Choosing a seating depth to start L.D

dan_351 · Post by **dan_351** » Mon Jun 16, 2014 9:32 pm

Normally i wouldn't be too concerned but after performing a slightl exaggerated test on the wifes 308 with seating depths and making a .6-.7inch group into a 3-4inch group it made me wonder have i just guessed well all the other times.

I am soon to start L.D on Bergers, Woodleighs and ACP in my 260. Is there a general distance from the lands which is safe to find a load then tinker with the final seating depth. I am not limited by any means in my Tikka. I have shot 90gn TNT's and 129gn SST (15thou off the lands) i think it is (if i could remember adam's instructions when setting up my mircoseater?!?!)

jeffk · Post by **jeffk** » Mon Jun 16, 2014 9:48 pm

In my single shot, I start just off the lands and work back once I have a good charge weight.....in my hunting guns, I start at mag length, as that is usually the limiting factor. I used to then try a couple of other groups seated back a few thou, but gave up when there was no real improvement.

Johnno67 · Post by **Johnno67** » Mon Jun 16, 2014 9:53 pm

From my experience with 260 in current Sako, you will run out of space in the mag before touching the lands, hope the Tikka mags differ for you.

JasonF · Post by **JasonF** » Mon Jun 16, 2014 9:55 pm

Woodleighs have shot best just off the lands in several of my rifles.

Dr G · Post by **Dr G** » Mon Jun 16, 2014 10:13 pm

With the catkiller I asked around a lot. On advice from trevort, Shane Clancy and others I started at 20 thou with the intention of tuning it from there once I got the charge right. By the time I settled on the load and realised I could get five shots into an 11mm group at 200m and seven shots into a group with 16mm vertical spread at 300m I stopped developing the load. I still haven't changed the seating depth.

Since then I have typically aimed for 20 thou where other restrictions allow it and so far no clangers for a range of cartridges and projectiles

dan_351 · Post by **dan_351** » Mon Jun 16, 2014 10:18 pm

Thanks guys, very hand to quote each post to reply to off the phone. I have done the bolt release and run a full length mag in the Tikka so there is plenty of room. Couldn't get near the lands with the 90gn to have a second proof where it likes.

I had the feeling the woodleigh loaded very toppically like a standars lead core. Shot the same as every other 150gn in the 308. I used a Sinclair comparator nut so from the 4-5 dummies we made up on the lands I should be pretty right

trevort · Post by **trevort** » Mon Jun 16, 2014 10:26 pm

you know I can honestly say I dont know the distance from the lands of any of my rifles.

I sent a dummy round to Clancy and asked him to cut my chamber so the pill was 20 thou off. Never measured if he did or not

I colour the end of pill with black texta and seat it just in, I chamber in the rifle, the bolt wont close. I seat it down a poopteenth and try closing the bolt. Repeat until the bolt closes and the pill comes out without marks from the rifling and then it is not touching but close. Off we go and try the charges.

I am pretty damm sure my 17m4 is in the lands but I did the powder charge from min with this length and know its safe

My factory 204 ruger was just as long as the round would let me and still fit in the mag, it would have ben nowhere near the lands. Same with my 22/250

I may be giving you the impression that this is the least important part of my load development

3potscreamer · Post by **3potscreamer** » Tue Jun 17, 2014 6:49 am

Don't know about the best depth to start but after the weekends experiment I turned a 2" group 20 thou from the lands into sub inch by going out to 40 thou off.
I did try closer but that was no improvement. That's just my experience with this rifle I'm definitely no expert.
Check out the thread on seating depth the guys were helpful.

Next time as there spotlighting rifles I'll start ten off get my best load if I'm not happy with that I'll start seating deeper until I am. ( without getting to deep into the case).

Please correct me if this is not the best way to do it.
Cheers

bimbo · Post by **bimbo** » Tue Jun 17, 2014 10:24 am

I have always started at 20thou if the pill and mag will let me. This has always seemed to work and even after trying different depths I seem to end back at 20 as the most accurate, although I do own savage rifles which will shoot pretty much anything accuratly :stir:

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