Hi all
I know that with f standard you are constrained to using 308win and 223rem, but are there any limitations as to chamber variants, that is neck turned chambers? Also looking for info as to what chambers are being used and free bore length for the 308?
Cheers
Chamber Specs
Moderator: Mod
Theres nothing in the SSRs http://www.nraa.com.au/pubs/SSRs.pdf about chamber sizes but there is about ammo.
Have a read of the ammo section and decide which projectile you are going to use and get a reamer to suit. I would suggest if its 308W that you will be using to go with the Australian made BJD in the HBC (High Ballistic Coefficient) bullet.
Good luck in F-Standard its a good choice and very competitive.
IanP
Have a read of the ammo section and decide which projectile you are going to use and get a reamer to suit. I would suggest if its 308W that you will be using to go with the Australian made BJD in the HBC (High Ballistic Coefficient) bullet.
Good luck in F-Standard its a good choice and very competitive.
IanP
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mike H
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Re: Chamber Specs
Steve 2141 wrote:Hi all
I know that with f standard you are constrained to using 308win and 223rem, but are there any limitations as to chamber variants, that is neck turned chambers? Also looking for info as to what chambers are being used and free bore length for the 308?
Cheers
Probably best to consult a gunsmith that is known to perform good work on target rifles, and even better if the said gunsmith is a target shooter.
The ,308 I use for F/class, is also used for Match Rifle with 200 grain SMK`s, so has some clearance, Fired winchester cases measure .342", loaded rounds are .333". Loaded HPS cases are .336". I measured a fired case from the club Omark, it was .343". I have no experience with neck turned style chambers, I believe that in TR and F/class standard, rifles should chamber and fire aproved factory rounds.
Mike.
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Woody_rod
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This is an interesting question, which I posed to a few people here and elsewhere. My understanding of the rule (20.2.1 - for F Standard NRAA SSRs) simply states that the rifle must be chambered for 7.62 x 51 NATO (308W) or 5.56 x 45 NATO (223Rem).
This does not allow for tight necks or chambers, as they would not then be able to chamber one of these standard rounds.
If asked for a way of testing chambers, the answer can be quite simple: just measure the case that comes out of the rifle. The fastest way would be to use a SAAMI or CIP test gauge, like a complete round, only made from steel, and ground to close tolerances. If this can be chambered, all is good, if not, the rifle could be tested further and it then looked at more closely.
Looking at the issue from another way, the chamber is in effect dictated by the round, therefore would be pretty easy to specify in dimensions.
I see the only way of gaining the best possible outcome, is to have the smallest chamber that will accept one of the above rounds. This will be the SAAMI or CIP minimum specs.
Those whom know of the rules at Bisley, will know of rule 150, where this is basically the same thing as above, but only in respect of the 7.62 x 51 or 308 Win due to the issued ammo. Chamber reamers made for this rule, are basically done to the minimum size that will allow for the testing of the sizing. One example is the B150 reamer many people use from PT&G.
The throat can be longer than the standard states, as this does not make for a dangerous condition, only the bore (in the throat area) diameter is the main problem, as per the test in Bisley for chambers. I know there are ways around this also, but people can figure this out for themselves.
The questions I still have unanswered are:
1. If the chamber is dictated by the specs, what allowance for neck expansion is safe? How is this to be measured accurately? For example, you might use standard Lapua 308 cases, like I do, but use a tight neck chamber to gain some real or imagined advantage.
2. Pressure signs in one rifle might not be shown the same on another unit of the exact same build. Whom at a range will decide if a rifle/ammo combo is unsafe? I know some of this is looked into with match rifle, but othewise?
3. What if a "hot load" is the only one that works in your rifle? Making for hard extraction etc, but may not in itself be unsafe.
This does not allow for tight necks or chambers, as they would not then be able to chamber one of these standard rounds.
If asked for a way of testing chambers, the answer can be quite simple: just measure the case that comes out of the rifle. The fastest way would be to use a SAAMI or CIP test gauge, like a complete round, only made from steel, and ground to close tolerances. If this can be chambered, all is good, if not, the rifle could be tested further and it then looked at more closely.
Looking at the issue from another way, the chamber is in effect dictated by the round, therefore would be pretty easy to specify in dimensions.
I see the only way of gaining the best possible outcome, is to have the smallest chamber that will accept one of the above rounds. This will be the SAAMI or CIP minimum specs.
Those whom know of the rules at Bisley, will know of rule 150, where this is basically the same thing as above, but only in respect of the 7.62 x 51 or 308 Win due to the issued ammo. Chamber reamers made for this rule, are basically done to the minimum size that will allow for the testing of the sizing. One example is the B150 reamer many people use from PT&G.
The throat can be longer than the standard states, as this does not make for a dangerous condition, only the bore (in the throat area) diameter is the main problem, as per the test in Bisley for chambers. I know there are ways around this also, but people can figure this out for themselves.
The questions I still have unanswered are:
1. If the chamber is dictated by the specs, what allowance for neck expansion is safe? How is this to be measured accurately? For example, you might use standard Lapua 308 cases, like I do, but use a tight neck chamber to gain some real or imagined advantage.
2. Pressure signs in one rifle might not be shown the same on another unit of the exact same build. Whom at a range will decide if a rifle/ammo combo is unsafe? I know some of this is looked into with match rifle, but othewise?
3. What if a "hot load" is the only one that works in your rifle? Making for hard extraction etc, but may not in itself be unsafe.
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Barry Davies
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All pertinent questions Rod, but I doubt you will get answers to them.
The need for " tight " chambers comes from the perceived notion that there is some advantage, well, when there is 600 to 1000 yards between you and the target, filled with all those gremlins we know so well, and you have a rifle that somewhat begs a proper load and tuning, all the tight chambers in the world aint going to help.
We use " standard " chambers in all of our rifles and results speak for themselves.
Proper load development and tuning will ensure you get the best out of your rifle- if a tight chamber turns you on then go for it --- cases will probably last a few more loads due to less working .
Barry
The need for " tight " chambers comes from the perceived notion that there is some advantage, well, when there is 600 to 1000 yards between you and the target, filled with all those gremlins we know so well, and you have a rifle that somewhat begs a proper load and tuning, all the tight chambers in the world aint going to help.
We use " standard " chambers in all of our rifles and results speak for themselves.
Proper load development and tuning will ensure you get the best out of your rifle- if a tight chamber turns you on then go for it --- cases will probably last a few more loads due to less working .
Barry
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Dave P
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Unless I am mistaken the benefit of using "tight" chambers is to facilitate two main items and a bonus item.
1. The neck turning of brass is for concentricity .. all part of making sure everything is in line
2. It also allows for greater control over neck tension .. all to do with consistancy
Bonus item. Less cold working of the brass extends the life
You dont need a massively undersized chamber for this to work. In fact many BR shooters dont take much more than a skim off a case neck. The reason case necks became so overly small ie .262 for a 6PPC was more due to the inconsistancy of the available brass. This meant you had to take a lot off to gain concentricity. These days .269 & .270 are more the norm.
You can run any size chamber the sameway if you use you brains and do the math.
1. The neck turning of brass is for concentricity .. all part of making sure everything is in line
2. It also allows for greater control over neck tension .. all to do with consistancy
Bonus item. Less cold working of the brass extends the life
You dont need a massively undersized chamber for this to work. In fact many BR shooters dont take much more than a skim off a case neck. The reason case necks became so overly small ie .262 for a 6PPC was more due to the inconsistancy of the available brass. This meant you had to take a lot off to gain concentricity. These days .269 & .270 are more the norm.
You can run any size chamber the sameway if you use you brains and do the math.
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Woody_rod
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Dave P wrote:Unless I am mistaken the benefit of using "tight" chambers is to facilitate two main items and a bonus item.
1. The neck turning of brass is for concentricity .. all part of making sure everything is in line
2. It also allows for greater control over neck tension .. all to do with consistancy
Bonus item. Less cold working of the brass extends the life
You dont need a massively undersized chamber for this to work. In fact many BR shooters dont take much more than a skim off a case neck. The reason case necks became so overly small ie .262 for a 6PPC was more due to the inconsistancy of the available brass. This meant you had to take a lot off to gain concentricity. These days .269 & .270 are more the norm.
You can run any size chamber the sameway if you use you brains and do the math.
Tight chamber means the whole chamber, not just the neck. You can't use a tight neck within the SSR's as they are now.
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Dave P
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Woody_rod wrote:Dave P wrote:Unless I am mistaken the benefit of using "tight" chambers is to facilitate two main items and a bonus item.
1. The neck turning of brass is for concentricity .. all part of making sure everything is in line
2. It also allows for greater control over neck tension .. all to do with consistancy
Bonus item. Less cold working of the brass extends the life
You dont need a massively undersized chamber for this to work. In fact many BR shooters dont take much more than a skim off a case neck. The reason case necks became so overly small ie .262 for a 6PPC was more due to the inconsistancy of the available brass. This meant you had to take a lot off to gain concentricity. These days .269 & .270 are more the norm.
You can run any size chamber the sameway if you use you brains and do the math.
Tight chamber means the whole chamber, not just the neck. You can't use a tight neck within the SSR's as they are now.
Yep .. but whats the advantage to undersized case bodies????? Accuaracy is consistancy and all the major variables are at the neck.
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