Interpreting Pressure Signs from Velocity (260 Remington load dev)

[Pdvdh]

1Moose,
Every legitimate rifle action and barrel is designed to be stronger, much stronger, than the brass cartridge case head. The cartridge case head should always fail under increased pressure levels before the rifle action or barrel experiences structural failure.

The one seldom experienced (but certainly occurs) exception to this would be a bore plugged near the muzzle. Plug the bore tight at that location with mud or another significant blockage, you might bulge the barrel out near the muzzle. But that's a different source of pressure. Even otherwise safe, relatively low pressure loads could still bulge the barrel with a bore obstruction.

So - measuring case web expansion is measuring the weakest link in the mix. No matter the brand of brass, the yield limit property of the brass, or the thickness of the brass. Yes, different brass cases will support differing case pressure before yielding to case web swell. As long as you're monitoring the case web expansion with the brand of brass you choose to use, you'll be identifying problem pressure before it becomes hazardous.

You wanna use cases with strong cartridge case heads, providing longer case life, even while running higher pressure loads producing higher MV? Use Lapua and RWS brass when available for your cartridge. If they're not available, maybe Norma. Some Norma brass is tough, some not so tough. Lapua and RWS is normally good throughout their product lines, in all cartridges.

 

[Pdvdh]

You not only assume far too much, you also talk about your assumptions far too much as well. Perhaps to reinforce to yourself that your assumptions are correct?

Good night sir...

Bye bye... gonna miss you!

 

[desertcj]

Bye bye... gonna miss you!

Lol, maybe you can blow some more primers in your super-uber magnum and then teach us how to measure case head expansion to check for pressure....ha

 

[Pdvdh]

Lol, maybe you can blow some more primers in your super-uber magnum and then teach us how to measure case head expansion to check for pressure....ha

You stating you don't care is as meaningless as your machinist-based comments on proper measurement tools for a task you know, and understand, nothing about.

You can't contain your care, any more than your need to decide on behalf of others whats a proper and safe mode of operation. You really need not be concerned about caring for my well being and lava flow. You might, however, take care of the flow of the other stuff, because you're piling it up pretty deeply.

Bye again, he who cares not. Tee hee. And hah hah to boot. Hip boots would be best in your case. Good night? Over and out? Roger that? Can you hear me now?

 

[Pdvdh]

1Moose,
Be cautious with any desertcj posted information. He'll likely lead you into a squib load, one that leaves the fired bullet stuck in the bore. Remember..., he doesn't like lava or the fire associated with it.

 

[1Moose]

1Moose I will offer this along with above. The Nosler data indicates max of H1000 at 50 grains with Nosler brass the hornady data indicates a max of 49.6 with remington brass. Remington brass weight averages 161 grains per case. The nosler brass I have weights 166 grains per case. Lapua brass weights 173 grains per case.

All this can explain some of your velocity issues heavier brass can translate to lower case capacity and greater pressure during firing hence greater velocity. The best way to check is to prime a case and fill with water and measure it to see the difference in actual capacity.

The nosler data indicates 50 grains max and 2785 fps. You may have an anomaly with the chronograph or a faster barrel.

In any case as explained above I don't think you can fit enough H1000 in a case to go over pressure it's rather unique in that way.

How is your accuracy at 47.8 gr you have an extreme spread of 10 fps and there is nothing wrong with that. Measure a few cases before firing and after firing above the case head and see how much expansion your are getting. This will be a better indicator than looking for pressure signs.

Noslers minimum data is 46 gr for 2596 and 48 gr for 2686 and above. Your load is about 70 fps over Nosler. I would increase as you have and see if ES improves. In all probability you will be able to increase until you get case deformation from powder compression this will generally happen at the shoulder but you can measure for this as well.

I hope this helps.

Good luck and shoot straight

Bob

1Moose I will offer this along with above. The Nosler data indicates max of H1000 at 50 grains with Nosler brass the hornady data indicates a max of 49.6 with remington brass. Remington brass weight averages 161 grains per case. The nosler brass I have weights 166 grains per case. Lapua brass weights 173 grains per case.

All this can explain some of your velocity issues heavier brass can translate to lower case capacity and greater pressure during firing hence greater velocity. The best way to check is to prime a case and fill with water and measure it to see the difference in actual capacity.

The nosler data indicates 50 grains max and 2785 fps. You may have an anomaly with the chronograph or a faster barrel.

In any case as explained above I don't think you can fit enough H1000 in a case to go over pressure it's rather unique in that way.

How is your accuracy at 47.8 gr you have an extreme spread of 10 fps and there is nothing wrong with that. Measure a few cases before firing and after firing above the case head and see how much expansion your are getting. This will be a better indicator than looking for pressure signs.

Noslers minimum data is 46 gr for 2596 and 48 gr for 2686 and above. Your load is about 70 fps over Nosler. I would increase as you have and see if ES improves. In all probability you will be able to increase until you get case deformation from powder compression this will generally happen at the shoulder but you can measure for this as well.

I hope this helps.

Good luck and shoot straight

Bob

No problem. I have been shooting and reloading for the 260 rem since about 2000. I really like the cartridge I've owned as many as 4 rifles chambered for it and 3 right now.

In that time for 140's I keep going back to H4831SC. H4350 is excellent for light bullets 120's RL15 or I4064 with 100's. I've tried a host of powders and have 100's of targets.

Stick with Remington 9.5's and Lapua brass IME it does not get better. 7828SSC shows promise as well.

If you're getting good accuracy and by good accuracy 1/2" 3 shots are common what you're running is pretty darn good.

Good luck and shoot straight

Bob

I got to my notes regarding performance with the different seating depths at 47.8 grains H1000 with the 143 ELD-X. There was some wind (5-20 mph varying from headwind to 30%). Regardless, I'm not really liking what I saw for accuracy (200 yards):

• .010 Jump (n=5 shots): Max spread = 3.1 inches; Vert spread = 1.2 inches. Velocity average = 2764. Std Dev = 9.1 fps.
• .028 Jump (n=5 shots): Max spread = 2.2 inches; Vert spread = 2.1 inches; Velocity average = 2759. Std Deviation = 25.8 fps. First shots of day out of perfectly clean bore.
• .033 Jump (n=4 shots): Max spread = 1.32 inches; Vert spread = 0.85 inches. Velocity average = 2754. Std Deviation = 12.7 fps.

On the earlier outing with 47.8 grains H1000, but at 100 yards:

• .028 jump (n=4 shots): Max spread = 0.6 inches; Vert spread = 0.44; Velocity average = 2677; Std Deviation = 10.2 fps.

I'll keep searching for something better (and try one of these loads on a calm day). I have a bunch of cartridges loaded in the basement waiting for their day: 143 ELD-x (with H4831) and Berger 140 VLDH (with IMR 4350--loaded these just before I received my H4350). I hope I see some magic somewhere in there! <wish I had H4350 load data for the 143 ELD-x to try that>

 

[scottishkat]

1Moose I would expect excellent accuracy with 140/142 at + or- 44gr H4831SC maximum of 45 or 46gr. With H4350 I would start at 41gr and expect maximum at 43 or 44gr all this with my rifles.

I had promising accuracy with the 140 VLDH and RL19 never got around to trying H4831 with it as the 140 NAB has been stellar. I4350 is an acceptable choice but I have found it less accurate than H4350, H4831 and I4831.

I tried H100V with light bullets and accuracy was very good. I have not gone back to it as H4831 and H4350 are members of Hogdons extreme powders and have a great reputation for temperature stability. As I recall it is a blend of H4350 and 4831 so it should be a real good choice.

I would not worry about the 8.5 twist rate it will probably stabilize anything you would care to shoot with a 260 Rem. The only bullet I have tried and could not stabilize in a 1 in 9 twist is the 127LRX it actually keyholed at 100. The 1 in 8 twist in my Sako is pretty sweet though.

Don't forget to post results.

Good luck and shoot straight

Bob

 

[1Moose]

1Moose I would expect excellent accuracy with 140/142 at + or- 44gr H4831SC maximum of 45 or 46gr. With H4350 I would start at 41gr and expect maximum at 43 or 44gr all this with my rifles.

I had promising accuracy with the 140 VLDH and RL19 never got around to trying H4831 with it as the 140 NAB has been stellar. I4350 is an acceptable choice but I have found it less accurate than H4350, H4831 and I4831.

I tried H100V with light bullets and accuracy was very good. I have not gone back to it as H4831 and H4350 are members of Hogdons extreme powders and have a great reputation for temperature stability. As I recall it is a blend of H4350 and 4831 so it should be a real good choice.

I would not worry about the 8.5 twist rate it will probably stabilize anything you would care to shoot with a 260 Rem. The only bullet I have tried and could not stabilize in a 1 in 9 twist is the 127LRX it actually keyholed at 100. The 1 in 8 twist in my Sako is pretty sweet though.

Don't forget to post results.

Good luck and shoot straight

Bob

I managed to get out today and started to see some results I think I can build from--all shooting at 200 yards from a bench, using bipod and a rear bag. I was shooting Berger 140 VLDH w/ IMR4350, and Hornady 143 ELD-X w/ H4831. Lapua Brass and Rem 9.5 primers.

Berger 140 VLDH w/ IMR4350 (all shots 200 yards)

• 37 grains, .010 jump
  • 3 shot group: Spread = 1.2
  • Vel avg = 2514, ES = 12, Std Dev = 6.5
• 38 grains, .010 jump
  • 3 shot group: Spread = .90
    
  • 3 shot group: Spread = .91
  • Vel avg all 6 shots = 2567, ES = 28, Std Dev = 14
• 38 grains, .050 jump
  • 3 shot group: Spread = 1.47
  • 3 shot group: Spread = .64
  • Vel avg all 6 shots = 2556, ES = 19, Std Dev = 8
• 38 grains, .090 jump
  • 3 shot group: Spread = 1.36
  • 3 shot group: Spread = .86
  • Vel avg all 6 shots = 2519, ES = 34, Std Dev = 12
• 38 grains, .130 jump
  • 3 shot group: Spread = 2.2
  • 3 shot group: Spread = 1.4
  • Vel avg all 6 shots = 2515, ES = 26, Std Dev = 12
• 39 grains, .010 jump
  • 5 shot group. Spread = .87 <shot all on same target accidentally; I clear flier 3/4 inch away>
  • Vel avg all 6 shots = 2618, ES = 18, Std Dev = 7
• 39.5 grains, .010 jump
  • 3 shot group. Spread = .97
  • Vel avg = 2646, ES = 10, Std Dev = 5
• 40.0 grains, .010 jump
  • 3 shot group. Spread = .85
  • Vel avg = 2682, ES = 35, Std Dev = 18

Hornady 143 ELD-X w/ H4831 (all shots 200 yards)
All 4 shot groups with 42.5 grains H4831. Varied seating depth. Velocity of all in range of 2600 to 2642 fps (faster being cartridges with less bullet jump)

• .010 jump: Spread = 1.14
• .030 jump: Spread = 1.8
• .060 jump: Spread = 2.4
• .080 jump: Spread = 1.9
• .100 jump: Spread = 1.2 <3 shots bunched at .6 inches>
• .120 jump: Spread = .94 <3 shots bunched at .54 inches>
• Next step will be to try varying the powder charge, which I may do with the SC so things aren't so compressed.

Probably more data that you were interested in, but there are some encouraging signs. Thanks for the prior load tips. I look forward to trying some of them in the future now that I have my brass back (which is what I was really planning with cartridges I loaded with the the IMR4350 rounds now that I have H4350, but they looked promising...)

Thanks again.

 

[1Moose]

Hello all,

Working up loads for 260 Remington. 24 inch Chanlynn barrel. Would appreciate any help interpreting if velocity for loads show any concerning pressure signs. First, no cases had any visible signs of pressure. Only the very slightest flattening on just a few primers across all loads, and not corresponding to the highest powder charge (still plenty of roundness to the edges). Not even the faintest extractor marks. No hint of stiff extraction.

Components: Lapua brass. H1000 powder. Rem 9.5 primers. Hornady 143 ELD-X bullets.
Labradar chronograph.

DECEMBER 26 (70*F). These are shots 40 thru 80 (roughly) in new barrel / rifle.
Load 1: 45.6 grains H1000. Jump = 0.050. Velocity avg = 2574.
Load 2: 46.1 grains H1000. Jump = 0.050. Velocity avg = 2596.
Load 4: 47.0 grains H1000. Jump = 0.047. Velocity avg = 2664.
Load 5: 47.8 grains H1000. Jump = 0.028. Velocity avg = 2677.

Load 6: 46.1 grains H1000. Jump = 0.156. Velocity avg = 2609.

JANUARY 20 (42*F). Tried three seating depths based off of 47.8 grains as that had tightest group earlier)
Load 7: 47.8 grains H1000. Jump = 0.010. Velocity avg = 2764.
Load 8: 47.8 grains H1000. Jump = 0.028. Velocity avg = 2759.
Load 9: 47.8 grains H1000. Jump = 0.033. Velocity avg = 2754.

Questions:
Q1) I've heard of velocity increases in first 150 rounds of barrel. First time I've had a chronograph to observe it myself. Even with lower temperatures in second outting, Load 8 is 82 fps higher than Load 5. <same load, a few more rounds down barrel, lower temp). Seem normal?

Q2) In Loads 7-9, I'm seeing approximately 150 fps higher than the Hornady manual's listed velocity. Again, no pressure signs. Maybe I have a faster than normal barrel? Have heard of +/- 100 fps not being uncommon. Granted, Hornady doesn't give many increments for powder and velocity for the 260 Remington, so I may not actually be that much higher than book if they showed more detail. (They show a lot more detail for Creedmoor for far more powders--likely given their affinity for their own cartridge). And I'm closer to lands and have longer overall cartridge length (2.820 vs 2.800) so less gas is escaping around the bullet I assume before it engages rifling.

Q3) Load 5 didn't show much velocity increase from Load 4, despite the powder increase. Should I assume this is a concerning sign? Max book load is 49.6 grains H1000 @ 2700 fps listed. Note that some load groups only recorded velocity for 2 shots given chrono position, so sample size isn't large.

Any thoughts could be useful as I haven't had benefit of chronometer for load development, so learning how to interpret things.

Thanks everyone for the thoughts / help. I'm trying to learn, and one of the things that is great about this forum is how generous everyone has been with their time. I really appreciate it, from all of you.

I had formulated some thoughts in my mind earlier in the day, and I'll hazard to post them--recognizing fully that I know less about this than everyone else commenting on this thread.

I had run into that info on Hodgdon site in my search for info on how much web expansion was too much. Thanks for referring me back to that. What I'm thinking now on both measurement and hardness:

Measurement:
If 260 Remington is somewhere in the .0005 - .0006 range for acceptable 1st-firing web expansion, then the chance of missing signs I was in that range with my current calipers would likely be small if I averaged out several cases (some "rounding" down to NN.nnn0 or NN.nnn5 and some rounding up). With a single case, logic would suggest it'd be pretty easy to get compounding errors pre- and post-firing that would underestimate case head expansion (and equally likely to overestimate case head expansion). Averaging several should help eliminate that.

Hardness:
The wrench in all of this seems to be that if some cases are made of brass with nearly double the hardness of others--and may even place more of it in the web area--then using the same criteria of maximum expected expansion for different manufacturers may have highly different factors of safety built in (i.e., cause very different interpretations on where one is starting to get into that range of pressures). One would guess (correctly?) they set those expansion guidelines with the "weakest" brass?

With all of the above, I can see why some reloaders, 1) load up until they see other pressure signs and then back off, or 2) use factory rounds with the same brass (in my case likely expensive factory rounds with Lapua brass) as a baseline.

Honestly, I'd like my brass to last a while, but I really just don't want to lose an eye or something. I'm okay if I only get 8 instead of 15 loadings out of it. One factor in my mind is that because I have a 1:8.5 twist, I want to ensure I have enough velocity to maintain stability in the 140-143 grain bullets out to maybe 700 yards. Fortunately, I live at 5000' so that helps there. I am a bit frustrated with myself that I didn't get an 8-twist when I had this rifle made. I need to let that go as that's not worth the stress I feel when I overthink that!

I tested the case head expansion today with 4 cartridges loaded to the same spec that originally started my wondering about potential overpressure given the velocity I was seeing (though no visible signs of pressure from extractor or on primer).

• Hornady 143 ELD-x
• H1000 47.8 grains
• Rem 9.5 primers
• Lapua brass (unfired, ran though FL die and chamfered the inside and outside of the neck)

I marked all four cases with sharpee, and marked my calipers as well so I was sure to measure in same place every time. Pre-firing case head measurement was 0.469 inches on all 4 cartridges. Post-firing case head measurement was 0.4695 (also on all 4 cartridges). I was as meticulous as I could be to get the calipers aligned in the exact same spot. So, measured expansion is .0005. Velocity from these four cases averaged 2772 fps, which as a bit higher than this load on my last outing when they averaged 2754 fps. I wanted to be sure to test the expansion and post the results given all the help offered in response to my original post. Thanks!

 

[Pdvdh]

Interesting read following your progress. Look's like you're getting there and having some fun along the way.

 

[1Moose]

Managed to do some more testing with the 260 Remington with both Berger 140 VLDH and Hornady 143 ELD-X. Results continue to improve.

All groups at 200 yards. A bit of crosswind, but not bad (0-5 mph from 30 degrees, mostly predictable as it would steadily increase /decrease)

140 VLDH; H4350 41.1 grains H4831SC; Rem 9.5 primers; .010 jump

• 3-shot group: Spread = .57 inches (vertical = .52)
• 3-shot group: Spread = 1.43 (vertical = .28). One shot well left.
• Superimposing 2 groups and a 5-shot spread = .57 inches (vertical = .52). The shot off to left could've been any combo of me, wind, and load.
• Velocity = 2775; SD = 9.8
• This was max load, so I measured pre- and post-firing case head and saw expansion of .00075 over 6 cases--3 showed .001 expansion and other 3 were .0005). No visible pressure signs.

140 VLDH with 40.8 grains; Rem 9.5 primers; .010 jump

• 3-shot group: Spread = .73 inches (vertical = .54)
• 3-shot group: Spread = 1.02 inches (vertical = .14)
• Superimposing 2 groups = 1.02 inches total spread, with 5 shots grouped under .7--and one off left again)
• Velocity = 2748; SD = 7.1

140 VLDH with 40.5 grains H4831SC

• 3-shot groups had spread of .87 inches and .83 inches (vertical spreads of .45 and .34)
• Velocity = 2734; SD = 12.2

The 143 ELD-X with H4831SC showed 3-4 shot groups from 0.47 to 1.98 inches. A couple of possible good loads to tweak to see if they'd do well consistently. I have those loaded for my next time out.

Thx again for the prior help.