Which chassis and magazine system for a 7mm SAUM ?

[Jumper]

I'm planning my first bolt gun build so this might be a real dumb question; It will be a 7mm R-SAUM with the Archimedes long action from American Rifle Company. I would like to use the Magpul Pro 700 chassis but this is where things get uncertain: The 7 R-SAUM case diameter is .550" with a case length of 2.035" and a cartridge length 2.825" in a short action. I think it grows to about 3" in a long action. Will this feed from an AICS magazine? CIP magazine? Magpul states their mags won't work with cartridges derived from the 404 jefferies. While the 7 SAUM technically isn't, it's almost a twin of the 7 WSM which IS derived from the 404 Jefferies. I guess I just need some advice on magazine options for the 7 R-SAUM and compatible chassis's. Thanks.

 

[Steel head]

Regular or CIP 300 WM mags will be good.
Any chassis taking those mags will be good.
In standard .09 freebore chamber.
you be on the lands at around 3”ish with 180 & 190’s.

 

[b6graham]

who's doing the barrel?

7 saum just doesn't make sense to me when you could 7SS/7SST from a true short action with ideal bullet placement or any of the true long action 7mms from a long action. 7 Max, 7 rem mag. 7/300 practical. 28 Sherman Mag. 280AI, 284 any variety

 

[Jumper]

Ok 300wm makes sense. Any mag that works with it will also work with 7 SAUM.

As for the 7SS/SST and the other 7mm variants; I'm not comfortable with a wildcat or borderline wildcat. Also the SAUM is a short fat cartridge. Shorter cartridges lend themselves to better consistency. It's easier to ignite a shorter powder column and get consistent burn than a long powder column like the 280 AI, 7mm Rem Magnum or Ultra mag. The 7 R- SAUM just checks most of the boxes for my needs.
Patriot Valley Arms is doing the barrel.

 

[Steel head]

You’ll like 7 saum.
Easy to load with decent performance.
If I did one in a long action I might get another .03-.04 extra freebore, that would Probably get 180-190 out of the shoulder neck junction.
That said I had absolutely no issues seating them deeper for my chamber.

 

[BCX]

Running my 7 Max on a long action loaded 3.200 plus w 190/195. No issues running 7 saum from a HS mag and bottom metal. I have played w the loaded 7 saum in AI 300 WM mags and 338 CIP mags. Both should work no problem.

 

[Jumper]

You’ll like 7 saum.
Easy to load with decent performance.
If I did one in a long action I might get another .03-.04 extra freebore, that would Probably get 180-190 out of the shoulder neck junction.
That said I had absolutely no issues seating them deeper for my chamber.

So you made yours short action? I'm on the fence .... I will probably shoot bullets in the 154 to 162gr range. Probably don't need a long action for that.

 

[Steel head]

So you made yours short action? I'm on the fence .... I will probably shoot bullets in the 154 to 162gr range. Probably don't need a long action for that.

On a short action I mag feed 168’s (Berger classic hunters @2.86 which is close to the lands) and single feed 190’s at a bit over 3.0.

lighter hunting bullets in 7 saum absolutely work in a short action with lots of room in the mags and feed nicely.

 

[Jumper]

Thank you very much for the help.
Was just checking out the 7 SAUM thread in the reloading depot and saw your posts there. This is a new caliber for me but I've been considering it for a long time. When I have more questions I'm going to look you up.

 

[robozebra]

I shoot 168 Berger VLD Hunter in my 7 SAUM in a short action. Great rifle. I’m getting around 3100 out of mine.

I’m considering going to the Cayuga 170 grain, but that puts length to 3.150. I’ll likely build one when XLR makes the magnesium chassis in XM length. Want to try an ultralight chassis. Would love to see how it’ll handle the 170 grain.

Good luck!

 

[Jackomason]

I shoot 168 Berger VLD Hunter in my 7 SAUM in a short action. Great rifle. I’m getting around 3100 out of mine.

I’m considering going to the Cayuga 170 grain, but that puts length to 3.150. I’ll likely build one when XLR makes the magnesium chassis in XM length. Want to try an ultralight chassis. Would love to see how it’ll handle the 170 grain.

Good luck!

Im thinking about ordering the 151gr for my 7mm mag, have you tried those in your SAUM?

 

[Army First]

Patriot Valley Arms is doing the barrel.

How long has your barrel been on order with PVA? May 18th for me.

I got the bug and started my search for 7SAUM items in April. The brass is kind of hard to find, I picked up some at Gunwerks and picked up some used 7SAUM brass here. I have not looked recently but the other vendors may have restocked by now. The neck bushings were found on Ebay, the Redding dies were found at the usual places.

Good Luck with your 7SAUM

 

[Jumper]

I talked to PVA yesterday just inquiring about lead times. Officially I haven't ordered anything. Justin at ARC said that PVA can make the barrel for their actions without the action in hand and I verified this with PVA. So the plan is to order both at the same time, ship the action directly to PVA when it's done, and have them install and headspace it. Then PVA ships me the barreled action and I do the rest. Hopefully this saves waiting for the action, then waiting again for the barrel. I'm anticipating about 6 to 8 weeks for this process. We'll see.
Also brass availability worries me somewhat as well. Only found some Nosler at Midway...

 

[b6graham]

I talked to PVA yesterday just inquiring about lead times. Officially I haven't ordered anything. Justin at ARC said that PVA can make the barrel for their actions without the action in hand and I verified this with PVA. So the plan is to order both at the same time, ship the action directly to PVA when it's done, and have them install and headspace it. Then PVA ships me the barreled action and I do the rest. Hopefully this saves waiting for the action, then waiting again for the barrel. I'm anticipating about 6 to 8 weeks for this process. We'll see.
Also brass availability worries me somewhat as well. Only found some Nosler at Midway...

ADG

Unknown Munitions often has it

 

[Steel head]

For 7 saum brass I use ADG.
Also look at their dealers and Gunwerks.
Brass life And quality with with ADG has been excellent

 

[Franko]

I see no point to a 7 SAUM if you are going to build the rifle on a long action. A 7mm RM will get you the same or better performance, handle the really long projectiles better, has readily available good brass, and a very wide variety of factory ammo. I urge you to reconsider. I say this as someone that just built a 7 SAUM on a short action.

 

[Jumper]

Thanks for your opinion. I called up PVA today and ordered the barrel in 7SAUM. Also ordered the Archimedes action. A long action. I intend to shoot bullets in the 154 to 168gr weight. I don't want to shoot the ultra heavies. I want to be able to if I decide to. PVA',s reamer is SAMMI spec so I think it's probably optimized for COL's around 2.800" since that's the design length for a short action. Feeding longish "short action" cartridges in a long action with the controlled round feed of the Archimedes should be pretty reliable. And, I'll have the optimum chamber freebore for the bullets I want to shoot. What have I overlooked?

 

[Franko]

You may want to consider an XLR Industries Element 3.0 magnesium chassis. It is what I have my rifle built on and I really like it. Good luck.

 

[robozebra]

Im thinking about ordering the 151gr for my 7mm mag, have you tried those in your SAUM?

I haven’t tried those yet. Was thinking of trying them, but concerned they won’t shoot well. My barrel is 1:9 twist.

 

[robozebra]

I see no point to a 7 SAUM if you are going to build the rifle on a long action. A 7mm RM will get you the same or better performance, handle the really long projectiles better, has readily available good brass, and a very wide variety of factory ammo. I urge you to reconsider. I say this as someone that just built a 7 SAUM on a short action.

I know that you‘ve moved ahead, but I agree with this statement. I was considering the same thing, but think it could be a bit of a waste. Thinking I’ll do a 7LRM or possibly 7-300 PRC until XLR builds the Element 3 Magnesium in a XM length.

 

[robozebra]

Thanks for your opinion. I called up PVA today and ordered the barrel in 7SAUM. Also ordered the Archimedes action. A long action. I intend to shoot bullets in the 154 to 168gr weight. I don't want to shoot the ultra heavies. I want to be able to if I decide to. PVA',s reamer is SAMMI spec so I think it's probably optimized for COL's around 2.800" since that's the design length for a short action. Feeding longish "short action" cartridges in a long action with the controlled round feed of the Archimedes should be pretty reliable. And, I'll have the optimum chamber freebore for the bullets I want to shoot. What have I overlooked?

If you are shooting 168 gr bullets, this can be done very efficiently in a short action. Mine shoots great. Only reason I’d build another is to shave a small amount of weight, try a chassis and to shoot the 170 Cayuga.

 

[Jumper]

All good insight but I still prefer a long action for the 7 SAUM. My reasoning is: It works in a long action.
2nd, If I decide later that I want a different caliber I'm not limited by my action to choosing only Short Action calibers. The Archimedes actions have interchangeable bolt faces so changing calibers down the road is just a re barrel plus maybe a bolt face. I like options.

 

[Steel head]

All good insight but I still prefer a long action for the 7 SAUM. My reasoning is: It works in a long action.
2nd, If I decide later that I want a different caliber I'm not limited by my action to choosing only Short Action calibers. The Archimedes actions have interchangeable bolt faces so changing calibers down the road is just a re barrel plus maybe a bolt face. I like options.

If you feel like lobbing some 180-190’s you’ll like the long action.
My Charlie tarac shipped.
There’s a possibility I might try for 3000 yards next week with my 7 saum.

 

[NewsShooter]

Thanks for your opinion. I called up PVA today and ordered the barrel in 7SAUM. Also ordered the Archimedes action. A long action. I intend to shoot bullets in the 154 to 168gr weight. I don't want to shoot the ultra heavies. I want to be able to if I decide to. PVA',s reamer is SAMMI spec so I think it's probably optimized for COL's around 2.800" since that's the design length for a short action. Feeding longish "short action" cartridges in a long action with the controlled round feed of the Archimedes should be pretty reliable. And, I'll have the optimum chamber freebore for the bullets I want to shoot. What have I overlooked?

If you're building in a long action I wouldn't use the sammi reamer, put more freebore in it so you can seat long bullets out farther. Gives you the option to use the 175-190 grain bullets with better BC. Personally I'd build it on a Tikka, it's about perfect with a 3.56 long action, MDT makes a chassis and mag to fit it. Hells Canyon makes a mag for the factory bottom metal which gives you lots of other options.

 

[Jumper]

Yeah,... short action might be better if I'm going to shoot the 168 range projectiles... Been doing a lot of research... Still undecided but leaning towards the SA. Starting to think the 6.5 SAUM by GA Precision might be the gun to model mine after.

 

[Steel head]

Yeah,... short action might be better if I'm going to shoot the 168 range projectiles... Been doing a lot of research... Still undecided but leaning towards the SA. Starting to think the 6.5 SAUM by GA Precision might be the gun to model mine after.

The short action route is what I’d do if I was doing a hunting build with 168’s and lighter.
You can still single feed heavies if needed.

 

[robozebra]

Yeah,... short action might be better if I'm going to shoot the 168 range projectiles... Been doing a lot of research... Still undecided but leaning towards the SA. Starting to think the 6.5 SAUM by GA Precision might be the gun to model mine after.

If you lived closer to OKC, I’d let you shoot mine to see how you like a short action 7 SAUM. I don’t have any issues with feeding 168 grain Berger VLD. Plenty of length. I’m getting about 3125 out of them. Crazy fast. Bolt gets a bit heavy with suppressor, but without it cycles just fine.

My quandary is that I’m looking to shoot 170 Cayuga’s but really need a XM length to do that right. XLR doesn’t make the magnesium chassis in XM length yet (hint hint XLR...), so I’ll likely build a 7 LRM for the 170 Cayuga to whet my appetite for chassis.

 

[Jumper]

Thanks for the advice. I think choosing a chassis is the hardest decision about this project... I should probably start with the magazine that feeds the 7 SAUM reliably and then get the appropriate chassis. Would the 7 SAUM work in 6.5PRC magazines?

 

[robozebra]

Yes. I run Accurate Mags with ALTUS +2 extensions. They work great.

 

[Steel head]

Thanks for the advice. I think choosing a chassis is the hardest decision about this project... I should probably start with the magazine that feeds the 7 SAUM reliably and then get the appropriate chassis. Would the 7 SAUM work in 6.5PRC magazines?

With 168 and under, yes.
With 180’s, yes with some jump.

 

[Jumper]

After cancelling my initial order with ARC for a long action (Sorry Mr Karaigis) I ordered a short action Archimedes, action wrench and a set of M10 scope rings. I was really undecided about doing this caliber in a short action. A couple things swayed my decision; input from this forum, and finding a mag from area 419 that lists a max c.o.l. of 2.925. for the 7 SAUM. That's long enough if I want to try some heavies. Now for the chassis. Base option is the KRG Bravo. If my budget doesn't get consumed with peripheral things like dies and triggers I had planned on the Magpul Pro700 folder. Looked at the MDT models. Nice, but just doesn't appeal to me but I'm sure I'd be fine with it if I saw it in person. Thanks all for the info to all who posted. Very helpful.