Setting Headspace

[Legionnaire]

So I've ordered a new Remage barrel from McGowen: a 24-inch 8-twist medium sporter in 22-250 Ackley Improved. Before it arrives, I've been exploring options for setting the headspace. I could buy go/no-go gauges from PTG or rent a set from Reamer Rentals.

According to PTG's web site, their gauges are cut to maximum SAAMI specs for the cartridge, whereas Reamer Rentals' gauges are cut to minimum SAAMI specs. According to SAAMI, the difference between minimum and maximum chamber length for a standard 22-250 is 0.010. My research indicates that for most centerfire rifle cartridges, the difference between a go and no-go gauge is 0.004. As should be obvious, if one set headspace to maximum SAAMI specs (1.5849), the bolt would close easily on a minimum cut no-go gauge (1.5749+.004).

So my question is, what are the pros and cons of setting the headspace to:
1. SAAMI minimum (Reamer Rentals)
2. SAAMI maximum (PTG)
3. Somewhere in the middle?

Mods: putting this in the Rifle forum for broadest input. Feel free to move to Gunsmithing if more appropriate there.

 

[someguy2800]

I don't use head space gauges when installing savage barrels. I run a piece of brass through my sizing die and use that as the gauge. I chamber that piece of brass and adjust the barrel so that there is just a tiny bit of drag when closing the bolt.

 

[edwardware]

First:https://ackleyimproved.com/headspace-and-ackley-improved-cartridges/

Convention for Ackley chambers is to set -0.004 from the parent Go, so that unformed brass is barely crush fit on the shoulder.

Since you're obviously reloading. . . it seems to me that you should also avoid setting the headspace too short for your FL die to bump to.

 

[Legionnaire]

... it seems to me that you should also avoid setting the headspace too short for your FL die to bump to.

Good thought. Thanks.

 

[edwardware]

Good thought. Thanks.

I've been slowly buying parts for 3 years intending to drop a Criterion RemAge in .223 Ack on my R700. . . I'm really interested to know how yours works out.

 

[Legionnaire]

I will definitely write it up. I'm hoping it turns out as well as the .260 Ackley I built last year. I've since moved the .260 to a Grayboe Renegade stock, so the .22-250 will start out in the Terrain.

I thought about a 223 Ackley, but decided that if I want to hotrod a .22, I'd go big.

 

[jmorris]

So my question is, what are the pros and cons of setting the headspace to:
1. SAAMI minimum (Reamer Rentals)
2. SAAMI maximum (PTG)
3. Somewhere in the middle?

If your chamber is set to minimum and the ammunition is loaded to maximum, it won’t fit.

If your chamber is set to maximum it will feed anything that is within spec.

If your chamber is in the middle it will fit half of the stuff that’s in spec.

If you reload none of it matters much.

I am likely pretty close to where someguy2800 winds up but I can do that with any chamber, even if it’s at max.

I just remove the firing pin and size the brass so the bolt handle will fall half way. When fully closed the case is being compressed. That’s the slight increase in resistance.



Only a good idea if you keep firearm and ammunition together though. Case life and how much you have to mess with them between firings are quite an improvement vs cases that are blown out and sized more then necessary every time.

 

[Legionnaire]

Makes total sense. So why would anyone choose to headspace at minimum spec? Maybe a competition gun?

 

[jmorris]

Well that rifle above has a chamber that won’t fit factory cases. The necks have to be turned, the point being to make consistent neck thickness and not be loose in the chamber, or having to move the brass around a lot in firing/sizing. A custom size die is also needed at that point too.

It’s a lot of extra work and I don’t bother for most rifles.

Only other reason I could see a minimum chamber being good is if you wanted to justify your undersize die purchase.

 

[WVRJ]

I have seen small but definite accuracy improvement with fairly tight headspace.I usually use Clymer gauges,and set up bolt guns to barely close on the go gauge after the bolt lugs are lapped.It all depends on what you want to use the rifle for.If it was a target rifle that I was going to shoot a lot,I'd run it tight.A hunting rifle that I may have to use ammunition other than my own,I would run it to the looser side of spec.With the Remage setup,you can tinker with it a little and see what works.

 

[jmorris]

I have seen small but definite accuracy improvement with fairly tight headspace.

I agree but you can get there even with a chamber that will feed ammunition loaded to max specifications. For that matter you could size cases so much that you create head clearance even in a chamber of minimum headspace.

 

[Varminterror]

If you’re reloading: As long as you set your barrel a) short enough to not rupture or excessively stretch, and b) long enough to let your die match the chamber without hitting dead stop between ram and die before it’s appropriately sized, then it really doesn’t matter.

 

[Slamfire]

I never cared for minimum headspace chambers. Most of the centerfire rifle ammunition I blew downrange was fired in NRA Highpower Competition. The ten ring was 2 MOA and you know, I never met anyone who shot 2 MOA all the way out to 600 yards. The High Master's always cleaned the 200 and 300 RF targets, but 200 yard standing is really tough, and then at 600 yards, winds are unpredictable. Given that a one MOA rifle could hold the X ring at all distances, and no one ever shot a 800-80X's, benchrest accuracy was not needed. What was needed was an rifle and load that held half the ten ring, or less, always, good ballistics, and perfect reliability in feed and extraction.

All the Highpower shooters I knew, at least the good ones, full length resized their cases and sized the case smaller than the chamber. My goal was to bump the shoulder 0.003" less than the chamber. This was good enough for 308, 30-06 and 223. If you have a case gage on the table, and you measure each and every sized case, you will find that brass, even of the same lot, fired in the same gun, the same amount of times, reacts differently after sizing.



Some brass will have their shoulders bumped back 0.003", others 0.002", and others 0.001". Might have been some with 0.000" shoulder clearance. What I wanted was clearance so that the bolt was not crush fitting rounds to the chamber, and then finding out, that the crush fitted round was hard to extract after firing. This is a primary reason I will never neck size, you need enough initial clearance between case and chamber to ensure that the brass springback is such, that after firing, there is clearance.



You start with a minimum headspace chamber and if you want your cases smaller than the chamber, you are going to have to grind off material from the bottom of your sizing die to gain clearance. So, I think minimum headspace chambers are undesirable. Maybe they are the thing for benchrest shooters, but ask yourself, when was the last time you saw a benchrest shooter shooting offhand with his 20 lb lightweight benchrest rifle? Or what are their times in the biathlon? Would skiing with an unlimited class bench rest rifle really improve biathlon times over the 20 lb lightweight class? Probably not. Accuracy without function reliability and portability is interesting and all, but useless everywhere but on a bench at the range. And therefore bench rest techniques are best left at the bench rest matches where shooters might see the differences on target.My buds who are long range champs, they all have screw ball reloading practices, mostly developed by seeing patterns that don't exist, but they are every and each one, outstanding wind readers. All of the long range shooters have sub MOA rifles, but what sorts out the winners from the pack, is wind doping and shooting when conditions are the same.

I always asked the gunsmith to ream the chamber go plus three. But if you use the maximum chamber headspace reamer, you can lubricate your cases on first firing, and you won't experience sidewall stretch

As I did on 300 H&H cases





and factory 30-06



with first time fired 6.5 X 55 cases



on new 270 Win cases



to neck sized 30-06 cases



and with 30-30 cases



It was hard to measure, but the case shoulder moved forward around 0.025" on the first firing. Without lubricated cases I would have developed severe sidewall stretching if not case head separations"




Once the cases are perfectly fireformed to the chamber, I set up my dies, with case gauges, and bump the shoulders back an average of 0.003"

 

[Varminterror]

I never met anyone who shot 2 MOA all the way out to 600 yards.

Think you need to get off of the HP range and explore the rest of the firearms world from time to time.

 

[murf]

slamfire,

will petroleum jelly work instead of beeswax?

murf

 

[Slamfire]

slamfire,

will petroleum jelly work instead of beeswax?

murf

Yes. The beeswax hair gel was on sale, and it was harder than Vasoline, which is petroleum jelly. I wanted to try something that was similar to the grease the Swiss used on their ball ammunition:



The Swiss grease ring is harder and drier than the wax ring on a toliet, so I have not found a perfect duplicate.

Any grease, or case lube will work. The case only has to feel slightly greasy. The gentleman I got the idea from, he used RCBS Water Soluble to size his M1a brass, and he never tumbled the lube off. His cases felt slightly greasy. He was able to take his 308 Win cases an entire shooting season without a case head separation, and being a cheap skate, I copied what he did, but I did not like the "booger" feel of RCBS lube. Particularly as I primed cased off the press with a Lee Autoprime.

What I did, after the cases were washed, primed, powder and bullet added, was to apply Johnson Paste Wax with my fingers. I particularly made sure I had well coated case necks and shoulders. My rapid fire ammunition I polished with a rag, because I had bolt over rides at Camp Perry in cold weather with "pine-apply" waxed ammunition during sitting rapid fire. After shooting an alibi I polished all my rapid fire ammunition and never again experienced an incident where the bolt closed on an empty, regardless of temperature.

The American shooting community has more than forgotten about lubricated cases, in fact there has been a militant denial of this period of history, but in the period when trillions of cases were fired greased and oiled, the Pedersen rifle cases were covered with Ceresin wax for lubrication purposes:



Ceresin wax dried hard, but under the pressures and temperatures of combustion, melts and becomes a lubricant. You can find Pedersen's patent on this, it is US167816

More particularly, the invention aims to improve a cartridge in two main respects: first, to provide a weatherproof protective coating for the cartridge which will enable it to be stored without deterioration for longer periods of time than heretofore; and second, to provide a means of lubrication for the cartridge to facilitate its extraction from the chamber of the fire arm when fired

I did this with my M1a ammunition because I preferred the hard coating that Johnson Paste Wax gave, it did not attract dust and did not have a greasy feel. I took one set of LC 66 cases 23 firings without a case head separation, which is exceptional, when you consider most cases develop severe case head stretch after five firings in a M1a.





At some point, I started keeping cases that failed through neck cracks and body splits, and sectioned them.





Anyway, there are plenty of suitable lubricants, water may be one of them. Melvin Johnson in his book "Automatic Arms", on page 167, recommends for those in combat, to

"1. If you have oil or graphite, smear as much of your ammunition with the lubricant....

2. If you are out of oil, water on the cartridge will help considerably......

3. If you have no water but there is an available mud puddle......

4. Failing the above, saliva on the cartridge will help measurably"

I do not recommend rolling cartridges around in mud, if it was my gun. Now if it was an issue weapon, I would not care if mud scratched the chamber, barrel, throat. As long as it went bang better.

Just remembered, the WW1 Germans coated their 8 X 57 steel case ammunition with a wax mix, so the cases would not stick in the chamber. They shot billions of the rounds. This may be where Pedersen got his idea.

 

[Legionnaire]

So here's my plan. I ordered a Clymer 22-250 go gauge from Brownell's. My research indicates that an Ackley chamber is 4 thousandths (0.004) shorter than a standard chamber, and that a standard cartridge go gauge can be used as a no go gauge in an Ackley chamber. So I should be able to screw the barrel in on a closed bolt until it contacts the go gauge, then remove the go gauge and turn the barrel in another 23 degrees (360 degrees on a 16 TPI thread is 0.063) and have a chamber 0.004 shorter than the gauge. Tighten the barrel nut, then see if I get a good crush fit with a full length sized case. Sound about right?

 

[murf]

and the Japanese had oilers on their machine guns.

done hijacking your thread, legionnaire. wish I could answer your question.

luck,

murf

 

[jmorris]

So here's my plan. I ordered a Clymer 22-250 go gauge from Brownell's. My research indicates that an Ackley chamber is 4 thousandths (0.004) shorter than a standard chamber...

.004” shorter where? With the tapers involved you need measurements relative to a datum or a diameter of reference and that trigonometry class will come in handy as the go gauge will have a different taper that the 22-250 and the 22-250 AI.



I don’t know the answer but it might or might not be as easy as what you have planned out so far.

 

[Gordon]

The way my .22-250 AI is set up is that factory .22-250 ammo goes into it OK , but I have found some makes are pretty tight , like Federal and the final closing of the bolt certainly contacts it . WW goes in with little resistance. Remington drops in . The important thing is factory ammo goes in . I wouldn't try to milk it too tight !

 

[Jim Watson]

In my brief foray into F-T/R with a Savage .308, I started out with the factory barrel and was quite content. Then NRA got worried about possibles being shot on high power targets with bipod and scope so they cut the size of the targets in half. A friend and I read up on the process of rebarreling a Savage and bought nut wrench, go gauge, and Pac Nor barrels. We wrassled off the nuts which are very tight from the factory and unscrewed the barrels.

Applying the consensus approach of the Savage board, we screwed the new barrels in hand tight against the Go gauge with bolt closed (extractor and ejector removed) then tightened the nuts. The draw force on the nut is said to pull the barrel back about a thou and a half, leaving the chamber at Go + .0015". No need for a No Go gauge. We used the Forster gauge from Midway, therefore probably a maximum minimum spec part.

It must have worked, accuracy was improved over stock, keeping us in the game with the "half MOA" (X ring) targets,
Luckily, brass shot in the factory barrel would chamber in the new barrels. Pac Nor said they had the "sniper chamber" which was SAAMI body throated for 175 gr SMK at maximum OAL.
I neck sized with no problems, no hard chambering or extraction, no case head separation, just neck size and load.

 

[Legionnaire]

.004” shorter where?

P.O. Ackley measured to the neck/shoulder joint rather than the datum line, so that's the measure. I have seen several places (here's an example) citing using a standard cartridge (in this instance a .22-250) go gauge as a no go gauge for the improved chamber. Hence my reasoning. Key will be testing for the crush fit.

But as Gordon says, not too tight!

 

[jmorris]

Key will be testing for the crush fit.

That’s the easy part, per #7 and you can get there either way. From your link the intention is to begin there vs form the case to chamber and maintain from that point.

For a comparison, if you had a minimum 1.5749” headspace dimension chamber and 1.578” ammunition, that would put you at -.0031.

 

[RussellC]

In my brief foray into F-T/R with a Savage .308, I started out with the factory barrel and was quite content. Then NRA got worried about possibles being shot on high power targets with bipod and scope so they cut the size of the targets in half. A friend and I read up on the process of rebarreling a Savage and bought nut wrench, go gauge, and Pac Nor barrels. We wrassled off the nuts which are very tight from the factory and unscrewed the barrels.

Applying the consensus approach of the Savage board, we screwed the new barrels in hand tight against the Go gauge with bolt closed (extractor and ejector removed) then tightened the nuts. The draw force on the nut is said to pull the barrel back about a thou and a half, leaving the chamber at Go + .0015". No need for a No Go gauge. We used the Forster gauge from Midway, therefore probably a maximum minimum spec part.

It must have worked, accuracy was improved over stock, keeping us in the game with the "half MOA" (X ring) targets,
Luckily, brass shot in the factory barrel would chamber in the new barrels. Pac Nor said they had the "sniper chamber" which was SAAMI body throated for 175 gr SMK at maximum OAL.
I neck sized with no problems, no hard chambering or extraction, no case head separation, just neck size and load.

Which Pac nor barrel did you use? Length and twist? I need a good barrel for my Savage 12FV .308! Much appreciated,

Russellc

 

[Jim Watson]

We got 28" (Their longest without extra charge.) 10 twist for about any bullet we cared to try, THREE groove.
My more experienced friend had signs that the three groove barrel would last longer than more conventional six groove.
I don't remember the profile number, something close to the factory varmint so we wouldn't have to enlarge the barrel channel in the stock.