.308 155 AMax Shooters....jump or jam?

[JLM]

Gents,

For those of you shooting the 155 Amax in your .308's, are you jumping them, jamming them, or what?

Some of the info I have found so far seems to indicate that unlike say, the SMK, they are not very jump tolerate.

If you have any advice about your seating depths, would be appreciated, thanks! Loads too for that matter. I found a few posted here but not many.

 

[bohem]

Re: .308 155 AMax Shooters....jump or jam?

My dad shoots them on a jam, I shoot the 178's from my 06 on a jam.

I tried jumping the 178's about .010 and it was OK, but touching the lands gave me much better results.

 

[Jerry R]

Re: .308 155 AMax Shooters....jump or jam?

I just worked up a 155 AMAX load and found that when I jammed them in about .020" they shot far better than just touching the lands with an average velocity of 2984 and no pressure at all from a 26" Rock 5R. I would have never believed it had I not done it myself.

The load was with 47 gr of VARGET and left a little smoke on the shoulder so I think I may try a smaller dose of Benchmark and see what I come up with.

 

[JLM]

Re: .308 155 AMax Shooters....jump or jam?

Thanks gents!

 

[Greg Langelius *]

Re: .308 155 AMax Shooters....jump or jam?

.

 

[JLM]

Re: .308 155 AMax Shooters....jump or jam?

Greg, interesting points.

Thing is (for ME anyway) I can jump SMK's and they shoot like a house on fire. In fact I can load them to 'book length' and they are GTG.

I haven't shot any Bergers yet, but everyone seems to say you have to jam them. They have a secant ogive design just like the A-Max.

I wondering if its the ogive shape:

Tanget=jumpable
Secant=jam

 

[esorensen]

Re: .308 155 AMax Shooters....jump or jam?

It appears that Berger is moving away from their on or into the lands stance. Eric Stecker put out a letter stating that there was too much evidence from "new" Berger shooters to be ignored. The "old" match shooters put them on the lands and that was accepted as standard. Now the Bergers are being sold as a hunting bullets and hunters are leary to put them into the lands as an ejected live round could potentially come apart and pour powder into the action. So, the evedence provided by the new shooters is they also shoot very well jumped (mag length). It was more of a seating window if I recall. Just see what your rifle likes.

 

[JLM]

Re: .308 155 AMax Shooters....jump or jam?

Well I got a chance to test a few loads today. The best one shot .75 MOA for a 7 shot group.

Virgin Lapua Brass
BR2's
45gr Varget
Seated 2.218 measured to the ogive (same jump as my 175gr SMK load)
Velocity/ES/SD: Someone send me your chrono <G>
COAL: 2.840

I stopped at 45.5 for no particular reason than that's where I stopped. No pressure signs at 45.5 but it opened up like a mother
at that charge.

Any suggestions? I really need to get a Hornady Seating Depth tool, and a chrono for that matter.

 

[Queequeg]

Re: .308 155 AMax Shooters....jump or jam?

Great advice.

I have been getting poor to mediocre accuracy with the 155 AMAX with a variety of powders (Varg, RL-15, H & IMR 4895, 4064). They have all been loaded book to mag length of 2.800"-2.820" give or take a couple thou.

I'll inertia pull (Just pop em out longer, not completely pulled) a dozen or so and reseat them to 2.840" for single loads to see if that is the solution.

 

[esorensen]

Re: .308 155 AMax Shooters....jump or jam?

As far as a seating depth tool, I don't have one. I use an uncharged/unprimed case as my "dummy round". I have a fiberglass rod that I insert into the bore muzzle first. I then seat the bullet of choice obviously long. I then insert this case into the chamber and give it a push. You can feel it hit the lands. You can feel pressure on the back of the case as you push the rod and unseat the cartridge or push the rod with the case. I then reseat this 10 thou shorter and repeat over and over until it slides back and forth with no resistance. I can get a very accurate picture of oal to the lands with this technique. It may take a while, but has proven to be quite accurate. I then use the electric pen to engrave the date/oal/seating depth etc. on the case and use it as reference. If you have any questions, let me know.

 

[Grump]

Re: .308 155 AMax Shooters....jump or jam?

"reseat them to 2.840" for single loads"

Hmmm. I think my M1A will take up to that long and still feed. Or maybe 2.83...

IIRC, the A-Maxes touch the lands in my rifle at 2.87 or so. Jumpy. Nosler 168s touch at 2.90. More than 70 rounds through the new barrel and have had only 2-3 good groups. One of them was with the 155 A-Max.

 

[JLM]

Re: .308 155 AMax Shooters....jump or jam?

Hopefully I can do some more testing this week and report back.

 

[JLM]

Re: .308 155 AMax Shooters....jump or jam?

Anyone else have a good loads?