Home Forums Reloading Big Game Rifles Apparent High Pressure with Book Loads ?

I was testing loads for my wife 6.5x55 Ruger MK II the other day and got high pressure signs with under max Nosler book loads. The powders tested were H1000, RL-22 and H4831SC. The other component were Nosler Brass, 140g Nosler PT and WLR primers. I only shot one round from each load because I was getting over book velocity for that load, but lower than max velocity according to the book and ejector marks on the cases. This has never happened before. One primer appears to have leaked and one was almost pierced. At least it looked that way. Bolt lift seemed fine. I pulled the bullets and reweighted the powder and in all loads it was correct. Wondering what could be the cause?

I thought of too short of throat: Nope plenty long and well over what they were loaded.

Improper head spacing maybe that allowed the brass to slam back into the bolt, but again not a problem before. However this was new brass, but a brand I have used before.

Bad primers maybe, but again that higher velocity with a shorter barrel.

I thought my scale was off, but used the same scale right after these were loaded to load .257 Roberts that were spot on velocity and no pressure signs.

Any ideas would be helpful.

You might take a look at dims across the board. First thought comes to mind is a tight chamber and/or thick case wall in the neck.

Sounds like you need to load less than "book max." It happens. Velocity is the best indicator as long as your chrono is accurate. But I've gotten funky chrono ouputs in changing light near dusk.

Ejector marks on the case head are IME some of the best pressure indicators.

You don't happen to load a .277-caliber with 140 Partitions, do you?

This.

Why would you load near book max without working up to it while watching for pressure signs?

That's why we start low and work up. Book max is just a suggestion, and many things can change it.

Reading the OP, it sounds to me like this is a familiar rifle and loads with familiar components and powder charges.

Only if the box was miss marked.

I'm not familiar with the term dim across the board.

That would have blown the primer back into his face and welded the case to the bolt face, and probably blown the extractor and/or ejector.

It would a been a lot more then "showing high pressure signs".

These were not max loads, but starter loads.

The Chono was working well with the other rifle I tested that day.

New rifle, new to you rifle, or old, known rifle you've never had problems with before?

Known rifle we've had for years that never gave a problem before.

Then take it too a gunsmith. We had this happen once. Barrel was "Jugged", and had to be rebarreled.

Same things happened to other forum members here.

It can happen. About 6-7 years ago I bought a box .284 cal 139 gr Hornady SP. Several days later I opened the box to load a few. As I was looking at the bullets something just didn't look right. The 284 cal bullets looked a little longer and thinner than I was use to seeing. After some looking through the bullets I got the calipers and measured. They were roughly 25-30 .264 caliber bullets in that box. I picked up the phone and called Hornady to let them know what I had.

They wanted the "lot" number and a few other things. They called me back a few days later, maybe a week or so, to let me know that there had been a mix up and that their research showed there were more mixed boxes out there, didn't say how many and I was the first one to call about the problem. They sent me 2 boxes for my trouble.

Stuff happens from time to time...

Sounds to me like it might be brass problem.

Have run into production lots of the same brand of brass that were soft and/or heavier than previous batches. More rarely, some have also had thicker necks--occasionally just at the base of the neck, the so-called "dreaded donut." All of the above can cause either higher pressures, or the appearance of higher pressure.

The easiest way to tell if the necks are too thick, either overall or just at the shoulder/neck juncture, is to try to insert bullets into the necks of fired cases. If there's any problem, the bullet won't insert easily, if at all.

The bullets are .262/

One fired case was difficult to push a bullet in, but it did go. The other 2 ha no problem getting bullet in. How does one test for thick neck wall?

With one of these:

https://www.midwayusa.com/product/544254/rcbs-vernier-ball-micrometer-1

That's what I figured. What is considered too thick?

My son had a pressure problem with his 243. It was with the same ammo he had loaded before. He asked around and was told to clean the bore and especially the throat. He used one of the adjustable bore guides cleaning his rifles and a ring of crud had formed in the throat area. He cleaned the bore and fixed the problem. After cleaning my bores with a bore guide my last step is running a patch soaked with denatured alcohol through the bore.