|
Post by HMC710 on Jun 12, 2013 7:28:57 GMT -5
Barrel is profiled and waiting to be set up to chamber. Been doing a lot of set up work on the lathe and built some new tooling to see how much better I can get a barrel. Bro has a smaller set up that is quicker to use so we might start doing all chambers on his machine. Anyway been learning, testing, and making things better. But, back to the 256 - Cut some brass down and formed. Did that a while back after I got the dies in. Cut down .223 brass, tried some stock length .223, and also did a couple .221 Fireball brass. The factory length on the 256 is 1.281" which are the 2 cases on the right. The left case is the stock .223 and the 2nd from left is the .221 (actually a 300 Blackout necked down) with a factory length of 1.397". As you can see, because we don't care about using .357 brass, one shot through the 256 dies with the Fireball case and Presto, the 257 Fireball. (We also did this with the 7mm so a 7TCU will fit an AR mag) With the 257 ARS and 1:14, it wants the short bullets. With the 1:10 twist we'll see what happens with the 95 gr + bullets. Seating them long for the AR mag we could use the extra .116" of case length. Now I can argue both cases here but if we already have all the Whisper / Blackout case work done, it eliminates the extra trimming. However, maybe if our Fireball / BO case gets tired, we can trim from 1.397 down to 1.281 and form into 256WM. But the chance of saving a split neck by trimming .110" is slim to none. Anyway, thats an option. Going to chamber this pistol barrel with the 256 Win Mag case and see what happens.
|
|
|
Post by HMC710 on Jun 17, 2013 10:12:45 GMT -5
Cut some cases down today and will get them cleaned up and run through the dies.
|
|
|
Post by HMC710 on Jun 18, 2013 9:16:05 GMT -5
Finished my case work and got everything cut sized and trimmed down to 1.281. Loaded up some 75 and 100 gr loads using the H110 I had in the powder measure. I usually try to load bullets no deeper than the base of the neck. With the 75 gr JHP this was 1.86" oal. Pushing them down as far I could this only got me down to 1.698". Factory OAL for the 256 WM is 1.590". My old Lyman manual says the factory duplication load is 16.2 gr of 4227 with a 60 gr bullet at 1.590" OAL. Fired from a 24" barrel 1:14 twist results in 2747 fps. With the 75gr JHP seated as deep as it would go (far right) I could not get the 256 into an M1 carbine mag. Seated to the base of the neck the 75gr (middle) and the 100 SPBT (left). The 100 gr came out at 1.960" Having gone through all of this, my gut is still telling me why not just stick with the 221 Fireball length case? Its only .116" longer and just call it the 256 WSM (Win Super Mag) or 257 Fireball. I don't own a real 256 so I don't know if you could fire the rimless case in one or not. Probably an ejector change would work in a Contender. Anyway, If I do another one it will be with Fireball cases. All of the loaded rounds dropped right in the chamber with no rifling marks present so we'll fire off a few rounds and see what happens.
|
|
|
Post by HMC710 on Jun 26, 2013 11:24:30 GMT -5
Barrel still on the bench, just haven't had time to test fire. Given the case length and if the 257 ARS and 22 RE are any indication, the 1:10 twist wasn't the best choice for this. Time will tell.
|
|
|
Post by 22boomer on Jun 26, 2013 11:40:19 GMT -5
I don't know if I already posted this or not but the 1:10 twist is good for most bullets up to 100gr -- as long as the actual bullet length is not too long like some VLD bullets. I have a real cheap and dirty bullet twist rate program to see if the bullets I want to use will work in my barrel. kwk.us/twist.html Try filling the info and see what falls out. Just in case you were thinking about some other bullets here is a listing of commercial bullet lengths by manufacturer. www.jbmballistics.com/ballistics/lengths/lengths.shtml#Barnes
|
|
|
Post by HMC710 on Jun 27, 2013 7:16:45 GMT -5
Thanks for the bullet list, have the twist rate calc. QL also lists bullet lengths to see what is out there. The factory round is 60 gr so they had the same issue of staying in the .357 envelope. We'll see what happens. Off topic but same case is the .357 rimless. Ran some cases through the expander and really blows the neck out so don't know how uniform they would end up after fire forming. The case dia is listed at .379" which is only .001" larger than the .223 at .378", so if I ever end up with a reamer and a blank I might do one just to say I did.
|
|
|
Post by 22boomer on Jun 27, 2013 9:55:20 GMT -5
After I fire-formed a bunch of cases I decided to just neck size so I wasn't screwing around with the reformed base. I was told that just neck sizing was a no-no for AR's but I'll tell ya -- it worked great for me with this cartridge -- they always fed nice and smooth.
I saw your pictures in a previous post that compared the256WM case size to the 300blk. With the right twist this could maybe be a 256blk -- just a thought since there seems to be a lot more heavy .25 caliber bullets than light ones. I only use the 70gr sierra's since my barrel is only 11.5" long and I want plenty of supersonic.
|
|
|
Post by HMC710 on Jun 29, 2013 7:00:51 GMT -5
Hmmm, my last post didn't show up.... Anyway, I have a neck size 7.62x39 die that I run in my AR all the time. Barely any pressure on bullet when seating and was concerned about the bullets moving in the magazine but they work.
Loaded up some Hornady 120gr HP over 9.0gr of H110. QL predicts between 980 - 1050 fps depending on seating depth. * OK - something is going on here * Just ran QL here at the shop and got different numbers, now I get 1200 fps with the same load.
Anyway, the 120gr HP is 1.185" long. The WM case is 1.285" long. Seated to the cannalure = 2.050" and they chamber. I loaded three up at this OAL and three more at 2.200". Didn't want to wake the neighbors last night or this morning so I'll try and get them run off this afternoon.
|
|
|
Post by HMC710 on Jun 30, 2013 10:18:12 GMT -5
Ran some of the heavy bullet loads through the 256 yesterday. Three rounds 120 gr w/ 9.0 gr H110 @2.200" Three of the same at 2.050" Three 100 gr w/ 8gr H110 @ 2.000" Three 100 gr w/16gr H110 @ 2.000" I'm running out of scopes to put on all these uppers....... . Because this one is a High Rider I didn't want to borrow one of an A3 so I had one left, Burris 2x pistol scope. First three rounds were the 120 x 2.200". All chambered without a problem. They would eject but wouldn't hold the bolt open. Fed them out of a stock mag. Held on center bull and they were 5" right x 1.5" low. Out of the three shots, two of them tumbled. Next were the 120 x 2.050" and held at top left bull: 2 shots hit 1.5" right of center bull but the third tumbled and hit 2" right of top left bull. Velocity was super sonic so I don't know if slowing these down will help but they don't stabilize reliably. 3rd string was the 100gr over 8gr H110 with same top left bull hold. These were more stable and put in a 1" group. Then I tried maxing out the 100 gr load with 16 gr of H110 and the result was about 5" + group scattered all over. I held at the top corner of the lower quad just trying to keep cross hairs on the edge of the shaded portion of the target. One thing I should do is start a spread sheet of all this data and correlate with the twist formulas to see if we can predict when these bullets fly and when they scatter.
|
|
|
Post by HMC710 on Jun 30, 2013 10:21:22 GMT -5
Here are the two rounds compared with the 75gr HP. L - R: 75gr HP, 100gr SP, 120gr HP All the heavy bullets fed great of of stock mags so the issue is going to be what niche are they going to fill. The factory duplication 60 gr bullet would probably like the 1:14 barrel better but we'll load up some of the 75 and 87's I've got and see what happens with the 1:10 we've got.
|
|
|
Post by HMC710 on Nov 19, 2013 18:41:02 GMT -5
Been revisiting this post and trying to decide if I want to re chamber this to 256 Fireball
|
|
|
Post by 22boomer on Nov 20, 2013 8:20:52 GMT -5
If you did the 256 Fireball what is the difference in case capacity and is it a good length for the AR magazine? Can a good weight bullet be used without having to stuff a lot into the case? Are you going to get a reamer made? My rimless 256WM chamber was actually cut using the 256WM reamer and, as you know, the 256WM base is a bit larger in diameter than the .223 so fired rimless cases came out with a very slight bulge. The bulge doesn't seem to hurt the case since I've reused my brass many times -- but a correct chamber would be nice.
|
|
|
Post by HMC710 on Nov 21, 2013 20:01:19 GMT -5
for this test I will deep chamber using my stock reamer. WIll look at bullet weights and case lengths and probably see if Dave Manson can grind me up a reamer with .223 base on it.
|
|
|
Post by HMC710 on Dec 9, 2013 22:39:23 GMT -5
Picked up some Palmetto State Armory lowers they had on sale with LPK for some of my lonely barrels. Found some Pistol buffers and put the 256WMR together. I'll get pics, it looks pretty good even with out a handguard on it. If it ever stops raining we'll run some rounds through it.
|
|
|
Post by HMC710 on Dec 14, 2013 14:23:18 GMT -5
More rain today, but Sunday is supposed to be nice. Running some ideas about the 256 and will see what the drawings look like. Might try some 25-20 bullets and see what happens
|
|