I have previously posted here about the problems which I have had with my custom wildcat which is essentially the same as a 416 Howell. To summarize, first we had problems with over-long bullets (Hornady changed where they put the cannelure) which raised pressures and then we had flattened (as in absolutely ironed) primers.

As pointed out here recently, all flat primers don't mean excessive pressure. What was happening here, as some very helpful souls pointed out to me here, was an over-large chamber and the primer was backing out upon initial ignition, and then the case was flattening it when the main charge went off. The cure, also suggested here, was necksizing the cases after initial firing.

Anyway, I found some Howell data, and loaded up some 400gr Hornady's using 4320. It worked just like Howell said it would. I started at 72 grains and went to 77grains. Velocities ran from 2150 to 2325. Data rounded to nearest "5", and barrel length 22".

IMR 4320 72gr 210M 2175
IMR 4320 73gr WLMR 2185
IMR 4320 74gr WLMR 2210
IMR 4320 74gr 210M 2175
IMR 4320 75gr WLMR 2255
IMR 4320 76gr WLMR 2280
IMR 4320 77gr WLMR 2320

Howell reports 78gr 4320 at 2456 using Barnes bullet primer and barrel length no given.
There were no pressure signs, no odd looking primers, and after six firings no pressure ridges forming in the cases.

I am elated, and look forward to using this rifle on my August elephant hunt. Hornady RNSP's and solids and Dead Tough sledgehammer solids and Nosler Partitions are the bullets of choice. We must see how they "harmonize" and file the front sight because it is shooting low since we fire lapped the barrel.

Thanks to those of you who were helpful in suggesting solutions when I was so frustrated. Kudude

Did I ever mention that this could be fixed while fireforming your brass?

I spoke with Ken, after we had the first 416 AR (anr 458, and 470) up and running. He was pleased with the rounds, and they'll be going in his next printing.

Anyway,
how are you fireforming your brass? If you are just crush/die forming them, can have problems, as your reamer should be .002 or so longer than the "perfect" or "ideal cartridge, and your dies should be (expect shoulder) about .001 smaller than ideal.

after the round are fired, with a full load, I bet if you do a (die to shellholder, with a slight backoff) full length resize, then with ONLY a primer, cornmeal and 10gr of bulleye, you would get a setback primer on that. You may have found that 10 gr is not enough, so work that up till it's where you think it should be. PM me and I'll tell you what load I use on the 416 ARs

So, what I would do is 2 things. Firstly, I would try using RUM brass (see wildcats on the "perfect" brass trimmer) to fireform the basics

second, I would try several settings to determine the PERFECT (partial) full length size setting and lock the sizing die in place. What I mean... I would take the die, run it down to the shell holder, and since we know that's too long, back it off 1.5 turns. Then, with fired cases that are "magic markered" all over, resize ONE... examine it.
(I expect this is a shoulder issue, btw)look at the EDGE of the SHOULDER and see if there's a bright ring.. if so, back off another 1/4 turn and try again.

if there's no mark on the shouder, or you can see where the neck is being resized, adjust to where the neck gets the most resizing, and notice the effect on the base.. it should pick up some marks, as well.


Anyway, i am seeing nearly 2500 with 400 hornadys and nearly 2600 with sper 350gr magtips... without any real, solid, "go to the range with 15 loads" developement work

Jeffeoso,
I take a 404 case which has been trimmed to 2.7"*, and run it into the die which necks it from 425 to 416. I prime and load the case with a mid-range charge of powder and a Speer 350gr bullet and fire it. This sets the shoulder in what must be a slightly oversized chamber.

Thereafter, I necksize the case, stopping short of the shoulder by a "bump". The cartridges are easy to chamber, and I have no problems with "crushed" primers. I can tell with the amount of shooting I have ahead of me, I may have to get a cannister of 4320!

What I have found interesting is that this cartridge has behaved very differently from the parent case although the only change is from 425 to 416, and shortening the case from 2.85" to 2.70". Many report RL15, 4350 and 4831 as the "go to" powders with the 404, but these have not worked well in my experience. I hasten to mention that case capacity is reduced by seating the bullet deeper, and the bore is slightly smaller, but Howell uses WW748 and IMR4320 w/ 400gr bulets and 4064 primarily with 350gr bullets.

Did Howell share any insight into using any other powders in this wildcat? I am eager to find out everything I can, having had success with his 4320 loads. (I felt that 748 did not work as well in my rifle, with the velocities achieved in my limited testing indicating I would not obtain my target velocities within his maximum loads.) Kudude

*I originally was going to use it at its full length, and the rifle is so chambered; however, Hornady changed the cannelures on its 400gr bullets such that seating these bullets to the cannelure ran them into the rifling in the full length case. This appeared to raise chamber pressures, and to prevent this from happening and permit crimping the bullet, I shortened the cases to 2.7". This reduction in case capacity and my shorter barrel may be the reason I am losing about 100-150fps in my rifle. k-d

Kudude,
sounds like you have it done. I am using h335 in my 416 (and 458 and 470)... and getting great results. 748 didn't seem to work, as i got pressure quick.

I am going to start doing "real" load dev on the AR rounds (kinds cousins to yours) and see what we can get out of them. I get 2450+ with a 26" barrel with the 400gr and h335, and 2550 with a "plinking" load of the speer 350 from 25" barrel.

i "discovered" h335 when working on the 550 express, in that i couldn't get the working pressure i needed from slower powders in that case and barrel length.. so I bought a jug of wc844 to begin work with.. the loads between commerical and bulk h335 were close enough, as i don't like pressure.

try fireforming without a bullet. ue a good charge of bullseye, fill the case with cornmeal/grits, top off wth a packing peanut" and bang... gives me a good fit on the reloads.

look in wildcatting on m "case trimmer".. might make life a little easier for shortening your cases

jeffe