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270 Sherman

 
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  #15  
Old 02-26-2013, 08:43 PM
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Re: 270 Sherman

It looks like the case capacity so far is about 9% greater than a fired case that has not been resized of the same batch of cases I made the fireformed 270 Sherman brass from.

I filled a formed case with a short dropper tube with 7828ssc and came up with 73.5g level full, the un-resized 270 case held about 67.5g of 7828ssc. That charge did not come to the neck in the Sherman case.

I have looked at quite a bit of loading data for 270 AI's and Gibbs' and it looks like a 9% increase in max loads may be close to where I end up if everything pans out. I will be starting with a max load for a 270 and going from there...

I will also probably be trying some H4831sc and RL17.
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  #16  
Old 02-26-2013, 09:49 PM
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Re: 270 Sherman

Quote:
Originally Posted by CogburnR View Post
It looks like the case capacity so far is about 9% greater than a fired case that has not been resized of the same batch of cases I made the fireformed 270 Sherman brass from.

I filled a formed case with a short dropper tube with 7828ssc and came up with 73.5g level full, the un-resized 270 case held about 67.5g of 7828ssc. That charge did not come to the neck in the Sherman case.

I have looked at quite a bit of loading data for 270 AI's and Gibbs' and it looks like a 9% increase in max loads may be close to where I end up if everything pans out. I will be starting with a max load for a 270 and going from there...

I will also probably be trying some H4831sc and RL17.
I thought I had close to 11% increase , but thinking back, that may have been from an '06 case, to an A.I. and then using the .270 formed to a Sherman?? In other words, I think It may have been 11% increase from a std. 6.5-06 to a 6.5 Sherman. That would make sense. I think that Retumbo and RL 25 might be your two best choices, velocity wise, with the heavy bullets. Keep the info coming......Rich
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  #17  
Old 02-28-2013, 04:57 PM
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Join Date: Dec 2010
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Re: 270 Sherman

I managed to get out to the range today to pressure test a few loads. The snow wasn't too deep and I didn't get stuck. Kinda cool and breezy though.

I loaded up some 7828ssc from 56 to 60.5 grains with a matrix 165g with a coal of around 3.51". The last 2 started to flatten the primers a bit but no brass flow and bolt lift was easy throughout.

The listed max for a 160g bullet in a 270win with IMR7828 is 56g, my measured capacity difference was 9% from a 270WIN to a 270 Sherman so adding 9% to 56g is 61g. The primers started flattening a little at 59.5 g so that kinda relates to what I am seeing.

The last 4 shots went into .453" and that is with half grain increments from 59g to 60.5g of 7828ssc and a WLR primer. Not bad considering I was cold and firing pretty quickly.

This weekend I will probably load a few more up and bring along the chronograph to check velocity. I am looking to see somewhere around 2850-2900fps with the 60g load and a 165 matrix...maybe more.
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  #18  
Old 02-28-2013, 05:23 PM
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Re: 270 Sherman

We run 56gr of 7828ssc with the 165 Matrix in a 270 win and it runs 2835fps with a 26in barrel and just stack them up but it's the top end pressure wise, had really good luck with BR2's with 7828 as well.
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  #19  
Old 02-28-2013, 05:58 PM
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Join Date: Dec 2010
Location: SD
Posts: 371
Re: 270 Sherman

The barrel on this rifle is a little short at 22". I didn't realize it was that short before I started the project but it is more for fun than anything(I have 2 270WSM's). I'm not likely to use it for much other than gong banging or a deer or two.

It is supposed to be a balmy 25 degrees tomorrow with a north wind at 5mph so maybe I will chrony some loads tomorrow and Sat..
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  #20  
Old 03-01-2013, 08:42 PM
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Join Date: Dec 2010
Location: SD
Posts: 371
Re: 270 Sherman

Had an "Unfortunate Incident" today while working on some loads.

It all started out at the range yesterday when I tipped over my plastic shellcase and 5 of my cases fell out that had been shot. They fell into the hole in the big wire spool I was using for a bench. I managed to fish 4 of them out of the snow inside the spool with the antenna off my truck.

This left me with 19 formed cases.

The next step came when I was reforming and polishing the decapping stem on my die. I finished with the changes to the stem and promptly put the stem back in the die and then decided to run a unformed 270 case through to check out how the modified stem worked. The stem worked great!

So, here I am with a 270 case that has been basically neck sized down to where the shoulder would start on the 270 Sherman. Then I am looking at the 19 cases sitting in the loading block and start thinking -hey load up some 700x and cream of wheat and TP and form up another case. Problem is that I did not form a false shoulder by necking up the case to 308 first!

So , I load up the case and stuff it in the gun and pop it off and open it...the case is in the chamber. Well, If I would have stopped right there and just ran a dowel down to tap out the case everything would have been hunk-dory.

Nope, I didn't do that! I shut the bolt down and attempted to pull out the case. Well, the case wasn't stuck...BUT, the case when popped off moved ahead about .100 from the firing pin and then the case walls held the case there and THE PRIMER FELL OUT.

Well, the primer wedged in the bolt. Bolt wouldn't open. If I was smart I would have just jiggled the bolt until the primer moved out of the way and the bolt would have opened.

No, not me! I grab the rubber mallet and give the bolt handle a whack...and got to spend the next 3 hours welding the damned thing back on and re-finishing the bolt!

The case came out and was formed fine except the shoulder is about .100" back from where it is supposed to be. The primer pocket is nice and tight. It looks just fine. The primer would look just fine except it is now a half-moon shape from being wedged in the bolt.

SO, MAKE DARNED SURE YOU MAKE A FALSE SHOULDER NEXT TIME DUMMY!!!

Anyway I'm glad that was all that happened and at least I found out my bolt handle wasn't attached that great. I guess people have them tig welded on because they fall off sometimes. And I didn't blow anything up! And I learned what happens when you don't have anything holding the case back against the bolt when fireforming!

I knew all along that shooting a full power 270 in it would probably be NOT-GOOD.

Anyway, when I got done with the "Unfortunate Incident" I loaded up some loads for pressure testing and chronographing tomorrow including: Magpro, RL22, N560, and some more with 7828ssc.
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  #21  
Old 03-01-2013, 09:17 PM
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Join Date: Dec 2008
Location: Northern Id.
Posts: 3,103
Re: 270 Sherman

Quote:
Originally Posted by CogburnR View Post
Had an "Unfortunate Incident" today while working on some loads.

It all started out at the range yesterday when I tipped over my plastic shellcase and 5 of my cases fell out that had been shot. They fell into the hole in the big wire spool I was using for a bench. I managed to fish 4 of them out of the snow inside the spool with the antenna off my truck.

This left me with 19 formed cases.

The next step came when I was reforming and polishing the decapping stem on my die. I finished with the changes to the stem and promptly put the stem back in the die and then decided to run a unformed 270 case through to check out how the modified stem worked. The stem worked great!

So, here I am with a 270 case that has been basically neck sized down to where the shoulder would start on the 270 Sherman. Then I am looking at the 19 cases sitting in the loading block and start thinking -hey load up some 700x and cream of wheat and TP and form up another case. Problem is that I did not form a false shoulder by necking up the case to 308 first!

So , I load up the case and stuff it in the gun and pop it off and open it...the case is in the chamber. Well, If I would have stopped right there and just ran a dowel down to tap out the case everything would have been hunk-dory.

Nope, I didn't do that! I shut the bolt down and attempted to pull out the case. Well, the case wasn't stuck...BUT, the case when popped off moved ahead about .100 from the firing pin and then the case walls held the case there and THE PRIMER FELL OUT.

Well, the primer wedged in the bolt. Bolt wouldn't open. If I was smart I would have just jiggled the bolt until the primer moved out of the way and the bolt would have opened.

No, not me! I grab the rubber mallet and give the bolt handle a whack...and got to spend the next 3 hours welding the damned thing back on and re-finishing the bolt!

The case came out and was formed fine except the shoulder is about .100" back from where it is supposed to be. The primer pocket is nice and tight. It looks just fine. The primer would look just fine except it is now a half-moon shape from being wedged in the bolt.

SO, MAKE DARNED SURE YOU MAKE A FALSE SHOULDER NEXT TIME DUMMY!!!

Anyway I'm glad that was all that happened and at least I found out my bolt handle wasn't attached that great. I guess people have them tig welded on because they fall off sometimes. And I didn't blow anything up! And I learned what happens when you don't have anything holding the case back against the bolt when fireforming!

I knew all along that shooting a full power 270 in it would probably be NOT-GOOD.

Anyway, when I got done with the "Unfortunate Incident" I loaded up some loads for pressure testing and chronographing tomorrow including: Magpro, RL22, N560, and some more with 7828ssc.
Holy crud Bruce. Talk about a bad hair day! I am old enough not to laugh too hard as I have had a few of those as well. Better luck tomorrow. I am anxious to hear the GOOD results.......Rich
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