320pf

If the "finished" length is 16 inches including the comp/brake, then you are talking about a barrel less than 16 inches. Or you are talking about a 16 inch barrel plus the comp/brake? Either way it does not matter. If you are going to run a 16 inch barrel or less, you should go with a carbine length gas system. As far as port diameter, start with a small port (about 0.060-0.065 inches) and increase in ~0.002 inch step if necessary... until the rifle cycles reliably. Adjustable gas blocks are just one more thing that can go wrong/bag during a match. 320pf

This is readily corrected by seating the bullet deep enough into the case so that the magazine rib rides on the bullet ogive where the diameter is approximately the same as a 223 case neck. (see this figure) This information is a bit dated and is based on the experience people had with rifle builds that had the gas port in the standard carbine position. With the standard carbine position, the gas port needs to be about 0.1-to-0.12". With this set-up you will need an adjustable gas block if you want to be able to shoot both super-sonic and sub-sonic loads. You can build a 300-221 aka 300 whisper that can shoot both super-sonic and sub-sonic loads without an adjustable gas block and uses a standard rifle buffer and recoil spring. It is all dependent on the location and diameter of the gas port. The best location for the gas port is the standard pistol position. A port diameter of about 0.80-to-0.85" seems to work best. I like to start with the gas port at about 0.73" and open it up so that the rifle will cycle 150g sub-sonic loads. As far as how sub-sonics work on game cas if correct. The sub-sonic load will not expand... They do their damage because they are sub-critically stabilized when shot from a 1:8 twist barrel at sub-sonic velocities and tumble upon impact. The most effective sub-sonic bullets are >200 grains. Super-sonic loads will expand and work well in game. (see this discussion thread): http://www.quarterbore.net/forums/showthread.php?t=1768 320pf Added after original post: 221 Fireball brass is hard to find and when you can fine it, the cost is too high. I make all of my brass from 5.56/223 brass. You will want to make sure that your barrel/chamber is cut with the an up-to-date reamer that will allow you to use 223 brass. These reamers have a slightly larger neck diameter to accommodate the thicker necks that you get with 223 brass. I am not too particular about my brass. It is mixed brands and I can routinely get my Noveske barrel to shoot < 1 MOA groups. Right now, one of the best 300-221 fireball barrels are being made by Noveske. These are other quality barrels out there but I am not familiar with all on them. I would avoid Modlel-1. They make OK blaster barrels. But the gas port on these barrels is in the carbine position, so you might have to work on getting the rifle to cycle reliably. In addition, the specs on the bore diameters is a bit greater than I like.

Interesting. I won't suppress well though I just got an upper from the guy that came up with this cartridge. I have been talking with him for several months now and he is a pretty sharp wildcater and knows his stuff. I was able to push 147 grain Win. FMJBT to about 2200 fps. It looks like the pressures were OK. If you are looking for a cartridge that uses standard mags, and bolt/carrier this round has some very interesting potential. It looks like a 20-inch barrel will push a 125 grain bullet to major power factor (2560 fps). If you want to shoot mainly sub-sonic load, however, the 300 Whisper aka 300-221 fireball is the way to go. Here is a good article on the virtues of long range shooting with high Ballistic Coefficient sub-sonic loads: http://www.lasc.us/RangingShotLongWhisper.htm 320pf

That was me the 2007 SMMG and it did not "puke" on 8 of 10 stages. First, the 2007 SMMG was my first outing with the 300-221 fireball. The load that I work up for that match was 20 gr H100 pushing a 125 gr speer TNT at 2350. That load ran fine in NY at ~ sealevel and 35-45 deg. F. The same load at 2100 ft and 80-90 deg. F. blew primers after about 3-to-5 shots. It puked on my first long range stages and boy did it puke. It blew the primer and pulled the rim off the case and left the case stuck in the chamber. major puke on that stage. I shot the rest of the first day using my sub-sonic ammo and the gun ran fine with the sub-sonic ammo on all of the close rifle stages. I did not shoot all that well because I was trying to figure out if there was a way to fix my ammo problem. One the second day I keeped the super-sonic ammo on ice but that did not work. I tried the ammo again on another stage and the load blew primers stuck cases etc.. again Puke number 2. The gas blowing back into the upper receiver heats up the ammo pretty fast. So I had to shoot the rest of the match using my sub-sonic ammo of which I just had enough to shoot the whole match with. Live and learn. So the next long range stage was not pretty. I later found out that H110 is pretty temp sensitive. So I changed powders to W296* and dropped the load to 19 gr and I get 2230 fps from this load and no blown primers. After some more serious load testing and development. My brother came out from CA and we shot a local match here in NY/NJ with the 300-221 fireball rifles and they both ran perfect. Then in 2008 my brother and I shot 300-221 fireball rifles at the 2008 SMMG and both rifles ran fine there as well! (*I have been told that W296 and H110 are the basically the same powders but W296 shoots tighter groups in all of my 300-221 rifles) Yes shooting a wildcat cartridge in a semi-auto is a bit more difficult. Most of the heavy lifting for using a 300-221 fireball in 3-gun match has been done and now the rifle run fine. If you what to see two of the rifles that I have built check here: http://www.quarterbore.net/forums/photopos...o.php?photo=367 320pf

Yes, I have built about six of them... And I am the shooter that Dan Sierpina is referring to in his post. My brother and I both shot 300-221 fireballs this spring at the Superstition Mountain mystery 3-gun in AZ. My brother did pretty well, I have some issues with my shot gun. Oh well next year. I found that the best way to shoot the 300-221 fireball in 3-guns matches is to bring two different loads to the match. For all the close in stages, I shoot sub-sonic loads. I like 165g at 1050-1080 fps. This make the minimum pf (150) and has about 1-2 ft-lbs of recoil compared to about 4-to-5 ft.-lbs of recoil for a identical rifle in 5.56mm. For the long range stages, I shoot 125g bullets at 2230-2250 fps. The secret is to sight the rifle in to be 4-inches high at 100 yrds for the super-sonic loads. The super-sonic loads zero cross is at 30 yrds. and 215 yrds. This load is 10-inches low at 300... so if you hold a high 12 0'clock position on a 10-inch plate... it is pretty easy to make the hit. The sub-sonic load starts about 2-inches below point of aim (POA) at the muzzle. The POA is right on at ~35-40 yrds. By 80 yrds the bullet is about 4-inchs below POA at 80 yrds. If you set up your rifle correctly, No. I use a standard rifle buffer and spring in both of my lowers and can use either with my 300-221 fireball uppers. I use standard unmodified mags and yes the are reliable. No. An adjustable gas block is not required if you set up your rifle correctly I have a Noveske 16-inch barrel, gas port in the pistol position. Three Olympic Arms barrels One has the gas port in the "Olympic" pistol postion (~0.5-inches closer to the breach than the standard pistol position). The other has the gas port in the carbine position and the third has gas port in both positions and can be configure either way... Depending on which port you plug with a set screw. All of my rifles shoot 1 MOA or better. The Noveske barrel will shoot 0.6 in groups at 100 yrds. With a 10-inch barrel you will lose about 200-to-250 fps. With my 16-inch barrels I can push 175 and 180 gr bullets to ~1850 fps. This make major pf. I can push 165-168 gr bullets to about 1950-2000 fps. But I have not had time to really check how reliable this load is. I have tried reformed 221 fireball brass but I have found that 223 brass works well and only requires cutting the brass to length (~1.36-inches) and then run it through the resizer die. I hope this helps and good luck 320pf

You can be very competitive with a Ruger Mini-14. But you will need to spend the money to accurize it. My brother lives in CA and shoots an Accurized mini-14 and is very competitive with it. The rifle was built by Accuracy Systems (www.ruger-mini-14-firearms.com). Check their web site if you are looking for more information. 320pf

I post under the same name (320pf) on arfcom [sic] (AR15.com)... the connection is pretty obvious. So what you the point of the rest of your comment(s)? 320pf

No Probably. I know that I pick up my wildcat brass. But I do not go crazy trying to find every shot round. The officials at "lost brass" matches usually do not have any problems with me picking up my wildcat brass because it is of little use to anyone else. 320pf

If you push the 6.5 Grendel to max pressures to make major PF you are likely to experience premature bolt failures. This problem has been debated to death on AR15.com. The 7.62x39mm in an AR15 platform will also has the same problem if you push the pressures high enough to make major PF. The problem is two fold. First, the bolt face has to be opened up up to accommodate the much larger case head of both of these cartridges. This removes some of the support material from the lugs. Second, the interior area of the case head is larger with the 6.5 Gren. and 7.62x39mm therefore there is more thrust on the bolt for any give pressure. The standard 5.56 NATO generates between 6000 and 7000 lbs of thrust on the bolt at 55000 to 60000 psi chamber pressure. The 7.62x39mm and the 6.5 Grendel will generate about 7000 to 8000 lbs of thrust on the bolt at 50000 to 52000 psi chamber pressure. If you push the pressures up to ~60000 psi chamber pressure the bolt thrust jumps to about 9000 lbs. Besides much more recoil, the other major disadvantage with these rounds is that the magazines only hold 25 rounds instead of 30. The way USPSA 3-gun is scored and the use of steel at distances of 100 yrds or greater, there is not much advantage to be gained shooting major rifle. I have been down this road... unless they change how 3-gun is scored, shooting major is not worth it. "The 6.8 will push the 115 to 2800fps from an 18" barrel. act." I have seen this claimed on several blogs...I think that this load is way off the "reservation"! The max 115gr load listed in the most recent Hodgdon database (listed for a 24-inch barrel) is 28.2 gr of H322 (compressed) generating 53300 psi and pushes the 115 gr bullet to 2608 fps. The claim that an 18-inch barrel is 200 fps faster is... well dubious. I believe that people might be getting these velocities but they are way over max pressure! Yea yea, I have also heard all about the three groove barrel and 1:10, 1:11 twist and the "improved" chamber etc... But it all sounds too special to me! 320pf

I think that it is only 0.308" caliber bullets... Not 308W. I have shot Major with 155 gr bullet out of a 20-inch barrel in 300-221 fireball aka 300 Whisper. 320pf

The title of the thread is "the 6.8 major and more" My question(s) is the "and more" part of the thread. Any way the point that I was trying to make is that: Until/unless the USPSA changes the way they score rifle matches the 5.56mm/223Rem will dominate the competition because there is not enough scoring advantage in the difference between major and minor rifle. I started a thread several months ago suggesting that USPSA consider changing the way major and minor rifle are scored. I could go over my idea again, but it is a bit off the subject of this thread. Oh well what the the heck... here it is again. Several "outlaw" 3-run matches score like the smm3gun match. One "A" hit or two any where else for time. I suggested that: Minor rifle: requires a single "A" hit... scored as two "A" hit and time for a hit-factor or two hits any where and scored like a regular USPSA. If a shooter feels confident that they got the "A" off they go to the next target. If the shooter misses the "A" and gets a "C" the score is Charlie-Mike and gets the appropriate penalties. If they take the second insurance shot, they get what they shoot. For example an "A" and a "C" hit are the scored as an Alpha-Charlie Major rifle requires a single "C" hit or better and is scored as either two "C's" or two "A's" depending on the actual hit. If a shooter feels confident that they got the "C" or better hit off they go to the next target. If the shooter misses the "A" or "C" and gets a "D" the score is Delta-Mike and gets the appropriate penalties. If the shooter takes the second insurance shot hey get what they shoot. Just like minor rifle. This scoring system gives credit to Speed, Power, and Accuracy.

ar15performance, Please explain the advantage of the 6.8 PSC in 3-gun? 1) Using a brass catcher (3 Bucc) in a match is a nonstarter. So this does not really offset the extra cost of brass. 2.) You acknowledge that the bullets cost more and then claim that you use "half as much powder". The loads that you list in your first post 27.5gr-to-30gr are not "half" of what you would use in the 5.56mm. In fact the two cartridges use about the same amount of powder. This is easily verified any reloading manual that you check. 3.) If a shooter goes with a 6.8SPC in addition to the barrel/upper that they have to buy, they also have to buy magazines 6.8SPC magazines are more expensive than 5.56mm mags. (I like to bring least 4 or 5 for a match). I also like to bring a spare bolt and carrier to a match that I can take from spare upper that I bring. 4.) Most 6.8SPC magazines hold only 25 rounds... which can translate to more reloads= more time. 5.) USPSA generally shoots steel at distance. So there is not scoring advantage there. 6.) In the close-up stages the minor (5.56mm) rifles be will faster with the second follow-up shot. Check the James Tarr article on the 6.8SPC in the May/June 2005 issure of front-site. He found his times were about 5-percent slower and at the time he tested the 6.8SPC, he was shooting a PF of only ~306. I have done a speed drill tests with a rifle that makes a 325 PF and I found that a is about 15-percent slower than the 5.56mm. I have verified the 15-percent speed hit/penalty with two other shooters, one a grand master level shooter and the other an A level shooter. 7.) Shooters that go with the 308W usually shot "Heavy Metal" (HM). The 6.8SPC does not qualify for HMN because the bullet diameter is only .277 not .308. The upshot of this is that you are not going the be competing with the 308W shooters but the 5.56mm shooters, who will be faster then the 6.8SPC. So bottom line until/unless USPSA changes the way they score rifle there is NO advantage to shooting major. I do understand the fun/cool factor of shooting a different cartridge that the rest of the pack... and that mat be reason enough! 320pf

I shot the rig this weekend and it did not bounce around. Also after I read your post, I took the gun and really shook and boucnced it around and it did stay put. Yes the reticle is magnitied. I think that it actually looks better through the magnifier than without it. If you look through the magnifier for a long time, however the central dot appears to elongate in the horizontal. Binking your eye returns it to a nice dot. Other people have made the same comment/observation. When I tried the site system out this weekend I drew a ~1.25-in. open black dot on the target and the 1 MOA dot fit nicely within the open black dot. Like I said in my post... I was able to shoot 0.75-in groups all day long with it so I think that the optical clarity of the sight and reticle are easily sub MOA. 320pf

Well I finally got a chance to take my AR15 in 300-221 Fireball out to the range on Sat. to try out my new xmas present, a L3 EOTech 3X magnifier. All I can say is that it works very well. If you are using a EOTech Holographic Weapon Sight (HWS) one of the magnifiers is a must have. I have been using an EOTech 510 for about 3 years now. It is a great sight for in close shooting out to about 100-125 yrds. My EOTech 3X magnifier is mounted on the "flip to side" mount and easily extends the range out to 300 yrds. With the 3X magnifier I was able to really see how good my Noveske barrel is... Both me and my shooting partner were able to shoot 4 shots into 0.75 inch clover leafs. The fifth shot, however, always went about an inch high or low. I think that when the bolt-carrier group cycles differently on an empty mag. So if you have an EOTech Holographic Sight I would suggest taking a look at the magnifiers 320pf

As I stated in my post, I use 30 caliber and beyond when I go hunitng but that is not the point of practical shooting since we have not yet approved a lion, elk or leopard target. If heavy metal should get extra credit in 30 caliber, how many extra points should I get for a "A" zone using one of my 40 caliber rifles or 50 caliber rifles? You do get a scoring advantage using a larger caliber "hole-punch" If you are shooting a 40 cal. bullet you can be 0.390 inches outside of the A-zone and still get the "A" points. 320pf