6mm-284 throated long

[sambubba]

I have a 6mm-284 barrel that was set up for a Rem 700 SA using max OAL at 2.800. I have recently installed it on a LA with the 95g NBTip seated where the base of the bullet is even with the neck base. It looks like about .250 difference. When I chrono'ed this morning 53g RL22 and the 95g partition was going 2940 fps. The old throating registered 3300. How many more grains of powder do you guys think I will have to add to get it back to 3300 or beyond?

As a reference point, 58g H4831 and the 75g Hornady spitzer only made 3300.
I was wondering if using .240 Weatherby data would be more in line? Any ideas would be appreciated.

Craig

 

[BountyHunter]

You can email Randy Robinett at BIB bullets and buy a handfull of his 95 and 108 gr FB bullets. He can be found on BR central.

They are much longer than a BT and would fit this throat and very very accurate. Be advised that they do have a pressure ring and require that the ring be in the case neck, but shoot great. They also routinely like about .003-.004 neck tension.

BH

 

[Tyler Kemp]

That is just amazingly slow, I understand losing some velocity but that is a huge amount. Are you sure it wasn't the chrono?

 

[Fiftydriver]

Was that 3300 fps reading from the barrel when it was new or was it just before you pulled it off the short action?

If it was from when it was new, likely, you have a decent amount of throat erosion and that will also add to the drop in velocity compared to when the barrel was new.

Seating the bullets out will certainly drop velocity for a given load. There is no way for us to tell you exactly how many grains of powder will need to be added to get your load back to 3300fps or if that is even practical. Should be, 3300 fps with a 95 gr bullet is not overly impressive out of a 6-284 but every barrel is different.

Start with your 53 gr load and add 1/2 grain at a time until you reach your 3300 fps level or stop if you start to see pressure signs before that.

 

[sambubba]

The barrel had about 100 rounds in it while in SA configuration, so total count now is about 175. The chrony battery is suspect and will be replaced, but 2 other rifles showed normal velocity readings for their loads. I was thinking that John Barsness had written somewhere that when you seat one out this long in a long throat, that you gain at most two grains of powder. Thanks for the replies.

Craig

 

[Fiftydriver]

YOu will probably gain more then 2 grains of powder volume depending on what powders your using of course.

Your throat should still be pretty fresh so that should not be the problem. I would just put a fresh battery in the chrono and work up 1/2 grain at a time until you reach top working pressures or your velocity goals.

Keep us posted, interesting problem. Would like to hear how it works out.

 

[Tyler Kemp]

FYI, I am getting 3400 fps from the same weight bullet in a 6mm AI with no pressure. The 6-284 is a bit more overbore, but IMR 4831 did the trick for me. RL 22 didn't do good with any bullet I tried.

 

[sambubba]

I've got two 6mmAI's and I agree with you totally. One of them is a 26" Shilen in a Rem 700 SA and it will shoot like a bench gun, and the other is consistent in the 2's and 3's for three shot groups. The 6AI is one of my favorite cartridges. I am trying this experiment on a LA with the long throat because it is a good barrel. I appreciate your reply Tyler, and all the rest of those who responded.

Craig