head space and accuracy

[22BRGUY]

Generally speaking, with a known fit between chamber and FL die, setting dies by feel can work, but for many, less experienced reloaders, and for tight chambers there can be a problem. The die can be too large for the chamber, and by the time that the desired bolt feel is obtained, the shoulder has been pushed back too far.
For example:
Friends both had slow twist 6BR barrels chambered for well built custom varmint rifles. The work was done by reputable gunsmiths, using custom dimensioned reamers. While they were in the process of having the work done, I told both that because their chambers were likely to be smaller in the back than standard, that they would be better off ordering FL dies from Harrell's Presision, instead of ordering a similar die from Redding. (I had run into a situation where a Redding S type FL die did not size the back of cases from a tight necked .222 that had been chambered with a match dimensioned reamer that was smaller in the back than factory.) Both friends, being familiar with Redding dies, and not being familiar with Harrell's, ignored my warning, and after they had both their rifles and the dies in hand, discovered that the problem that I had cautioned them had come to pass. By the time that they had adjusted their dies down far enough to size the backs of their cases, the cases' shoulders had been pushed too far back. After that, they both sent in fired cases to Harrell's, and promptly recieved the dies that they have used ever since. This is why I tell people to get the proper tool(s) and always measure shoulder bump, because unlike Tony Boyer, who knows that his die is suitable for his chamber, we have no idea if that is the case when someone posts a question as to how to properly set a die.

Some years ago, a good friend that I had told he should be measuring, disagreed, saying that he had been setting by feel for years, so I challenged him to a test. I asked him to unset and reset his die several times, and bring the resultant sized cases over to my house to be measured using my recently acquired Stoney Point (now Hornady) caliper attachment. He did as I requested, and the measurements were all over the place, much less consistent than he would have imagined. At that point he went home and made some gauges for various calibers that were similar to the one that Harrell's furnishes with their dies.

I believe you are exactly right on Boyd and thanks for the info. It's just that some of us "po folk" try to get by with the less than dies. It's always a matter of priorities I guess and intend to go the custom die route and know it will help just as you said, but trying to have as much fun and precision as I can in the meantime. Best Wishes

 

[BoydAllen]

The economy version of a bump gauge is something like a decapped, trimmed and chamfered .38 Special case, used in combination with dial calipers. Invert the case over the neck of the rifle case, so that its mouth rests on the shoulder and measure the combined length. This, combined with monitoring the diameter of the base of the case, before and after sizing, should get someone on a budget by. If bushing dies are not in the budget, decapping first, and then FL sizing without the expander assembly in the die, followed by expanding with an expander die and mandrel, will give less runout, than the same die would produce using its expander ball. In both cases neck IDs should be lubed, and the lube removed before charging the case with powder. I started reloading with a Lee loader and a plastic headed mallet, and I had a ball.

 

[jaybray]

Sorry to intrude but if a person orders a custom full length die from harrels does one need another new die from them each time a new barrel is re chambered? Even if the new chamber was cut from the same reamer?

 

[BoydAllen]

Depending on the gunsmith that does the chambering....no. Back in the day, that is why I started my 6PPC rifle project by ordering my own reamer. All of my barrels are cut with it to very close headspace tolerances, and I can interchange the brass and use the same dies.

 

[jaybray]

Ok thanks. Once my brass is fired say 10 times, even if annealed with my questionable method using a hand torch, I must bump the shoulder back 4 thou with The redding type s fl die or it will not resize the web area of the case. Set back 2 thou and I cant even begin to close the bolt. I think I better get a harrels die.

 

[BoydAllen]

Yes or a small base Redding, but I would rather have the custom fit. I would send him some of your fired, work hardened cases to be sure that the die that he sends you will do the job on those.

 

[jaybray]

Yes or a small base Redding, but I would rather have the custom fit. I would send him some of your fired, work hardened cases to be sure that the die that he sends you will do the job on those.

I was under the impression I had one. A redding 6br B fl 10.

 

[jaybray]

It looks like I do not have the small base die. I ordered the small base but was sent the 77317 the regular one. I just assumed it was the right one. I needed 77201. Never assume.

 

[bigedp51]

Sorry to bring this up guys but the OP is not shooting bench rest, the OP stated he has been reloading for two years and has started shooting F-Class.

Therefore the word "headspace" and shoulder bump means different things to different people and their shooting venues. And not everyone wants their bolt handle sticking straight out with no head clearance and having resistance on closing the bolt. And the OP asked about "Headspace and Accuracy" and using .002 shoulder bump and asked nothing about benchrest shooting with a small select group of perfectly aligned cases in custom chambered rifles with tight chambers.

So to me gentlemen it sounds like the OP has been setting his dies up as per the instructions with the press reaching cam over without any die adjustments for minimum shoulder bump.

Therefore the OP isn't asking about how a world class bench rest shooter sets up his dies, and we need to get back on topic about the rat turd in the violin case method of sizing.

hello,

I have been reloading for about 2 years now. I do some f class shooting too, and it seems there is always something new to learn in this business.

i always heard about shoulder bumping but i never paid that much attention. it seems that something clicked in my mind and now it seems it does matter.

the question is, how much does proper head space impact accuracy? and how much head space is ideal for accuracy? it seems every where I see that 2 thousands is good, but i dont know.

lastly, can you bump a shoulder with a redding neck bushing sizing die?

thanks

Gil

 

[Tim Singleton]

I didn't see anywhere in the OP about a rat turd and violin method as a topic

As stated the OP asked about head space and ACCURACY. He specifically asked about shoulder bumping. The methods of bumping shoulders and minimal FL sizing is what has been shared.

I think all of the information that has been shared has been on topic



If a rat turd in a violin case yielded the best accuracy then I do believe the world class benchrest guys would load that way. It is the pursuit of pure accuracy that has led to their loading methods.
The OP has enough information to see what works for him

 

[mikecr]

Other than for semiautos, I believe bumping standards presented hold as appropriate.

 

[bigedp51]

I didn't see anywhere in the OP about a rat turd and violin method as a topic

As stated the OP asked about head space and ACCURACY. He specifically asked about shoulder bumping. The methods of bumping shoulders and minimal FL sizing is what has been shared.

I think all of the information that has been shared has been on topic



If a rat turd in a violin case yielded the best accuracy then I do believe the world class benchrest guys would load that way. It is the pursuit of pure accuracy that has led to their loading methods.
The OP has enough information to see what works for him

The Rifleman's Journal
Setting Proper Headpace on Resized Cases
by Germán A. Salazar
http://riflemansjournal.blogspot.com/2009/08/reloading-headspace.html

"Ideally the headspace will be between 0.001" and 0.002" less than the fired cases - this is for a bolt action rifle, for a semi-auto use 0.002" to 0.003" headspace."

The Rifleman's Journal
Short Headspace on New Brass
by Germán A. Salazar
http://riflemansjournal.blogspot.com/2012/04/reloading-short-headspace-on-new-brass.html

"I prefer to set the die for an average of 0.0015" to 0.002" setback on a .308 and allow that 0.001" total variance. That keeps headspace variance a lot tighter. The reason to keep headpsace short and consistent is simply to maximize case life. The more we set the shoulder back, the sooner the case will separate at the base."


Please note nothing is said by Germán A. Salazar about the bolt sticking out at 90 degrees with "zero" head clearance and resistance as the bolt closes. And this will never happen with "0.0015" to 0.002" shoulder bump or shoulder setback.

The Rifleman's Journal
Partial Neck Sizing
by Germán A. Salazar

A case that is only neck sized depends on the case body itself - or at least that's the theory - to center the bullet. In reality, the case is banana shaped to a greater or lesser degree, but always curved and it is highly unlikely that it will actually put the bullet into perfect, straight alignment in the throat. The fully resized neck and a bit of clearance in the throat mean that the bullet is likely pointed off center to some degree, following the curvature of the case.

A case that is full-length sized, but only partially neck sized, which is the condition you describe, depends on the unsized portion of the neck to center the bullet. The resized case body is still banana shaped, but has been sufficiently reduced in diameter at the shoulder to keep the curvature from wedging the case within the chamber. Now, we get to the unsized portion of the neck. There is approximately 0.001" diametrical clearance to the chamber neck on the unsized portion just from normal brass springiness. There is probably no more than 0.0005" diametrical clearance between the bullet and the throat and in many cases as little as 0.0002" clearance. In other words, there is one-half to one-fifth the clearance in the throat that there is in the unsized portion of the neck. Which is doing the alignment? If that were all, we could say there's no harm done by the partial neck sizing, but that isn't the whole story. Unless the bullet is perfectly concentric to the neck, there exists the possibility that the bullet's alignment in the throat is being influenced by the neck's eccentricity in relation to the bullet. If you're relying on two points to align the whole, those two points had better be perfectly concentric. The longer the unsized portion of the neck is, the greater likelihood of the neck inducing a misalignment in the throat due to imperfect neck to bullet concentricity.

Now the last scenario, a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway.

And the first time I read about the rat turd in the violin case was at Mr. Salazar website because he also knew and shot with the late Jim Hull of Sierra bullets testing lab along with Kevin Thomas of "Team Lapua USA". And if the case is even the slighest bit warped and banana shaped a snug fitting case with zero head clearance will aggravate the bullet alignment problem. And the case with .001 to .002 head clearance will have a little wiggle room to be self aligning with the bore.

 

[BoydAllen]

Highpower/across the course, LR prone compared to Benchrest, two different worlds, and sets of accuracy standards. You know that right? They both deserve respect for achievement but the accuracy standards required to win matches is vastly different, as are the skill sets. To me, one is mostly about success in holding and making wind calls, while the other is more about raw accuracy, tuning and of course the wind. It is good to remember the point of reference when reading an article. German writes wonderfully, and would beat me like a rented mule shooting prone, but I remember one article where he compared bullet seating results to three or four places, and then tested the ammo by shooting it prone, loosing the fine distinctions in the noise. Point of reference.....Have you looked at the results for the latest NBRSA Nationals?

 

[bigedp51]

Mr. Boyd Allen

This isn't Benchrest Central, it is Accurate Shooter and you once called my Enfield rifles "quaint" meaning old-fashioned and Sgt. York was an "accurate shooter" and with his "quaint" M-1917 Enfield rifle he was very good at shooting round holes in square heads.

And the last thing Sgt. York and other competitive shooters need is a stiff closing bolt to stay in the game. And the subject was headspace and accuracy asked by someone who has been reloading for only two years and he does not shoot in bench rest competition.

In closing Mr. Allen I enjoy reading your postings because they are informative and very well written. And now the bad news, I first read your postings at Benchrest Central and I Googled your name which lead me to this forum. So now the truth is out and everyone can blame you for me being here.

Now does anyone want to talk about the most important type of headspace that can effect all shooters no matter the type venue.
(I have been told a rat turd in a beer glass can cause excess headspace)

 

[BoydAllen]

No one that I know of, that shoots competitively, strives to have a lot of clearance between his or her loaded ammo and the chamber that it is shot in, neither do they shoot SMLEs or 1917 Enfields. This site is about accuracy, not antique military standard accuracy, but modern, up to date accuracy. Generally, I assume that those who come here for answers are looking to take a step up, rather than back. Even so, your illustrations and pictures are useful to convey basic principals, pictures being better than words alone. The reason that took the time to disagree with your reference to what is desirable in the way of case to chamber fit was that I believe that such colorful stories may lead someone who is relatively inexperienced astray. None of this is intended to discourage your continued posting. The OP spoke of shooting F class. Some time back, those targets were made more difficult, half the size in their centers as standard prone targets. This has made loading and rifle tuning more critical, requiring an approach more akin to the various types of bench based competition, which is the reason for the nit picking. He will have to boot strap up quite a bit to run with the best in that game, and I thought that it was important that he develop an understanding of what that entails.

 

[jcampbellsmith]

..... I always keep my brass bumped to a point to where my bolt (with firing pin removed) will fall half way down before meeting light resistance. This way my case will always be pushed back against the bolt face but not offer enough resistance to upset the rifle on the rest when closing the bolt.
...

I read of this approach of removing the firing pin a lot. One thing puzzles me, what about the ejector plunger? Does that need to be removed too?

Thanks

JCS

 

[22BRGUY]

..... I always keep my brass bumped to a point to where my bolt (with firing pin removed) will fall half way down before meeting light resistance. This way my case will always be pushed back against the bolt face but not offer enough resistance to upset the rifle on the rest when closing the bolt.
...

I read of this approach of removing the firing pin a lot. One thing puzzles me, what about the ejector plunger? Does that need to be removed too?

Thanks

JCS

I don't believe so because the headspace clearance will be determined by the camming down of the bolt against the case head, not the ejector pressure. Good question and may be others will clarify better. We are blessed indeed to have the experience and knowledge of some great shooters here.

 

[bigedp51]

Mr. Boyd Allen

Too many people like you and many others have tunnel vision about the type shooting they do, and a very large percentage of the people reading about reloading and wanting to improve their reloading techniques and skills read these postings. And the vast majority of them have standard factory rifles, and if you read carefully you will see the OP was having his press cam over without any thoughts about minimum shoulder bump. And as I see it the post was taken over by benchrest shooters without regards to what the OP was asking. And judging from what Mr. Salazar and Mr. Thomas of Team Lapua USA said they do not share the partial sizing and zero head clearance of the bench rest fraternity and prefer the rat turd in the violin case method for better accuracy and reliability.

And if you go to the main webpage of accurateshooter.com you will see that this site doesn't cater to just benchrest shooters and covers all types of shooting from .22 rimfire and up. So try and remember that not everyone shoots in benchrest competition and sorts and preps a few cases to perfection and many just buy Lapua (or Remchester) brass and load and shoot with a little head clearance.

And Mr. Allen I sold off the vast majority of my milsurps rifles and bought modern rifles with scopes for my chronologically gifted eye sight. And again this forum has people from all over the world reading these posts that are looking to become "Accurate Shooters" from hunting to "ALL" forms of competitive shooting.

 

[dixieppc]

..... I always keep my brass bumped to a point to where my bolt (with firing pin removed) will fall half way down before meeting light resistance. This way my case will always be pushed back against the bolt face but not offer enough resistance to upset the rifle on the rest when closing the bolt.
...

I read of this approach of removing the firing pin a lot. One thing puzzles me, what about the ejector plunger? Does that need to be removed too?

Thanks

JCS

I might have gotten myself into a thread talking about one discipline when I shoot another so I apologize if I have done so. Anyway, I don't have an ejector on my benchrest rifles.

Regards....

 

[tuck2]

I m not into target shooting but I wont long case life for the ammo used in my varmint rifles. I use the Redding Competition Shellholder Set which has five shellholders of different length . With the set I can use the one which gets the head space best for my rifle chamber. I have enjoyed reading about accurate reloading for target shooting . I don't like missing varmints .