How much jump to lands

[stephentri]

Hi reloading for a.223 using 75grain amax what do most people find works best up touching or a few thou back

Thanks Stephen

[dannywayoflife]

Every rifle will be different but when I was running these in my T3 I found they had to be kissing the lands to shoot well.

[gunner]

Well my 223 ai was throated for this perticular bullet and i finalized at 2545 , with about 10 thou jump . What's your chamber factory of custom ? Also what barrel twist 8 ? Ideally if you haven't already done it , find out your col when touching then ideally knock up 25 for a col test with 5 shots per group . And prob 5 thou difference in each 5 . Ideally start test with a few surplus rounds to foul the bore ( if its clean ! ) and wait for barrel to cool slightly between shots . I allow 2mins between EACH shot ! Some may say shoot 5 then let cool for 5 minutes etc .

 

Have you done a ocw test ? This could be key to better accuracy after this col test ! Good luck with it tho . Cheers tim .

[Brummy Mark]

Hi, im at 2.545 coal as well, for me this is 40thou off the lands and as long as I can go for feeding from an AI polymer 223 magazine.

Mine was chambered/throat for 90gr vld.

However this is not what you should do.

You should see what the maximum coal is for rifle, if its a standard factory barrel then you wont be able to load them very long

and should start your loads from a reloading manual for safety,

I tried 75gr amax in steyr pro hunter with a 1:9 twist barrel, couldnt load them long enough to get enough powder in for an MV to stabilise them, you need a fast twist.

If its heavier round try 69grainers.

If you dont want your 75gramax Ill happily buy them off you!

[stephentri]

Hi it's a custom barrel chambered for 75grain amax touches the lands with a oal 2.506 iam using n140 powder 1 in 8 twist 24 inch barrel

[Big Al]

I would start at touching the lands and then jump back in .0.010" increments to say 0.060 away - this should give you enough groups to see where your accuracy is, once you fine the best group you could then try some 0.005" either side of that best length. Save yourself a lot of barrel life by not working in smaller increments than 0.010" at the beginning and then only drop to 0.005" changes to see if it improves either side of you best length.

 

If you haven't found what your looking for then dont be afraid to go back much further, I have a great load (albeit a different caliber) that is sitting 0.140" back from the lands. All this changing of the seating depth by 0.002 increments is misguided in my opinion, if barrel/bullet combos were that sensitive few people would have accurate rifles and factory rifles just wouldn't shoot as good as some of them do with with factory ammo.

[gun nut]

Big Al has the right idea, but do your initial jumps in 40thou steps, somewhere between 10 and 150thou off the lands you will see better groups and refine from there. 2thou steps are meaningless and will only waste your time and components. PS the 40 thou steps weren't my idea, it's how Berger bullets recommend you find the right seating depth for their bullets.

 

Mike

[Big Al]

Big Al has the right idea, but do your initial jumps in 40thou steps, somewhere between 10 and 150thou off the lands you will see better groups and refine from there. 2thou steps are meaningless and will only waste your time and components. PS the 40 thou steps weren't my idea, it's how Berger bullets recommend you find the right seating depth for their bullets.

 

Mike

 

Yes, I have in the past jumped back at 0.040" increments and found the right depth quite easily Mike, I suggested 0.010" jumps in this instance because its Amax and I wasn't sure if they responded to such obvious jumps as well as the Bergers VLD type of bullets do.

 

I spoke with Callum Ferguson a while ago about this subject and he also felt that tiny adjustments were meaningless and a waste of time and components.

[jcampbellsmith]

I'd make two comments:

 

Small changes to seating depth can be critical and a number of very experienced people talk about fine tuning a load in 4 or 5 thou steps.

Sometimes your combination of brass prep, bullet, powder, primer and testing technique just don't work. Don't be afraid to abandon specific bullet/powder/primer combinations.

 

Regards

 

JCS

[gun nut]

JCS,

 

there is of course a time in your load development that you get down to +/- 5 thou, but it's at the very end of load development. I wasn't suggesting otherwise, just that there's little point it starting off with such small increments.

 

Mike

[jcampbellsmith]

JCS,

 

there is of course a time in your load development that you get down to +/- 5 thou, but it's at the very end of load development. I wasn't suggesting otherwise, just that there's little point it starting off with such small increments.

 

Mike

Mike. I agree. I tend to tune by powder weight first and then try tweaking the seating in & out by small amounts. Regards JCS