seating depth for .308 155 lapua's

[300ultramag]

i have some questions regarding oal of the 155 lapua's in .308.i am shooting a rem700 vs in .308 with a 26" tube.i have worked up a few different loads using imr 4895 and varget. i really wanted to seat the 155's at the lands as i load individually.but my chamber oal is 2.966" if i were to load to this dimension i would only have approx..136" of the bullet surface contacting the neck!! no counting the boattail.i can't find any info that speaks to minimum bullet seating.i know i could get better accuracy seating out further than the 2.886" i have settled with. .081"jump seams excessive.i also started seeing primer flattening and extractor marks on my lapua brass at 44 grs. of imr 4895.my current load of 45.5 imr 4895 yields me only 2800 fps using my ced chrony.my varget load of 46.0 grs. yields me 2825 fps.it too shows minor pressure signs.both these seam very slow when comparing all the info supplied here and on other sites.will i have problems with my cases[donuting] if i seat to the lands??? iam using 155's exclusivly because am shooting f class to 1000 yrds. sorry for the rambling hope you can help.

 

[LarryDScott]

Do you actually know that your accuracy is better in this rifle seated closer or do you think it should be????
I had a Factory VSSF 308 and did lots of powder and bullet testing, and the same w/seating depth. My conclusion was that my rifle didnt care where the bullet was seated. It would put 5 into a half inch at 200 on some occasions and 3/4 anytime if I did my part. This rifle disproved everything I thought I knew about seating depth. Larry

 

[billmo]

Seating depth for the .308 is kind of a puzzler. At one time I thought the best loads for my .308 were close or maybe even jam to lands. However, I got to looking at some of the accuracy loads here on the .308 load page and some other literature also and realized that there were some pretty dog gone accurate loads with the bullet simply seated at 2.800 or there abouts. So, I loaded up a couple of my pet loads and headed to the woods to check' em out. My results proved that the old stand-by seating length was just as good and in some cases better than anywhere close to the lands. So don't be afraid to seat your bullets out from the lands with this caliber. Further, it has been known to happen many times, when a shooter or handloader could not get anything to come together in the accuracy dept. by jamming to lands and/or close to them with some of the popular "accurate calibers" of the day, by backing away .020 or even more they would find that sweet spot they had been looking for for several failed attempts. There is always that exception to the rule when you are dealing with rifles and handloads. Never say never or always with these critters. They can make you feel very tiny sometimes when you have tried it all. I hope this helps. Bill

 

[MSwickard]

i also started seeing primer flattening and extractor marks on my lapua brass at 44 grs. of imr 4895.my current load of 45.5 imr 4895 yields me only 2800 fps using my ced chrony.my varget load of 46.0 grs. yields me 2825 fps.

I'm puzzled by this comment! First off I know the books state you can load up to 47.5C with IMR 4895 w/155 Sierra. First I find it unusual that you would increase your powder charge 1.5 grains if you saw pressures at 44grs?

I also posted to your question on the reloading forum concerning this cartridge. Not being familiar with the 155 lapua bullet, but if it has more bearing surface I could see pressures being higher at a lower charge weight.

Additionally, your speeds in the 2800+ seem about right. I would probably look at another powder like N140.

Lastly, I would first figure out why you are getting pressure indicators on lower charge weight loads. Again,I think you may have a headspace problem and the case is slamming back onto the boltface flattening primers and leaving an ejector mark.

Have you measured the diameter of your cases at the web campared to a new case. have you checked the inside of the cases to see if there is a ridge near the web? Good things to do.

Mike

 

[300ultramag]

mswickard; my initial pressure signs were fed210 primer flattening at the edges,but i read elswhere that these primers are known for this.i also read about some lapua brass being unusually soft.to set my headspacing i removed my firing pin and started sizing a case using shim stock at .012" between the shell holder and the full length resizer, the bolt was stiff to close to stiff for my liking at .010" it would close with just minimal resistance.this what the die is set at now.i also added a redding floating carbide sizing button.i am going to try and seat out to the lands.dropping my charge down of course.at 2.966" i should have about .165" in the case.after 4 reloads i am consistantly trimming 8-10 thou.to get back to my lead of 2.008"i have checked inside the cases with a 90 degree scribe and cannot feel any ridge.my primer pockets were also a bit loose on a few cases.maybe i should size with the .012"shim and live with the firm bolt.

 

[MSwickard]

300um

Well you covered everything I would have done in the inital setup of your dies. Personally, I use both fed 210's and 308 Lapua brass and have not seen anything that is problematic. It is possible you may have some soft brass. Only thing to do is try a different lot.

If you can get enough neck tension on the bullet out at the jam, I would see how it shoots then work back in 0.010" increments. Also, it may help going to a slower powder. I'd look at Varget which you are using as well as N140.

Lastly, are you shooting a factory barrel or a custom chambered barrel?

Let us know your findings.

Mike

 

[300ultramag]

i am going to try and seat to the lands and try varget and imr 4895 again,would dropping 2 grains be enough.to answer your questions.i am shooting moly lapuas and my barrel is factory tube.i have been shooting decent groups at 100 yrds.sub .5's.will let you know how i make out.
thanks