working up load for a 260

hey guys, I am working a load up for a gun I built Its a 260 with a 26 inch shilen varmint barrel. I have new lapua brass, 139 grain lapua scenar bullets and h4350 powder. I have figured my oal using a hornady oal guage and bullet comparator. I am getting 2.285. Now Ive read that I need to work with seating depths before figuring powder charge. So I am going to load 3 at 2.285, 3 more at 2.28, 3 more at 2.275 and 3 at 2.27. I know I need to start with a powder charge on the low end so i am looking at 41 grains of h4350 to load in all the cartridges to start with to find the best seating depth and then work up powder charge. Would you guys please tell me if i am on the right track. Thanks.

Sounds like you are on the right track... My max load for my 260 Rem Match (CBI barrel) is 43 grains H4350 pushing the 143 ELD-X. I get 2745 FPS out of 25" barrel at 59 degrees. my seating depth is a bit longer because of my Match chamber. I'm guessing you 2.2 measurement is to the ogive? My COAL is 2.933 for my match chamber, but normal specs for 260 rem are 2.80 COAL.

Do you mean 2.825" instead of 2.285"? (Or is your .260 not a .260 Rem?) You're WAY down into the case if your measurements are typed correctly. 2.800" is the SAAMI C.O.A.L.

Yes the 2.285 is measuring to the ogive. my c.o.a.l. is 2.825. Do those sound about right?

That sounds about right... Depending on how that ogive is shaped. There is another way to "old school it" take a fired case, stick it on your resizing die and just barely size the first part of the neck (So the bullet will slide, but also be held fairly well). Slide your bullet of choice in just enough to stay in the cartridge. Carefully push the bullet and the cartridge into your chamber and close the bolt. open the bolt and pull out the cartridge and measure (to the ogive or COAL, which ever you prefer). Do that process 2 or 3 times to make sure the measurement you get is consistent. That measurement should be "to the lands"... Subtract .02 to .04 and that is where I would start with your Seating depths...

Good luck,

Yes.

I have no good way to take that measurement and it changes with any choice of bullet (and where Shilen set the throat on your barrel) so I use the ancient empirical method of setting the bullet long in a powderless "dummy" sized cartridge with the bullet coated in candle soot until it just contacts the lands (all around) and the tighten the seating plug down another 0.010"

Am I on the right track about loading 3 at coal then backing off 5, 10 and 15 thousandths or should I jump in shorter measurements or maybe go out farther than 15 thousandths say to maybe 20 and 25 also?

I move seating depths in .02 increments... Both up and down. So if you have some loaded a 2.80 (for example) the move to 2.82 going up, and then 2.78 going down (this is just an example) but you get the idea I'm sure....

sounds good appreciate all the help gentlemen!

if your .260 is anything like mine it will shoot just about anything. It's a Savage FT/R with a Criterion 26 inch bull barrel .260 1 in 8 twist. I get sub MOA out to 800 using a variety of loads. Nosler 140 CC's with 44.0 gr H4831 with the ogive .05 off the lands is it's favorite. That same load also works with 140 SMK's but you can seat farther back with the SMK. Those same SMK's will also shoot almost as well using H4350 or Varget. 123 grain SMK's work pretty good as well. 107 SMK's were the only bullet I could not get to shoot well. Those loads are just in my gun etc. Please start low with the manufacturers recommendations and work your way up.

The only "issue" I have is trying to determine optimum seating depth before finding optimum load. I normally search for a load with the bullet seating just off the lands, find my load, then mess around a bit with seating depth.

Comments?????

have been reading a lot and a lot of what I read says to find optimum seating depth first and then fine tune with your powder charge. Have loaded some and shot the 123 grain lapua scenars but that was with Remington cases and h4350. Can get moa accuracy with these but never really played with seating depth any. Where I am at I have a place where I can get out to 600 yards and have shot the 123 grain scenars with pretty good results. Just wanting to really play with gun and see what kind of accuracy I could really get. Have a forster ultra micrometer die coming next week and plan on really trying to dial gun in!

Just my method but I have always do the load tests first with bullets seated to manufacturer recommended COL across a chrono looking for loads that shoot with low ES and SD of velocity preferably one that shoots flat velocity for a couple of adjoined tenths. Once I fine the tune the powder load I tweak in base to ogive distance. My reasoning is that if I have a load that is acceptable tweaking the BTO is just putting icing the cake. It may or may not be the most optimum method but it works ok for me

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Originally Posted by rakatak

Am I on the right track about loading 3 at coal then backing off 5, 10 and 15 thousandths or should I jump in shorter measurements or maybe go out farther than 15 thousandths say to maybe 20 and 25 also?

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Just be aware that when you reach that point where the bullet finally is in contact with the rifling before you fire the pressure makes a hockey-stick jump up. Keep an eye out for excessive pressure as well as group size.

That's why I like the soot method. I can "back" a bit off that (two cereal box cardboard thicknesses = 0.020" or close) and then know the bullet is still jumping a bit and tweek from there.

I will also note that some rifles I have owned never showed much preference below the c.o.a.l. and the point where I ran out of receiver cut/magazine clearance. Production barrels seem to keep the throat "generous". Nothing more embarrassing than finding you can't cycle a live cartridge to unload even though they fit the magazine and feed OK. ;-)