OK race fans, the two 357's are chambered and getting ready for final finish. If this is to proceed, the reamer definitely needs to be modified to include a square edge at the case mouth instead of the normal 357 long taper. I left both chambers a bit short just because. I also have not put in any dummy rounds with as formed brass to verify neck clearance, so that will be done after I clean these up, port, and bead blast. I don't know how much more I'll get done today, bro said there's too many beverages in the fridge......
and we have lift off! The 357 AMag is alive.....Running the pistol port "with authority" and our new M1 carbine mag set up. Pics to follow tomorrow, but things look good so far. Running a conservative load of 2400 and 115 gr JHP QL says 1850 from the 10" barrel. Can I get a Wooooo Hooooo
Here are the barrels fresh out of the cleaning pit.
and the assembled 357 AMAG 8" Pistol.
Its dressed up with a UTG FF Pistol Quad and a BTE adjustable gas block. The barrel is an 8", not 10" like I mentioned yesterday. I also updated my QL with the 115gr 9mm bullet I used instead of the 125gr I had in QL. Pressures in QL all dropped significantly with the 115gr bullet. QL shows 1700 fps with the 16gr charge of 2400 I used, which shows 34,000 psi for the 357 Magnum at 1.59 OAL seating depth. Case volume was 94%. The powder was definitely too slow as evidenced by the rather large muzzle flash. Swapping over to Power Pistol, or AA#9 shows over 2000 fps from QL estimated 60,000 psi. H110 & 296 both show a compressed charge like 2400 to get those numbers.
Brass: The case mouth expanded enough for a fresh bullet to slide into a fired case without much excess. I'll get some better readings when I dig out my good calipers but its looking like the base measures .3775 and the mouth measures .3805 on these cases. That also tells me that the pressures were in the 357 Mag safe zone....
Bottom line is: 1. Testing was flawless 2. The gas system can be tuned DOWN 3. The M1 Carbine mag system worked for the limited test we have done 4. A true "headspace on the case mouth" reamer should be made 4. Somebody needs to cut a bunch more brass.......
Test fired the AMAX using 22.5 gr of 2400 and the same 115gr JHP 9mm bullet (because that's all I had laying around)which QL predicts about 42000 psi. I have a carbine gas system on this one and will work on tuning while I ramp up power a bit. The rounds will load in a stock mag to a point and a bit better in a 7.62x39 mag. I've only fired a few rounds but no major issues with feeding, just not as smooth as the AMAG. I'll post pics whenever they finely transfer from my phone........ But: It works!
Well, photobucket sucks more than usual today so here are some small pics.... What you can't see well are the three rounds on top of the receiver; 5.56, 357AMax, 357AMag, plus the B E A utiful ss barrel. But, if you double click on the pic, it opens up!
The AMAX was loaded up to 40kips and it did blow the base of the case open a bit. Once fired brass measured .375 or so and there was a bulge about .300 up from the rim that went from .380 - .384 on the fired AMAX, so it is opening things up a bit. Will it cause case head separation? I don't know, but I'll run up the charge slowly while I test feeding from stock mags. The 115gr bullets would slide into the fired case, so that tells me there isn't a neck tension issue. However, I do need to measure the case bell die (Lee Powder through expanding die) dia because the 115's slid right into them expanded case. All in all, a good day!
Did a bunch of case forming the other day. The 357 AMag's are pretty easy, but also have some thicker walls with the heavier bullets, >140gr and are tight in the chambers. Stock .357 mag dia at the mouth are .375 and the LC brass loads are .380 even tho wall thickness both measure .010. We will see what happens after I reload the formed cases. The chamber should have a case mouth formed like the 30 Carbine, but every round fired off. I formed some cases with 115gr 9mm bullets, 158 gr JHP 357's and 90gr XTP .357's. I switched to H110 and loaded to stock 357 spec's and H100 "full" loads all filled the case and were compressed loads. The LC brass definitely has some smaller volumes and I was using small pistol primers. I don't have QL on this machine, but I was getting some seriously flattened primers. 90gr XTP = 1891 fps 115gr 9mm = 1943 - 2000 fps 158gr = 1650 fps If I continue on this path, a new reamer is probably the best bet to form a good case mouth and open up the chamber a bit so we don't have to mess with brass reaming. Another option would be to do a 9mm version and offer the 9mm mag, 9mm Super mag (1.29 case) and 9mm Max. We'll see what kind of feed back we get.
For the 357 Max we used the same bullets. Chambering was smoother as the case walls were obviously a bit thinner. Using stock mags, the rounds usually didn't feed all the way, partially from the lack of a feed ramp and the long by AR standards, straight wall case. I'll do some research on the other straight walls, 450 Bushmaster and 50 Beowulf to see if I can get some chamber dimensions. My barrel wasn't "ramped" much at all so there might be some room to improve there. 158 JHP = 2200 fps 115gr FMJ 2650 fps (flat primers) THese also were H110 loads from the 357 maximum load data max loads.
Another good day at the range. Temps were actually too warm as we hit 80 degrees out! Reloading the fired cases went smoother so that is a step in the right direction. The 1.29" length cases did have some thick walls going from .010" to .013" as you got into longer seating depths, so that's where the tight fit came into play. Using <125gr bullets should allow un-turned cases to be used. Same way with the 357 Max, but this time the 158's seated easily and chambered just fine. I switched over to 2400 powder and could tell the difference between the two when I used up the last of the H110 loads at the end of the session. Velocities were actually a bit higher than the H110 loads. We used stock mags with the Max and got the rounds to feed with the FMJ bullets, but only loaded two at a time for testing. The AMag used one of our new Tok mag set up and was a bit long to get more than one round in, but feeding was much better than yesterday. I need to take a look at the chamber bevel and feed ramps to smooth things out a bit, but it should be able to feed reliably. If the 450 Bushmaster can do it, the 357's should also. One thing that I don't have is our new M1 Carbine mag set up, our last one went out with an upper, so we can get more feed data with the 357 AMag.... I did pick up some 125gr JHP and was looking for some 180+gr, but couldn't find any at the LGS so we will continue with the 125's and the 158. I'll get some more loaded up tomorrow and see how they print.
2/25/17: Loaded up some of the 125 XTP loads with 19.5gr of 2400 with a case length of 1.590" and 1.690" for the 357 AMag and also switch from the Tula Primers to Remington 7.5 primers. Velocity was right around the 2020 fps and got the red dot scope adjusted to print on paper at 100 yards giving horizontal spreads of about 3" for 3 shot groups. Using the same load with a 1.690 OAL dropped the spread to about 2" with the 125gr Hornady XTP's. Tried using a 5 round 762x39 clip and got nose up jams when feeing the AMags. Reloading the Amax rounds revealed some case separations:
A quick look at the chamber didn't reveal any burrs or knarfs but we will definitely do an autopsy when I'm back at the shop. Loads for the Amax were 20gr of 2400, Rem 7.5 primers, and 158 JHP at 1.920" seated to cannalure. Velocities were touching 2000 fps, but.... got multiple case separations as shown in the pics above. Rounds were crimped with the Lee seating die and just by feel were not consistent but felt heavy. Groups at 100 yds were 2 close with 1 expanding out to 3".
Also loaded up some longer rounds at 2.020" with the same set up, basically backed off seater 1 turn. VIOLA, no spit cases. Groups also tightened up a bit.
Did a 5 shot string with 3 touching and 2 opening things up shown by the circled group. Twist rates on both 357s are 1:20, from which my researching shows is good for up to 160gr bullets, depending on velocity. But seeing as I only had 125 and 158 .357 bullets, my options were limited. The split cases concern me a bit so both uppers need to be fully stripped and inspected. My thinking is the H110 loads I started off with over stressed the brass and the writing was on the wall.
I also didn't do any of the 357 AMags with the 158 gr JHP's.
Where I go from here will depend on how much interest is generated from this thread. Looks like a nice Whitetail round to me!
More testing since the last post and added the Hornady 140gr FTX polymer tipped bullets. These bullets are very long and I can get them to chamber in the AMAX, but not the AMAG. I was having issues feeding so we worked on that when I got back to the shop and things are looking better. Went through a quick string of the AMAGs with 100% function. This was using the new M1 Carbine mag set up with BHO. The AMAX can be fed from stock mags, but the 556 is too narrow in the front. 762x39 mags work better and I've got two cheap ones I'm using for testing while I decide what I want to do. The Hornady FTX bullets get seated very deep and it doesn't take much to get them into the rifling. This might be a prime spot for a cast SWC to get AOL past 2.000" so there isn't any push forward during loading.
Just tested some of the 140 FTX bullets loaded with 18gr of 4200 and 1.930" seated in the cannalure and 1.980, seated one turn out but into the rifling. Neither load would cycle the action or eject the rounds. Last loads were hot at 21 gr. Feeding was much improved, but mags are still an issue so I'll work on sorting that out.
Ran some more loads through the 357 AMax today and made some port adjustments on the barrel. Using the Hornady 140 FTP and 2400 powder we got a solid 2300-2350 fps with no issues. Working on port size now to optimize for operation. We also tried a new magazine set up and so far, so good, as we are feeding the long straight wall cases with bolt hold open feature. During feeding you can definately tell we are hitting things on the way in so well do some work when we are back at the shop next week and see what we can do to smooth things up. I might go a bit more on the port as there is little room for error on locking the bolt back. Ive got all my new brass fire formed, so well run some more tests and see where we want to go from here. The only issue i see so far is blowing out the case above the base on 223 brass. I might "de-rim" some 357 Max brass as a test to see how they compare to the formed 223 stuff.