Big bore load development process

[CoElkHunter]

Well, I do have a lead sled, but it won’t be enough for 500gr loads!

i think I will just confirm max pressure and keep building my ability to handle it!

I use a Past brand harness style recoil pad when shooting my .458 WM from the bench along with a slip on Limbsaver recoil pad ( I need the extra lop anyway). I use just the Limbsaver when standing. Haven’t shot from sticks yet, but with my leather military style sling, I get a great three point stabilized position when using the sling while standing shooting at 50 meters with open sights. I know the WM isn’t a Lott, but haven’t shot one yet, so this is just FYI?

 

[bruce moulds]

I sort of followed the method talked in this video, which is OCW-ish, with the first pass of developing my 404 Jeff loads. Full disclosure, I had a favorite load that was given to me, so we had a certain load in mind when we started. But as pointed out in this video, and what I did, was loaded a total 10 rounds of 5 loads and shoot them into a dirt bank and simply chrony the shots. I used a friends magneto type chrony. We had 2 rounds of each load and 5 loads to test. Since Swift A-Frames aren't cheap, this was an economical test. We simply looked for the for the SD and ES from two shots on each and found the node.

s.d is absolutely meaningless for 2 shots.
10 shots is becoming a meaningful min.
standard deviation is a statistical measure.
it is however, done properly far more meaningful than extreme spread, as it measures all the shots, as opposed to only 2.
both things are really pointless for a big bore rifle.
also, low e.s. does not necessarily indicate tight grouping, other than reducing vertical at ranges over 600 yds
even then, are you tuned to positive or negative compensation?
for a big bore, just get a velocity close to what you want and make sure it will group well enough for the job.
you won't exactly be shooting it off a benchrest and at long range, more likely offhand.
ability to deliver acceptable accuracy from positions shot, and what is delivered to the target are the priorities here.
bruce.

 

[nksmfamjp]

Yea, I feel like I’m more developing to the max load the shooter with a confirmation of accuracy. Accuracy will likely be similar across the loads with open sights at 25-50 yds.

I also learned the value of crimp and outside chamfer. Without, the case mouth will hang up solid going in the chamber....

 

[nksmfamjp]

So, things are going well enough. Velocity is a bit off....I’m shooting a max load of H4895, but only getting 2050 fps...Fine for a 458 Win Mag, but this is a real rifle!

I think for now, I’ll keep creeping up in velocity, reading bolt lift and primers.....Any bolt lift is too much as this is a dg rifle!

 

[bruce moulds]

if feeding is a problem with no crimp, there is something wrong with the rifle.
bruce.

 

[nksmfamjp]

if feeding is a problem with no crimp, there is something wrong with the rifle.
bruce.

I thought so too, but let’s think about that for a minute.

With a crf action, you want some extractor tension, right? That will always push the round to one side.

With a belted magnum, you always have the edge in the chamber from the belt.

You can loosen up the extractor until it doesn’t hold the round, but that kind of defeats the purpose....or you can make sure the cartridge mouth is not belled out.

I did that and have no issues.

 

[Opposite Pole]

So, things are going well enough. Velocity is a bit off....I’m shooting a max load of H4895, but only getting 2050 fps...Fine for a 458 Win Mag, but this is a real rifle!

I think for now, I’ll keep creeping up in velocity, reading bolt lift and primers.....Any bolt lift is too much as this is a dg rifle!

Keep temperature changes in mind when approaching max loads. Even with heat insensitive powders they do have some effect.

 

[Forrest Halley]

I cheat on load development. I go to the Nosler web page and find the bullet weight for that caliber and pick the most accurate powder and start at the most accurate load for that powder. I don't care if it's a different bullet that I am using so long as the grain weight is the same. It works out really well.
The Lott data says 74.0 of IMR 4895 @ 3.590 OAL. I will be starting there just as I did with my .375 H&H. My favorite .300WM long range accuracy load hits exactly on the nose for their H1000 load and I developed that with the help of a friend.

 

[nksmfamjp]

Anybody have ideas how to get 2200 FPS from a 22” barrel....I’m planning to dial it up until I feel bolt lift or see flat primers....

your thoughts?

 

[Forrest Halley]

Anybody have ideas how to get 2200 FPS from a 22” barrel....I’m planning to dial it up until I feel bolt lift or see flat primers....

your thoughts?

H335 or TAC and a .450NE bullet? Good way to guarantee the velocity...

 

[Wyatt Smith]

Different powder?

 

[nksmfamjp]

Just asking....why not h4895? I think the issue is the anemic data from Hornady!

 

[fourfive8]

Go to Hodgdon data. Look up 458 Win Mag. Lott is greater capacity so pressures and velocities will be slightly less in the Lott but it gives a safe place to start. Use a chronograph. You should be able to get close to 2200 with appropriate powder. Do pay attention to pressure signs as you posted. I’d try Varget. I load either Varget or Benchmark in my Watts, which is a very slightly larger cousin to the Lott. Also, consider one of the 480 gr bullets. They are called “Express” and have the crimp groove in a place more suitable for some of the older Express carts. However, I found some to work very well in my Watts with the crimp groove in a much better place than so many of the 500 grainers having it located specifically for the Win Mag.

 

[Wyatt Smith]

Some powders give better velocity than others.

 

[fourfive8]

Here's the 458 Lott 500 gr TBBC bullet data from Speer. Barrel length of test gun 24".

 

[Forrest Halley]

Just asking....why not h4895? I think the issue is the anemic data from Hornady!

I looked at Nosler Data and those powders were the only ones that were not over 100% density.
H4895 is at 107% in published maximum . Not a lot of room to run there.
Accurate 2520 maxes at 86.0 and is said to yield 2310 out of a 24".
Upon further investigation I find myself thinking that the Lott is being listed below its potential. Comparison between Nosler Lott data and Hogdon WM data with h4895 is interesting indeed. Seems to be a bit downscaled for sure.

 

[fourfive8]

Here's the Nosler Data.
Each bullet brand, type and design will react slightly differently to different powders and different bores. Each type of primer will yield slightly different results. Each case brand will have slightly different volumes. Each chamber and bore will vary depending on the lab test gun used for any particular pressure test and those variations will affect pressure/velocity data. All these variables will affect test outcomes. Also, each lab may use slightly different MAP thresholds for determining Max Loads.

 

[nksmfamjp]

Maybe there is a Hornady expert out in the wild who can explain this...

458 wm Win LRM Hornady 500gr @3.310” oal
H4895 66.5gr-75.7gr for 2150 fps


458 wm Win LRM Hornady 500gr @3.585” oal
H4895 64.4gr-74.2gr for 2150 fps

Can this be explained in any way? There is nearly 0.3” more powder space in the larger round!

Which explains why they get 2300fps from their ammo!

 

[Forrest Halley]

Maybe there is a Hornady expert out in the wild who can explain this...

458 wm Win LRM Hornady 500gr @3.310” oal
H4895 66.5gr-75.7gr for 2150 fps


458 wm Win LRM Hornady 500gr @3.585” oal
H4895 64.4gr-74.2gr for 2150 fps

Can this be explained in any way? There is nearly 0.3” more powder space in the larger round!

Which explains why they get 2300fps from their ammo!

DGS= Dangerous Gonna Shatter
DGX= Dangerous Gonna Xplode

 

[sgt_zim]

What are we planning to hunt with the Lott?

Cape buffalo have a heart that's about 12" in diameter. As long as you can group your Lott at 3-4 MOA, you're golden.

For ele, you're shooting maybe 40-50 yards max. Never been after ele, but sure looks like a lot of shots are 25-30 yards. Even 10 MOA at that distance turns into a 2.5-3" group.