seating depth 208 amax 300rum

[RUMBALL]

Hi guys,
went for a shoot at the range with handloads some promise with 90gr and 91gr AR2225 two touching one left of POI with both loads the 90gr load the third shot is about inch left and down the 91gr load is about 1cm left and down.
SO im thinking some tweaking is in order so back home thought I would check measurements to the rifling now past measurments came up 2.945 with comparator.
Last time I measured I used hornady OAL gauge with dummy case with slight pressure on gauge to get past measurement but this time I applied a bit heavier pressure and the proji went in to 3.133thou on the orgive that 88thou longer than previous measurement.
So next I sooted up a proji and began seatting it in a fire formed case and got no rifling marks until 3.110 at the orgive so Im assuming the 3.133 measurement is jammed so Im asking what the heck was I getting my very first measurement of 2.945 from this rifle has approx 40 rounds down the tube so cant see it been throat wear.
Im no longtime guru handloader so your thoughts would be helpful have I missed somthing or have I had a DOH! moment.

Cheers Rumball.

[Footsore]

Were you using the exact same projectile that you used the first time you measured it? With those long bullets it can be very difficult to get a consistent reading even with a comparitor. Also with them even a very small amount of erosion of the throat can mean the bullet can go much further forward than a bullet with a less pointed ogive.

[RUMBALL]

It was same type of projectile not the same one I used in the first measurement but came up the same as first measurement 2.945 on the orgive.
Then did it again until assumed contact on the lands but this time I just pressed a bit harder not much at all and the projectile just fell in about 80 thou more.
Im pretty sure it was jammed in the rifling couldnt be anything else I think the first bit of resistance its on the lands but it only takes the slightest touch to fall in I think I will stick with original measurement or may get someone else to do a measurement then compare.
The thing thats got me stummped is not been able to get rifling marks on projectile when sooted and seated at 2.945 but with OAL gauge the projectile will have first resistance at 2.945 have to go out further to get markings on sooted projectile.

Cheers Rumball.

[trebark]

If you pressed the bullet until the rifling left a mark, that's too much pressure. You need to use the lightest pressure and stop when the bullet stops. My guess is your 2.945 is probably closer to 'on the lands'.

Also, be sure that if you measure your dummy case with the comparator, that you measure your loaded rounds the same way. I shoot the 208Amax in my RUM and have found that there is as much as a .004 variance bullet to bullet.

[RUMBALL]

Originally Posted by trebark

If you pressed the bullet until the rifling left a mark, that's too much pressure. You need to use the lightest pressure and stop when the bullet stops. My guess is your 2.945 is probably closer to 'on the lands'.

Also, be sure that if you measure your dummy case with the comparator, that you measure your loaded rounds the same way. I shoot the 208Amax in my RUM and have found that there is as much as a .004 variance bullet to bullet.

Hi Trebark,
I do use it as you explained and have done with all my rifles with no problems so as I started second guessing myself I took it to the gunsmith just to get a comparison he used all my equipment.
He used my OAL gauge first and could feel the first resistance that I usually use as my measurement then gave the slightest bit more pressure and It went in just like it did for me then he made up dummy round using new projectile a fireformed case then began seating until he got slight rifling marks on projectile.
His measurment just touching the rifling is 3.141 different to my assumed jammed measurement of 3.133 on the orgive and I have been seating at 2.945 as you know so that a big difference now the smith being a bench shooter aswell who reloads also one would assume he knows what hes on about so guess I could carry on where I was or start fresh and work up looking for pressure sighnes.
As Im only single feeding no need to worry about mag length and theres not to much info on OALS on the 208amxes in standard senderos to compare to plenty on the bergers so just see how I go.

Cheers Rumball.