My thinking is probably warped here, but here goes. It seems as .308 is becoming very popular for ARs today. Why not build a 7mm-08 AR? I would think it would use the same upper and lower as the .308, and the same bolt & carrier assembly. I had one in a bolt action rifle once and really liked it. I was thinking it would be really nice in an AR. What am I missing here? Is it even practical? I own 2 7.62 X 51 NATO rifles already, an M1A & a DSA-FAL. Like both of them, so am looking for something different. You can only build so many 5.56 ARs & it seems like why build more. Just wondering.

Thanks,
Mark

Remington already makes one, I think they call it the R25, in .243, 7mm-08 & .308.  I'm a 7mm-08 fan too.

All else being equal I'd rather have a 6.5 Creedmore myself.
If there is huge difference in reloading 7mm bullets for some specific reason I could see 7mm but if it just means heavier bullets can be had in 7mm I would stick with .308.
Or if for instance you already have a 7-08 bolt action.

These discussions often degrade into what is basically a preferential issue.  For me, in bolt guns you get less felt recoil as you go down from .308 to 7mm/08 to .243, and so on...same with 30.06 to 270 to etc.  Yes there are other factors, but recoil is often the primary one in these upper calibers...it's a different issue for something like a 25.06 and why people go there...usually.  With AR platforms, the recoil just isn't as a big a factor in a rifle where the gas system, BCG, and buffer setup combine to shoot smoothly and cycle reliably.  7mm/08 is a great bullet, but in AR platforms perhaps not a great advantage when .308 shoots pretty darned softly.  Check your reloading manual, and you'll see there isn't a great deal of advantage there either between .308 and 7mm/08.  For fun, for uniqueness...lots of options that don't have to qualify absolute logic.  Ammo availability "can" also be an issue sometimes if you don't reload in certain calibers.  I have a .243 AR10 to compliment my .308 model, and it fits well as a powerful varmint rifle...and ammo is readily available.  Lots of likes and dislikes in choices like these, and it often comes down to just trying a few...but that can get expensive.

I will add to this.  Many years ago I decided to cut down on my calibers.  I got tired of so many bullets, gr weight and caliber.  So I decided to just stick with the .22 center fire, .257 and the .284.  I have many bolt action and lever action BLR's in these calibers.  I no longer have any .30 calibers, the last one I sold was a 300 H&H.  so for me the 7-08 in a AR10 is on my list, as well as a 25 Souper and a 25x45 or 25/222 in an AR15. I already have a bolt gun in the 25x45.  I am not sure which AR-10 round I will do first in my Armalite. but it will be one of those two.  Yes I reload, lots of wild cats and ack imp.  So I follow the 7-08 posts, too bad there are not more barrel options out there to choose from.  I also wish I could get BHW to do a 25 Souper barrel since they already make .257 barrels all they need to do it buy a reamer.

As far as I'm concerned there is no magic bullet, pun intended. While one cartridge vs another might be a bit more effecient than another in burn rate, or be rated for higher pressure, the reality is that all else being equal, projectile weight determines the amount of case capacity needed to propel the chosen bullet at a specific velocity, adhering to pressure limitations. Or, vice versa, case capacity determines how fast you can push a chosen bullet. Realistically you have to compare different rounds with the projectiles they are best equipped to shoot. You can shoot heavy or light for caliber bullets in any cartridge, but the compromise is always in the middle...energy and velocity.

If you want less drop from a round, you push a bullet faster. A 308 can only push a 168gr bullet (for instance) so fast. Yes, you can drop down to a 125gr bullet to increase velocity, but you lose ballistic efficiency (and retained energy) doing so. A 125gr bullet of similar design in 7MM is going to have a higher ballistic coefficient, and better energy if the velocity is higher. You want to push a .30 cal round faster with less drop, you step up to any of the larger capacity cases...30-06, 300 Win Mag, the short mags, etc.

I think the 7MM-08 would be a pretty good round for medium sized soft skin game. There are a lot of "professionals" who say that 7MM's of any type are too small for Elk up, yet there are plenty who are successful with even smaller diameter bullets. Range and desired use/performance are what should dictate round selection (edit: I suppose platform needs considered as well, but that is sort of an inherent limitation).

Big +1. I have an 18" 308 AR and I am building a 16" 7mm-08 AR. I also have a 300BLK 12.5" AR. Papa bear, momma bear and baby bear. All will kill deer dead, just depends on how I feel the breezes calling on any given day. The 308 is bigger medicine than is usually needed, the 300BLK results in deer that die after 20-30 yards or so, and the 7mm-08 splits the middle.



I love 7mm-08, just a great cartridge. A bit softer than 308 in the same short action cartridge family and still anchors deer to the ground.



Or so my rationalization goes!



-Stooxie



 

Thank you for all the responses. I will mull it  over.
Again Thank  You
Mark

Currently building a 7mm08 myself. I already have a bolt gun in 7mm08.

IMI mags will allow you to load longer than 2.86" so you can load longer than SAAMI specs for the high BC bullets.

I'm waiting on my 22" BHW barrel to arrive.

This was my thinking exactly in building a 7mm-08 DPMS pattern rifle.  Everybody has a 308, so why don't I do something different?  Conformance is not my style.  Just personal preference.  The 7mm-08 has a proven history of accurate long range shooting, it is a deadly round for deer, and yes, elk.  You can get the heavier bullets, if you choose.

I was just about to pull the trigger on a 6.5 Creedmoor, but went with the 7mm.  Why?  I can find 7mm-08 ammo on the shelf locally.  Can't find the Creedmoor round.  In the end though, it's personal choice.  You can't go wrong with most any of the 308 family of cartridges.

Only thing I'm struggling with is finding 7mm-08 brass for reloading.  I've tried resizing 308 brass, but it chambers hard in my rifle.  The necks have to be turned.  I do not have a neck turner.

But, if you want cheap ammo and easy to find brass for reloading, go with the 308.

Just wanted to check in....  ;)
Weatherby Vanguard & Tika T3 Lite both in 7mm08

7mm

This is the key point in most discussions.

To answer the OP, though, the thinking is not warped. In fact, at one time, RRA was promising 7-08 uppers would be made available for their LAR8. I think they have since removed that promise from their website, and have never seen them follow through on it, but at least they had entertained the idea at some point.

Originally the 7-08 was a faster, flatter shooting, lower recoil alternative to the 308, especially in the competition circles. The popularity of 6.5mm and 6mm alternatives in that cartridge/action size have strongly overshadowed that benefit since then.

Reloading can/should also play a part in many of these cartridge and caliber choices.  Most of these rounds/calibers outside of .308, 30.06, .223, etc. began life as wildcats and offer a lot of options.  For those sticking with off-the-shelf ammo, more standard calibers are probably a safer bet.  I've been playing with the wide array of 150gr bullets for my AR10 .308 and have noticed very good performance for accuracy and distance.  It allows me to stay within a common caliber with a large availability of reloading supplies.  I guess the performance of the AR10 .308 with 150gr bullets shouldn't be surprising since that's the general NATO bullet weight at 147gr in many cases.  Yes, there are so many variables that come into play such as barrel length and barrel twist and what you're using the rifle for and the distances that you'll generally be shooting.  When I used the words "degrade into" about these discussions, I didn't mean that in a negative way...perhaps should have used "boils down to".  It's hard to get/give a precise answer in some of these caliber and rifle configuration threads without lengthy discussion because of the variables.  Most people either don't want to type that much or read that much, and some of that is the nature of the internet.  One can read an entire book on these issues and still have questions.  Instant knowledge is illusive.

Covered here

7mm-08 New Build

Ammoseek 7mm-08


7mm-08 is a great cartridge.  When comparing it to the .308 Win., you need to look at muzzle velocities, barrel length, and more importantly, the BC value.

For elk, the Hornady 139gr GMX is a known performer-it will sail right through them and boat motor the vitals at around 2x the speed of sound, not losing any weight more than the plastic tip in the process.

WDM Bell used a 7x57 Mauser basically (called a .275 Rigby by the Brits) for many of his over 1100 elephant kills, along with .303 Enfield and 6.5x54 Manlicher Shoenauer, and that was without modern projectile technology.  He would have loved the GMX.

BC on the 139gr GMX is .486 G1, so higher than the Sierra 168 Match King for the .308, with less recoil, more muzzle velocity, and you start to see why Army Ordnance Corps screwed us over by insisting on their .30 caliber  (bigger is better) mentality.

The 139gr SST has the same BC as the GMX, so you can have an economy white tail and practice round, then step into the GMX for big game hunts if you want.  You also have:

154gr IB/SST with .525 G1 BC
162gr A-MAX with .625 BC

With the 162gr A-MAX, you have a BC that trashes almost every .30 call pill unless you go into the 220gr magnum-loaded .30 cal pills.

Agreed.

I would really like to thank everyone for taking the time to help/ answer me. I know I want to build something different. I have 7.62X51's .30-06's, a .300 mag. etc etc. I am still thinking on what I want to do different, but leaning toward a 7mm-08. I have some rounds and brass from my days of having the bolt action 7mm-08. I should have kept it.

Thanks again, very much,
Mark

7-08 is an extremely popular hunting cartridge.
7mm pills are pretty sleek and fly very well.

Agreed *3 plus the 7mm bullets just look sexy..... I have a 7mm-08 on the LR308 platform that I don't get to shoot nearly enough

Check out the BC on the Nosler Accubond LR



It's my goal to make this work in a semi auto. They are long bullets, but with my IMI mags I should be able to load them to 2.850" and still have it fit in the mag. Should be able to push them faster than the Hornady 162 gr Amax.

all true, its just atha a .264 chambering offers substantial improvements in BCs, SDs & trajectory compared to 308.  The benefits of the .284 variant comared to the 30 cal are marginal.

JSmithXYY did you not read the thread?  162 AMAX and 168 VLDs (let alone the 180) have higher BC's than any .264 rounds, especially in the AR10 platform.  Its about whether or not you can get the velocity high enough to take advantage of those BCs (which seems to be the case).


To the OP:  if you are going to be reloading, consider 7mmx47 Lapua, 7mm creedmoor, 7mm GPC, or even .284 win.  The first three will fit standard mags, and can all be made by easily necking up the parent and will do everything the 7mm-08 will but with less powder and a shorter cartridge length which gives more room for longer projectiles.  The .284 win is a more custom build but a few companies do it, and you can get close to 7mm Mag ballistics with it.

Also the main reason to go 7mm is that it has the highest BCs of anything an AR-10 can spit out (with perhaps the exception of a 300WSM with the 208 amax) while maintaining high energy on target.  It has little to do with recoil or any of the rest of the nonsense some folks are spouting off ITT.


If you can go 20in+ with your barrel and energy on target isn't a huge concern you might want to check out the 6mm cartridges like .243AI, 6mm Creedmoor, 6mm XC, etc, that seems to be what most 1000-ish yard competitors are using right now.

I built a 7-08 AR and REALLY like it. Ballistics are just what I like.You will not be sorry.

Trivia:
The British Army did extensive testing on the optimum rifle caliber and came up with 7mm, twice.  Once in 1912 and again in 1946.  The US also did a long study on the optimum rifle caliber and came up with 7mm in the late 1920s, then again at the end of the century.  In 1938, the Germans studied reduced power cartridges for what would become the MKb 42, the preferred diameter was 7mm.  In 1908-13 the Canadians developed a 7mm military round.

The 7mm diameter bullet probably holds the record for having been studied, found best, then for one reason or another, not adopted.

Been a 7mm-08 fan for more @ 20yrs:





BUTT!!! if I was going 7mm and whispering "my precious" over the various BC pill options...

I'd sure as da-da-damn go 7mm Creedmoor.

There are reasons why you should go 6mm CM over 243Win in an AR-10 and it applies equally as well in 7mm.

If you ain't going to do the 7mm right in an ARMALITE GenII mag while going ga ga over BC numbers,
then do the right thing and just go 6.5mm CM.

The 7mm offers better BC for the same bullet weight and is easily capable of delivering the same weight at the same velocities for the same case volume and same max chamber pressure.  .260 Rem does offer better BC, but at reduce bullet weight, or reduced velocity.

My 7mm08 will be used for punching paper and to hunt with. Therefore I tend to lean towards the larger 7mm bullets. Honestly the difference between the 6.5mm and 7mm is so insignificant that who cares about a few inches more drop. As long as your dope is right you should have no problem with either to reach out at long range. That 142 grain Accubond in the 6.5mm looks like mean bullet though, but I doubt you could fit it in the mag of an SR-25.

Bullet Comparisons Heavy for Caliber

Berger 6.5mm Bullets

140 gr Match VLD Target - BC - 0.612

Berger 7mm Bullets

168 gr Match VLD Target - BC - 0.617

6.5mm Nosler Bullets






7mm Nosler Bullets