Tight chambers in bolt action rifles, risk problem?

[His lordship.]

I have heard that tight chambers in rifles are good for accuracy, but can be a problem with ammo that is corroded, not resized properly, or under dirty conditions such as in the trenches in WW 1.  

I have a CZ 550 bolt action rifle in 30-06 that seems to have a tight chamber as we tried to use a .32 cal. ACP pistol cartridge insert modifier for an experiment and it would not fit into the chamber, the guy who let me try it designed/markets it as an option for people to shoot the pistol round in their bolt guns.  This rifle is very forgiving for me when I handload my ammo using a Lee loader as it chambers everything I put into it smoothly, other rifles I have handloaded for can be temperamental.

Another shooting fellow I know went prairie dog hunting with 2 of his custom rifles with tight chambers, one is chambered in .223 Ackley and I forget the other one.  While shooting he had one of them jam the bolt tight freezing up the action, and had to have a gunsmith remove the bolt.  The other one blew up leaving the bolt intact, but the whole receiver/bolt area assembly was broken.  The 2 other shooters in his party used .223 factory rifles with factory ammo, no problems with them.

Are tight chambers a sensitive item on a gun to where they are unsafe, or prone to breaking down?  The guy who had his guns malfunction buys very good equipment, and I am sure this was a very expensive and unfortunate trip for him.

Thanks.

[gunnut69]

Target rifles are often tight chambered on purpose.  It was thought to enhance accuracy but fireforming brass to the chamber and only neck sizing will accomplish the same thing.  There only difference is the amount the neck expands in firing.  A tight neck can be used to eliminate nearly all expansion of the case neck.  Doing this can raise pressures drastically if the brass especially prepared for the particular rifle is not used.  As far as blowing up rifles I wouldn't blame the chamber dimensions.  These rifles had to have been using handloads and my guess is that is where the problem arose..  An overload will usually not destroy a rifle but if the rifle is a well built custom it will not generate the pressure signs most loaders look for.  This encourages overloads and eventually the rifle, continually overloaded, simply fails.  Or perhaps it was a case of a simple error.  The wrong powder can create tremenfous pressure spikes and cause failures.  Usually the case fails and vents high pressure gases.  Of course these pretty much destroy the rifle, although the main metal work is usually left intact.  The cartridge adaptors failure is probably due to it's being out of spec.  Chambers as most manufactured items are made to tolerances.  This means the chamber in your rifle may be on the tight side of the tolerance range while the adaptor may be on the large side.  It should be possible to polish the chamber adaptor to allow it to function in your rifle if you so desire..although generally speaking my experience shows these adaptors as being not very accurate.  A light load can be devefloped for you rifle and will usually work much better than these adaptors..

[Judson]

All the rifles I build are head spaced to minimum tolerances, meaning you will feel the bolt snug up against a sized case when the bolt is closed.
If you are a reloader and want the best in accuracy this is where you will find it.   A rifle chambered like this will not accept a Go Gauge, or possibly some factory ammo so it is not for every one.    For the non reloader all that is required is around .002" of head space which means a go gauge will still not chamber or be tight but factory ammo will work fine.
   As for your friend either he screwed loading his ammo or he had better find another gunsmith that knows what he is doing!!!

[johnboyncsu]

Judson,

I have a savage 110 in 270 and it feels real tight when chambering factory winchester ballistic silver tips but is a lot smoother with factory remington core loks.  Could this be a head spacing issue?  Both of the bullets will shoot fine but I'm just curious why the bolt could be so much tighter with different factory ammunition.

[gunnut69]

Judson--  I must disagree with you about the headsapace setting..  All you accomplished is to make the rifle incapable of using some factory ammo.  The exact same effect can be obtained by chambering the rifle normally and neck sizing only when reloading the brass.  Tight chambers in match rifles doesn't refer to the headspace but the neck diameter of the chamber.  The relationship between the cases neck wall thickness, bullet diameter and the diameter of the neck in the chamber is what is tight.  Usually these necks are cut undersized and the cases neck is turned to fit.  There must be enough clearance between the neck and the chamber to allow it to expand and release the bullet but as little as possible to promote better axial alignment of the round in the chamber.  If the cases in a normal chamber are neck sized only then they will have exactly the same tight tolerances as your custon chambers and the rifle will still handle factory ammo just fine.  All you've accomplished by such chambering is to make the owners life a bit more difficult than need be and limit ammo availability..  All chambers should accept a go guage..  There is no viable reason for them not to.

[Mikey]

Chris D:  I once had a Rem 788 that had such a tight chamber I would have to prepare my reloads with four different case sizing steps to get a reloaded round to chamber.  Factory stuff was no problem but handloads - that was the reason I finally got rid of the gun.

As to that chamber insert business.  I found that with steel chamber inserts, once it has been fired in one chamber it may not fit others - I used to play with 30 Luger and 30 Tokarev inserts for that 788 and when I tried to use the inserts in two other rifles they wouldn't fit.  I believe that once an insert is used, it expands to fit that one chamber and probably won't fit others.

I've known a number of shooters with tight chamber rifles but haven't ever heard of a blow-up due to the tight chamber.  Mikey.

[His lordship.]

The guy with the two malfunctioning rifles is a fellow I used to shoot with alot, but I have been mostly shooting weekdays for the last 2 years, so have not seen him.  I will ask for more info when I do, the bad hunting trip was clearly painful to him, so will have to see.  

My prior exposure to chambering problems in rifles have been with the ammo as the main culprit, not the gun.  But then again, I only use factory standard rifles.  The info on the .32 cal. ACP insert is helpful as that makes sense that the device would expand differently with individual rifles.

One area of warning to collectors and shooters is the early unmodified military bolt action rifles.  I had a Japanese Type 44 carbine (made around 1912) and an early production Chilean Mauser model 1895 that I handloaded for, and these guns were very tight in the chambering for the handloads, not a problem with the factory loads, but as soon as I used my handloads, failure to chamber was a risk.  I had read that due to the muddy conditions in WW 1, many British rifles had their chambers reamed out to be more forgiving, and my later production military bolt actions were nice for handloading.

[gunnut69]

Just a little note..  I've never seen a military bolt rifle with a tight enough chamber to cause chambering problems..  The problem likely was with arsenal rebuilds.  Many of these old rifle have been rebuilt at least once and many more than once.  The replacement barrels are turned to size, threaded and short chambered.  That means they will screw on the action just fine but may require a finish reamer be used(by hand) to allow a go guage to work thru the action.  I have seen instances where the 'armorer' simply tried a nogo guage and if the bolt wouldn't close, sent the rifle on it's way..  The result may be a chamber that's too short!  A tight chamber refers to one that is smaller in diameter.  They somewhat enhance accuracy by allowing less slop in the cartridge/chamber fit.  A chamber that has too little headspace is simply incorrectly chambered..  The last I fixed was an '03A3 that a friend had bought at a gunshow.  The chamber would chamber ammo only with difficulty.  I checked and it would not accept a go guage.  I deepened until it would close on a go guage and all was normal..  Don't confuse a headspace problem with a tight chamber.  Military rifles almost always have loose chamber tolerances to allow positive functioning with dirty ammo or fouled chambers..

[Judson]

As far as Remington ammo chambering easy and Winchester tight I think that if you check the case dimensions you will find the Remington ammo a bit on the small side compared to the specks such as can be found in the book  Cartridge Conversions, which gives the cartridge "print" dimensions.    Winchester ammo is usually closer to specks and in general Federal is right on.    Why this is I am not sure other then quality control or the fact that Remington makes semi autos which work best as far as reliability with "loose" brass
    A Go gauge is set at dimensions which allow for factory tolerances and safety.    Most of the major factories use a field gauge and a go gauge when inspection their rifles as the ultimate in accuracy is not of top priority.    In a lot of super accurate rifles like the older Sako rifles for example you will not close the action on a go gauge.    For the ultimate in accuracy you want minimum chamber tolerances and this means using a sized case or a gauge made to these dimensions.    A person who wants the best accuracy is not going to run factory fodder nor want to fire the mass produced stuff to get cases to neck size.    Besides with minimum chamber dimensions your brass lasts just as long with full length sizing.
    For example, I set a Savage .22/250 up for a guy you may know who goes by Woodseye.   Before tightening it up and bedding it shot .78" at best, after bedding right around.647"   After correcting head space slop and chamber dimensions constant .132 to .135" groups minus bore bullet diameter.   Tight is right and by the way this rifle will shoot most factory ammo no problem.
  One other point the difference between a bolt closing on a go gauge and a no gauge is the difference between good and poor accuracy.    If the bolt closes on the go with no feel how do you know it is not .001" off closing on a no go?    This is why I chamber with a lathe and a micrometer.

[gunnut69]

By using a go guage and a nogo guage you are setting the headspace to the specs for that particular caliber..  By setting headspace too tight or below normal you have not materially tightened the critical chamber demensions the radial demensions.  Headspace is simply a measurement from a datum line on the case somewhere to the boltface..  The circumferencial measurements are much more important than headspace.  Even they can be negated by simply fireforming a case to the chamber it is to be used in..  A proper neck sizer will then give a better fit than any reamer or lathe..  Most benchresters, the real accuracy nuts, fireform and necksize in specialty dies.  I would be the accuracy gains you quoted were probably more from a chamber that was straighter than it was before you recut and that is nearly benchrest quality accuracy from a low priced rifle..  As to a brand of brass being different I will admit I've not done any extensive study but have found that the size of the case is more important in it's relationship to another case of the same brand and batch than it is to some other brand.  Most begining reloading instructions will tell you the segregate by brand..  Using a proper guage is also a very good idea.  Cases can be easily deformed by the camming action of a bolt action rifle.  This will give bad readings..  There are some limited exceptions, where the headspace is set by a rim or a belt but for the most part, use a guage..  I still see no gain from setting the headspace to short.  The first firing of a case in a chamber will give you a case precisely fitted to the chamber minus a bit of springback...exactly as will the case in your too tight chamber, with an exception, yours won't allow some factory ammos use..  That's a real benefit all right!

[Judson]

Gunnut69, I am not saying too short, just to what the dimensions should be not mass produced tolerances like the factory.    For the best accuracy one must tighten up all the factory slop that mass production creates.    I am not knocking the factories as they could do the same thing but then prices would go up substantially.    That as you know is the difference between custom and factory.    If you look at a go gauge and mike it you will find it to be, depending on the cartridge from .002 to .006 over print chamber dimensions and a no go from .004 to .006 over this.    For a hunting rifle .002 over case dimensions is plenty and will result in a tight go gauge and yes you are right in that head space is only one factor in chambering.    It is not just the head space but all the dimensions that have to be right.   Tight head space and a loose chamber or neck is defeating the whole concept.    This is why I mike a reamer when I get one and throw out the worn out ones, use a floating tool holder so the pilot centers on the bore and all the good stuff.    That is also why I lap the lugs square the action and "blue print the action.    The guns I build will shoot under 1/2" at 100 yards and again you are right in that it is not one dimension it is all the dimensions that give top accuracy.    Really what it is about is blue printing like one does with a race engine.    Yah I used to do that too then I got, well, smarter but not nessarily smart.

[gunnut69]

Judson-I guess it's all about care.  A custom rifle has the care put into it and factory rifles don't. The past few years some of the juck I've seen produced in this country has me a little scared..  I've bought a few of the CZ rifles and have been impressed..  Not custom quality but awfully good.  I bought a 537 FS in 22 Hornet(a reloaders nightmare) and it shot sub 1 inch groups, regularly, with factory ammo!!  It even has shown a liking for the little 40 grain Hornadays.... As for cars, well, I too had that phase..  2nd car I owned was a '63 corvette convertable with a nice hardtop.  Only car I've ever owned I wished I hand back..  I always tried to define a custom rifle as one that works the very best it can..

[Judson]

You have good taste in both cars and rifles.   We have sols several of the 550 magnums in both .416 and .375, the triggers needed a bit of adjusting and the customers wanted them bedded as on some of the forums people have mentioned the big mags developing cracks.    But what a rifle for the money, for a factory rifle they are hard to beat!