Bart B. ... I'm starting to see the light ... full-length case sizing IS better!

[MCMXI]

Due to Bart B.'s extensive posts on the benefits of full-length case sizing, I've started to experiment with new vs. neck-sized cases. The results thus far seem to corroborate Bart's position that full-length sizing is the way to go. It's early days but groups shot with my .308 Win over the last few weeks seem to indicate that my neck-sized cases aren't helping accuracy with 0.662" and 0.786" 5-shot groups at 100 yards. Compare that to 0.242" and 0.482" 5-shot groups with new brass and the same two loads.

100 yards, prone with bipod and rear Triad Tactical bag (all groups shot "round-robin" as part of load development)
New Lapua cases, 42.9gr Reloder 15, 5-shot group = 0.242"
New Lapua cases, 43.2gr of Reloder 15, 5-shot group = 0.482"
Once fired, neck-sized Lapua cases, 43.2gr Reloder 15, 5-shot group = 0.662"
Once fired, neck-sized Lapua cases, 43.2gr Reloder 15, 5-shot group = 0.786"

There is a question in here somewhere. Due to these results, I've decided to use 60 new cases for this weekend's match so have begun sorting 200 Lapua cases. I figured I'd sort them by "headspace" and have found that they vary from SAAMI - 0.002" to SAAMI + 0.001". Since I don't usually full-length size or even bump case shoulders back using a body die very often, what sort of consistency (headspace) are you able to maintain when sizing with a full-length or body die? If Lapua cases from the same lot vary by 0.003", can we expect to do better? I recently bought a set of five .308 Win Redding competition shell holders with 0.000", 0.002", 0.004", 0.006", 0.008" and 0.010" increments to help with consistent sizing in terms of headspacing but have yet to use them. Ultimately, I'm most likely going to neck-size fired cases and then bump the shoulders back with a body die. This is how I resize cases for my .223 that I use in matches and I'm happy with the results. I haven't made much of an effort to check the headspace consistency of .223 cases prepared that way but it's probably not that good. Me and .223 don't get along that well.

Thanks.

 

[USSR]

...I'm most likely going to neck-size fired cases and then bump the shoulders back with a body die.

That's what I do, although I use the body die first, then the NS die.

Don

 

[essayons21]

Is this a bolt-gun or an autoloader?

I've done similar tests with my bolt-gun, and found neck-sizing produces optimum accuracy vs. full-length. I use once fired Black Hills Match brass, which I believe in Winchester in origin, so I don't know the difference between neck-sized and new brass.

If F/L works best in your gun, that is outstanding. You get the added bonus of more reliable feeding as well. I would like to see an extension of this test, with perhaps 20-30 rounds of each. Three 5-shot groups, while showing an interesting trend, isn't exactly conclusive.

 

[MCMXI]

That's what I do, although I use the body die first, then the NS die.

I know .... I pay attention to what you do and say.

Three questions though ... any reason for the order, how much do you bump the shoulder back, and how consistent are your headspace dimensions after using the body die?

Thanks,

 

[MCMXI]

Is this a bolt-gun or an autoloader?

Bolt action.

If F/L works best in your gun, that is outstanding. Three 5-shot groups, while showing an interesting trend, isn't exactly conclusive.

My initial results compare new Lapua brass to once-fired/neck-sized brass and once-fired (different chamber)/neck-sized/shoulder bumped back to fit in new chamber brass. I'm making the assumption that new brass is the same as full-length sized brass. I realize that FOUR five shot groups comparing new and once-fired brass is just a start, but since all groups were shot "round-robin" as part of at least 40 shot strings, the evidence is compelling.

 

[fguffey]

full length case sizing is better than what? A feeler gage?

I am a fan of cutting down on all that case travel. not sure why it has to be full length sizing or neck sizing with nothing in between, I do not go to the range with a rifle that I have not check for head space, I do not fire a case first then check the effect head space had on the case, I check head space first then size cases for the chamber with a full length sizer die that is adjusted with a feeler gage.

Things to remember by Bart B.

Folks should remember that rimless bottleneck rounds always have their shoulder hard against the chamber shoulder when they're fired. The round's driven hard against the chamber shoulder by the firing pin's impact. The case shoulder stays there as the primer detonates, burns the powder, pressure builds up and pushes the back part of the case back until the head stops against the bolt face just before peak pressure's reached



I do not agree with Bart B's explination of the sequence of events from the firing pin hitting the primer to to the bullet leaving the case starting with "Folks should remember", The part that 'folks' remember is 'the pressure builds up and pushes the back part of the case back until the head stops against the bolt face just before peak pressure's reached', folks remember that all that case travel causes case head seperation, if the object is to get a lot of miles out of each case possible full length sizing is not recommended.



Accuracy, full length sizing and bench resters with cases that have been fired with full loads 50 times, that is a conflicting statment, I do not know the difference between cases that have been fired 50 times and cases that shooters claim they fired 50 times but cases I personaly know of that have been fired fewer times had difficulty standing up straight because the case was to thin to support the weight.

F. Guffey

 

[USSR]

... any reason for the order, how much do you bump the shoulder back, and how consistent are your headspace dimensions after using the body die?

1858,

My reasoning for using the body die prior to sizing the neck is that the cartridge case is completely supported and aligned with the sizing bushing when the neck sizing process begins. The body die does not resize the body in relation to the neck. In practical terms, it may not matter, but this is my reasoning. I set up my body die using a case fired in another rifle that would not fit the chamber of my FN SPR. I lowered the die until it produced a case that would just close without resistance in the chamber. Since my other .308 rifle is a FAL with a more generous chamber, I just leave the body die set as it is. Never really checked for consistency data.

Don

 

[Marlin 45 carbine]

do you center the die in the press? I do, leave the die a little loose and run a sized case into it then tighten down. I also use an o-ring as a shellholder retainer which allows it to float a bit. it seems to help a bit.
that Lapua brass is good stuff.

 

[MCMXI]

Here are the results from 200 new Lapua cases compared to a SAAMI standard and measured using a Redding Instant Indicator Case Comparator.

Difference between case and SAAMI standard in thousandths of an inch.

-3.0 (7)
-2.5 (3)
-2.0 (46)
-1.5 (25)
-1.0 (53)
-0.5 (24)
0.0 (27)
0.5 (8)
1.0 (5)
1.5 (2)

So the majority of the cases (175/200) are between SAAMI - 0.002" and SAAMI + 0.000". I'm going to shoot four 5-shot groups at 200 yards in tomorrow's match (at different targets) using cases that are -0.003", -0.002", -0.001" and 0.000" compared to the SAAMI standard. I'm wondering if I'll see a significant difference in group sizes between the four different cases all with the same 43.2gr of Reloder 15. I'm going to shoot 22 rounds at 600 yards using new -0.002" cases (compared to SAAMI). If I do see some meaningful differences, this may tell me how much I need to bump the shoulder back on fired cases. If I don't see much difference between the groups, this may tell me that I don't need to spend a lot of time trying to get the same shoulder setback for every case.

do you center the die in the press?

Not really ... but this is something that I've been reading about recently and will have to look into. All of my dies are Redding and so far they seem to produce uniform cases as measured with a V-block and dial indicator.

Don, thanks for the explanation ... I was thinking that neck-sizing first would do a better job of keeping the neck concentric to the case body but as you mentioned, it may not matter either way.

not sure why it has to be full length sizing or neck sizing with nothing in between

Despite the thread title, I'm not trying to make any grand claims here or say that there's only one way to do this. I feel that my equipment is now at a level where I'm seeing a lot more consistency. The result is that subtle differences are starting to show up with more consistency. What was noise, error or simply unexplained before, now has value.

 

[MCMXI]

Here's some data from yesterday. I shot the target below at 200 yards in 22 minutes prone with a bipod and rear Triad Tactical bag. I used the "round-robin" system after the first two sighters S1 and S2. This means I shot one round at the top left, top right, bottom left and bottom right targets and then repeated the order four more times for a total of five shots per target. I don't know what happened to two of the shots on the top right target (0.002" headspace) so that one's kind of a wash. The target puller in the pitts saw a hole in the tape above the left-most hole (of the three) but that's all I know.

It's obvious that I completely messed up the first sighter in terms of windage with only -0.25 MOA of adjustment dialed in. I put this down to the fact that the scope (zeroed for 100 yards) was zeroed at my local range where the wind blows from right to left and the average crosswind value measured with my wind meter was 2-3 mph at the 200 yard line. Based on the correction for S2, the actual wind value was more like 8-10mph but that's the problem with that range, a berm down the left side with access cuts makes for tough wind calls. If you're right next to the berm there's almost no wind the whole length of the 600 yard range, but 50 to 100 feet from the berm and all hell breaks loose! Since I was shooting for groups, I didn't make any adjustments after the second sighter S2.

As for the groups, I was trying to determine if the headspace on a new or full-length sized case would make much difference. The biggest problem I had loading these cases was inconsistent neck tension. I ran all the cases through a 0.335" neck-sizing bushing in an attempt to get a consistent neck diameter, but during the bullet seating step it was obvious that there was quite a lot of variation based on the amount of force required to seat the bullets. The variation in seating effort was most likely due to the necks being out-of-round due to the cases banging around in the fabrication/shipping stages. That's why I like neck-sized fired cases ... the necks are very consistent.

So any thoughts or comments?

 

[Roccobro]

I have nothing really to contribute other than...

I'm drooling over all the good information being posted! :drool:

Justin

 

[MCMXI]

I have nothing really to contribute other than... I'm drooling over all the good information being posted!

Here's some more data. I measured the headspacing of the 52 new cases shot yesterday and here are the size distributions after one firing.

[b][U]Headspace dimensions of 52 once-fired Lapua cases compared to SAAMI reference at 0.000"[/U]

-0.003"[/b] (initial)     [b]-0.002"[/b] (initial)    [b]-0.001"[/b] (initial)    [b]-0.000"[/b] (initial)

-0.001" (4)           -0.0015" (1)         -0.0005" (2)         -0.0005" (1)
-0.0005" (1)          -0.001" (10)          0.000" (2)           0.000" (2)
 0.000" (2)           -0.0005" (5)          0.0005" (1)          0.0005" (2)
                       0.000" (17)
                       0.0005" (2)

Based on the groups and the headspacing measurements after firing, I think I'm going to bump the shoulder back on fired cases to SAAMI + 0.000".

 

[fguffey]

"I'm making the assumption that new brass is the same as full-length sized brass"

I let Sammy size his own cases, I size my cases for my chambers, to start I know the head space first then determine the effect the case has on head space, Terms expressed in SAMMI are for the most part lofty and vague, my standard is my chamber, if I size to SAMMI standards I am sizing cases for something I do not have, I never assume the length of a case from the head of the case to the shoulder even if it is new, once fired, neck sized or formed, not being able to determine the effect the case has on head space is the same as purchasing and firing new commercial ammo.

The new rage in full length sizing started when a shooter from PA set a new world record with a Weatherby 300 Winchester Mag, I have two 300 Winchester mags, one a Weatherby the other is a Winchester Model 70 300 Win Mag (#2, the first one went back after 100 rounds, it was replaced 2 years ago, if I had confidence in it I would have taken it to the range by now). Cases fired in the Weatherby would chamber in Model 70 #1, cases fired in the Winchester were the ugliest/over sized cases I have ever seen, it shot patterns, the pattern got smaller by sizing with reloads but not much. Winchester and I had words, they told me the chamber would require a hone and polish job just to smooth it out, my question "if the chamber is too large in diameter and in length how is honing and polishing going to make the chamber smaller in diameter and length" their answer, "It is policy, we have to try that first".

After 74 rounds of factory Federal ammo, the Weatherby 300 Win Mag shoots one hole groups ( 4 boxes, 80 rounds, the last five went through the same hole, changing ammo changes point of aim not the group). Sizing the cases fired in the Weatherby is effortless, sizing the cases fired in the Winchester was a work out, the value/benefit of full length sizing can not be applied to both the Winchester and Weatherby chamber.

Chambering a rifle that will fit ALL factory ammo is to to say there is (at least) .005 difference between the chamber and case length from the head of the case to the shoulder and bolt face to shoulder of the chamber. If cutting down on case travel when sizing results in longer case life, I choose to extend case life, of when chambering a rifle I can cut down on case travel when fired I choose to chamber a rifle with a short chamber, it it does not work out I can finish the chamber, if I have a rifle that has a long chamber I choose to size cases that eliminate all that case travel, as with the M 1917 Eddystone with .016 head space, I use 280 Remington cases necked up to 30 cal, I form first then fire.

F. Guffey

 

[Duce1]

I have always used full length dies . That is all I own and that is all I will buy .

It has been my personal preference when starting to reload and I have kept with it . I am glad to know and see someone has done a in-depth study of the differences !

Makes me happy .

 

[fguffey]

For the most part the full length sizer is all I need, this does not mean I do not have neck sizer, small base and special dies (RCBS dies hand stamped with an S? or X stamps), Just because the die is stamped F L does not mean I must use it as a full length sizer die, I neck size, partial neck size, neck size with partial body sizing with the full length sizer die, gages come in go .005, no .010 and beyond .014 ( beyond 'field gage' .014 over commercial ammo-.000), with a feeler gage I can size cases from ..017 below the length of a go-gage size chamber (.005, that is .005 longer from the head of the case to the shoulder of factory ammo) to infinity, or (a practical) .010 thousands over a go-gage size case.

F. Guffey

 

[MCMXI]

Terms expressed in SAMMI are for the most part lofty and vague, my standard is my chamber, if I size to SAMMI standards I am sizing cases for something I do not have

SAAMI is a standard, a point of reference no different from any other standard that allows us to compare one measurement to another. Is an inch, foot, yard or mile "lofty and vague"? They only have meaning when compared to standards. If I measure new cases and compare them to the SAAMI standard that tells me something. If I then fire form those cases and measure them again that tells me something else. If you look at the data above showing the before and after headspace dimensions of the new cases fired in my .308 chamber, it looks like my chamber is SAAMI + 0.0005". If I neck-sized all those cases and used them again, I bet more of them would be closer to SAAMI + 0.0005". If I had some fancy way of measuring the chamber maybe I'd get the same or better results but I don't so I'm doing all I can do. Since I was trying to determine how much I should bump the shoulder back after each firing, I feel confident that SAAMI +/- 0.000" will give good results in terms of ease of chambering, accuracy and case life.

 

[MCMXI]

More data from today ... different bullet (178gr A-MAX), same powder (Reloder 15), and the same new Lapua cases sorted by headspacing. The cases used for the two 5-shot groups (shot round-robin) shown below were SAAMI + 0.000" and SAAMI - 0.00015". Despite running the cases through a 0.332" neck-sizing bushing, inconsistent neck tension was still a problem and this may have adversely affected the groups. Average velocities for the 44.1gr and 44.4gr loads were 2754 fps and 2832 fps respectively. There were no signs of excessive pressure such as heavy bolt lift, marks on the case head or flattened primers.