Reamers .458 Lott vs. .450 Watts

[fourfive8]

Doesn’t matter what the reamer specs are on paper. Ream the chamber then use a simple plug type chamber length gauge to get exact chamber length. Trim brass to AT LEAST .005” to .010” shorter than that number.

Next step…. find bullet jam-to-land contact length for any particular bullet. Then seat that bullet to allow for AT LEAST .030” clearance from the jam length for that bullet. Most times the bullet’s crimp groove will determine seating depth. Just make sure the bullet has at least .030” land contact clearance when properly crimped.

Check feed and cycling function for any loaded ammo.

 

[John P.]

Exactly what this device is for:

 

[Riflecrank]

The SAAMI .458 Lott chamber is 2.810" long, allowing only 0.010" for case stretching on firing.
Better trim it to 2.790". Max brass 2.800".

The .450 Watts Magnum of 1949 first shot has a chamber that is 2.870" long, allowing 0.020" for case stretching, and 2.850" maximum brass length.

SAAMI specifies a minimum chamber length and a maximum brass length.
The reamer maker can make a .458 Lott reamer of greater length than the minimum and call it a .458 Lott, but it is a sloppy job.

In 1971 Jack Lott took a reamer for the .450 Watts Magnum that was designed for re-chambering
a SAAMI .458 WinMag rifle and stole the valor of James Watts by declaring a new cartridge of 0.050" shorter length.
That reamer had a non-cutting belt stop and no throat, it blended into the existing SAAMI .458 WinMag throat.
The SAAMI .458 Lott is shorter throated and cannot perform to has high a level as Jack Lott's "wildcat"
or even the SAAMI .458 Winchester Magnum if it is non-SAAMI-loaded to same COL and higher pressure/MAP of the SAAMI .458 Lott.

Jack Lott's sketch:

From a Nick Harvey article, same reamer re-drafted:

SAAMI pressure barrel chamber drawings are more directly "readable" for chamber length:

You can load a SAAMI .458 WinMag to longer COL than you can load a SAAMI .458 Lott.

Here is the PT&G reamer of Dave Kiff that matches the SAAMI .458 Lott chamber:

Easy to make your own GO and NO GO gages by seating a flat-based .458-caliber bullet backwards into the case. You will find that you need longer ones for the SAAMI .458 WinMag than for the
SAAMI .458 Lott, of course.

Best to use a SAAMI .458 WinMag reamer to re-throat a SAAMI .458 Lott chamber.
I call that the .458 Watts Express.
It is like Jack Lott's first "wildcat" without the extra 0.050" slop in chamber length.
Actually brass of 2.85" is of no benefit over the 2.800" brass.
If I had my druthers for a .375 H&H-length magazine box, I would make the brass 2.700" long,
chamber 2.720" long with a .458 WinMag throat, and call it the .458 Watts Winchester II.
.458 WWII.

 

[Jim Golden]

The SAAMI .458 Lott chamber is 2.810" long, allowing only 0.010" for case stretching on firing.
Better trim it to 2.790". Max brass 2.800".

The .450 Watts Magnum of 1949 first shot has a chamber that is 2.870" long, allowing 0.020" for case stretching, and 2.850" maximum brass length.

SAAMI specifies a minimum chamber length and a maximum brass length.
The reamer maker can make a .458 Lott reamer of greater length than the minimum and call it a .458 Lott, but it is a sloppy job.

In 1971 Jack Lott took a reamer for the .450 Watts Magnum that was designed for re-chambering
a SAAMI .458 WinMag rifle and stole the valor of James Watts by declaring a new cartridge of 0.050" shorter length.
That reamer had a non-cutting belt stop and no throat, it blended into the existing SAAMI .458 WinMag throat.
The SAAMI .458 Lott is shorter throated and cannot perform to has high a level as Jack Lott's "wildcat"
or even the SAAMI .458 Winchester Magnum if it is non-SAAMI-loaded to same COL and higher pressure/MAP of the SAAMI .458 Lott.

Jack Lott's sketch:

View attachment 592743

From a Nick Harvey article, same reamer re-drafted:

View attachment 592744

SAAMI pressure barrel chamber drawings are more directly "readable" for chamber length:

View attachment 592745View attachment 592746


You can load a SAAMI .458 WinMag to longer COL than you can load a SAAMI .458 Lott.

Here is the PT&G reamer of Dave Kiff that matches the SAAMI .458 Lott chamber:

View attachment 592747

Easy to make your own GO and NO GO gages by seating a flat-based .458-caliber bullet backwards into the case. You will find that you need longer ones for the SAAMI .458 WinMag than for the
SAAMI .458 Lott, of course.

Best to use a SAAMI .458 WinMag reamer to re-throat a SAAMI .458 Lott chamber.
I call that the .458 Watts Express.
It is like Jack Lott's first "wildcat" without the extra 0.050" slop in chamber length.
Actually brass of 2.85" is of no benefit over the 2.800" brass.
If I had my druthers for a .375 H&H-length magazine box, I would make the brass 2.700" long,
chamber 2.720" long with a .458 WinMag throat, and call it the .458 Watts Winchester II.
.458 WWII.

Really excellent info here, Riflecrank! Thank you! I copied all of this and sent it to my 'smith.

 

[Riflecrank]

Great !
I bet your gunsmith can give a SAAMI .458 Lott a proper throat if you dare to excel.

 

[AHT081]

A friend of mine recently came back from Africa. He shot a Cape Buffalo with a .375. I asked
him why he didn't shoot his .458 Lott. He said it was just to big and kicked too much. He found
the .375 to be a really good cartridge. These are not my experiences they are my friend's.

 

[86thecat]

Posted by Mule Deer (John Barsness) a few years ago (2011) on campfire. Believe he knows a bit about rifles-

"The tapered throat is quite common, even though parallel throats tend to be more accurate.

The way I understand it, tapered throats evolved with black powder rounds as a way to allow rifles to keep shooting accurately a little longer before powder fouling built up in the throat.

They also served the same function with many smokeless powders that also fouled more than many of today's powders--which was of course complicated by shooters who didn't clean their rifles very often. This is also one of the reasons for the wide-spread belief that even the barrels on smokeless-powder rifles must be brush-cleaned frequently to maintain accuracy.

Tapered throats don't work as well with shorter bullets, or bullets seated very far off the lands. Today the trend is toward parallel throats, in part thanks to cleaner-burning powders."




Posted, same thread by SWARF-

"There is a short article on "throating" in one of the old "Percision Shooting" annuals that Dave Brennen used to put out when he had more submitted than he could publish in the regular magazine. One of the items discussed was by Keith Francis,who was then at JGS the reamer folks still in Oregon. In the article he stated that he had modified the SAMI 458 WM throat in such a manner to eliminate much of its oversized throat to something more sensible, and he maintained it much improved accuracy. When talking to Sarah Humbert at JGS a year or so ago I asked if they still had the "figures" for it. She told me they not only had them, but still stocked it, and called it the 458JGS Mag or something like that."


Would be interesting to know dimensions on 458JGS throat, might work with your Lott.
Would have just linked ro thread, but doesn't seem to work on rhis site.

 

[Jim Golden]

After all this, I'll call my smith. I might just pay the $200 and get a custom reamer made.

 

[86thecat]

If you talk to JGS and get a drawing or a good verbal description of the 458JGS Mag, I am sure it would be of interest to some here.
Hope your build goes smoothly, quickly and turns out great!

 

[Jim Golden]

So I talked with my Smith today and I am going to spend the money and have a custom reamer made. It will be basically a .450 Watts with the case part extended slightly and the throat made to be close to the .458 Win Mag extended 0.3" and a half inch of freebore beyond that. Totally custom .450 Watts / .458 Lott. But it should accept anything from under the seat of a Rover. I'll get carbide, so it'll last. Rent it to you guys if you want to make a duplicate. I want to be able to single load a max length .458 Lott / .450 Watts with a 550 gr with about 1/2" of freebore with .030" over the normal case length just to be sure anything will feed. I'm not shooting this rifle at 500 yards, so if accuracy suffers slightly from the freebore, so be it. At 100 yards or less with open sights it'll be fine with the 26" barrel. Dugga boy Beware

 

[fourfive8]

If it is reamed with care so everything is on axis, I'd almost guarantee you will not have an accuracy issue. A tad of free bore is not a bad thing at all. That actually provides some insurance against high pressure spikes in high temperatures. I used an 8 groove, 14" twist barrel for my 450 Watts. This is a common target and what it's capable of with any good 500 gr bullet, off bench at 50 yards. Both Varget and Benchmark proved to be good powders.

 

[Jim Golden]

Wow! That's one big hole! I'm going to machine my action for scope bases and have a set of Talley's for it. I'll try open sights first and we'll see how bad it is before I try a scope on it I did spend the money and got a nice New England Custom Gun rear sight for it (along with their front ramp).

 

[Jim Golden]

Posted by Mule Deer (John Barsness) a few years ago (2011) on campfire. Believe he knows a bit about rifles-

"The tapered throat is quite common, even though parallel throats tend to be more accurate.

The way I understand it, tapered throats evolved with black powder rounds as a way to allow rifles to keep shooting accurately a little longer before powder fouling built up in the throat.

They also served the same function with many smokeless powders that also fouled more than many of today's powders--which was of course complicated by shooters who didn't clean their rifles very often. This is also one of the reasons for the wide-spread belief that even the barrels on smokeless-powder rifles must be brush-cleaned frequently to maintain accuracy.

Tapered throats don't work as well with shorter bullets, or bullets seated very far off the lands. Today the trend is toward parallel throats, in part thanks to cleaner-burning powders."




Posted, same thread by SWARF-

"There is a short article on "throating" in one of the old "Percision Shooting" annuals that Dave Brennen used to put out when he had more submitted than he could publish in the regular magazine. One of the items discussed was by Keith Francis,who was then at JGS the reamer folks still in Oregon. In the article he stated that he had modified the SAMI 458 WM throat in such a manner to eliminate much of its oversized throat to something more sensible, and he maintained it much improved accuracy. When talking to Sarah Humbert at JGS a year or so ago I asked if they still had the "figures" for it. She told me they not only had them, but still stocked it, and called it the 458JGS Mag or something like that."


Would be interesting to know dimensions on 458JGS throat, might work with your Lott.
Would have just linked ro thread, but doesn't seem to work on rhis site.

I've contacted JGS and requested the drawing. Will let you know what they send me.

 

[86thecat]

Thanks, definitely interested in how they handled the oversize funnel throat of the 458WM.
Have dealt with two 458 WM that hated lighter bullets and gave shotgun patterns with cast bullets. Did find a recipe with one cast bullet and COW filler that gave almost acceptable accuracy in both tho.