6mm help

[Caleb85]

Can someone tell me what's wrong here? This is a 80gr. Berger HP with a 6mm modified case out of my M700 . It showing 3.382 and SAAMI. Is 2.825. That's a difference of .557!!!

 

[morcey2]

It looks like you have an exceptionally long throat. I'd expect that on military surplus rifles, but that's a little unexpected on anything else. On my 7x57 and 8x57 mausers, all surplus barrels, the throats are extremely long and that's what it looks like when I measured them. Was the barrel throated for the longer bullets? The 105/108 gr Bergers are all about 0.300" longer than the 80 gr flatbase.

Make sure that the modified case is seated completely in the chamber and that the plunger is locks the thumbscrew in place correctly.

If the measurement is correct, load them up to a good nominal length and see how it shoots. If they don't and the twist will handle it, get some longer bullets.

Matt

 

[Caleb85]

It's a older BDL varmint special and I'm just wanting to shoot PDs with it. I can load 42 gr. of H414 with eather 80gr. Berger HPFB or 80gr. Nosler BT and it will shoot one inch is the best I can get it to do, but they have to be short..anything at SAAMI or longer will shoot all over he paper!

 

[AZShooter]

If you cannot get the results you want you could have a gunsmith set it back and rechamber it. What is a 6mm modified?

 

[sakoluvr]

Can someone tell me what's wrong here? This is a 80gr. Berger HP with a 6mm modified case out of my M700 . It showing 3.382 and SAAMI. Is 2.825. That's a difference of .557!!!

So what you you are saying is your throat is .557 shorter than your magazine. Hmm, I recently bought a 1965ish 700 in 6mm Rem, and I just finished making some dummy rounds with a COAL of 2.80" using the 95gr Nosler BT. I didn't bother checking for throat since I figured magazine constraints would limit things right out of the gate. My 2.80" dummies feed and load fine.

Somebody may have done some gunsmithing on your rifle with a throat as short as that. Keep in mind that the long and heavies did not exist when your rifle was made, and the original owner was using short and light bullets kissing the lands.

You may have to get a new tube if you want to shoot the longer VLD bullets.

Correct me if I misunderstood your post.

 

[sakoluvr]

It looks like you have an exceptionally long throat. I'd expect that on military surplus rifles, but that's a little unexpected on anything else. On my 7x57 and 8x57 mausers, all surplus barrels, the throats are extremely long and that's what it looks like when I measured them. Was the barrel throated for the longer bullets? The 105/108 gr Bergers are all about 0.300" longer than the 80 gr flatbase.

Make sure that the modified case is seated completely in the chamber and that the plunger is locks the thumbscrew in place correctly.

If the measurement is correct, load them up to a good nominal length and see how it shoots. If they don't and the twist will handle it, get some longer bullets.

Matt

I am thinking he has a short throat. See my post above.

 

[sakoluvr]

If you cannot get the results you want you could have a gunsmith set it back and rechamber it. What is a 6mm modified?

I think the "modified" is referring to the modified case to check the throat for COAL.

 

[Caleb85]

I think the "modified" is referring to the modified case to check the throat for COAL.

Correct !

 

[Caleb85]

So what you you are saying is your throat is .557 shorter than your magazine. Hmm, I recently bought a 1965ish 700 in 6mm Rem, and I just finished making some dummy rounds with a COAL of 2.80" using the 95gr Nosler BT. I didn't bother checking for throat since I figured magazine constraints would limit things right out of the gate. My 2.80" dummies feed and load fine.

Somebody may have done some gunsmithing on your rifle with a throat as short as that. Keep in mind that the long and heavies did not exist when your rifle was made, and the original owner was using short and light bullets kissing the lands.

You may have to get a new tube if you want to shoot the longer VLD bullets.

Correct me if I misunderstood your post.

No, throat is over a half inch LONGER the. SAAMI Specs. In order to load a bullet to kiss the lands It will be out of the case and powder everywhere !!

 

[morcey2]

It's a older BDL varmint special and I'm just wanting to shoot PDs with it. I can load 42 gr. of H414 with eather 80gr. Berger HPFB or 80gr. Nosler BT and it will shoot one inch is the best I can get it to do, but they have to be short..anything at SAAMI or longer will shoot all over he paper!

It sounds to me like you're losing neck tension as you seat the bullets longer. That can cause the powder burn to be inconsistent, especially with ball powders. Since you're never going to get anywhere near the lands with that particular bullet, I'd just keep your OAL short and start experimenting with other powders. Either H- or IMR-4350 would have close to the same burn rate as H414, but they're a little easier to ignite. Or try IMR4064, my all time favorite for any of the 57mm long cases (7x57, 8x57, 257 Rob) even though it's a little fast for 6mm, it should work well with an 80 gr bullet.

I am thinking he has a short throat. See my post above.

I think you misread his post. The SAAMI Max OAL is 2.825" and when he pushes the bullet out of the modified case to touch the lands, the OAL he would end up with is 3.382" with about 1/4" of air gap between the case and the base of the bullet as shown in his picture.

Matt

 

[Caleb85]

I'm just wondering is the throat and barrel is shot out of this old thing.

 

[Edd]

I'm just wondering is the throat and barrel is shot out of this old thing.

If a bullet will fall that far down the barrel, you can quit wondering.

In a new SAAMI spec chamber, that bullet would contact the lands at an OAL length of about 2.94

 

[sakoluvr]

It sounds to me like you're losing neck tension as you seat the bullets longer. That can cause the powder burn to be inconsistent, especially with ball powders. Since you're never going to get anywhere near the lands with that particular bullet, I'd just keep your OAL short and start experimenting with other powders. Either H- or IMR-4350 would have close to the same burn rate as H414, but they're a little easier to ignite. Or try IMR4064, my all time favorite for any of the 57mm long cases (7x57, 8x57, 257 Rob) even though it's a little fast for 6mm, it should work well with an 80 gr bullet.



I think you misread his post. The SAAMI Max OAL is 2.825" and when he pushes the bullet out of the modified case to touch the lands, the OAL he would end up with is 3.382" with about 1/4" of air gap between the case and the base of the bullet as shown in his picture.

Matt

Whoops! I misread 3.382 to be 2.382". lightbulb I am a *******. Sorry.

 

[morcey2]

I'm just wondering is the throat and barrel is shot out of this old thing.

Do you know the history on the gun? I know that lots of 700s come from the factory with lots of freebore, but that's a little more than I would expect. Have a gunsmith that you trust check it out with a bore scope for a final judgement. If it looks good, but is just long, follow AZShooters advice and have a couple of threads cut off and a new chamber cut. If it looks bad, rebarrel it.

The reason I ask about the history is that someone may have had it throated for longer bullets, but the 1:9 twist of a factory barrel might not stabilize them, thus the previous owner deciding to get rid of it.

Either way, if you want a shorter throat some gunsmithing will need to be done.

Matt