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Anyone own a 7mm 300 Win Mag?

 
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  #148  
Old 04-27-2011, 02:48 AM
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Posts: 117
Re: Anyone own a 7mm 300 Win Mag?

I know that 77grn of H1000 is pretty hot for my 7-300 using 180 bergers.

I will measure my cases on my fire formed rounds to see what they are. I did measure them once and though I was right around .513 just above the belt. I had to do this because the cases were sticking in the chamber. Even when I had the load backed way way down.
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Remington 700 SA 22-243 Win
26" SS Benchmark Barrel 1-8 Twist
Glass Bedded-Grey Bull Precision Stock
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  #149  
Old 04-27-2011, 10:11 AM
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Location: California
Posts: 81
Re: Anyone own a 7mm 300 Win Mag?

Thanks, Sid.
I worked up in 1/2g increments CAREFULLY measured, to 78g, because, as in the past w/ most of my Remmies, I could ususally be ok w/ slightly higher than max listed loads. Since all I have to go by is what this thread offers, I was careful in gettin there! No extraction problems, no pressure signs, ie, flat primer, ejector marks etc., and acceptable hunting accuracy for a factory take off bbl. BUT since this chamber is so large, I don't have a reference for head expansion that I go by. Only had problems (knock on wood, so far) w/ the second FF load and H4837sc which MUST be too hot cuz the primers came out! I don't care what the books say, if a primer comes out, SOMETHING is wrong in the mix! Usually it's the powder charge, IMO. But not sure here cuz it's uncharted territory for me.

If your cases come out .513 that would make sense, IF the virgin brass was .510-.511 to begin with. Couple thousandths expansion is acceptable, right?


Quote:
Originally Posted by SidTheKidd View Post
I know that 77grn of H1000 is pretty hot for my 7-300 using 180 bergers.

I will measure my cases on my fire formed rounds to see what they are. I did measure them once and though I was right around .513 just above the belt. I had to do this because the cases were sticking in the chamber. Even when I had the load backed way way down.
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  #150  
Old 04-27-2011, 10:17 AM
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Join Date: Aug 2008
Location: E. TN
Posts: 87
Re: Anyone own a 7mm 300 Win Mag?

I had brass (given to me as once fired) sticking in the chamber too. I got a RCBS small base resize die and that cured it.

I got a 18 twist 7mm barrel this way:
crazy barrel story - Sniper's Hide Forums

I fire formed the brass with the .270 bullets and it all went fine, safe and cases came out good. I was surprised the rifle had some kick to it... the undersized bullets must have been trying to make a gas seal anyway. I learned that in a survival pinch I can shoot .270's through my 7mm.

Per load data I have found I seem to be able to use straight .300WM data for my 7-300.
I just go off the data for the same bullet weight. No I don't just jump into it blindly and load hot- but I have had no problem starting with middle 300WM loads in my
"7mm Win Mag"

Thanks fellas.
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-Tres @ WildernessMeans.com

Check my website for articles, training info, etc!

NOTE: I'm a machinist, gunsmith, writer, and instructor of many outdoor topics looking for gainful employment in any geographical cool place to live. Resumes Available.

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  #151  
Old 04-27-2011, 10:29 AM
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Join Date: Aug 2008
Location: E. TN
Posts: 87
Re: Anyone own a 7mm 300 Win Mag?

Weasel,

When I was just beginning to load for this cartridge I used 7mmRM max loads as a start load for my 7mm-300WM. That never even came close to given me trouble or pressure signs.

No that I have some experience with it under my belt I have found no issue using low to middle loads of the straight 300WM data in my 7mm-300WM with bullets of the same weight.

My MAX loads to date is:
(MY rifle, 30" barrel, tight neck chamber, in cool weather- upper 50's)

!80 grain bullet:
IMR 7828 75.5g 3261fps
H1000 79.4g 3225f/s
Retumbo 81g 3311f/s

As always temps are warmer now & your gun will be different, So drop way back off these charge weights and ease back up in small steps watching for pressure signs.
__________________
-Tres @ WildernessMeans.com

Check my website for articles, training info, etc!

NOTE: I'm a machinist, gunsmith, writer, and instructor of many outdoor topics looking for gainful employment in any geographical cool place to live. Resumes Available.

John 14:6 2TIMothy 3:16
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  #152  
Old 04-27-2011, 10:30 AM
Bronze Member
 
Join Date: Aug 2009
Location: California
Posts: 81
Re: Anyone own a 7mm 300 Win Mag?

Tresmon, I read that Hide article. Good stuff! lol

Ya know, I used the 300WM data as well but got caught w/ my pants down!
IF my chamber has been reamed too large (and I have NO IDEA what specs SHOULD be, but have asked the smith who did the work to check into it for me) then I don't think I'll have a problem rezing them to fit w/ a regular die. Small base would be going in the wrong direction there, it would seem to me. Besides, I neck size only and don't usually FLS until absolutely necessary and then only bumb the shoulder back .002.

Really, the only thing so far that has me spooked is the amount of expansion to to fit the chamber here. I can pay attention to detail all I can, but if it's too big, no telling WHEN a particular piece of brass might let go! Ooopses are not my cup of tea. Thanks for the input. It's valued.
Take care.



Quote:
Originally Posted by tresmon View Post
I had brass (given to me as once fired) sticking in the chamber too. I got a RCBS small base resize die and that cured it.

I got a 18 twist 7mm barrel this way:
crazy barrel story - Sniper's Hide Forums

I fire formed the brass with the .270 bullets and it all went fine, safe and cases came out good. I was surprised the rifle had some kick to it... the undersized bullets must have been trying to make a gas seal anyway. I learned that in a survival pinch I can shoot .270's through my 7mm.

Per load data I have found I seem to be able to use straight .300WM data for my 7-300.
I just go off the data for the same bullet weight. No I don't just jump into it blindly and load hot- but I have had no problem starting with middle 300WM loads in my
"7mm Win Mag"

Thanks fellas.
__________________
Life is short and we ain't gettin out alive!
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  #153  
Old 04-27-2011, 03:20 PM
Silver Member
 
Join Date: Nov 2008
Posts: 117
Re: Anyone own a 7mm 300 Win Mag?

You got those bullets flying out of there!!
Quote:
Originally Posted by tresmon View Post
Weasel,

When I was just beginning to load for this cartridge I used 7mmRM max loads as a start load for my 7mm-300WM. That never even came close to given me trouble or pressure signs.

No that I have some experience with it under my belt I have found no issue using low to middle loads of the straight 300WM data in my 7mm-300WM with bullets of the same weight.

My MAX loads to date is:
(MY rifle, 30" barrel, tight neck chamber, in cool weather- upper 50's)

!80 grain bullet:
IMR 7828 75.5g 3261fps
H1000 79.4g 3225f/s
Retumbo 81g 3311f/s

As always temps are warmer now & your gun will be different, So drop way back off these charge weights and ease back up in small steps watching for pressure signs.
__________________


Remington 700 SA 22-243 Win
26" SS Benchmark Barrel 1-8 Twist
Glass Bedded-Grey Bull Precision Stock
Built by Hazer@Bison Barrels in Gillette,WY
Sightron SIII 6.5-24X50MM LRMOA
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  #154  
Old 04-27-2011, 03:25 PM
Silver Member
 
Join Date: Nov 2008
Posts: 117
Re: Anyone own a 7mm 300 Win Mag?

Just measured the brass and it was was about .512 just above the belt. This was brass that has been fireformed in my rifle. Most were right there.

Quote:
Originally Posted by Weaselthis View Post
Thanks, Sid.
I worked up in 1/2g increments CAREFULLY measured, to 78g, because, as in the past w/ most of my Remmies, I could ususally be ok w/ slightly higher than max listed loads. Since all I have to go by is what this thread offers, I was careful in gettin there! No extraction problems, no pressure signs, ie, flat primer, ejector marks etc., and acceptable hunting accuracy for a factory take off bbl. BUT since this chamber is so large, I don't have a reference for head expansion that I go by. Only had problems (knock on wood, so far) w/ the second FF load and H4837sc which MUST be too hot cuz the primers came out! I don't care what the books say, if a primer comes out, SOMETHING is wrong in the mix! Usually it's the powder charge, IMO. But not sure here cuz it's uncharted territory for me.

If your cases come out .513 that would make sense, IF the virgin brass was .510-.511 to begin with. Couple thousandths expansion is acceptable, right?
__________________


Remington 700 SA 22-243 Win
26" SS Benchmark Barrel 1-8 Twist
Glass Bedded-Grey Bull Precision Stock
Built by Hazer@Bison Barrels in Gillette,WY
Sightron SIII 6.5-24X50MM LRMOA

Last edited by SidTheKidd; 04-27-2011 at 05:05 PM.
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