Oly Posted January 28, 2012 Report Share Posted January 28, 2012 After a period of absence and inaccuracy I am getting back into reloading after a couple of years off, so please bare with me as I may be a little rusty... Tonight I have measured my chamber lengths to help determine my bullet seating depths and jump to the lands for my reloaded rounds. Whilst I can't recall all my previous measurements, I know that in my previous .243Win Remington 700 I seated my bullets 0.010 off the lands. However, having just measured my .308Win Tikka M595 Continental it appears that I cannot seat my bullets this close. The manuals maximum overall length (to the bullet tip) is 2.800, but my chamber measures 2.870 (effectively to the ogive). Therefore, even reloading to the manual's maximum overall length of 2.800, the distance to the lands will still be 0.070 plus the distance from the bullet tip to the ogive... I have thought it through, remeasured and remeasured again, but can only come to this conclusion. Can this be correct? Are some chambers really this long? Thanks, Oly Link to comment Share on other sites More sharing options...
achosenman Posted January 29, 2012 Report Share Posted January 29, 2012 After a period of absence and inaccuracy I am getting back into reloading after a couple of years off, so please bare with me as I may be a little rusty... Tonight I have measured my chamber lengths to help determine my bullet seating depths and jump to the lands for my reloaded rounds. Whilst I can't recall all my previous measurements, I know that in my previous .243Win Remington 700 I seated my bullets 0.010 off the lands. However, having just measured my .308Win Tikka M595 Continental it appears that I cannot seat my bullets this close. The manuals maximum overall length (to the bullet tip) is 2.800, but my chamber measures 2.870 (effectively to the ogive). Therefore, even reloading to the manual's maximum overall length of 2.800, the distance to the lands will still be 0.070 plus the distance from the bullet tip to the ogive... I have thought it through, remeasured and remeasured again, but can only come to this conclusion. Can this be correct? Are some chambers really this long? Thanks, Oly Oly, the short answer is yes. Seating close to the lands is generally better, but you may not get close. My 270 is a typical example. It is excellent at .010 and .075 and .130. Magazine length dictates .075 for me. Enjoy. ATB Link to comment Share on other sites More sharing options...
duey Posted January 29, 2012 Report Share Posted January 29, 2012 Oly the 2.800 is the sammi spec for a factory loaded round, you can move the bullit forward to meet your requirement of .010 off the lands with a couple of things to watch If Mag fed will the longer round still fit in the mag, and probably more important is there su fficient of the bearing surface of the bullit still in the neck of the case, if the answer to both is yes then work on your load to those measurements and see hpow you get on you may also find an accuracy node related to jump to lands at 0.05 or 0.07 ish it all depends on the individual rifle bullet combination and just to throw another spanner in the works there are some reloaders that swear by building reloads to sammi spec only and get good accuracy I personally stick to 0.010 off the lands with 30 cal ammo good luck Ian Link to comment Share on other sites More sharing options...
duey Posted January 29, 2012 Report Share Posted January 29, 2012 I can load my 52gr amax in my remmy 22-250 0.005 off the lands and have no probs with fitting mag or falling out of case which amazes me with a remmy chamber, especially as I had to have my 308 barrel removed, chamber cut off and rechambered to palmer spec to get it to work as the chamber was that sloppy with a hugh freebore, go figure Ian Link to comment Share on other sites More sharing options...
Oly Posted January 29, 2012 Author Report Share Posted January 29, 2012 Many thanks for the responses - good reassurance!! I'm pretty sure that both rifles would not hold a bullet 0.010 off the lands, as they would have already fallen out of the case!! I'm sure I'll find another sweet spot with a little trial and error though! Cheers, Oly Link to comment Share on other sites More sharing options...
eldon Posted January 29, 2012 Report Share Posted January 29, 2012 Whilst I can't recall all my previous measurements, I know that in my previous .243Win Remington 700 I seated my bullets 0.010 off the lands. I am surprised you managed this previously. Remington seem particularly long on the free bore. If your Tikka is anything like that then realsitically you will have to single load or be miles off the lands, your choice? Link to comment Share on other sites More sharing options...
Oly Posted January 29, 2012 Author Report Share Posted January 29, 2012 The measurements 223Rem - Chamber length: 2.280 AOL (to bullet tip): 2.250 AOL (to ogive): 1.811 Jump to Lands: 0.469 308Win - Chamber length: 2.869(5) AOL (to bullet tip): 2.747 AOL (to ogive): 2.149 Jump to Lands: 0.720 Do they seem reasonable figures for factory Tikka M595 Continentals? Link to comment Share on other sites More sharing options...
Gunsgobang88 Posted January 29, 2012 Report Share Posted January 29, 2012 Hi Oly, Referring to your first post, some chamber throats are really that long. As others have noted, in many rifles to seat the bullet just off the lands the bullet would be falling out of the case and the round would not fit the magazine. In extremis it's called 'freebore' and used to reduce pressure but usually does nothing for accuracy. Early smokeless rounds were inconsistent and rifle manufacturers were generous in their chamber dimensions to avoid problems. Mausers had freebore of up to 3.5 times bullet diameter. Post war Weatherby took the same approach. More conservative European makers such as Heym took the same attitude until fairly recently. US makers tend to throat their rifles to accommodate the longest commercial round available in a particular chambering, Alan Link to comment Share on other sites More sharing options...
Oly Posted January 30, 2012 Author Report Share Posted January 30, 2012 Interesting stuff there Alan, so it sounds like my chamber sizes are not out of the ordinary?! Link to comment Share on other sites More sharing options...
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