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Thread: Long Throat explanation?

  1. #1
    Member kodiakrain's Avatar
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    Default Long Throat explanation?

    I have been wondering about the length of throat in my Sako 85 .270wsm

    Why is it so far from the max mag length (2.93 COL) to the Lands (2.99 or 3.00 COAL) for several bullets I am loading for. I have measured several bullets using several methods, It's way out there and I can only get there (-.05 back) on a few of the larger bullets.

    Did Sako do this on purpose, as I can't imagine them slacking on the Barrel build.

    So ran into this on Gunners Den,


    Bullet Seating Depth
    Bullet seating depth has a great impact on rifle accuracy. The bullet seating depth for each individual rifle and bullet varies and should be set accorgingly. NOTE: Do not use this procedure for rifles chambered for weatherby cartridges as these have long throats cut into the rifles bore.

    Is this something they may have done for a reason with the WSM for example? I have no problems with accuracy setting way back from the lands, usually finding 2.80-2.90 the place I want to be. Seating them out to 2.93 a squeeze into my Magazine or loading a few out to the lands and back up a bit has not showed any increase in accuracy at all?

    Comments?

    Ten Hours in that little raft off the AK peninsula, blowin' NW 60, in November.... "the Power of Life and Death is in the Tongue," and Yes, God is Good !

  2. #2

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    I also have a Sako 85 (in 300 WSM) and it has a long throat. I don't know if it's just some cartridges or all and I'm not sure why they do it. The Weatherby's are known for a lot of freebore and both my Sendero's (in 25-06 and 300 RUM) have long throats. More freebore will reduce the likelihood of overpressures. Some argue that freebore is detrimental to accuracy and some say it doesn't matter. On seating depth, I personally think that it's up to the personality of the rifle barrel as to where it likes which bullet seated with whatever powder. An interesting thread on this just came up in another forum.

    http://www.longrangehunting.com/foru...-tested-56067/

    My opinion... the best seating depth depends on rifle, bullet, powder etc...

  3. #3

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    You might do some digging at the Weatherby site or in their old catalogs for their own explanation and justification for freebore. It was supposed to do two things as I recall- hold down pressures while allowing for extra velocity, giving the bullet a "jump" before encountering the rifling. In my personal experience it compromised accuracy to a degree, and some claim it resulted in a lot more throat erosion as gases could briefly get past the bullets.

    I use the term "long throat" to mean something different than freebore, though. In my uses, it means I can seat the bullets out further than factory standard, allowing more powder capacity than standard. The magazine has to be long enough to allow it, but I still seat the bullets very close to the rifling for best accuracy and there is no "jump" a la freebore.

    One of the fair-haired ladies of long throating in its day was the 257 Roberts. When Remington made it a factory round, they had short action on the brain and seated it to an OAL of 2.75", shorter than most folks did in the past when loading it as a wildcat on the 7x57 case. The typical long throated Roberts allowed a 3" OAL, and there was quite a bit written about it. When RCBS built my rifle I sent them several dummy cases loaded with the Sierra 117 grain bullet to a 3" OAL, which put the base of the bullet right at the base of the neck rather than further down in the body. They used them as a measure when cutting the throat in my barrel. I had the rifle built on a 700 Remington action I salvaged from a lefty 30-06. It required a very small bit of feed rail adjustment while they were at it.

    The Roberts was handicapped in the first place by loading to lower pressures (45,000 PSI like the factory 7x57 as I recall) in honor of some older rifles chambered by the wildcat. Between that and the restricted powder capacity from deep seating to 2.75", it really didn't turn out velocities to its potential. Long throating and upping the pressures to those comparable for other factory loadings results in substantial jumps in velocity. In mine I get very long case life while pretty much duplicating the velocities of the 257 AI. I have never got around to comparing case capacities, but I'm guessing the long throat brings it up very close to the AI. And barrel life has been spectacular. I've shot that rifle for 35 years, the first ten including a whole lot of ground squirrel and rockchuck shooting, and accuracy is still really good. No, it won't break half an inch like it used to, but most loads still break an inch.

    Another notable example is the Ruger #1 in 243. The one I had allowed seating the Speer 105 spitzer all the way out till the base of the bullet was at the base of the neck. Funny looking thing, but it vastly increased powder capacity and velocity. I had to carefully label all boxes loaded that way so they wouldn't try to sneak into a standard rifle. Probably not much fear, because it made the round something like 3/8" longer than would fit in standard magazines. Here's the kicker- that #1 wouldn't shoot for beans with standard seating depths, but with the bullet seated out to that length and just shy of the rifling, it was a sincere one-holer.

    In your case, I'm betting that long throat explains why you're not getting "book" velocities from your rifle. If it was my rifle, I'd figure out what your max OAL is with that long throat, then pray that the magazine would allow you to seat that long as a standard. I'm betting your "max" load is going to be higher than book as a result, but I'm also betting your groups really shrink.

  4. #4

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    BrownBear, I have considered freebore and long throats to be the same thing. Maybe I misunderstand it. Can you explain the difference as you understand it?

  5. #5

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    Quote Originally Posted by MontanaRifleman View Post
    BrownBear, I have considered freebore and long throats to be the same thing. Maybe I misunderstand it. Can you explain the difference as you understand it?
    I think I explained it above, but I'll try it this way. Remember, it's my own distinction between the two.

    For me "free bore" means the rifle is set up to allow the bullet to jump quite a ways before it encounters the rifling.

    For my purposes ranging from rifle design to reloading strategies, "long throat" means I can seat the bullet out to a longer LOA than standard. There's no extra "jump" for the bullet because I'm using the extra throat to seat it out to virtually kiss the rifling, rather than leaving the round standard length so I get some jump.

    Now, a poorly conceived "long throat" turns into a "free bore" in a hurry if your magazine won't let you seat your bullets out far enough to kiss the rifling. Either that, or you've just turned a magazine gun into a one-shooter. ;-)

  6. #6

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    I been thinking about your question, and thought of another example that might help you see my distinction between the two.

    In that Ruger #1 243, it's a "long throat" to me when seating the 105 Speer all the way out to almost kiss the rifling. But when I tried seating some 87 grain spitzers that far out, there was about 1/64" of bullet in the neck. You could shove it sideways with moderate finger pressure. I had to seat the bullet deeper, and as a result it was a long ways from the rifling. Viola! It was free-bored. But it "grouped" like a cheap shotgun with economy ammo. 100 grain bullets were somewhere in between. Seated out to the rifling, there was only a little over 1/8" of bullet in the neck. Grouped like crazy, but so little bullet was in the neck that I never carried them in the field.

    BTW- With the 105 seated all the way out, the max loads were waaaaay over "book" max due to the gained powder capacity. But so were velocities with slow powders. Add in the 26" barrel of the #1 and velocities were pushing up toward the 240 Weatherby mark. But if by some catastrophic mistake someone had managed to push one of those rounds into a standard chamber, I'm betting they would have had a bomb on their hands. Hence my careful labeling of the loads.

  7. #7

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    Thanks for the explanation and it makes sense. The way I see it, a long throat can be freebore or not depending on the seating of the bullet to or away from the lans.

  8. #8

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    Exactly. I'm not a fan of "free bore" a la Weatherby, where the bullet has to jump quite a ways to reach the rifling. But when it works with the magazine length and bullet length, I AM a fan of long throats that let me seat the bullet out far enough to reach the base of the neck.

    I don't know if the rest of the world sees my distinction, but I'm sticking to it! ;-)

  9. #9
    Member kodiakrain's Avatar
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    Default Good description

    I get the distinction,

    Interestingly enough, over just a bit of experience I am finding that my Sako actually likes the Jump more than the Kiss,

    Couple times I have kind of stumbled onto noticing that pressing the bullet back in a bit more, like from 2.85 to 2.80 for a Barnes 110gr TTSX I have both increased velocity by as much as 200fps and picked up noticeably better accuracy? These short bullets are a long way from the lands anyway but "longer is always better" may not be the story for me. Maybe it is less open space in the case, not "compressed load" by definition, but basically more efficient use of case area powder vs. air space? I may be noticing this with the Nosler 160gr partition also, long enough to "Lands it" but pulling back into Mag max actually is better vel and accuracy?

    I guess I could pour more powder in there, (NEVER OVER MAX!!!!!)

    haven't seen this enough to lock in on the idea but it is interesting, hence the question, maybe Sako does this on purpose for WSM case capacity reasons, etc.?
    Ten Hours in that little raft off the AK peninsula, blowin' NW 60, in November.... "the Power of Life and Death is in the Tongue," and Yes, God is Good !

  10. #10

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    I don't know Sako well enough to offer speculation. And I know even less about WSMs- just no experience with them at all.

    But it sounds like you're right on track, along the lines of "If it aint broke, don't fix it!"

    You're doing well, and putting the right kind of thought and caution in the right places.

  11. #11
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    Default

    What is wrong with these manufactures that make and sell these rifles all around the world, don't they know that America is the only place that makes and sells bullets? You would think that jests maybe you would throat a rife barrel for the bullets they make in the U.S.A. Could it be they might throat for other countries beside just what's available from the U.S.A.? What part of America does Finland in? I guess it's a good thing nobody makes bullets but us.
    "The tree of liberty must be refreshed from time to time with the blood of patriots and tryants." (Thomas Jefferson

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    Default Lapua is in Ohio, maybe?

    Was just looking at Lapua for .22 info and guess what, they aren't in Ohio!! More Finlanders.....

    Who'd have figur'd that out? Kinda good stuff there.

    No .270wsm tho, but, I make my own now so,....

    Yea, RCBS, and Nosler..... that's Bend, Oregon there
    Ten Hours in that little raft off the AK peninsula, blowin' NW 60, in November.... "the Power of Life and Death is in the Tongue," and Yes, God is Good !

  13. #13
    Member Big Al's Avatar
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    You do know that cutting a throat for one bullet takes a little head scratching, you can imagine what kind of head scratching it takes to cut a throat so everything works? One of the big reasons why custom barrels shoot so much better than the factory barrels do, don't get me wrong but this is just one of any reasons why factory barrels are left in the dirt compared to custom barrels. that is beside looking like a sewer pipe inside.
    "The tree of liberty must be refreshed from time to time with the blood of patriots and tryants." (Thomas Jefferson

  14. #14
    Member kodiakrain's Avatar
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    Default So what's the story

    and that, Big Al, brings up the next question,
    from a guy who is brand new to custom ammunition..... and likin' it...

    What's the story on custom barrels, maybe not so bad to wear this one out??

    Seriously, what is an approx cost for a real nice custom barrel, I imagine they can just pull this one and screw a barrel onto this rifle that is customized for throat length, etc? I imagine cost is hard to pin down but, several hundred, or is it out of control expensive to "Do It Right" and have a barrel that is fantastic to load for and actually improves the value of a rifle I already think is Real Good in just about every other way?
    Ten Hours in that little raft off the AK peninsula, blowin' NW 60, in November.... "the Power of Life and Death is in the Tongue," and Yes, God is Good !

  15. #15
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    Default A Gold Mine of information.

    Quote Originally Posted by BrownBear View Post
    You might do some digging at the Weatherby site or in their old catalogs for their own explanation and justification for freebore. It was supposed to do two things as I recall- hold down pressures while allowing for extra velocity, giving the bullet a "jump" before encountering the rifling. In my personal experience it compromised accuracy to a degree, and some claim it resulted in a lot more throat erosion as gases could briefly get past the bullets.

    I use the term "long throat" to mean something different than freebore, though. In my uses, it means I can seat the bullets out further than factory standard, allowing more powder capacity than standard. The magazine has to be long enough to allow it, but I still seat the bullets very close to the rifling for best accuracy and there is no "jump" a la freebore.

    One of the fair-haired ladies of long throating in its day was the 257 Roberts. When Remington made it a factory round, they had short action on the brain and seated it to an OAL of 2.75", shorter than most folks did in the past when loading it as a wildcat on the 7x57 case. The typical long throated Roberts allowed a 3" OAL, and there was quite a bit written about it. When RCBS built my rifle I sent them several dummy cases loaded with the Sierra 117 grain bullet to a 3" OAL, which put the base of the bullet right at the base of the neck rather than further down in the body. They used them as a measure when cutting the throat in my barrel. I had the rifle built on a 700 Remington action I salvaged from a lefty 30-06. It required a very small bit of feed rail adjustment while they were at it.

    The Roberts was handicapped in the first place by loading to lower pressures (45,000 PSI like the factory 7x57 as I recall) in honor of some older rifles chambered by the wildcat. Between that and the restricted powder capacity from deep seating to 2.75", it really didn't turn out velocities to its potential. Long throating and upping the pressures to those comparable for other factory loadings results in substantial jumps in velocity. In mine I get very long case life while pretty much duplicating the velocities of the 257 AI. I have never got around to comparing case capacities, but I'm guessing the long throat brings it up very close to the AI. And barrel life has been spectacular. I've shot that rifle for 35 years, the first ten including a whole lot of ground squirrel and rockchuck shooting, and accuracy is still really good. No, it won't break half an inch like it used to, but most loads still break an inch.

    Another notable example is the Ruger #1 in 243. The one I had allowed seating the Speer 105 spitzer all the way out till the base of the bullet was at the base of the neck. Funny looking thing, but it vastly increased powder capacity and velocity. I had to carefully label all boxes loaded that way so they wouldn't try to sneak into a standard rifle. Probably not much fear, because it made the round something like 3/8" longer than would fit in standard magazines. Here's the kicker- that #1 wouldn't shoot for beans with standard seating depths, but with the bullet seated out to that length and just shy of the rifling, it was a sincere one-holer.

    In your case, I'm betting that long throat explains why you're not getting "book" velocities from your rifle. If it was my rifle, I'd figure out what your max OAL is with that long throat, then pray that the magazine would allow you to seat that long as a standard. I'm betting your "max" load is going to be higher than book as a result, but I'm also betting your groups really shrink.
    Brownbear:
    That kind of information is SOOO, good. You just don't hear much about that stuff these days, but it was common years back.

    If you have enough action length, (like on a L A Rem. 700) one can have the throat lengthened to allow whichever bullet to seat wherever you want it. I did that with my 7mm R M. Stan Jackson did it for me. Now, I can seat bullets pretty much as long as I want. And, like you said, the loads MUST be labeled for that rifle ONLY. To chamber them in a shorter throat ed rifle, would cause the bullet to be pushed back into the case, and that could have destructive results.

    I know that "kissing the lands", is something many people consider essential to accuracy, but if they always do it that way, they wouldn't know if it worked the other way.

    Factory loads have a LOT of jump in my rifle, but they're as accurate as before, IME.

    I'm convinced that free-bore, like Weatherby does it, works like he said. The 7mm Wby gives better performance than the 7mm RM, even though the case capacities are essentially the same. I believe that Free-bore is one of the reasons. Also, if the bore, in free-bore is not oversized, I don't think accuracy should suffer.

    Weatherby rifles and cartridges are accurate, and I can't see them being more accurate, or delivering greater performance without the free-bore.

    But, that is mostly conjecture, compared to your actual experiences. Again, I appreciate hearing about these things, and the reasoning behind them.

    Smitty of the North
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    Has it ever occurred to you, that Nothing ever occurs to God? Adrien Rodgers.
    You can't out-give God.

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    Quote Originally Posted by kodiakrain View Post
    and that, Big Al, brings up the next question,
    from a guy who is brand new to custom ammunition..... and likin' it...

    What's the story on custom barrels, maybe not so bad to wear this one out??

    Seriously, what is an approx cost for a real nice custom barrel, I imagine they can just pull this one and screw a barrel onto this rifle that is customized for throat length, etc? I imagine cost is hard to pin down but, several hundred, or is it out of control expensive to "Do It Right" and have a barrel that is fantastic to load for and actually improves the value of a rifle I already think is Real Good in just about every other way?
    I had my Rem 700, 280 rebarreled and blue printed by Stan Jackson in Anchorage. That made it very accurate with nearly everything I've shot in it.

    I hung the original barrel on the wall in my garage. Ever since, I've felt like I was one of the Beeg Boys.

    He used a Douglas barrel, but you could choose another brand. I have Shilen barrel on another rifle, that is a gooder'n too.

    I don't remember the price, but I thought it was quite reasonable.

    You could easily give him a call for future reference. He can make the throat as long, or as short as you like. Just give him a cartridge with the bullet you like, seated to the length you'd like it to be.

    Smitty of the North
    Walk Slow, and Drink a Lotta Water.
    Has it ever occurred to you, that Nothing ever occurs to God? Adrien Rodgers.
    You can't out-give God.

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