Let's kick this around

[cw308]

When sizing your brass with minimum headspace dimension is it for case life or accuracy . The reason I'm asking is if you bought store bought match ammo . Let's use federal match 168gr. Sierra for a example . They will chamber and fire accuratelyin almost all rifles . There case measures .003 to .004 differences measuring from bolt face to datum line In 308 and a AOL of 2.800 . Maybe powder charge is most important

Cases maybe better self centering along with the bullet , now I'm testing with .003 for the case and a .002 for a jump with the same accurate powder charge I was using before . Next Sunday will see if room makes a difference .

[RC20]

Case life. Full set back per the sizer die mfg will wind up cracking the case down at the base.

Some claim its better to squeeze the round a bit with the bolt cam, others refer to "as loose as a Rat -CENSORED--CENSORED--CENSORED--CENSORED- in a violin case"

They never agree. I don't like using my bolt lugs as a rough cam, they are not intended to do that, so I go with a tad loose.

The jump I think is a separate subject from shoulder set back ala not full size resize but not just neck either. .

[cw308]

I was reloading with a minimum in case space an bullet jump , worked very well but after thinking of this expensive match grade loaded store bought stuff that will work well for those that don't reload . I'm going to test with alittle more wiggle room to see how it compares . Reloading isn't only case life.

[hounddawg]

ditto what RC20 said.

I was using .002 - .003 but this new barrel had occasional issues with some of my older brass so I kicked it to .003 to .004 this morning.

[Unclenick]

You can cam a case tight if you want to. Take a look at the SAAMI chamber and case drawings for the .308 Winchester for example. The head-to-shoulder datum maximum for the cartridge is given as 1.634", meaning anyone manufacturing ammunition that long is meeting the SAAMI standard for new ammunition to fit in all chambers that meet the SAAMI standard. But then look at the minimum chamber, and it is 1.630" from breech face to shoulder datum. In other words, they allow 0.004" of shoulder interference fit. This is because SAAMI minimum chamber diameters are bigger than maximum case diameters and the case can be crushed up to 0.004" before the sides run out of room to expand in the chamber. I would not try to feed such cartridges in a self-loader, though.

The drawback to tight fit like that is the case is seldom formed with perfectly uniform walls all around, so upsetting the walls outward like that tends to pull the neck off-center. With a looser case fit, under firing pressure, after the firing pin has pushed the case shoulder against the chamber shoulder to center the bullet, inertia holds it there well enough that the neck expands with the case body and centers the bullet before uneven expansion of the case walls can pull it off center, so it isn't affected by the uneven case walls so much.

0.002" jump? Are you sure you didn't mean 0.020"? 0.002" is about the variation I see in the distance between the case shoulder and the bullet ogive throat contact location, so rounds loaded to such a small jump will likely vary between 0.001" and 0.003" actual jump (determined by the case shoulder contacting the chamber shoulder and how far forward of that the bullet ogive is; it is not determined by head to ogive measurement unless the case is fireformed to the size of the chamber) with maybe a few touching the lands and a few backed out more.

[cw308]

So with all this going on in resizing cases with .001headspace dimension , jumping or jamming the bullet to the rifling . Chasing that perfect fit to chamber and barrel or sizing to get that very last reload out of a case . Maybe saving our sanity buy going SAAMI spec's and working on powder charge in the hunt for accuracy .

I stopped tweaking my reloads , what I'm doing is with a accurate reload , I'm working on shooting form and my groups are getting tighter and getting back to enjoying shooting. 10 reloads with everything the same . Only wearing out the barrel is what I'm working on now .

[hounddawg]

But CW you reload to be a better shooter, some of us shoot to have a excuse to reload. I am still chasing .5 MOA 10 shot group at 300 but having a ball doing it

[USSR]

cw308,

For 6 years, I shot in 1,000 yard F Class Competition, and here are some of the tricks myself and many of the other competitors used. Note, this is assuming we are talking about a bolt gun for target/match shooting. First, after the bullet, the case is the most critical factor for developing accurate loads. Almost to a man, we all used Lapua brass. Many of us full length resized the brass in 2 distinct operations: the body was resized and the shoulder bumped back using a Redding Body Die; and the neck was typically resized using a Redding Competition neck sizing die with bushings. Low neck tension (.001) was used, and many of us only resized 1/2 to 2/3's of the neck. Regarding the amount of bullet jump, I would never seat a bullet inside of 0.010" of it making contact with the lands because of the variance in ogive dimensions of Sierra MatchKing bullets due to them coming off different machines at the factory. So, I would either seat them to 0.010" off or 0.020" into the lands. If seating into the lands, I found that reducing the powder charge by 0.9 grain produced the same velocity as seating off the lands in my 6.5x55. Hope you find something useful here.

Don

[cw308]

hounddawg
I'm with you , I enjoy reloading as much as shooting and always try to shoot better . 1/2 at 300 yards is a great goal , you must have a load that works for you to get even close to half inch . Trying a different powder could be a game changer an starting all over , even lot changes in powder and bullets will take alittle tweaking . It a great , I don't know if it's a sport , hobby or just alot of fun to shoot and reload .

Chris

[hounddawg]

CW I think the word you are looking for is addiction. Every week seems to be a something new to try and test.

my best so far is a .6 MOA at 300, now if I can just get the hang of centering my groups. I tend to over correct on my sighters but that is a subject for another forum.

[cw308]

hounddawg
Nice group , what are you shooting off of Bi Pod , front rest or bags . All my shooting is off a bench with a Bi Pod and rear bag . Found shoulder touching no pressure on the rear of the stock with a good cheekweld works best for me . Any changes and its just like changes in reloads . That's why I'm trying sticking to my best reload and concentrating on my form . Also found leveling my barrel at the bench when set up for my distance of 200 helps . Cut piece of rug under the Bi pod and adjust rear bag with a towel to level barrel to target.. What's your setup.

Chris

[Unclenick]

Houndawg,

Overcorrecting and then "chasing the spotter" during a match are common problems. System-wise, the human and gun and other variables, with feedback from the spotter (or the hole location viewed in your spotting scope or from electronic target readout) form a correction system that tends to be an oscillator that is always overshooting the right amount of correction and needs some damping. Jim Owens, in his good little book, Sight Alignment, Trigger Control and "the Big Lie", points out a way to apply a damping factor is to correct the sights only half as much as they appear to require so that your corrections approach but never overshoot the right zero. I often use a full correction after the first sighter on the assumption the error is due to different ambient conditions and lot of reloads but use Owens's recommended half corrections thereafter and for the rest of the match. (Note, this does not include come-ups for changing range, which usually have fixed values you know from your records.)

[tangolima]

Unclenick,

I found 0.004" interference quite hard to chamber, even in a bolt gun. I will have to work the bolt quickly to "hammer" the round in sometimes, or the bolt handle simply can't turn down.

I always try to set up the die to have 0.002" clearance. Funny thing is out of a batch of, say 30, brass sized with the same setup, I often have 2 or 3 brass that would still chamber tight. It is when I was using my old Lyman T-max turret press. Such variation mostly disappears when I started using the Forster co ax press. I reckon it is due to the flexing in the press. The T-max has more of that under stress because it is turret.

-TL

Sent from my SM-G930T using Tapatalk

[F. Guffey]

There case measures .003 to .004 form bolt face to datum line ,

Is this something you guys got tougher and changed without telling me? If this measurement has to do with the chamber I would suggest the measurement has something to do with head space; if the measurement has something to do with the case I would suggest the measurement had something to do with case length because I have never got confused when reading SAAMI drawings of chambers and cases drawings and I never assumed head space applied to the case because SAAMI never included the symbol for head space in their case drawings.

F. Guffey

[hounddawg]

@CW

Sinclair bipod and a rear bag. I just feel more comfortable prone and feel I manage recoil better off a bipod that a rest. I shot some last week from the bench using my heavy rest but sitting at a bench just does not feel natural to me.

@Unclenick

I only started competing this year but I am extremely lucky to have a great group of shooters at my club helping me learn the ropes. I received the half correction advice this weekend after doing a classic over correction. The first target the sighters were on the edge of the 8/9 ring so I moved 3/4 MOA left and be damed if my 20 for score were dead centered on the left side of the 8/9.My buddy told me the half adjustment theory and I tried it on the last target and popped a 195 6X with a very heavy mirage at 800

[F. Guffey]

I found 0.004" interference quite hard to chamber, even in a bolt gun. I will have to work the bolt quickly to "hammer" the round in sometimes, or the bolt handle simply can't turn down.

I am the only reloader that works with long and short chambers and I am the only reloader that works with long and short cases as in when measured from the shoulder/datum to the case head, that goes for head space gages also. It does not matter what gage I pick up as long as it (it being the case and or gage) is not the short one.

And then there is the magnificent press that is the strongest in the world, I never assume cases have the same ability to resist sizing, all of my presses have threads, all of my dies have threads; I increase and decrease the presses ability to overcome the cases ability to resist sizing, AND! I am the one with feeler gages.

F. Guffey

[tangolima]

Originally Posted by F. Guffey

I am the only reloader that...

"I am the only reloader". That would have saved a lot space.

-TL

Sent from my SM-G930T using Tapatalk

[F. Guffey]

"I am the only reloader". That would have saved a lot space.

Thank you; This thread is about the chamber and the case, again: I can not find a reloader that feels comfortable with moving away from the '.002" bump'. They never explain how they get the .002" adjustment and they all assume the bump of the shoulder is back. Over and over and over I have said it is impossible to move the shoulder back with a die that has full body contact. They all get angry with me thinking it is my fault they do not understand.


tangolima, explain to me how you bump the shoulder back, you can also try and explain the difference between a bump press and a non-bump press.

F. Guffey
'

[T. O'Heir]

You're over complicating the entire reloading process.
"...minimum headspace dimension..." There's no such thing when referring to cartridges. Cases do not have headspace.
No case will ever measure 3 or 4 thou from the bolt face to the non-existent datum line either. A sheet of regular copy paper is about 4 thou thick.
Store bought ammo, match or otherwise, is loaded to SAAMI specs. The whole purpose of SAAMI is to ensure all ammo from all manufacturers will chamber in all rifles of a specific chambering. However, that does not mean that ammo, be it match grade or not, will be accurate in a particular rifle.
1151 x 719 pixels is too big.

[tangolima]

Originally Posted by F. Guffey

tangolima, explain to me how you bump the shoulder back, you can also try and explain the difference between a bump press and a non-bump press.

Why? I have never said anything "bump". But if you must, it is a direct quote from the only reloader on the planet.

"all of my presses have threads, all of my dies have threads"

So long.

-TL

Sent from my SM-G930T using Tapatalk

[Unclenick]

OK guys, no need to be contentious.

A bumping practice in common terms was implied by the OP talking about resizing just far enough that 0.001" of excess headspace for the cases was created (i.e., the shoulder set back 0.001" from its as-ejected size). However, even though that is now commonly called "bumping", I don't believe it is the original meaning of the term. I try to remember to call it "setting the shoulder back" as distinct from "bumping", though others disagree.

The reason for the distinction is my aging memory recalls the term "bumping" first showing up among benchrest shooters writing in Precision Shooting Magazine in the 70's or 80's who had got custom sizing dies for their rifles cut from blanks using the same reamer that chambered their rifle. A sizing die like that can move a shoulder back without making the brass narrower than the chamber, retaining a neck-sized-only case body fit with the exception of the 0.001"-0.002" excess headspace from "bumping" of the shoulder. Lot's of references are written to the contrary, though, and they call partially setting the shoulder back in an FL sizing die or in a Redding Body Die "bumping". I still think it originally meant setting the shoulder back without narrowing the body below chamber diameters by doing it in one of those custom chamber reamer-cut dies, but that is often not how the term is used today. That is unfortunate because it means the original type of "bump" resizing is being forgotten by the collective handloading community memory as a possibility to explore.

Originally Posted by cw308

There case measures .003 to .004 form bolt face to datum line…
…So with all this going on in resizing cases with .001 headspace dimension…

I have to say that is a little confusing, but I think you don't mean the case is only as long as a piece of paper is thick. I suspect you mean sized until the case leaves excess headspace in the chamber that is 0.001" to 0.003" to 0.004".

Originally Posted by tangolima

I found 0.004" interference quite hard to chamber, even in a bolt gun.

Oh yes. This is not recommended practice unless you decide you want to try it to see what happens with a really tight fit. I don't think I've ever seen a newly made commercial case that was longer than a minimum chamber in .308, and even that was only in some uncommon foreign-made 7.62 cartridges. I am only saying that making the cartridge that long is within the rules of the game. The manufacturers actually know they would get complaints if they made cases that long. The reason it is within the rules is that all SAAMI cartridge length and diameter dimensions are the critical values beyond which operation of the weapon system is prevented due to an oversized cartridge. In the case of the chamber, the dimensions given are critical minimums, with criticality having the same definition but in the opposite directions; too small prevents operation.

[Sevens]

Extremely interesting discussion that is an enjoyable meals for enthusiasts! But with an awful subject line that tells literally ZERO about what is being discussed.

Can we give this conversation a name?

[cw308]

Unclenick
What I meant was the case headspace dimension is so much greater with match SAAMI store bought ammo , and still very accurate . Promise I won't write any books in the future .

Chris

[hounddawg]

CW308 in regards to your first question my current theory is powder charge is not as important to short range ammo as correct seating depth is and finding the right powder for the bullet and barrel is. Powder charge comes into play with consistent velocity at ranges of 500 and greater. Of course the holy grail is a flat velocity node and the perfect seating depth

[cw308]

hounddawg
Never competed in shooting , I shoot with a group of friends each weekend , some have completed . I just like shooting and reloading . The ranges in my area are max. 200 yards , that's what I shoot 200 yards . I load at the low end of the scale ,as long as it shoots where I'm aiming that's all that matters. If I were shooting different distances then that's a different ball game . I don't have a chronograph , some have the ones that attach to the barrel . Two years ago one of the guys first time out with the chrono ,the kind you shoot through a triangle . First shot he mangled that thing , had to walk away , couldn't stop laughing , he was so pissed off at himself . Just gotta love the sport .

Chris