5.56 on the left, sized 250SS on the right - not fire formed. This started about a month ago. Why not just short chamber the 250 Savage? A short 250 Savage..... The 250 SS. I like the name, would it work? I wanted something I could do (ie KISS, or stupid simple). 7.62x39 brass, cut down some 250 savage dies, form the brass, short chamber a barrel, fire form, and GO. It worked on paper. But what about performance? My objective was to run a 100gr bullet at 2500+ fps. Calcs on QL said that could easily be done with the 250SS. The only draw back I saw was the case base dimensions, but if this works, we can fix that.
From L - R: 762x39 case, formed 250SS, fire formed 250SS w/117g BTSP, 6x45 case
I didn't want special cases or trimming or bolt faces or anything. Set up a press and go. The case was fire formed with 100 gr Sierra into the rifling and 18 gr of 4227. Chrono avg vel was 2251 fps. 4227 is a bit fast for optimum performance, from what I could calculate, but I wanted a forming charge. Shoulders are not quite defined yet so I'll try Bro's 6ppc forming charge and see what happens. I picked up the dies on ebay for $9.09 + $4.95 S&H, not much to lose there if I screwed up. Got out case drawings and trimmed the difference between the 250 Savage and 762x39 cases, .388" according to the info I had. Lubed up a brass 762x39 case and ran it through the short die - and - wrinkled the shoulder. Did it again, rotating the case a few times as I worked it down, and presto, a 250SS case. Pressed in a bullet and measured neck OD at .282" - Savage neck dim was .285", might have to work on this area. Loaded the dummy round at 2.250 oal and chambered it to check fit and see if there were any rifling marks. It chambered and had rifling marks. Might be able to push the chamber fwd a wee bit, but lets see what happens. I've learned it's lots easier to move them forward than back! Formed the once fire Remington brass that I had from my SKS. I took a high base dimension on the brass for a baseline: .443". Loaded up a case at 2.25" oal, chambered, and fired. It was an absolute smooth fire. Just a push on the shoulder, it just felt right. Chrono said 2251 fps. Case ejected nicely about 4' behind me. Took case measurements and my main concern was the base dimension. Measured .448" and you could see the definite expansion. Shoulder was not as defined as I hoped, but being my first fire formed case, I didn't know what to expect. Fired 2 more rounds. The base needs to be tweaked on the reamer a bit I think to ensure any repeatable accuracy and to ensure case life. Gas system was mid length with .089" port and an 18" brl. Thought it might be on the low side but even at the low powder charge, cycled and ejected perfectly. Might be able to cut it down a bit. So, there it is fellas, what do ya think? My goal is to do a group buy of 10 barrels/uppers after I decide what to do on the reamer. Then I'll get w/Dave, adjust the reamer, and have Lee make 10 Die sets. Once thats done we'll have a contest for best group out of the 10 barrels. The winner gets his barrel and die set for free.
Talked reamers and chambers yesterday with some folks. Going to fire form some more cases with what we have then do some reloads with W748 & H335. Will try and dig up some cc equipment to get an actual volume measurement.
I got the 250 Savage reamer first, 256 will be next, based on the .223 case. Fired more cases yesterday and definitely ran up the pressure using 4227. Switched to H335 and tried 27 gr with the Sierra 100gr SPBT 1625 seated to 2.220 OAL. Cases filled out nicely and vel ave 2521 fps when fire forming. QL calculated pressure of 41ksi and 2473 fps. Reloaded the formed cases and tested with the same load, but my light was not good enough to get good chrono readings. At 2.220" oal I was still into the lands a bit and my neck is just a bit longer than my target so I am going to push the chamber forward a bit today. Also going to adjust the sizing die a bit and add to the bottom to lengthen it out. Cycle and feeding from my Colt 7.62x39 mag was fine. I am going to open up the ejection port a bit on the High Rider upper because I am getting some case bounce on the way out. No accuracy testing done yet and some cases are on their 3rd reload. New brass is on its way, the SKS bangs up brass pretty good.
OK, I'm starting to get excited about the 250. Bumped the chamber forward a wee bit and lengthened the sizing die. Ran 5 cases through the same 27 gr load into the lands with the new chamber then reloaded them with the "new" dies. Nice clear skies today and chrono avg was 2543 fps with a high reading of 2555 fps. Switched over to the 50 yd range where I had a paper plate tacked up. Put my Redfield on, found the aiming point where I was on the paper, and fired the last two rounds I had loaded. Went in and reloaded 3 more and fired at the target again. Was holding 6:00 on the fold line below the black bull. High rings on a High Rider upper.
The 50 yd. five shot group to the left of the writing measured .69". Barrel is an 18" A&B 1:10 twist. Took the same 5 cases and reloaded 3 of them (6th reload) with 28 gr of H335, Sierra 100 gr SPBT, OAL 2.195". QL predicted 2619 fps. Three shots were 2621, 2623, and 2645. Powder charge was still below the shoulder and I forgot what the QL pressure was but I think it was in the 48-49ksi range. Cases ejected nicely (with the opened port) and no signs of flat, cratered, pushed primers, bolt swipe, etc. I guess I need to put this in perspective. I've only been shooting the AR for about 4-5 yrs and BRD has produced many calibers looking for a hunting round. I use my AR-10 or Beowulf and my wife uses the 6.8 SPC. My data from my 6x45 loads got me up to 2460 fps with a 90 gr bullet and I stopped. The 6.8 loads are running 2428 fps with the 115's, not even close to what others are getting. Maybe I have not found the right combination but, like I said at the start, my goal was 2500+ with a 100 gr bullet. The 250 SS has done that and more. I can't wait to get the new reamer.... Been digging up info on bolt thrust just to cover that base. My "assumption" is that if the Grendel 5.2ksi, 6PPC 5.8ksi, and others can run 50,000+ psi, so can the 250 SS. Never assume, verify and follow up.
Finalized reamer with Dave at Manson Reamers and he has it in the works. Have Lapua brass coming and will get another blank started to see how things compare with my Frankenchamber. Meanwhile, I'll find a scope to mount on the 250 and see where this thing will go, 10 days til opening day and its snowing out. "AlGore, clean up in isle 5, clean up in isle 5 please"
For those looking for a 25 based 223, check out ar15.com in the variants section. Great thread on the 25-223 with dies available from CH4D. Getting some amazing performance out of that thing!
I was hoping this post wasn't going to take this long, but it is what it is. I guess I needed a lesson in patience, perseverance, and faith. Managed to leave work a bit early Saturday and get some deer hunting in. About 130 yards, one shot, one deer, no tracking. I watched it drop through the scope, recoil was so easy. I call that a success and the 250 SS delivered. 28 gr H335 Sierra 100gr SPBT. From the autopsy, I will pick a different bullet for the next hunting session. Definitely a through and through (spine, a bit high). As a comparison, the one my wife shot with her 6.8 SPC (115gr HP at 2425 fps), was devastating to say the least. Nice neck shot Babe! The fired case (8 reloads) did have a slightly flattened primer. QL shows a dramatic change in pressures due to bullet seating depth. The throat is also a bit short so here is the plan: 1. Have Bro chamber and throat a new blank with the new Manson reamer and Lapua brass, to his specs. 2. I'll continue to work with my current reamer and do some experimenting with a few things. 3. Compare both results. 4. Make some dies based on these results. This is going to be fun fellas!
Did some work last night on 250 Savage brass and tweaking it to use for the base of the 250 SS. I slightly turned the rim down to fit the 7.62x39 bolt face and then trimmed them to rough length. I ran one through the size die but had a neck failure so I am going to anneal a few cases and try it again. I have a couple other custom dies I might use as a prep to get the neck started. This will allow us to make a definite distinction between the two rounds; The 250 SS based on the Savage case, dies, and reamer; and the .257 AR based on the 7.62x39 case with custom dies and reamer.
The new Dave Manson reamer showed up today for the .257 ARS round (American Russian Stoner). Don't have a lot of spare time right now to turn down another barrel, but have it on the list. Case dimensions are located here: ammoguide.com/cgi-bin/ai.cgi?sn=BMTYqEenBC&catid=800
New barrel is profiled and hopefully chambered today. Way too much dust on this project but...... Picked up some new Lapua brass for fire forming as well a bunch of once fired R-P. Plan is to get this hot rod together, fire form some brass and send it out to get some dies made.
257 got chambered yesterday, thanks Bro! "Man, that is one sweet reamer!" says Bro. "That thing cut like butter. It was awsome." So a quick shout out to Dave Manson at Manson Reamers www.mansonreamers.com Dave worked with us on the 257 and offers a lot more than just reamers so check him out. Thanks Dave! Now we'll get the barrel finished up and decide what we want to mount it in and see what happens.