"Off the lands" ....

[garandman]

I'm bad at searching (never find what I'm looking for) so if this has been asked a billion times, please forgive...

But what's the deal with adjusting OAL to say 10 /1000's off the lands, or 20/1000's off the lands? Does it really make a difference? Is there a standard distance?

I'd imagine every rifle chamber is different, so I'm guessing what works for other 6.5Creed rifles won't necessarily work for mine.

Any help / explanations appreciated.

 

[Rthur]

Make a dummy round(without powder or primer). Seat the bullet of your choice long, as to engage the lands. Color the bullet with a sharpie. Chamber the dummy round in your rifle. You will see the lands marking the bullet. Carefully seat the bullet in further a few thousandths at a time. Recolor the bullet after each time you chamber . When it doesn't leave marks anymore this is your col to the lands, This will tell you your max col(cartridge overall length). Now that you have this number you can use it to test your bullets at .0XX amount of jump. Some are jump tolerant and some are not. This is also a way of fine tuning a good load.

R

Also a bullet comparator such as hornady or Sinclair sells can make this more accurate. Measured at the ogive.

 

[Garvey]

Make you a dummy round(without powder or primer). Seat the bullet of your choice long, as to engage the lands. Color the bullet with a sharpie. Chamber the dummy round in your rifle. You will see the lands marking the bullet. Carefully seat the bullet in further a few thousandths at a time. Recolor the bullet after each time you chamber it. This will tell you your max col(cartridge overall length). Now that you have this number you can use it to test your bullets at .0XX amount of jump. Some are jump tolerant and some are not. This is also a way of fine tuning a good load.

R

Also a bullet comparator such as hornady or Sinclair sells can make this more accurate. Measured at the ogive.

^^this^^

Also, of late, I've been splitting the neck of a piece of brass to give it almost no neck tension. I've had more consistant results with my measurements. I start each rifle and load even with the lands or .001" jammed (as long as it'll fit in the mag), find the powder charge range it likes, then play with seating depth if needed.

 

[garandman]

Actually I bought a 6.5 modified case and a Hornady OAL gauge.

I'm not so much interested in the "how" as I am interested in the "Does it really help improve accuracy?"

 

[Jig Stick]

There are a few reasons for working with the lands.

First: When working up powder loads, you always want to start with the bullet jammed into the lands. Work up your loads and see what shoots good, all while looking at your brass for pressure signs. Once you find a good powder charge that shoots good, then you can start coming off the lands and find what seating depth your bullet likes By working up powder charges with the bullet jammed, you will protected yourself from potentially dangerous over pressure issues, For example: a powder charge of 70g behind a bullet OFF the lands may not cause any pressure issues. But if you put that 70g behind a bullet jammed into the lands, you may have a dangerous situation.

Second: Some bullets like to be jammed, and product the best accuracy when so. For example...VLD's, AMAX like to be jammed. if you back off the jam, the groups open up (atleast in my gun). Take Barnes triple shocks....they hate being jammed. shoot like crap jammed. back it off, and they group much better.

 

[Garvey]

My observation of a .22-250, a .243, a .260 with 130 Bergers, a .260 with 140 A-Maxes, .308 Win, 7 Rem Mag has been powder charges is the most important factor in the experiment. All other factors are the control in the experiment; i.e. brass, trim length, primer, powder lot, bullet relationship to the lands. Adjust powder charge to find the sweet spot, then move to seating depth. Again I've started all of those rifle/ load combinations even with the lands and have produced sub MOA shooters out of all of them. I have not went back and adjusted seating depth. Many guys do, but I've not felt the need.

 

[808Huntress]

Actually I bought a 6.5 modified case and a Hornady OAL gauge.

I'm not so much interested in the "how" as I am interested in the "Does it really help improve accuracy?"

Yes! Seating depth will affect accuracy, sometimes to a very great extent.

 

[garandman]

Well, I'm 0.018 off the lands, and shooting 0.60-0.70 MoA w/ 140 A-max's. Something to play with, anyway...

 

[Rthur]

Yes, it can make a huge difference. Try changing your jump by .020, .040, .060 and see what your rifle thinks. I would try more than 5 shots on each.

 

[oldfatguy]

Yes seating depth matters. After doing the OCW to find the charge weight my 260 Rem liked I loaded up three rounds each from 0.010" jammed to 0.060" off the lands in 0.010" steps and shot them round robin just like the OCW run. By far the best group (bug hole) was loaded 0.020" off the lands. You really need to do your own test to see what your rifle likes.

OFG

 

[Squid284]

Now that you can accurately measure it, it provides one more adjustment knob to turn in your reloading process. Keep in mind as you shoot, the throat will errode over time and you will find yourself "chasing the lands" to keep the same amount of jump. I re-measure every 100-150 rounds or so and adjust the seating die appropriately.

Try what Rthur said above and you might be surprised by the results (good or bad).

 

[cecchino76]

I agree with Squid 284 , mesurament keeps on changing, I mesure my chambers every 500+- ROUNDS,
and it is alwais different

 

[MTyotehunter]

I have found most bullets in most guns will do best between .003 and .010 off the lands. But some bullets may like to jump, Ive heared the Berger VLDs and Barnes bullets often like to jump...