Chasing the lands

[tn noshooter]

When jamming how do you determine how much or when you chase the lands. Do you check the lands every 100 rounds 200 300 or so on.I"m new to this concept always jumped before but now found a load next to the lands and just don"t know how to go about it
Thanks in advance

 

[Sniper338]

When jamming how do you determine how much or when you chase the lands. Do you check the lands every 100 rounds 200 300 or so on.I"m new to this concept always jumped before but now found a load next to the lands and just don"t know how to go about it
Thanks in advance

Easiest answer is when your groups start opening up.. then scoot closer. Theres not a number of rounds. Too many variables

 

[ShootDots]

When jamming how do you determine how much or when you chase the lands. Do you check the lands every 100 rounds 200 300 or so on.I"m new to this concept always jumped before but now found a load next to the lands and just don"t know how to go about it
Thanks in advance

There are a few "rules of thumb" I use. 1.) when I shoot an entire match (3 x 20 + sighters) and I am back at the reloading bench, I check with a Stoney Point O.A.L. guage with the proper caliber insert. Chances are it has moved from 1-3 thousandths. 2.) Every time I open a new box of bullets that are from a different lot>>>whether I have shot a match or not. 3.) after I scrub down the barrel with JB>>I have found that when I do that, for whatever reason the throat has moved "more than the usual" couple of thousandths.

 

[cheek9075]

Thanks for posting the video... Good info. I always remove the firing pin to determine the case size, but have never done it to find oal.

 

[comagutsa]

Yeah I use that vid to find mine and chase them.. I check them every 100 rounds and adjust

 

[KenOath]

Check your lands regularly, some barrels wear faster than others. No point in spending the time and money finding the best powder charge and seating depth and not chase the lands.

Rushty

 

[mikecr]

Well, if you do full seating testing(like Berger's recommended) and find something off the lands, then you won't ever need to chase anything.
If OTL costs to much loss in peak pressure for your cartridge, you could add neck tension or faster powder, to recover that attribute while OTL.

 

[TAJ45]

Well,
If OTL costs to much loss in peak pressure for your cartridge, you could add neck tension or faster powder, to recover that attribute while OTL.

Very good physical logic. This had never occurred to me. However it does open up another set of incremental variables, such as half thou. neck bushings, amount of neck to bearing surface contact (back to seating depth). Yessir, always interesting, this precision reloading.

 

[Brians356]

There are a few "rules of thumb" I use. 1.) when I shoot an entire match (3 x 20 + sighters) and I am back at the reloading bench, I check with a Stoney Point O.A.L. guage with the proper caliber insert. Chances are it has moved from 1-3 thousandths.

Really? You've seen 3 thousandths erosion from less than, say, 70 rounds fired? Huh.
-

 

[jlow]

I check them every time I clean. I chase them regardless of jam or jump.

Tom

Sounds good Tom! I imagine you adjust powder weight as you seat longer and increase volume?

 

[Macropod]

With the 308 I find the tune is maintained by increasing the charge by 0.1gns for every 0.010" throat wear. This formula seems very close when using AR2206 (H4895) and 155gn projectiles that are seated to just touching. Essentially the case volume increases as the bullet is seated further out and the charge adjustment maintains the tune. Other cartridges/loads may differ.

Keeping slightly on the high side of the node allows a little more time between powder load changes.

 

[Hengehold]

I usually jam about .020 for slow fire With .001 NK tension. In the past I have just adjusted after group opens up (approx after 700/800 rds with my 6XC).

With my 6.5-284 I have had similar concerns as you with throat erosion so I have been measuring throat with stony point tool. After 370 rds (35% of the barrel life) I have measured virtually NO throat erosion (.005).

I think a good rule of thumb would be to measure throats after 300-400 rds.

-T

 

[Jet]

Well, if you do full seating testing(like Berger's recommended) and find something off the lands, then you won't ever need to chase anything.
If OTL costs to much loss in peak pressure for your cartridge, you could add neck tension or faster powder, to recover that attribute while OTL.

Might be just me but I've found that even when jumping bullets I need to pay attention to what the throat is doing. Berger's article (the one I read) discusses using a process to find a wide seating depth window when tuning to maintain a .4"-.5" tune at 100yds through many firings. This will work for the vast majority of rifle shooting situations but when tuning I'm looking for a seating depth that will shoot much smaller then that and when testing at distance must definitely be sub .5 MOA. Once found I check it after every match then verify it on the range prior to loading for the next match.

Good Shooting

Rich

 

[MagnumManiac]

I'm with Mikecr, I used to chase the lands after every 200 rounds or so, I could measure accurately that the throat had eroded on average around .030"-.040".
When I was unable to get to .010" off the lands I would cut a thread off and rechamber. This would normally happen 3 times during a season.

Nowadays, I simply check velocities as the season progresses and adjust the load to get back to the known velocity, this poses no problem as the pressure is dropping from the throat erosion.
If the load proves to open up, I will tweak the seating depth to bring back the sweet spot.
I now get 2 seasons from a barrel, only needing to set back and re-chamber twicw in that time.
I don't like changing barrels often, it screws up my loads and I hate tweaking loads on new barrels as they run in.

Cheers.

 

[rardoin]

Really? You've seen 3 thousandths erosion from less than, say, 70 rounds fired? Huh.
-

I have had a couple of barrels, that when 'near the end', the throat would move out near 0.003" over about 80rds. I had one that jumped .011" after two 68 shot matches/12 or so prematch sight in/velo verification shots...so it moved that far in about 150 shots. When I scoped it, the pictures were pretty nasty.

 

[Brians356]

I have had a couple of barrels, that when 'near the end', the throat would move out near 0.003" over about 80rds. I had one that jumped .011" after two 68 shot matches/12 or so prematch sight in/velo verification shots...so it moved that far in about 150 shots. When I scoped it, the pictures were pretty nasty.

Wow, ok.

I ran set of 50 Tubb Final Finish fire-lapping bullets through a '68 R-700 in 6mm Rem. The comparator length to ogive, touching the lands, only increased about .010" to .015" as I recall. Lapping velocity only about 2500 fps, but still ...
-

 

[dkhunt14]

Check your lands regularly, some barrels wear faster than others. No point in spending the time and money finding the best powder charge and seating depth and not chase the lands.

Rushty

Also some cartridges wear them faster. I shot a 308 Baer and you could move as much as .015 every 2 to 3 matches. Which would be max of 102 rounds depending if you made the shootoffs. I switched to a 300 WSM and can shoot 3 seasons with as little as .005 movement. Which is around 900 rounds. Matt

 

[BenPerfected]

Is it an option to just use your tuner to keep up with land erosion?