110 grain bullet in the 7-30 Waters

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mtngun
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110 grain bullet in the 7-30 Waters

Postby mtngun » Sun Jun 02, 2013 6:53 pm

Since I failed to achieve 2700 fps at safe pressures with a 120 grain bullet, I thought that if I dropped the weight down to 110 grains, 2700 fps would be child's play.

I made two versions of the 110 grain Loverider (pronounced "low-ver-rider"), the one shown here with a single 0.286" driving band, and another that is identical except it doesn't have ANY driving bands, only bore riding bands. Yes, that's a weird design but I like to push the envelope to see what happens.

Most of the bullets were lubed with HVR, but a few of the lubed bullets were rolled in fine brass chips. After being dusted with brass chips, the bullets were run through the push-thru sizer to embed chips in the lube. Then I repeated the dusting and sizing process to be sure the bullet was quite "brassy." :lol:
Image

I walked up powder charges with both WW748 and WW760, using the zero-band bullet. You basically can't stuff enough WW760 in the case to hit 2700 fps. You run out of powder space, pressures go up when you compress the powder, and yet velocity doesn't increase much. :cry: WW748 worked much better ..... but I am nearly out of WW748 !!! :evil: So I'll just file this info for future reference, and in the meantime I'll have to continue to struggle with WW760.
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Zero Band Loverider:
I shot 3-shot groups as I walked the powder charge up.

1.8" -- 43.0 gr. WW760, 2.700" COL, HVR, 2590 fps

7.4" -- 43.5 gr. WW760, 2658 fps

8.2" -- 43.7 gr. WW760, 2668 fps

The zero-band bullet was inaccurate at high speeds so I gave up on it.

One Band Loverider:

3.2" -- 43 gr. WW760, 2.545" COL, 2652 fps, 43 ksi

4.5" -- 43.2 gr. WW760, 45 ksi, chrono not reading due to lighting conditions

One Band Loverider with Brass Chips, 43.2 gr. WW760:

3.3"
2.5"
4.1"
4.4"
4.4"

At 2669 fps, average velocity was higher than HVR, though standard deviation was high too at 0.76%.

I don't have a bore scope, but I inspected the bore near the muzzle in good light after shooting the brass chip bullets. Normally high velocity cast bullets leave a grey "wash" near the muzzle, but the brass chip bullets left it black. To my eye it seemed cleaner than normal.

Was This Project a Failure ?:

After struggling with high velocity cast off and on for 10 years now, I'm right back where I started -- I can't stuff enough powder in the case to hit 2700 fps at safe pressures, and average accuracy seems stuck around 3 MOA.

But I'm learning things with these experiments, and that's the whole point. After all, I have no PRACTICAL use for high velocity cast bullets. It's like climbing Mt. Everest -- you do it because it is there, and because you want to challenge yourself and your equipment. 8-)

Lessons Learned and Things to Try Next Time:
-- cast bullets, particularly "loverider" bullets, may be too slippery to burn "normal" powders well. Contrary to popular belief, a more slippery bullet is usually slower, not faster. "Sticky" bullets like the Barnes X are faster because they create more pressure and make the powder burn more efficiently. I'm going to move in the direction of faster burning powders, but it may take a while due to the component shortage.

-- the brass powder coating indeed acted like a chore boy and left the barrel very clean. However, it didn't improve accuracy. I've said all along that there has been no sign of a serious fouling problem with HVR. A little bit of grey "wash" seems to be harmless as long as velocities and groups don't deteriorate as more shots are fired.

-- The loveriders seem to work OK providing there is one full diameter band near the top of the neck to align the bullet in the case neck.

-- A full diameter front band on a loverider, that kisses the throat, seems to either help, or at least it does not seem to hurt.

-- itty bitty bands seem to work just as well as big Elmer Keith-style bands, though the itty bitty bands may be more difficult to cast.

-- In this particular rifle with it's better-than-average throat, I have seen no advantage to bore riding bullets. Accuracy seems no better or worse than full diameter loverin-style bullets. I suspect the bore riding design may be more likely to have an advantage in a crappy throat.

-- skidding is a non-issue providing the bullet is seated to kiss the rifling.

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mtngun
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Posts: 1638
Joined: Fri Feb 01, 2008 5:45 pm
Location: Where the Salmon joins the Snake

Re: 110 grain bullet in the 7-30 Waters

Postby mtngun » Sun Jun 02, 2013 7:05 pm

Forgot to include the pressure traces. :oops:

This is the zero-band loverider with 43.5 grains WW760, about 2650 fps.
Image

This is the brass-coated one-band loverider with 43.2 grains WW760, about 2670 fps. The brass coating caused more variation in pressures in velocities.
Image


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