I was planning on purchasing an upper to build another AR in an alternate caliber.  I was trying to decide on one from the following categories for a sporting/target rifle:

1) The .50 Beowulf or the .458 SOCOM.
2) The 6.5 Grendel or the 6.8 SPC.
3) The .338 Spectre or the .300 Whisper.

The factors I was considering are:

1) Availability and cost of factory ammunition.
2) Availability and cost of upper.
3) Commonality of magazines to 5.56mm.
4) Magazine capacity.
5) Disadvantages, benefits, and effectiveness of the different calibers.
6) Likelihood that the caliber will be available in 20 years.

Any feedback from someone who owns several ARs in the aforementioned calibers would be appreciated.  

i went with .50 beo.

From reading the .50 Beowulf - .458 SOCOM thread it sounds like the .50 would be the better option for a large caliber due to ammo availability.  A complete Alexander Arms .50 Entry Rifle only runs around $980.

Between the 6.5 Grendel - 6.8 SPC, it sounds like the 6.5 would offer increased range over the 6.8 SPC with close to the same terminal ballistics under 300M.  However it appears there are more uppers  as well as ammunition currently available for the 6.8SPC ($999.00 for a DPMS Panther 6.8 SPC.  What's with the $2700 for a M468?).  I belive both the 6.5/6.8 will require some modification to AR-15 mags (or new mags).

I have no familarity with the 300 Whisper or the 338 Spectre.  The reduced recoil/noise of the sub-sonic rounds would be nice however the ammo may not be as available.

I may buy an Alexander .50 Entry and wait until more 6.5 uppers are available.

Quoted: From reading the .50 Beowulf - .458 SOCOM thread it sounds like the .50 would be the better option for a large caliber due to ammo availability.  I would have to disagree with you here.  The sheer number of different 458 bullets available is huge, while the number of 50 bullets can easily be counted without taking ones shoes off.  As time goes on, I certainly think that the 50 beowulf will have a better selection, but I would seriously doubt that it will ever be on par with the 458 caliber bullet selection.  A complete Alexander Arms .50 Entry Rifle only runs around $980.   Between the 6.5 Grendel - 6.8 SPC, it sounds like the 6.5 would offer increased range over the 6.8 SPC with close to the same terminal ballistics under 300M.  However it appears there are more uppers  as well as ammunition currently available for the 6.8SPC ($999.00 for a DPMS Panther 6.8 SPC.  What's with the $2700 for a M468?).  I belive both the 6.5/6.8 will require some modification to AR-15 mags (or new mags). I have no familarity with the 300 Whisper or the 338 Spectre.  The reduced recoil/noise of the sub-sonic rounds would be nice however the ammo may not be as available. I may buy an Alexander .50 Entry and wait until more 6.5 uppers are available.

I didn't mean variety of bullets, I meant availability and price of factory ammunition.  

334 grain hollow point .50 Beowulf is available on Midway for $220 for a box of 200.  Cor-Bon has 20 rounds of 300 grain JHP .458 SOCOM for $45.17.

I liked the RRA .458 SOCOM CAR A4 at $1065, which is about the same price as the Alexander Arms .50 Beowulf Entry.

Quoted: From reading the .50 Beowulf - .458 SOCOM thread it sounds like the .50 would be the better option for a large caliber due to ammo availability.  A complete Alexander Arms .50 Entry Rifle only runs around $980. Between the 6.5 Grendel - 6.8 SPC, it sounds like the 6.5 would offer increased range over the 6.8 SPC with close to the same terminal ballistics under 300M.  However it appears there are more uppers  as well as ammunition currently available for the 6.8SPC ($999.00 for a DPMS Panther 6.8 SPC.  What's with the $2700 for a M468?).  I belive both the 6.5/6.8 will require some modification to AR-15 mags (or new mags). I have no familarity with the 300 Whisper or the 338 Spectre.  The reduced recoil/noise of the sub-sonic rounds would be nice however the ammo may not be as available. I may buy an Alexander .50 Entry and wait until more 6.5 uppers are available.

I have both the .50 Beowulf and the 6.5 Grendel; like them both.  Ammo by Alexander Arms is available for both and soon (about May)  Wolf Performance ammo in brass will be available for a lot less than factory ammo.
www.wolfammo.com/Wolf_Ammo_Catalog2006.pdf

I chose the .458 socom because in all my research I never saw where anyone had to modify the mags to work.  I've read where quite a few people had to "open the feed lips" on their mags.  I want to be able to use any mag that I own for either cartridge.  But I know there are lots of folks that use .50B who say it feeds just fine as is - I just didn't want to chance it.

I also got the .458 cuz the TJ logo is COOL!!!!!!!

And bullet selection, because I do reload.  I have faith that the price will come down at Corbon, and that others will soon start making it too.

Mine will be in wednesday......... I CAN'T WAIT!!!!!!!!!


I thought that the 6.8 was supposed to feed well from stock mags - just with less capacity?

Magazine commonality would be important in making my choice.  I thought the 6.8 and 6.5 were supposed to work with .223 magazines, however I believe there are 6.8 specific mags available from PRi.

I may go with the RRA .458 and wait for a 6.5 Grendel from Patriot Ordnance.....

My 458 had been easy to reload for and there are a ton of bullets.  I use the Brownell's 223 mags with only one jam to date.  (last round and it was a 7.62 mag by mistake)

Quoted: I was planning on purchasing an upper to build another AR in an alternate caliber.  I was trying to decide on one from the following categories for a sporting/target rifle: 1) The .50 Beowulf or the .458 SOCOM. 2) The 6.5 Grendel or the 6.8 SPC. 3) The .338 Spectre or the .300 Whisper. The factors I was considering are: 1) Availability and cost of factory ammunition. .50 B - ammo right now a lot cheaper, Wolf will make it even more so, limited variety of loads due to mentioned smaller selection of projectiles.  Ammo likely more readily found .458 S - ammo is costly, talks with CorBon underway and at least two other makers are expressing interest to make it.  Due to plethora of bullets out there, more loads feasible.  At least one custom loader getting set up to load what ever you want (within reason) 6.5 Grendel ammo to be offered by Wolf, making it cheap, however, 6.8 ammo becoming more available.  Not sure how pricing stacks up.  Suspect 6.8 might be more easily found .300 W ammo can be had from CorBon in two loads IIRC.  Not cheap.  338 S from Reed's ammo in 10 or so different loads, priced less than some factory ammo I have seen in yellow and green boxes.  Neither will be as cheap as bulk surplus.  Order from Reed as he is only source right now. 2) Availability and cost of upper. With RRA in the game, .458 and .50 uppers are similarly priced.  Hard pressed to find totally custom .50 uppers, with the .458 there are three sources for these.  Have not seen any sources for SBR/pistol uppers for the .50B Several folks making 6.8s and at least 3 places offer 6.5s.  Have not checked prices, but most 6.8s seem to be "cookie cutter" whereas most all 6.5s seem to be custom. .300 W uppers can be found several places under different names (300 Fireball, 300-221)  Priced competitively with 6.8 and .223 uppers.  .338 S for now from only one source, cost depends on what you want installed.  All uppers match grade barrels due to twist rate needed. 3) Commonality of magazines to 5.56mm. .458 designed to be used with stock 5.56 mags.  Not aware of any that don't work and some custom stuff in the works.  50 B have seen reports suggesting minor fitting of mags (lips) but not all the time.  Would appear both about the same I guess 6.8 requires dedicated mags, 5.56 mags WILL NOT WORK.  Aware of two makers (Creative Products and PRI)  6.5 requires dedicated mags, not sure about sources other than AA or CSS .300 W uses stock 5.56 mags.  338 S uses 6.8 mags (see above) 4) Magazine capacity. .50 B and .458 S share parent case, so mag capacity identical, 30 round 5.56 will hold 10 6.8 and 6.5 require dedicated mags.  Seen different versions for both, but IIRC 6.8 has 28 max and 6.5 has 25 max .300 W using stock 5.56 mags can use ANY in that caliber, so aside from 30 rounders, Beta drums are an option ... for the 338, stick with the 6.8 mags and you are limited to 28 for now 5) Disadvantages, benefits, and effectiveness of the different calibers. I don't think I have enough time or space to write all of this, I would recommend the various FAQ for the differnet calibers.  I can give the 10,000 ft overview .50 and .458 are kissing cousins, whatever you hit with either won't know the difference.  Only big difference I can think of is due to some of the projos available for the .458 that handloaders might have more options to them.  Also, 600 gr subsonic factory load for those that need/want it 6.8 v 6.5 - I ain't EVEN sticking my finger in that hornet's nest.  There are whole websites dedicated to that discussion. .300 W and .338 S.  Both are meant for specific application: subsonic suppressed work.  300 W has the advantage of stock mags and HUGE bullet selection.  For the INTENDED application, the 338 S has 10% larger bullet diameter and 25% heavier bullet, meaning more energy on target and gel tests have shown it will tumble AND penetrate.  If you can wait a few weeks, we have a new round in the works to compete with the .300 6) Likelihood that the caliber will be available in 20 years. I haven't a clue ... but I would venture that 20 years from now, components could be found provided everyone does their duty and elects the appropriate people into and OUT of office.  Other than that, the 6.8 MIGHT be more commonly found at that time in the future but who knows. Any feedback from someone who owns several ARs in the aforementioned calibers would be appreciated.

Thanks for the great info.

The .458 would be more attractive if the ammo price came down to the .50 Beowulf range.  The .458 and the .50 Beowulf appear to be suited for hunting or "home defense,” however magazine capacity, range, and ammo availability and price seem to be limiting factors in regards to tactical employment.  (Does anyone know of any actual military or law enforcement application of either caliber?)

I can't see the 6.5 or 6.8 being selected as a law enforcement patrol rifle cartridge (perhaps the 6.5 for sniper rifles) due to concerns of range and lethality.  Does anyone know of any large PDs that have purchased patrol rifles in either caliber?  I also believe the military (aside from special operations) will stay with the 5.56 due to availability of magazines and existing ammo stocks as well as commonality with allies.  It sounds like the 6.5 Grendel would be the better than the 6.8 due to its greater velocity/range and similar terminal effects.

The .300 Whisper and .338 Spectre appear to be well suited as specialized cartridges for larger caliber, short-mid range, and suppressed rifles.  They also would probably work well for law enforcement due to the reduced recoil, noise, and range; however I couldn't see either one being utilized with the limited availability of rifles and ammunition.

As alternates to the 5.56/.223 for personal use, the .458 SOCOM in a 16" barrel with an EOtech would be nice for its lethal effects in CQ; and the 6.5 Grendel in a 20" barrel with a 1-4x scope would be nice for its increased range.

Quoted: Thanks for the great info. The .458 would be more attractive if the ammo price came down to the .50 Beowulf range.  The .458 and the .50 Beowulf appear to be suited for hunting or "home defense,” however magazine capacity, range, and ammo availability and price seem to be limiting factors in regards to tactical employment.  (Does anyone know of any actual military or law enforcement application of either caliber?)Mag capacity is being addressed, give it about another 2 months.  Same with ammo price for the .458.  There is documented military use of the .458 and .50, but I am not at liberty to give details.  In some of the threads in this forum, you may note that some of the posters allude to their employment and use of these calibers.  There have been articles written as well and at least one picture of a .50B in A'stan has been shown on this website I can't see the 6.5 or 6.8 being selected as a law enforcement patrol rifle cartridge (perhaps the 6.5 for sniper rifles) due to concerns of range and lethality.  Does anyone know of any large PDs that have purchased patrol rifles in either caliber?  I also believe the military (aside from special operations) will stay with the 5.56 due to availability of magazines and existing ammo stocks as well as commonality with allies.  It sounds like the 6.5 Grendel would be the better than the 6.8 due to its greater velocity/range and similar terminal effects.Several PDs going to 6.8 from what I have heard.  Mags in the 6.8 are shipping by the pallet so someone sure is using them.  Similarly, 6.5 articles aplenty with mention of who might be using them The .300 Whisper and .338 Spectre appear to be well suited as specialized cartridges for larger caliber, short-mid range, and suppressed rifles.  They also would probably work well for law enforcement due to the reduced recoil, noise, and range; however I couldn't see either one being utilized with the limited availability of rifles and ammunition.We have sent several barrels in 300 Fireball and 338 S to end users who have put them to very hard use.  Again, cannot discuss who.  The 300 W and 338 S are being tested out to 500 yards ... but initial specs were for "up close and personal" rigs As alternates to the 5.56/.223 for personal use, the .458 SOCOM in a 16" barrel with an EOtech would be nice for its lethal effects in CQ; and the 6.5 Grendel in a 20" barrel with a 1-4x scope would be nice for its increased range.

Marty, thanks again for the great info.

I imagine that various calibers would see use amongst special operations.  A silenced .458 SOCOM, 50 Beowulf, 300 Whisper, or .338 Spectre would make nice short-mid range take-down weapons.  

Either the 6.5 or 6.8 would be an improvement over the 5.56 as an assault rifle cartridge; however cost and logistics rather than effectiveness will probably govern any US Military decision to replace the 5.56 entirely.  

Similarly I could see the 6.5 or 6.8 being used by Tac Teams, however many administrators with little patrol experience would be very apprehensive putting a more lethal bullet in the hands of the average officer.  A large department I know of was offered free surplus M4s from the Army however they were turned down due to the cost of ammunition and training.  The officers in the department that have AR-15s are forbidden to use anything other than 2 x 20 round clips (Colt factory only) loaded with 50 grain bullets.  If they can't get M4s I can't imagine M468s.

While on the M468 subject: Does anyone know why it's so expensive?  Is it the ARMS rail, or is Barrett quality really that good?  Are there any other viable 6.8 uppers besides Barrett and DPMS?

In closing, it appears that there isn't enough objective testing comparing ARs chambered in  6.5 and 6.8 as compared to 5.56 and .308 to say which is the definitive cartridge.

In regards to a replacement for the Army's M4: I could see the greater lethality of the 6.8 SPC being an improvement however the cost and the logistics involved will probably prevent it from being selected.  

The greater range of the 6.5 Grendel would be nice for a designated marksman weapon, however as a general assault rifle cartridge for engagements out to 300M it's comparable to the 6.8.  

I can't see where a 6.5 Grendel or 6.8 SPC would be desired for hunting when there is the .308 AR-10...

The best course of action seems to be a wait and see what rifles and ammo are offered in each caliber and whether or not either is accepted by the military.  Until then stick with the 5.56 for a general assault rifle or the .308 for hunting/marksman.  

For the price of a Barrett M468 you could buy both an Armalite AR-10 and a Colt MT6400C!