7mm STW, Velocity vs Barrel Life

[osteodoc08]

My late father had a 7mm STW built on a mauser action and I'm looking to take it out and making a bench gun out of it. It has a reputable barrel (I forget the brand McGowen or Lilja or ???) on it and I'd like it to last as long as possible. At what velocity do we really start to see barrel life suffer?

My plan is to shoot the heavy for caliber loads and try to keep velocity under 3000fps and use it out to 600-800 yds as a target gun. All the hunting I do here in GA, this would be WAY overkill. Some of the 160-180gr offerings have some very impressive B.C. numbers.

Also, a huge thank you to C. Latch for landing me on 1x fired 7mm STW brass for an awesome price.

So......velocity vs barrel life. What is the threshhold if any?

[DR Owl Creek]

I don't have a 7mm STW, but I do have other magnum bolt action rifles. I would suggest shooting at a slow enough pace that you don't get the barrel really hot, and you should have decent barrel life. Even if you have to eventually have it rebarreled, so what? People put new tires on their cars and trucks all the time, and it's not the end of the world.

Enjoy shooting your Father's rifle!

Dave

[Larry Gibson]

300 Win Mag sniper rifles and match rifles are most often rebarreled between 1000 and 1500 rounds. Given how much more over bore the 7 STW is I would suggest not wasting a lot of barrel life "working up a load" to get that last bit of .001 less group. I've carefully tracked the round count on several long range match rifles of 6.5-06, 6.5-284, a .280 Rem, and a 7mm Rem Magnum. They all lost match winning capable accuracy (1/2 moa) around 1200 - 1500 rounds and held 1 - 1 1/2 moa to close to 2000 rounds. All rounds fired were with the heavier MKs and appropriate for the case/cartridge powders. A 22- 284 I was involved with once was totally shot out in less than 800 shots. If you want to dance you have to pay the band. Some match shooters rebarrel at 1000 rounds "just because". They have a standard load for the cartridge that takes little, if any, tweaking. The simply zero and test the new barrel with the standard load. If it shoots they use it in matches and don't waste a lot of barrel working up loads.

Larry Gibson

[Mk42gunner]

Once again, what Larry says makes a lot of sense to me. To paraphrase, try a few loads then pick one and stick with it.

If it was me, I think I would start with the heaviest Sierra Match King and the slowest powder I could get several pounds of.

Good luck and have fun with it. I know I always enjoy shooting my Dad and Grandpa's guns, it brings back a lot of memories.

Robert

[Love Life]

Heat and pressure.

[osteodoc08]

Thanks for the responses, esp Larry. Any suggestions for powder? I think dad used 7828, but I'll have to see what we have locally. I think the 50BMG powder was on the shelf last time. A number of the Reloaders as well. Suggestions?

[pjames32]

I use 8700 at the high end with 160-175 Sierra. That's the best accuracy. My gun has 800-900 rounds and has not lost accuracy, yet!
PJ

[JeffinNZ]

If it is a hunting rifle don't worry about it. He'll likely never put that much ammo down the tube.

A lot of over bore cartridges get/got a bad rap because they burn out barrels but the reality was the average owner being a hunter need never worry about it.

[MBTcustom]

Given what you have said in this thread, I'd say you're going to start noticing your groups open up at about 1000-1200 rounds. I am a riflesmith and I see alot of this sort of thing. The things that burn barrels fastest are:
Overbore cartridges
Heavy bullets
Fast twist
Slow powders
and high pressure.
I don't think running your barrel hot or cold makes a huge difference. This is a combination of gas heat and pressure in the barrel during the firing event, and that heat compared to the temperature of the barrel is so great that 50 degree differences in barrel temperature doesn't mean a whole lot.
Fact is, you've got about 1000 shots on your debit card. What are you going to buy with it?

Another thing that you should really take into consideration is the twist rate recommended for shooting those long javelins. Call the bullet manufacturer and ask them what the ideal twist rate is, and then check your barrel. If your twist isn't fast enough to really stabilize your bullet, you are not going to be able to use that high BC because you are not able to stabilize the long bullet.

A word on BC: Don't get too wrapped around the axle with this. High BC does not an excellent bullet make!
Also, the BC is set according to a very specific set of parameters that your rifle and cartridge may or may not realize. Larry Gibson can speak much better to this subject, but suffice it to say that I have come to regard BC like IBO speeds on compound bows. It's always given as the highest number they think they can get away with because the stated BC helps the product sell, whether it's right for your rifle or not! True marksman match the bullet to the rifle and twist first and foremost, and try to use the best flying design they can within those parameters (if that makes any sense). A good recipe for success (and how I proof test accuracy in the custom rifles I create) is to get a nice boat tail bullet from Seirra or Hornady that is optimized for the twist rate of the rifle. Load up some ammo according to the accuracy load in the manual you use. If the rifle doesn't shoot sub MOA with that combo, then there is something wrong with the rifle. This is how I choose loads for testing custom rifles, and I don't have time to be trying three powders and three bullets etc etc etc. I need accuracy and I need it quick, so I follow that procedure and turn the crank. Works every time.

Please keep me in mind if you do burn that barrel out and need a new one. I change barrels all the time for people on the forum here, and I can put you right back to square one if you burn out the barrel.

[gray wolf]

IMHO -- I think you will notice throat erosion before the actual barrel gives it up.

[Larry Gibson]

Thanks for the responses, esp Larry. Any suggestions for powder? I think dad used 7828, but I'll have to see what we have locally. I think the 50BMG powder was on the shelf last time. A number of the Reloaders as well. Suggestions?

With the heavier 7mm match bullets (175 - 200 gr) 7828, RL25, Retumbo, H50BMG, AA8700 and H870 are the powders I would look for. The fastest I would use would be RL22.

Larry Gibson

[MT Chambers]

I'm thinking that is a long range hunting cal., not a BR cal., most folks shoot it once or twice to check zero and then go hunting, never heating the barrel up. I know a lot of people want flat trajectory for long range target work, but I'm thinking that there may throat erosion before you work up a good load.

[Larry Gibson]

OP states; "I'm looking to take it out and making a bench gun out of it..........My plan is to shoot the heavy for caliber loads and try to keep velocity under 3000fps and use it out to 600-800 yds as a target gun."

Probably no need to get the barrel hot at all unless in target competition where there is a time limit for so many shots to be fired in. An example would be where 1 shot per minute is allowed and a 10, 15 or 20 shot string will heat the barrel.

None the less the rifle probably has a match level accuracy life of 1000 - 1500 rounds. With some that can be less than one season of shooting. With others it can last 10+ years. Depends on how much the OP is going to shoot it.

Larry Gibson

[fredj338]

Heat and pressure.

^^THIS^^ It's not so much vel but heat & pressure. Large charges of slow powder create a lot of heat over a longer duration. Over bore rounds like the 7STW are going to burn barrels if you run the top end, no way around it. The throat is going to go, in as little as 2000rds of full power ammo. You can of course have the barrel turned down & rechambered to get some more miles out of it.

[Love Life]

Barrels are consumables. I'd pick a different caliber for target shooting and range funning, but you run what you brung!!

[JeffinNZ]

On 6mmbr.com a while back someone calculated the life of a BR barrel to be SIX seconds.

[osteodoc08]

Picked up some RL25. Hope to get started shooting this by early spring. I'll check twist when I have a chance and get appropriate weight bullets. Will keep everyone posted.

[Motor]

I use H-870 for the one I load for using 175gr bullets. I'd say if you stay in the 160 to 175 range you will get the most out of it.

If you start pushing 120s or 139/140s to max velocity you will see it ware quickly.

Motor

[BST4227]

I had a 7MMSTW built in 91 when I was stationed in Colorado Springs (Ft Carson) the gunsmith said I would most likely have to replace it somewhere near 1500 rounds depended on what I shoot and how I shoot it. So far I have around 800 rounds through it mostly 160g Noslers and Barnes with a few 120s now and then. Mostly I have used 7828 or RL22 powders, I have yet to see any major decrease in accuracy.