7 RSAUM in a Bighorn short action

[Backcountry sports]

I have searched this forum for an hour, sorry I'm a newby on the forum. I was hoping to chamber an 8 twist proof, carbon barrel in 7 RSAUM and screw in on a Bighorn origin short action. It will be a lightweight hunting rig, probably for 175 grain Nosler ABLR bullets, because I have several 100. I could switch bullets if need be but I would like to shoot at least 175s. The plan is to magazine feed and may go with a Wyatt's box to seat as long as possible. Does anyone have any real world experience with a similar setup and if so, what freebore reamer did you go with? I have seated a ABLR bullet to several seating depths to try to see where the junction is but I have not received the Wyatt's box yet so I don't know my exact seating depth. If anyone has experienced a similar scenario, I would appreciate your thoughts. I already have a couple hundred pieces of 7 saum, Normabrass, a proof barrel and an Origin action (just have to get a magnum bolthead).

 

[Backcountry sports]

I have remington bdl 7saum with vias muzzle shoots fantastic and with scope less than 8lbs just loaned it to a lady elk hunting 350 yards she killed here cow perfect shot 160 grain nosler partition

 

[Rent Outdoor Gear]

I have searched this forum for an hour, sorry I'm a newby on the forum. I was hoping to chamber an 8 twist proof, carbon barrel in 7 RSAUM and screw in on a Bighorn origin short action. It will be a lightweight hunting rig, probably for 175 grain Nosler ABLR bullets, because I have several 100. I could switch bullets if need be but I would like to shoot at least 175s. The plan is to magazine feed and may go with a Wyatt's box to seat as long as possible. Does anyone have any real world experience with a similar setup and if so, what freebore reamer did you go with? I have seated a ABLR bullet to several seating depths to try to see where the junction is but I have not received the Wyatt's box yet so I don't know my exact seating depth. If anyone has experienced a similar scenario, I would appreciate your thoughts. I already have a couple hundred pieces of 7 saum, Normabrass, a proof barrel and an Origin action (just have to get a magnum bolthead).

I just did this exact build. It doesn't work... The Wyatt PRC box is too long for the mag well. Bighorn says the action won't take that box, and a standard SA mag box won't work with factory Hornady 143 ELDX.

It appears the action can be cut to allow possibly using the Wyatt PRC box, but it's a little dicey. Gotta do some measuring before I take a carbide endmill to the action. Hate the idea of loading short rounds for this rifle and using valuable case volume.

I'll let you know how it works out.

 

[Arapaho]

I just did this exact build. It doesn't work... The Wyatt PRC box is too long for the mag well. Bighorn says the action won't take that box, and a standard SA mag box won't work with factory Hornady 143 ELDX.

It appears the action can be cut to allow possibly using the Wyatt PRC box, but it's a little dicey. Gotta do some measuring before I take a carbide endmill to the action. Hate the idea of loading short rounds for this rifle and using valuable case volume.

I'll let you know how it works out.

Yes, let me know how it works out. I am taking my time so I won't get frustrated. I built two rifles this year and this was going to be the third but I don't want to cut myself short. If nothing else, I'll screw another prefit on her chambered in a small 6 until I figure it out.

 

[WiscGunner]

I built a similar set up in a 7SS (TL3 and 26" Proof Sendero) that shoots 180 ELD-M's (so far). Excellent combo from a DBM. If you are worried about seating to max capacity I suggest removing emotion and looking at the actual numbers of what less velocity does for you at you intended ranges. Those 180 ELD-M's cut through the wind fantastically and are extremely effective on game. Run some numbers in your ballistic app and see what 50-200 fps less means for your wind holds. An extra click or 2 elevation is nothing when dialing but if you are a short range hunter looking for point blank zero then perhaps lighter faster bullets would be your ticket.

 

[joshf303]

I built a similar set up in a 7SS (TL3 and 26" Proof Sendero) that shoots 180 ELD-M's (so far). Excellent combo from a DBM. If you are worried about seating to max capacity I suggest removing emotion and looking at the actual numbers of what less velocity does for you at you intended ranges. Those 180 ELD-M's cut through the wind fantastically and are extremely effective on game. Run some numbers in your ballistic app and see what 50-200 fps less means for your wind holds. An extra click or 2 elevation is nothing when dialing but if you are a short range hunter looking for point blank zero then perhaps lighter faster bullets would be your ticket.

Good points Gunner. Same can be said for useable powder space...
There is a point of diminishing returns.

 

[Arapaho]

Good points Gunner. Same can be said for useable powder space...
There is a point of diminishing returns.

Thanks for the input guys, it is really appreciated. I agree with both of you and never have really been a speed freak. I do however like to reach a particular cartridge's potential or just do another caliber and/or cartridge. Gunner, I have been doing some homework on the 7ss but I would have to spend quite a bit more coin to change up in the game now dies, brass (unless I use the rsaum brass instead of headstamped ADG) and probably a new dbm stock. Currently, I have 3 BDL stocks to choose from. Then reamer wether or not rented or purchased. I know it will go faster but not sure if I want to sink that much more money into this build.

 

[Another Casual]

I had my Origin opened up for the Wyatt's extended box for my PRC. It was $80 for the local smith to do it. DBM is probably easier, but I preferred the BDL for this one. Feeds well and I'm happy with it overall. Still tweaking the spring, every once in a while when loading 3 rounds down the first one doesn't present all the way, but that seems to be spring related. Feed rails work fine in my experience.

 

[Rent Outdoor Gear]

Yes, let me know how it works out. I am taking my time so I won't get frustrated. I built two rifles this year and this was going to be the third but I don't want to cut myself short. If nothing else, I'll screw another prefit on her chambered in a small 6 until I figure it out.

I took another good look at the Bighorn Origin and decided to cut the action as I couldn't see any reason that it would not work even though Bighorn customer service said otherwise. The extended box dropped right in and fed flawlessly with longer PRC cartridges. Factory PRC rounds would not fit in the standard SA length DBM box. I would not hesitate to have your smith make the modification so you can load a longer OAL with the SAUM. Might as well get the most out of it if you're building a custom.

 

[joshf303]

I took another good look at the Bighorn Origin and decided to cut the action as I couldn't see any reason that it would not work even though Bighorn customer service said otherwise. The extended box dropped right in and fed flawlessly with longer PRC cartridges. Factory PRC rounds would not fit in the standard SA length DBM box. I would not hesitate to have your smith make the modification so you can load a longer OAL with the SAUM. Might as well get the most out of it if you're building a custom.

Which DBM mag?

 

[elkaholic]

I took another good look at the Bighorn Origin and decided to cut the action as I couldn't see any reason that it would not work even though Bighorn customer service said otherwise. The extended box dropped right in and fed flawlessly with longer PRC cartridges. Factory PRC rounds would not fit in the standard SA length DBM box. I would not hesitate to have your smith make the modification so you can load a longer OAL with the SAUM. Might as well get the most out of it if you're building a custom.

How much length did you end up with?

 

[Rent Outdoor Gear]

The only DBM that would work with the stock inlet was the HS Precision SA which is only 2.86" as I recall, at least .100" too short for factory PRC ammo. AICS .308 mag would have had enough length but the stock would not work for an M5 style bottom metal.

The Wyatt's box is about 3" so 2.95" COAL works fine with the Origin action cut to accommodate the extended box.

 

[atepointer]

Anyone else have experience the last couple of years with the 7SAUM in an Bighorn SA they would add to or caution me on? I've held off on the 7SAUM b/c brass was ridiculous for so long, but seeing more and more and more of it. I don't want to buy a new action, but man if I can get Northland to cut some muzzle threads in a 28"+ barrel for my old SA.......oooooohhhh weeee I could be had now that components are starting to flow.

If I don't care about mag loading issues b/c I use a loading block for bench rest shooting only 1 at a time....does that alleviate all said concerns above on an SA? I'd like to venture into to 180g world if I can. I've seen some astonishing shooting at 1 mile with his cartridge locally I mean wow. Grapefruit sized groups in the middle of an IPSC target. All I could do was clap and say well done stud!

 

[Trm82]

I bought a Fierce Rival in a 7 saum and it's a short action which shoots like the dickens but if I was building I definitely would not be building on a short action.
These are 175 elites seated at mag length