7BRAW re-Visit

[ktm571]

Hi. Searched a bit but this topic seemed to pop up and fade a couple of years back.

I'd be interested in a 7-08 with a standard or 25 degree shoulder and .200/.230-ish FB with std 1.5 degree throat. I've looked long and hard at the WTO 7 SAW but I'm too chicken to put $1000 worth of barrel blank + chambering at risk with their stepped throat in 1k benchrest. That throat design presumably helps with speed and they intend it for PRS. I'm not sure how erosion of the straight step in that throat would affect accuracy for benchrest over the life of a barrel.

Anyone try a 7 SAW for benchrest? Or know where Alex W left the 7BRAW topic? Thx.

 

[ballisticdaddy]

I run a 7SAW for hunting and NRL hunter matches but it's a bit much for PRS imo. Curently running the Hornady 162 grain ELD-M at 2,788 fps and Sierra 150 grain TGK at 2,755 fps with Alpha brass. I shot f-class 1,000 yard for years and if you are looking at a 7mm why not just use the tried and true .284 Win?

 

[ktm571]

Hi. Searched a bit but this topic seemed to pop up and fade a couple of years back.

I'd be interested in a 7-08 with a standard or 25 degree shoulder and .200/.230-ish FB with std 1.5 degree throat. I've looked long and hard at the WTO 7 SAW but I'm too chicken to put $1000 worth of barrel blank + chambering at risk with their stepped throat in 1k benchrest. That throat design presumably helps with speed and they intend it for PRS. I'm not sure how erosion of the straight step in that throat would affect accuracy for benchrest over the life of a barrel.

Anyone try a 7 SAW for benchrest? Or know where Alex W left the 7BRAW topic? Thx.

Recoil & muzzle blast simply. I have a 284 now. A properly throated 7-08 with a 180 HT ought to be within 100 fps or so of a 284 using 8-10gn less powder. My particular matches are about 65-70 rds with a 17lb gun and lighting off that many rounds with a 284 on a Sunday just isn't fun.

 

[ballisticdaddy]

Recoil & muzzle blast simply. I have a 284 now. A properly throated 7-08 with a 180 HT ought to be within 100 fps or so of a 284 using 8-10gn less powder. My particular matches are about 65-70 rds with a 17lb gun and lighting off that many rounds with a 284 on a Sunday just isn't fun.

If you push a 180 grain projectile within 100 fps of a .284 I would venture to say it would have VERY similar recoil and muzzle blast. I shoot my 7SAW suppressed as neither the recoil nor muzzle blast are enjoyable!

 

[DHuffman]

7-08 40° improved is competive running 180s in 600 & 1000 in BR
Will run 2700 without wrecking brass and recoil in a 17#:gun is mild IMO

 

[std7mag]

Your gonna laugh. Shake your head. And just flat out think I'm crazy.

My first 600 yard F-Open match, I shot my Stevens 200 with the 22" sporter barrel that I reamed to 7mm-08AI (7mm-08 Imp 40°).
It was the last horrah on the barrel as I had put about 6,000 rounds through it. (Yes, you read that correctly)
So rifle with an Atlas knock off bipod, Sightron STAC 4-20X56 weighed in about 8lbs.

For cartridge I was using PPU brass.
Alliant PP2000MR powder.
Fed 210M primer.
140gr Berger VLDH at 2.898" COAL (Reamer has a 0.06" FB)
Velocity 2,832fps with ES-6, SD-2 run over (2) ten shot strings.

Muzzle blast wasn't bad.
But after the second string of 20 rounds recoil was getting to me.
By the end of the third string, I was hurting!

I think a 17lb gun, throated for the 160-168gr class of bullets, the 7mm-08AI would probably shine.

 

[mike mccormick]

Or....and I know it sounds crazy.....you could just throttle back on the 284, find a lower accuracy node, and achieve your goal.

 

[Fire Dog]

Your gonna laugh. Shake your head. And just flat out think I'm crazy.

My first 600 yard F-Open match, I shot my Stevens 200 with the 22" sporter barrel that I reamed to 7mm-08AI (7mm-08 Imp 40°).
It was the last horrah on the barrel as I had put about 6,000 rounds through it. (Yes, you read that correctly)
So rifle with an Atlas knock off bipod, Sightron STAC 4-20X56 weighed in about 8lbs.

For cartridge I was using PPU brass.
Alliant PP2000MR powder.
Fed 210M primer.
140gr Berger VLDH at 2.898" COAL (Reamer has a 0.06" FB)
Velocity 2,832fps with ES-6, SD-2 run over (2) ten shot strings.

Muzzle blast wasn't bad.
But after the second string of 20 rounds recoil was getting to me.
By the end of the third string, I was hurting!

I think a 17lb gun, throated for the 160-168gr class of bullets, the 7mm-08AI would probably shine.

Mass x Velocity is going to equal the same amount of recoil impulse no matter what cartridge is used… 180gr x 2,800+fps
The heavier gun will soak up the felt recoil effects and adding a RAD system will make your shoulder thank you following a long string match.

 

[ktm571]

Mass x Velocity is going to equal the same amount of recoil impulse no matter what cartridge is used… 180gr x 2,800+fps
The heavier gun will soak up the felt recoil effects and adding a RAD system will make your shoulder thank you following a long string match.

Thx guys. Ya, it's Mass x Velocity squared . So yes, muzzle velocity of a 180 at 2700 is only 7-8% less than 2800. There is the muzzle blast factor too using 8-10 grains less powder. And in theory better barrel life comes along for the ride.

I'll look into the RAD system as well. I shoot for fun. Will never be a Nat'l Champ. The 284 isn't fun right now at that many rounds. Wouldn't be as bad for 1-2 relays at Williamsport on a Saturday.

 

[ktm571]

Thx guys. Ya, it's Mass x Velocity squared . So yes, muzzle velocity of a 180 at 2700 is only 7-8% less than 2800. There is the muzzle blast factor too using 8-10 grains less powder. And in theory better barrel life comes along for the ride.

I'll look into the RAD system as well. I shoot for fun. Will never be a Nat'l Champ. The 284 isn't fun right now at that many rounds. Wouldn't be as bad for 1-2 relays at Williamsport on a Saturday.

Muzzle energy that is...

 

[std7mag]

Mass x Velocity is going to equal the same amount of recoil impulse no matter what cartridge is used… 180gr x 2,800+fps
The heavier gun will soak up the felt recoil effects and adding a RAD system will make your shoulder thank you following a long string match.

That's the kicker, so to speak.
I was shooting a 22" barrel with a 140gr bullet at 2,832fps. But from an 8ish lb rifle.

My wife's Savage 111FP with the 24" heavy varmint barrel and a Choate stock puts it right at 14lbs.

Even with a longer barrel, I'm not sure that the 7mm-08, AI, or SAW would have enough case volume to push a 180gr bullet to the 2,800fps range.
I could be wrong, but I think if you were able to, it would be hard on the cases.

 

[Fire Dog]

That's the kicker, so to speak.
I was shooting a 22" barrel with a 140gr bullet at 2,832fps. But from an 8ish lb rifle.

My wife's Savage 111FP with the 24" heavy varmint barrel and a Choate stock puts it right at 14lbs.

Even with a longer barrel, I'm not sure that the 7mm-08, AI, or SAW would have enough case volume to push a 180gr bullet to the 2,800fps range.
I could be wrong, but I think if you were able to, it would be hard on the cases.

I think you are right as I am using 180’s & 184’s in a 280AI {basically a 7mm-30-06} and to get them moving at 2’800fps requires 56.7gr of 4831sc and the 308 case of the 7-08 just may not have enough capacity but some other powders may be a bit less volume and able to produce that velocity… As always advised, go slowly and with caution as you approach maximum loads.