Wanting lower pressure but maintian velocity

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Hardened Steel

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Looking for any susggestions,

Looking to lower pressure but maintain current velocity, situation slight ejector scrub on cartridge face, flattened primers but no cratering, This is my current load @ 2900 fps, 260 Remington with 140 matchkings, 41.5 grains VV550 GMM 210 primers, .010 into the rifling.

Thanks
 
Hardened Steel said:
Looking for any susggestions,

Looking to lower pressure but maintain current velocity, situation slight ejector scrub on cartridge face, flattened primers but no cratering, This is my current load @ 2900 fps, 260 Remington with 140 matchkings, 41.5 grains VV550 GMM 210 primers, .010 into the rifling.

Thanks
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I am assuming you meant off the rifling, otherwise that would be your problem right there.

As for your load, you are probably right around max at 2900 for your rifle. Are you neck sizing or full length sizing? If full length, then there is often some movement of you case back against the bolt face that will show on the head. As long as those loads were worked up when it was warm out, I wouldn't worry about it.
 
You could try a bullet with less bearing surface, I think the Sierra 142's have a shorter shank, as do the Berger VLDs. Coating the bullets with moly or WS2, seating the bullets back a touch to let them get a bit of a run at the rifling. I doubt that you could get enough of a slower powder into the case to keep your velocity up.
 
I've tried jumping into the rifiling and jammed into the rifling, both the same results, tried 139 lapua's, 142 MK's, I suspect that I'm at the Max load for VV550, These are neck sized cases. Just wondering which way to with powder, as far as burn rate is concerned, Tried Varget, not enough velocity, tried H4350, too inconsistant in velocity. Was thinking towards H4831sc or even to the extreme H1000.

Thanks
 
You have observed the same thing that I am always saying, same pressure whether the bullet hits the lands, or has a clearance. They tell us the reason for this is that peak pressure is reached after the bullet is well into the barrel, so a minor spike at the start doesn't mean anything.
If there is no sign of your bolt sticking and the primer pocket is not enlarging from your shooting, I sure wouldn't worry about having too much pressure. Most loads shoot best and the powder burns best, at the pressure they are designed for.
 
You have observed the same thing that I am always saying, same pressure whether the bullet hits the lands, or has a clearance. They tell us the reason for this is that peak pressure is reached after the bullet is well into the barrel, so a minor spike at the start doesn't mean anything.
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Take a look at the link below.The 6PPC data halfway down the page disproves your theory.

http://www.shootingsoftware.com/pressure.htm

From that 6PPC data:

Here's a classic good load for 6PPC. The only difference between all these traces is the first 3 were seated right on the lands. The last 4 were 30 thousands of an inch off the lands. Note the substantially reduced pressure and overall reduction in energy.
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re 260 load

You might try VV n 560, I have had good luck with it in my 260 rem 700 lss mountain rifle and have tried all the usual suspects, rl 22. 19 h-4831 h-4350 ect. they were either too slow or the load was too hot( h-4350) The vv n 560 load gave the best velocity and also the best acuarcy with speed. these loads were tried with Nosler 140 partition. my rifle has a 22 inch barrel, unless you shooting a 24 or 26 inch barrel I think you are asking about 100 fps to much for the little 260. All my loads were shot over a chrono were yours?
 
You should try a slower burning powder to achieve lower pressure at similar velocities. Dense slow burner would probably work best. I would give H4831SC and Norma MRP a try. Regards, Eagleye.
 
Wouldnt moly'ing the bullets benefit this situation? What advantage does 10 thou interference into the lands offer over just touching, or a small jump? BTW - I'm with Stubblejumper on the issue of pressure vs proximity to lands...
 
I'm twisting these out of 30" McLennen barrel.
At 2900 and .010" into the rifling this barrel is by far shooting it's best groups, keep in mind this load is being worked up at 3200+ feet above sea level and at below 0' degrees c. I would like to find something that when the temperature rises well above 0'c. the load won't be too hot.
 
Sierra's generally liked to be jumped so moving them back .020-.060 off the lands will decrease your pressure somewhat.

I have used H4831SC, H4350 and RL17 in my .260

I found H4350 to be a bit fast and would give me ejector marks and even pop the primer pockets wide open rendering a few of my cases useless.

H4831SC gives me best accuracy but velocity is around 2850 with a full load but no pressure signs.

RL17 gave me up over 3000fps but the accuracy was not there for me. RL17 will give you good velocity with lower pressure.

I personally do not know where the VV powder you are sits in relation to the others I have listed as far as burn rate but I am sure you can search out a burn rate chart and see if the RL17 will be what you need.
 
You can't do it. The load you have is pretty much at the max of what the cartridge is capable of (BTW sounds like a nice load).

If there were some slack, you could do what you want; if you were getting (say) 2700fps but hitting pressure limits, you could go to a slower powder, get a lower peak pressure, and still hold your velocity.

If your load shoots well though, just keep it. Come summer, it may well be too hot (VV500 series powders are fairly temp sensitive), but if you back off your charge so as to maintain 2900fps in summer temps, your pressure (and accuracy) should be along the lines of what you are getting now. You can do this "summertime load development" in the winter by heat-soaking your ammo; take it to the range in an insulated cooler box, with one or more 2L pop bottles filled with very hot water. Ideally you'd get your ammo to 100F or 120F (whatever your best guess of what your summertime ammo would be), and then chamber and shoot it without delay.
 
That load sure sounds like over max.

the power looks to be one or two notches too fast. Is there room for more powder?

An ejector scuff mark is cause by extruding the solid brass web of the case into the ejector hole. That takes 70,000+ psi.

I know that is a common pressure for our ammo, but be aware you are at a limit - in cold weather.

You are trying to get 260 Ackley velocity out of a regular 260. The case may not have the capacity for more of a slower powder. I get 2950 fps with that bullet using RL22 or 4831SC in an Ackley case..
 
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2900 fps with 140 grain bullets is pretty fast for a .260, or even 6.5x55 in a modern rifle. I think it would be wise to drop your charge slightly if you're getting ejector scuff marks. Anything you shoot won't know the velocity difference.
 
tjhaile said:
2900 fps with 140 grain bullets is pretty fast for a .260, or even 6.5x55 in a modern rifle. I think it would be wise to drop your charge slightly if you're getting ejector scuff marks. Anything you shoot won't know the velocity difference.
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With a 30" barrel my guess would be that this is a Target rig and not a hunting rig.

We target shooters like to get the most wind bucking we can out of our rigs with our chosen calibers (at least I do).

Try RL17, I think it will give you the performance you are looking for.
 
This is a full blowen target rig, tight neck chamber, .002" clearance neck, fireformed Norma 308 brass, full preped, currently using 139 lapua's with the same results, case head expansion is not present. Come Spring when it warms up, I'm aware that I will have to back the load down a bit, I'm just looking to find another powder that will match this load. A powder that is a little more available and priced right. Tried the old faithful Varget not enough velocity, H4350 doesn't group tight enough, VV500 groups excellent at 600 yrds. in heavy winds, the velocity is right where I need it for 1000 and beyond.My load of 550 is not at the body to shoulder junction, I still have room for 3-4 more grains, This is the base of the question and my thinking, is that H4831sc and H1000, both are fine grained type of powders similar to VV550, both are slower burning then 550. N160 and VV560 are options but availablity becomes the problem. I guess I should have been more clear in my original question, has anybody tested these powders in 260 and it's variant's?
 
I have used H1000 and 4831SC in a 260 Ackley.

H1000 is too slow and bulky to fit the your standard case. 4831SC might work. I can send you as sample, if you like.

If I went into my bunker, looking for a powder for your case, I think I would look at N560 or N160. N160 is similar to IMR4350, but better quality. Maybe a ball powder like H414 or WW760.
 
I'm a hunter not a target guy so I may be off base but doesn't hy-brid 100 look like a good fit for this load? It' s burn rate is between h4350 and h4831 sc , so powder space should not be an issue, in alot of loads it develops more fps with less psi than comparable powders. I use it exclusively in my .243 with etheir 100 gr seirra's or 100 gr parts. but these are hunting loads/bullets. May be 2slow for you ... 42gr hb-100 (compressed) 142gr seirra hpbt 2700 fps (24" barrell)
 
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