tension. In a bolt action the neck tension is much less important since loading into the chamber is not a violent process. And not being tied to a magazine length, COAL can be set to put the bullet nearly on the lands. So now you can make sure the bullet starts traveling straight as it is immediately guided on the lands, and the bullet is pushed into the lands as pressure builds rather than slamming into them.
High neck tension also effects the shoulder during seating - high tension requires a heavier undersizing of the neck during sizing work hardening the neck followed by dragging the decapping rod back through to set the neck size which is done with an unsupported shoulder.
So if you use very low neck tension and seat at the lands to create the initial pressure spike for solid ignition, the residual uncontrolable variability in the neck tension becomes more insignificant as it's a small percentage of a small problem.
All valid and great theory with science supporting it - but I can't shoot well enough to take advantage of that level of precision anyway 😕
 
At some point you will be over-working the brass, causing early failure and potentially some inconsistent velocity. Will .004" do it? I don't know. As someone mentioned, the benchrest guys will probably have answers. These are the guys trying for sub 1/4 MOA groups.

It's been a long time, but when I tried different neck tensions via LE Wilson arbor press dies, the tightest I tried did cause the SD's / ES's to increase. I'd have to find the bushing to see what the tension was. With good brass, annealing, halfway decent 'match' dies, some load development, and most importantly a good barrel- I can achieve 1/2 to 1 MOA results which works for me. ES can be ~11 to 13 fps and SD's in the single digits. IIRC, the higher neck tension was causing ES's in the mid 20's to low 30's with Benchmark powder in .223 cal.
 
Got to test some stuff. Everything else being the same , necks that were .0035 under yielded sd's that were half of what the .002 under brass provided.
 
50wt said:
no sir. I may try a .004 under expander though. I think controlling the id may be easier than measuring a crimp. using gage pins, the neck id seems to be pretty consistent, which can also be felt when seating .
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I kept telling myself I was going to set up a single stage press with the torque wrench adapter. And use the crimp dye the one that just crimp the neck. Use the Lee crimp dye on reduced cast loads for rifles especially ones that have a good amount of free travel before the bullet hits the lands.
Although I don’t think I’m using the crimp dye as Richard Lee intended. I adjusted it to the point where it just kisses the crimp in. I’d have to go over and do some more testing, but I definitely had better groupings and a lot less off sounding shots and flyers when I crimp
It’s been a good while since I lost through it, but I’m pretty sure Richard Lee first edition reloading has a good amount of info on neck, tension, and crimping
 
Of all the things I worry about when trying to shoot an X at 600 yds, neck tension/crimp falls somewhere below what the factory worker had for lunch the day he was manning the machine when my batch of brass, bullets, primers, etc was made.
 
PatMcD said:
Of all the things I worry about when trying to shoot an X at 600 yds, neck tension/crimp falls somewhere below what the factory worker had for lunch the day he was manning the machine when my batch of brass, bullets, primers, etc was made.
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I have long passed X ring , in the black is my end goal at 53 and very little practice
Heck I have not been to 600 yds in YEARS
Last time was a any rifle any sights at 600 and I was doing fine and the hit the frame 2x ? It was hot and nasty and I lost interest stopped shooting for the day.
 
PatMcD said:
Don't give up hope. I'm 4 years older than you, and this was my last string of 20 at 600 during the Downeast Regional a couple of weeks ago. View attachment 932458
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Still on irons or scope, i was teying to snag a SR optic , buy cash has been tight
Got a good hit on auto and home insurance
I just cant keep up with the increases.
 
mac1911 said:
Still on irons or scope, i was teying to snag a SR optic , buy cash has been tight
Got a good hit on auto and home insurance
I just cant keep up with the increases.
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The Sightron S-Tac 1-4.5x is a solid scope from short money ($285 when on sale).
 
PatMcD said:
Of all the things I worry about when trying to shoot an X at 600 yds, neck tension/crimp falls somewhere below what the factory worker had for lunch the day he was manning the machine when my batch of brass, bullets, primers, etc was made.
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If your buying factory ammo, sure. If you reload, can you explain why you dont worry about this?
 
50wt said:
If your buying factory ammo, sure. If you reload, can you explain why you dont worry about this.
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I think he's saying, in terms of consistency, the effect of neck tension variability tends to contribute less uncertainty than may be induced by other reloading steps or component choices. Or, improvement in the uncertainty may be overwhelmed by other factors in the process in conjunction with the tune.

At some point, doing just enough in order to get the results and consistency that you need for your application will help prevent the insanity induced while chasing those nodes.

With that said, I have seen an improvement on ES when tuning and managing neck tension. This is when trying to chase an ES 10 or less. Annealing is part of this and, for my set-up, it was less neck tension that seemed to decrease ES. I say 'seems', because there are likely incremental improvements overall in the reloading process simply due to repetition along with the unique tuning factors for my particular platform and component choices.

This guy, an F-Class competitor, does a nice job of testing such effects on his channel:


View: https://youtu.be/e_RfzthBUKo?si=oaWkw9DanZggO3SO


And, Eric Cortina's take on tuning loads.


View: https://www.youtube.com/watch?v=6VEMZJYovMA
 
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PatMcD said:
The Sightron S-Tac 1-4.5x is a solid scope from short money ($285 when on sale).
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Sorry for the thread drift
You keep itvon 4.5x all the time ? Really like the concept of that reticle
Like my Redfield match sights , front globe.
 
mac1911 said:
Sorry for the thread drift
You keep itvon 4.5x all the time ? Really like the concept of that reticle
Like my Redfield match sights , front globe.
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I do. The dot is small at 1/2 moa, but the outer ring works great (just like match iron sights) at 600 at the end of the match when your eyes get tired.
 
50wt said:
If your buying factory ammo, sure. If you reload, can you explain why you dont worry about this?
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The first stage on my 650 is a mandrel. That just make sure all the necks are the same.
The target we shoot at is huge (x-ring is 6"). If your game is benchrest or F-class, maybe experimenting with neck tension is worth the time?
 
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