accuracy hard vs. soft bullets

[rp85]

good afternoon;

Caliber is 375 Wby. This rifle gave great accuracy, @1” or less, with cast bullet hardness of BHN 25. Cast bullets now have a BHN number of 11-12. Using same powder charge that gave great accuracy, my groups went to 3”+. Speeds are 1400 & 1650 with two different powders. The only variable are bullets that are not as hard compared to what I was shooting. bullet is a 375449 clone, gas checked.

Normal to loose accuracy with softer cast bullets? Thx for any input

rp

[quilbilly]

That has not be proven for me but every barrel has a personality of its own. If you are getting that accuracy with the hard boolits then as the saying goes, "If it ain't broke, don't fix it." Boolits that hard may have other issues in terminal performance, however, so if you are hunting with that rifle, you might try an intermediate BHN for an accuracy trade-off that is acceptable to your hunting conditions.

[Winger Ed.]

I wouldn't think it would make any difference.
The main issue should be leading, or conserving expensive additives to the alloy.
But often it does.

If you've found what the rifle likes-- I'd stick with it.
Without getting off into some real tweaking, and custom barrels, etc,
I'd think getting 1" groups is perfectly acceptable.

[Wheelguns 1961]

Perhaps the harder bullets are doing a better job of engaging the rifling.

[243winxb]

Hard bullets dont skid or slump on firing.

[waksupi]

Rule of thumb, Brinnell two points higher than velocity. Example, 1200 fps, 14 Bn, 1400 fps, 16 Bn, etc.

[BLAHUT]

Rule of thumb, Brinnell two points higher than velocity. Example, 1200 fps, 14 Bn, 1400 fps, 16 Bn, etc.

Each gun has its own likes and dislikes? I found my roler likes pure lead bullets at about 1200 fps or a tad less with no leading and very accurate out beyond 1000 yds, with my lube and the way I build my loads. I found the lube to be a very big factor in the load, I tried every kind available to me on the market, none did what I wanted, took a long time of trial and error, to find what would work for my load and for me. Just my opinion. Just what I found to work for me, only took about 5 years of trial and error. Works in all my 45 and 50 cal. guns.

[charlie b]

I have used Lyman #2 for years now in the .308. Works well for me even with long bore riders up to 2000fps.

I would have guessed that harder bullets would be less accurate at those velocities. So, unless you are getting leading in the barrel I am out of ideas.

Forgot to ask. Gas checks or plain base? I use GC on all my rifle loads that are over 1200fps.

[Bigslug]

Rule of thumb, Brinnell two points higher than velocity. Example, 1200 fps, 14 Bn, 1400 fps, 16 Bn, etc.

Though it seems a bit of a simplified generalization, this is probably a pretty fair place to start. I have found some sign of it myself. As velocities start to creep up, both 20-1 (expands wonderfully) and air-cooled wheelweight simply give up the accuracy ghost, and 1300-1400fps seems to be roughly the place that starts to happen.

The causes for this may be legion, but the Mann brothers in A Bullet's Flight spoke of testing done by progressively shortening barrels, which had the effect of increasing the gas pressure on the unsupported base of the bullet at the point it exited the barrel. The effect of this was deformation of the base - especially with softer slugs. This MAY be one of the reasons for our soft bullet accuracy disappearing as loads get hotter.

[Larry Gibson]

Additionally to skid and set back with a lubed bullet the swaging down of the bullet as it rides over that layer of lube is greater with the softer alloy. It may also be greater intitially with faster burning powder giving a quicker acceleration rate.

[Outpost75]

I'm with Larry. Over simplified.

Bullet fit is more important than hardness.

In black powder calibers with either BP or smokeless loads I get fine results with 1 to 30 tin-lead up to 1400 fps. With GC bullets I am OK With 50-50 wheelweights and plumber's lead with 1% tin added to 1800 fps. I use 50-50 linotype and plumber's lead to 2100 fps to function M1 Garand.

[35 Rem]

I'd guess it has something to do with the freebore in a Weatherby rifle. I've played around with the Lee 500 grain in my 460 but not got any great results as of yet. I tried a NOE that weighs I think 395 grains and it didn't impress at all. My 1st inclination was that the freebore makes these rifles unlikely to ever shoot any cast bullet well unless it is heavy for caliber so that it can span the freebore and get closer to the rifling. I could be wrong but that is my conclusion with the limited testing I've done. I strayed from the 460 due to other more pleasant cast bullet projects so my conclusions may prove to be wrong someday when I get back to it.

[mehavey]

OP didn't mention powder or bullet as-sized diameter, or lube/ALOX/PC

FWIW: at 1,400/1,600 fps, nothing harder than Lym#2 is warranted -- properly sized/not-too-slow of a powder/
Kick size up to 0.002" over groove/fast powder

BN 11/12:
- ALOX'd good for 20,000 psi
- PC'd good for 30,000 psi
FAST powder to get bumped up in the freebore

Try it w/ a half-dozen to see if improvement looks in the cards.

[dondiego]

Had you fired any jacketed bullets in between tests and maybe left a little copper fouling in the bore?

[rp85]

Good morning;

Though it would be nice to hunt with rifle. BHN number was 25, to hard to expand. Had large pot of alloy that was hard which took a fair amount of lead to reduce BHN to 11-12 per pencil test. Great accuracy went away.

New update on hardness. Cast a very small batch of bullets and water quenched. BHN went to 18-20 per pencil test.

Shot yesterday with new hard bullets, accuracy returned. Soft bullet groups that were 3+ inches (5 shot groups), with new hard bullets ( 3 – 3 shot) groups averaged .95” (35 grains 3031\ 1650 fps\oal of bullet 3.225”).

Just to see what would happen if I reduced speed using Red Dot powder. Shot soft bullets that were hollowed point using a Forster tool + a counter sink bit to increase diameter of hollow point, 14.4 grain Red Dot\1350 fps\oal 3.225\ groups avg . 890”. Accuracy also returned.

Answers to questions. Bought rifle to shoot only cast bullets.

Rifle had no free bore, custom rifle, original owner passed away years ago. Had to use reamer to get some free bore to close bolt on cast bullets.

Using an Arsenal mold, 375449 clone, sized to .379, weight is 285 grains lubed and gas checked. Now using this cast bullet for everything.

Brother of original owner shot rifle 1 time put it up for 30+ years, but said “if you shoot rifle with Wby ammo it will hurt you”.

Thx for input.

rp