From: Sarge (Original Message) Sent: 12/12/2006 6:53 PM
I get lots of questions by my Hunter Safety students and by the club members about gunsmithing. So I will try to post a message outlining and explaining common gunsmithing problems and answers at least once a week. (that ought to keep me busy for the next 50 years)
One thing that came up recently is worth mentioning as the potential for problems and I mean problems of the bad kind, is great if this little item is missed.
If you put a new stock on your rifle, make sure the inletting for the bolt handle is complete and absolutely none of the bolt touches the stock. The reason for this is that if the bolt does not lock completely but does lock enough for the gun to fire, you will have an excessive headspace problem that can end up with a face full of hot gas and needle like pieces of brass in your eyes and face. The bolt handle must be completely down on the receiver stop to have your headspace correct. If it is not touching the receiver stop then you will have a bolt that can very possibly be blown out of the gun as the push of the gas can cause the bolt to turn and release. I hope this isn't too complicated. Maybe I should explain how head space is measured.
When the bolt handle is completely down (touching the receiver frame (stop) the distance from the face of the bolt to the start of the shoulder of the cartridge is called the head space. If the bolt is not completely down, then there is more space between the bolt face and the shoulder of the chamber. When a cartridge is fired with this extra space the brass expands until it reaches the end of the chamber (shoulder) and that causes the cartridge case to stretch and the wall of the cartridge case to thin down at the base just above the cartridge head. If the head space is excessive the brass will thin down to the point that it can no longer hold the gas pressure and the cartridge case will rupture and the gas will come back along the bolt and you guessed it, hit you in the face. This is something we all want to avoid, believe me.
So this tip is to make sure you are not creating a excessive head space situations by checking your bolt handle to make sure it is touching steel not wood. One more tip, the drop-in Poly stocks need to be fitted to the action. Especially if you have a different barrel installed. I recently put a so called drop in stock and found that it was not 'drop in'. It, in fact, needed quite a bit of fitting and one place in particular was where the bolt locked into the receiver. The bolt would allow the firing pin to drop but the bolt was still being held up by plastic.
Sarge the long winded gunsmith.
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From: MSN NicknameLEWIS4289 Sent: 12/12/2006 7:28 PM
Sarge have you ever used any of the go, no go gages that brownell sells for any cal.
If so how good are they , I also, is true that the closer the headspace the better
groups being shot for a given cal.
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From: Sarge Sent: 12/14/2006 12:31 AM
I use brownells Go-NoGo gauges exclusively. They are excellent and made from some very hard steel. (I know I dropped one on my concrete floor once and it rang and bounced. And best of all did not have a dent or scratch on it)
Having minimum headspace is good for a target rifle, not too good for a hunting rifle. The last 4 rifles I made for a customer he requested minimum head space as he was going to use them for long range shooting and wanted all the accuracy he could get. Also he is a reloader and very careful about case length, using only a neck sizer rather than full length sizing. Had he wanted the guns for hunting I would have suggested he accept a .002 deeper chamber. The reason for that is for hunting guns the chance of dirt or debris getting in the gun or on the ammo is great and you don't want your rifle to jam up on the shot of a life time. The difference in accuracy would be so small that in the hunting field it would not show up. But for a long range rifle match, it would make a difference. Now as whether this rule works every time, is not necessarily true. Rifles like women come in all temperments and some very loose rifles (not women) will shoot excellent groups and I can't tell you why. If you are getting a rifle made for you it is better to start out with a minimum head space and then if you feel your accuracy is poor (AND IT IS NOT YOUR FAULT) then you can always have your gunsmith open the chamber up just a few thousands and see if that shows any improvement.
Sarge |
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