Some of my musings from last year, I might be finally crazy enough to act, after years of poopooing the idea:

Quoting my fearful self of old:

"Pressure against the inside of the cartridge case generates force that thrusts the case rearward against the bolt face in the action.
This is resisted by the locking lugs.
Same pressure in a bigger case generates more thrust against the bolt lugs that prevent rearward movement of the bolt.
Shear strength of the bolt lugs, and the lug recesses, have to be sufficient to prevent failure.

A real mechanical engineer and gunsmith like Rusty McGee might be able to do the measurements and math, not me.

As Rob pointed out, metallurgical properties, heat treat, etc. of the action are involved, besides the physical measurements of the lugs,
and the pressure inside the case head,
and the surface area inside the case.

I thought about doing a sporting .408 Chey-Tac just for kicks.
I read the roll stamping on the CZ 550 Magnum action of my .505 Gibbs.
Stated pressure limit is 3800 bar, 55,100 psi.
The .408 Chey-Tac max pressure is 63,800 psi,
using the same case head as the .505 Gibbs.

Some would guess that the CZ 550 Magnum action is engineered to handle 1.5 times the engineer-lawyer recommended pressure limit.

I have not done all the measurements and math.
But, the area inside the case rear face should be roughly proportional (by pi-are-squared) to the diameters of various cases.

If they are rimless, beltless, non-rebated cases,
like a .505 Gibbs and a .416 Rigby,
that rough comparison may be made based on base diameter just ahead of the extractor groove.

.505 Gibbs: about .640" diameter, area = 0.7854 D^2 = 0.322 Sq.In.
.416 Rigby: about .590" diameter, area = 0.7854 D^2 = 0.273 Sq.In.

Thrust: Pressure x area

Max thrust allowed for CZ .505 Gibbs = 55,100 psi x .322 Sq.In. = 17,742 pounds force

So for a CZ .416 Rigby, max thrust should be same (same locking lugs, same action except bolt face).
Max pressure allowed then would be roughly:
55,100 psi X (.322/.273) = 64,990 psi
rounded to three significant digits = 65,000 psi

So I better keep my .338 Lapua based wildcats down to 65,000 psi even if the brass is spec-ed to 68,000 psi?

And standard .408 Chey-Tac loads are about 8000 psi too hot for a "sporting featherweight" CZ 550 Magnum so chambered?

Yet CZ chambers their 550 Magnum for .338 Lapua Magnum, with a CIP pressure spec of 4700 bar, 68,150 psi?
Close enough to 65,000 psi to be acceptable with a 1.5X safety factor for over-engineering-and-over-lawyering?

I have no idea what the MRC PH action (0.800" or greater bolt diameter?), or GMA Magnum Mauser action with 0.750" bolt diameter, can handle.

CZ 550 Magnum, Ruger M77, Winchester M70, standard Mauser M98: all have similar .700" bolt diameter, and similar locking lugs.
No comment on Remington M700, or Weatherby MkV from me ..."

quote:

Originally posted by RIP:
Fear not:
Even the CZ 550 Magnum is approved for a steady diet of 55,100 psi (3800 bar) with a Gibbs case head in a 1.200" diameter barrel knoxform.
At that pressure, the sporting .408 CheyTac can propel 305-grain bullets at over 3125 fps from a 26" barrel.
It is about time we had some of these!
The 63,817 psi (4300 bar) max load for the .408 CheyTac will not even equal a proof load for the 10-pound sporter.
And recoil is pidly compared to what many "okes on the ground" put up with.
The .408 CheyTac could also be thought of as the "400 Underkill" when compared to the "600 Overkill."
Of course this refers to effect on the shooter, not on the game.

Hey, RIP, you better go easy on us or I may want to turn in my 416Rigby (3000fps 300grains) for a Gibbs wildcat.

On the technical side, is the 3800-bar stamp on the receiver or on the barrel?
I ask because the CZ barrel contours are rather short at the breach end. If the stamp is on the barrel, then one solution would be to use a 3.5" long contour at the breech.

PS: it is comforting to see your figures approve the CZ 550 Rigby-heads out to 65kpsi.
I assume that my loads are around 60k, judging from below-max Fed215GM primers and extraction. E.g. 350 grain TSX at 2820fps using 102.5 grains Rel-17. Can anyone check Quikload? (Remembering, of course, that QL data on R-17 is relatively new.)

Tanz,

Re-17 with .416/350-grain Barnes TTSX for .416 Rigby will be a worthwhile QL to look at the velocity and pressure estimates.
I will do it this coming weekend when I have the program and some sample bullets at hand.
Will assume 25" barrel like CZ.
Will do the powder survey to compare to other powders, like above for 400 Underkill.
Just cannot do it right now.

.408 CheyTac (aka 400 Underkill) recoil levels: Underwhelming compared to a similar weight 600 Overkill.

26"-barreled 400 Underkill, 10-pound and 11-pound comparison for scoped rifle weights loaded like so:

Load: 305-grain bullet weight, 152.0 grains of Retumbo Extreme by Hodgdon,
pressure 55,075 psi, velocity 3130 fps:

Free Recoil of 10-pound 400 Underkill: 88.4 ft-lbs @ 23.8 fps

Free Recoil of 11-pound 400 Underkill: 80.4 ft-lbs @ 21.7 fps

Very do-able. I am merely tickled by anything with recoil of less than 100 ft-lbs @ 30 fps, free recoil energy and velocity.

A mere spacewalk impulse thruster.

quote:

Originally posted by RIP:
.408 CheyTac (aka 400 Underkill) recoil levels: Underwhelming compared to a similar weight 600 Overkill.

26"-barreled 400 Underkill, 10-pound and 11-pound comparison for scoped rifle weights loaded like so:

Load: 305-grain bullet weight, 152.0 grains of Retumbo Extreme by Hodgdon,
pressure 55,075 psi, velocity 3130 fps:

Free Recoil of 10-pound 400 Underkill: 88.4 ft-lbs @ 23.8 fps

Free Recoil of 11-pound 400 Underkill: 80.4 ft-lbs @ 21.7 fps

Very do-able. I am merely tickled by anything with recoil of less than 100 ft-lbs @ 30 fps, free recoil energy and velocity.

A mere spacewalk impulse thruster.

Yes, that is within huntable levels with reasonable recovery for multiple shots. Maybe not a bread-and-butter impala load, but doable when buffalo are in the woods. I went through similar calculations 20 some years ago on the 416Rigby. Jack O'Connor had written that the 416Rigby was a wonderful cartridge. He thought that 400 grains at 2400fps was OK (it is), but that 400 grains at 2600fps was too severe. (not.) The last load is comforting when buffalo are around. Now you're only asking for 2800fps, or 2950 with 350 grains. Shake, (rattle?), and roll. Buffalo's down. Eland are in trouble.

416Tanzan,

Here you go, estimated bullet boat-tail from photo of bullet,
estimated start pressure based on percent bearing of the mono-copper with 4 cannelures,
estimated COL of 3.760",
25"-barreled .416 Rigby,
default case capacity from QL,
assumed max average presure of 63,817 psi is not the default:
Looks like you better quit around 2800 fps with the 350-grain TTSX and RL-17.
For what QL is worth:









Here is the DSRG M1999 PH, arrived within 2 weeks of order from MRC.



The walnut stock available from MRC, the action is too big to fit the CZ Kevlar stock.
Maybe stainless and walnut will look sharp:



The front receiver diameter is about 1.505" and the threads look like about 1.2"x16tpi.
Barrel shank diameter is going to have to be bigger than 1.250".



The bolt diameter is about 0.805" and the extractor does fit the .408 Chey-Tac case nicely:





Inside box length is about 4.070", and it it easily fits and feeds cartridges up to 3.980" COL,
feeds the flatnose solid too:







Action screw spacing is about 8.250".
Trigger is excellent, a crisp, no-creep 48-ounce pull weight, 3.0 pounds.
Action weight on my scales was 3 pounds and 14 ounces.

This action looks great.

Thanks, RIP.

First, congratulations on a very impressive action. It sure looks capable of Gibbs cases.

On the Quickload, that is useful for knowing what some batches of R-17 might do and for the 350TTSX.
I've got a couple of boxes of TTSX waiting in the US for loading and transport over the ocean, just haven't found the right timing. One little item different from your loads is that my current batch of cartridges in TZ are the 350 TSX. Those are flatbase and probably give a couple of grains extra capacity to the calculations.

One puzzling item in the data lists is that QL rates 96 grains of R-17 at the same pressures as 96 grains of Ramshot BigGame. BigGame is normally rated faster than the 4350's and Alliant suggests using IMR4350 data for their R-17. Apparentally, the Quickload parameters for R-17 are for a relatively fast batch of powder since it gives 98 grains for IMR 4350 at the default pressure. Presumably, the lawyers at Alliant are happy with IMR 4350 data.

According to Quickload, then, my 102.5 grains of R-17 should be turning in 2950fps and over 77000 psi! Kawabunga, Buffalo Bob! (But with the TTSX.)
It looks like Quickload is running a bit hot for my batch of R-17, though as mentioned above, I am still using TSX rather than the longer TTSX.

So our loads are not as hot as predicted by QL and still producing such nice primers and extraction. It might also mean that two separate chronographs are out of calibration--always a possibility with one, but less likely with two (one was a Pro-Chrono, one, yes, a Chrony that has worked well for three years and with reasonable results on 338WM and 416). Now I will admit that one testing at noon under a hot Tanzanian sun did produce readings in the 2825-2900 fps range using two 416Rigby rifles. And for full disclosure, this year the same Chrony, after freshly bouncing over hundreds of kilometers on dirt roads, went up to 3000fps in cooler weather with the same batch of cartridges, so it was retired. It also clocked an older batch of 2650fps-cartridges (with a surplus AccurateArms powder) at 2800.

Here are pictures of last years cases and bullets.
The SMASHED 350TSX and nice looking Fed215GM primer is from a buffalo face shot, 70 yards at a previously chrono-ed 2825fps. Yes, 102.5 grains Rel-17.


And for comparison, below is a 350 TSX bullet from a hartebeest, 180 yards, through front leg and deflected off of spine, assumed 2825 fps, nice primer, 102.5 grain R-17:


Assuming that the other powder calculations are more stable for QL, it looks like H4350 at 99 grains would be a nice load, maybe needing 100 in our rifle-chambers with the TTSX. MRP would work except that I would shy away from a 110% load density. I've not expected to need powders significantly slower than the 4350's. In any case, reloading can get tricky when the rifles are 11 time zones away from load development facilities. I'll definitely need to ferry over a new chronograph the next time I bring a batch of yet-to-be-tested loads. It is easier to take a couple of grains out of a load if testing requires, than to add non-existant powder. Each grain to be added would require cannibalizing one precious round. Such is life overseas. I've also got to juggle the question of bringing over a batch of CEB 307 grainers and the 500 AR-Nyati with loads of 350 gr CEB or 450 GSCustom, whenever it is ready. Travelling is always a hassle and requires a trip without significant layovers all the way to TZ. If my wife accompanies me we can get two allotments of 5-kg ammo.

416Tanzan,

QL disclaimer says the velocity and pressure could vary with powder lot variation, so they claim that RL-17 96.6 grains could be either:

2887 fps at 75,995 psi
or
2660 fps at 52,722 psi, with the .416/350-grain TTSX.

TSX instead of TTSX at same COL will also increase case capacity and lower pressure, as you say.

The case-filling % of the QL data is also different than reality by quite a bit sometimes.

Actual, measured case capacity being used (gross water), instead of the QL default value, would be another needed refinement.
What .416 Rigby brass are you using?

I always give a rifle a female name, as Davy Crockett did "Ol'Betsy."
Not like Daniel Boone, who named his rifle like a dog: "Tick Licker." I suppose he meant it was good enough to lick the tick off a dog at 100 yards,
and I do not think he had any woman in mind for that talent.

When I picked up the action from Rusty yesterday, I checked on Bridget. She is still reclining in the mill at Hilltop Gun Shop & Spa for Wayward Women.

Mentioned I would need a name for the MRC PH 400 Underkill/.408 Chey-Tac.
Rusty said "She is from Montana, out west, how about 'Calamity Jane?' "

Perfect. What better calamity to befall me than a 400 Underkill?

The efficient Will at MRC took my order today, for a walnut PH stock and emailed a pdf of action and barrel specs.

PH barrel diameter at chamber end is 1.326"
and the cylindrical knoxform may be 3.0" to 4.0" long depending on the PH contour chosen, various sporter and target contours.

Some current official specs:

Receiver Thread: 1.1875-16 TPI UNF-2B
Bolt Diameter: .805"
Internal Magazine Length: 4.043"
Action Weight: 64oz (1.81kg)

From MRC:



From netgages.com:

"A class 2A external thread and a class 2B internal thread gives a normal fit."

So PH has a "fractional thread size" of 1 3/16-16 TPI UN-2B or "decimal thread size" 1.1875-16 TPI UN-2B internal thread,
and needs a 1.1875-16 TPI UN 2A external thread on the barrel,
but I ain't no gunsmith.
"UN" versus "UNF" for thread specification is a distinction that escapes me.

The "Go Pitch Diameter" on that 2A thread is 1.1454" and the "No Go Pitch Diameter" 1.1403",
but heck if I know what that means ...

Wikipedia, "ISO and UTS Thread Dimensions":



The "peaks" on the external (barrel) thread are pointier than on the internal (action) thread.

Is a "UNF" thread a "Finer" or a "Funner" Fitter than a "UN" thread?

Also what is this, political correctness??? Calling a female thread "internal" and a male thread "external"???
Calamity Jane does not approve. She calls her thread female!

quote:

Originally posted by RIP:
416Tanzan,

QL disclaimer says the velocity and pressure could vary with powder lot variation, so they claim that RL-17 96.6 grains could be either:

2887 fps at 75,995 psi
or
2660 fps at 52,722 psi, with the .416/350-grain TTSX.

TSX instead of TTSX at same COL will also increase case capacity and lower pressure, as you say.

The case-filling % of the QL data is also different than reality by quite a bit sometimes.

Actual, measured case capacity being used (gross water), instead of the QL default value, would be another needed refinement.
What .416 Rigby brass are you using?

Currently we're using Hornady 416 Rigby brass, which weighs 316-320 grain, new.
Previously we were using Norma, some of which weighed 327-330 grain and some of which weighed 337-340 grains, two distinct groupings of Norma that were sold as one bag of 100. Go figure.

Dan Lilja is making a .408 barrel for me.
JGS offers the .408 Chey-Tac reamer, 20 weeks wait.
I'll go for it since Dave Manson is so swamped that he cannot get back to me on a "400 Whelen Berry of 2013" reamer.
So I wait ... all parts at least ordered.

In hand:
Action, MRC M1999 PH Stainless.

On order:

Stock: MRC walnut, with crossbolts.

Barrel: Dan Lilja stainless, fluted, No. 7 sporter contour, 1:13" twist, 6-groove, .408-groove/.400-bore,
1.350" diameter shank/knoxform is 3.5" long,
0.833" at 26" and 0.825" at 28".

Reamer from JGS.

Dies from Chey-Tac USA.

Brass from Jamison/Captech International.

Lo and behold: Dave Manson's name is on the JGS reamer drawing, the one with inch units instead of mm:



Dave Manson used to work for JGS?
Compare to metric:



Same reamer.
Updated specifications on the date I ordered it.
Both drawings have a 07/11/02 approval date by "CP."

The metric one was designed by Spider Firearms, approved by "CP" on 07/11/02 and update on 12/03/03 also approved by "CP."

The one I ordered was designed by Dave Manson,
approved by "CP" on 07/11/02 and update on 04/05/13 by "SS" who would be Sarah Siewell, the "sales lead" from whom I ordered the reamer by telephone, yesterday.

RIP- Where are these guys coming from? The .600OK was designed for 65K PSI and lets see over 200 built with no failures of any kind? Bolt lugs, receiver lugs. Period. No rims broke off either!!! MY two 0.600OKs were BluePilled at 85KPSI!!! Issue OVER, Settled, FINITO. Go ahead with the Montana PH which we helped design for exactly this kind of cartridge and have no FEAR. A .408 Chey tac at 65KPSI and in the Montana PH action is a insignificant problem. -Rob

quote:

Originally posted by Robgunbuilder:
RIP- Where are these guys coming from? The .600OK was designed for 65K PSI and lets see over 200 built with no failures of any kind? Bolt lugs, receiver lugs. Period. No rims broke off either!!! MY two 0.600OKs were BluePilled at 85KPSI!!! Issue OVER, Settled, FINITO. Go ahead with the Montana PH which we helped design for exactly this kind of cartridge and have no FEAR. A .408 Chey tac at 65KPSI and in the Montana PH action is a insignificant problem. -Rob

"400 Underkill"

quote:

Originally posted by Robgunbuilder:
RIP- Where are these guys coming from? The .600OK was designed for 65K PSI and lets see over 200 built with no failures of any kind? Bolt lugs, receiver lugs. Period. No rims broke off either!!! MY two 0.600OKs were BluePilled at 85KPSI!!! Issue OVER, Settled, FINITO. Go ahead with the Montana PH which we helped design for exactly this kind of cartridge and have no FEAR. A .408 Chey tac at 65KPSI and in the Montana PH action is a insignificant problem. -Rob

Were any of those 600 OK built on a CZ platform? If so, it would mean that the CZ is good for 65k psi, too, with the Gibbs boltface.

-

quote:

Originally posted by 416Tanzan:

quote:

Originally posted by Robgunbuilder:
RIP- Where are these guys coming from? The .600OK was designed for 65K PSI and lets see over 200 built with no failures of any kind? Bolt lugs, receiver lugs. Period. No rims broke off either!!! MY two 0.600OKs were BluePilled at 85KPSI!!! Issue OVER, Settled, FINITO. Go ahead with the Montana PH which we helped design for exactly this kind of cartridge and have no FEAR. A .408 Chey tac at 65KPSI and in the Montana PH action is a insignificant problem. -Rob

Were any of those 600 OK built on a CZ platform? If so, it would mean that the CZ is good for 65k psi, too, with the Gibbs boltface.

-

416Tanzan,
Most of those 600 Overkills were indeed built on CZ 550 Magnum actions.

I will not need any stinking muzzle brake on my 400 Underkill.
I am going to have the barrel stamped, or maybe engraved with a flourish:

".408 Cheyenne Tactical/400 Underkill"

Guys- what is it a new crop of Big Bore people here or what? Probably over 100 .600 oks have been built in CZ550s. Yes they can take 65KPSI all day long! One of Mine has over 1000 ends thru it too! Based on that now some Internet genius is going to spout off on how that's impossible! We worked with Montana arms to design their action to be even more rugged than the CZ550. Where do you think the big bolt diameter and bolt face ideas came from?-Rob

quote:

Originally posted by Robgunbuilder:
Guys- what is it a new crop of Big Bore people here or what? Probably over 100 .600 oks have been built in CZ550s. Yes they can take 65KPSI all day long! One of Mine has over 1000 ends thru it too! Based on that now some Internet genius is going to spout off on how that's impossible! We worked with Montana arms to design their action to be even more rugged than the CZ550. Where do you think the big bolt diameter and bolt face ideas came from?-Rob

Thanks, Rob.
The 600 Overkill is my reason for confidence in the 400 Underkill.

Another .408 barrel source is McGowen: http://www.mcgowenbarrel.com/

McGowen barrels I have:


5 of .510-caliber:

1 of .505-caliber:

3 of 404 Jeffery-caliber:

6 of .395 caliber:

1 of .308 caliber:


All are outstanding, foul little, accurate, and as promptly delivered as one could hope for.

My only gripe with them is that the 404 Jeffery barrels are .425"-grooved, but work great as long as the bullets are a full diameter of .423",
they just require more powder or faster powder to get top velocities (and pressures).
Excellent for any bullet weight with Varget Extreme.

They make barrels up to 1-3/4" for 50 BMG.
For other calibers you need to call for price:

"1 3/8" or 1 3/4" Diameter Steel ... Add: Call for Quote"

The standard sporter barrels there are 1-1/4".

They make a .408-groove/.400-bore, 1:13" twist barrel.



I figure I better stick to 1-3/8"(1.350"-1.375" diameter) at the breech end of a 400 Underkill on the MRC PH ...
But that CZ 550 Magnum that is screaming "Me too!" might just get a 1-1/4" McGowen barrel ...
That is a way to use the CZ Kevlar stock for the "featherweight" 400 Underkill.

From McGowen:



Contour Name...#..........A.........B........... ..C ...........D ...... Max Length .....Estimated Weight (as 30-cal)

Douglas....... #6 D6 ....1.200".. 4.00" ..... N/A .... .750" .... 26"................ 5 1/2 lbs

For a CZ 550 Magnum 400 Underkill, though it will not be a featherweight.

My 416-505 is closer to a range date. Action is now bedded , the barrel channel will be done in the morning. Rough weight with the 29" bull barrel,and the ph action with out the bolt is 14 lbs now. I am shooting for 18lbs I will added about a 1 lb more bedding materialto the butt and fore arm.


The forearm is solid glass and JB weld. I cut all the foam out out of the barrel channel and poured in the JB. I did a real tight full length bedding of the action, the bottom metal and mag box ( two layers of masking tape for clearance) with devcon steal. I will remove about 2" of foam from the butt and pour in some two part expoy to soak the foam with, then add the 2" of jb to finish the stock and provide a way to mount a recoil pad. The MPI stocks take some work to finish. Inletting is close and required a couple hours of work. I suggest bedding tne action and barrel in two passes. Thats a lot of action to get loose and a lot of glass to work at one time. It took almost a full pound of devcon to bed the action.

I will make a rail to bride the action,amd allow more ring options.
How much will I have to mill off the front of the picatinney rail to get 20= 25 moa built in.

I am guessing 408 data should be close for the 416-505.


JD

quote:

Originally posted by J D:
My 416-505 is closer to a range date. Action is now bedded , the barrel channel will be done in the morning. Rough weight with the 29" bull barrel,and the ph action with out the bolt is 14 lbs now. I am shooting for 18lbs I will added about a 1 lb more bedding materialto the butt and fore arm.

So, J D, you done gone tacticool on us?

Hey, you will probably still be 7 pounds lighter and only about 200 fps slower than a .416 Barrett M99 with a 32" barrel. +3000 fps with 400-grainers instead of +3200 fps? And your barrel will last longer.


The forearm is solid glass and JB weld. I cut all the foam out out of the barrel channel and poured in the JB. I did a real tight full length bedding of the action, the bottom metal and mag box ( two layers of masking tape for clearance) with devcon steal. I will remove about 2" of foam from the butt and pour in some two part expoy to soak the foam with, then add the 2" of jb to finish the stock and provide a way to mount a recoil pad. The MPI stocks take some work to finish. Inletting is close and required a couple hours of work. I suggest bedding tne action and barrel in two passes. Thats a lot of action to get loose and a lot of glass to work at one time. It took almost a full pound of devcon to bed the action.

Well, the fiberglass boat remodeling job is not so bad on an MPI if you want heavier.

I will make a rail to bride the action,amd allow more ring options.
How much will I have to mill off the front of the picatinney rail to get 20= 25 moa built in.

How long is the rail you are tilting? I will get out the side rule and do some calculating for 20 MOA .


I am guessing 408 data should be close for the 416-505.

Yep. My .408 Chey-Tac/400 Underkill mid-level loads will be a good starting place for your .416/.505 JD, work up from there.


JD

So, JD, what is the diameter of your barrel at the breech and at the muzzle?
Target taper or straight all the way?
How long is the cylindrical shank/knoxform if any?
What twist?
Who made your .416 barrel?

It seems the perfect diameter for the Gibs case is the .395" Diameter.
300-400 grains of awesomeness. 300 grain for hunting and 400 grains for flat mile shooting.

quote:

Originally posted by boom stick:
It seems the perfect diameter for the Gibs case is the .395" Diameter.
300-400 grains of awesomeness. 300 grain for hunting and 400 grains for flat mile shooting.

I laid down a long time ago and the idea went away on that ".395 Berry Gibbs" aka .395 Bee Gee.

Here was a first attempt at necking the .505 Gibbs down to .395:



Necking a .408 Chey-Tac down to .395 would be easy, but so inconsequential.

J D,

Tangent of 20 MOA = 0.00581783

So, if the anchor points of the front and rear of the rail are 6" apart,
and you want it to have a 20 MOA forward slope, so the rifle will shoot 20 MOA higher:

Elevation difference = (0.0581783) X (6") = 0.034906" = about 0.035"

The rear attachment point will need to be 35-thou higher than the front:

Shim the rear + 0.035"
or file down the front - 0.035"

Substitute any rail span in inches (distance parallel to the bore between the front and rear centers of attachment of rail to rifle)
into the above formula and calculate away.

I love the 375 CT but hey 395 makes a nice middle ground and just a bit more rare than the 408
Talk about an exotic cart...
At least you won't have a restriction on travel with a military chambering.

Alas, if this wildcat cartridge, the .408 Chey-Tac (non-SAAMI, non-CIP), is considered a military cartridge and prohibited somewhere,
then the second one built will have only "400 Underkill"
or ".505 Gibbs/400-Bore" on the barrel,
and use brass to match.

I do think the CT carts make good Timber Dog (Wolf) rounds.
Become a member of the TD SSS sniper team.

RIP and Boom, ye of many rifles--

I think that you will have an easier time getting the right bullets and a wider choice of bullets in .416". Yes, the same argument could be made for the .375", but with Gibbs powder behind the bullet, one should probably go bigger, .416", rather than smaller. But if you want .408", hey, it's still a free country.

416 makes good hand load sense to me.

quote:

Originally posted by RIP:
[QUOTE]Originally posted by J D:
My 416-505 is closer to a range date. Action is now bedded , the barrel channel will be done in the morning. Rough weight with the 29" bull barrel,and the ph action with out the bolt is 14 lbs now. I am shooting for 18lbs I will added about a 1 lb more bedding materialto the butt and fore arm.

So, J D, you done gone tacticool on us?

Hey, you will probably still be 7 pounds lighter and only about 200 fps slower than a .416 Barrett M99 with a 32" barrel. +3000 fps with 400-grainers instead of +3200 fps? And your barrel will last longer.


The forearm is solid glass and JB weld. I cut all the foam out out of the barrel channel and poured in the JB. I did a real tight full length bedding of the action, the bottom metal and mag box ( two layers of masking tape for clearance) with devcon steal. I will remove about 2" of foam from the butt and pour in some two part expoy to soak the foam with, then add the 2" of jb to finish the stock and provide a way to mount a recoil pad. The MPI stocks take some work to finish. Inletting is close and required a couple hours of work. I suggest bedding tne action and barrel in two passes. Thats a lot of action to get loose and a lot of glass to work at one time. It took almost a full pound of devcon to bed the action.

Well, the fiberglass boat remodeling job is not so bad on an MPI if you want heavier.

I will make a rail to bride the action,amd allow more ring options.
How much will I have to mill off the front of the picatinney rail to get 20= 25 moa built in.

How long is the rail you are tilting? I will get out the side rule and do some calculating for 20 MOA .


I am guessing 408 data should be close for the 416-505.

Yep. My .408 Chey-Tac/400 Underkill mid-level loads will be a good starting place for your .416/.505 JD, work up from there.


JD

So, JD, what is the diameter of your barrel at the breech and at the muzzle?
Target taper or straight all the way?
How long is the cylindrical shank/knoxform if any?
What twist?
Who made your .416 barrel?[/QUOT


1".125 dia bull barrel. Duglas 1-12 twist
If I remenber right. 29" long

One could try a Stiller 408 in a repeater or single shot. I have one that I did the 338 Snipe-tac on. 300 gr Begers at 3350 out of a 30 inch barrel.

If you want one built right for a walk around gun contact Dave Viers of Viersco Manufacturing or Black Diamond Rifles.

He does every variant of the 505 gibbs.

The other Gun I am working on is a 550 Gibbs on a Montana Pro acion.

Jeff

quote:

Originally posted by 550 Gibbs:
One could try a Stiller 408 in a repeater or single shot. I have one that I did the 338 Snipe-tac on. 300 gr Begers at 3350 out of a 30 inch barrel.

If you want one built right for a walk around gun contact Dave Viers of Viersco Manufacturing or Black Diamond Rifles.

He does every variant of the 505 gibbs.

The other Gun I am working on is a 550 Gibbs on a Montana Pro acion.

Jeff

I spoke to dave yesterday. He made my dies for me. Great workmanship. very impressive dies. He knows his shit. I have a mpi sporter stock avaible if you need one for the gibbs.

JD

quote:

Originally posted by 416Tanzan:
RIP and Boom, ye of many rifles--

I think that you will have an easier time getting the right bullets and a wider choice of bullets in .416". Yes, the same argument could be made for the .375", but with Gibbs powder behind the bullet, one should probably go bigger, .416", rather than smaller. But if you want .408", hey, it's still a free country.

Yes, free country, for now!
Not trying to be sensible or practical here, have plenty of .416 rifles.
I really need a .408 rifle like I need a hole in my head.
So, hey, the die is cast. The "400 Underkill" will be a true .40-bore, a .408-caliber rifle.
Ain't freedom grand?

For those looking to do a 408 Chey-tac. I know Dave Viers has a reamer. But my gunsmith in Iowa under the handle of RWSynder has done my 338 snipe -tac. Well his reamer list shows a 408 chevy-tac, plus many others. He does many of these guns a year, more tactical than hunting. He is on sniperhide forumn more than any others. But if you would go with him he is great to work with. Oh if you do call or let him do some work, tell him you seen a post from me a Crazy Cowboy from Wisconsin.

I have a hankering for a .408/350-grain "400 Underkill" bullet.
I reckon it will have to be a custom run,
and will be truly "underwhelming" by .408 Chey-Tac standards for BC.
But meanwhile I could collect sizing dies and a press capable of reducing a Barnes .416/350-gr TTSX down to .408" diameter.
Should be fun.

No, wait a minute ... I need the heaviest bullet weight that will go 2800 fps at 55,000 psi and fit a COL of 4.000" for magazine box feeding,
with acceptable BC for KISS Principle,
one bullet weight for everything!

This is gonna take some figurin'.

There is a new batch of dies for the .408 CheyTac.
Your choice of either 1.25" or 1.5" diameter dies.
Mine are 1.5" and shipping by UPS.

What is the velocity differential of the 416 Rigby and sporting 408 underkill at the same CIP 47k PSI?

quote:

Originally posted by boom stick:
What is the velocity differential of the 416 Rigby and sporting 408 underkill at the same CIP 47k PSI?

Is there anyone who is really bored and wants to set up a couple of rifles with strain guages to answer this for boom stick?
Maybe he would be satisfied with some QuikLOAD doodling by a big-bored person?

Probably the .408 CheyTac would beat the .416 Rigby by about 300 fps with same bullet weight, whether it is at same low pressure or same high pressure.

When I get bored enough I will do the doodling with select powders.