Neck Tension vs Accuracy

[yukonal]

If the bullet from the handload is seated to touch, or into the lands, does differences in neck tension really make a difference?

Example:

Trimming a new bunch of brass...for whatever reason...some cases were trimmed .005" shorter than the intended length, could the slight difference in neck length...read "neck tension", cause a difference in POI from the loaded rounds, where the bullet is seated to touch the lands?

If the bullets are seated to touch, or into the lands, how can slight differences in neck tension make a difference? Seems to me the bullet doesn't have to jump, it's already there...

 

[Lapua40X]

IMO, if it makes any difference at all you won't be able to single it out with any certainty as a causation fractor on the target. Slight variations in your hold on the rifle (which are never truly consistent from shot to shot) are more likely to affect accuracy than the neck tension you describe.

 

[searcher]

I think that when the bullet is into contact with the lands - the amount of tension on the bullet is generally less important UNLESS your load requires that the bullet be firmly engraved into the lands - for which you may need "more" tension. If loading into the lands, say, .015", and you have extremely light tension, your bullet , once contacting the lands, will merely slide into the case as the bolt is closed - resullting in a "soft-seat" as is often called. In general, the idea is for your bullet to be held in steady position (wherever that may be) until you have ignition. If jambing, you may need more than off the lands - depending upon the amount of jam you want.

Regarding taking off the length and any resulting point of impact change, changing ANYTHING on a load "can" have a minimal change on P.O.I. and changing tension on the bullet will certainly do it. That said, I normally don't trim my cases after each (or many) firings and have not lost my tune by doing so. They may grow .003 to .006 before I trim. I have never noticed point of impact changes due to just the trim. Either I never noticed or they are too small to notice. Don't know. I certainly wouldn't worry about clipping .005" undersize. It sure won't affect the cases ability to hold your bullet - and I doubt you will see any P.O.I. change.

 

[Alex Wheeler]

I learned this season that neck tension is every bit as critical as seating depth or powder charge. Test it like you would anything else. The gun will want "x", go too far either way and things get ugly. As far as .005" variation in trimming, I don't think you'll notice that.

 

[6BRinNZ]

I learned this season that neck tension is every bit as critical as seating depth or powder charge. Test it like you would anything else. The gun will want "x", go too far either way and things get ugly. As far as .005" variation in trimming, I don't think you'll notice that.

zfast - how "tight" do you go in your testing i.e. do you stay in a .001- .003" or do you go out to say .004/5?

 

[Erik Cortina]

Neck tension is one of the biggest factors in accuracy. Jamming bullets does not give you a free lunch because bullets with light neck tension will jam less than bullets with heavy neck tension, therefore having different base to ogive measurements when chambered.

 

[mikecr]

It's hard to imagine 5thou of trim length changing either bullet grip, or seating force, enough to matter.
Seems likely lost to the fog of ballistics.

 

[lpreddick]

a good question. i asked the same when i went from jumping to jamming. i believe strongly that neck tension or bullet grip that has to be overcome before the neck releases the bullet, increases with time after the bullet is seated. we have discussed/argued the phenomenon of "cold bonding" between bullet and neck ad. nauseum...it is real. a bullet loaded today, jumping, will very often shoot to a different poi in 6 months than it does on day one, and the group can change. seating into the lands seems to overcome this observation. "just touching" is risky in that the bullet may not touch all lands the same, esp if the gun has been shot a lot...land erosion. .020 into the lands with .002 "neck tension",meaning the neck is expanded .002 from sizing to seating measurement over the pressure ring(flat base bullet) or bearing surface on boatails will usually keep the bullet from "self seating". the pressure needed to move the bullet seated .020 into the lands FAR exceeds that needed to move same bullet if jumped, i.e. breaking neck tension/grip. therefore i suspect slight variations in neck grip ,either from "cold bonding" or neck length differences has little, if any, effect on inside case pressure needed to move the bullet when seated well into the lands.

 

[1shot]

Just to add to what others have said, I recently competed in the "Bob Wright" the Ohio state 1,000 championship. The match is 5 strings prone at 1K fired over two days,with 3 scope matches and two iron sights only matches. On two separate occasions, I had bullets had moved out from their original seating position and I had to re-seat them by closing the bolt. I don't know what the jam measurement was, but I sure it was well in excess of my normal seating depth of +.012 to touch. Before touching off the shot I mentally said "well, I wonder where this one will go". Much to my surprise and happiness both shots were X's. So, I'm not sure if bullet grip or jamming has any pronounced effect or not, or if I just got lucky on both of those shots but it didn'y hurt my score. BTW, I won the Master class shooting a 974-35x and was second overall to the match winner, a HM.
I hope this helps,
Lloyd

 

[artbosco]

I've seen both neck tension increased by .001" and seating depth increased by .001" make a world of difference. Sometimes it doesn't take much to improve accuracy significantly. Fine tuning a load with a F/L bushing die and adjusting seating depth can really shrink group size.

 

[FeMan]

............ I'm not sure if ....... I just got lucky........BTW, I won the Master class shooting a 974-35x and was second overall to the match winner, a HM.

I would say it was a combination of 100% luck and 100% skill Congratulations on the great shooting!

 

[1shot]

I suppose I should have been a little more clear. I agree 100% with what Outdoorsman said. When a rifle isn't shooting to the potential that I believe it is capable of, I will play with both seating depth and neck tension. That said I only change one variable at a time and determine which is making the most pronounced difference. Changing two or more variables will have you chasing your tail as well as making you bat poo crazy.
I hope this clarifies my last post.
Lloyd

 

[yukonal]

It's hard to imagine 5thou of trim length changing either bullet grip, or seating force, enough to matter.
Seems likely lost to the fog of ballistics.

Lot of good answers. Thank you, guys.

This is my opinion and observation...but then I've only been shooting and reloading for 28 years. I am wondering if there is conclusive evidence otherwise.

If a bullet is in the lands...touching or otherwise, any amount of neck tension shouldn't change the outcome of the POI. Should it? I am asking...because I don't have any facts, just my opinion.

Thanks again guys, for taking the time to reply.

 

[searcher]

The paradox of your question is that is takes more neck tension to get to different depths of bullet engraving position. That aside - and once you are there - wherever it is, - I would think any change in an amount of normal tension ranges would not make a difference at that point - when jambed. If not in the lands, tension amount can make a HUGE difference.

 

[Alex Wheeler]

Neck tension always matters. It effects when the bullet starts to move. Touch, .010" in, .020" in, neck tension is still going to be what is holding the bullet back. Now, when you get to jam, then the rifling is what is holding the bullet back, but you can't get the same jam length with different neck tensions so once again it matters. If you aint turning necks to +/- .0001" and keeping very consistent tension you are leaving some accuracy on the table IMO.
Alex

 

[SF-Guy]

okay, great questions. neck tension is a way of allowing the lands in the barrel to "push" back the round which might be soft-seated.

I go with IN or OUT of the lands. I don't "touch" simply because with the tolerance in loading instruments if one touches and the next one does not...they will print at two elevations on the target. they should all be uniformly "into" the lands or a little OFF the lands. IMO

using a good chronograph and watching the impact downrange you will come to the same conclusion.
Another reason to adjust neck tension depends on whether you load into the chamber one at a time (slow fire) or load from a magazine (rapid fire, etc). when loading from a magazine the neck tension needs to be firm enough to keep the bullets from moving about.

 

[Juma]

For what it is worth we use an M Die to seat Barnes projectiles i.e. tsx & ttsx. The seating op is so smooth because the long shank of the monolithic Barnes is not shaved as it is seated.Groups have dropped dramatically.These are on hunting rifles.

 

[dkhunt14]

I agree with TOM and Alex that tension is critical. Some guns are more critical then others. I also like to shoot the VLD's 10 to 15 in and I believe both of these help reduce vertical at 1000 yards. The more tension helps keep the bullet more consistent when going into the rifling. Plus the more tension helps if you have to open the bolt on a live round. Never had a bullet stay in the barrel. Matt

 

[johara1]

I too believe that uniform neck tension is critical to low ES and to vertical at 1000yds. Seating depth, powder charge must be held to the same tolerance as nt. I just ran a series of test and used .002, .003 and .004 all were held with in 2 lbs. seating pressure all had single digit ES but with the Spencer bullets only one shoot small …….. jim

 

[Drop Port]

I agree with TOM and Alex that tension is critical. Some guns are more critical then others. I also like to shoot the VLD's 10 to 15 in and I believe both of these help reduce vertical at 1000 yards. The more tension helps keep the bullet more consistent when going into the rifling. Plus the more tension helps if you have to open the bolt on a live round. Never had a bullet stay in the barrel. Matt

When you say more tension? I curious about what numbers you are talking, how much tension or how high have you gone to achieve the results you were looking for.

I was out load testing yesterday due to new dies and lot of powder. I found that my 6.5x47 definitely likes more than .002" neck tension. When I tried dropping down to .002 groups doubled. Loads area .002 off the lands.