Hitting pressure early in 6.5 PRC

[skookum]

The SAAMI spec says .532 at the Web and all my brass measures .533 after firing, I'd say that's pretty tight...

 

[JAYgs8163]

The SAAMI spec says .532 at the Web and all my brass measures .533 after firing, I'd say that's pretty tight...

Have you resized yet?

 

[skookum]

Have you resized yet?

No thats 1x fired

 

[JAYgs8163]

No thats 1x fired

Curious to see what it resizes to.

 

[Bob Wright]

As long as a new bullet drops in a spent case, you're pretty good in the neck. Your numbers back that up. I run .002 per side on a 7 mag and 280AI. So, .004 difference between loaded necks and fired necks.
If your reloading is a smooth stroke while seating, you shouldn't have to worry about a donut at the neck shoulder junction. My 280AI developed one immediately. Ugh....pressures went up dangerously...

 

[spin-one]

When I had my 6.5 PRC built I was lucky enough to find ADG brass. I started out loading 143 gr ELD-x and because go ADG brass is heavier I couldn't reach max load without hitting pressure but was getting velocity in the mid 2950. I switched over to Barnes LRX 127gr and had no problem reaching the max recommended grains of powder ( H1000 ) and increased the velocity to 3090.

 

[kfreeze]

I think you just have a one of those barrels. All of the numbers confuse people. It's the lands, grooves and throat that cause the most change to your loads. The lot of powder can also play big role in it too sometimes. (Why I don't buy one lb of powder at a time, and try to buy at least 5lbs off ogf the same lot#) What you are seeing is normal. How is the case fill? Maybe try retumbo or n570?

 

[skookum]

Curious to see what it resizes to.

Me too. I have to take the family camping unfortunately so this will have to wait until next week. Darn the hard luck anyway. Haha

 

[skookum]

I think you just have a one of those barrels. All of the numbers confuse people. It's the lands, grooves and throat that cause the most change to your loads. The lot of powder can also play big role in it too sometimes. (Why I don't buy one lb of powder at a time, and try to buy at least 5lbs off ogf the same lot#) What you are seeing is normal. How is the case fill? Maybe try retumbo or n570?

That stuff is magic fairy dust. Maybe someday. Hahaha

 

[BrentM]

How much growth would be considered a tight neck? Loaded measured to .291 and after was .297-.298 depending on how I held my mouth while measuring.

Your chamber is saami.

 

[BrentM]

I'm being a little dramatic. The gun is shooting fine at a velocity that I was hoping for just more pressure than I would like. Based off the wheeler video it sounds like I might not actually be hitting pressure as much as its just a tight chamber. The load i am settling on for now is 2960 avg which is totally fine with me but I am going to see what I can do in the accuracy department and try another powder. Its right at 1/2 moa which is acceptable but I want to see if the gun will do a little better, that's part of the fun for me anyway. I will say that this is the 2nd McGowan barrel I own and neither have impressed me thus far but thats a sperate topic.

You have a new barrel running mid 29's with a 143. Seems pretty spot on to me. It will speed up around 150-200 rounds likely.

 

[Lefty G-gear]

I have a newly barreled 6.5 PRC that I am hitting pressure with a modest load of H1000 and 143gr ELDs. Book max said 59.0 gr and in my experience with every other gun I have ever shot the book max is still under what the gun will actually do. I started hitting pressure at a modest 56.5gr of H1000, Nosler Brass, and a FED 215. By 57.5gr I gave up when I started getting a heavy bolt lift. Any ideas on why? I know every gun is a little different but this seems extreme. Could the chamber be a little too tight?

I wonder about the chamber or even the barrel being too tight?
Does it need to be 'throated' ?
Is there a way to slug a bullet through the barrel - then mic the bullet diameter and grooves?

 

[Subzero]

Jump is .050" that i settled on. And now that I think about it some of the Hornady factory ammo was a bit tight like a handload that didn't have enough shoulder bump.

It sounds like your chamber is a little too tight.
Is your barrel shouldered or mounted with a barrel nut? If it's a barrel nut, then it's a pretty easy fix.
If your velocities are with a 24" barrel then it's not too bad as it is. I would only worry about being able to setup your die tight enough to fl size your brass smaller than your chamber.

 

[orifdoc]

If the bolt is heavy to lift, you are exceeding pressures, plain & simple. Don't rationalize it away! You might be able to chew through a hundred different case and chamber variables and eventually sort it out...... about the time the barrel is 1/2 shot out.

My advice is to back off and find a lower node or try a different powder. Accuracy trumps a bit of extra velocity 99.9% of the time. I've accepted less than book velocities in plenty of my rifles. As long as they're consistent & accurate, an extra couple clicks at 800 yards is no big deal. Saves a lot of frustration too.