Tight chamber or headspace issue?

[Texas Solo]

First outing with new Savage 12FTR. To serve scope, I started with Fed GM 168. Bolt was tight to close. I shot 3 rds & had the scope on.

Then I tried some loads with 155 ELD-M. New Hornady brass. These were also tight, but not as bad as the Fed GM. I shot multiple rounds while conographing. All were a bit tight to close bolt and primary extraction was stiff too.

Got home and measured everything.
The factory GM 168 grew only .005 in OAL brass length. 2.005 to 2.010.
New Hornady brass was the same.

Next I measured the brass to the datum line with a comparator. There was ZERO growth in either the factory Fed GM or my Hornady brass reloads.

This has me concerned. I'd like to try a .002 shoulder bump, but my die is already screwed down so the press doubles over. Now what?

It just seems like the headspace is too short. I'd rather try some shoulder bump before I consider having to correct headspace.

Is there a special die for shoulder bumping 308?

Appreciate your thoughts.

 

[Bill Norris]

Following. Redding does make a body die for .308.

 

[Ggmac]

make one . Take a Lee fl die and cut .010 off the bottom . That should be enough given manufacture tolerances . JUST BE SURE TO MARK THE DIE !

 

[WSnyder]

Sand a couple of thousands off the top of your shell holder and try it. If not enough take a couple more off and try it. Repeat as necessary.

 

[Martin52]

Slight chance the chamber neck is tight, how does the neck on a fired case compare to a loaded round ?

 

[Karlandco]

Strip the bolt, load a sized piece of brass into the chamber..empty of course. That should tell you if the shoulder is touching.

If it's the neck, while advancing the bolt forward towards the closed position you'll feel resistance. If shoulder resistance will be felt at the end of the stroke while camming over.

This assumes the brass has been trimmed to length.

 

[txtaxman]

First outing with new Savage 12FTR. To serve scope, I started with Fed GM 168. Bolt was tight to close. I shot 3 rds & had the scope on.

Then I tried some loads with 155 ELD-M. New Hornady brass. These were also tight, but not as bad as the Fed GM. I shot multiple rounds while conographing. All were a bit tight to close bolt and primary extraction was stiff too.

Got home and measured everything.
The factory GM 168 grew only .005 in OAL brass length. 2.005 to 2.010.
New Hornady brass was the same.

Next I measured the brass to the datum line with a comparator. There was ZERO growth in either the factory Fed GM or my Hornady brass reloads.

This has me concerned. I'd like to try a .002 shoulder bump, but my die is already screwed down so the press doubles over. Now what?

It just seems like the headspace is too short. I'd rather try some shoulder bump before I consider having to correct headspace.

Is there a special die for shoulder bumping 308?

Appreciate your thoughts.

The reason to bump the shoulder is to create space "where needed".

There are two other measurements to take on new, fired, and full length sized cases: Diameter at the shoulder and at 0.2" from the base of the case.

These measurements will help you make a decision regarding modifying the die or shell holder vs resetting the headspace. Doesn't your rifle have the barrel nut system? Do you have a headspace gauge?

 

[Coyotefurharvester]

Rent headspace gauges, clean chamber. Then you are not guessing on the length.

 

[Karlandco]

Rent headspace gauges, clean chamber. Then you are not guessing on the length.

Great advice.

 

[K22]

If your rifle has difficultly in chambering and extracting factory ammo, I would investigate the reason before doing anything else.

First, I would check the headspace of the rifle with go / no go gauges. All rifle smiths have these and for a nominal fee, they'll check it for you.

Also have him inspect the chamber for burrs, tool marks and other imperfections which may be hindering smooth chambering and extraction. I had a Vanguard with this problem making chamber and extraction very difficult. The smith polished the chamber, and it functioned fine. One sure sign of this is pronounced wear marks on the case.

 

[spudgun]

I had the same thing when I bought a used Savage 12 F/T, 6.5 CM. I have been shooting my other savage with a Brux barrel and had no issues with closing bolt and extracting the brass..

My first shot with the used Savage 12 was it was hard to close the bolt and after the shot, I could not lift the bolt handle to extract it and needed a rubber hammer to beat the bolt back.

Tried a second shot and same thing.

Came home and started checking my loads and brass. All my reload worked fine in my other Savage 12 with the Brux barrel.

Measured my brass at the base and found that it was .003" larger than factory brass.

Bought a small base die and all issues went away. My FL die just was not sizing the base far enough down to fit the tight chamber. You may want to check into a SB die set.

Another issue arose about 2 months ago. I started having hard bolt close issues on both my 6.5's. It was like the cases were too long in the shoulders. Checked some other brass that I had resized earlier and no issues with them.

Did some checking and found that 1 of my 2, RCBS shell holder was .002" thicker that the other which was causing the shoulder to be longer causing the hard bolt close. Sanded .002 off the face and now the bolt closes like butter. Must of switched them at one point.

Good luck

 

[doctorh]

First outing with new Savage 12FTR. To serve scope, I started with Fed GM 168. Bolt was tight to close. I shot 3 rds & had the scope on.

Then I tried some loads with 155 ELD-M. New Hornady brass. These were also tight, but not as bad as the Fed GM. I shot multiple rounds while conographing. All were a bit tight to close bolt and primary extraction was stiff too.

Got home and measured everything.
The factory GM 168 grew only .005 in OAL brass length. 2.005 to 2.010.
New Hornady brass was the same.

Next I measured the brass to the datum line with a comparator. There was ZERO growth in either the factory Fed GM or my Hornady brass reloads.

This has me concerned. I'd like to try a .002 shoulder bump, but my die is already screwed down so the press doubles over. Now what?

It just seems like the headspace is too short. I'd rather try some shoulder bump before I consider having to correct headspace.

Is there a special die for shoulder bumping 308?

Appreciate your thoughts.

Sound like your headspace is a little on the tight side.If you don't have a go gage take a new piece of brass chamber

First outing with new Savage 12FTR. To serve scope, I started with Fed GM 168. Bolt was tight to close. I shot 3 rds & had the scope on.

Then I tried some loads with 155 ELD-M. New Hornady brass. These were also tight, but not as bad as the Fed GM. I shot multiple rounds while conographing. All were a bit tight to close bolt and primary extraction was stiff too.

Got home and measured everything.
The factory GM 168 grew only .005 in OAL brass length. 2.005 to 2.010.
New Hornady brass was the same.

Next I measured the brass to the datum line with a comparator. There was ZERO growth in either the factory Fed GM or my Hornady brass reloads.

This has me concerned. I'd like to try a .002 shoulder bump, but my die is already screwed down so the press doubles over. Now what?

It just seems like the headspace is too short. I'd rather try some shoulder bump before I consider having to correct headspace.

Is there a special die for shoulder bumping 308?

Appreciate your thoughts.

Looks like your headspace is on the tight side. Need a go gage to see if it will let bolt close.if you can't get go gage take a new piece of brass and try to close bolt. Should be no or very little drag on bolt closing. If you are not getting any shoulder bump when resizing fired brass you can use a shim in your shell holer