Long barrel 7stw

[hemiford]

Good Morning All

I seek some guidance on this rifle build. I have a 36-inch Benchmark barrel blank, 9-inch twist, 5-groove.
Rifle weight will not be a consideration.
I plan to shoot Berger 175-gr Elite Hunter (I'm counting on them being available at some point).
I don't have a chronograph yet, but I will get one when I figure out which one to buy.
I've read more bad than good it seems about chronos.

Looking for powder advice. I have 7828SSC right now and I'm getting some VV-N570.
I suspect the long barrel throws a curve ball in the powder selection, do I want a super slow powder
for best velocity ? I'd be willing to try a different powder than the above two.

The barrel is not chambered yet, I'm not against getting a custom reamer and altering the SAMMI specs a bit.
I want it all, velocity and accuracy.
This is a special project to me and I want to go the extra mile building it.

I'm even thinking about Hex-BN coating down the road, but not at first (first load development).

Thanks much !

 

[ultraedge]

delete please

 

[ultraedge]

I have used 30" and 31.5 " barrels. The 30" was faster. Retumbo powder worked great with 150, 162, and 180 grain bullets.

 

[MagnumManiac]

I suspect the long barrel throws a curve ball in the powder selection, do I want a super slow powder
for best velocity

The barrel is not chambered yet, I'm not against getting a custom reamer and altering the SAMMI specs a bit.

I run 32" barrels in my comp rifles for 1000 metre F-class, 30" for 600 metre F-class and 28" for all other shorter distances. None use a different powder because of length. It makes zero difference.
My own 7STW is a re-chambered factory Sendero 7RM barrel I did myself.
The only custom issue you may want is a custom throat, mine was altered to run 175g ABLR and 168g ABLR, both run right at 3.655" to fit my mag box, this rifle is a trued/blueprinted REM 700 Sendero switch barrel, other barrel is a 264WM 1:8" twist, custom chamber and throat at 29.5". Runs 142g ABLR above 3300fps.
I don't think other changes to the chamber are required, unless you have a mag box suitable for 3.850" or longer cartridge OAL. This is my goal, but haven't ordered the Wyatt's box yet.
As to chrono use, I have an Shooter Chrony, the Beta model, and find overcast days are best, also you MUST level the chrono so the bullets are going over it flat, otherwise you get erroneous results.
I use HBN on my 300WM comp rifles, not for hunting, and I coat my 338-416 Rigby Improved 45° custom bullets to reduce in-bore friction.

Cheers.

 

[yobuck]

I have two 7x300 Wetherbys, both 9 twist, one has a 30" barrel and one a 26.5" barrel.
Using 7828 powder and 162 gr bullets they both produce the same velocity within a couple fps.
The 7x300 Wetherby and the 7 mm STW are pretty much clones from a performance standpoint.

 

[yobuck]

I run 32" barrels in my comp rifles for 1000 metre F-class, 30" for 600 metre F-class and 28" for all other shorter distances. None use a different powder because of length. It makes zero difference.
My own 7STW is a re-chambered factory Sendero 7RM barrel I did myself.
The only custom issue you may want is a custom throat, mine was altered to run 175g ABLR and 168g ABLR, both run right at 3.655" to fit my mag box, this rifle is a trued/blueprinted REM 700 Sendero switch barrel, other barrel is a 264WM 1:8" twist, custom chamber and throat at 29.5". Runs 142g ABLR above 3300fps.
I don't think other changes to the chamber are required, unless you have a mag box suitable for 3.850" or longer cartridge OAL. This is my goal, but haven't ordered the Wyatt's box yet.
As to chrono use, I have an Shooter Chrony, the Beta model, and find overcast days are best, also you MUST level the chrono so the bullets are going over it flat, otherwise you get erroneous results.
I use HBN on my 300WM comp rifles, not for hunting, and I coat my 338-416 Rigby Improved 45° custom bullets to reduce in-bore friction.

Cheers.

My brother in law has a standard 338x416 with a 36" barrel, and his velocity with a 300 gr is 3050 fps using H50bmg powder.
Another guy i know has the improved version, and he claims 3200fps plus.
Bruce Baer built both guns, and when i discussed this with him he just said no he dosent, and if he did he would simply throw the case away when he removed it.
Id be curious about your experience with yours.

 

[Barehandlineman11]

Idk my 37xc with h1000 is 3000 with 34" barrel 390 a tip. 33xc with h50 and 30" will only do 3150 with a 300 itll do 3250 with n570. So 338/416 be super unrealistic to get 3200 out of it. As of 7stw and 175 id run h1000 no matter the tube. If you got it or can retumbo would be ideal.

 

[hemiford]

Thanks guys, I guess I need to find some H1000 and some Retumbo, to try at least.
Break out the wallet. Can't find the Reloders either. And the Enduron powders 7977
and 8133 are discontinued.

 

[Barehandlineman11]

N560 is around same burn rate too just dirty

 

[MagnumManiac]

My brother in law has a standard 338x416 with a 36" barrel, and his velocity with a 300 gr is 3050 fps using H50bmg powder.
Another guy i know has the improved version, and he claims 3200fps plus.
Bruce Baer built both guns, and when i discussed this with him he just said no he dosent, and if he did he would simply throw the case away when he removed it.
Id be curious about your experience with yours.

I have discussed this with you before, my +P throat, 45° Improved chamber and use of HBN makes this cartridge shoot my 323g solid copper bullet well above 3200fps, but I do not shoot it at that velocity regularly.
The regular bullets without relief grooves that I have used would top out at 3200fps in the 300g weight range.

Cheers.