switch barrel rifle build

[Buano]

I'm in the design process of building an antelope/mule deer/elk rifle. It will be on a Rem 700 action. I do a lot of backpack hunting so weight is at a premium.

Here are some of the specs currently:
- calibers are: 340 Weatherby and 7 mm RUM (possibly 7 mm Weatherby)
- stock - Lone Wolf Monte Carlo - weight about 2 pounds
- bottom metal - PT&G aluminum 2.4 ounces
- barrels Pac-Nor - 22" but not sure about the contour...either a lightweight
unfluted (2.3 pounds) or a #1 fluted (2.3 pounds)
- bolt work...alum firing pin, alum bolt shroud, fluted, lightweight bolt handle.

Some questions I have:
1) would anyone be willing to flute an lightweight barrel? I could drop the weight another 8 ounces.
2) any other ways to cut weight?
3) recommendations for a good lightweight scope and scope rings?
4) any other issues I might be missing?
5) Other caliber recommendations?

Thanks in advance,
Scott

Some thoughts:

• A 22" barrel will waste much of the long-range potential of the rounds you are looking at. You may as well stay with a .338 win mag instead of the Weatherby if you don't care about the velocity. If you don't want the weight of the longer barrel, go to carbon wrapped barrel to save more weight than the short barrel while maintaining bullet velocity.

• If you are going with a .340 Weatherby for your "big" barrel, a 7mm-.300 Weatherby would have the same case and feed exactly the same. Obviously, a 7mm-.300 Weatherby only works if you are a reloader.

• You could save weight by going to a shorter action & use .270 (or 7mm) WSM & .325 WSM.

• No one beats the Talley Lightweight Alloy Scope Mount (talleymanufacturing.com). They are light, they look good, & they work well — & two of our rifles wear them.

• If you are going ultra-light I presume you would be adding a muzzle brake. At least I HOPE you will add a brake!

• As one of your reasons for a switch-barrel gun was so you would only need buy 1 scope, any of the quality quick-detach scope mounts let you swap scopes instantly between different guns. Talley makes the best QD mounts made.

• If I was looking at 1 gun to do all these jobs, it would be a .300 Weatherby, and likely a stock Accumark. There are lighter guns, but I will carry a little extra weight to get "shootability".

•*As you already have a 7mm SPS, I would buy a .340 Accumark & hang on to the 7mm.

 

[sanjuanfly]

Buano thanks for the input. I like the idea of the 7mm-300 weatherby (sounds like a pretty hot round). Would a 338 RUM and 7 mm RUM be in the same situation where they would feed exactly the same?

My new barrel lengths will be 24-26 inches. From some of internet searchs, seem like a 340 only loses 15 - 20 fps per inch at these lengths.

Also the idea of an ultra-light weight big bore rifle is not going to happen. I think I can still have a great LR gun come in under 7.5 unscoped (8.5 to 9 pounds scoped).

 

[Buano]

Buano thanks for the input. I like the idea of the 7mm-300 weatherby (sounds like a pretty hot round). Would a 338 RUM and 7 mm RUM be in the same situation where they would feed exactly the same?

My new barrel lengths will be 24-26 inches. From some of internet searchs, seem like a 340 only loses 15 - 20 fps per inch at these lengths.

Also the idea of an ultra-light weight big bore rifle is not going to happen. I think I can still have a great LR gun come in under 7.5 unscoped (8.5 to 9 pounds scoped).

Yes, the 7mm-.300 Weatherby sounds HOT. I've never had one, and if the 7mm RUM weren't a standard loading, I would think hard about that cartridge.

Yes, any of the RUM shells should feed the same, so a switch-barrel with 2 RUM calibers should have no feeding issues. Not that I would want to switch-barrel a RUM!

I still think you would be best off with 2 rifles. Keep your 7mm & lighten/accurize it when you get time & money. Buy a .340 Weatherby & have a great gun.

 

[sanjuanfly]

I still think you would be best off with 2 rifles. Keep your 7mm & lighten/accurize it when you get time & money. Buy a .340 Weatherby & have a great gun.

I'm really starting to think that 2 rifles are the answer.

 

[sp6x6]

Have both 7mm,340, problem is my 16 yr old keeps taking my 340. Solution , my new speedgoat,deer,elk hammer,338 NORMA. 26",Defiance,Lonewolf 7-2oz,8-12 oz w/M4 6-20

 

[Buano]

I'm really starting to think that 2 rifles are the answer.

Switch barrel guns are always a possibility but there will always be trade-offs that I don't want. You can make a 7mm quite light & still be able to shoot it fairly well, the same can't be said for anything in the .340 Weatherby class. The big shells require a fair amount of mass in the rifle to tame the recoil — even with a muzzle brake. If you make a switch-barrel for these 2 cartridges, it will likely be heavier than you want for your 7 mm backpack rifle.

With 2 rifles you have a back-up that can be ready to go if something happens to the gun you were hunting with. This can save an expensive hunt.

 

[MontanaRifleman]

I'm really starting to think that 2 rifles are the answer.

I think trying to combine a big 338 with a light weight pack gun is a bit too much. You might combing a small cal varmint barrel like .25 with a larger cal hunting such as a 7mm or 30 cal.

If and when I do a switch barrel, it will be based on seasonal needs and I might just do that if my smith is OK with it. It would be a 300-375 Ruger for big game, deer, elk and bear in the fall and spring for spring bear. Then after spring bear, put the 6.5-375 Ruger barrel on for varmints and speedgoats, then right after speed goats, back to the 300-375 for big game again.

The advantages I see are... save cost on stock & action and associated smithing and base, rings and scope. The disadvantage is having to re-sight which is no big deal and not having a particular cal to shoot for about half the year, again no big deal

I agree with Buano, that having a backup rifle is a good idea. In my case I have backups, so to get a swithbarrel would save me about 50-70% the cost of a new rifle depending on what scope I used.

 

[sanjuanfly]

I've given up on having a ultra-light 338, but I think I will stay with the switch barrel. Between my dad and I we have numerous back up rifles (270 weatherby, 30-06, 300 weatherby, 340 weatherby, 308, etc.). The main problem with a two rifle solution for me is I was getting away from the custom gun, which was my first reason for doing the build.

So here are my current plans:
- 338 RUM and 7 mm RUM (I will buy a couple hundred extra brass in each caliber just in case
- barrels will be Pac-Nor 25" #3 contour fluted with a Gentry Quiet muzzle break. I was really trying to stay away from a muzzle break, but lighter kicking rifles are ALWAYS good.
- Lone Wolf Monte Carlo...not sure I will pay extra for the 100% carbon or stay with the carbon/kevlar
- scope TBD

A questions I have:
1) Would these calibers work out of my 7mm Rem Mag 700 long action without modification?
2) Should I give Pac-Nor any special instructions on the barrels? I don't handload right now, but will start when this build is complete.


I appreciate everyone's feedback.

Thanks,
Scott

 

[sanjuanfly]

Since I'm likely going with muzzle breaks, what are people's thoughts on the 375 RUM?

 

[MontanaRifleman]

I've given up on having a ultra-light 338, but I think I will stay with the switch barrel. Between my dad and I we have numerous back up rifles (270 weatherby, 30-06, 300 weatherby, 340 weatherby, 308, etc.). The main problem with a two rifle solution for me is I was getting away from the custom gun, which was my first reason for doing the build.

So here are my current plans:
- 338 RUM and 7 mm RUM (I will buy a couple hundred extra brass in each caliber just in case
- barrels will be Pac-Nor 25" #3 contour fluted with a Gentry Quiet muzzle break. I was really trying to stay away from a muzzle break, but lighter kicking rifles are ALWAYS good.
- Lone Wolf Monte Carlo...not sure I will pay extra for the 100% carbon or stay with the carbon/kevlar
- scope TBD

A questions I have:
1) Would these calibers work out of my 7mm Rem Mag 700 long action without modification?
2) Should I give Pac-Nor any special instructions on the barrels? I don't handload right now, but will start when this build is complete.


I appreciate everyone's feedback.

Thanks,
Scott

Based om my experience with the 300 RUM, if you want seat the longer high BC bullets, you will need to lengthen the mag box unless you use the method of just putting one down so the nose is above the mag wall. What you need to do is get the brass and the bullets you want to use and seat them where you want them seated for the smith to chamber and throat the barrel to the correct depth and determine how long a box you need. You can always seat the bullet deeper into the case to shorten your COAL.

I'm guessing you'll lose about 50 fps with the 25" vs 26" barrel. Some ways to maximise your efficiency and velocity would be to..

- Use slightly faster powders like H4831sc or H1000 vs Retumbo

- Get a 5C rifled bore - there seems to be a fair amount of evidence that the 5C or 5R rifled bored are about 30 fps or so faster than non-canted rifling.

- Nitride your barrel - a fairly new process that appearrs to lengthen barrel life by 2-4x. It also give s you a little better velocity. Sources I've talked to and read show about 1-3% increase in velocity.

The 7RM has an identical base diameter as the 7RUM and the 338 RUM is .002 larger, I don't think it should be an issue but let the smith decide that.

A question for you, what experience do you have with the Gentry Quiet Brake? And just how "quiet" are they?

 

[MontanaRifleman]

Since I'm likely going with muzzle breaks, what are people's thoughts on the 375 RUM?

I think you'll get better perfomance from the 338 RUM. If you want to throw 375's go to the Chey Tac. The high BC 375's will also be extremely long - not sure if you could even chamber them single shot?

 

[sanjuanfly]

I just searched some recoil tables of the 375 RUM...even with a brake they will kick pretty hard. So 338 RUM is it.

As for the "Quiet" brake, I don't have any experiece with it or any muzzle brake. I think there are some good titanium brakes out there. Any recommendations would be appreciated.

Do you know who does the Nitride barrel treatments? And how much do they cost?

5c was the way I was going to go. Need to make sure Pac-Nor offers it.

 

[MontanaRifleman]

Benchmark does Nitriding and this guy...

YouTube - Salt-Bath Nitriding for Rifle Barrels -- Joel Kendrick Interview

This would definitely be a big plus for the 7RUM as it is well known to be a barrel burner.

Salt-Bath Nitriding for Barrels — Whidden is Impressed « Daily Bulletin

 

[sp6x6]

Speaking of light weight, I looked at a 4-13oz, 338 win at Lonewolf a few weeks back, should have asked about the smith