260 rem question and bullet seating.

[Turbo900rr]

Ok hopefully I explain this right. I loaded up some 260 rem loads with h4350 from 39.0 to 42.0 grains, pushing a 140gr a max. The 42.0 had the best accuracy by far. My problem is I loaded the oal to 2.800 and later figured out that I need to be at 2.900 to touch the lands. So the bullet was jumping a .100! I'm now going to load 2.890 so the bullet will only see .010 jump. My question is this and I think I know the answer. I just want more info before I proceed. I need to start all over again and watch for pressure signs again, correct? I.e. Start at 39.0 gr of h4350 and work up. It's a savage 12 lrp if it matters. Thank you and sorry for the newbie question.

 

[chkunz]

That is the right answer in the back of the book and no one will say that is not the best answer. 42.2 grains of H4350 is a very common accuracy load for the 260 with the 142 SMK (you are using the 140 A-MAX). I have been using this load and find it works well in my application. If you consult the reloading manuals you will probably find that you are not near max loads so you may decide that since you have not seen any pressure signs so far that you do not have to completely start over but no one will fault you if you do. I understand from others that the SMK is very tolerant of bullet jump so that is a consideration if you would like to try the 142 SMK.

 

[nastynatesfish]

If it shoots good why worry about it being in the lands? That's not the solve all for accurate loading. None of my loads are in the lands. My 7'ag jumps .160 at least with 162 amax

 

[Brians356]

You might start at the current 0.100" jump, which you say is pretty accurate, and using that powder charge 42.0, test smaller jumps in .005" increments (jumps .095", .090", .085" etc) to see if it gets even better.

 

[jr600yd]

How accurate is accurate? If the rifle shoots small groups and your happy with them keep shooting. If you want to shoot bench rest or mid-long range keep tinkering. First define what you expect from the rifle/load. What distance you want to shoot. Big difference between itty bitty groups at 100 yds and groups at 600 - 1K. Your on the right track, go for it.

 

['Freak]

How ‘bout load three or so each at 40.8 or 41.2, then 41.6, and 42.0, and seat ‘em out so either on or as near to the lands as you figger you’ll ever put ‘em, then shoot ‘em, all the while watching for signs of increasing pressure. If all’s still well at 42.0 grains while seated on the lands, you can increment the charge up to find the upper limit, load whatever weight looked to be right in the middle of the best node, and then incrementally back the ogive away from the lands looking for where it’ll do its best, knowing (for a good while, anyways) that pressure will only go down as the ogive is being incremented further away from the lands.

 

[HTSmith]

You are for sure on the right page in the hymnal. Mine loves 42.0 Gr of H4350 behind 140 Gr. Bergers.

 

[mikecr]

I think you should stop pulling seating numbers out of your butt and do full seating testing to determine it's best.

 

[Brians356]

I think you should stop pulling seating numbers out of your butt and do full seating testing to determine it's best.

In fact, OP could try Erik Cortina's approach:

http://forum.accurateshooter.com/index.php?topic=3814361.0

 

[JarheadAZ]

I've been shooting the .260 at LR (1000yd F Open) since about 2001.

When I developed my loads, I had one concern only about jump. They should either all jump, or none of them jump. I never did find anything more specific about jump. I never had to, the process works.

Greg

 

[mikecr]

Doesn't sound like a process to me.

 

[loneranger04]

I have two .260s and neither will shoot the Amax as well as 139 Scenar but that's not what this thread is about so...I'd rather find a bullet, which I think the Amax is probably one of, that isn't finicky about seating depth because...if you are trying to seat to lands, or just short of, you'll forever be chasing the lands with a .260. Throat erosion starts after just a few hundred rounds. I have a .260 with a new barrel (Krieger) and after just over a thousand rounds you can really see the erosion and fire cracking already. I'm not a benchrest shooter and can't shoot one hole groups a 100 yards but I doubt you are shooting benchrest matches with 140 Amax bullets anyway. For ringing steel out to 1000 yards plus I'd seat a little deeper than magazine length and tune the load using different powder weights as you have been doing.

 

[JarheadAZ]

Doesn't sound like a process to me.

You're right Mike, I left some stuff out.

I would find my lands with dummy rounds, then seat to an OAL length of .010" shorter to ensure that no ogive variation should result in rifling contact.

In truth, I seldom even do this anymore, since all my chambers are now SAAMI spec, and my rifles are all repeaters. So basically, I typically seat to the max OAL length shown in the Sierra Manual.

Thanks for the prod, I needed it.

My current .260 project is to develop a 200yd load for my Savage 10 Predator Hunter using the 95gr V-Max and Varget. I suspect I'm going to find something useful at or around 41.0gr.

My 1000yd load used right around 43.8gr of H-4350 and the 140 A-Max/142 SMK in an L-W 28" 1:8" barrel.

I'm also in the process of switching brass from necked down Win 7-08 to necked down HDY 7-08. My primers remain CCI BR-2.

Greg Langelius