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.

It was clean, but I'll check that. Maybe I missed something.

Just a Hunter - from what I saw in your first post, I think you have two separate problems, neither of which has been mentioned yet.

#1 - get rid of the WLR primers. They have been cracking and leaking like that for at least the last 10 years, it's a known problem that I think Winchester still hasn't fixed, because people keep using them anyway. I have several pitted bolt faces because of them, and it's not related to high pressure, just bad primer cups.

#2 - You need to measure the headspace on your sized brass, especially with new brass, don't just guess and turn the size die in 1/4 turn ( or whatever) past touching. I'd bet lunch you'll find headspace is a little too short with that new brass and is causing false pressure signs. Measuring headspace is easy if you have a digital caliper, and while it's easier with the right tool, you can do it with just an empty 9mm pistol case inverted over the rifle case neck. Compare to your fired brass from that chamber (with primer removed!) and set headspace back .001-.002".

Thanks Yondering

Just a Hunter,

The necks are too thick for THAT chamber when fired brass won't allow bullet to be freely inserted into the necks.

Or, you may with to just try some different brass, or some factory loads.

If it still shows excessive pressure with Winchester brass, or factory loads, you know it's not a brass or ammo issue but a rifle issue.

I'm

I'm reading what you are saying about the Winchester primers. Man I have a lot of those.

The headspace might be right. I have a .284 that gives false high pressure signs too with new brass, but it hasn't shown an increase in velocity or bad primers so that confused me.

Thank you Mule Deer. The bullets go into the fired cases so that must not be it.

antelope sniper

I may have to do just that. Also I am thinking of trying a lighter load or reloading the fired cases and seeing if the headspace has been corrected by the firing. Sound idea or stupid?

You are already at a minimum load.

Now it's time to start experimentally removing variables.

Year back we had a similar issue with Mom's rifle. We swapped out our ever trusty hand loads for some Remington factory loads. When the issue didn't go away, we knew it wasn't an ammo problem.

You've eliminated many of the low cost ammo based usual suspects from the list. Now it's time to test if it's the rifle.

It sucks about the Win primers, I hear ya; I've got a couple cases of them myself that I won't use. Too bad, cause I liked them before they had problems.

Excess headspace will show false pressure signs, guaranteed. It's really simple to measure though to be sure, just compare to fired brass in that chamber, as long as it's not from a really mild load with the primer backed out. (When the primer is backed out in a mild load, the shoulder is bumped back.)

Here's picture to show what I mean. Zero the caliper on the fired case, then measure the sized case. The measurement is between the case head and the middle of the shoulder. This one is adjusted correctly, the caliper measurement shows the shoulder has been bumped back .002". You can use a fired 9mm case, something like a Hornady headspace comparator, or make your own like I did.

I do have some factory loads that I'll try.

Thanks Yondering

Have the same issue with a stock barreled military Swede. Assembled some ammo in new brass for a ladder assay. Less than halfway through the low to high load run I began getting bolt lift pressure indications. Did not have a chrony along, so I'm just going with the lighter load for now. Did not even attempt to fire any of the upper end loads. As I was moving up the ladder, however, every slug was punching the same hole.

Will do some anal brass prep after I get through an initial firing then start some intensive investigations into cause.

Good luck,

I did the headspace measurements with the 9mm case as you suggested since I don't have .26 for my comparator. The difference between a new case and a fired case was .0035

That should be just fine; if that headspace measurement is correct then headspace is not your problem. Good to know how to check it though.

A known rifle that has never had a problem before! Load a little less and just keep on shooting doesn't sound like very safe advise. I would find the problem before resuming or if I couldn't find the problem I would have a reputable gunsmith help me out. I would start by taking a good look at your brass considering its the new element you introduced along with the problem occuring at the same time

Have you checked the water capacity of the nosler brass. Then compared it to a different brand?

I agree step 1 is shoot some factory loads. If the problem goes away you know you have a problem with components or methods.

If factory bullets work fine then I would start here:

1. measure your bullets.
2. make sure your barrel is clean
3. Check your scale
4. change powders. The same powder in a different lot can have quite different results.
5. check your headspacing.
6. Try different brass
7. Try different primers
8. Take it to a gun smith.

That's a good point. Checking the water capacity or at least just weighing the empty cases compared to a different brand should shed some light on that.

Another consideration is that your Nosler brass might be a bit on the soft side; I encountered that in a different cartridge with their brass.



I'd suggest trying the same load again, but with different primers (because of the known WLR issue) and a different brand of brass. Do the ejector marks go away?

Thanks guys.

I think the first thing I'll do is try factory stuff (Question: I imagine the factory stuff is really light due to old rifles they are fearful of.)

Because of the Primer issue I think I will try some CCIs and see if that is a problem.

The soft case issue. That's a new one for Nosler as far as I have heard, but I think Norma makes brass for Nosler and have heard of some Norma brass being soft.

Also see what the Nosler brass water capacity is.

Nosler contracts from a wide variety of brass makers. If you watch the headstamps the font will vary from lot-to-lot, or at least they used to. Regardless, it's all made to Nosler standards, which typically means it's thick, heavy, and has reduced case capacity. That said, the reduced case capacity should NOT be enough to give you pressure problems with minimum loads.

Is that should or shouldn't give pressure signs?

I think I need to apologize to you all for wasting your time. I just shot some Federal 140 Soft Points. The case is identical to the reloads although the primers look better. Must be a quirk with the rifle.

Should NOT be.