260 rem loads

D

dsnyder

Inactive
I've been working up loads for 140 gr Hornady Interlocks in my Model Seven 260 Rem, 20" brl. I started at 40.0 grains of H4350 and slowly worked my way up looking for signs of pressure just like you should.
I am well over the max loading that I have seen listed anywhere. I just chronographed 2850fps and the only sign of pressure I see so far is a slight, and I mean slight, cratering on the primer around the firing pin dent. When I compare the primers I'm using, Federal 210 lg rifle, they look exactly the same as the Federal factory loads, except for the slight cratering. I measured the case head diameter and they appear to be about .001 to .003 over a factory loaded, fired case dimension.
The case head has a slight mark on it from the ejector. Again it looks exactly the same as the Federal factory load. Extraction is normal.
I know that all guns are different but could this rifle really be that much different from nearly everything else?
What other signs of pressure should I look for? Could I be missing something?

any advise would be appreciated.
 
I think you are fine and not in danger. Load data for that combo can be difficult to find. BUT I think you have found the upper end of your rifle with that powder.

FWIW, I get to around 43.9 grains before I get that slight cratering on the primers. I am seated about 2.870 with 142 smks. I do not use the load of course, b/c it is a bit too close to my rifle's max. The 43.9g is well above what anyone usually lists. Let the gun tell you. Your velocity seems to be right in line with what people get to with the h4350 pressure signs, but with your shorter barrel length I would think it would be lower.

You have obviously reached pressure limits, so time to back it down a bit. I would try for a bit over 2800 fps. What barrel length are you running?

I would check the primer pockets of the cases you have fired. The rem 260 brass sometimes is soft and and will loosen up on heavier loads.

You could try adjusting seating depth or try a few different primers too.
How is it shooting groupwise and SD?
 
How does it group? A 140 gr. 6.5 bullet of good design at that speed should do anything you need it to do, if it shoots well in your rifle.

I'd be leery of increasing that load if the primers are flat (edges are no longer radiused), beginning to flow around the pin and the extractor is leaving a mark......

I you MUST get MOAR velocity, look into Hodgdon's new Superformance propellants ....... I understand they are quite spendy, but will give 100 to 200 f/sec more velocity than other powders at similar pressures. Beats me how they do it.

http://www.downrange.tv/blog/hodgdon’s-new-hornady-superformance™-and-leverevolution®-powders/6017/
 
Thanks Guys.

To answer your questions the firle has a 20" brl.

I'm loading 47.0 grains of H4350 (this gave me the slight crater on the primer)
*As I said I seem to be WELL above what most people find ot be the max load (as far as grains of powder is concerned)

I don't need any more velocity from this. Haven't shot for groups yet.
 
IMHO

If your head measurements are .001-.004 greater than spec, you are putting your rifle and yourself at risk. The rule of thumb that Ken Waters used in his loading was anything that expanded .0005 was a good working maximum. My own results bear this out. I've only exceeded book max with my 6.5-06 and 140 Hornadys; however, this rifle is long throated for 140 Sierras seated to the shoulder. I get no pressure signs whatsoever.
 
I'm measuring the head at the portion of the case which is just forward of the rebated rim, where the body of the case would be the largest diameter.

Is that the correct place to take a measurement?

I've been loading for 15 years or so but I've never run into something so unexpected. I've always used the primers and the chronograph to give me the inforrmation I need when looking for pressure signs. Am I measuring that the correct point on the case?

My inclination is to back off a full grain (to 46) and shoot a few more rounds to confirm my findings and see how they group.
 
I've always used the primers and the chronograph to give me the inforrmation I need when looking for pressure signs. Am I measuring that the correct point on the case?
Click to expand...

You know you can use the chrony to tell you a bit about what the group will look like, right?

As you increase the load, watch the standard deviation..... it usually starts out pretty large at the "start load" and gets smaller as the charge increases .... up to a point, anyway: then it usually begins to grow again as the "Do Not Exceed" charge is neared...... my best group is usually shot with the charge that gave the lowest SD ..... IME (limited, at that), the SD of slow powders is near max charge.
 
Your measurement place is correct - just in front of the head. Jimbo raises an excellent point about SD and ES. If your load has SD below 10 and and extreme spread below 30fps, then you'll have an accurate load. Looking at Hodgdons Data, 42gr. with a 140 gives 58,000.
 
I looked on Hodgen's website last night and saw that 58,000 also. I'll back off and see what kind of groups I get.

Thanks!
 
FANTASTIC!

Backed off to 46.0 grains, 2800 fps, no pressure signs and got 4 shots into a group .271" this past weekend. I chickened out and didn't fire the 5ht shot...

I'm sticking with this. I don't see any reason to change anything.:D
 
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