Full Length or Neck Only; What's Best Resizing for Accuracy?

[RD57]

In my rifles and single shot pistol I have found FL sizing with a slight shoulder bump to be more accurate. I think but can't prove that if the case has the ability to center itself on the bolt face and the bullet in the throat you'll have better accuracy. I've tried neck sizing with bushings and without and could not achieve better accuracy. I shot some old LC Match M118 79 rounds at 200 yards three days ago and got a 1/2" group at 200 yards with 5 rounds. Everyone knows that LC Match brass is crap for concentricity in the neck and body, and the headspace is .005" smaller/shorter than the 1980 Rem 700 BDL Varmint I shot it through! Just some food for thought.

 

[birdiemc]

I think but can't prove that if the case has the ability to center itself on the bolt face and the bullet in the throat you'll have better accuracy.

Could this be the reason that savage's shoot so well for such a cheap, poorly machined rifle, the floating bolt head allows the case to be centered in the chamber, essentially equivalent to having the case centered in the bolt face of a non-floating bolt

 

[azarcher10x]

One thing that worked out for me, was going from just a neck sizing die, or fl die, and using a body die and then a neck sizing die. I was occasionally running into extraction problems when only neck sizing. Theory was, after a couple of firings, the cases were were expanded to where the wasn't any spring back from the chamber wall, allowing them to stick. Before anyone says it was over pressure, I checked everything, including comparing to factory loads. Anyway, I picked up a body die, sized the body, and then did the neck separately. No more extraction issue and the groups stayed at .25. I should mention this was on a 300 RUM shooting 168 gr. Barnes at 3400 fps.

 

[richhymas]

I am a "younger" hunter who recently started shooting benchrest with a bunch of old retired guys about 6 months ago. That has been a real eye opener. I am learning a lot about longer range shooting (600 yards) and what impacts great groups at that distance that can't be seen at 100 yards.

I have also learned that these guys have lots of time on their hands to tinker and play with their load. I bought a BR gun that from a guy used after shooting it and realizing that it is a real shooter. For that gun I frequently win best aggregate group, which is the sum of the diameters of four groups of 5 shots each. This seems like a fair way to judge accuracy of a rifle. Anything under 10" is competitive (averaging 2.5" per group with best groups in good conditions just under 2"). This is around 1/3 MOA at 600. Anyone that can consistently shoot 1/4 MOA average 5 shot groups At 600 yards would blow the competition out of the water.

on these forms people are usually siting their very best groups not averages. And usually 3 shots at 100 yards.

getting to my point, most of these techniques are controversial meaning some but not all guns shoot better when x y or z techniques are used, but they do eliminate variables so that when something isn't working you don't have to worry about case weight variability or neck tension or powder charge variability and you can focus on systematically solving the accuracy problem.

in the real world, my experience tells me that many good barrels aren't very fussy and bad barrels won't shoot no matter what you do to your loaded round. There are plenty of cases in the middle where tuning your load just right makes a so so barrel shoot well.

 

[CRS]

I've been reloading for years but just for a hunting load. When I joined this forum, I realized I don't know anything. I want everyone here to know that the wisdom and knowledge you impart on this site is very educational, interesting and very helpful. Every question or problem that's laid before this forum is solved and answered. I don't know of a problem that can't be resolved because of the knowledge and experience you guys have. I for one want all to know it's all appreciated. I will be working on long range shooting in the future. I've certainly found out that 300 yards is not long range. Lol! I don't know where else you can get the knowledge of some of the best gunsmiths in the country along with the wisdom of experience from so many. I'm amazed! Thanks for your help!

 

[Tree Farmer]

I've been doing the same lately. I also quit neck turning as it never really improved accuracy. My runout has improved significantly just by removing the expander ball and using a mandrel for neck tension.

 

[Bart B]

Could this be the reason that savage's shoot so well for such a cheap, poorly machine rifle, the floating bolt head allows the case to be centered in the chamber, essentially equivalent to having the case centered in the bolt face of a non-floating bolt

I don't think so.

The head of a rimless bottleneck case is seldom, if ever, centered on the bolt face when the round fires. Extractors often push case bodies off center against the chamber, Their diameters at that point are smaller than the chamber.

But case position is very repeatable from shot to shot. Accuracy is good. A perfectly straight 308 Win cartridge with its head .001" off center in the chamber will put its bullet tip about .0007" off bore center in the opposite direction. The case pivots on its shoulder in the chamber shoulder.

New 308 Winchester cases with a 3/10 grain spread of IMR4895 under Sierra's 155 grain bullets having .003" runout tested 2.7 inches with 20 shots at 600 yards. In the first match with that new bullet in ammo loaded on two Dillon 1050 progressive's, a couple dozen top ranked long range competitors said it shot about 3 inches at 600. I had the high 4 day aggregate score shooting 600, 800, 900 and 1000 yards using metallic sights.

 

[GregH118]

I am new to reloading I have Redding type s full length sizing die with a .337 neck bushing die when I check diameter of the neck after resizing it will read .335 is this normal

 

[floyd kittrell]

Does one method end up with bullets better centered in the bore when fired? If so, why?

Buy a Sinclair Concentricity gauge , that is what I use , everyone needs it. Most all bullet manufacturers make them , Hornady , etc , etc .

 

[Gcan]

Most target guys FL size now days.

It seems neck sized would line up better because the .010" of slop from case walls to chamber wall would be taken out. It doesn't seem to improve accuracy.

I keep hearing, "the competitive guys full length size". I find the general statement somewhat misleading or overly broad. The statement suggests the comp guys are the same as the guy usually asking the question, as though it is apples to apples. Its not!


Yes, I full length on all hunting and some precision rifles. However, I like the bench folk I know, had a reamer ground to match the dies used or dies made to match the reamer used.

The very idea that you can shoot rounds in just any chamber and then FL size with just any SAAMI die and then get the magic dimensions that produce a combo that shoots bug holes is unrealistic. Although I will concede that uncle Jethro might have an O3-A3 that shoots bugholes.

In the real world the guys who are shooting for excellence have $$$$$ tied up in a rifle/scope/gear. To think they just threw a dart to buy dies is ^*+#~!

we all probably have our own thoughts on max growth tolerances for body to chamber, OA growth, as well as throat growth. I don't know any serious shooter who FL sizes regularly unless they have dies matched to their chambers or chambers matched to their dies. And unless all the stars align, SAAMI dies are not Going to do it. THE difference between a SAAMI FL die and a SAAMI Reamer when you have the max spec on the Chamber and the min spec on the die can be huge in body OD and length growth. Add to the built in differences inherent in the chambering process/set up from one smith to the next and cases can grow .010+ in length from FL SAAMI sizing to shooting and similar body growth. Ain't nobody shooting 1/8 to 1/4 moa or less with cases growing .008 or more (in any direction) with each firing.


I agree with everyone who says Prep-Prep-Prep. Doesn't matter how good your chamber/die relationship is, Garbage in. Garbage out.

 

[5gauss]

THIS... AND to back up what he said, if you don't skim turn and square up the necks to true them, I don't feel either method has any effect on accuracy whatsoever as long as they are sized properly. In fact, there is a faction that believes if you don't prep your brass you are actually better off using small base dies and completely sizing cases back to nearly new factory dimensions. They feel this allows the case to self align in the chamber somewhat, like a factory round. For our purposes (a long range precision rifle) I feel very strongly every round of brass should be fully prepped and sorted. Great loads cannot be either consistent, or duplicated without this step. Leave this step out and you will always be chasing your tail for accuracy. You can find a load that shoots the magic 1/4" group. Go home and load up a bunch and the next group just may be 1-1/4". Doesn't take long to turn, trim and chamfur the necks, ream the flash holes and primer pockets on 100 cases. Doesn't take long to sort them by weight either. I don't sort them until they have been fully prepped.

Yes for target and long range. If you plan to hunt with this process being used, you should run each through the chamber to be sure they will function in the field. You will usually never need that accuracy for hunting purposes. Hit a pie plate at 600 yards consistently and good to go.....or further of course

 

[Opa-lopa]

no advantage to neck size only.. hurts feed reliability, why do it?

 

[Bart B]

SAAMI doesn't have any specs for sizing dies.

It's interesting that most full length sizing dies for rimless bottleneck cartridges have headspace about .005" less than the cartridge's GO headspace gauge

 

[Bart B]

Buy a Sinclair Concentricity gauge , that is what I use , everyone needs it. Most all bullet manufacturers make them , Hornady , etc , etc .

None of them position cartridges to the dial indicator like they are in the chamber.

Depending on their design and setup, they'll indicate different runout values for a given cartridge