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Second opinion on seating depth
- Thread starter SHAGGY101
- Start date
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He mentioned the benchrest guys. Those that are full length resizing aren't using a standard die set. They have custom dies cut to match their chamber only a couple of thousands smaller.
I doubt if many on this forum have custom dies made to fit their chamber. I know I don't.
Yes, well the suggestion, and my clarification, had to do with the accuracy benefits of full length sizing versus neck sizing. The quality of the full length die being used and its dimensional quality compared to the rifle's chamber is another topic.
I have custom dies. Quite a few other members do also, in the pursuit of improved accuracy and/or improved brass life.
If it were true that full length sizing would cut group size by 1/4 moa, many would depart with another $300 and add a set of custom reloading dies to their $6000 to $8000+ custom rifle/scope outfits.
So I wouldn't dismiss the discussion on the potential benefits of full length sizing preferentially to neck sizing, based on the cost associated with a set of custom full length sizing dies.
Mikecr
Well-Known Member
You haven't completed the testing.
So you don't know best seating yet.
So you don't know best seating yet.
phorwath and rcoody,
Best accuracy does not require a full length sizing die whose chamber matches the barrel's chamber minus .001" all the way around. The only thing that makes the bullet center perfectly in the chamber throat when fired is the case shoulder mating perfectly with the chamber shoulder. The case body can have a lot of clearance to the barrel chamber, but when the firing pin drives the case full forward centering its shoulder dead center in the chamber shoulder, that takes the case neck and the bullet in it to dead center, too. Of course, the back end of the chambered case at its pressure ring is usually pressed a thousandth or two off chamber center by the extractor's pushing it that way. If a perfectly straight .308 Win round's back end is .001" off chamber center and its shoulder centered in the chamber shoulder, its bullet tip will be about .0005" off center in the chamber throat opposite that of where the case is touching the chamber wall.
Benchrest folks sometimes have folks make custom dies with their chamber body dimensioned to size fired case bodies down .001" in diameter. That's for long case life. Long before that was popular, high power match rifle shooters were honing out commercial full length sizing die's necks to a couple thousandths less than a loaded round's neck diameter. They often got 50 to 60 reloads per case with maximum loads. Nowadays, the benchrest folks get several more reloads per case because they're work-hardening the brass a little less. A recent benchrest record was set with cases having been full length sized over 100 times.
Sierra Bullets' tool and die shop honed out commercial full length sizing die necks back in the '50's so their ballistic tech full length sizing their cases fired in SAAMI spec chambers could get their best match bullets to shoot into the ones (under .002") in their test range. Nowadays, they use Redding full length S dies with bushings on cases they're made for and their 10-shot test groups with match bullets are as good as benchrest aggregate records at 200 yards. All bullets shoot under 1/2 MOA. Like the benchrest crowd, sometimes their groups are well under 1/10 MOA equaling the few-shot match winning ones the benchresters rave about and everyone else wants to equal.
Best accuracy does not require a full length sizing die whose chamber matches the barrel's chamber minus .001" all the way around. The only thing that makes the bullet center perfectly in the chamber throat when fired is the case shoulder mating perfectly with the chamber shoulder. The case body can have a lot of clearance to the barrel chamber, but when the firing pin drives the case full forward centering its shoulder dead center in the chamber shoulder, that takes the case neck and the bullet in it to dead center, too. Of course, the back end of the chambered case at its pressure ring is usually pressed a thousandth or two off chamber center by the extractor's pushing it that way. If a perfectly straight .308 Win round's back end is .001" off chamber center and its shoulder centered in the chamber shoulder, its bullet tip will be about .0005" off center in the chamber throat opposite that of where the case is touching the chamber wall.
Benchrest folks sometimes have folks make custom dies with their chamber body dimensioned to size fired case bodies down .001" in diameter. That's for long case life. Long before that was popular, high power match rifle shooters were honing out commercial full length sizing die's necks to a couple thousandths less than a loaded round's neck diameter. They often got 50 to 60 reloads per case with maximum loads. Nowadays, the benchrest folks get several more reloads per case because they're work-hardening the brass a little less. A recent benchrest record was set with cases having been full length sized over 100 times.
Sierra Bullets' tool and die shop honed out commercial full length sizing die necks back in the '50's so their ballistic tech full length sizing their cases fired in SAAMI spec chambers could get their best match bullets to shoot into the ones (under .002") in their test range. Nowadays, they use Redding full length S dies with bushings on cases they're made for and their 10-shot test groups with match bullets are as good as benchrest aggregate records at 200 yards. All bullets shoot under 1/2 MOA. Like the benchrest crowd, sometimes their groups are well under 1/10 MOA equaling the few-shot match winning ones the benchresters rave about and everyone else wants to equal.
Thanks for all the input guys.
I ended up seating to .090" off the lands (factory barrel) giving me a cbto of 2.724" giving me a coal of about 3.4. I loaded up h3450 from 57.0gr to 61.5gr with 0.5gr increments (less than 1% change in volume) and shot the following ladder at 300 yds.
I then verified shots 5-10 as I thought they had the most potential with low sd at about 2800 to 2850fps. As you can see. All shots landed in almost identical dispersion with loads 5-7 showing the most potential at about 2800 fps and .5 MOA. Instead of shooting another string I thought that I had good enough results to move forward.
So I will now load 59.0 gr to 60.0gr in 0.2 gr increments to find my ocw and then work within my seating window that I previously established. I plan on changing the seating depth by .010" +-.040" from my current .090" from the lands.
Do you guys recommend redoing my initial seating depth test instead?
I ended up seating to .090" off the lands (factory barrel) giving me a cbto of 2.724" giving me a coal of about 3.4. I loaded up h3450 from 57.0gr to 61.5gr with 0.5gr increments (less than 1% change in volume) and shot the following ladder at 300 yds.
I then verified shots 5-10 as I thought they had the most potential with low sd at about 2800 to 2850fps. As you can see. All shots landed in almost identical dispersion with loads 5-7 showing the most potential at about 2800 fps and .5 MOA. Instead of shooting another string I thought that I had good enough results to move forward.
So I will now load 59.0 gr to 60.0gr in 0.2 gr increments to find my ocw and then work within my seating window that I previously established. I plan on changing the seating depth by .010" +-.040" from my current .090" from the lands.
Do you guys recommend redoing my initial seating depth test instead?
I'd stop where you are and used either load that produced the images posted. There's not enough difference in them to waste barrel life and components to see any significant difference. A 10 to 20 percent spread in group sizes for the shot numbers you're using is very normal.
