Chamber/sizer and brass question

[Phys86]

I have a few questions on my reamers, design, and experience with my brass.

Here are the prints





Experience shooting this chamber
- FL resize die is cut from a PTG blank. Not hardened.
- I shoot Peterson 284w brass, 55.5gr h5350, cci 200, 185 juggernauts about 0.020 off lands (bearing surface well ahead of donut area)
- mv about 2825fps, 23" barrel
- started seeing light ejector marks around 56.5 initially when doing pressure ladder, now sometimes I'll occasionally see one at 55.5gr
- full case is around 57.5-58gr
- Peterson brass measures 0.499 just in front of ejector ring virgin. Just under 0.500 for 11x fired
- measures 0.503 after firing at the bright line/ring in the pictures above extractor groove
- measures 0.502 for 3x fired brass at that same line/ring, 0.502+ for some 11x fired




Questions:

- is the 0.200 dim always actually at 0.200 from the bolt face/cartridge base? My 11x fired cases measure about 0.503 at about 0.275 from cartridge base.
- Is it normal to have that "bulge"/ring around the bottom where the die quits sizing or can't size?
- do I need a small base die or do I just need to have a better sizing die made? It seems with my sizing reamer it should size that bulge/range back down
- it seems like I might sometimes be getting a slightly stiff bolt lift with some of the 11x fired. Does that mean something is causing overpressure or just that I need to size that bulge down further?
- should the 0.200 dim be larger than 0.502 or is it more likely that my sizing die is swelling?


Final notes are that it shoots really well. Consistently better than 0.75moa, which is good for me. This load didn't seem to be over pressure at all when I developed it, so the occasional ejector marks and stiff bolt lift I'll now occasionally see with the 11x brass are a bit baffling. It's a Tikka action, which is cock on lift so it's kinda hard to tell when it's a little stuff. It's more noticeable for definite over pressure loads.

 

[fkimble@charter.net]

There is no bulge around the .200 line. How far are you pushing back the should each time? With 11 firings it's probably ok headspace wise. Maybe try another thou or two, to push the case into the taper a little more. How is case length? If a couple get too long that could increase the pressure. What is your loaded neck diameter? A thick neck here and there could also increase pressure.

On another note: that case looks terrible! Never seen so many rings on a case and the lengthwise lines also. Does your sizer create the lines/rings or does the chamber?

Frank

 

[FeMan]

What do your sized cases measure at the 0.200 line?

 

[Phys86]

There is no bulge around the .200 line. How far are you pushing back the should each time? With 11 firings it's probably ok headspace wise. Maybe try another thou or two, to push the case into the taper a little more. How is case length? If a couple get too long that could increase the pressure. What is your loaded neck diameter? A thick neck here and there could also increase pressure.

On another note: that case looks terrible! Never seen so many rings on a case and the lengthwise lines also. Does your sizer create the lines/rings or does the chamber?

Frank

What I am calling a bulge, is the diameter of my case where the die obviously stops contacting it during sizing. It measures 0.503 after firing.

The 0.200 line is between the edge of the extractor groove and where bulge/ring is. It measures around 0.4995 on most cases, which is why I am calling that 0.503 area a bulge.

Case length is fine. I always trim when I get more than a couple thousands above 2.160 and the chamber is as shown above. I have checked with a borescope when I hit 2.160 case length to make sure I'm not hitting the end of the chamber, and I'm good there. I clean it every 50 or so rounds and don't have any significant carbon buildup, so the occasional pressure spike should not be from that. Loaded neck diameter is 0.3375, and never more than 0.338 on a slightly thicker one. Fired neck diameter is 0.342.

I'm bumping the shoulders back. 0.002 -0.003. I can't push the case any further into the die without oversizing.

I anneal my case is with an induction annealer every firing. Those circumferential stripes you see all the way up and down the case are from the sizing die. I had a straight 30-284 that I used Redding dies for and it had the same circumferential rings all the way up and down the case body. I think the longitudinal lines are also from the die, although some of it is just from feeding the cases into the chamber from the magazine quickly.

@FeMan , If we are considering the 0.200 line to be the edge of the extractor groove, then after sizing it measures 0.4995 -ish on most cases. If you're asking about the true 0.200 line, where it is that distance from the base of the case, then it's likely slightly larger than that because of the larger ring/bulge just ahead of there measuring 0.502 after sizing.

 

[FeMan]

Ok, now I think I understand. Not enough coffee yet for me!

If your cartridge base below the 0.200 line measures 0.503", your brass may be trashed. It should measure 0.500 or less. If you have any virgin Peterson brass, what does that measure?

If your case head is expanding, you are over-pressuring the brass. The 284 has a rebated rim (0.473 bolt face and 0.500 body diameter) so there is less surface area to absorb the pressure. The case head therefore experiences higher pressures (about 12% higher) than it would otherwise see. The solid case head should not grow in any appreciable amount. It seems like it has increased by 0.003" or more and if so, that's a problem.

 

[Phys86]

Ok, now I think I understand. Not enough coffee yet for me!

If your cartridge base below the 0.200 line measures 0.503", your brass may be trashed. It should measure 0.500 or less. If you have any virgin Peterson brass, what does that measure?

If your case head is expanding, you are over-pressuring the brass. The 284 has a rebated rim (0.473 bolt face and 0.500 body diameter) so there is less surface area to absorb the pressure. The case head therefore experiences higher pressures (about 12% higher) than it would otherwise see. The solid case head should not grow in any appreciable amount. It seems like it has increased by 0.003" or more and if so, that's a problem.

Perhaps a picture would help

I have not considered it to be highly overpressure because my primer pockets are still plenty tight at 11x firings.

 

[Tesoro]

On note about the fugly brass. I had a couple of chambers done and the fellow didnt polish them sufficiently and my brass looked identical from the annular ring chamber imprints. And then I had the same longitudinal scratches which were made by leaving the entrance to the chamber sharp, instead of bevelling and polishing. I spun the barrels off and had my regular smith fix them up for me. And I tossed the brass! When you size the brass, even if polished, it will bring out those scars to the surface.

 

[Tesoro]

and ps: as you have yourself a customized chamber and experimenting with loads then spend 10 bucks on one of these. Measures same spot easier and it is faster to do ie 5 cases out of same firing to check averages.

Cartridge & Bullet Measuring Tools - .200 Line Tools - PMA Tool

www.pmatool.com

 

[gunsandgunsmithing]

He said his sizer die was not hardened. That's why the brass is ugly. You do need a better die. Your resize reamer is about right for your chamber reamer, size wise. It's normal for the hard, thick brass at the base end to spring back a lot, like yours. It gets pounded on and all brass will eventually do this. How long before it does, depends a lot on how hot you're loading. You mentioned other pressure signs indicative of the load being at the top end so you may be at or very near the end in terms of good brass life.

With your shown reamer sizes, I'd expect to see about .002 or so of sizing after spring back at the top and about .0006-.001 at the .200 lin for a while but it will keep getting bigger with every firing and sizing, by a little. If you're not using a good micrometer that is capable of reliably reading in tenths, you should be. Calipers just are not intended to measure anything under a thou or so reliably, even the best ones. Resolution has nothing to do with that. And even with a good mic, it takes some practice to get accurate and repeatable measurements to the tenth. So, if not already, you really need to be using a good mic here.

Not sure with a 30-284 but most 284 based cases have a bit of this issue when pushed hard.

We really need a good measurement at the .200 line, in tenths to say much more than this, conclusively. If you're getting clickers though, that pretty much answers the whole question...you need new brass. Your .004 of sizing before spring back is fairly aggressive but should work well. I know brass is scarce and expensive but Ii don't see anything other than the scratches that I'd blame on the die. Not familiar enough with Peterson brass to have an opinion but you might get better life with Lapua...or not. I would try it and see because as I see it, with the brass you're using you have two choices...Back the load down or break open a new batch of brass. Actually, new brass either way. IME, you won't get rid of clickers for very long, regardless of what else you do. You might get a couple more firings out of it with a more aggressive sizer or polishing the chamber a tad but I'd just bite the bullet and get new brass and a new die, but same dimensions. You might try having that die nitrided, as it will give a hard surface, and do a much better job. I don't think you'll regret addressing the die not being hardened.

 

[Phys86]

@gunsandgunsmithing , Thanks! I'll look for a micrometer and look into die nitriding. I'd planned to do that, but didn't get it done. I also plan to do some shooting with new brass dropping my charge by either 0.5 or 1.0gr to see how the case handles it. I'm also going to try out some Lapua.

For the current die, nitriding it will do nothing for sizing the web/base are further, correct? It will only help with the ugliness of the brass and make the sizing operation smoother?

If I have a new/better die cut, what die mfg would do this work for me since I own the resize reamer? Affordable is better, since I don't compete.

 

[Tesoro]

Thanks! I'll look for a micrometer and look into die nitriding. I'd planned to do that, but didn't get it done. I also plan to do some shooting with new brass dropping my charge by either 0.5 or 1.0gr to see how the case handles it. I'm also going to try out some Lapua.

just for the heck it it clean you chamber and poke in your borescope. Look for annular rings on the last half of the chamber, where it is harder to polish and matches your case marks. Also look at the chamber edge and se if it is sharp or has been lightly bevelled to not make scrape marks on insertion of a round.

 

[Phys86]

just for the heck it it clean you chamber and poke in your borescope. Look for annular rings on the last half of the chamber, where it is harder to polish and matches your case marks. Also look at the chamber edge and se if it is sharp or has been lightly bevelled to not make scrape marks on insertion of a round.

The barrel breech is well beveled. When I've inspected it before with my scope, I haven't found anything that looks like it would cause the annular rings, but I'll check it again as I wasn't inspecting specifically for that.

 

[Tesoro]

The barrel breech is well beveled. When I've inspected it before with my scope, I haven't found anything that looks like it would cause the annular rings, but I'll check it again as I wasn't inspecting specifically for that.

What happened with me is the machining ring imprints were not that obvious on extraction. Then I cleaned up my cases on a drill to make them pretty and the marks disappeared. But after they came out of the f/l die they re-appeared and looked like yours do. But after I took off my barrel and had it polished up then I didnt get those nasty rings marks after sizing anymore. The f/l sizing process make them re-appear! That was my situation and maybe not yours but wise to check that off your list. And get better dies anyhow!

 

[RGRobinett]

Saw a case in half [length-wise] and you'll see that your "bulge" is at the junction of the solid case-head and the body wall - so long as the case-head expansion remains <0.001", you are not achieving excessive pressure and may well be able to live with the slightly more difficult extraction.

Over-all, Mike's post (#9) is sound advice. RG

 

[Phys86]

I have not had any cases where the edge of the extractor groove is larger than 0.001 yet. But yes, I do need to get a 0.200 tool from pma and a mic to measure this more accurately.

I've been monitoring the thinning of that portion of the case with a sharp pin to feel inside. My 11x cases have a noticeably more prominent dip in that area when running the pin in towards the base compared to the 3x cases. It seems I have to trim more often than I expected, but I'm keeping an eye out for head separation to start.

My shoulder is 0.486 fired and sized to 0.4815. I think that might contribute to needing to trim every 2-3 reloads.

I will first try some Lapua brass. I'll see where pressure signs start to show up in comparison to Peterson, try to use a load that might be ballpark same pressure (I assume if the case H20 vol is same as this brass, same charge should provide roughly same pressure), and I'll monitor case head/web expansion.

Having a new sizing die made may come later because funds are tight. However, I may use a bore mop and polishing compound on my current die to see if I can polish the interior and make the sizing easier.

Thanks for the advice everyone. I appreciate it.

 

[KMart]

On another note: that case looks terrible! Never seen so many rings on a case and the lengthwise lines also. Does your sizer create the lines/rings or does the chamber?

Frank

Maybe it is just me, but i have only owned 2-3 Redding F/L sizing dies. Every one gave me that "look" after sizing. I have culled all of them.

 

[Phys86]

I have some Lapua on the way to test out. I also want to have another sizing die cut and nitrided. My die is just barely useable for a few reasons.

Does anyone have any suggestions on who the best would be to have a die cut with my reamer and can also send it for nitriding? I haven't called around yet to see if any of the big guys would cut it with my reamer, like whidden