High pressure signs where I shouldn't have any, Please help.

[jeffman3]

OK...... This has me stumped.

So I'm turning to the smartest group of re-loaders I know. I am shooting a Stevens 200, 25-06. Load: R-P cases, WLR primers, Nosler BT 100 gr, H-4895 powder, bottom book load 40.0 gr, Seating depth .020 off hard land contact. This rifle has a short throat. (Sierra 90 gr HPBT loaded to book length are showing land contact.)

I am showing flattened primers with the bottom book loading listed above.

My thought was short throat, coupled with a possible tight chamber. I need some help understanding whats going on, and what to do about it. Any ideas?

[thomae]

Just a thought. Is your loaded ammo truly clean or might you have some lube or oil residue on your brass?

As you sugges, it could also be a sizing issue.

[Eric in NC]

Very light loads will show flat primers at times. Does it do it with factory ammo?

Clean oil out of chamber, clean brass, make sure there isn't anything in your chamber or throat, double check powder (make sure it is 4895) double check weight (pull down one of your loads and weight it).

My bet though is light load in slightly long chamber.

[keeki]

what is your COL? if your COL is shorter than book then your powder is gonna be less than book. Bullet takes up case capacity.

[AKShooter]

Obviously the above but here's some food for thought. There is a theory that light loads are more dangerous than heavy loads. If you are familiar with gasoline engines think predetonation or ping. The idea basically goes that the burn is ignited on both ends and the pressure waves meet in the middle and develops much higher pressures than normally seen. The theory in cartridges is that the spark starts to burn but jumps to the front of the case via the air gap left due to the powder laying in the bottom of the case. Search reduced loads in .454 casuall with h110.

[Mallard57]

Hi,
I have a Savage 16 in a .308 Winchester that was doing the same thing, it didn't shoot too well either. I got disgusted and bought a new barrel. Just before I swapped the barrels out I decided to check the headspace on the factory barrel and it was .012 of an inch. It flattened primers on everything.
Jeff

[jeffman3]

Thanks guys. This rifle is a candidate for a re barrel job anyway, but it drives me nuts when I can't figure out why I have unexpected results.

I of course rechecked components, and load parameters first. I may try neck sized cases and see if that helps? Fire-formed, should be closer to a fit if this is a head space issue. I'll clean and dry the barrel/chamber, and see where this goes. I wish I had a set of gauges to check the head space.

I am tempted to buy some ammo and see what results I get with that, but to be honest about it, I haven't bought rifle ammo in decades.

[keeki]

just use a resized case to check headspace.

[bigedp51]

keeki

just use a resized case to check headspace

A full length resized case is designed to be at least .002 shorter than minimum headspace, How are you going to use a cartridge case to check headspace when its too short.

http://i122.photobucket.com/albums/o254/bigedp51/IMGP7241.jpg

Your telling us to use a full length resized case to set headspace that's at least .002 shorter or even more than minimum headspace or GO. Where do you people come up with these ideas, I have brand new cases that are .009 under minimum headspace and they have been full length resized.

http://i122.photobucket.com/albums/o254/bigedp51/IMGP5163.jpg

[keeki]

I guess if your gonna load that headspace gauge and shoot it then you may not want to use a resized brass to set headspace. But, if your gonna use that resized brass to make your ammo then it should work just fine. When you tighten the barrel nut up youll gain .002 in headspace from the nut pushing against the action locking it in place. And always remember that tight headspace is much better than loose headspace.


And use a brass thats been shot and resized through the dies that you intend to use to make the loads for that gun. New brass varies in size too much to set headspace by

[jeffman3]

Thanks for the help guys! ;D

I am thinking more and more that this is a combination of problems.

I Know I have a short throat. ( 90 grain SIE HPBT loaded to book length are showing moderate to hard contact with the lands. [not enough to hold the bullet in the barrel, just very clear and obvious land marks]) The flattened primers, I am believing are a result of long head space.

My plan is to load some ammo (bottom book) 2 rounds at book length with land contact, and two rounds .020 under book length. If the rounds loaded with land contact show less flattening then the loads .020 off then I am definitely dealing with a barrel that has long head space, and a short throat.

The Physics of internal ballistics can be tricky, but If I am correct this test will show me what I am dealing with. It won't show the extent of the head space misalignment, but it should tell me if that is the problem. Trying to sort out two issues in the same barrel has me scratching my head and pouring through my reloading library, for solutions.

If this proves out, resetting the barrel to correct head space will make the short throat issue even worse. My thinking is a new barrel is in order, if this proves the direction I am thinking it will.

Your opinions are always welcome.

[keeki]

I have a 25-06 110fp that has a short throat and it is scary accurate. just gotta stay away from those book Max loads. The combination of being close to the lands and having the bullet seated deep causes pressure quickly.

[parkj5]

I have a ruger 25-06 doing the same thing....