OAL Length Problem

[GaCop]

Received my 6mm BR Norma case for the Sinclair OAL guage. I've run into an interesting problem while using it. I tried my Sierra 107 grain match boat tails and found that when the bullet is seated to touch the lands, only the boat tail remains in the case neck?

The barrel is an EABCO 26" that is supposed to be throated for the 105/107 grain pills. To have enough bullet in the case neck my overall length needs to be 2.420" for the 107 grain and approximately 2.400" for the Sierra 95 grain BTHP.

Has anyone run into this problem? I recently put the rifle together but purchased the barrel back in January when I returned from Afghanistan.

I guess I need to recheck the headspace though I did screw the barrel in to make light contact with the GO guage,or so I thought).

Tom

 

[BlackHawk95]

GAcop. Are your mesurements from the base of the case to the tip of the bullet, or from the case base to the ogive?

I just checked your measurements and if 2.420" is from the case base to the tip of the bullet, It looks to me that the 107MK is about half way in the neck. I just checked my overall length and it is around 2.380". Are the bullets not touching the lands at 2.420"?

I does seem a little long to me. I have a Savage F-class 6.5-284 where the throat is very long like that, to touch the lands with a 139 Scenar tha base of the bullet is halfway up the neck like you describe. It is longer than I would like, but the gun shoots great. The only downside I can think of is, as the throat wears and you move the bullet out to the lands, you will eventually run out of case neck.

I would like to see what some of the other more expirienced shooters say.

Good luck,

Jerid

 

[expiper]

welll Im certainly no expert..but "well seasoned"....Jerods chamber is prolly somewhere around .080 FB,kiff method) and if yours is not touching,or barely at 2.420") until your way out ...try some A-max or the new Berger 105 BT,non VLD) ...both of those bullets shuld solve the problem ..and they are proven match winners....Roger

 

[BlackHawk95]

Expiper, IS free-bore a measurement from the case mouth to the ogive on the bullet?

 

[ODIN]

A light bulb just went off....

I am ordering my first 6BR barrel and I didn't think about bullet length. If I primarily want to shoot 87 grain vmax and 90 grain Sirocco, seated well into the neck, what should I tell the people at Pac-Nor?

Bob

 

[expiper]

Yes...FB is the dim from the end of the chamber,usually .015 +/-) longer than the ctg.case to where the lead or tapered portion of the chamber begins...
I have had much success with FB between .040 and .080 with all bullets up to and including Sierra 107...I have not shot and Sciorcco bullets....so I dont know about them....Roger
OBTW...watch out when talking to the bbl mfg...they will say "we got just the reamer YOU need" and usually have no idea what the gunsmithing will be done with and what really works...beware...make shure they are doing just what UUUU want...or get someone else to do it...!!!!

 

[fdshuster]

If I'm having a barrel chambered, I will give the gunsmith a "dummy" round with the bullet of my choice, seated in the case to the depth that I want, if it's a boatail, the full diameter of the bullet will be at the base of the neck/ heel of the BT below the neck), and it will be throated to those specs. If I'm having my own reamer made, Pacific/ Dave Kiff), I'll send a "dummy" round, and the reamer will be ground to match. Works for me. Why spend big $$$$ on a high quality barrel, and leave it up to the gunsmith/builder to decide your chamber dimensions?

 

[ODIN]

Thanks

I really don't want to hijack "GaCop's" thread but it's kind of similar.

By the way.......The sirocco,Swift) is the only bonded 6mm Bullet I know of, and amazing terminal performance and weight retention on large game.

I will send a couple of dummy rounds to the manufacturer.

Thanks again.
Bob

 

[wal]

GaCop

For your projectiles to be touching the lands how much of bearing surface of the bullet is in the neck of the case?
Sounds wierd that the chamber has too much free bore, unless the gunsmiths reamer had a suitable FB for smaller projectiles and he throated it out to far.

wal

 

[GaCop]

After inserting the Sinclair, I slowly slid the rod forward until it stopped. Pulling it out. the 107 grain Sierra wobbles in the case because only the boat tail enters the neck. Seating the bullet to approximate caliber diameter or about 1/4" gives me a reading of 2.420". I measured from base to tip. I know this is not the best way to measure but, with only the boat tail entering the neck, I was curious what length I would get with the bullet 1/4" in the case neck.

 

[expiper]

wowowo...Tom...it sounds like you have aprox...250"!!!! FB...that is wayy tooo long....Roger

 

[wal]

GaCop

Do you understand what touching the lands is?
Seat a projectile in an unprimed neck sized case as long as possible, shine projectile with 000 steel wool or JB, chamber in rifle the projectile should push back into case. You should also see the lands marks clearly on the bullet. You may already know this but your not making any sense in your thread.
I dont believe your 6mm br has that much FB that you cant get 107gr projectiles to touch the lands.

Wal

 

[GaCop]

Prior to pull the barrel on my BR I checked the chamber closely and noticed debris so thats why my measurements were way off. All is well now using my comparator. Thanks for the responses.

Tom