Head space

[Hannibal]

At the risk of getting 'flamed', and on a quest for accuracy, is there a minimum head space requirement, or perhaps recommendation? Or can you go all the way up to engaging the rifling?

[Tatume]

It appears you are confusing headspace with free bore. Headspace specifications should be respected. It is common practice to engage the rifling with cast bullets however.

[Hannibal]

Yes, you are correct. Thanks for straightening me out. Ok. Do the same rules apply with 'J' words?

[Tatume]

Shortening the distance the bullet has to travel to engage the rifling is associated with an increase in pressure. If you are going to load bullets out to touch the rifling, you should start low and work up, watching for signs of pressure. Given the fact that you are asking the question suggests that perhaps you should stick to published loads until you gain more experience. Reliable loading books (Sierra, Hornady, Speer, etc.) will include overall length specifications with their data. The OAL specs apply to the particular bullets only, and cannot be interpolated to other bullets.

There's a lot going on in the assembly of reliable, safe ammunition, and much to be learned.

Take care, Tom

[mikeym1a]

I have always read in various manuals, that the bullet should be seated to where it just touches the rifling. I fail to see how this would cause a pressure increase if normal loading practices are observed. It should add to consistency of shooting, resulting in greater accuracy.

[jonas302]

I try to get really close to the rifling with every load not always possible to kiss the lands magazine length ect I start every load low and never hot rod the oal length in manuals is meaningless to me

[Hannibal]

I'm not planning on going to max loads and beyond max OAL published data. I have duplicated factory ammo accuracy on a bolt action .308 and am in the process of trying to determine why I am still well over 1 MOA at 100 yds. I plan to have my gun smith inspect the bore with a bore scope next week. In the mean time, I am exploring other possibilities. This may lead to a pillar/bedding job or something as simple as a scope and set of rings. Personally, I prefer to examine the possibilities that require the least monetary outlay and work out from there. Which has led me to my question i posed.

[cbrick]

With cast pressure is increased very little by contacting the rifling, with jacketed as already mentioned, if the COAL is too long it is possible to seat the bullet deeper in the case and raise pressure this way. Whenever possible I seat to contact with the lands. In some firearms such as the T/C Contender and Carbine barrels that are really deep throated it can be very difficult to get decent accuracy with cast because of the amount of freebore, frequently in these barrels the boolit cannot be seated out far enough to touch the rifling and accuracy suffers.

Rick

[popper]

I have duplicated factory ammo accuracy on a bolt action .308 and am in the process of trying to determine why I am still well over 1 MOA at 100 yds.
Me thinks you want to say your cast loads = jacketed factory accuracy and why doesn't your rifle shoot better? First question is what type rest are you using, i.e. you or the rifle the problem? Consistent MOA is NOT an easy task. Not enough posted info to really give an answer. You talking a milsurp or NIB?

[Hannibal]

(SIGH.) ME thinks you people are reading too much into my question. Yes, I could have spent $2000 on a custom rifle and another $1000 on optics and had an out-of-the-box tack driver and learned NOTHING.
My question was, though I asked incorrectly and was immediately set straight, is there a minimum free bore space needed on jacketed bullets.
The answer apparently is NO.
Thank-you.

[runfiverun]

ths confusion was probably about asking in a cast boolit forum and meaning jaxketed bullets.
you gotta be a little more clear.
they are two completely different worlds.
heck the rules change when dealing with cast, depending on your goals and what boolit style you are using to attempt to reach them.

[cbrick]

Several people tried to offer advice to your self admitted incorrectly asked question . . . And you sound irritated. Amazing.

Rick

[Hannibal]

The only reason I am approaching irritation is somehow my question responses have morphed from head space to rest/trigger skill/equipment.
Am I a competition level shooter? No.
Do I own competition level equipment? No.
Does either one effect head space limitations? Based on what I have learned thus far? No.
Are the answers different for cast bullets and 'J' words? Apparently YES.
Ah, Ha!
Please excuse me while I am in the process of gleaning information from those more experienced than myself.
And please excuse me if I know but have not communicated that I am quite capable of meeting my accuracy expectations with other rifles utilizing the same rest and shooter. (Myself).
And thank-you to those of you who have been generous enough to offer constructive feedback.
I was not intending to offend, just keep the responses on topic.
Sometimes I learn more than I bargained for.

[uscra112]

(SIGH.) ME thinks you people are reading too much into my question. Yes, I could have spent $2000 on a custom rifle and another $1000 on optics and had an out-of-the-box tack driver and learned NOTHING.
My question was, though I asked incorrectly and was immediately set straight, is there a minimum free bore space needed on jacketed bullets.
The answer apparently is NO.
Thank-you.

Generally speaking, the answer is YES, a j-wart should be seated so that it is off the lands by a little bit, maybe .010" at least. A j-wart stuck into the lands, they way we do with boolits, acts like a bore obstruction, leading to excessive pressures. In fact the best explanation yet advanced for the so-called S.E.E. is that a long j-wart is knocked into the lands by the primer blast a millisecond or two before the powder lights up. The j-wart is so firmly stuck there that pressure goes to "blow-the-gun-up" levels. Every experimenter going all the way back to pre-WW1 days found this out and wrote vociferously against putting a j-wart in contact with the lands.

[Hannibal]

Yikes! Thank-you, sir! This is the very sort of plain-spoken response I was looking for. Again, thank-you!

[dtknowles]

Generally speaking, the answer is YES, a j-wart should be seated so that it is off the lands by a little bit, maybe .010" at least. A j-wart stuck into the lands, they way we do with boolits, acts like a bore obstruction, leading to excessive pressures. In fact the best explanation yet advanced for the so-called S.E.E. is that a long j-wart is knocked into the lands by the primer blast a millisecond or two before the powder lights up. The j-wart is so firmly stuck there that pressure goes to "blow-the-gun-up" levels. Every experimenter going all the way back to pre-WW1 days found this out and wrote vociferously against putting a j-wart in contact with the lands.

Not every experimenter, I have read many publications where the author indicated that seating bullets to jam might lead to better accuracy. I have seated bullets to jam with varying neck tension to try to improve accuracy in a 6mm PPC. I am back to 0.01 off of jam. I even tried 0.10 beyond jam with almost no neck tension so the bullet was purposely pushed back a tenth of an inch into the neck. After all the futzing around it did not matter because they all shot better than I could.

Tim

[rsrocket1]

The only reason I am approaching irritation is somehow my question responses have morphed from head space to rest/trigger skill/equipment.

I think the comments/questions were related to the following statement, not your original post


I have duplicated factory ammo accuracy on a bolt action .308 and am in the process of trying to determine why I am still well over 1 MOA at 100 yds.

Now by this, do you mean you cannot get 1 MOA with either factory loads or handloads or do you mean you do get sub MOA with factory loads and > MOA with handloads?

You have to start with a standard, then change one variable at a time to see if it has an effect on your results. If you can't get 1 MOA, how do you know what's causing it? Freebore may not make a bit of difference if the crown of your barrel is bad, your scope has loose internals or if you have some other problem with your gun. Now if you said you shoot single holes at 100 yards and your handloads are 2 MOA and the only difference is the freebore, then you know it's not the gun, scope or the shooter.

[Hannibal]

I presume you are speaking of the response from uscra112? His explanation of the possible cause and apparent damage seems plausible. However, if you and others have found this to be untrue, I am certainly willing to listen to contradictory information.
Again, I came here to learn without any pre-conceptions.
If you already know all there is to know about accurately loading ammunition, then I applaud your accomplishment. Somehow I doubt that I ever will.

[303Guy]

Hi guys.

If I may add a little snippet here, jamming the 'j-wort' into the leade is supposed to raise pressure by some fixed amount - 10% rings a bell. That's if the bullet is not pushed back into the case. The worst case pressure rise is from a 308 cartridge fired in a 270 Winchester chamber. The cartridge then head-paces on the bullet ogive. Some actions will fail while some amazingly, survive! But the principle of seating to kiss the leade is more about bullet alignment with the bore. The analogy with the SEE event is close enough but is a little more complicated in that not only does the bullet stop against the leade but the powder is already burning so the 'burn rate' is then seriously altered towards way too fast. SEE's have been duplicated in the lab following a 6.5 Swiss factory load going ka-boom in milsurp rifles but were fine in the test barrel. Hopefully there is some relevance here.

[Hannibal]

I apoligize for not being clearer, i did not think it relevent at the time. Yes, I am unable to achieve 1 MOA at 100 Yds. with either hand loads or factory ammunition in this particular firearm. I have perhaps been lucky, but in the past I have been able to make considerable strides in accuracy in other firearms by simply sticking to the basics. This firearm is relatively new to me, and I have only recently found the time to investigate the accuracy issue with it. This condition is not a new one, but one it had when new a couple of years ago. While not horrible, I find it unacceptable. Particularly in a .308, well known for being the most accurate 30 caliber round. Before I spend additional monies trying to fix this problem by 'throwing parts at it', I am attempting to explore other possibilities. Free bore is something I had heard of before, but not something I had experimentmented with in the past. Thus, my question I posed. As I am soon to attempt loading cast boolits in my 30-30, I thought I would pose the question here, not realizin the confusion it would cause. I was un-aware that free bore is treated so differently with cast and jacketed bullets.

I think the comments/questions were related to the following statement, not your original post



Now by this, do you mean you cannot get 1 MOA with either factory loads or handloads or do you mean you do get sub MOA with factory loads and > MOA with handloads?

You have to start with a standard, then change one variable at a time to see if it has an effect on your results. If you can't get 1 MOA, how do you know what's causing it? Freebore may not make a bit of difference if the crown of your barrel is bad, your scope has loose internals or if you have some other problem with your gun. Now if you said you shoot single holes at 100 yards and your handloads are 2 MOA and the only difference is the freebore, then you know it's not the gun, scope or the shooter.

[Biggs300]

If you haven't already done so, you may want to consider investing in a Hornady or Sinclair OAL Gauge to measure the length of your chamber. Using this tool along with a headspace gauge, you should be able to find the optimum COAL for accuracy in your rifle by reducing the bullet seating depth. Using the headspace gauge you should be able to duplicate when reloading. Take good notes during the process and check for pressure signs at the range. Even though most of my reloading is done to create accurate hunting rounds for my various rifles, these tools have proven useful.

[Tatume]

Maximum overall length (OAL) can be determined in many ways. My favorite follows, but is only applicable to the particular bullet used in the test.

Back off the sizing die. Put a fired case in the shell holder and raise the ram. Screw down the sizing die until contact is made. Lower the ram slightly and screw the die down a little more, raise the ram, lower the ram, and remove the case. Try a bullet in the case. If the bullet is loose, repeat the process. When sufficient resistance is induced that the bullet is held firmly in the case neck, but can still be moved with the fingers, the case is ready to be used to make measurements.

Put a bullet in the case and leave the OAL only slightly too long. Gently chamber and remove the dummy cartridge. Measure the OAL with a caliper. Repeat several times.

This OAL only applies to the particular bullet used in the test. If another bullet with a different ogive is used then determine the maximum OAL for that bullet independently.

For most sporting ammunition I like to use 0.010” less than maximum OAL.

Take care, Tom

[Elkins45]

This is one of those places where cast and jacketed can behave differently. It's also one of those places where every gun is an individual, but as a starting point I don't like to make a cast bullet jump very far unless I have a good reason. Most of my bolt action rifle loads with cast have the bullet actually touching the lands just a tiny bit, but I don't load anywhere up near max.

[375RUGER]

I'd suggest that you invest in some match grade ammo, Hornady 168g A-max Superformance is good stuff. If your rifle still won't shoot with that for you, find a friend or someone whom you know can shoot and see if they get the same results.
You might also tell us about the equipment: rifle, scope, ammo, what rest you use to shoot, handload data, etc., problem may not be the rifle. I think your problem lies somewhere besides "freebore", but I could be wrong.

[gray wolf]

I apoligize for not being clearer, i did not think it relevent at the time. Yes, I am unable to achieve 1 MOA at 100 Yds. with either hand loads or factory ammunition in this particular firearm. I have perhaps been lucky, but in the past I have been able to make considerable strides in accuracy in other firearms by simply sticking to the basics. This firearm is relatively new to me, and I have only recently found the time to investigate the accuracy issue with it. This condition is not a new one, but one it had when new a couple of years ago.
While not horrible, I find it unacceptable. Particularly in a .308, well known for being the most accurate 30 caliber round. Before I spend additional monies trying to fix this problem by 'throwing parts at it', I am attempting to explore other possibilities. Free bore is something I had heard of before, but not something I had experimentmented with in the past. Thus, my question I posed. As I am soon to attempt loading cast boolits in my 30-30, I thought I would pose the question here, not realizin the confusion it would cause. I was un-aware that free bore is treated so differently with cast and jacketed bullets.
First off what is the rifle you are shooting and how are you shooting it ? and what factory ammo ?
how much load testing have you done with it ? how many powders and how did you work up your loads, by that I mean how many rounds of each different powder charge did you load and shoot. Did the barrel cool ?
How solid was your bench rest ? did you use sand bags ? did you use a rear squeeze bag and a front forearm rest ? did you try different positions for the front rest ?
Did you try different torque on the action screws ?
did you use a scope and did you check your ring and base screws ?
Over all length is a good tool to increase accuracy for a rifle that is shooting real well, and all other variables have been worked out. It can take many rounds to find that sweet spot. Also if your not shooting 1MOA or better you are not going to get there by changing how far out the bullet is seated. ( it's one of the tools ) And the gains could from it could very well be very small.
I's like a question I hear all the time: should I turn the necks for my factory rifle that has a factory chamber ?
Clean them up a tad, maybe, turn them down ? NO, for reasons I am not going to go into.
Also what makes you think this rifle will ever shoot 1MOA or better ? Some rifles just flat out do not.
It's just not within the capabilities of every rifle. If a factory rifle shoots 1 MOA with a decent factory bullet
( not the best ammo just decent ) Chances are you can get it to shoot 3/4 with a good hand load if your really good and put the time in for different bullets and powder perhaps a little better.
Also a rifle that shoots a 1" group 1 time out of 5 or six different groups is not a 1MOA gun, sometimes don't count, even though that's the group people like to cut out and put in there wallet.
I didn't mention or ask if you cleaned the rifle well before your testing was done, And did you let it cool a little or shoot it hot?
Weatherby rifles are some of the most accurate factory rifles made. Did you ever look at the free bore in a weathery ? some of them the bullet will fall out of the case trying to load to jam.

Particularly in a .308, well known for being the most accurate 30 caliber round.
It's an accurate round but I would not tag it as the most accurate.
IMHO I don't think any of these questions are UN-pertinent to the issues your having or trying to solve.
Nor were any of the other questions asked. Every one in this room has two concerns that float to the top, keeping people safe and trying to do the best they can to help and answer peoples questions.

[rsrocket1]

Yes, I am unable to achieve 1 MOA at 100 Yds. with either hand loads or factory ammunition in this particular firearm.
That helps a lot. What causes an inaccurate gun/load is an investigation in itself much less trying to determine what will make a lead bullet shoot more accurately. The suggestion of starting out with match grade jacketed bullets is a good one. A box of 100 projectiles usually costs less than $30 and would be a good investment to take all the projectile questions out of the picture. To start out, you might even buy a box of fully loaded match grade bullets. If you can't find an accurate load that gets you less than 2 MOA, then you should check out the barrel/scope/bedding. Yes, the .308 is typically a very good caliber for accuracy "out of the box" and should typically be somewhere around 1 MOA with a good rest/scope.

For instance, my 788 .308 can shoot 1 MOA with jacketed bullets at nearly any reasonable load. Just the POI moves around so as long as I pick an acceptable load and match it, the scope setting is good to go. When moving to 110g light bullet loads, I adjust for best group that has the same POI as my full house loads so I can now shoot either without changing scope settings. I am now casting 3 different weight boolits for the gun and will do the same with each bullet knowing that the gun is capable of 1 MOA. If I didn't know that, I think I'd be lost.

[shooter93]

I've owned rifles that shot best with the bullet into the lands but have also owned many that shot best with the bullets way off the lands. I had a 22 Hornet that shot amazingly well but only ay 15 thousands off the lands. Against them accuracy went out the door same with 20 thou off. 15 was the magic number for THAT rifle.

[popper]

If you are trying to get MOA @100 with Open sights, get a scope. If you get 3" or better I'd say the bore is good. Set your sizing die for the proper head space. 308 spaces on the shoulder, 30/30 on the rim. I would wait on the gunsmith stuff till you find out how well the rifle really shoots factory and your reloads. 168 gr Amax bullit is a good one for 308.

[Tatume]

Shooting MOA is not something every rifle is expected to do. When I was young an MOA rifle was the Holy Grail, and it was many years before I ever saw one. That didn't make our rifles any less useful. A two MOA rifle would still win High Power matches, and a three MOA rifle would still kill deer as far out as almost everybody should be shooting at them.

A two MOA rifle will still win most matches if a good shooter is pulling the trigger. Further, buying a one MOA rifle will not cause one to win more matches. Almost all imprecision is in the shooter, very little is in the rifle.

[44man]

Head space in a bottle neck case is not that important. It can vary with no affect on accuracy at all.
Once a case is fire formed adjust dies so the shoulder is never set back and the brass now fits and is adjusted for the head space on that rifle.
Head space is measured to a datum line on the shoulder, nothing to do with boolit seating UNLESS the shoulder has been set back. The quick, dirty fix is then to put the boolit to the lands.
With a bolt gun you want just a little resistance to closing the bolt on an empty, sized case. Can't do it with a lever, pump or auto so cases must be sized more. Still does not hurt much if brass just fits and chambers.
Each rifle is different and some need a bullet .020" off the lands, others or other bullets want .010" and some want touching. That is not for head space, just what the gun prefers for the bullet/boolit.
You can actually work an accurate load using the same powder charge and only changing seating depth.
Once brass fits you can forget about head space.
Look at the accuracy of factory rifles with factory loads today, rounds are made to fit ALL guns no matter the head space.
It is a non issue for accuracy.
Over sizing to increase head space only shortens brass life as it stretches over and over to fit. Then you have bolt stretch (compression a better word) on lever guns that stretches brass even if it fits.

[grouch]

I would really hope that no one on this(or any other forum) would claim to know everything about reloading ammunition. Probably not since Francis Bacon has anyone had the gall to make a claim like that with a straight face.
Please try not to take offense, and,fellows, let's try not to give it.
Grouch

[375RUGER]

I don't know where that came from but what's going on here is people trying to fish out the pertinent information needed to help Expanman. i.e. if he says he's using a bipod on the bench, there would be a consensus here saying "ditch it, use bags". The whole story is out there, but it's not on this thread.