PP for a 7mm-08 is a .270 bullet a good start ?

[greywuuf]

Hey guys I just picked up a REALLY cute Ruger Youth rifle in 7mm-08. it is the laminated stock and looks and acts almost like one of the GS carbines. I have been wanting to PP for some time now and was thinking that Maybe a .277 mold ( intended for a .270 or 6.8) might make a lazy mans start ( and cheaper than a custom PP mold) way to go about this. Any recommendations or experiences to share.. either about my Idea or the 7mm-08 in general?

[greywuuf]

Never mind, brain fart, I knew this. I will just use the 7mm mold I have and size that after patching. I would still like to hear of any successes with PP in the 7mm-08

[pdawg_shooter]

Depends...what are you bore and groove diameters?

[greywuuf]

That is a good question, and one I plan to answer this weekend, if I can find some dead soft lead and a decent rod to slug the barrel, hoping to get an impact cast of the throat as well.

[greywuuf]

ok had some trouble but got a partial impact cast of the throat but dont like what I am seeing. Is it common for the 7mm-08 or Rugers to have this short of a throat ? ( crappy picture I will try for a better cast and a better picture)
83232

[HABCAN]

Well, you have a nice cast of the freebore part.......now make one about 1/2" longer out to the left as shown in your pic and see where the rifling starts. Then you'll know what you have for a 'throat'.

[greywuuf]

rifling shows in that picture, there aint no 1/2" left actually the rifling starts right at the bright ring at the midpoint of that.

[greywuuf]

ok just got a clean slug through the bore and it appears as though the rifling is fairly shallow, Bore measures .278 and groove is .284, looks like a mold for .277 might actually work out ok , would still have to size them, so not sure what I should do, the only 7mm mold I have throws .288.

[geargnasher]

My RCBS .270-150 mould drops .279 boolits, which would work great for you, but my 7mm-08 barrel had a bore around .280" from wear.

Your accuracy and function challenges with PP in your rifle will likely be with the .317" chamber neck. Make brass out of .270 and neck turn to .016" thick. Size your boolits to .279" and patch with two wraps of 9lb onionskin paper or maybe even cigarette paper, twist the tail, and shoot them with something like H414/WW760. Worked for me, anyway. As an aside, I quickly found that with properly fitted brass, 2625 fps was easily attainable with reasonable accuracy using standard lubed, checked boolits, so I quit patching.

Gear

[greywuuf]

Gear you are the second person that has told me to use long brass .....not that I doubt you but this picture of new once fired factory brass, compared to a chamber casting just does not convince me I will gain much. What am I missing?
83254

[geargnasher]

You pretty much missed most of it, and more particularly the reasons why. Reread my post above. I didn't mention it because of "long", although being able to close the gap at the end of the chamber is a plus.

Gear

[greywuuf]

On re reading you mentioned a dimension for the neck. I took that to be a length not a diameter (as I was asking about short throats and was just think length I guess). So you are saying that the biggest issue is excessive neck clearance and that I should form brass to overcome that? I have not tried it yet but I do have a lot of LC ".308" brass that I can only assume will provide a bit thicker neck when sized to 7mm. Soon as my dies arrive I will take some measurements and start experimenting.

[greywuuf]

Oddly enough I just measured the "fusion" brand ammo brass that I fired from this rifle, outside of neck..316, neck thickness .016, and the as cast bullets I just made (.288) will not slip into a fired case, I don't have any sizing dies (bullets or brass) for this yet, so still more to do, but it might end up shooting these cast bullets quite well just lubed and gc'd as Gear said.

[geargnasher]

You got it! Chamber neck is probably around .317" average with some taper, .316" OD fired brass is typical after springback. I'm very surprised your necks are that thick, most run .312-.3135" nominal with some considerable thick spots. Knocking back .270 brass gets you a little more case volume (in the head area), ability to trim to fit the chamber length minus a few thousandths for safety, and to get necks thick enough to force the boolits to get t a straight start. One more thing, make sure the other end of the case doesn't wiggle in the chamber or the snug neck fit is meaningless. Please ask questions if any of this fitting business is muddy, it is one of the keys to accuracy.

.308" brass doesn't gain much thickness being squeezed to 7mm, at least in my experience, but by "much" I mean not more than a thousandth which isn't nearly enough for what I needed.

You've already done the pound cast of the chamber neck and throat, that will be your guide for fit. Max boolit diameter is throat entrance diameter, so figure that (maybe .285"?? Check and see), try to get your loaded neck diameter with a throat-entrance-sized boolit to fit the chamber neck minus a half-thousandth diameter. With .285" boolits and .016" necks and a .317" chamber neck (just for example, confirm by checking your pound cast) you would end up with a theoretical zero neck clearance. With that lot of Fusion brass you may need to just "clean up" the high spots on the necks with an outside neck turner to achieve perfection, but that depends on the throat diameter and how much your boolits compress when seated. The Lee 7mm boolit shot well for me, and has for at least one other person at very high velocity/rpm if you can get enough of it up into the throat (gas check location proved critical for me, I ended up getting best accuracy with it "just" barely still in the neck). Use water-quenched 50/50 wheel weights/pure with a pinch of tin, and starting jacketed load data for the slower powders (4350, H414, 4831, etc.).

I'm a big fan of paper jackets for the modern high-powered calibers, but this one worked well enough for me using traditional greast-groove boolits and gas checks that I quit bothering with wrapping them. Your results may vary, but I wanted to share my experiences here in case you had any preconceived notions about the limits of grease-groove cast boolits at 200,000 RPM.

Gear

[greywuuf]

Thanks Gear, I knew I was just being thick. I have a lot of same lot number once fired mil surp, that I am going to run through this Hornady die (borrowed one today) so that I can take some.measurements and see what it comes out as. Wish I had some gas checks. I would give these fresh cast bullets a shot.

It's not like I have not played with turned necks before I built a 22-256 win mag wildcat with a tight neck, I got it down to the point where I do not size my brass anymore.... The necks just open far enough to release, but not far enough to exceed the plastic limit. It's nice if you can get everything just right. Those necks got significantly thicker (.357 necked to .22) so I had plenty to turn.

[geargnasher]

There ya go! Just apply the same principles. I didn't need to resize these, either, like you say if you limit the movement by a tight fit, they stay within the elastic range.

Gear

[MBTcustom]

Boy, you actually got a rifle that was made close to being right!
Miracles do happen.
Wish there were more like that one out there.

[greywuuf]

Pretty sure you make all of your "close to right" goodsteel.

[MBTcustom]

And just to think: if the gun industry would have only surrendered me two or three really excellent shooting rifles, I never would have become a gunsmith. I always get stuck with the worst dogs in history.
My 336 shoots 4" groups
I had a M70 that would shoot 4" groups after carefully working up reduced loads with copper jacketed rounds.
I bought a #4MK1 Lee Enfield that had a groove diameter of .320
I'm a diseased rifle magnet I tell ya! Like Johnny Cash said, I had to "get tough or die" LOL!

[geargnasher]

Actually, Tim, his rifle is on-spec, which is usually terrible for cast boolits, but his BRASS is way above average thickness.

Gear

[greywuuf]

Heh, "my brass is above average"
I will go with that.

[Harter66]

Actually I've a smaller 7mm w/bore groove diminsions that mirror yours and my RCBS 27-130 at 278 is near perfect in it . FWIW the 7x6.8 REM shot identical groups w/120 flat base soft point Seirra and the 27-130 at 132 gr w/the patched 132s going 20fps faster on the same 22.0 gr of RL 10x. While this is 1 bbl and 1 example the 270 boolit works well in it.

No Tim I've not gotten back to dial it in yet but very soon I will be back on it. I do have another ''plan''in my little head.

[Good Cheer]

No, haven't tried paper in the 7-08 yet. But I'll get there.
As concerns the 7-08 in general, it's great for cast. Had a 788 with the 18" barrel in 1981 that I used as a test bed to develop data for a cast boolit wildcat. The old Lyman 280473 with DoAll Tool Saver for lube, bumping up with pressure, worked great in it. The inside of the barrel would look like it was galvanized and it still shot into 2" at 100 yards. Later on it had the chamber neck lengthened to use full length sized 30-06 cases with the old design long contact length RCBS 168 grainer. The loaded cartridge looked like a beer bottle so it got dubbed the 28 Long Neck. After all the data was put together it got rebarreled. Still have the 280473 and the discontinued Lee 270 mold. So, yeah, I oughta get with the program and roll'em!