Gunsmithing Need some tips for a 700RUM action.

[ShooterwithNoName]

So I bought a new 700RUM action a while back. It's a stripped carbon steel version. I'm getting ready to start purchasing the parts for the build and I'm hoping to get some insight from those who know more about building these. My plan is to build a heavy rifle to squeeze all the velocity I can out of it. A dedicated long range rig that can handle the heaviest for caliber bullets. I'm having trouble settling on a chamber.

I have been planning a 338RUM to shoot the heavier 250g, 285g and single fed 300g. I want it to be a repeater. Since it will be mag fed for most of the rounds I'll be shooting I stayed away from the 338Edge due to its extra length. From research I've read that you can fit some Edge loads in a 3.775" mag but they are so tight that they often hammer the bullets around in the case. Which is why I decided to go with the standard 338RUM with its shorter case length. I had initially planned a 338LM build but decided to save that for a better suited action. I had thought about going with a 300RUM but prefer the 338 bullet weights. I want above all else for this rifle to be as reliable and tough as possible as it will be drug around on hunts. I know it will be heavy, I've drug around a Zastava M808 with heavy ass wood thumbhole stock and massive 26" barrel and it's been my go to rifle I've learned to shoot longer distances with. But it's chambered in 30-06 and I've reached its limits. I plan on keeping this 338 build in the same weight class as my M808.

Here's my list so far for the build.

- Remy 700 UM receiver
- PTG dual ejector LA bolt, M16 extractor
- McGowen #7 338RUM 1:9 28" Remage
- HS Precision PSS take off
- PTG Stealth CIP bottom metal
- Timney 510 Trigger
- Tubb Speedlock firing pin assy

As you can see, this is a budget build. As much as I admire the amazing rifles you guys build here, a lot of them are WAY out of my price range. I have to build something here as fiscally responsible as possible while not compromising quality. This rifle will, for lack of better terms, be a beater. I'm not trying to build a beautiful Ferrari, I'm trying to build a primered 72 Nova that'll run. I want to use this rifle to learn how to shoot at distances past 800yds. I want to not cringe at the thought of dragging it through the brush, putting it in the dirt and shooting it regularly in places other than a bench. My concerns are more about reliability. Such as:

The Tubb Speedlock firing pin assy, have these proven to be reliable or would I be better served with a factory firing pin assy? Do you guys recommend the dual ejector setup for the RUM case? I'm planning on the Stealth BM so I can run Accurate Mags set up for the 338RUM. Are the Accurate Mags pretty reliable? I'm open to any recommendations you guys have. I know the HS stock is probably not the top choice, but they can usually be found pretty cheap second hand and I've had good luck with them in the past. The barrel will be threaded 5/8-24 So I can use an FTE brake. I went 28" so I can wring all the velocity I can out of the RUM. I know that's a heavy, cumbersome barrel to pack around but I have managed one before on a 7mmMag so I know what I'm going to be dealing with. I'll have fun getting used to it this fall. I plan on single loading the 300g loads while hoping to find an accurate 285gr load I can fit in the 3.775" mag without beating the bullets back in the mag. I usually pack the mags out of the rifle until I'm in position anyway.

Thanks for reading, I'm gonna use this as my build thread as time goes on.

 

[B y r o n]

When I built my rifle there weren't any ready to use magazines at least that I was aware of. It too is a .338 RUM I had built on a stainless action. Here is what Randy Cain at R&D Precision assembled for me.

Now this is with factory bottom metal, It actually got dropped into an AICS stock when I could afford it. The problem was the .338 RUM rounds would not fit in the .338 Lapua magazines. The problem was shoulder hit the front rib of the magazine. I had to have the magazines milled. This is what was done:

Once that was done it worked like a charm. The RUM shoulder just sits further forward than the Lapua.

You may have also noticed the muzzle brake. It's a Badger Thruster and believe me it makes the rifle SO MUCH better to shoot. Between the weight of the rifle and the brake it doesn't recoil any harder than a .308 or maybe a .30-06 and that is with the 300 grain Sierra's.

I can't help with much more because I didn't have a barrel nut to contend with but I felt you might need to know about the magazine issue.

 

[Bandit31]

Out of curiosity, why the RUM and not something like a 300m or 7 rem mag?

I'd exxpect to spend a little extra money to have the PTG bolt fitted and the scope base screws aligned and opened up to the 8-40 to hold everything down with the recoil from the magnum.

I'd also compare the costs to a custom action if you can find something that'll work for you. You may not be far off from a price difference when all is said and done.

I say no on the speed lock and spend the savings on a different/ better trigger like a triggertech.

Look at the KRG Bravo chassis. Already set up for large recoil lugs, cip mags, and has more options, especially with adjustability. Would probably cost the same as a pss and the dbm plus the work to have the stock inlet for everything.

 

[ShooterwithNoName]

Bandit31, I have been considering the Bravo. It looks like a quality chassis, for the price they are hard to beat. They also look like they are about as rugged as you could ask for. As far as chamber selection, I wanted something to shoot 338s out of. I have a Sako A7 in 7mmMag and it's a great hunting rifle with terrific out of the box accuracy. The main purpose of this build is so that I will be able to assemble and do all the work myself. I chose a Remage barrel so I can headspace it. I have fit a PTG bottom metal into an HS stock before, while it wasn't pretty I know now that I can do it better with lessons learned. The action will be trued to the PTG bolt by a local gunsmith. I'm trading services for that work so the cost there will be negligible I just lucked out that he needed refrigeration work done. In the end, I may very well go with the KRG. Down the road I plan on having something like that.

B y r o n, I've read about nodding the front rib off of 338LM aics mags. If I would end up with going that route it would definitely be an option. I would have to come up with some kind of way of plugging the split. Do they feed good out of the modded 338LM mags?

 

[B y r o n]

. . . B y r o n, I've read about nodding the front rib off of 338LM aics mags. If I would end up with going that route it would definitely be an option. I would have to come up with some kind of way of plugging the split. Do they feed good out of the modded 338LM mags?

There is no need to plug up the milled area. The shoulder of the RUM case rides right up at the front edge of the milled slot. It does have a small clearance but don't remember the exact amount. The rounds feed flawlessly from the mags I had modified.

I was able to get an 0.008" shim between the cutout and the shoulder on both sides at the same time.

 

[ratton]

Seekins used to make a nice 338 mag and floor plate. I had a friend install it on his Rem 338 Ultramag

 

[ShooterwithNoName]

Thanks for that pic Byron, I see what you mean. Mind if I ask what the max OAL you can load your 338RUM to and still fit the mag?

I hope to be able to tuck 285s and find a sweet spot with velocity that'll fit in a magazine. But if I have to single load the 285s its not a deal breaker. I really prefer having a detachable mag setup. I've shot a lot with drop floor plates. I prefer to be able to reach for a mag vs. digging rounds out and trying to feed them down into the box with a scope mount in the way while shooting prone. Most all the shooting I do with this rifle will be prone.

My hunting loads will be the majority of what will be mag fed. Ill be single feeding the longer target rounds.

 

[B y r o n]

Thanks for that pic Byron, I see what you mean. Mind if I ask what the max OAL you can load your 338RUM to and still fit the mag?

I hope to be able to tuck 285s and find a sweet spot with velocity that'll fit in a magazine. But if I have to single load the 285s its not a deal breaker. I really prefer having a detachable mag setup. I've shot a lot with drop floor plates. I prefer to be able to reach for a mag vs. digging rounds out and trying to feed them down into the box with a scope mount in the way while shooting prone. Most all the shooting I do with this rifle will be prone.

My hunting loads will be the majority of what will be mag fed. Ill be single feeding the longer target rounds.

3.683" for inside the magazine, 3.725" externally and 3.596" for the rounds that were loaded in the magazine. I don't remember if they are 300 gr. or 250 gr. as they were the last rounds in one of my boxes and no card as to what they were loaded with or bullet weight. They're just fouling rounds now I guess. They feed just fine.