6.5 sst (sherman short tactical) arrived

[elkaholic]

Well. the hint was dropped a while back and the day is here! The slightly milder version of the 6.5 Sherman Shortmag has been chambered by Eric Goss (Axis Works) and will be shooting its first PRS match this weekend by" tbeckstead", this forum.
The SST was developed with competition in mind, but that doesn't mean that it won't be a highly effective hunting round. It will share the same SAUM parent case with the same length and body taper. The primary differences are a 30 degree shoulder for smoother competitive feeding and a shorter throat to cycle through almost any magazine. (coal with 140 VLD is 2.795"). Since the round won't be fire formed until tomorrow, I don't have an exact case capacity, but it should be between 69-70 grains.
The idea behind the SST is to run moderate pressures at approx. 3000 to 3050 fps which should give 3000 rounds of barrel life and put it above anything else in its class at this velocity.
I designed the case so that the exact same "ready to form brass" can be used for either the SS or SST. Another benefit is that the SST case is .003" longer at the neck/shoulder junction so it can be fired in a SS chamber with proper head space (like an A.I.) I expect the SST will max out near 3200' with a 26" barrel, for those who want some smack down on game.
I am counting on Thane to post some pics and description on the build with maybe some data on the fire forming and initial testing. I usually do that myself, but with a match on Sunday, he will have his hands full trying to get it all together Good luck Thane!!

 

[codyadams]

How many rounds fit in a standard 10 round AICS mag with the magnum case diameter? It will be interesting to see how it compares to a creedmoore or 6.5x47 for recoil management, as that is a big thing in PRS. What powder charge are you estimating to run a 140 around 3000?

 

[elkaholic]

How many rounds fit in a standard 10 round AICS mag with the magnum case diameter? It will be interesting to see how it compares to a creedmoore or 6.5x47 for recoil management, as that is a big thing in PRS. What powder charge are you estimating to run a 140 around 3000?

You will have to ask Thane about his magazine. I know he has a brake on it, but not sure which one so recoil is still a ?, but it should be very mild. All that stuff he will likely post on soon. This was such a wham, bam, operation that there isn't much to add until he gets smoke coming out! Based on the SS charges, I am guessing that Thane will be using about 52 grains of the H4350 he plans on trying?? I think if RL26 was used, it would take about 55 grains, give or take? I am pretty sure that N560 would be a good choice too....Rich

 

[tbeckstead11]

I'm JACKED about trying this new SST out! I have 100 cases loaded up, ready to fire form, but the rifle didn't come in the mail today like I was hoping, so that will have to wait until tomorrow. I'll keep this thread updated on the load development and all the particulars as we go along. I used 49 grains of H4350 for the fireforming. Plenty of capacity left in the case. I'm going to use the new Nosler RDF 140gr bullets. Everyone that I know using them says the published .330 BC is accurate, so that pretty hard to beat.

As for Magazine Capacity, I ordered a +2 extension from AxisWorks LLC so I should be good to go. I'll let you know for sure when they get here. Later tonight I'll load up my 10 round AICS and let you know how many will fit in there.

The rifle is a PTG blueprinted R700 stainless Short action, Bartlein MTU countour 26" barrel, JP enterprise Recoil Eliminator Brake. It'll be in an XLR Evolution Chassis in a couple weeks, but for now it will have to go in my B&C I've been runnning for the last year and a half or so.

Thanks for the opportunity to break this new SST in Rich! I'm really looking forward to it. If all goes well, I'll burn out a barrel in the next several months so we have a real good idea how long it will go.

 

[elkaholic]

I'm JACKED about trying this new SST out! I have 100 cases loaded up, ready to fire form, but the rifle didn't come in the mail today like I was hoping, so that will have to wait until tomorrow. I'll keep this thread updated on the load development and all the particulars as we go along. I used 49 grains of H4350 for the fireforming. Plenty of capacity left in the case. I'm going to use the new Nosler RDF 140gr bullets. Everyone that I know using them says the published .330 BC is accurate, so that pretty hard to beat.

As for Magazine Capacity, I ordered a +2 extension from AxisWorks LLC so I should be good to go. I'll let you know for sure when they get here. Later tonight I'll load up my 10 round AICS and let you know how many will fit in there.

The rifle is a PTG blueprinted R700 stainless Short action, Bartlein MTU countour 26" barrel, JP enterprise Recoil Eliminator Brake. It'll be in an XLR Evolution Chassis in a couple weeks, but for now it will have to go in my B&C I've been runnning for the last year and a half or so.

Thanks for the opportunity to break this new SST in Rich! I'm really looking forward to it. If all goes well, I'll burn out a barrel in the next several months so we have a real good idea how long it will go.

How many WINS will that be!

 

[tbeckstead11]

I can get 8 in a standard AICS 10 round 308 magazine.

 

[codyadams]

I can get 8 in a standard AICS 10 round 308 magazine.

Ok, that's not too bad. I use the Alpha type II mags, they are significantly shorter than a standard AICS mag, but double stacked with a standard bolt face cartridge. With a mag, I doubt they would double stack much, I would probably be around 6 or 7 in mine

 

[Trnelson]

Tagging in, like I need another 6.5....

 

[tbeckstead11]

How many WINS will that be!

Well, I'm not even close to as good as this rifle will be. If all the stars align, I might compete in a few

 

[reeldawg]

Check out MPA. They make a 4 round extension for for AI and Accurate mags. Rich does this take a mag bolt face?

Jay

 

[Predator 22]

Tag

 

[codyadams]

Check out MPA. They make a 4 round extension for for AI and Accurate mags. Rich does this take a mag bolt face?

Jay

Yes, all the ss cartridges do. Bases on the SAUM

 

[elkaholic]

Yes, a magnum bolt face.
Well the dummy that designed the case did not bump the shoulder back quite far enough so Thane is left hanging until he gets a saum die shortened! All I had to chamber in was my SS so I set the shoulder where I thought it would work but came up a hair short, so the bolt won't close. I guess I was a little worried about TOO MUCH head space, or that is my excuse anyway!
We are still hoping a miracle happens and Thane will be able to compete this Sunday?
I had the chamber reamer and sizer reamer ordered at the same time so SST dies are still likely 6 weeks out...............Rich

 

[tbeckstead11]

I got the brass sorted out, fireformed, annealed, sized, and a ladder test ready to go. I'm going to use Re26. Started at 53.5 grains and loaded up by .2 to 58.5. This should be pretty well into max. I'd like to see where I get pressure signs. I also loaded up some H4350 just to see where max will land with that powder. I started at 52.5 and loaded up to 54.5.

I'm using the Scott Satterlee method of load development. Shameless plug for my Facebook page. If you go on Facebook and search for Precision Rifle Shooting (PRS) for Beginners, the pinned post has a good explainatiom and a link to a video about Scott's method.

I'll try to get this test done tomorrow and get back with th results.