Primer Pictures -- Pressure Opinions?

[Josh Smith]

Hi Folks,

I went from 0.318" bullets to 0.323" bullets in my Gew88/05 Commission rifle. The 0.318" bullets were just causing problems.

Here are some pictures of primers. The brass is 7.92x57mmJS (8mm Mauser) formed from Winchester .30-06 brass. Bullets are 150 grain Hornady. Powder charge is 43.5 grains of Varget, and primers are Federal Large Rifle. Published velocity for this load is 2400fps, which is just fine. Figure it might be a bit more with the tight bore.

http://i19.photobucket.com/albums/b191/WabashShootist/Guns/reloading/primers.jpg
Two different exposures with their inverted images on the right side

http://i19.photobucket.com/albums/b191/WabashShootist/Guns/reloading/closeup.jpg
Macro uncut

The primers look like they're fine to me. Do you agree?

Data is from Hornady and the 43.5 grains Varget is their starting load. Hodgdon's starting load is 45.5 grains. Figure I'm safe using 43.5 grains as a start and 46 grains as max -- do you agree?

Also, this is effectively a squeeze bore. The initial slugging of the bore resulted in a groove measurement of a little over 0.318", but subsequent cleaning and shooting have been peeling off grime to reveal something a bit bigger. I still need to slug it again, but it may end up being 0.321" as they were playing with sizes of 0.318" to 0.321" while developing the rifle, and I have an original 1892 barrel. For now I'm assuming a groove diameter of 0.318" to be safe.

Would you have an estimate to what kind of velocity the barrel adds if it's 0.321"? I'm not trying to push the rifle's limits at all; just curious. I know there were squeeze bore barrels made for the .22LR before the advent of the rimfire .17 calibers, and they boosted by a few hundred feet per second.

Subjectively, recoil is about like a .30-30 with 150 grain load, maybe a bit less. Feels good to shoot and if I can find an accuracy node someplace under 46 grains Varget, I'll be a very happy camper.

Thanks!

Josh

[runfiverun]

those primers look fine.
i do see the imprint of the bolt face in them, but that is nothing.
,005 squeeze is quite a bit i'd [off the top of my head] say you are bumping the pressure up about 10-12k.
i would [maybe] try this with the softest thinnest jackets i culd find [speer]
if the bbl comes out at 321 i wouldn't get to worked up about the pressure. and bring the load up to what you are thinking carefully.

[leadman]

Have you measured the case from a 318" bullet case and compared it to what you are getting with the .323" bullet?

If the barrel comes out at .321" IIRC isn't that the size for the 32 Winchester Special?

[Multigunner]

Firing pin indentation looks a bit odd, have you checked the protrusion specs?

[303Guy]

I 'read' primers. I too use Federal LR primers. That looks like quite a mild to moderate load to me (but maybe not mild for a commission rifle - I don't know). Do you have any H4350 or similar (or even slower) powder to try? I would suggest you could drive a 180gr bullet to the same velocity and pressure as those Varget loads.

What I do see is a very central firing pin strike. Neat photo's.

By the way, a trick I have used to 'read' or compare pressure it to make an indent in the case near the shoulder and see how much it pushes out on firing. Changes are more pronounced than on primers. Experimenting will show how where and the dent should be made to be meaningful to you. ( A dent that never irons out is counterproductive).

[jonk]

I'd think twice about stuffing a bullet that is 5/1000" oversize diameter through an action like an 88. I've run into pressure trying to use a .311" bullet in a .308 bore well before max loads were reached.

The Gew. 88 is a solid, well made gun, but it really should be limited to 40,000 psi for a regular working pressure. While normally your load and bullet weight should be fine, you could be spiking above this with the oversized bullets.

Consider either a push through die in .321 or buying some winchester .321 bullets.

The primers look fine, but I find they don't start to flatten until around 50,000psi or up is reached.

[leadman]

The US made 8mmm .323" ammo is designed to not overpressure a .318" bore if fired in it.

You may want to buy some of this and measure the pressure ring just ahead of the web and not exceed this when loading your own.

You can call Hodgdon and ask the tech about your load. They have very good service.

[Multigunner]

I'd think twice about stuffing a bullet that is 5/1000" oversize diameter through an action like an 88. I've run into pressure trying to use a .311" bullet in a .308 bore well before max loads were reached.

The Gew. 88 is a solid, well made gun, but it really should be limited to 40,000 psi for a regular working pressure. While normally your load and bullet weight should be fine, you could be spiking above this with the oversized bullets.

Consider either a push through die in .321 or buying some winchester .321 bullets.

The primers look fine, but I find they don't start to flatten until around 50,000psi or up is reached.

The Birmingham Proof authority along with Radway Green ran a series of tests to determine the pressure increase when using .308 bullets in undersized bores. Undersized bores for long range target rifles had been in favor for some time, to compensate for the undersized bullets of much of the milspec NATO surplus ammo that had been used for NRA matches till they contracted for new production ammo as the standard issue target round for NRA sanctioned matches.

They found the major cause of increased pressures was a chamber neck cut too tight for a mixture of full size bullets and brass with relatively thick case neck walls. undersized bores also had an effect.

The NRA then made new rules on chamber and bore diameter which a rifle had to pass before use in competition.

The Gew 88 with earlier bore sizes of .318 to .321 also had chambers cut with the slightly smaller diameter neck of the 8mmJ ammo in mind.
Sometimes when converting for use with 7.92X57 ammo they simply freshened the chamber neck to a slightly larger diameter and left the bore size as it was.

When the 6.5 Remington Magnum had been out for a few years one of the Model 600 carbines was blown up when the owner handloaded his cartridges using salvaged 6.5 Carcano bullets that miked at .268 rather than the U S standard of .264. The blow out was due to a too tight chamber neck and oversized bullets.

Old built up carbon fouling in the chamber neck can exacerbate the situation.

[Me not you]

A big factor on using slightly oversize bullets and pressure is what the bullet is going into. In the picture below, the taper will swage the bullet with maybe a 10% or so increase in pressure. The step on the other hand would cause a much larger increase in pressure if the bullet is larger in diameter than the step. Enough possibly to blow up the firearm.

http://castboolits.gunloads.com/imagehosting/201464f2d06dd83936.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=3763)

[stubshaft]

The primers themselves look fine.

[Mk42gunner]

Firing pin indentation looks a bit odd, have you checked the protrusion specs?

This was my first thought as well. While the outer edges of the primers look fine, the firing pin indention does look rough, for lack of a better word.

I would make sure the tip of the firing pin is well rounded, with the proper protrusion.

The appearence could be the camera angle and lighting, too.

Robert

[303Guy]

I have this picture I took a few minutes ago and it has that same strange looking inner 'ring' as does the OP's. It's light reflection in my case.

http://i388.photobucket.com/albums/oo327/303Guy/325grW748206grXIXPP006.jpg
http://i388.photobucket.com/albums/oo327/303Guy/closeup.jpg

By the way, I find it more revealing to photograph the primer out of the case. (A trick is to place it on top of a clean transparent surface so the auto-focus sees only the primer top surface).

[Hang Fire]

When primers start looking like they are milled flush with case head face and extruded out around the firing pin area, those are signs of high pressure.

But with that said, some weaker actions can fail well before such signs occur.

[303Guy]

Like a Lee Enfield. Don't forget the edge flattening effect of primers backing out and being reseated. Mine don't do that - the cases lock up tight in the chamber against the shoulder.

[Me not you]

Take a look at the tip of your firing pin. I needed to gently stone one or two to the right profile.

[Josh Smith]

Hi Folks,

I'm sorry I've been away. The 88/05 conversion does indeed allow 0.323" bullets. They are swaged during firing as Me not you (http://castboolits.gunloads.com/showpost.php?p=1575143&postcount=9) posted.

What I did not know was how much the pressure was raised. Seems 10% is the answer... right? This is the number getting tossed around.

Now, most of my brass is Winchester but I have some Remington brass in there too. The Remington brass was stuff that was forever backing out the primers with 0.318" bullets. The Winchester didn't so I used mostly that.

Well, the Remington brass still backed out the primers -- not near as much as with the 0.318" bullets, but some with that starting load.

Also some cases came back a bit sooty.

LOW pressure even with a 0.318" squeeze bore! I was surprised.

I might bump it up a notch or two, but not much at all. Headspace is excellent, and if it doesn't stop showing low pressure signs by 45 grains, I'll just back it off to the most precise load and call it good. I can live with low pressure signs.

Thanks!

Josh

[303Guy]

Joshua, I wouldn't be expecting primers to back out on a reload. I also don't see an oversize cast boolit raising pressure much at all. I don't know how it works with grease groove boolits but with paper patched boolits I seat the boolit tight enough to not move in the neck on firing and that's without neck sizing. The necks enter the chamber with a firm push so there's no clearance there (see my primer picture above). I don't see why a GG would be any different unless it's real hard. That primer backing out is what worries me. That might explain the sooting of the cases. The cases are moving back against the bolt face while still under pressure, thus loosing the seal. Two things one can do; firstly, don't size the cases (neck only if needed), secondly and a bit controversial, lube the loaded cases - not dripping but about the same as for sizing a case. That allows the case to settle back at lower pressure so it can expand as the pressure rises and form a seal. (I did say it's controversial but it works for me and it does prolong case life to like, forever and I'm talking Lee Enfield).

[303Guy]

Have a look over on Cast Boolits for 'Reading Primers for Pressure'. Here's the link;
http://castboolits.gunloads.com/showthread.php?t=142661

I was inspired by this thread to find out more.

[Me not you]

Extremely light loads can result in backed out primers as a result of shoulder setback. The firing pin delivers a pretty good "whack" to the base of the cartridge, driving it forward. The normal build up of pressure has the base pushed back against the bolt face, and the case swells out to fit the chamber. The light loads don't do that, so the primer slides back instead. You might see less of this if you were to oil or lightly grease the case so it can slide back.