Pressure before veloctiy...help with the 7mm Creedmoor and 156 Cauteruico's

[Mgordon]

Shooters,

I have been working on some new loads for the 7mm Creedmoor and I'm having trouble getting velocity with on one load because I run into pressure first. The goal is to push high bc (.630) 7mm bullets with high velocity (2900 FPS) in a true short action, high capacity configuration. Here are the details.

Bob Cauteruico 7mm 156 gr VLD's. .2853" diameter .630 claimed BC. .48 cents a piece.
Varget powder
Hornady 6.5 CM brass necked up
Federal 210M primers
26.2" Rock Creek 7mm 1-8.5" 5R chambered in 7mm Creedmoor.


I did a vertical latter test at 400 yards with 39 gr of Varget to 43.5 gr of Varget. I settled with 41.8 gr of Varget because it feel in a great vertical accuracy node. The problem is Velocity was only at 2750 FPS. I'm getting 2810 FPS with my Hornady 162 A-Max load with 40.8 gr of Varget. So I'm getting 60 FPS lower with a lighter bullet and 1 more grain of powder....???

This bullet acts like a tight bore configuration due to the .2853" diameter. I am not sure if I should try a slower burning powder because Varget is getting into pressure before achieving good velocity or what? Varget and CFE223 and other faster burning powders have always been the choice for the 7mm Creedmoor, you just cannot get enough H4350 and such into the case to achieve pressure before compression becomes a problem with the 162 range bullets.

2750 FPS with a .630 BC 7mm bullet is not bad, but this thing would kill 260's and other 6.5's while banging the hell of out steel if I can get them up in the mid to high 2800's FPS with out real pressure. Let me know your thoughts.

Mark

 

[sakobob]

if you can find some maybe rl 17, if not i know a guy that will give some up.
you should be able to get enough in the case,when we tested it with 162's we reached pressure
and gained speed with a little room left in the case, but stayed with varget it was a easy 2820 and he was
happy with that.

 

[Fredo0621]

Any chance of trying 2000MR? In all cartridges that use Varget it always yields higher veloctity. Just have no info on the 7creed.

 

[sakobob]

thought of another powder to try,imr4007sc .
i have some 2000mr if you need some.

 

[Mgordon]

I'm planning on trying CFE223. We will see.

Sent from my HTC6435LVW using Tapatalk 2

 

[turbo54]

PP2000 and CFE should be tried.
[MENTION=14025]Mgordon[/MENTION]

I've got 3/4 bottle PP2000 and RL17 if you'd like to try them.

As 7creed and 708 are rather similar, its not surprising they both have this same issue.

Though I've yet to try it, I've often thought about blending Varget and H4350 for 708 because of this same issue.

 

[Frank Green]

Mark, What are the bore and groove dimensions of that Rock barrel. If it's a tight bore and those bullets are fat like you say they are it's going to be a good guess that these are adding up to the pressure problems etc....

The old saying goes tighter is slower and looser is faster applies.

George had a barrel (not ours) and was blowing 50% of his primers (believe it was a .243AI). The bore and possibly the groove was tight. He asked me what could be done as he didn't want to pull the bullets from all the loaded ammo he had and redo it all.

I said lets make a barrel with a standard bore size (not tight) and will make the grooves to the high side of the tolerance and then lap the barrel. He put the barrel on the gun and he said the loads were still hot but he wasn't blowing primers anymore and the gun shot like a million bucks.

With all that being said the velocity your getting given the case capacity etc...is pretty good in my book.

Later, Frank
Bartlein Barrels