450 reloads extreme velocity spread

[teamja2]

Shot my reloads for the 450 bushmaster today and have incredible velocity spreads all over the map. I am thinking either powder or crimp related but wonder your thoughts. Day was hot, 85 - 95 and sunny, light south wind. 5 rounds in each magazine, no noticeable signs of bullet movement after cycling rounds towards the bottom of the magazine through the gun and inspecting them. Rifle is 16"

1x 450 hornady brass full length sized in hornady dies
Remington 7.5 BR primer
Hornady 225 FTX bullet
w296 powder
crimped using factory die to .475
2.13 OAL
Powder charges weighed on RCBS balance beam scale - reloads were not mixed and shots are in order fired and no rounds were allowed to sit in a hot chamber

Factory FTX load - 2109, 2109, 2143, 2133, 2099 - 1 1/8"
36 - 2048, 2002, 2029, 1799, 1733 - 1 5/8" The 2 that were 17xx fps sounded noticeably different
36.5 - 1872, 1792, 2035, 1841, 1804 - 1 3/8"
37 - 1823, 1819, 1902, 1834, 1784 - 3 1/4"
37.5 - 1924, 1963, 2073, 1870, 1932 - 1 1/4"
38 - 1984, 2154, 2109, 1904, 2051 - 2"

I'm have loaded for some years but can not explain this.

[Hoot]

Some may differ with me on this, but 296 is a little slow for the 225s. It relies more heavily upon a stiff crimp to hold them back alot so that it can get really cooking. If I were using 296 and the lighter bullets, I'd be inclined to add a stab crimp to the rear cannelure as well. I don't use 296, just relying on burn tables. My experience has been that using the taper crimp only, this caliber has wide velocity variation compared to shouldered calibers I reload for. Again, from my experience, it has little bearing on groups at 100 yards. My tightest group had a velocity SD of something like 45. On the flip of that coin, I've gotten single digit SDs with double stab crimps and poor groups at 100 yards. Go figure...

Hoot

[teamja2]

Thanks - a few follow ups.

Is lil gun a better choice for 225's?

Stab crimp - is this what the modified crimp die I read about used for?

Would w296 be better for the 300's - or what is recommended for the 300's?

Also accuracy wise this rifle / caliber just seems to shoot most anything into a pretty good group - not very fussy.

Ryan

[Hoot]

Thanks - a few follow ups.

Is lil gun a better choice for 225's?

In my opinion, yes.

Stab crimp - is this what the modified crimp die I read about used for?

Yes, a modified Lee .45-70 Factory Crimp Die (not expensive)

Would w296 be better for the 300's - or what is recommended for the 300's?

Ryan

While I can not speak from personal experience, that's typical of what I've read. There is room for overlap though. Think in terms of efficiency. If you load a 225gr with Lil Gun to produce 2150 fps, you throw abut .6gr of unburned powder downrange. With W296, that's 3.7gr (almost 10%). That's work not getting done.

Also accuracy wise this rifle / caliber just seems to shoot most anything into a pretty good group - not very fussy.

Seems that way. If you looking for tight groups, for whatever reason, there are loads in every bullet weight that can be tuned fairly tight. Not always at maximum velocity, but the FTX family expands at modest velocities, so who's to care.

Hoot

[teamja2]

Thanks - appreciate the help.

Ryan

[pitted bore]

teamja2-

Welcome to the occasional frustrations associated with reloading the 450B. If you stray very far from the reloading sheets Hornady prepared, you're likely to encounter a variety of problems. Solving them can be very educational, if you're careful and patient.

Hoot's comments are spot on, and what follows won't add much of substance to what he wrote. I have had some experience with 296, which I recorded on some threads I wrote here two years ago. Other forum mebers have had a lot more experience with it. 296/H110 is slower than Lil'Gun in the 450B. According to the Hornady data sheets, this is true even with the 300-grain bullets that you asked about. For bullets between 240 and 300 grains, the choice between 296 and Lil'Gun will probably be based on accuracy in your own rifle.

Hoot's note about unburned 296 being blown out the barrel is probably based on a computer model, but that idea is consistent with my observations. With lighter bullets and slower powders in the 450B, adding more powder does not necessarily produce more velocity. For a given bullet, primer, etc., with some powders. I found that velocity would increase as more powder was added, as expected. However there would be a plateau reached where more powder did not result in more velocity. In fact, velocity could decrease with the addition of more powder. The "extra" powder was apparently being blown unburned out the barrel.

The variation from shot to shot in velocity reflects the amount of powder burned vs unburned. This may be an almost random effect, depending on position of powder in the case, variation in strength among primers within a lot, variation in firmness of bullet seating between rounds, etc.

The stab/side crimp has helped the situation by slowing the exit of the bullet from the case by a fractional millisecond, to allow the pressure to increase enough to promote a more complete burn. In a sense, a side crimp with lighter bullets is a substitute for the inertia of heavier bullets. (That's my working hypothesis until some data appears to contradict it.

So, as Hoot writes, a shift to a faster powder like Lil'Gun should produce better results with the 225-grain bullet.

If you try it, be sure to post here to let us know whether the advice was good.

--Bob

[Hoot]

Remember, this string of powders all overlap and sometimes hold a surprise. Look at wildcatter's result propelling 200gr XPBs ahead of insane amounts of 296. By all rights, it should have been too slow for optimum results, but the proof is in the pudding. Seversl times now, I've observed a phenomena where when you pack a case plumb full to the point of compression, more complete burns occur (among other things) with powders that should by all accounts, be too slow for optimum performance. I've seen it with vibrated down, fully packed cases using Varget in my AR15 .300 OSSM. By rights, it should be too slow for the 150gr bullets, but the dense-pack is synergistic. When you stumble upon an anomaly that while outside the nine dots, works amazingly well, that truffle makes you feel less blind, if for a moment.

Dancing on the edge brings with it a degree of risk of course. A load that is magical at one temperature, can turn into a disaster when the temps and humidity get like they've been the past few weeks. Approach all of our more outlandish, reported accomplishments with respect for the consequences that can happen if it doesn't go according to our reported experience and always start lower. Sure it costs a little more time and money, but if you can't appreciate it for the safety factor, write it off as opportunity to gain more experience on the trigger.

Hoot

[Texas Sheepdawg]

What about 2400 using the Legendre Crimp?

[Hoot]

What about 2400 using the Legendre Crimp?

2400 lights easy and fast. Too easy and fast. It does not need a stab crimp to hold the bullet back while the powder gets going.

Any one person's experience, while valid, is unique to them. I've had acceptable results with 2400 and light bullets. In my tests, the behavior got too quirky at 225 gr bullets and up. The biggest problem is loading density. To keep pressures in the safe zone, I wind up with charges that leave the case half empty. That means the powder is sitting in the lower half of the case in the gun. I got more consistent behavior by placing a disk comprised of one ply of a two ply sheet of toilet paper, cut using a sharpened mouth 450b case. Then I fill up the gap to the base of the seated bullet with grits or cream of wheat. With each charge, I measure that distance, charge a case, remove the grits and weight them. Then I weigh each subsequent filler charge for that particular powder charge to keep my results the same. Grits are not weightless. If you just eyeball topping off each powder charge, your results will vary within that given powder charge a lot more than you might desire. I'm spending a lot of time with this aspect than it deserves.

2400 has merit. Especially if you hunt where it gets incredibly cold. The problem with 2400 is that it will go from entering the sweet zone in terms of velocity, accuracy and pressure to over-pressure in as little as a one grain step under certain conditions. Lil Gun, N110, W296 spread the love over a greater range. If you want a powder just a little faster than Lil Gun, consider Vihtavuori N110. Otherwise, with a hot primer, Lil Gun is quite up to the task with bullets down to 200 gr but then yes, my experience has been that you need a good grip on the bullet by any means.

Hoot

[Texas Sheepdawg]

I always considered 2400 to be a slower powder, but then, I used it only for my .357 Magnum. Man, after 26+ years, I still have a lot to learn.