High pressures in 6PPC

K

kolar55

New member
Hi Guys.
I am new (back) to this board after a few years. I've gotten away from bench shooting and am getting back into it. Sort of. I had a 6PPC built on a Rem. XR100 action hart bbl. w/262 neck pillar bedded into the original stock, Jewel trigger, and Leu. 45x45 scope. I had some decent groups fire forming brass and figured things would be good when developing loads. Most things I have read point to N133 as the powder of choice for the PPC. With most of the claims in the 28.6gn to 29.2 and over on some behind a 68gn bullet of some kind or other. (I've tried Berger 68, Bart's Headhunter, and Bart's Ultra). At about 28.8 I am getting brass flowing into the ejector hole. Bolt lift is just a bit of resistence but it does not click at the top. Velecities at those charges in this rifle are 3400 and above. Extreme spreads of 9 or less and ovbiously SD's are 4 or there about. Primers are flat and cratered and I'm thinking this is WAY too much pressure. Accuracy seems to be erratic with fliers that I don't think I caused. The dot of that 45 horse Leupold seems to be where it should be when rifle cracks. Is my brass that has those ejector marks ruined for max accuracy or will it be ok yet. I'm a bit frustrated and somewhat dissapointed. This one is not as easy to get to shoot as my .222x35 was back in the late '80s. Help!!!
Thanks, Lonnie
 
Try H322. Start at 26.5gr. work up to ~28.0 gr. and you should find happiness again. N133 may be a great powder, but the learning curve will stress you out. Factory actions won't handle the pressures seen in the loads used in custom actions.
 
What do your loaded rounds measure over the pressure rings of the bullets? If you are seating into the rifling with the Berger 68s, what do the marks look like? Have you checked your scale lately. On the flattening, how are you setting your shoulder bump? Are your loaded rounds and chamber completely free of oil or sizing lube? If you are using a used chamber swab after cleaning that might not be the case. Too little chamber friction, and a little too much bump can show pressure signs from the case coming back to the bolt face harder than normal.
 
Boyd mentioned some stuff - one of them is likely the cause. Measure as best you can and give us the following measurements:

Neck thickness at the greatest thickness or the neck diameter of a loaded round at the widest point from the case shoulder to the mouth of the case.

Length of a fired case with the primer removed - not sized, just the primer removed.

If you have one of those devices to measure the base to shoulder, measure the case with the primer removed, write that down and then size it and remeasure. Give us both of those measurements. If you don't have such a device that's cool - there are alternate means to troubleshoot excessive headspace.

Pretty sure when we have that info we can conclude what is wrong - this is what we live for. In the meantime, STOP SHOOTING THIS RIFLE IN ITS CURRENT STATE.
 
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At this time I can't say for sure what the exact measurement of the loaded neck is but I do know a bullet will slip into a fired case. So there shouldn't be a too tight neck problem. The first firings when the gun was new would leave a smoke ring about half way down the neck-indicating they might not have enough clearance, so I took another .0002 off per side and now the smoke ring shows two dips like it should. It seemed to shoot the best with about .0015 shoulder bump. If memory serves me correctly, the rifling marks are about square. Seating depth is .006 back from jam with .002 neck tension. I always wipe the cases after sizing etc., and the chamber gets swabbed and dried after every cleaning, which is after 20 rounds max. Always after a session at the bench for sure. I have also compared the chargemaster to the balance beam to verify it as soon as it was set up. The thing that is confusing is the brass flowing into the ejector and not having the click when opening the bolt. Most all of my other rifles usually have the click before seeing the ejector mark. Flattened and cratered primers may or may not be a decent indicator of high pressure, but flowing brass would seem to me to be. I have seen worse but I am wondering if these cases will still give good accuracy or if that is what is opening things up a bit.

Yes I have tried H322 and when I reach some of the charges I see in print the pressure signs are there again. But 27.6 does shoot pretty well and I think velocities were between 3250 and 3275. Isn't that about where the PPC should be?
 
OK I'll try to get some measurements tomorrow and post them. I was told to pretty much fill the case with either 8208xbr or N133 when fireforming. So I used 8208. I did that and I thought they were way too hot at that point already. I don't remember how much that was but it was like 28.5ish I think. I have used tight necks before in my duece 35. They were fitted and didn't need sizing to seat a bullet. I never ran into this problem. I don't know the exact unprimed length but it is like .012 short or so.
Thanks Lonnie
 
As for your other question

Is my brass that has those ejector marks ruined for max accuracy or will it be ok yet.
Click to expand...

I'd say maybe. Or not ruined, but hard to manage. I had a set of cases I was shooting too hot, hammering the bolt open matches both 4 & 5 (.30 BR Unlimited at Charlotte. Wilbur was there. Couldn't quit the load, I was leading through match 3...)

Now those cases were OK safety wise, but even with FL sizing each time, & with a much lighter load, they were sticky. Brass seems to have a memory.

On the other hand, I've a few cases that had one ejector mark only that were OK for another 5 reloads...

As Wilbur said, STOP. While 28.5 grains would generally be considered the middle window with VV N-133, it obviously isn't in your setup, & you should figure out why. Many possible explanations...
 
Remember with that factory stock, it's highly unlikely you'll get groups you see posted shot from full blown BR outfit. How good was that H322 group? Was it better than any N133 groups. Also remember one or two groups is not enough to fully verify what the gun likes. Shoot in different temps and humidity. You'll most likely find N133 is "finicky" , very finicky. Are you using Lapua brass? Sako? Accuracy rules in benchrest, once you get a load that shot tiny holes consistently and safely, why be concerned about bullet speed?
 
That is a bit confusing - brass flow into the ejector hole and no click. Have the cases been annealed?

Try to cook up those measurements....your assumptions are sound but nothing like knowing.
 
Lapua brass that was prepped by Ron Hoehn. And yes I don't really care about velocities but use those numbers to kinda double check myself and my loads etc. And yea Wilbur, the ejector mark without the click is really bugging me. I have always had the click before the mark. The bolt opens and feels about right but when I look at the case heads, the mark is there. Given that this is my first PPC with Lapua brass, I'm just not sure this is right. I'll try to get some measurements today. I've pretty much been over everything a couple times, but it doesn't hurt to go through all the steps again. It's easy to overlook something.

Thanks Lonnie
 
Well I have a bunch of measurements and they all appear to be about right to me. Also checked the Chargemaster and it is dead nuts to maybe a tenth under-weighing a known weight multiple times. Many thanks to those that have responded to this thread. I really didn't expect to get so much help on this. Here goes;
Trim length=1.488-1.490
Neck wall thickness=.0077-0078
Loaded neck dia.=.2593-.2594
Bullet dia.=.2435 on the pressure ring
Bullet runout= .0016 and under
Comparator lengths vary by about .0015
Shoulder length of a fired case using a Sinclair bump gauge=1.085
Sized cases are 1.0835 on same gauge
Neck bushing is .257
Loaded length is about .006 into the lands
 
For N133 use the .257 bushing..also try a .256 if you have.
For H322 use a .259 bushing
Exactly what are your intentions with this build?........competition, varmints, or just bench shooting for fun?
 
I guess I'm not seeing a discrepency here... ??? ..... 3400 is smoking right along considering you're running a Rem action with it's honking ejector hole. I've got several Remingtons set up similarly and they simply won't accept high pressure. IMO you can win just fine running at 3250 and that Rem will hannle that like a boss.

Plenty matches have been won at 3250, even recently. And for 100-200 I can't see a mathematical advantage (I know, I know, "math lies") in shooting faster. "Wind drift" certainly isn't affected. You'll like the 6PPC over the 222 case.


BTW as far as "no click" the chamber's probably bigger than the current fad....... Guns don't hafta' click :)

Mine don't


ever



al
 
Ya know I am really starting to think that what I'm seeing is in fact signs of too high pressure and just need to back down. I think you are right that this action just won't handle the powder like a custom job. With all the info I posted above, everything looks to be in order to me too. So with that in mind going back and starting over down lower sounds like the right thing to do. I was thinking something was wrong that everything I read was pointing to those higher powder charges and they are just too hot for this setup. Ahh experience wins again. Thank you to all. Lonnie
 
Looking at those measurements, judging the "lingo", and that the brass flowing into the ejector hole turned into a "mark".... I agree ...too much gunpowder. The only other thing to check for is an extreme carbon buildup in the chamber effectively reducing the allowable case length.
 
I might add one more thing, do you what chamber you have? I had a custom actioned 6ppc(.262Nk) some years back that was a very small chamber and it would not take a hot load and cratered primers so bad that they would be stuck in the fireing pin hole...yea i know it sounds hard to belive but you could remove the bolt and the case was stuck to the bolt..had to pull it off..but it never blew a primer..but cratered them bad..i monkeyed with it for awhile, it was built by one of the very best gunsmith/shooter's that there is and was a beautifull rifle..someone was interested in it, i told them all the problem's i had with it..so i sold it.
it could be possible that you just wont be happy or satified with the chambering you have, you could have it set back and rechamber also have your fireing pin bushed down.
and you could live with the rem action..just a thought..
 
I revisited the powder charge thing yesterday and today. I started off with 27.5, 27.8, and 28.1 N133. Bolt lift was smooth and not difficult. Groups were from .287 down to .186. All 3 shot groups. Sd's were all in the single digits. Today it was about 10 degrees colder, cloudy with gusty winds. I went 27.8,28.1, and 28.4 to try to find what I would call top pressure. These all shot pretty wellwith .275 as the high and I missed the last shot on the last group making it a .217. I knew it before sliding the rifle back forward. It probably would have been a very small zero. Again bolt lift was good. The last charge was a bit stiffer so I think 28.4 is a good place to stop. So with all that said, I think alinwa and Wilbur are right-this thing just will not handle the pressure. BTW 28.4 was just short of 3300. Many thanks to everyone for setting me straight on this.
Lonnie
 
I think what you'll find Al(inwa) telling you is that you are getting pretty high pressure, you're just able to do it with a lower powder charge. Your original post listed what, 3,400 fps? Pretty high velocity, hence likely pretty high pressure.

Why, no one knows. Could be a number of reasons. But the conclusion isn't that you're rifle "can't handle fairly high pressure," because it seems to be doing so. The conclusion is, that using the complete system, you're getting higher pressure than most with a particular powder charge.

Myself, I'd let it go at that & not worry about it, as long as the velocity & group size stays consistent at the "lower" charge. I suppose if you sell the rifle with that barrel still on, you should mention it. Or, you could shoot out the barrel trying to find out "why?"...

Edit: As always, I'm giving a perspective. Anytime you think safety is an issue, you should stop & get at the problem. I'm simply saying that it doesn't seem to be a safety issue involved with the lower charge. Which, of course, is how things ought to be.
 
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Charles, I agree, and I think you are right in the conclusion of getting there with less powder. This is my first PPC and didn't really know what to expect. All I could do was consider what I was reading. I have seen powder charges as high almost 30 gn of n133 and velocities of over 3400. So when this rifle is coming up with a different set of results, I was concerned I was doing something wrong or there was something wrong with whole package. I've been shooting a long time and should have trusted my instincts a little better. Now that I think about it I have run into this same type of thing with other cartridges too.

Another question, What is the deal with the recall on the Berger column bullets? I was measuring some of those yesterday with a comparator and they varied a quite a bit from base to ogive-way more that 68 Bergers I have and the Bart's Ultras. I wanted to try some of them today. do you think they will be a problem?
Thanks Lonnie
 
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