Headspace & reloading

[Black Jaque Janaviac]

I read the headspace thread above with interest.

Particulary interesting was one man's ingenious way of fireforming .303 brass to headspace on the shoulder without stretching above the web.

Could this be done with a rimless case by seating a bullet out so far that it engages the rifling and let the bore actually seat the bullet?

I kind of like the idea of fireforming brass for accuracy yet still having the reliability of using factory ammo. That and I'm afraid that turning the barrel in further will not be an option. I have a front sight ramp on it and I don't want it lookin' crooked.

[bigedp51]

I wrote about using the rubber o-ring for fireforming the .303 British, with an Enfield at maximum military headspace and a cartridge case with minimum rim thickness you can have .020 head gap clearance. I also do not advise lubing cartridge case for fireforming because it doubles the bolt thrust or force on your bolt when the cartridge is fired. I prefer using the rubber o-ring on the .303 cases because when the rubber o-ring is compressed it centers the rear of the case in the large chamber. With American made .303 cases chambering a cartridge in the military Enfield is like parking a Smart Car in a Blimp hangar. ::)

There are two methods for fireforming cases, creating a false shoulder that stops forward case movement and holds the case against the bolt face. The second is seating the bullets long and hard into the rifling, the neck tension must hold the bullet firmly in place and the bullet pushes and holds the case against the bolt face.

I have a new .243 Stevens 200 with 200 loaded cartridges ready for fireforming, 50 loaded with a reduced load of Trail Boss and the bullets seated long. 50 loaded cartridges 2 grains below maximum and the bullets seated long. And 100 cases loaded the same as above with a false shoulder and the bullets not touching the rifling.

The problem is some of the new Remington and Winchester cases are .005-.006 under minimum headspace and the headspace of the Stevens 200 is .001 over minimum headspace. This gives me up to .007 head gap clearance which "might" cause problems if the cases are not fireformed properly ("0" zero head gap clearance) when fired.

Depending on headspace and chamber diameter you will be contending with axial and radial expansion of the case when fired. The less "slop" your case has when it is fired the less case stretching and possible case distortion you will have with the new fireformed case.

Some "aids" in resizing your new fireformed cases. ;)

http://i122.photobucket.com/albums/o254/bigedp51/7-17-201054719PM.jpg

http://i122.photobucket.com/albums/o254/bigedp51/7-17-201054345PM.jpg

http://i122.photobucket.com/albums/o254/bigedp51/7-17-201055522PM.jpg

Below is a good read on resizing methods and accuracy.


From: bartbob@aol.com (Bartbob)
Newsgroups: rec.guns
Subject: Re: Bottleneck Cases - Seating and headspace
Date: 11 Jan 1996 09:34:11 -0500

Your questions about reloading the .308 Winchester are good.

Headspace for the .308 Winchester, as well as other rimless, bottleneck cases, is measured from the closed bolt's face to a datum point on the shoulder. This datum point for the .308 Win. is .400-inch. Minimum .308 Win. chamber headspace is 1.630-inch. Maximum is about 1.650-inch. New cases typically measure about 1.628-inch from case head to the shoulder's datum point so they will easily fit in minimum-headspace chambers, yet not stretch in firing enough to cause head separation problems when fired in a maximum-headspace chamber. New cases typically end up with a fired-case headspace dimension of about .001-inch shorter than the chamber's actual headspace.

Headspace is measured with steel gages precision ground to specific dimensions. They are put in the rifle's chamber, then the bolt is gently closed. If the chamber is too short and a minimum gage is used, the bolt won't fully close; the chamber must be lengthened with a reamer to fix the problem as new cases may not allow the bolt to be closed. If the chamber headspace is between the minimum and maximum limits,then the minimum gage will let the bolt easily close. If a maximum gage is put in the chamber, the bolt should not be able to close which verifies the chamber headspace is within manufacturing limits for safe use with new cases. But if the bolt closes on a maximum gage, chamber headspace is too long and new cases may rupture if fired in such a chamber. Minimum gages are called "go" gages, maximum gages are called "no-go" gages based on the idea that a the bolt should "go" closed on a go-gage and "no-go" closed on a no-go gage.

Bottleneck sized- or new-case headspace can be measured with a gage such as the RCBS Precision Mic. A case is put head-down in the gage, then a micrometer thimble is screwed on and tightened until it stops against the shoulder. The gage is read in thousandths of an inch. Loaded rounds can also be measured with such gages.

Here's what was learned back in the 1960s about sizing cases. It applies to the .308 as well as other rounds of similar size. Tests were conducted with super-accurate .308 Win. match rifles. Chamber headspace was 1.630-inch,or minimum. Rifles were held in an unrestricted machine rest. An unrestricted machine rest clamps the rifle's forend and butt much like it would be held by someone. On firing, it moves with the same resistance for each shot. It slides on three steel rods riding in V-blocks and moves about 3 inches when fired. The upper cradle is moved back forward against a stop after each shot and repositions the rifle exactly the same for each shot. Such machine rests eliminates all human variables in holding and are commonly used by bullet making companies and military arsenals for accuracy testing. Sometimes only a barreled action is clamped in the rest; pictures of such machine rests are shown in Sierra's reloading manual. The US Olympic Shooting Team uses similar ones for testing .22 rimfire match rifles and ammunition as they know humans can't test them as well as the rest can.

Such tests are much, much better than shooting a highpowered rifle from a bench because of one important, but little known reason. The more recoil a rifle has, the more very, very slight changes in how it's held effect how it moves as the bullet goes down the barrel; very small changes cause the barrel axis to be different for each shot as the bullet leaves. Rifles used in 100 to 300 yard benchrest matches shoot mild cartridges with small powder charges and light bullets which are shot in virtually free-recoil conditions unimpeded by differences in holding which is near machine rest conditions. When held firmly like rifles shooting larger, more powerful cartridges have to be, they typically shoot much larger groups than the sub 1/4th-MOA ones they are famous for. Rifles tested in machine rests typically have groups with smaller spreads between largest and smallest ones than when conventionally benchrested. What this means is that most highpowered rifles actually shoot better than conventional benchrest techniques show.

The .308 rifles fired in a machine rest would shoot about 1/2-MOA test groups with cases sized correctly for best accuracy. Note that twenty or more shots were fired for each group. When hand-held and shouldered from a typical benchrest with the rifle's forend and stock toe on sand bags, the groups would be in the 1 MOA range. Here's a summary of what was learned from these tests.

When a full-length sizing die was set in the reloading press as instructions said, sized cases had a head-to-shoulder headspace typically shorter than a new case. When fired, these cases produced test groups about 1.5-MOA. Note that the die was set in the press such that its bottom just touched the shellholder as the ram was at the top of its movement. This caused the case shoulder to be set back so the sized-case headspace dimension was typically shorter than that of a new case. Such instructions supplied with reloading presses and dies are required for two reasons regarding chambers with minimum headspace dimensions. First, the great variety of chamber sizes for a given cartridge vary quite a bit and the manufacturer wants to be sure sized cases will chamber properly. Second, the amount of case lube applied causes sized-case headspace to vary several thousandths of an inch; lightly lubed cases will have a longer headspace and the manufacturer wants to be sure cases so sized will fit in minimum headspace chambers. Cases so sized could be reloaded about 10 times before their head separation became imminent.

Fired cases partially sized in a full-length sizing die with about three-fourths of the neck sized produced test groups about 1.5-MOA groups. Cases so sized had their body diameter's reduced a couple of thousandths of an inch which moved the shoulder forward several thousandths of an inch. These partially-sized cases were actually longer in head-to-shoulder datum point dimension than the chamber's headspace dimension. A slight binding was noted as the rounds were chambered. Case life of these cases was about 20 to 30 reloads.

Fired cases that were neck-only sized in dies that didn't have their body diameters reduced but their necks were sized down would shoot groups about 1-MOA groups. Subsequent firings of the same case resulted in its shoulder moving forward enough to cause very slight binding as the bolt was closed and groups opened up about 1/4th MOA with such cases. About 30 to 40 reloads per case was possible.

New, never fired cases produced test groups about 3/4ths-MOA even with all their irregularities from manufacturing. The smallest test groups came from cases full-length sized such as the shoulder was not set back from it fired position. Sized-case headspace was the same as, or not more than .001-inch shorter than fired-case headspace. Test groups were about 1/2 MOA. And cases could be reloaded
20 to 30 times.

This well explains why most folks get better accuracy with partial-sized cases using full-length sizing dies than by following press/die instructions for full-length sizing. It also explains why they get better accuracy with neck-only sized cases compared to conventional full-length sizing with the die set according to supplied instructions.

It should be mentioned that the machine-rest tests were made at 600 yards. Had the tests been done at 100 yards, the smallest groups would have been about 2/10ths-MOA and the largest ones about 3/4ths-MOA. In one test, 40 consecutive shots were fired into just under 2 inches at 600 yards. To do that well, the group at 100 yards would have to be about 1/10th MOA.

By using a sized-case headspace gage like the RCBS Precision Mic, you can set a full-length sizing die in a press such that it sizes the cases just enough to set the shoulder back no more than .001-inch. You'll probably get best accuracy this way as well as excellent case life.

[Balljoint]

These's post have some very good ideas so i printed them out

[bigedp51]

I would like to add something, I have been reloading for over 40 years and "NEVER" had a case seperation or an indication of one in a normal chamber on a commercial manufactured rifle.

"BUT" I did come this close on a military British .303 Enfield because the cases were not fireformed correctly. The case below was only fired three times and I did not use the rubber o-ring trick or a false shoulder to fireform these cases. I used too light or low chamber pressure while fireforming and the case ended up headspacing on the primer, in other words I did not eliminate my head gap clearance or "air gap" between the rear of the case and the bolt face.

http://i122.photobucket.com/albums/o254/bigedp51/IMGP5191.jpg

A full length resizing die when it contacts the shell holder resizes the case approximately .002 shorter than minimum headspace. If your chamber is .003 over minimum headspace and you full length resize with the die touching the shell holder you will push the shoulder back .005 every time you resize the case and will shorten its reloading life.

.308 resizing endurance test. ;)

http://i122.photobucket.com/albums/o254/bigedp51/308fail.jpg

http://i122.photobucket.com/albums/o254/bigedp51/308fail-2.jpg

[gotcha]

Big Ed, As usual very interesting & enjoyable reading! For those who'd like to try the head spacing methods outlined. It's only necessary to have a cartridge headspace gauge that attaches to your calipers. And a set of feeler gauges to set the distance between the shell holder & the bottom of the die. (except the .303 british of course) Once the correct die seating depth is established firmly set the lock ring. I use this method and can usually get the proper die setting in just a couple of tries. I can usually hold cartridge headspace between .001" &.002" depending on the quality of brass I'm using. I have had dies that required a small amount of material be removed from the shell holder contact point. I won't mention the name of the Mfg. except to say they came in a green box. :D

[bigedp51]

Big Ed, As usual very interesting & enjoyable reading! For those who'd like to try the head spacing methods outlined. It's only necessary to have a cartridge headspace gauge that attaches to your calipers. And a set of feeler gauges to set the distance between the shell holder & the bottom of the die. (except the .303 british of course) Once the correct die seating depth is established firmly set the lock ring. I use this method and can usually get the proper die setting in just a couple of tries. I can usually hold cartridge headspace between .001" &.002" depending on the quality of brass I'm using. I have had dies that required a small amount of material be removed from the shell holder contact point. I won't mention the name of the Mfg. except to say they came in a green box. :D


gotcha

You stated you had to remove material or make the shell holder shorter, in another forum a person was having a problems getting a resized case to chamber because a cartridge case was used as a headspace gauge. Resizing dies are manufactured assuming zero or minimum headspace is the base line, if the headspace on a Savage/Stevens is adjusted below minimum headspace standards the reloading die will not be able to touch the shoulder of the case and push it back.

If you buy a European made rifle due to different manufacturing standards established by the European "CIP" or equivalent of the American SAAMI you can also have chambering problems.

Delta L problem

"The delta L problem (?L problem) is a condition that occurs regarding certain firearms chambers and their practical incompatibility with ammunition made for the corresponding chambering. The ?L refers to a Commission Internationale Permanente (C.I.P.) geometric dimensioning and tolerancing definition for firearms cartridge cases which are longer than the chamber they have to fit in."

http://en.wikipedia.org/wiki/Delta_L_problem

This RCBS shell holder below was shortened .003 in order to properly resize a .270 Win cartridge case for a Czechoslovakian made mauser. It is a beautifully made rifle with a tight chamber and the "standard American" full length resizing dies would not push the shoulder back. If you adjust your headspace on your Savage/Stevens rifle below minimum headspace standards you "WILL" have problems resizing your cases.

Below, .003 removed from the top of the shell holder by lapping the top of the shell holder. We live in a "plus and minus" manufacturing world and if you make the chamber "minus" too large you are going to have resizing problems and your FL dies will not push the shoulder of the case back to minimum standards.

http://i122.photobucket.com/albums/o254/bigedp51/IMGP6943.jpg

Bottom line, if you use a cartridge case to adjust your headspace you could have problems, I have new .243 Win cases that are .006 shorter than minimum headspace. If a "short" case is used to set your headspace then expect your full length resizing dies to "NOT" resize your cases properly. This is because "YOU" have created your own "Delta L Problem" and made your chamber too short for your resizing dies.

[gotcha]

Big Ed, Excellent point! The problem I encountered was with an old Mark X Mauser barreled action in .270 I acquired years ago. This was also the 1st time I used Lee dies and assumed the problem was caused by the dies. I chucked the Lee's into the trash, bought a set of green box dies and low and behold had the same problem. As I recall, I took .0025" off the bottom of the die. Problem solved. It's now my son-in-laws favorite white tail rifle. But, I still do the reloading ;D Just one of the reasons I always use a headspace gauge on Savage/ Stevens. Keep the good stuff coming, Dale

[Innovative]

Your concern for excessive chamber clearance is a good one. Look into the Digital Headspace Gauge. It works on ALL different calibers, and it doesn't require using any special bushings or attachments.

[wever]

Hope I don't go of course from your thread with this question, if so - disregard. My question is in reference to my 7mm Rem Mag model 111, mfg 1999, had it since new but never a good shooter. Brought it out recently and I think I discovered why, the difference between new factory ammo of numerous mfg. and fire formed brass from same boxes is .023!! I was going to order a go no go gauge for 7mm mag then discovered that most belted magnum calibers use the identical part number go no go gauges, leading me to believe that if a .264 win mag is going to pass with the same "go" measurements as a 300 H&H will, it's not going to answer any accuracy questions. So I decided to order a neck sizer die and see if accuracy improves - any thoughts, suggestions or feedback gentlemen?

[drybean]

check out the dies & gauges at innovative technologies

[Innovative]

wever .....

You'll always find that factory loads have .018" to .030" chamber clearance at the shoulder. Factory loads (for belted mags) headspace on the belt. However, Handloads NEED to headspace on the shoulder. Keep in mind that headspace and chamber clearance are 2 different things with belted magnum calibers.

Conventional headspace gauges are used for installing barrels, not useful to the handloader.

Limiting chamber clearance "at the shoulder" eliminates case head separations. Case separations are caused by repetitive (and excessive) case stretching. My website has several good pages on this subject.


WWW.LARRYWILLIS.COM

[bigedp51]

wever

The belted case is a British design and being the traditionalists that they are the British decided to put a rim on a rimless case. ::) What is forward of the rim or belt is immaterial, it will expand outward to fill the chamber the first time it is fired. I don't have any 7mm Remington Magnum so a .303 British with a rim will have to do. Below in the top photo is British Commonwealth 1982 South African made military .303 cartridge in a Wilson case gauge. This surplus ammo is .002 below the lip of the Wilson case gauge and right where it should be for new ammunition.

In the bottom photo is a brand new Remington .303 case and the shoulder is 1/8 short of where it should be. Rimmed and belted cases can be very forgiving for faulty-sloppy manufacturing standards, all that really matters is from the rim or belt to the bolt face or head gap clearance. (the air space between the bolt face and the rear of the cartridge.

http://i122.photobucket.com/albums/o254/bigedp51/twocases.jpg

Below you can see it is the head gap clearance that causes case head separations and all your problems when reloading and "over resizing" your cases.

http://i122.photobucket.com/albums/o254/bigedp51/headspacestretch-1.gif

http://i122.photobucket.com/albums/o254/bigedp51/headspacestretch_frame_002.jpg

Once your cases are fireformed for your chamber the secret for long case life is to only bump the shoulder back when necessary and "NO" more than .002. So as Mr. Willis stated you will need some form of gauge to measure the distance from the shoulder to the base of the case to prevent over resizing with full length resizing dies.

http://i122.photobucket.com/albums/o254/bigedp51/fireformed-zeroheadspace.jpg

So to your accuracy problem and cartridge concerns, the "short" Remington .303 cases pictured above shot groups equal to or better than reloaded ammunition that was a tight fit in the chamber.

I would suggest two things to try to improve the accuracy of your Savage 111.

1. Clean the barrel several times with foam bore cleaner allowing the foam to set overnight.

2. Put some thin shimming material under the barrel at the fore end tip like the same raised area on a Remington 700. My Enfield rifles are made with 2 to 7 pounds of up pressure at the for end tip and a Remington 700 has 3 to 9 pounds of up pressure at the fore end tip. This up pressure is used to dampen barrel vibrations and improve accuracy.

Its the "bad vibes" that makes your groups bigger, and you may need to do some barrel tuning.
(change or alter the barrel vibrations)

http://i122.photobucket.com/albums/o254/bigedp51/barrelvibes.jpg