View Full Version : Headspace Differences in Three .30-06 Rifles

05-02-2005, 11:55 PM
"Headspace" is a term all new handloaders must confront, but most of us old f---s have learned to deal with it as a matter of routine.

I had an interesting demonstration of its influence once again just this afternoon.

Loading up a bunch of .30-06/311299 for the Nevada Shoot, I was using a new RCBS Small Base sizing die which I picked up to load ammo for my Garand. I've loaded MANY rounds for Garands and other .30-06 rifles with a standard die, but I decided to go with the SB anyway.

So....I set up the dies, and checked the first cases with a Wilson case gauge, which has the maximum-minimum surfaces machined on each end to indicate how well one's sizing die is adjusted, and also to gauge case length. The first cases were just about right, being between the max/min dimension "shelves" on the gauge, so I commenced turning out ammunition.

About 120 rounds into the run, it occurred to me that it would be a pious thought to actually check how the rounds would fit in the rifles....three rifles, to be exact. The differences in the chambers were immediately apparent. In my Model 700 BDL, the rounds fit with just a nice wee bit of "feel" as the bolt cammed into lockup. In the Garand, they were a bit snugger, and this is DEFINITELY NOT a good thing, as rounds for these rifles must chamber freely to minimize any slam-fire possibilities. In the '03 Springfield, it took serious effort to get the bolt locked.

So, I have 120 rounds which fit the 700 about perfectly. Since the sizing die was screwed down tight enough that it took a definite "bump" for the ram to make full travel, I had to find a route to size cases for the other rifles a tad more than the setup was giving me. I tried an assortment of shellholders and found a couple thousandths' difference among 'em, but not enough to give the sizing I wanted. Taking the "thinnest" shellholder, I ground some material off its top until I did get enough extra sizing to do the job for the Garand and '03. Even when the maximum of sizing is applied, bumping the die hard on this altered shellholder, the cases are just at the "minimum" dimension on the case gauge, and now the rounds chamber freely in both rifles. That is, I can't go BELOW the minimum shelf, meaning that I'm not producing rounds with excessive headspace. Rather, they are on the short side of the normal tolerance of headspace range, and now fit very nicely in the chambers.

The altered shellholder is CLEARLY different from the others in stock, so there'll be no problem sorting out which one I need for the more-extreme sizing. Come to think of it, I'll store this shellholder in the same box as the SB die for future reference.

My original set of RCBS dies gave no such dimensional troubles. It's just the addition of the one new sizer which led to this, and I suspect the die is well within tolerance, as shown by the good fit in the Remington. I DO find it curious that the two military chambers are tighter-headspaced than the commercial one in these rifles, but "facts is facts". I woulda thunk it'd be the other way around...looser military chambers. BTW, the base diameter of cases from the SB die is about .003" smaller than cases sized in the "regular" die.

05-03-2005, 12:12 AM

Was this with the SB die? If so it sure isn't small basing them very well.


mike in co
05-03-2005, 12:27 AM
bruce...i know you got a ton of loading experience behind you, but do not follow the blind in sizing for your guns.
reliable sizing in a semi-auto is as much a case of clean as sizing.
i size to 1-2 thou under chamber length AND only use a small base die for the first size( from someone elses chamber). this works for four ar-15s (223) and an ar-10(308). THE SMALL BASE CAN CAUSE THE SHOULDER LENGTH TO GO LONG BY FORCING MATERIAL IN AND UP.
my custom ar-10 used for benchrest gets next to zero shoulder bump....

overworking brass by over(under) sizing is why lots of brass fails early.
i have an article on 308 brass going over 50 reloads WHEN PROPERLY SIZED.

by the way my win mod 70 ammo is a tight bolt close in my 03-a3......

05-03-2005, 06:48 AM
For wildcat rifles like 6-284 I cut the chamber .001 SHORTER than the factory brass, I then use a shellholder surface ground .002 to bump the shoulder. I did notice that tempering (annealing is technically taking to dead soft, tempering is making softer but not dead soft) the necks changed the shoulder bump on 22-250AI quite a bit.

The Redding Competition shellholder set is marked for the amount shorter they are than stock shellholder (their advert on them would sort of lead you to belive they are LONGER but actually they are shorter)

Personally on the garand I feel slamfires are caused by using non milspec primers or high primers but I still prefer to have .002 bump because it is easier on any type of action than having to cam a too long ctg. into battery. This puts lots more wear on locking lugs than proper ctg. fit with .001-.002 shoulder bump.


05-03-2005, 07:18 AM
My '03 and '03A3 have much tighter chambers than my M70 30-06 does. Is this the norm? I would have thought that a military rifle would be more generously chambered than a commercial rifle.

05-03-2005, 09:05 AM
I'll take a W.A.G here (Wild @ssed Guess) that the mil rifles they used the reamers as long as they could before making new ones (re-sharpening can make them smaller) , so the range of dia encountered may be larger, and that Win holds their chambers more to the saami max.

saami didnt even exist back when the 03 and 03A3 was made did it ??


mike in co
05-19-2005, 12:00 PM
as i stated the ammo handloaded for my m70 is too tight in my 03a3.
i had no plan to pull all this ammo to resize the cases.......

i took a '06 fl sizing die and opened the neck to larger than the current neck dia of the loaded ammo, hand lubed the body of a loaded round, and with the die several turns up from bottomed out, i sized, then tried it in my 03a3.. repeated, moving the die down in 1/4 turns, till the ammo was a snug but smooth bolt closing fit.

it took very little sizing to get the ammo to fit in the 03a3.
the die was an easy 3-4 turns up from the shell holder.
the 03a3 chamber was tighter in the top half of the case, not the shoulder, and not the base.....

05-19-2005, 12:14 PM

Didn't they have stargauged barrels and national match 03 rifles? They might have thought building an accurate rifle with the Springfield rather then a loose chamber easy functioning one.

Most all the Springfield 03's I've encountered didn't have sloppy chambers.


05-19-2005, 12:45 PM
They did make NM springfields but I'm not the springfield expert that could tell you if they used a differant chamber or not.


05-19-2005, 01:59 PM
From what I've heard they stargauged barrels and marked the real good ones.


05-19-2005, 07:40 PM
Headspace differences in 03 and 03A3 rifles probably comes more from the bolts than the chamber.

My mentor who has long passed on, told me of going to the Army armory back in the 30's with 03. The Ordance non-com took his rifle and sat down with a box of bolts and a headspace gage. When he found one that gave a minimum headspace, he handed it back with the statement that is would now shoot like a match rifle. He droped the old bolt back into the box.

My 03A3 was an ROTC drill rifle before I came to me. The bolt had the firing pin hole welded shut. At a gun show I meet a fellow who had a couple of dozen new REmington 03A3 bolts for sale at $3.00 per. I took my headspace gage and rifle and found one that gave a tight headspace. I was suprised how much difference there was in that collection of bolts from the same maker. The rifle shoot like a house-a-fire.

BTW...Those Wilson gages are true jewels and can provide a host of information with a little creative use.

05-19-2005, 07:50 PM

That sounds pretty good and makes alot of sense to me. My first 03 was an arsenal rebuild. It was an 03 Remington action with a new 4 groove barrel on it. I took it to a gunshop in Denver where one of the owners was a WWII vet, plus a collector, and pretty knowledgeable on military rifles. He took my rifle and got his headspacing gauges out, but first he said that most arsenal would set it up to the bolt will just close snug on a go gauge, and that the bolt handle should go down halfway and stop on a no go gauge. Then he gauged it and it was exactly as he had said. He was convinced it was an arsenal rebuild. He said since it didn't match that collectors would be too interested in it, but he said it had to be one heck of a shooter. Boy was he right, the best one I ever had. Like a dummy I sold it years later.


05-20-2005, 04:15 AM
.............I don't know if any checking of the barrel via the armory's Starguageing routine included the chamber or not. All I ever recall hearing about was bore and groove, and that would be the barrel exclusive of the chamber.

There was no Sammi at the time the 1903 series rifles were in production, and since the 30-'06 was a government developement, THEY invented the specs and Sammi would have had to copy it from them anyway.

My 1903A1 has a throat of .309" and a tiny smidge. If I tried to chamber a slug sized .310" it would be hard chambering due to lead scraping back on the boolit, or even the boolit getting pushed back into the case a bit. The caselength using a FL sized case is fine as I don't own any small based dies.

The Remington 1917 I just got shooting had been fed FL sized FC once fired cases and they show bright markes on the shoulder and base from being wiped as the bolt was operated. Obviously a bit shorter chambered or more tightly headspaced then the Springfield. I did try ammo I had on hand loaded for the 03A1 and there was no chance it was going to chamber short of using a mallet on the bolt handle.


Bob S
05-20-2005, 07:23 AM
The star gage measured only groove diameter, and the readings can be very subjective: two different "operators" can get very different results. Springfield and all of the WW II barrel contractors went to air gaging about 1942.

Bob S.

05-20-2005, 10:34 AM

Or it might be that your sizing die isn't bringing the case into specs. Sounds like it does for your 03 but not the 1917. One way to find out is with a new factory round. Does sound like the 1917 has a tighter chamber, no doubt there.

Bob S

I only meant that I think there was more care or gauging in building the 03 , or maybe the Americans watched their machining and assembling more then other countries. That's not to say our rifles are the best. It really doesn't make sense why the 03's chambers are tight for a military rifle.