7-08 vs 7 SAW vs 7CM vs ? for Large Frame

[penguinofsleep]

Not looking to build this soon, but want to see what my options are:

Looking to use 130-150gr bullets, not strictly a target / paper puncher. Would prefer ability to use whatever poly and metal large frame mags (shorter COAL). 20" barrel. Will probably want a 0.75" gas block to keep weight reasonable if carrying.

Precision:
Before I figure anything else out, I want to see if platform will be "precise enough" - assuming build / parts are good and I can shoot a (precision large frame) gas gun properly, what size groups can I realistically expect from Tipped GameKings, Hornady Interlock, and various Speer offerings in this weight range? Am I realistically looking at < ~2-3 MOA 10 shot groups?
150gr SMK for target shooting - can I still realistically expect ~1-1.5 MOA 10 shot groups?

Feeding / reliability:
Most importantly - Does case geometry of any particular cartridge in this class allow for inherently better feeding?
Is one going to be easier to sort out with the gas system, buffer, spring rate / length, bolt carrier, etc.

Brass:
I see 7mm-08 brass is usually commercially available. How time consuming is it to form 7mm-08 brass from 308 if I really need to?
I see that WTO says that 7 SAW can be formed from 308 with just a full length resize (i.e. 1 step) - looks like it's just necking down and pushing the shoulder down a bit and to 30 deg from 308. Anyone experience otherwise?
7cm hasn't been standardized, but are most chambers cut for 6.5cm brass that has had a 7mm mandrel run through it (maybe with the neck shoulder junction back a tiny bit?)

Velocity and powders:
Looks like these have similar velocities. WTO states that 6.5x47L powders work well for 7 SAW. Is one easier to load for overall? Is one going to be very compressed with a popular powder and polymer mags?

 

[Old Man with Gun]

My stock SP-10 in 6.5 Creedmoore shoots 140 ELD into sub MOA, I think a 10 shot 1.5 MOA group would be easy. It is very reliable with one quirk that I have never bothered to try to fix. Sometimes the bolt release doesn't lock the bolt tight, but when I pull back the charging handle and release, it is fine.

May not be what you are looking for, but a precision large frame is very realistic.

 

[AR shooter]

As long as you get a good barrel and you do your part and it likes the bullets you use a 7mm is very capable of MOA or better shooting. I just built a 7mm 08 with a 24" X caliber barrel. I'm shooting 162 gr. ELDM's and 175 gr. ELD-X, they shoot equally good. High BC's is what I was looking for and not disappointed.

 

[AR shooter]

duplicate

 

[Tx_Flyboy]

I have a 7mm-08 with an 18” Wilaon barrel. Still working up a load for it, so no amazing groups to show for it.

I have shot excellent groups in large frame ARs in .308, so 1MOA or better is absolutely feasible.

I haven’t seen Lapua brass for the ‘08, or the other calibers you mentioned, but I suppose you can form them from .Lapua .308, 6.5CM brass as needed.

My advise would be to get a 20” to 22” barrel as the 7mms do very well in longer barrels. Expect a loss of about 30-35ft/s per inch of length.

 

[knuckleballz]

7 saum if you’re stuck on 7mm. Magazine’s are the only drawback to going saum. You can put 4 saum rounds in a 10 round pmag and it will feed perfectly. Larger magazines will bulge and not feed well.

 

[camotoe]

7creed

 

[LRRPF52]

 

[The Knuckle]

Seems sig did a lot of testing in this area and settled on the 277 fury which is a 7-08 AI necked down. I’ve been leaning this way myself but a part of me says a 7-08 or 6.5cree would probably be just fine and more common

 

[ggmanning]

Built my son a 7 Creed 18" several years ago for a suppressed hunting rifle. Brass is easily made from the 6.5 Creedmoor. Dies are just 6.5 Creed with a 7mm neck bushing. Accurate round, pounds deer very well with 150's

 

[LRRPF52]

7mm SWC is a necked-up 6.5x47L, with Alpha brass already available.

You can load the super long 190gr class of 7mm bullets as well, and run high pressures if you want.

162-175gr are screamers from it. Alpha brass changes the game with it.

 

[232593]

7mm SWC is a necked-up 6.5x47L, with Alpha brass already available.

You can load the super long 190gr class of 7mm bullets as well, and run high pressures if you want.

162-175gr are screamers from it. Alpha brass changes the game with it.

The background Garmin numbers are from 190s? What barrel length are you running?

 

[Shoreglide]

Pic looks familiar…

https://shermanwildcatcartridges.com/7swc-1

 

[LRRPF52]

The background Garmin numbers are from 190s? What barrel length are you running?

Not my pics. That’s off Sherman website.

I was thinking about doing 7mm SAW until I saw that Alpha makes the 7mm SWC brass.

 

[232593]

Not my pics. That’s off Sherman website.

I was thinking about doing 7mm SAW until I saw that Alpha makes the 7mm SWC brass.

Are you going to do a 7mm SWC now?

 

[LRRPF52]

Are you going to do a 7mm SWC now?

It’s on a distant back burner. All my current focus is on more important work.

But for a high performance cartridge that fits inside the AR-10 action using .473” case head, the better-designed 7mms really have had my attention for a while.

I was looking at 7mm SAW until Alpha told me about 7 SWC.

I already have some experience with 7mm-08.

7 SWC can run 190gr A-TIP at very respectable speeds. I love the sound of 7mm higher BC bullets hitting steel at distance, and how easy it is to hit with them in the wind. I don’t notice the difference in recoil between 7mm-08 and .308 Win.

The 7mm BCs crush everything in 6.5mm and .30 Cal when you look at them:

190gr Hornady A-Tip Match	0.838	Match
180gr Hornady ELD-Match	0.796	Match
197gr Sierra MatchKing HPBT	0.780	Match
195gr Berger Extreme Outer Limits (EOL) Elite Hunter	0.755	Hunting
190gr Berger Long Range Hybrid Target	0.751	Match
185gr Nosler RDF	0.719	Match
183gr Sierra MatchKing	0.713	Match
184gr Berger F-Open Hybrid Target	0.695	Match
175gr Hornady ELD-X	0.689	Hunting
180gr Berger Very Low Drag (VLD) Target	0.683	Match
180gr Berger Hybrid Target	0.680	Match
180gr Berger Very Low Drag (VLD) Hunting	0.673	Hunting
162gr Hornady ELD-Match	0.670	Match
180gr Sierra MatchKing	0.660	Match
180gr Lapua Scenar-L	0.660	Match

 

[232593]

It’s on a distant back burner. All my current focus is on more important work.

But for a high performance cartridge that fits inside the AR-10 action using .473” case head, the better-designed 7mms really have had my attention for a while.

I was looking at 7mm SAW until Alpha told me about 7 SWC.

I already have some of experience with 7mm-08.

7 SWC can run 190gr A-TIP at very respectable speeds. I love the sound of 7mm higher BC bullets hitting steel at distance, and how easy it is to hit with them in the wind. I don’t notice the difference in recoil between 7mm-08 and .308 Win.

The 7mm BCs crush everything in 6.5mm and .30 Cal when you look at them:

190gr Hornady A-Tip Match	0.838	Match
180gr Hornady ELD-Match	0.796	Match
197gr Sierra MatchKing HPBT	0.780	Match
195gr Berger Extreme Outer Limits (EOL) Elite Hunter	0.755	Hunting
190gr Berger Long Range Hybrid Target	0.751	Match
185gr Nosler RDF	0.719	Match
183gr Sierra MatchKing	0.713	Match
184gr Berger F-Open Hybrid Target	0.695	Match
175gr Hornady ELD-X	0.689	Hunting
180gr Berger Very Low Drag (VLD) Target	0.683	Match
180gr Berger Hybrid Target	0.680	Match
180gr Berger Very Low Drag (VLD) Hunting	0.673	Hunting
162gr Hornady ELD-Match	0.670	Match
180gr Sierra MatchKing	0.660	Match
180gr Lapua Scenar-L	0.660	Match

I wonder how those bullets perform on tissue with impact velocities of 18-2000 fps?

 

[steve123]

It’s on a distant back burner. All my current focus is on more important work.

But for a high performance cartridge that fits inside the AR-10 action using .473” case head, the better-designed 7mms really have had my attention for a while.

I was looking at 7mm SAW until Alpha told me about 7 SWC.

I already have some of experience with 7mm-08.

7 SWC can run 190gr A-TIP at very respectable speeds. I love the sound of 7mm higher BC bullets hitting steel at distance, and how easy it is to hit with them in the wind. I don’t notice the difference in recoil between 7mm-08 and .308 Win.

The 7mm BCs crush everything in 6.5mm and .30 Cal when you look at them:

190gr Hornady A-Tip Match	0.838	Match
180gr Hornady ELD-Match	0.796	Match
197gr Sierra MatchKing HPBT	0.780	Match
195gr Berger Extreme Outer Limits (EOL) Elite Hunter	0.755	Hunting
190gr Berger Long Range Hybrid Target	0.751	Match
185gr Nosler RDF	0.719	Match
183gr Sierra MatchKing	0.713	Match
184gr Berger F-Open Hybrid Target	0.695	Match
175gr Hornady ELD-X	0.689	Hunting
180gr Berger Very Low Drag (VLD) Target	0.683	Match
180gr Berger Hybrid Target	0.680	Match
180gr Berger Very Low Drag (VLD) Hunting	0.673	Hunting
162gr Hornady ELD-Match	0.670	Match
180gr Sierra MatchKing	0.660	Match
180gr Lapua Scenar-L	0.660	Match

As much as I don't want to get back into large frame that 7 SWC with heavies is very appealing.

Who would you guys recommend doing the chamber and barrel work if I did go this way?

 

[putput30]

A 7 SWC slinging 180 eld-ms would be a long range monster out of an ar-10...

 

[nickw]

As much as I don't want to get back into large frame that 7 SWC with heavies is very appealing.

Who would you guys recommend doing the chamber and barrel work if I did go this way?

I’d reach out to Craddock. I bet if you supplied the reamer they would get it done for you.

 

[davethedog]

I don’t want to sound like a naysayer but my experience with Sherman wildcats and 7mm wildcats in general is that nobody is really going to achieve the touted 2700fps with a 190.

Most of us shooting 7mm saw are getting just north of 2700 with the 160s, a few can get close with 180s but they’re pushing it quite a bit.

Do we really believe that the steeper shoulder and reduced taper is going to get those speeds? I sure as shit don’t. I may just be salty though after Sherman’s 7ss reamer/brass debacle and the way he handled it though.

 

[LRRPF52]

I’ll be plenty happy with 2500fps from a gas gun with a 190gr A-TIP.

162s going much faster are no slouch either. External ballistics were really good when I looked at them, but nothing really sounds like 180-195gr momentum on-target.

Radar data for 162gr ELD-M is amazing even at 2500fps. Same with 190gr A-TIP or any of the high BC 7mms.

 

[XP1K]

I wanted to do a 7saw barrel for my MWS but now y'all got me thinking.

 

[D_TROS]

huge fan of the 7-08 for components

KISS

shooting 168 bergers at 2720

great catridge for NRL Hunter as well as real life hunting.

 

[LRRPF52]

With Alpha Munitions 7mm SWC brass, the choice is pretty easy.

If there’s a cartridge I load for and Alpha makes brass for it, I will just buy that and not look back.

I’ve loaded for 7mm-08 in the past, and really love that cartridge. It’s what 7.62x51 should have been, and we should have known that from 7x57 Mauser performance already. 7x57 Mauser was one of the best military rifle cartridges ever developed and mass-produced.

Instead, we stubbornly stuck with the .30 cal bore because of institutional biases in Army Ordnance Board/CONARC. I don’t hate .30 cal, but you just get better performance from 7mm with higher sectional density for weight.

.276 Pedersen was our missed opportunity, which would have solidified 7mm in the US arsenal system going into the 1950s after the War. Would have made an awesome little AR-10 with a smaller frame, higher mag capacity, using the Pedersen’s case head.

 

[LRRPF52]

After the War, Army Ordnance and Fort Benning wanted a smaller COL than M2 ball (.30-06), but with the same performance. So they shortened the case to something similar to 300 Savage and increased the chamber pressure, added a boat tail to retain energy resulting in the T65 and later 7.62x51.

If they had done the same thing with the .450” case head .276 Pedersen, we would have had something with a 2.400 to 2.600” COL, running higher pressure in the M14, FAL, G3, and AR-10.

 

[st1650]

7SAW with the 162 eldm and the 160 TMK. Most efficient case in the short action game. Especially when limited to the 2.80in coal.
And alpha brass is available