OzFclass

Who's tried them and what did you think ?

I bought a box of 500 recently they were meant to be the 155 grain projectile but the majority weigh 155.4-155.6 grains. They seat at a different length to the old 155. I have fired 30 of them so far and think they are accurate enough, but bolt was hard to open with the same load as the old ones. Have backed off the load for next week and also seated a little deeper in the cases as they may have been into the lands a little.

i dont mind em

Bigtravoz wrote:I bought a box of 500 recently they were meant to be the 155 grain projectile but the majority weigh 155.4-155.6 grains. They seat at a different length to the old 155. I have fired 30 of them so far and think they are accurate enough, but bolt was hard to open with the same load as the old ones. Have backed off the load for next week and also seated a little deeper in the cases as they may have been into the lands a little.

Wow what was your load??
I shoot 215's at 2680fps and no heavy bolt list cant imagine what load you would need to give a 155 a heavy bolt lift it would need to be huge!
Chris

Pommy Chris wrote:

Bigtravoz wrote:I bought a box of 500 recently they were meant to be the 155 grain projectile but the majority weigh 155.4-155.6 grains. They seat at a different length to the old 155. I have fired 30 of them so far and think they are accurate enough, but bolt was hard to open with the same load as the old ones. Have backed off the load for next week and also seated a little deeper in the cases as they may have been into the lands a little.

Wow what was your load??
I shoot 215's at 2680fps and no heavy bolt list cant imagine what load you would need to give a 155 a heavy bolt lift it would need to be huge!
Chris

Would not call 44.4 grains of 2206h a huge load

Primers were looking nice not flattened or cratered. Have seen Winchester match ammo flatten the primers more. Bolt lift was fine was just tight pulling the bolt back

It is something else like bolt needing oil. I have a barrel with 2,000 rounds that has only shot 215's at just under 2,700fps and the cases are the originals I fire formed for the rifle so been shot well over 10 times. No bolt lift issues admittedly palma brass, but pressures will be much higher than you have. To have bolt lift issues with 155's the load would have to be much higher than you are using IMO. What velocity?
Chris

Bigtravoz wrote:I bought a box of 500 recently they were meant to be the 155 grain projectile but the majority weigh 155.4-155.6 grains. They seat at a different length to the old 155. I have fired 30 of them so far and think they are accurate enough, but bolt was hard to open with the same load as the old ones. Have backed off the load for next week and also seated a little deeper in the cases as they may have been into the lands a little.

When you say the new ones seat at a different length to the old ones was your old load set to jump or jam? Are the new projectiles jumping or jamming? Going from jump to jam with a different projectile (potentially different bearing surface) most likely will give you a very peaky pressure at release plus a higher overall pressure.
You need to, if you haven't done it, determine the dimension where the projectile is in contact with the lands and work from there. You need to do this when you change to a different projectile and I also do the check when I change lot numbers with the same projectile. Sometimes you can experience very different ogive measurements lot to lot. Sierra used to be very bad for this. In the past I have even found different ogive measurement within the same box with Sierra.

What action are you using?

Assuming the pressure isn't stupid and the chamber walls aren't rough, or even 'ringed' from a poor chambering job then perhaps it's just tired oversized brass that's done time in another chamber ?

Once fired Winchester brass full length sized and trimmed simply to get them all consistent length previously had been an 8 thou jump but think we think that they may have been a couple of thou into the lands. It's not a bolt oil issue it was the case tight in the chamber. Omark action headspaced two shoots ago and bolt head changed to give minimum headspace. Have made some adjustments and will see how they go this week. Wasn't excessive tight just required a bit more than usual to pop them out of the chamber.

Seems to me that you have little or no primary extraction in your action.

Cannot remember all my old Omark theory - bolt head numbering and how much each changed headspace and whether the length of the locking lugs changes to give different headspace or are the locking lugs unchanged and the recess in the bolt face changes but is it at all possible your bolt head change has changed the primary extraction geometry a tad? Probably talking kerap here. Primary extraction was never the Omark's greatest strength. Maybe time to take to it with a bit of Tig.

Oops, didn't see mike H's post.....

The HBC-P are supposed to be 155.5 gn so I Rekon your box was on the money bigtravoz.
Cheers

Shoota wrote:The HBC-P are supposed to be 155.5 gn so I Rekon your box was on the money bigtravoz.
Cheers

Agreed shoota but they were not meant to be the 155.5. No big deal. Have seen a full grain in weight variation in them though. The majority are in the 155.4-155.6 but have seen some as low as 155.0and as high as 156.0. That said the numbers which are either side of the middle range are minimal.