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

[tim_w]

If the case shoulder to chamber alignment is responsible for centering bullet to bore centerline via firing pin and ejector spring force explain those loads with bullets seated into the lands? Case/load runout and fl sized so no hyper precision bore alignment via case to chamber as the bullet is being engraved into the leade. Seems to me there is enough case tolerance to allow the bullet ogive into the freebore and leade to center to the bore centerline.

While not popular for hunting plenty of wins and even records both in group and score have been set with loads seated into the lands over the yrs. I have trouble believing firing pin force (which is partially absorbed by primer yield) is over powering bullet engraving or neck tension to center off the shoulder cone.

We also have the sub 0.2 agg with sub 0.100 groups and numerous wins including championships set by a texas BR shooter using, of all things, a standard 30-30 cartidge headspacing off the case rim? IIRC, his loads had bullet jump so no support from either end pinning the bullet or case to centerline.

It seems this evidence taken together supports the theory of the freebore/throat/leade being the constant and thus primarily responsible for bullet alignment not the case shoulder. Not denying it might be contributory in some cases.

 

[LDHunter]

If the case shoulder to chamber alignment is responsible for centering bullet to bore centerline via firing pin and ejector spring force explain those loads with bullets seated into the lands? Case/load runout and fl sized so no hyper precision bore alignment via case to chamber as the bullet is being engraved into the leade. Seems to me there is enough case tolerance to allow the bullet ogive into the freebore and leade to center to the bore centerline.

While not popular for hunting plenty of wins and even records both in group and score have been set with loads seated into the lands over the yrs. I have trouble believing firing pin force (which is partially absorbed by primer yield) is over powering bullet engraving or neck tension to center off the shoulder cone.

We also have the sub 0.2 agg with sub 0.100 groups and numerous wins including championships set by a texas BR shooter using, of all things, a standard 30-30 cartidge headspacing off the case rim? IIRC, his loads had bullet jump so no support from either end pinning the bullet or case to centerline.

It seems this evidence taken together supports the theory of the freebore/throat/leade being the constant and thus primarily responsible for bullet alignment not the case shoulder. Not denying it might be contributory in some cases.

GAK!!! You just upset a lot of handloading generally accepted knowledge with that one! LOL

A 30-30 headspacing off the case rim? No jamming into lands? I'm waiting for the non believers to come up with some spin on this one.

I've known quite a few people that spent a small fortune on special handloading equipment and many many tedious hours to proudly walk down range to view their "tiny groups" only to notice that the guy next to them with a factory rifle and sloppily neck sized ammo had smaller groups.

I'm not saying that careful handloading isn't valid but I just can't ignore my two factory 308 Remington PSS rifles (bedded with custom triggers) that both shoot ridiculously tiny groups with Federal GMM 168MK factory ammo. It all just flies in the face of reason. Some of the very best groups I've ever seen were made with rifles set up by people that really knew their stuff and ammo that had NEVER been neck turned or trimmed or or or.... any of that fancy stuff.

If I were competing in target shooting I'd certainly be investing in that equipment and doing all that stuff and like JE Custom says if I were counting on sub 1/4 MOA accuracy every single shot then I'd likely be doing all that tedious case prep but I'm not and it's hard to ignore that 30-30 shooting one hole groups or some of the stuff I see at my local range.

My take in over 50 years of shooting is that the rifle is waaaaaaaay more important than the ammo and that average handloads or exceptional factory ammo in a rifle that might even be just a bedded factory rifle with a good trigger or a good custom rifle will come dang close to that 1/4 MOA reliable grouping.

That seems to be the magic number. Reliable sub 1/4 MOA requires way more patience than I'll ever have. LOL

So.... There you have it. I never bought into so many of the things that many handloaders agonize over as being all that important unless the rifle is properly set up and few rifles are. With modern CNC machining like some of the custom shops have invested in they can now turn out rifles capable of groups that defy imagination.

 

[Savage 12BVSS]

It seems this evidence taken together supports the theory of the freebore/throat/leade being the constant and thus primarily responsible for bullet alignment not the case shoulder. Not denying it might be contributory in some cases.

Hard to argue against, it's my theory as well, it's the biggest reason for the bullet alignment IMHO.

On the accuracy with other shooter's on your gun......I have an unusually accurate 22-250 rifle. Generally mid one's to mid two's depending on how ideal days are at the range. Easy gun to shoot, heavy, very low recoil, very light trigger, I always let anyone shoot it when I'm up at the shop shooting out back on the bench. One young fellow that had little rifle experience sat down and matched my groups with two of his own. The Gunsmith that owns the shop and range has shot my gun multiple times and has a ton of shooting experience, he can also produce groups like I shoot. He loves the gun cause he is a big bore shooter primarily. I have also seen complete loss of accuracy with some that can barely shoot 1".

Its always chamber formed and necksized with match prepped brass. This very long thread that took me about 2 hours to read and digest last night led me to one simple question that few poster's ever mentioned. Take your gun with the load it loves and shoots best, only change the sizing from neck to full length nothing else and see what it tells you. Same day, same load, same shooter, same gun and chamber, and identical conditions. No long arguments or spec sheets or opinions pro or con....just ask the rifle to show you what it likes the most. Within the next week or two I will test it equally with same neck tension and concentricity and report on my results. I was taught to chamber form and neck size and never tried FL sizing for accuracy. You can bet if it helps my groups even a little I will shout it from the rooftops. Accuracy is my thing, not beauty or pedigree, just an obsession with smaller groups. The snow is off the bench and been load working a 7mm-08, will shoot its final rounds tomorrow, Lord willing and the snow don't hit us again

Oh and some will no doubt mention, FL sizing will change the case capacity slightly and hence change pressure slightly. That will be the only result that can't be exactly the same. Dave

 

[Alex Wheeler]

This picture may help with visualizing the freebore diameter's role. The yellow arrow points to the clearance around the bullet in the freebore diameter. It doesnt matter if your jumping or jamming the bullet, there is usually about .0002" clearance here. No matter how you size a case, the bullet will be aligned to the bore to within .0002" or you wont be able to chamber the round. This applies to well built rifles with freebores. You can also see how a very tightly fitted case with even the slightest amount of runout will cause a bind in the freebore. A properly full length sized case gives just enough room to allow the bullet to freely rest in the freebore without bind. And since we can not perfectly control runout, clearance is a good thing. 20 years ago the trend was tighter is better, today its to give things a little room, and the guns are shooting better than ever.

 

[Bart B]

What about rifles whose barrels don't have any freebore?

 

[Alex Wheeler]

That doesnt really apply to LR hunting, or at least it shouldn't. But if we want to talk short range varmint rifles, the best cartridge to look at is the 30BR. Its the only one currently being used in competition with a zero freebore, so it has a good track record and plenty of data. Common practice is to run them in the lands, but some very good shooters jump them. If you could get a hunting rifle to shoot half as good as a 30br you would be doing extremely well.

 

[Mram10us]

crap! Now I need to add a 30br to my switchbarrel setup. Thanks Alex....

 

[Bart B]

I asked about zero freebore because several cartridges popular for long range use have SAAMI chamber specs showing zero freebore. 300 Win Mag is one example.

 

[bigngreen]

I asked about zero freebore because several cartridges popular for long range use have SAAMI chamber specs showing zero freebore. 300 Win Mag is one example.

The zero freebore reamer SUCKS for long range!! Every one I know uses .180-.220 freebore then it's a new ball game!!

 

[Bart B]

Zero freebore in the chamber used to shoot this 20-shot group.

Shots 1 and 2 were first two from a clean barrel.

 

[cajun]

You know as reloaders some times we can get sucked down that rabbit hole of trying to squeeze group size to minuscule levels. But honestly any rifle that will consistently hold 1/2 moa even 3/4 moa is plenty good enough. Even for long range. You would be better served just getting out in the field and shooting. Shoot from field positions. Go shoot when its windy as hell. Learn to read mirage to read the wind. Just go shoot.

 

[tim_w]

Alex,

You have a gift for teaching and laying out data in an easily to be understood way.

 

[tim_w]

Even with zero freebore you still have a leade which acts as a centering alignment cone. Not to mention the bullet dimensions used.

Look at the primary bullet design used in the 30BR when no freebore is cut. They are using short flat base bullets under 1.00" jackets most 7 tangent ogives. Those using longer bullets seem to be adding some freebore. Compare this in contrast to all bullets used in LR shooting. They tend to have much longer bodies with bt and longer necks with hybrid transitional ogives etc. Having freebore in the latter has a greater effect as there is a need. The short bodied 30BR bullets do not have this.

Consider the small groups seen fireforming wildcatts where shoulder angle as well as headspace distance are certainly not in play. A jammed bullet and possibly in concert with a shelf shoulder in the neck base nothing close to the alignment surface area or angle hi of the case shoulder.

It would seem difficult to support a theory that the case shoulder is primarily responsible for the alignment properties of bullet to bore centerline. Yet deny a similar design alignment cone that has direct contact with ogive of the bullet itself is the primary guide in aligning the bullet itself to bore centerline.

I would say this. The shoulder is responsible for centering the case and the throat (freebore & leade) is responsible for aligning the bullet to the bore.

Looking at the relationship I would say the case shoulder is akin to "coarse" alignment of the bullet and throat is "fine" alignment.

It all plays a role. I think it really can be seen as simple as shoulder centers case and throat centers bullet. Ones secondary or primary to the other.

 

[cajun]

Fwiw before I knew to measure shoulder bump I had some dies in 350 rem mag that were pushing the shoulder back .012. Encore break action so no bolt feel to go by. Even with that much slop in the case shoulder dimension the rifle shot 1/2 moa. Of course after 2 firings I had a case separation which led me to buy a comparator to see how much the brass was being sized.