New rifle, old brass...

[Streeker59]

After alot of soul and wallet searching, i just couldn't justify spending £2+ k on a TRG..

So... I've bought a Tikka T3 Super Varmint in .308. 20" barrel as most of the time i don't shoot beyond 600 yards so i'm not worried about keeping rounds supersonic to 1000 yards. I already have a T3 varmint in .223 and it's a cracker of a rifle. Next year i'll add a Robertson stock to the .308 as the existing stock is a little flimsey. Any way, i digress..

 

I have a that which promotes growth and vigour load of Lapua .308 brass that was used in my previous rifle, a sako 75.

I've full length sized the brass and trimmed to 2.05". I tried some of the empty cases in the Tikka chamber and the bolt is really hard to close.

I chambered a new case and that was fine.

Next step was to compare case dimensions with a dial caliper. After sizing, the fired rounds are identical to the new brass.

Shoulder diameter is 0.45". Max diameter at case base is 0.466".

I'm wondering if the resizing die is not bumping the shoulder back enough..

Next step was to highly polish a sized case with Brasso wadding and try it again in the chamber to see if any scuff marks may show up the problem.

 

The only obvious marks were 2 rings on the case shoulder. One ring a third of the way down the shoulder from the neck and the other close to the shoulders widest part.

The case dimensions had also changed. The shoulder diameter and base diameter were now .001" smaller than before i loaded the case into the chamber.

Now smaller than a brand new unsized case that loads without a problem.

Am i right and the the shoulder isn't being bumped back enough ?

Your help guys would be appreciated...

 

I can only assume from this that the sizing die isn't bumping back the shoulder enough.

The die is an RCBS competition full length jobby and it's correctly installed into the press so the die base is just touching the case holder.

As a final test, i chambered a Samson ( IMI ) factory round whose shoulder and base dimensions are the same as a resized case. That loaded just fine albeit with a little resistance.

 

Grant.

[Streeker59]

Sussed it !!!!!

I've always neck sized my 308 rounds and forgot that i can adjust the shoulder bump depth as the neck die is a Redding "S" type die.

Installed the die. Wound the adjuster down a bit at a time until the case chambered without complaint....

 

I was crapping myself for awhile thinking that 500 lapua cases were gonna have to be binned..

I know that ideally new rifle new brass but at £80 a hundred i really didn't want to bin the lot..

 

I guess that my redding FL die will get the heave ho though. Surely it should have set the shoulder at the correct angle???

[Scotch_egg]

Grant,

 

 

Not a .308 but I recently ran a .223 case through my redding .20 tactical FL die in my redding co-ax press. It would not chamber in my rifle. However when I put the die in my old lee press and ran a .223 case through it chambered perfectly. It appeared to bump the shoulder back better.

 

From this experiencr It sounds like it's the shoulder not being bumped back.

[Vermincinerator]

Apart from needing to bump back the shoulder there is often a situation where the case head has expanded enough to stop complete chambering in a new rifle or chamber even after F/L sizing.

The problem is that with a standard F/L sizing die there is a small portion of the case just above the extractor groove that never gets sized.

To combat this many competition shooters have been using what are called "small base dies" which cure this problem.

These dies are available in common competition cartridges from Redding.

 

Ian.

[baldie]

Very good they are too Ian.

We tend to use them a fair bit for practical rifle ammunition. They ensure reliable feeding with ANY brass, and are virtually a must have for some of the straight pulls, in either .223 or .308.

Some commercial chambers these days are cavernous.

[Elwood]

Apart from needing to bump back the shoulder there is often a situation where the case head has expanded enough to stop complete chambering in a new rifle or chamber even after F/L sizing.

The problem is that with a standard F/L sizing die there is a small portion of the case just above the extractor groove that never gets sized.

To combat this many competition shooters have been using what are called "small base dies" which cure this problem.

These dies are available in common competition cartridges from Redding.

 

Ian.

I had that exact problem with some once fired Norma 6BR brass, I ran them through a small base body die and they chambered perfectly, in fact Ian I think it was you who informed me to do it.

 

I had the same problem with 7 WSM brass but unfortunately there isn't a small base die available for this calibre.