Today I went out to test a new load for my wildcat 33 G&A. Load was a healthy charge of R25 behind the 250gr Nosler bullet. I loaded up several at one seating dept, then several more seated out a bit closer to the lands.
Once at the range I fired the first three shot group, made notes as to the size of it and noted there was no indication of high pressure on either bolt lift or cases. In fact, I noted it seemed moderate at most.
I then noticed these were the longer length rounds so thought oh well, now for the others and began again. To my surprise the first one required me to pound the bolt open with my palm! Second one did as well! Why?
These had identical charges of powder, primers, etc and were loaded so as to give them more "jump" than the first series. I would have thought if either one showed high pressure it would have been the longer ones! Does anyone have any ideas about what went on here!

John
The only thing I can think of is the deeper you seat the bullet which lowers case capacity which raises boiler pressure.
Anybody got a formulae for this.

Rich.

If I may venture a guess, I'd say that the increased pressure was caused by the decreased airspace inside the case. Less space = more pressure upon ignition. Also, this might have happened with a combination of short rounds, thick necks, and (maybe)magnum primers. I've been using standard primers in my .300 Win Mag with great success recently. Also, reaming the ID might help drop pressures a bit, especially if you have found a really accurate load you want to keep.

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Happiness is a 200 yard bughole.

Perhaps fouling? First three thru a clean bore, then with the bore fouled, pressures rise?
Just brainstorming...
Tom

I'm baffled also, I've worked up compressed loads but never had pressure spikes from seating deeper in the case if the initial charge was okay. I would suggest backing off a few grains and work up again keeping your seating depth the same. A compressed load is generally very consistent in pressure hence accurate also regardless of the increased bullet jump to the lands. As with all aspects of reloading though nothing is written in stone. Try again and let us know of your results.

Good shooting,
sure-shot

I have searched and checked and really found nothing to attribute this to so have just went through all of the cases with my neck reamer on the possibility there were a few bit thick. Will give them another test and let you all know the results.
Thanks for the suggestions!

John S -- I shoot a .340 WBY and with max loads the RL-25 powder has to be compressed too much. I don't know how your 33G&A compares to my rifle but RL-19 and RL-22 are my favourite powders, you might try them and avoid the problem you mentioned. One thing for sure, that load is too hot, so you are going to have to try something else. Just a thought. Good shooting.

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phurley-
I have used a lot of R22 and 7828 in this cartridge, they do work well but since I have some R25 I thought I might give it a go. With R22 I seem to be running into pressure before top velocity is attained, not so with 7828. This R25 is supposedly slower than 7828 so figured it should work?
Also, after inspecting the cases I'm convinced it was neck wall thickness. The primers weren't flat, there are no marks on the cases heads to indicate brass flow into the ejector slot, etc.

[This message has been edited by John S (edited 10-29-2001).]

How long is long to you ? I mean how was the seating depth re. neck friction.

With a hot load, increased friction between bullet and neck may increase pressure as this extends pressure development within the case.
Friction force is minute compared to the max pressure of the load, but it starts small as nearly everything in this world so that friction has a certain retarding effect (we are dealing with tiny bits of time) which makes a higher proportion of the increasing pressure happen before the bullet leaves the case = considerable expansion happens.

This effect, increase of resistance to rising pressure, is provided by the shoulder of bottleneck cases as well.

Here we go again!
Tried things again this morning, this time I switched over to 7828 and used cases that I just neck reamed. I also measured the necks with bullets seated and after firing, there is 6/1000" difference, so I think I'm fine there. Bullets were seated 40/1000" off the lands in one batch, 60/1000" off in the other. Shot the shorter batch first, no pressure signs and a nice 1" grouping as a result. Proceeded to fire the longer batch and on the first shot I'm pounding the bolt back with my hand, just like last time!
I've used these charges before with the regular style Nosler partitions and Fail safes and have never ran into this. I'm begining to think this is bullet related!

John
Now I'm baffled in your first post the longer length were okay but in your last post the longer ones have pressure?

Rich

Now I'm confused (so what else is new?). In your first post you stated that you shot the long cartridges first then the shorter ones showed the pressure signs which is counter to what I would expect. This time things went as I would normally have predicted in that the cartridges with less jump showed the pressure signs (heavy bolt lift). Which is it?
By the way, by the time I encounter difficult bolt opening I would expect to see some other pressure signs. Regards, Bill.

So, now you guys are confused and baffled as well! Join the crowd!
In the first test I did shoot the longer batch first. In the second I reversed the order and shot the shorter ones. In the end, after three shots of one batch it happened on shot #4, so that tells me something is wrong! It has to be either powder fouling and/or something with these bullets is haywire and causing something else to happen within the leade.

John,
I think you are on the right track. Something is loading up after three shots and the next three are showing pressure signs, regardless of O.L. How does the throat look? Is it at all rough? I have seen where too soft bullets can load up a throat very quickly and velocities can spike in the same string. Running a dry patch through will often help to locate rough areas even before discoloration takes place. Interesting.

A possibility...

In the shorter rounds, the primer created enough pressure to dislodge the bullet from the case and move it forward, slightly into the lands. Then, the powder developed enough pressure to begin moving the bullet, which was stuck in the lands. This would all happen rather instantly, but it has caused blowups before.

If you're not using a magnum primer, do so. If you are, then (or in addition to the mag primer) put a good crimp on the bullets at the case mouth.

IF this is what's happening, pressures can go over 80,000 psi and give you a nasty surprise.

Please be careful.

redleg

After considering all of my actions and options, I loaded several rounds at the shorter COL, reduced the charge by a couple of grains and had no more extraction problems. BTW, the barrel hadn't been cleaned since the last session,to eliminate the "clean barrel syndrome"!
This still did not answer the question of why things went south after a three round string, but cutting back on the powder didn't hurt.

John,

As you know I mentioned pressure spike with foulded bores and reload powders. This an be noticeable with soft brass, which RWS brass is. In other words with soft brass, your accurate load is closer to causing problems than if brass was hard.

However, I agree with Bill Leeper that hard extraction should be showing other pressure signs UNLESSthe rifle has some mechanical problem with extraction.

Mike

If you have access to QuickLoad try this. Take the load you are using...powder, powder charge, primer, etc. and plug in the two different OALs...you will find the shorter one will give the higher pressure. The effective decrease in case capacity is the culprit. I ran into the same thing awhile back with my .375 and RL15...seating the bullet out a little further made all the difference.

JohnS,
DB hit the nail on the head, proof of this factor is delt with when one has a very long throated rife, in that he can load beyond book max as much as 5 to 8 grains in some cases simply because he has more powder space, furthermore he will get more velocity....Another prime example is that the exact circumstances take place when one deals with in an improved cartridge/chamber, more powder space, and increased velocity at the same pressure level as prior to improving.....

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com