Swear by it or at it. The only options.
The Maximum may also do well with H110/296. Also faster than the mentioned powders and often a "best accuracy" powder in magnum handgun loads.
Let me suggest another possible problem: The 7 1/2 is a magnum level small rifle primer. Board member M1 Garand sent me some Charles Petty articles one time that showed a .223 Rem load going from 3150 fps with the Federal 205 primer to 3300 fps with the 7 1/2. He also got the most extreme velocity spread with it among the primers he tested, despite its BR label. So it's pretty warm and not especially consistent. In the small fireball case and in the Maximum case due to the bullet having a lot of surface area relative to the case volume, that primer is stiff enough to unseat bullets before the powder gets burning. That causes erratic velocity extreme spread. The even smaller .22 Hornet is famous for having the bullet unseating problem both because of its capacity and thin neck. I would go to the Remington 6 1/2 (
EDIT: Not a good idea for max Fireball loads: see Rocky's comment and my follow up below this post) which is made specifically for the Hornet pressure range and is milder, or to the Federal 205 or 205M, also milder, and you might even look at a standard small pistol primers for the Maximum if the powder is filling the case well.
Still another common problem is underseating primers. Benchrest shooters are big on the feel of the primer anvil feet just touching down on the bottom of the primer pocket as best for primer seating, but two bits of information I have contradict that. Both come from the Precision Shooting Reloading Guide (Precision Shooting, pub., 1995). Each chapter has a different author. One author cites Federal as stating optimal seating is 0.002" inches compressed beyond the touchdown for small rifle primers and 0.003" beyond for large rifle primers. Another author, quite independently mentions that he has always got his most consistently small extreme spread from seating primers "hard". That by doing so he has always been able to get a rifle down to about 10 fps ES.
What is going on there is that the primer has its priming compound in the form of pellet that is between the primer cup and the anvil. The thickness of the pellet between the two is called the bridge. There is an optimal degree of pre-loading required to maximize its sensitivity and minimize ignition delay after the firing pin strike, and that is accomplished by "setting the bridge", which is to say, putting an optimal amount of compression or squeeze (the pre-load) on the pellet between the cup and anvil.
When you've been at the loading thing for awhile, you'll notice that different lots of primers have the feet of their anvils sticking up more in some instances than others. That makes me doubt that even Federal's advice can be consistently relied on. Rather, I expect it is an average truth. Commercial ammo, and Federal's is often quite good, is made simply by seating the bottom of the primer cup a fairly consistent 0.003" to 0.005" below flush with the back of the case. That 0.002" spread is because primer pockets are not all the same depth. If you uniform your primer pocket depth to maximum, the higher number should apply. I suspect that primer position approach will be your best bet most of the time.
If you have purchased a large lot of primers, you can also use a tool like the Markel priming tool with its dial indicator option added. That will let you feel touchdown and measure some specific number of thousandths seating depth beyond that. This will let you find what number does best with your primer lot? Much trouble, but interesting to experiment with.
Forster's Co-ax press has a unique primer seater that forces the primer 0.004" below flush by means of a stop on its primer ram. I know of no other, not even Forster's own Co-ax bench seating tool, that does that. If you have the Co-ax press, go to the bother to set the primer seater up. You can seat your primers with it to see if an improvement occurs?
If your powder charges are not filling the cases well, you can get pretty big velocity spread just from the powder position shifting in the case. Try firing ten shots after first tipping the muzzle up to get the powder over the flash hole, then lowering it to the bag slowly to leave it there before firing. Then try muzzle down for ten shots. See if the mean velocity changes measurably?
With spherical and fine grained propellants, ignition is more difficult that with coarse stick propellants because the spaces between the grains are smaller and harder for the hot gas of the flame front to move through. It's kind of like those porous stone filters for fish tanks: coarse lets the gas flow through more easily. As a result, the one year I ran Accurate 2520 in my M1A, I found I could cut group size 40% by deburring the case flash holes. Basically, anything that improves ignition tends to help those powders. You might get a Sinclair deburring tool if you don't have one and see if it makes a difference for you?
I would be remiss if I didn't point out that velocity extreme spread by itself doesn't affect 100 yard accuracy a lot in all guns and loads. Charles Petty's erratic .223 load was the most accurate he had. I think that's because it averaged around a barrel time sweet spot and that increasing his fixed charge with the milder primers to bring them up to the faster load's barrel time would have done the same thing or better for him, but he didn't do that experiment. I'm just pointing out that even 100 fps ES amounts to vertical dispersions of only a couple or three tenths of an inch at 100 yards. It isn't until you get to 300 yards that you start to measure it in inches. Instead, it is the timing with which the bullet leaves the muzzle that seems to have the most effect on accuracy from a load. I recommend, if you haven't done so already, that you look at and read through Dan Newberry's
OCW site. Whether looking for an OCW load or not, his round robin approach to firing test loads is an excellent way to narrow the choices down.
Finally, it has to be mentioned that the best load in the world won't compensate for a gun that isn't in best shooting condition. One of the authors of the PS Reloading Guide said he doesn't like the concept of a pet load because it suggests that if you haven't lapped your bolt lugs, re-crowned your muzzle, bedded the action properly or, in some instances, firelapped the barrel to remove constrictions or irregularities, that the load will somehow make up for those mechanical inconsistencies. It won't. You can find a "best" load for the gun, but whether or not that will be satisfactory to you depends in large part on those other mechanical factors. Newberry's round robin will help you find what is best in your gun. Once you have that, you can tell whether or not you need to start looking at those other factors.
Good luck with it, and have fun!
