short throated barrel

[MTBMaine]

I just got a new shilen barrel for my savage 12 and Im finding it has a very short throat. Im trying to load 178 grn A-Maxs, and Im getting a coal of 2.6 (.02 off the lands) with the SP gauge and bullet comparator this is 3.13.

My question is could I get dangerous pressures from the bullet being seating too deep? I know Im going to have compressed powder issues.. The ogive is still well above the neck. Any feedback would be greatly appreciated!

 

[jo191145]

What cartridge? Measured to the ogive or tip?

Always make sure your SP cartridge is releasing the bullet cleanly. I've been fooled with a new set up before.

 

[CatShooter]

My question is could I get dangerous pressures from the bullet being seating too deep?

Differences like these are why we drop loads 10% and work up... if you do that you will never have a problem.

 

[MTBMaine]

Its a .308, and Im measuring base to ogive.

Thanks

 

[fdshuster]

MTBMaine: With the bullets deeply seated, as required by the short throat, also give some consideration to the full bullet diameter making contact with the donuts that will form at the case neck/shoulder junction. If they do form, and the bullets are making hard contact, pressures will increase.

If the throat is too short for the bullets you need to use, consider having the throat length increased with the use of a throating only reamer. Make a dummy round with the subject bullet seated somewhere in front of the neck/ shoulder and use it as a guide for the amount of freebore needed.

That's one dis-advantage of the pre-fit barrels: the maker has no idea what bullet will be used, so how can they know what freebore length to provide?

Your other option would be to check for donut formation regularly, and use the cutting tools to try and remove them, then the bullets could be seated as deep as necessary, but, then you're intruding on case powder capacity.

Just some thoughts for your consideration.

ps: Just learned that it's a 308. I spec'ed my 308 chambering reamer with a .100" freebore length, for a perfect fit with the Sierra 175 MatchKing, which, of course will have a different ogive dimension than your 178 A-Max's.

 

[jo191145]

Seeing as we don't have your exact comparator we do t know exactly where your at.

Reloading manuals use a generic base to tip measurement which should be somewhere around 2.810"
That doesn't mean you need to load to those dimensions that's the generic 308W load length.

I have a freakishly short throated 308 savage factory barrel. A 178 Amax at just touching is 2.803" base to tip. At 2.6" the bearing surface of the bullet is below the case mouth.

Bottom line, your making a mistake somewhere. Happens often.

 

[MTBMaine]

Ok, thank you very much for the replies... Just checked my notes, I was mistaken Im getting a base to tip measurement of 2.75. Not as extreme as 2.6, but still on the short side... pardon the typo..

 

[MTBMaine]

That's one dis-advantage of the pre-fit barrels: the maker has no idea what bullet will be used, so how can they know what freebore length to provide?

I'm finding this out the hard way, I'm also thinking this is my first experience with a chamber thats not to SAMMI specs... Im relatively new to all this, if you haven't guessed. I would have the throat reamed but the 175 grn Berger hpbt work perfect in this rifle, I just can't ever find any...

 

[masterblaster1]

Call Shillen, my McGowan 308 is tight but it works well with the small base sizing die, the "match" chamber will be a bit tighter than most. 2.6 is way too short, you really need to call Shillen.

 

[jo191145]

Ok, thank you very much for the replies... Just checked my notes, I was mistaken Im getting a base to tip measurement of 2.75. Not as extreme as 2.6, but still on the short side... pardon the typo..

That's better bit still short. Unless it's a special order they shouldn't be coming out that short.
You can call shilen. I'd recommend that for sure. Shilen has a lot different reamers. I would guess they also have 0 freebore reamers for customers that request specific freebore. Could be that was used and someone missed a step.


FWIW the 308 Amax line has some of the longest bearing length on the market. Comes in handy when trying to reach the lands in long throated rifles. Not so good with super short throats.

Call shilen and double check your Stoney point methods. The gauge is designed for a light touch IMO but if the case is tight and slightly nonconcentric it can cause the bullet to jam on the side of the throat with light force. I had a little 20 caliber that fooled me for a week or so until I gave it a little harder push and it broke free and showed a normal throat. A little work on the case and that problem went away. Unfortunately, I liked it where I thought it was

 

[MTBMaine]

I spoke with the folks at Shilen, they told me to create a dummy cartridge with the bullet and seating depth I want and they would ream the throat to its spec. I only have to pay shipping, pretty decent of them I thought . I may try some 155 SMKs and see how well they work in this current configuration.