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Chasing the lands vs Jam

wywindsor

So with all the internet advise I found this on my 6.5 prc with 144 match kings.

Cortina method Jam
2.424 CBTO

Wheeler Method Bare bolt drop
2.365 CBTO

Speedy Method Barrel off bullet seating with no drag on cartridge removal.
2.365

All test were Lapua brass. And verified twice with new brass and bullets.

The gun is a Savage trail hunter. The first 20 rounds were factory Hornady 143 eldx which averaged 2'' groups at 100 yards. The next 20 was Hornady brass 54gr. 4831sc. Speed 2909 avg. Group avg .75. The factory loads were 9gr. apart loaded. The spent brass 5gr. apart. The factory ammo had some resistance on bolt closure. Not sure the CBTO. The reloads were at jam. Where to start is the question. Not wanting to waste components. But with .059 difference. Looks like to the range or ?
 
wywindsor said:
So with all the internet advise I found this on my 6.5 prc with 144 match kings.

Cortina method Jam
2.424 CBTO

Wheeler Method Bare bolt drop
2.365 CBTO

Speedy Method Barrel off bullet seating with no drag on cartridge removal.
2.365

All test were Lapua brass. And verified twice with new brass and bullets.

The gun is a Savage trail hunter. The first 20 rounds were factory Hornady 143 eldx which averaged 2'' groups at 100 yards. The next 20 was Hornady brass 54gr. 4831sc. Speed 2909 avg. Group avg .75. The factory loads were 9gr. apart loaded. The spent brass 5gr. apart. The factory ammo had some resistance on bolt closure. Not sure the CBTO. The reloads were at jam. Where to start is the question. Not wanting to waste components. But with .059 difference. Looks like to the range or ?
Click to expand...
I’d say start at .020 off the lands
 
Listen to Eagle Six but maybe go to .015 in then start backing out. Term jam is used incorrectly by most. They mean touch. Two different terms. It makes no difference how you measure as long as you get repeating numbers. It is only a reference point. There is no right or wrong answer.
 
wywindsor said:
The gun is a Savage trail hunter.
Click to expand...
Shooting these loads from a magazine ?? This is my method for
For a hunting rifle......After you check your action screws for the
factory torque specs, "leave them alone" !! Well I should say......
Make sure the tang is is floated. Other then that, find out what
your magazines will allow for the components you want to test.
In most cases, touch and jam are meaningless, since the mags
won't let you get there. If they do, find touch and start there.
 
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I have plenty of mag. clearance. The reason I ask is the longest cbto or coal is a hard jam. Using the Cortina method to seat the bullet. I know this is dependent of seating tension. I have .0015 interference. So with the response here I take it light to no resistance is where you want when the bullet. This will give me a correct starting point.


Thanks Ray
 
Eagle Six said:
I wouldn't want to leave .020" on the table, I would start at touch/light jam and work back, but I'm not shooting that cartridge or those bullets.
Click to expand...
AGREE, I start at .020- .025 "Off" Jam point, ONLY to Find, the Rifles MAX Powder charge ( Pressure ) then, I move bullet IN with, a 1/2 to One grain LESS Powder and,.. a Light Jam.
Then IF, necessary move bullet Back, in ,005 to .010 increments til,.. "Happy Tune".
When, I started Jamming, the 107 gr. SMK Bullets, in my 6 XC, the group's SHRUNK,.. noticeably.
 
He has video's on it called chasing the lands is stupid or to some effect. He uses his preferred neck tension. Seats the bullet long, just to where the bolt won't close with out a little force. Lubes the bullet and uses the barreled action to seat the bullet to jam.
 
What Erik does that I think that is very useful is when he loads a block of rounds, he loads a few a bit longer than the current tune and he shoots them. If they shoot with the group in size and POI, he uses that as his seating depth for the next time. He assumes that as the lands wear, the optimal seating depth is going to stay put or get longer, so by checking a few long each time out he maintains an optimum seating depth. It may or may not stay a constant distance from the measured lands, which is what he considers chasing the lands. Erik doesn't bother with trying to measure a touch seating depth, he rams as much jam as is physically possible in his chamber and brass and builds his tune working out from there. To wywindsor's point, he uses the lands to force the bullet in from an extra long seating depth and measures that. I tried it once and the bullet stayed stuck in the lands - maybe I didn't lube it well enough. I also could have removed my extractor and just very carefully push the bullet out using a coated cleaning rod from the muzzle end.
 
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