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Headspacing ? for Gunsmiths

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Unread 06-16-2005, 01:49 AM
Gold Member
Join Date: Mar 2004
Location: Germany
Posts: 658
Re: Headspacing ? for Gunsmiths

headspace. one of my favorite subjects.
As Bill needs to put the rifle on the shelf and sell it as new then the CHS needs to be within the recognised SAAMI specs. For it to be other wise would be leaving the business open to liability issues. In the absense of availability of head space guages i'd take it to the nearest gun smith and have the head space measured and if need be adjusted to withing specs, its easy to do on a savage due to the barrel nut.
Now if Bill was keeping the rifle him self, I would suggest he head space of the cases he would be using in the rifle. Rifles that are head spaced to match the ammo that they are using (which is basicaly what is happening when you use once fired brass, providing it was fired in the rifle its to be used in) are more consistently accurate than rifles with over sized, on the outer edge of the SAAMI tollerences.
My own personal rifles are set up so the case is ever so slightly squeezed between the shoulder and the bolt face when i close the bolt. I use one type of ammo/case in them and the CHS is set for that. Of course variations in factory loaded ammo mean i measure a number of cases in a batch and take the average, up to now with Lapua, Norma, Hornady and Black Hills, the variation in factory cases has ben negligable, almost nil.
Customers rifles i set to the exact minimum SAAMI spec which still means that all factory ammo can be chambered as i have yet to fin any factory ammo that wasn't slightly under the minimum spec. Unless the customer specificaly wants it done otherwise. In this case I engrave the CHS length on the barrel. Worst case scenario is a rifle that is on the larger side of the tollerance and ammo that is on the small side. This leads to innacuracy, case stretch and in some cases case separations. Ive seen several Remington 700's that where from factory with well over the max CHS spec, which leads me to belive that there are guages and then there are guages.
To tight a head space isn't nesseceraly a major danger problem, if the bolt won't close on a case, unless you realy force it shut, then you aren't going to encounter problems (exept that you can't chamber a round).
Too large a head space is a problem and can be dangerous. best case is inaccuracy as the case is either held forward under the force of the plunger ejector, depending on the case width compared to chamber width, the case can be levered side ways slightly, pivoted on the extractor putting the bullet out of true with the centre line of the bore. On firing the case comes slamming back,(and the bullet wobbling forward) not giving the best start for the bullet to enter the rifling, hammering the bolt lugs and streching the case and ruining any accuracy.
Well far more in depth than the question required, but usefull i hope all the same.
if you are head spacing off a case / live round remove the bloody firing pin before hand !!
You would be better to remove the bullet from the case as some bullets in certain ammo put in certain chambers will lodge in the rifleing before the shoulders of the case and chamber contact, in this case you would end up with way over sized head space.
I know of a certain rifle. a 6.5x55. The chamber was cut with a mis marked 6.5x57 chamber reamer. This was a major screw up by the reamer manufacturer or some idiot re etching the reamer for a start.( Hobby Gun Smiths and Professionals alike, beware, Buy your reamers from a reputable place !!) The head space was measured(if you can call it measured as no measure ments where done, off some Norma match ammo. The ammo had long long bullets loaded in it and the barrel was made with a tight/ short throat. The CHS was done in the method of a piece of paper on the bolt face and the case in the chamber. As you can imagine, the chamber was 2mm too long to start with, the bullet was touching the rifling and the case shoulder was a ways away from the chamber shoulder.
The rifle was test fired,firstly with normal hunting ammo,which had a shorter bullet than the match ammo, the firer reported the absence of any recoil for the first few rounds and then a couple of miss fires followed by a strange sound, difficult bolt opening and a separated case.
The first few cases had managed to stay in one piece, apparently bieng held on the bolt face whilst bieng fired, its questionable as to wether the bullet, bieng way away from the lands, slamming in to the bore had counter effected the recoil, acting a bit like one of those mercury recoil reducers, would account for the lack of recoil. The miss fires would have been the round further in the chamber, not held by the extractor, firing pin couldn't reach the primer properly. Anyway, then a case separation occured.Luckily No harm was done to the shooter / hobby gun smith.The bolt logs where burred but not badly dammaged.
When i got the rifle to look at and the story un folded it became mostly apparent what had happened. I took the rifle appart, bleaned up the bolt lugs, inspected the thing thoroughly and put it back together, whith correct CHS measurements, the thing shot very well there after, the guy was lucky, that had to be some way out fire forming excersize by accident.
Anyway the moral of the story is, don't mess with what you are un sure about, if you are unsure, take it to a professional gun smith to have it checked out, beware of reamers bought on ebay, don't just rely on cases for CHS, measurements should be taken also. Wear eye protection whilst shooting.
cheers Pete
Occupying the British Zone.
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Unread 06-16-2005, 07:22 AM
Silver Member
Join Date: Jan 2005
Posts: 398
Re: Headspacing ? for Gunsmiths

Pete, brings up a vary useful point about case extractors and head-space. The Remington extractor offers no real protection against excessive head-space. Even the lowly hook extractor offers some. The claw affording the best. I once fired 10 rounds of 7.62 NATO in a National Match Garand chambered for 30-06, thanks to a National Guard member handing me my ammo in the clips while shooting prone rapid fire. My first clue something was amiss was the strange looking brass laying next to me that for all the world looked like rimless .410 shells. The second clue was the Maggie's draws waived in front of my target by the pit crew. [img]/ubbthreads/images/graemlins/grin.gif[/img]
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Unread 06-16-2005, 07:37 AM
Bronze Member
Join Date: Nov 2001
Location: Bradley, Oklahoma
Posts: 39
Re: Headspacing ? for Gunsmiths

Chris is probably right, since I know who Bill works for - send it back to Savage and let them worry about it.
I suggested the new case and solder method to see what the headspace is.
Send it back and you can sleep better at night.
If nothing else you have gained some knowledge about headspacing and that's what this board is all about.

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Unread 06-16-2005, 08:55 PM
Join Date: Dec 2004
Location: El Reno, OK
Posts: 1,922
Re: Headspacing ? for Gunsmiths

Thanks for all the info guys.

We've got a gunsmith that does some work for us. I think I'll call him in the morning and see what he would charge. Who knows, it may be cheaper than paying freight to send the gun back to Savage.


PS- I did learn alot about headspacing!!!
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Unread 06-16-2005, 11:26 PM
Bronze Member
Join Date: Apr 2005
Posts: 33
Re: Headspacing ? for Gunsmiths

Now if we could get you to learn about a good football team.
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Unread 06-17-2005, 08:33 AM
Join Date: Dec 2004
Location: El Reno, OK
Posts: 1,922
Re: Headspacing ? for Gunsmiths

Are speaking of USC or LSU?
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