308 trim to 2.000?
- Thread starter mr45man
- Start date
Too short.
2.005"- 2.008".
2.005"- 2.008".
Penalty for trimming to 2.00? For one thing you're providing more empty space for a ring of carbon to buildup at the mouth of the chamber, and it will, as seen with my borescope. Get one of the Sinclair Chamber over-all-length gauges, cost about $7 & reusable, and take an accurate length of your chamber.
They are all different and can vary by .040" or more. Then, let them stretch to whatever length you are comfortable with.
My match chamber brass is left to "grow" to within .005", factory chambers to .010". I never get the carbon ring buildup.
Second point: If you're already working with a long throat & trying to seat short bullets to touch, and still keep them inside the case neck so they don't fall out, you'll have more bullet/neck contact to hold the bullet(s).
I cannot think of a single advantage to over trimming cases.
They are all different and can vary by .040" or more. Then, let them stretch to whatever length you are comfortable with.
My match chamber brass is left to "grow" to within .005", factory chambers to .010". I never get the carbon ring buildup.
Second point: If you're already working with a long throat & trying to seat short bullets to touch, and still keep them inside the case neck so they don't fall out, you'll have more bullet/neck contact to hold the bullet(s).
I cannot think of a single advantage to over trimming cases.
Frank is right on all points. My seven .308 rifles, both factory and custom, have chamber lengths ranging from 2.035" to 2.040". Consequently, I rarely trim brass.
Not a problem at all, and I've been trimming my 308s to 2" even for decades. Saves trimming them every time, which was always a concern when dealing with the volumes I had to shoot every day. Never had a bit of trouble with the cleaning, but then the guns were usually kept pretty clean to begin with.
Sorry to buck the conventional wisdom here guys, but we're discussing how many angels can dance on the head of a pin.
Sorry to buck the conventional wisdom here guys, but we're discussing how many angels can dance on the head of a pin.
[br]KevinThomas said:
So, Kevin, what does that gain you? What is the concern of which you write? And, what does cartridge quantity have to do with case length? [br]
I have several lots of Lapua .308 brass that have never been trimmed. Some are neck turned, some not. After six firings on one lot, they are still only around 2.020", .015" short of chamber length. My Lapua 6.5-.284 brass is expanded to 7mm, neck turned, fire-formed to Shehane and fired in competition with pretty healthy loads. Never trimmed. It would be pretty tough to convince me that this has affected my accuracy. In fact, after six firings, the brass has only grown about .006", well short of the chamber length. Trimming is over rated and frequently over done. If the case has grown to within .010" of the chamber length, trim. If not, why bother?
I have a question.... no matter what length you choose to trim, would it not be prudent to keep all your brass at the exact same length? I mean neck tension is so critical, I don't want some of my brass at 2.005, some at 2.010 and some at 2.015. I've seen brass "grow" at different rates. Why not keep them all at the same length to keep neck tension as equal as possible on all rounds? Just wondering.....
Thanks for all the input.
As i see it the only reason to trim that short is to get the brass all the same length because you have some that measure short to begin with.
That is letting the tail wag the dog
The 308 necks are short to begin with, no reason to make them even shorter.
John H.
As i see it the only reason to trim that short is to get the brass all the same length because you have some that measure short to begin with.
That is letting the tail wag the dog
The 308 necks are short to begin with, no reason to make them even shorter.
John H.
[br]Longshooter70 said:
Let's consider the example of .308 cases with .250" bullet shank engagement. One case has a .010" longer neck than another. If we accept that tension is uniform along the engagement length and contributes equally, that is a 4% neck tension variance. If you are that concerned about neck tension variation, you had better be turning your necks to a very tight tolerance.
I do.... I turn them to .014" and use a .335 bushing for right at .001 neck tension and I soft seat my bullets... I'm pretty anal about keeping everything the same... Seems to be working....
John
John
[br]Longshooter70 said:
What is your neck thickness variation after turning? A .014 neck thickness will not reliably clean up any Lapua brass that I use, .222, 6BR (either blue or gold), .284, or .308 Win. I turn mine, depending upon cartridge, to .011" to .0123". They are turned in two passes and held to ±.0001" and 100% measured. [br]
Some folks are shooting without turning or culling by case wall thickness and still do well. It may not be crucial.
Steve,
you're actually making my point here. You don't trim, and you clearly (and correctly) state that you can't see where it as affected accuracy one whit. I'll agree, and doubt that you could prove any sort of accuracy gain, or loss, based on .005"-.010" in case length alone. As to why I've done it this way, that's sort of a different situation. Remember, at any given moment I was loading for 20-30 different 308s, and didn't have time to try to keep brass separate by gun. Or monitor their case lenghts, by gun. It all had to be processed at the same time, and some standard had to be set. In the instance of the 308s, that standard was 2.000" even. To be fair, it wasn't my call initially; I inherited it from Jim Hull, my predecessor in the lab. It certainly didn't cause any problems, and I saw no earthly reason to worry about changing it. I ran the next 20+ years doing it the same way Jim had set it up, and never had reason to doubt the choice. For those not familiar with the requirements here, this equates to my firing literally hundreds of thousands of ten-round groups over the years, with the vast (95% or more) majority holding somewhere within the 1/4 to 1/2 MOA range at 200 yards. Not a single time, ever, can I recall a group that failed to stay within those standards that could even be remotely blamed on case length. Not once, ever.
Aside from the 308s, I also had several other chamberings that required the use of cases which were often shorter than the SAAMI specs, for one reason or another. We were running a 6.5-08 as a standard test vehicle LONG before Remington ever standardized the 260, just as we were the 7mm-08. I made almost all of these cases from 243 Win brass, with the resultant case length variations. The Sinclair gages you mentioned were used to set what we considered acceptable dimensions, and I'll have to admit, I never lost any sleep over it beyond that. So long as the cases weren't too long, I was perfectly happy.
This topic seems to have come up frequently over the past few months, with a few guys I've spoken to stressing themselves over trimming all their cases to precisely the same length, right down to the thousandth. It's just not an area to be that concerned about, and you'll never notice it in your shooting results. Over on another site, there's a very heated debate (which I've specifically avoided delving into) concerning different impact points from the last round out of a Service Rifle. Really? In the thousands of strings I've fired in HP competition over the years, I've never once heard a coach calling something different on the last round out of the mag, as oppsed to the one or seven that previously went down range. Nor have I ever seen the need to hold differently to account for this "last shot impact shift" that has them so worked up right now. In the HP venue, I've shot for several military teams with both the M14 and M16 families of Service Rifles, I'm a Distinguished Rifleman, I hold the President's Hundred and several State Service Rifle Championship titles. If there was some sort of impact shift that amounted to anything more than fly feces, I think I would have run across the phenomenon. Total BS, and yet it's the topic of a heated debate. My point here is, you get any group of shooters together and you can stir up a controversy, valid or not. I think everyone can make their own decisions from there. Personally, I'm not changing a thing.
you're actually making my point here. You don't trim, and you clearly (and correctly) state that you can't see where it as affected accuracy one whit. I'll agree, and doubt that you could prove any sort of accuracy gain, or loss, based on .005"-.010" in case length alone. As to why I've done it this way, that's sort of a different situation. Remember, at any given moment I was loading for 20-30 different 308s, and didn't have time to try to keep brass separate by gun. Or monitor their case lenghts, by gun. It all had to be processed at the same time, and some standard had to be set. In the instance of the 308s, that standard was 2.000" even. To be fair, it wasn't my call initially; I inherited it from Jim Hull, my predecessor in the lab. It certainly didn't cause any problems, and I saw no earthly reason to worry about changing it. I ran the next 20+ years doing it the same way Jim had set it up, and never had reason to doubt the choice. For those not familiar with the requirements here, this equates to my firing literally hundreds of thousands of ten-round groups over the years, with the vast (95% or more) majority holding somewhere within the 1/4 to 1/2 MOA range at 200 yards. Not a single time, ever, can I recall a group that failed to stay within those standards that could even be remotely blamed on case length. Not once, ever.
Aside from the 308s, I also had several other chamberings that required the use of cases which were often shorter than the SAAMI specs, for one reason or another. We were running a 6.5-08 as a standard test vehicle LONG before Remington ever standardized the 260, just as we were the 7mm-08. I made almost all of these cases from 243 Win brass, with the resultant case length variations. The Sinclair gages you mentioned were used to set what we considered acceptable dimensions, and I'll have to admit, I never lost any sleep over it beyond that. So long as the cases weren't too long, I was perfectly happy.
This topic seems to have come up frequently over the past few months, with a few guys I've spoken to stressing themselves over trimming all their cases to precisely the same length, right down to the thousandth. It's just not an area to be that concerned about, and you'll never notice it in your shooting results. Over on another site, there's a very heated debate (which I've specifically avoided delving into) concerning different impact points from the last round out of a Service Rifle. Really? In the thousands of strings I've fired in HP competition over the years, I've never once heard a coach calling something different on the last round out of the mag, as oppsed to the one or seven that previously went down range. Nor have I ever seen the need to hold differently to account for this "last shot impact shift" that has them so worked up right now. In the HP venue, I've shot for several military teams with both the M14 and M16 families of Service Rifles, I'm a Distinguished Rifleman, I hold the President's Hundred and several State Service Rifle Championship titles. If there was some sort of impact shift that amounted to anything more than fly feces, I think I would have run across the phenomenon. Total BS, and yet it's the topic of a heated debate. My point here is, you get any group of shooters together and you can stir up a controversy, valid or not. I think everyone can make their own decisions from there. Personally, I'm not changing a thing.
Kevin, [br]
You may have noticed that I referred to Lapua brass as examples. That does not mean I do not trim brass. When I must use Remington (stopped using Winchester) brass, there is sufficient variation that I cannot reliably neck turn, sometimes up to .020" case length variation. I do not see that with Lapua or with the 500 Norma .270 WSM cases I just bought. I also didn't imply that trimming .308 cases to 2.000" would affect accuracy. I know better. It is just that I object to doing things that are not necessary and do not contribute to success. I liken some actions, like excessive trimming, to genuflecting in the presence of a black cat. If it makes one feel better, by all means, do it. Just don't try to convince me that there is a valid reason to do so.
You may have noticed that I referred to Lapua brass as examples. That does not mean I do not trim brass. When I must use Remington (stopped using Winchester) brass, there is sufficient variation that I cannot reliably neck turn, sometimes up to .020" case length variation. I do not see that with Lapua or with the 500 Norma .270 WSM cases I just bought. I also didn't imply that trimming .308 cases to 2.000" would affect accuracy. I know better. It is just that I object to doing things that are not necessary and do not contribute to success. I liken some actions, like excessive trimming, to genuflecting in the presence of a black cat. If it makes one feel better, by all means, do it. Just don't try to convince me that there is a valid reason to do so.
I used to analy trim my 6br's and .308's. I'd mic them and fool with my case trimmer adjustments to get everyone exactly the same length. Then because I was shooting a lot of practice and matches I just stopped because I didn't have the time and let them grow to whatever length they wanted to. This is with Lapua brass.
You know what? Didn't make a bit of difference. I'd shoot new brass for 20-25 loadings then just file 13 them and start with new brass again. This is of course in custom barrels cut with my reamers. Factory chambers could be a different animal altogether.
Danny
You know what? Didn't make a bit of difference. I'd shoot new brass for 20-25 loadings then just file 13 them and start with new brass again. This is of course in custom barrels cut with my reamers. Factory chambers could be a different animal altogether.
Danny
Fair enough, but as I said, I had an unusal amount of chambers that I had to accomodate, and they were constantly rotating in and out of service, along with many new ones as the older ones died. That, for me, was often only a month or so from their being brand new barrels to having been shot into retirement. Frankly, I didn't have time to get too personal with them, and was dealing with a mass production process.
No argument with your methodology or with carrying on Martin's approach. I met all the old guys in Santa Fe Springs and I know they were careful and prudent. [br]
BTW, I wouldn't have to buy and expand that Norma .270 WSM brass if Lapua would make some .300 WSM. Just sayin'...
BTW, I wouldn't have to buy and expand that Norma .270 WSM brass if Lapua would make some .300 WSM. Just sayin'...
Steve,
You're obviously not keeping your fingers crossed tightly enough. That, or you haven't shared this with enough of your compatriots out there in WSM land. We've taken plenty of requests for these (especially with all the F class actrivity) but there's some other cases that have beaten the WSM inquiries pretty soundly. We may get around to it at some point, but I can't promise you any joy in the very near future.
Sorry!
You're obviously not keeping your fingers crossed tightly enough. That, or you haven't shared this with enough of your compatriots out there in WSM land. We've taken plenty of requests for these (especially with all the F class actrivity) but there's some other cases that have beaten the WSM inquiries pretty soundly. We may get around to it at some point, but I can't promise you any joy in the very near future.
Sorry!
Donovan,
Everything has it's limits, and I'm sure it would become an issue at some point. My guess (and I stress; guess) is that it would be somewhere south of the figures you mention here. Possibly considerably south. And no, I'm not saying that "shorter is better" at all. I'm saying too long is a bad thing, if it gets to the point where there's interference with the chamber/leade blend. And, as we've already established, that figure is often quite a ways forward of what SAAMI calls as "Max." Put it this way, never letting them get beyond that "max" length figure will never cause you a problem in a standard chamber. May not for quite a ways ahead of that, but you get the idea. By the same token, trimming a few thou under what they've somewhat arbitrarily decided is the magical "trim to" length, is likewise not going to be an issue. Remember, this conversation started over a difference of .002". Take out a mic, set it to .000" and then open it back up to .002". That's how much we're talking about. I say again; Really?
Everything has it's limits, and I'm sure it would become an issue at some point. My guess (and I stress; guess) is that it would be somewhere south of the figures you mention here. Possibly considerably south. And no, I'm not saying that "shorter is better" at all. I'm saying too long is a bad thing, if it gets to the point where there's interference with the chamber/leade blend. And, as we've already established, that figure is often quite a ways forward of what SAAMI calls as "Max." Put it this way, never letting them get beyond that "max" length figure will never cause you a problem in a standard chamber. May not for quite a ways ahead of that, but you get the idea. By the same token, trimming a few thou under what they've somewhat arbitrarily decided is the magical "trim to" length, is likewise not going to be an issue. Remember, this conversation started over a difference of .002". Take out a mic, set it to .000" and then open it back up to .002". That's how much we're talking about. I say again; Really?
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