New 308 155 Sierras, OAL ?

[zeroveez]

"New 308 Sierra 155's, OAL for TR" the recieved wisdom is that the new Sierra 155's need to be loaded so as to have about 40 thou of jump. In the past, using Lapua 155 Scenars, I have been in the habit of loading them with about 10 thou of jump, and have been satisfied with the results. Does anyone have either experience or opinion concerning what the cartridge OAL with the new 155, 308 Sierra's should be?

[20series]

depending on your chamber you might not get too near the ogive anyway.

SMK's dont normally mind a jump anyway

Alan

[rox]

"New 308 Sierra 155's, OAL for TR" the recieved wisdom is that the new Sierra 155's need to be loaded so as to have about 40 thou of jump. In the past, using Lapua 155 Scenars, I have been in the habit of loading them with about 10 thou of jump, and have been satisfied with the results. Does anyone have either experience or opinion concerning what the cartridge OAL with the new 155, 308 Sierra's should be?

Do you mean the 2156's? (SMK HPBT 155 gr 'Palma').

The person I would ask about these is the spawn of your loins; I think he has used them quite a bit. 0.040 sounds long. Scenars are quite a different beast, so I would ignore any experience related to them.

..

[TattooedGun]

I've been using the 2156's with a 20 thou jump and theyre pretty good... no real 100 yard groupings to show though, but they do very well for me at 3 and 600 yards with my TR...

[zeroveez]

"Do you mean the 2156's? (SMK HPBT 155 gr 'Palma')". I do.
"spawn of your loins" he says 40 thou is OK. I am about to try 5-10 thou, either this w/e, or next. When are you going to get rid of that Grunig and get a decent TR rifle?

[IainWR]

My GB team experimented endlessly with Scenars. We could not get a solution that worked reliably in more than one rifle - utterly useless for a team of 21 with nearly 30 rifles between us.

We eventually loaded Sierra 2156 (bought at a good price surplus from the GB2011 Palma Team) to 2.912 OAL, which is the mean equivalent of Sierra 2155 at 2.800" OAL (eg NRA RUAG 155). It worked well. The main problem dimensionally was that a 2.912" round will not unload by normal extraction from a Swing action - you have to take the bolt through the catch to get the bullet tip past the front of the loading port.

We found no issues related to loading length in terms of accuracy. Jumps varied from about .005 to about .070 with no correlation to results. This corresponds to the NRA opinion that Sierra bullets are extremely tolerant to widely differing chambers.

Iain
Captain of Great Britain Target Rifle Team to South Africa 2012

[Dangermouse]

I know on paper / ballistic programs these Palma 155's out preform the standard older SMK 155's, Has anyone seen any real increase in performance in the real world?

DM

[GazMorris]

As Dad and I have been "outed" I may as well chip in at this point!

I've been using the 2156s for nearly two years and have found them to be an excellent bullet. After some playing, a 40 thou (0.04") jump seems to work very well in my last rifle with the Sierra 2156s and the Berger 155.5s. It was the longest jump that I tried and worked the best, so longer jumps (per IWR's GB Team) may be better. This was not a statistically valid analysis, but gave an indicative result.

That said, I generally shoot the old 2155 Sierra with a 20 thou (0.02") jump, but I made up and shot a batch of ammo aimed at cloning RUAG with a jump of something like 60 thou (0.06") which shot just as well.

On a final note, I need significantly less elevation at 1000 yards with the 2156 than with the 2155. I've never done a like-for-like comparison between the two for windage but reckon that I need about 10% less wind with the 2156 than with the 2155.

Cheers,

Gaz

[ovenpaa]

The 2156 does look a bit 'pointier' however I have not had chance to try them yet.

Outed Gaz?

[GazMorris]

Outed Gaz?

As being father and son, that is.

Gaz