338 - 500 Jeffrey

[Brent]

My gunsmith sayes he will build me one. Is there a particular action that would be better suited for this than another? Does anyone make a reamer yet, and what whould you think the performance would be with the 300gn M-king and a 36" barrel? What weight range would keep recoil below a .308win?

 

[Gary Rihn]

Maybe I misunderstood something, but I don't see how you're going to take a 300 gr bullet & a bucketful of powder, and keep recoil below a 308 Win.

With any reasonable load (and why build something like this if you're not going to shoot loads that take advantage of it), I just don't see bringing the recoil down by using weight.

I'd think your best option to tame the recoil would be a *good* muzzle brake.

 

[Len Backus]

Brent

I am e-mailing you an Excel spreadsheet which calculates recoil. You just have to input four parameters to get your answer. Weight of bullet, weight of rifle (which is your question), weight of powder and velocity of bullet.

I don't know what your .308 assumptions are or I would just venture an opinion on rifle weight myself. You'll have to do a bit of trial and error to get the answer from the formulae. E-mail me if you need an explanation of the spreadsheet.

 

[Darryl Cassel]

Brent

With a 36" Tapored barrel, and to keep the recoil to that of a 308 you need BOTH weight and a GOOD muzzle brake.

How about something like a 22# rifle with a bipod and a large KDF brake.

I have a friend who built one on the same case as I shoot (338/416 Rigby IMP) and has his at 22# with a 36" tapored barrel and a Mark 4 Scope. We only use the 300 Gr Sierra MK bullet.

The recoil is not bad with the weight and brake combination. You will need both to make it as comfortable as possible when shooting.

By the way, he is the same guy who killed the elk at 2890Yds with that rifle.

Darryl Cassel

 

[Brent]

Yes, I will be useing a brake, but was curious as to what additional weight would be needed in the stock to accomplish this, around 15 lbs. recoil. Velocity will be kept at near max, not reduced unless needed for accuracy improvement.

I shoot a Ruger in .416wby without a muzzle brake now so heavy recoil doesn`t bother me much anymore. Just shot a lucky 3.1" 3 shot group at 700yds yesterday and a 6.2" at 600yds too. I love to shoot the .308s too, but neither one will do 2000yds like this one will.

Any guesses at the gain in velocity over the .338-.416 Rigby IMP? Dave, my smith, just built a .300RUM with Rem. action, barrel blocked 36" Lilja barrel, Leopold scope, Jewell trigger and a heavy laminate blank was kept wide and flat at both ends for the bench, the weight is 24# I believe. It shoots under 1" groups with just 200gn Nosler partitians with the first loads at 500yds. When the 2 OZ. trigger is pulled, free recoil slides the rifle about 1.5" in the rest. A very sweet rifle.

 

[Darryl Cassel]

Brent

Probably/possibly not a gain in velocity over the 416 Rigby IMP.
The inefficiecy of a larger case many times causes the velocity to drop. It seems that, the 416 IMP is about at the top of the efficient scale for the 338 bullet using 300 gr bullets and long barrels.
I once tried a 50 cal spotter round necked down to 338 and shot the 300 gr bullet. With 145 grains of powder the velocity of the 300 gr was below my load of 122 grs in the Rigby IMP. using the same powder.
You don't always need added velocity over what the 416 IMP will give you if you have the correct length barrel.

The 300 gr bullet works very well on kills at velocities between 3100 and 3250 fps.
As stated before, I have run mine to 3300 FPS if I don't care about loading the brass more then 2 times.
Drop it back to the 3150 to 3250fps range and you have a fine functioning combination that can be loaded many more times and the bullet will repeat shot after shot at extended range.

If you take the 378 Weatherby case and improve it like the 416 IMP you will have about the same powder capacity. We use a 35 degree shoulder with minimum tapor for extraction and move the shoulder forward to make the improved case.
It's a rather impressive looking case when fireformed.

Sometimes (not always) going bigger then what has already been tried and tested, especially when working with loads over 100 grs of powder, will work against you.

Anyway, just a thought concerning the larger case capacity cases.

Good luck in your venture.
Darryl

 

[Len Backus]

Brent

Ok, I'll venture a guess as to the weight required. According to the excel spreadsheet I use for recoil calcs:

A 9 pound, un-braked .308 has around 17 pounds of recoil.

I don't know just what your load is for your big gun. Assume 300 grain bullet, 130 grains of powder and a velocity of 3,200 fps. This means an un-braked howitzer needs to weigh around 50 pounds.

Correct my load assumptions if you like and I will run it again.
(I couldn't get your email address to work)

 

[Len Backus]

Brent

I should have mentioned the brake option. If we assume 40% reduction in recoil. The necessary weight of the rifle goes down to about 30 pounds with a brake on the big gun.