7mm saum pressure issue ?

[buster2765]

Let me start by saying i'm a newbie & need a little advise. My first 7 saum is a savage pta with 28 inch cbi bull barrel & shoots great with 210 fed ,60.5 gr 4831sc & 180 berger hy.(2950fps) no pressure sign. 7saum # 2 not the same, this one is another savage with a benchmark 26 inch with a .319 neck a little tighter than my cbi. nosler fits fine, rem. needs a slight turn.This is my issue, saum #2 (benchmark) afer about the 3rd firing you need to beat the bolt open, with a click at the top. this is with 59 to 60 range 4831sc at around 2800 to 2850fps(same 180 bergers) I ordered a Neil Jones custom die hopeing it would help. ps no other sign of presure Any advise thanks Dar

 

[pmarauder]

You are either not getting enough sizing somewhere on the case, or you have a carbon ring build up. How many rounds down the benchmark?

Can you measure your headspace accurately? Im sure you know what im talking about, but if not..... I can walk you thru it. basically, you need to measure 3 places on your fired case to see what the fired case dimensions are. Then, adjust your sizing die to bump the headspace back .001 from fired dimension. Now pull your firing pin out of your bolt and see if you can chamber that sized round without any resistance on closing the bolt. If there is resistance...... adjust your die to size another .001 of head space bump and so on until you can just close the bolt without any resistance.

Derek

 

[buster2765]

Thanks for your reply Derek. the barel only has 200 rounds & have has this from day one. As far as headspace i push the shoulder back 1 to 2 thou each time (fl resize) but i can push it back alot more than that and by the 4th or 5th firing you cant even get it in the chamber is a benchmark barel specs tighter down the lenght of the case (match) or just the .319 neck ?

 

[pmarauder]

What does your loaded round measure at the neck OD?

It appears that you have a sizing issue you need to address. Can I assume that you turned a bit off your necks? I would recommend that you turn the necks down to give you at least .003 neck clearance with your chamber. so your loaded round would measure .316 at the neck.

So go back and read my first reply..... 1 to 2 thou of head space bump may not be enough. you need to bump the head space back until you can put that stick of brass in your chamber and with the firing pin out of the bolt......the bolt handle should fall on its own without you manually closing it.
Sounds like your sizing die is not a good match for your benchmark chamber...... none the less..... you need to keep bumping it until your bolt will close freely.
Derek

 

[turbo54]

The case length from head to datum isn't the problem, as the OP is measuring and setting the sizing die appropriately.

Sounds likely to me the body is too large down by the .200" line, which is causing the sticky primary extraction (the "click" the OP mentions).

He needs a small base sizer.

 

[XTR]

The only time I've had that problem with my 308s has been when I got brass fired in one rifle and only neck sized mixed in with the loads for a different rifle. Had to tap that one out with a cleaning rod, but every time I've ever had a problem extracting it was sizing on the body, not the neck or the shoulder. I've had shoulders make it harder to close, but not problems on extraction/opening

 

[pmarauder]

The case length from head to datum isn't the problem, as the OP is measuring and setting the sizing die appropriately.

Sounds likely to me the body is too large down by the .200" line, which is causing the sticky primary extraction (the "click" the OP mentions).

He needs a small base sizer.

Perhaps..... but the only way to be sure is to begin and bump the head space of the fired brass until it will chamber without resistance. Clickers on the other hand is a completely different issue and will require a different plan of attack.
If you read busters second post, he says that he cant even get it in the chamber, and has to beat the bolt open.....RED FLAG
My advice is still the same. and you may also need to look into annealing your brass in order for it to "bump" properly.

Derek

 

[buster2765]

one other thing is that i'm using the same fl sizing die on both saum rifles redding s type. bumping the shoulder back 1 to 2 thou works great with the cbi barrel but even if i bump back 6 to 7 thou (benchmark barrel)still closes hard(3rd 4threload) so its not the shoulder getting in the way. My origional thought after doing a little reading was that the die was not sizing far enough down the case, i then was going to get a small base sizing die & try that but could not find one for 7saum. So i ordered the Neil Jones die, worst case i get a great fl sizing die

 

[mac86951]

I'd recommend Cerrasafe the chambers for comparison.

I've heard of a 7RSAUM where the chamber reamer didn't float the pilot so the throat was rifled for 50% (only on one side).

This made for a serious pressure issue using 180 Bergers loaded at same specs to the other barrel manufactured at the same time.

Problem has been resolved using a finishing throat reamer for 7mm SAUM by hand (and going very slowly).

-Mac

 

[AKShooter]

Sent you a PM, I have a benchmark 7saum as well, couple questions, want to compare notes. Thanks