brass length vs throat length
- Thread starter 1-trident-1
- Start date
- Location
- Western Manitoba
So, some confusion on my part. The chamber is cut with clearance for the neck of the case - that neck clearance needs to be longer than the brass case will grow upon firing. That is why we trim our brass necks. On the other hand, what I thought was the "throat" is that portion of the barrel, ahead of the neck clearance area, but before the lands start. The "throat" is the size of the bullet, or maybe a thousandth or so over, usually matching real close to the bottom of the grooves. I have some rifles which have only a few thousanths of "throat" and some that have at least .375" of throat. I have read of target shooters "chasing the lands", as the start of the lands erode. I am not sure I have heard of the "throat" eroding??
Use the gauge below to find actual chamber length and then trim .010 shorter.
SINCLAIR INTERNATIONAL - Sinclair Chamber Length Gage
https://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx
The Sinclair Chamber Length Gauges are designed so the handloader can determine the true length of his rifle's chamber when measuring from the bolt face to the end of the chamber's neck. This measurement will tell you how much excess case length your chamber may have over published trim lengths in reloading handbooks.
The Sinclair Gauges are inserted into a fired, unprimed shortened case and then chambered into your rifle. The insert pushes back into the case when it contacts the end of your chamber. You then extract the case and measure the overall length. The gauge is made of 12L14 soft steel so it will not damage your chamber. Step-by-step instructions accompany each gauge. The gauges can be used over and over again.
The differences between published trim lengths and the actual length of your chamber can be quite significant. You could be over trimming your cases by .030 inch or more.
NOTE: The 22 caliber gauge will not work on thin-necked cases such as the 22 Hornet, 218 Bee, or cartridges based on these cases. The 30 caliber gauge will not work on teh 30-30 Winchester. None of the gauges listed will work on tight-necked chambers except for the G-243T. Should not be used in handguns, semi automatic rifles, lever actions rifles and pump action rifles.
SINCLAIR INTERNATIONAL - Sinclair Chamber Length Gage
https://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx
The Sinclair Chamber Length Gauges are designed so the handloader can determine the true length of his rifle's chamber when measuring from the bolt face to the end of the chamber's neck. This measurement will tell you how much excess case length your chamber may have over published trim lengths in reloading handbooks.
The Sinclair Gauges are inserted into a fired, unprimed shortened case and then chambered into your rifle. The insert pushes back into the case when it contacts the end of your chamber. You then extract the case and measure the overall length. The gauge is made of 12L14 soft steel so it will not damage your chamber. Step-by-step instructions accompany each gauge. The gauges can be used over and over again.
The differences between published trim lengths and the actual length of your chamber can be quite significant. You could be over trimming your cases by .030 inch or more.
NOTE: The 22 caliber gauge will not work on thin-necked cases such as the 22 Hornet, 218 Bee, or cartridges based on these cases. The 30 caliber gauge will not work on teh 30-30 Winchester. None of the gauges listed will work on tight-necked chambers except for the G-243T. Should not be used in handguns, semi automatic rifles, lever actions rifles and pump action rifles.
Throat erosion happens. Doesn't matter if your leade close or not.
Back in the day, companies like Weatherby purposely cut very deep throats to create a condition called "freebore." This was done to alleviate initial pressure spikes. My Tikka T3 has a very deep throat but tolerances are also very tight and it doesn't effect accuracy. If tolerances are sloppy, accuracy can be dismal.
Usually with the amount of erosion Gandrite mentions accuracy falls off slowly. If you're a match shooter, it depends on how close the tolerances of your chamber are and case neck thickness. When I shot Hunter Bench Rest my rifles had very tight chambers with .002 thou total clearance around the necks of my cases. I purposely loaded my bullets out so that they would contact the leade and be pushed back into the case neck. That saved a lot of measuring and fooling around. I WOULD NOT SUGGEST THIS PRACTICE with and OFF THE SHELF HUNTING RIFLE. The tolerances are just to sloppy. You might be able to get away with it with neck sized only cases. Also, the bullets I was shooting had thin J4 jackets and only weighed 130 grains. (30 cal, 308Win) That extra velocity came in very handy at 300 yards.
Older cartridges used to have very long necks. This supposedly helped with accuracy by holding the long for caliber bullets straight while they entered the leade when fired. Throats in those times were notoriously different.
The old rule of thumb is .005 off the lands for best accuracy. Some rifles with chambers cut to tight tolerances don't care how far the ogives are from the lands.
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Back in the day, companies like Weatherby purposely cut very deep throats to create a condition called "freebore." This was done to alleviate initial pressure spikes. My Tikka T3 has a very deep throat but tolerances are also very tight and it doesn't effect accuracy. If tolerances are sloppy, accuracy can be dismal.
Usually with the amount of erosion Gandrite mentions accuracy falls off slowly. If you're a match shooter, it depends on how close the tolerances of your chamber are and case neck thickness. When I shot Hunter Bench Rest my rifles had very tight chambers with .002 thou total clearance around the necks of my cases. I purposely loaded my bullets out so that they would contact the leade and be pushed back into the case neck. That saved a lot of measuring and fooling around. I WOULD NOT SUGGEST THIS PRACTICE with and OFF THE SHELF HUNTING RIFLE. The tolerances are just to sloppy. You might be able to get away with it with neck sized only cases. Also, the bullets I was shooting had thin J4 jackets and only weighed 130 grains. (30 cal, 308Win) That extra velocity came in very handy at 300 yards.
Older cartridges used to have very long necks. This supposedly helped with accuracy by holding the long for caliber bullets straight while they entered the leade when fired. Throats in those times were notoriously different.
The old rule of thumb is .005 off the lands for best accuracy. Some rifles with chambers cut to tight tolerances don't care how far the ogives are from the lands.
TURF THE LIBERALS IN 2019
If you can't vote CPC, stay at home in protest.
I don't believe that you are the one that is confused, the OP seems to be the one that is confused as to the definition of the throat.
Use the gauge below to find actual chamber length and then trim .010 shorter.
SINCLAIR INTERNATIONAL - Sinclair Chamber Length Gage
https://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx
The Sinclair Chamber Length Gauges are designed so the handloader can determine the true length of his rifle's chamber when measuring from the bolt face to the end of the chamber's neck. This measurement will tell you how much excess case length your chamber may have over published trim lengths in reloading handbooks.
The Sinclair Gauges are inserted into a fired, unprimed shortened case and then chambered into your rifle. The insert pushes back into the case when it contacts the end of your chamber. You then extract the case and measure the overall length. The gauge is made of 12L14 soft steel so it will not damage your chamber. Step-by-step instructions accompany each gauge. The gauges can be used over and over again.
The differences between published trim lengths and the actual length of your chamber can be quite significant. You could be over trimming your cases by .030 inch or more.
NOTE: The 22 caliber gauge will not work on thin-necked cases such as the 22 Hornet, 218 Bee, or cartridges based on these cases. The 30 caliber gauge will not work on teh 30-30 Winchester. None of the gauges listed will work on tight-necked chambers except for the G-243T. Should not be used in handguns, semi automatic rifles, lever actions rifles and pump action rifles.
our American friend comes through with what I was seeking. yes I did confuse the terminology, but I also learned more than I was seeking, thanks to all the supporting replies.
