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Sir Ron,

After reviewing the prints and description of the Manson vs. Clymer reamers it’s clear that there would be a difference in the rifle chambers cut with one vs the other. But only in the throat & leade dimensions, not in the case dimensions.

However, the FL sizing die needed would seem to be the same regardless of which chamber the cartridges were fired in. Although loads required for equal MVs would probably be slightly different due to the effect of throat length ane diameter as well as leade angle on chamber pressures, headspace and fired case diameters shouldn’t vary, given equal PSI.

This will probably simplify acquisition of resizing die, if it were cut with a resizing spec reamer based on the original 460G&A reamer dimension.

Do you think these are valid asumptions?

Yes, reloading dies should be same for both
chamber reamers.

A friend has a stainless synthetic Model 70 Classic in 300 RUM that he was going to use for a 404 Jeffery build, but has changed his mind. If anyone wants to pursue a conversion project, let me know and I'll put you in touch.

👍

Sent you a PM

Just heard from CH4D today. Fortunately one of the two 460 G&A dies they have in stock matches the chamber reamer I have from Dave Manson. Should be in hand this week. The other die may be for a rimmed (?) version.

Also seems the barrel from Douglas will be delivered today. So far have caught some very lucky breaks. This may come together on time yet.

Formed the first 5 460 G&A cases easily today in the CH4D sizing die with one pass using 404 Jeffery basic cases. Set headspace on these cases to the dimension of the Mason go gauge. The formed cases required trimming of almost almost 0.15” of the neck to achieve the max COL of 2.800”. They’ll serve as the basis for dummy rounds for the GS building the rifle to ensure 100% function as a DGR.

Moving the shoulder forward and decreasing the taper, compared to the parent 404 J case, was obviously a very good idea. Given that the 500 grain 0.458” monolithic solids are longer than the 400 grain 0.423” bullets, the taper change and relocating the shoulder forward prevent loss of powder capacity. Although I’ve not measured the capacity I anticipate that these changes may have increased the capacity slightly. It’s also obvious that the 3.6” COAL, which allows building this cartridge in a standard Win M-70 length action does not maximize the newly gained powder capacity.

Because I have a 450 Rigby DGR I’m having an opportunity to compare it to the 460 G&A with respect to design of the 2 cartridges. If the 460 G&A were built on a true magnum length action, such as the Ruger RSM or one of the magnum Mausers, a COAL of 3.720” could be achieved. Loading a 500 grain monolithic bullet (Barnes, CEB BBW #13) would preserve the entire powder capacity of the 460 case, with the base of these bullets flush with the neck-shoulder junction. Of course, the whole rationale of the G&A cartridge is to provide similar performance to the 450 Rigby or Dakota with less powder, albeit at a higher chamber pressure, while allowing building it in any action that allows 3.6” COAL (ie, 375H&H length) cartridges. Slighter shorter bolt throw (probably insignificant functionally) but greater selection of actions (much more important).

I’ve been documenting the process so far and will post the pics at some point, once the rifle is ready and load development is underway.

Very interesting, thanks for sharing.
My .458/.338 Lapua Mag with 2.7" case length has about identical case capacity to your longer and skinnier .460 G&A.
I will be able to use any load data you develop, so please do pass along any loads you find particularly agreeable.
As to COL limits caused by throat length and magazine length,
I understand your pain.

I do not suffer from it myself, however.
My .458/.338 LM has a .458 WinMag throat and is built on a CZ 550 Magnum.
Can be loaded to 3.8" COL in the CZ with +3.8" mag box.
Going from 3.6" COL to 3.8" COL adds about 8.3 grains of H20 net water capacity.
That is 4.166 grains of water for each 0.1" length of shallower seating, with a .458-caliber bullet.

Why is it that so many folks cling to their tight throats ?
I am sold on the .458 WinMag throat after thousands of rounds of handloads tested in it.
The 460 Weatherby Mag throat is also way long, but of tighter diameter.
I used to shoot cloverleaf groups with that throat at 100 yards also.

Anyway, get some 404-gr Shock Hammer bullets and use them at 2500-2600 MV in your .460 G&A.
You will be able to do that at COL of 3.580" with no re-throating:
2.800" case + 0.780" nose projection, seated deep.
You will need no other bullet unless the game is heavier and thicker-skinned than a ton of cape buffalo.
But, truth be told, that load would probably be sufficient for elephant,
though an FN solid would be cricket.

Thanks for the advice, Sir Ron. I’ll post load data once the rifle is completed and we enter that phase. Hopefully mid-Spring 2023. The components will ship to the GS who’ll build the DGR tomorrow. I’ve seen one of his rifles at work in Zim and decided he was the right guy to build this one for me. Unpretentious, all business and reliable.

As to bullets, I’ve been looking at the Hammer’s website today. I was surprised they have so shamelessly neglected those of us disciples of the 404, so wrote them a brief missive - how about a 400 grain 0.423” bullet?

For my upcoming hunt in Zim I’ll use CEB BBW#13s. I’ve used them in the 500 NE 3” and 404J last year, with great success. Though my target is more than a ton of buff and I believe you may be right about the Hammers on pachyderms, I’ll stick with the monolithic solid, at least on this trip.

I’ll order some 0.458” Hammers and test them at some point, as I’m planning on putting together a 458WM No. 1 from components in hand and will use the 458WM+ data you’ve developed in that rifle. My current 458WM Ruger M-77 bolt’s magazine won’t allow longer COALs.

After a shipping incident by USPS resulted in a broken stock requiring a return trip to the GS who built the rifle, the 460 G&A is finally home! The replacement Super Grade stock has better figure than the original one and is now fully bedded once again, including the added barrel recoil lug and crossbolt . The build came in at 9 1/2 lbs loaded, so most likely another 8 oz lead will go into the buttstock next week, after I shoot the initial loads.

Planning to test the rifle with the originally published loads, H-4064 with a Hornady 500 grain DGS. Will work up to as close to 90 grains as possible, depending on recoil and MV. Will likely try a couple of other similar burn rate powders also. The feeding, extraction and ejection with dummies loaded with 500 grain CEB BBW #13 FPs is flawless, as anticipated. The newly fabricated box holds 4 cartridges with a COAL 3.64”.

Unless some unanticipated problem arises during load testing, this will likely be the primary rifle for Zim this summer. It is trim, balances well and fits quite well, with the NECG rear peep and white line post FS aligning quickly and reproducibly. The Ruger RSM 450 Rigby Rimless will arrive in a couple of days, so a test with known loads will be in order.

May well be that after a long respite, the 460 G&A will experience a brief African rebirth. The more things change, the more they remain the same.

Now have all 3 heavy rifles which are suitable for the upcoming safari to Zim in a couple of months. The middle rifle is the Ruger RSM 450 Rigby Rimless for which I’ve already developed loads for the CEB BBW#13 500 grain solid at MVs up to 2400 FPS. It had some feeding problems which were corrected by Mark Cromwell at NECG. Feeds more smoothly than ever and holds 3 in the magazine. A bit heavy at 11 lbs loaded which is ideal for the level of recoil. It is very well balanced and lines up the sights naturally when shouldered. As soon as I sight it in with the new NECG rear peep, this one is ready.

The top rifle is the Ruger Hawkeye 458 WM I’ve described in the 458 WM thread. A bit more load development with the CEB BBW#13 450 grain solid propelled by AA-2230 and Varget should get MV close to 2250 FPS. This rifle will definitely make the trip.

The bottom rifle is the new Win M-70 Classic built in 460 G&A by Gene Simillion. Holds 4 in the newly built box, feeds smoothly with dummies with the 500 grain CEB. I’ll start load development using H-4064, RL-15, and BL-C(2). Currently this rifle weighs 9.5 lbs loaded, but with realistic prospects of reaching 2350 FPS with 500 grain bullet, it needs a bit more weight, so I’m planning to add 1/2 lb lead in the buttstock. The rifle has turned out to be what I was looking for from Gene - a working DGR which will work every time, without drama. The work is flawless and the rifle unpretentious, though the replacement buttstock grain is much better than I anticipated. This is the rifle I hope works well when I develop loads, as balance and anticipated weight should make it sleek and totally dependable.

Will report after the next range session.

Good work.
Down sized to display in the scroll:



2350 fps with the 450-gr CEB Brass FN Safari Solid is a nice load for any 24"-barreled .458 WinMag:



Are you using Redding dies on the .458 WinMag ?
FL sizing with those resulted in wasp-waisted loads for me.
Using RCBS FL sizer does not squeeze down the .458 WM brass as much and makes a prettier load.

RC,

I’m using RCBS dies for the 458 WM. The cases you see are cutoff 458 Lotts. I didn’t internally ream them so that results in thicker walls.

They’re from an old 458 Lott RSM that has gone down memory lane but it’s what I had most when I made these dummies.

I now have proper new 458 WM cases and will use those for sighting in and the trip.

Good catch!!

Brief range report of the first firing of the 460 G&A Win M-70. The rifle was built by Gene Simillion.

Started out with the original IMR-4064 loads developed by Tom Siatos. Fired Barnes 500 grain monolithic solids with 84.0 grains (MV = 2332 fps), 86.0 grains (MV = 2375 fps). I didn’t fire the 88.0 grain load having passed target MV of 2350 with the 86 grain load.

Also fired RL-15 loads with the 500 grain Barnes at 84.0 grains (MV = 2214 fps) and 88.0 grains (MV = 2256 fps). Will probably load 90 and 92 grains with the CEB BBW #13 500 grain monolithic solid for the next session as this is a slower powder than the 4064 and there’s sufficient room in the case without much compression.

Last batch was loaded with BL-(C)2 with the same 500 grain Barnes solid at 84.0 grains (MV = 2272 fps) and 88.0 grains (MV = 2343 fps). Will also load 89 grains with the CEB 500 grain solid for the next session.

All shooting was at 25 yds with peep sight and MVs are measured at about 10 yds uncorrected. This will be the second rifle for the Zim safari with the Ruger Hawkeye 458 WM described in the 458 thread and also fired today.

The rifle is very accurate, comfortable recoil - even seated at the bench - so I’ve decided to not add any weight as I had planned.

Thanks for sharing.
Good data to use in my .458 Ted Williams Thumper (.458/.338 Lapua Magnum Unimproved).
Very similar in case capacity to your .460 G&A.

Got to the range today to try a new load in the Win M-70 Classic 460 G&A. Given current powder supply conditions, I decided to try a powder other than IMR-4064, because I have a small supply of that powderleft and it seems to be out of stock just about everywhere.

Looking at the powder burn rate charts, I realized that RL-15 is a bit slower that IMR-4064 and my prior data showed that an 86 grain load produces a mid-2200 fps MV. Given that the 460 G&A case has a volume to the neck-shoulder junction (measured wit BL-(C) 2) of 100 grains, I loaded the CEB BBW #13 500 grain FPSS with 90 grains of RL-15 - I have an adequate supply of this powder - and fired 6 cartridges with it today. MV corrected at 8 yds is 2410 FPS with SD = 4, max spread = 11 FPS KE = 6449. The RL-15 experiment seems to be a success, because it produces excellent MV with markedly less compression than IMR-4064 due to the small granule size.

Here’s the target at 25 yds, with successive adjustments to zero



I also wanted to determine the sighting system to use. The Leupold 1-4x25 produced good groups but the rings wouldn’t hold it in recoil. I’m not totally sold on using magnified optics for elephants in herds.

The Holosun 530 produces an excellent sight picture with very comfortable cheek weld. However, the scope base loosened under recoil despite torque screws fully tightened. I believe the height of the QD mount provided wit the 530 results in significant angular velocity. I changed out the factory high mount for an aftermarket QD lever mount and will try that next week, with the torx screws Loctited in place. I’m hoping to avoid having to epoxy the base to the receiver but that may be the next step. I’ll also ry the NECG peep in a forward receiver ring base.

Once the sighting system is finalized, both the DGRs will be ready. Tempus fugit now.

Hey hey hey, RL-15 was my pick for the .458/.338 Lapua Thumper. Excellent with 500-grainers and 350-grainers.

The only time I don't 8x40 and JB-Weld scope bases on .458s
is when the rifle has integral bases
or with a Near Mfg. Picatinny having a recoil stop on the bottom of the rail.

Considering both measures. For the next session switched over to Warne lever actuated QD steel rings and Loctite on the base torx screws. I don’t have a competent GS within easy driving distance and don’t want to send the rifle away at this late stage. We’ll see what solution I can rustle up.

Since you mentioned the Thunper, I happened to run across a box of 338 Lapua brass in the shop yesterday and got this photo, just for perspective on ‘other’ 458 wannabes.




450 Rigby on the left, 460 G&A in the center and an unaltered 338 Lapua on the right.

Spent time time stamping the first 10 cases as “460 G&A” yesterday. Will post some pics of the stamped bases when I finish a few more. Need to turn out 30 stamped, formed cases to load cartridges which will pass muster upon arrival in Zim.

Excellent to get any tips on headstamping blanks.
Do you have your own bunter and press or some other method?

Near identical case capacity to 460 G&A is the .458 /.338 LM:



My favorite load in the Thumper was RL-15 and 450-gr North Fork softs and solids at just over 2600 fps.
Uniform and accurate.
That was in a 22" barrel, 1:12" twist, throated like a .458 WM.

I have a 1 ton press but I’m stamping by hand instead as I’m getting better results. I built a jig but it didn’t work well. I don’t have enough time to start over so will need to redesign and build another when I get back.