The Good The Bad and The Ugly About Yor 6.5 Sherman Short

Well, I decided to give the 6.5 SS a try, I pre-ordered the brass and have decided to see how it works out in a rifle first then maybe a pistol and my buddy can see how it all works out for me before taking the plunge. Now if I can just decide on which barrel to use the 1 in 8 or the 1 in 7.5.

I would like to thank everyone who shared their experiences with me on this cartridge, dies, loads and everything else. I would also like to thank Rich for his patients.

Dave

Congrats on your going forward with the 6.5 so project. What was the final fact that helped you learn toward the 6.5ss and not the sst? Go with the 7.5 twist,or go with one of bartliens progressive twists. Start at 8& end with a 7.5 twist. I suppose that's only if you are really going to take advantage of the 6.5 high b.c. bullets like the smk 150 in which case you would probably just get the gun setup to shoot the smk 150's by cutting the chamber for them specifically b/c of their aggressive nose. The 147 eld-m run completely fine out of a 8 twist.

Check with Rich to confirm this..........but I think when you setup for the 150 smk the same freebore works well enough for the elds and hybrid as well. This is where there are is another benefit to the longer neck Rich leaves on these cases but not not taken to an extreme. It allows you to setup on the 150 and yet can still get good bullet base/BT placement in the case for most of the top high BC heavier bullets.

Actually out of the various new sierra TMKs only the 224 cal does not follow the same general design format. All the others get these long necks standard body and longer BT. The 224 gets a small increase in neck basically none in the BT but a much longer body bearing surface. Because of this you need much more freebore than say the 90 VLD and SMK used for ideal base placement in the neck and makes it hard to setup for both. Not a concern here.

Issue is Sierra not publishing any dimensions specs for any of the new TMK other than G1 and OAL. I love Berger for how they handle and always give you detailed dimensions.

Unless you had a long COAL your receiver / mag box handle and really maxed out the freebore for the 150 in that scenario like 3.1+ you could then have an issue but with the typical 2.9 sub 3.0 I think the freebore for those works out well with the SS/SST neck length.

Again best to hear from Rich on this to confirm it.

Actually none of that is correct. Neck length has nothing to do with freebore,or setting the bullets coal etc. Unless I misunderstood what you meant.The main reason I even mentioned it was we were talking about twist rate. The overall length of the 150 smk round will be extremely longer than than say 147eldm if you're going to run them at 20 thousandths off lands b/c of the base to ojive measurements. That would most likely cause the overall length of the round to be longer than magazine length. That's why I mentioned that you would probably want to set things up from the beginning to cut the chamber for the 150's. A chamber to run the 150's at say 20 thousandths off with a coal of 2.840" would have the 147's way jammed at the same coal& probably (w/o measuring bullet lengths right this sec) would be jammed even at 2.800" . So b/n mag length and twist rate being higher,you probably would setup the gun from the start just to run the smk150's is what I was saying.

The std. Reamer for the sst runs the 147 at just over 2.8" and the bullet is into the body a ways. I did this intentionally so most bullets could be run through just about any mag. It actually works out so that the much longer smk with a more aggressive nose, will work pretty well. We didn't have the150 smk when I set it up so I don't know exactly what the coal is, but it would be moved ahead considerably and be positioned better in the neck. Doing some math, using the 2 designs, the smk should be .020-.030" into the neck at the body/boat tail jct and have a coal to the lands just over 2.9".In a round about way, the neck length does have a bearing on throat length design, provided the neck/shoulder jct is the
reference point. I.e. .020" longer neck means .020" shorter freebore, all else equal. Also, the longer neck does give more lee way to move bullets around and still have adequate bearing surface grip.

Ok, I just remembered that I had just gotten some SMK's in so I went to the shop and loaded one to the lands. It turns out the original shorter throat is about as close to perfect as you could plan for the 150

2.3051" to throat is what my 6.5 sst print says. If I run at 2.240" base to ojive measurement, the coal of the smk 150gr is 2.940"... now that's with quite a jump to keep it at just inside mag length. I see your point of view of neck length in a "roundabout" way lending itself to determining freebore. Again I would definitely set the gun up from the beginning to shoot the 150's by first running a faster twist,and since I would be using a short action,to set up the bullet coal to be at most a 2.840" with a .020" jump so I wouldn't have to worry about feeding issues or problems ejecting unfired rounds. The big plus of the round is it's a short action,why complicate it with trying to effectively run rounds on the edge of proper function. I realize that's only my opinion, but I think it's a logical one.

I'm not sure how you came to the 2.940" conclusion with a jump? I spoke with another PRS shooter today and he confirmed that with his new barrel, it was just UNDER 2.9" to the lands with the 150 smk? Mine was a little over, but I have several hundred rounds through it.
I just checked it again and 2.920" jams the bullet quite a bit! I do agree that a 7.5 twist would be preferred for the 150 SMK.

I believe you misread my posted information. 2.940" was coal...not jump,the jump I was referring to was .065"...2.305" distance to throat,and the 2.240" was the base to ojive measurement on the 2.940" loaded 150smk using a hornady gauge. I've been shooting& tuning them out of mine now to the tune of over 100 rounds with different jumps/coal etc. And the base to ojive measurement using the gauge I have is exactly 2.246"bto at 2.940" coal... I'm not trying to get in a ****ing contest over this. The information my gauge with my chamber is as stated. Perhaps this has gotten way off topic. My original reply was commenting on twist rate for setting up a new rifle.

I think I know why, at least, I am confused. Do you have the ss, not the sst? If so, my bad! That would be very close to the ss dimension. That would make all your previous measurements pretty much on! I knew Dave was building the ss but thought you had the sst. GETTING OLD STINKS!

150 SMK in a 6.5SS w. 26" 1:8" twist is a thing of beauty. 3156fps. Max load for my rifle over RL26.

Lance.,. Could you post the coal with the 150 in your SS (to the lands)

lancetkenyon said:

Click to expand...

Thank you sir. I'm not crazy after all