F/TR legal chamber size for 308??
- Thread starter 1KBR
- Start date
Erik Cortina
Team Lapua Brux Borden Captain
Sounds like someone running out of excuses for losing! 
1kBR,
To answer your question "fired case measured .470" at the rear end and .455" at the shoulder. Is this over spec?"
No, SAAMI specs for .308 chamber are 0.4564" at shoulder and 0.4714" at a point 0.200" forward of bolt face. See http://www.saami.org/specifications_and_information/publications/download/206.pdf
The losers need another excuse.
To answer your question "fired case measured .470" at the rear end and .455" at the shoulder. Is this over spec?"
No, SAAMI specs for .308 chamber are 0.4564" at shoulder and 0.4714" at a point 0.200" forward of bolt face. See http://www.saami.org/specifications_and_information/publications/download/206.pdf
The losers need another excuse.
rcw3
Site $$ Sponsor
Lbart said:
I think you are reading the print incorrectly (not that it changes things for this discussion). The min shoulder for a chamber is .4551" (not that you could measure it because there is a small radius in the chamber at the shoulder) and min at .200" forward of the bolt face is .4714", but bear in mind the stated tolerances for chamber body diameter dimensions is +.002" so technically you can add that to those dimensions.
Robert Whitley
rcw3
Site $$ Sponsor
Lbart
No biggie - no question prints can definitely be hard to decipher and read sometimes - I certainly won't say I never made an error reading a print. Actually it was helpful to look at the print again because it makes clear one can have a pretty sloppy chamber and still be within SAAMI (i.e. 4571" at the shoulder and .4734" .200" forward of the bolt face.
I guess with the original posting maybe one could try to say the chamber was under minimum and that was the issue (although with brass shrink back I don't know that you can take the brass measurement as conclusive of the chamber anyway, although it can be pretty close).
In any case, the complaint/challenge by another shooters seems off the mark.
Robert
No biggie - no question prints can definitely be hard to decipher and read sometimes - I certainly won't say I never made an error reading a print. Actually it was helpful to look at the print again because it makes clear one can have a pretty sloppy chamber and still be within SAAMI (i.e. 4571" at the shoulder and .4734" .200" forward of the bolt face.
I guess with the original posting maybe one could try to say the chamber was under minimum and that was the issue (although with brass shrink back I don't know that you can take the brass measurement as conclusive of the chamber anyway, although it can be pretty close).
In any case, the complaint/challenge by another shooters seems off the mark.
Robert
"Do they normally measure fired cases at f-class comp.?"
I know am going to catch some flak for this, but I am going to post anyway.
Answer - No.
In the thirteen years I have been shooting FC and that includes a LOT of matches around the USA and 5 countries, I have never seen it done or even suggested. I have seen comments on the net talking about people they thought were using large chambers, but that is always after those persons had won. This is a problem that does not exist. If someone believes it is being done then they SHOULD file a protest under NRA rule 16.2 and find out.
16.2 Protests—
A competitor may formally protest:
(c) The equipment which another competitor has been permitted to use.
If you are not willing to do so bite your tongue and be quiet. Don't go behind the competitors back and bad mouth them. That is character assassination. 1KBR I am not talking about you, you are just the messenger.
Please note I shoot F-open and have no horse in this race.
Larry Bartholome
I know am going to catch some flak for this, but I am going to post anyway.
Answer - No.
In the thirteen years I have been shooting FC and that includes a LOT of matches around the USA and 5 countries, I have never seen it done or even suggested. I have seen comments on the net talking about people they thought were using large chambers, but that is always after those persons had won. This is a problem that does not exist. If someone believes it is being done then they SHOULD file a protest under NRA rule 16.2 and find out.
16.2 Protests—
A competitor may formally protest:
(c) The equipment which another competitor has been permitted to use.
If you are not willing to do so bite your tongue and be quiet. Don't go behind the competitors back and bad mouth them. That is character assassination. 1KBR I am not talking about you, you are just the messenger.
Please note I shoot F-open and have no horse in this race.
Larry Bartholome
Thanks for the info, sounds like he is well in spec. As you said Eric, some people are running out of excuses and this guy won because he didnt get the wide 7-8s in the switches. I measured my factory chamber and I am slightly bigger than him, but then I didnt win, so no protests there. BTW, this was for a club championship only???
No one there seemed to know what the specs were as they have never heard of cases being measured before either. I was dragged into this fued as I was the one who had a micrometer with me.
No one there seemed to know what the specs were as they have never heard of cases being measured before either. I was dragged into this fued as I was the one who had a micrometer with me.
Tony, this guy didnt hide the fact that he was getting 3050 fps with 155 Hybrids. I think telling other people this what got him into trouble. Ive since found out he has had other barrels chambered with the same reamer, cases interchange with this barrel, but these barrels dont give anywhere near the same speed, fast barrel perhaps?
3050 is very very doable with a 155.
Absolutely - if people filed complaints over that MV over here in the UK, we'd have cartloads! We have had competitors break the 3,100 fps barrier with 155.5s and the new Sierra MK, but those loads are often a bit too warm in my view. Of course, we worry a lot less about high ambient temperatures over here and shoot alternately in pairs instead of string shooting which keeps chamber temperatures down a bit and allows the use of some very stiff loads with Viht N500-series double-base powders.
Not exactly worried about high ambient temps here at the moment. Not many people here use the N500 series powders, not sure why, I dont think it is as available as in U.K. I would have thought N540 would be good with the 155s.
Is the problem with N500 powders, the high temps in summer, or just the difference in temps between winter and summer? I,m hoping Alliant AR-comp will be good in this matter.
Is the problem with N500 powders, the high temps in summer, or just the difference in temps between winter and summer? I,m hoping Alliant AR-comp will be good in this matter.
Steve Blair
Silver $$ Contributor
8208 XBR has been noted by many shooters as a nearly ideal powder for 155-class bullets in .308. My 26" tactical rifle is getting 2990 with Berger 155.5 FULLBORE bullets. The 155 Hybrid has greater velocity potential due to the shorter bearing surface.
Keith Glasscock
Gold $$ Contributor
I was just looking at the SAAMI specs for 308 win... Even if one was trying to do a full-on end-run of the rules, it is still a 308 Win and would produce about the same velocity. There is something to be had in managing the chamber specs, in my opinion, but it isn't velocity!
I agree with many others that have posted. There is no possible reason to even worry about another competitor's rifle with three exceptions:
1) The ammo going in isn't 223 or 308 (ie. the guy that is trying to fake it wth a 7-08 or 260) or comes out with an Ackley shoulder - that would be cheating in my book.
2) The rifle is seriously over-weight. I'm not talking ounces here folks...
3) The guy on either side of me is blowing primers right and left - unsafe!
FWIW, 3050 is achievable easily with a long enough barrel. My 26" is running in the node at 2924 and I can increase the charge a full 1.2 grains safely (70fps). Unfortunately, it doesn't shoot there...
There are some that believe that you can buy your way into the winner's circle. The people that end up in the winner's circle can tell you that isn't true....
I agree with many others that have posted. There is no possible reason to even worry about another competitor's rifle with three exceptions:
1) The ammo going in isn't 223 or 308 (ie. the guy that is trying to fake it wth a 7-08 or 260) or comes out with an Ackley shoulder - that would be cheating in my book.
2) The rifle is seriously over-weight. I'm not talking ounces here folks...
3) The guy on either side of me is blowing primers right and left - unsafe!
FWIW, 3050 is achievable easily with a long enough barrel. My 26" is running in the node at 2924 and I can increase the charge a full 1.2 grains safely (70fps). Unfortunately, it doesn't shoot there...
There are some that believe that you can buy your way into the winner's circle. The people that end up in the winner's circle can tell you that isn't true....
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