.458 SOCOM anyone?

L1A1Rocker

Active Member
There ARE ways to lighten a barrel. . .

sidebysidebarrels.jpg
 

Ian

Notorious member
I'll be over in a couple of days with a tray of cookies and a barrel for you to fix like that...:D
 

L1A1Rocker

Active Member
I'll be over in a couple of days with a tray of cookies and a barrel for you to fix like that...:D

What we could do, is chuck it up in the lathe and lay out all the lines marking all the drill points. Then you could use a ball mill on your drill press to actually do the hard tedious work. :)

But first I need to finish this barrel of yours that is currently residing in the lathe. I've got the flat turned down and the steady in place. I've got a plan of attack ready for parting off the stub. I'm dealing with a few clearance issues as I'm kinda in a box but I got it figured out last night. Today/tonight, I'll part it off and have to do a lot of facing work to get it down to specified length. I'm thinking about making a shield of some sort to help keep chips out of the steady sense I'll be working very close to the steady's fingers.
 

Ian

Notorious member
More parts arrived today, time to put some stuff together. First the upper, which is a standard AR-15 flat-top upper I picked up on sale. I lapped the receiver square and enlarged the ejection port full-length to .625" so the brass would eject and reduced the radius a bit of the corners on the front. Of course the barrel nut was five pound/feet from spec when it was lined up with the gas tube, so I did what the armorers do and cranked the nut a few times to seat the threads and ended up about 30 lbs over spec to get it to the next notch rather than lap the shoulder more.

Nothing special on the outside, but here's a pic of the progress so far.

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F

freebullet

Guest
OMG, that barrel up there has measles, chicken pox, or an std...

I don't sign on for a few days & use guys barrels get sick.?. Dang...
 

Ian

Notorious member
More progress, L1A1 got my muzzle brake bored out to take the big bullets, and I got some other goodies ordered for next week so I can do some more fab work and get a handguard mounted (in case anyone was wondering what the heck I was thinking putting a GI delta ring on there with a pistol-length low-profile gas block, soon it will all make sense). Moving right along in step with all my other projects, can't wait to shoot this thing!
 

Will

Well-Known Member
Very interested in seeing your results Ian. This is one of those projects that come to my mind every few months. So far I have kept it to just reading and haven't let it get in my wallet.

I'd say this will be my next project after I get a 300 blackout built.
 

Ian

Notorious member
More money, more work, and a little more progress. Picked up a heat-shielded handguard, steel rail-height gas block, and some 4130 tubing. Gas block got bored and honed to fit the .850" barrel, fitted a steel washer to the end of the tube and TiG welded it in there, then bored it to fit over the barrel and welded to the gas block, gas block then pinned and cap-welded to the barrel to make a permanent 16.5" barrel length. All the holes drilled in the barrel extension serve three purposes: Reduce weight (3 ounces), make the alphabet agencies happy, and ventilate so the suppressor can have some air flow. The muzzle brake and suppressor fit inside for a short overall package and no SBR stamp or travel hassles.

Pictured next to my DI-45 which has a 16.1" barrel plus brake ( brake adds 1.5"), you can see the advantage to the barrel shroud when using a suppressor. The same suppressor fits the DI-45 and makes that little carbine LONG.

A little bit of lipstick, mascara, and some glasses and she'll be ready to go. I'm thinking DuraPark WWII green on the upper receiver, barrel extension, and handguard cap/delta ring.

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Ian

Notorious member
My DuraPark order should be in early next week, I'll get it torn down, bead blasted, and degreased before then. I also picked up some sights for it and maybe will get some group shooting in this weekend.
 

Ian

Notorious member
Well, got some shooting in, more questions than answers though.

Good news is my starting load is good, probably will be my stopping load, too. Nailed it thanks to Quickload. Got an average of 1080 fps for ten rounds and an SD of, get this, 4.8! That's 496 grains and 1275 lb/ft of Mastadon-stomping whupass. About like a 1-1/4 oz. 12 gauge slug, and kicks just like it too even with the can.

Bad news is three of ten hit the paper exactly sideways at 25 yards. Four had a little bit of tilt. Those that didn't tilt made a 5/8" group. No baffle strikes or Magnetospeed sensor strikes. Bullets were half a thousandth larger than groove size and the nose was a very snug bore fit. With a 14" ROT, JBM predicts a stability factor of 5.998 so it OUGHT to be plenty stabilized. Next step, as much as i don't want to, is shoot it without the can or chronograph attachment and see if that helps.
 

L1A1Rocker

Active Member
Well, got some shooting in, more questions than answers though.

Good news is my starting load is good, probably will be my stopping load, too. Nailed it thanks to Quickload. Got an average of 1080 fps for ten rounds and an SD of, get this, 4.8! That's 496 grains and 1275 lb/ft of Mastadon-stomping whupass. About like a 1-1/4 oz. 12 gauge slug, and kicks just like it too even with the can.

Bad news is three of ten hit the paper exactly sideways at 25 yards. Four had a little bit of tilt. Those that didn't tilt made a 5/8" group. No baffle strikes or Magnetospeed sensor strikes. Bullets were half a thousandth larger than groove size and the nose was a very snug bore fit. With a 14" ROT, JBM predicts a stability factor of 5.998 so it OUGHT to be plenty stabilized. Next step, as much as i don't want to, is shoot it without the can or chronograph attachment and see if that helps.

Well that's a bit disappointing. Just a thought here. Is the twist in the barrel really what is marked on the outside? Also, if you have access to a full face motorcycle helmet, it cuts the blast wave down a lot. No, I'm not joking. Earplugs and a full face helmet does work.
 

Ian

Notorious member
Good tip, but I sold mine with the bike well over 20 years ago.

The idea to recover some bullets came to me a little while ago, so after some digging in the berm I managed to come up with four of them, mostly they were the ones that went sideways and stopped shorter. Anyway, I think the alloy is just too soft. There are full-depth rifling marks clear up to the break in the ogive of the nose, and really bad washout marks on the back two bands, stopping at the back of the third band. They look like rodent chew marks, unmistakable. Washed out so bad there is very little evidence of rifling engraves on the bands. I don't think the bullets were stripping, but I do think they would have shot better if loaded backwards. That's what I get for shooting 8.5 bhn alloy at 30k psi with medium-slow shotgun powder. Something else I need to check is how badly these are getting sized down in the brass, a little rookie step I skipped.

Oops, thought I posted this earlier this afternoon, sat down to update and saw it still here. Forging on..
 

Ian

Notorious member
Ok, got it sorted. Bullets were getting squeezed down by the brass, causing blow-by, gas cutting, and acrobatic bullets. So I went through my whole die collection trying to find an expander big enough to do the job. Nothing. After a bit I noticed the Lee rifle PTE die insert in the bottom of my universal tool head can and mic'd it....471" OD. So I turned it down to .457" on my drill press with a file, shaped a nice bell shank, tapered the point, polished it, and fixed my neck tension while still being able to use my PTE measure.

After testing two other powders I've come to the conclusion that Quickload is simply off the mark by about 80fps and a LOT of pressure with Hodgdon Longshot in this instance. What really got me thinking is a hint of metal flow on the case head, just a slight imprint of the ejector hole and extractor groove, classic warning signs with the .458 that pressures were just at or a little over maximum. I had loaded 14.0 grains, predicted to be about 1000 fps and 26K psi. I got 1080 fps, which would take 16.5 grains to make by prediction, and 35500 psi, which is just over maximum, just like the brass was telling me. My explanation for the 80 fps gain over predictions had been suppressor "bump", which is common enough and I see it regularly. So I worked HS-6 and Herco for a while and the velocities were within single digits of predictions, so it wasn't the suppressor, it was an erroneous prediction. Herco was spot on with Quickload's predictions =/- 2 fps. Problem is, I want to stay around 25K psi and Herco has to run up near max pressure to get 1020. HS-6 does the pressure and speed fine, but has a really high muzzle pressure compared to Herco and Longshot. So I re-ran Longshot in Quickload, taking into account the 80 fps off the mark and came up with 12.7 grains for 927 fps. Shot those over the chrono and actually got 1005 fps with an SD of 1.2 for ten shots, so 78 fps off from the prediction. By adding powder to the prediction, my pressures come out at 28K at 1008 fps. Whatever. The 12.7 grain/1005 fps actual load is quieter than 11.5 grains of Herco at 926 fps, and the action works 100%, rifle feels good, and it shoots like a laser beam. I'm one happy camper now, sore shoulder and all, and that Mastadon is going to be in very, very deep poo....
 

L1A1Rocker

Active Member
I'm real glad to see you've figured out the problem. Looks like you are on the road to getting a good load. Are you powdercoating these?
 

Ian

Notorious member
Are you powdercoating these?

But of course! Cast and pre-sized another 150 after supper, got a small batch in the oven baking right now. I'll post-size the noses in my Lyman sizer, nose first in a .451" die which ensures they'll chamber, and then I'll size the bands in a modified Lee push-through so they come out .4585".

Yes, I'm already thinking about an Accurate mould for this, something about 530 grains, that can be hollow-pointed. I may hollow point one cavity of this Lee mould first and do some 'spansion testing. Also I need to hone out the neck of that Lee sizing die so it doesn't make the necks so small, brass after sizing are .452" on the inside.
 

Ian

Notorious member
100_4498.JPG Got it all coated and back together again. I'm really disappointed in the WWII green DuraPark product from Lauer, it was a bright, yellow-green and full-gloss, nothing at all what it should have been either in color or finish to replicate the greenish hue of some chromium-dip mil-contract Parker jobs. I had some black so I added that to dim it down and kill a lot of the yellow, but didn't have any matting agent to kill the sheen. Instructions say to dry-mist it in the end to give a texture, and that works fine, but gloss paint will always be glossy, even if the surface is textured. I selected the color based on wanting to put a matte-oil-finished walnut stock set on it for an over-all "WWII" theme, so it looks kind of goofy with the "FDE" tan furniture and lower, but for now it matches the 5.56 upper that normally goes on this rifle (note the YHM quick-disconnect action pins).

Would you believe that with my Form 1 silencer attached and seven rounds of the 500-grain bullets in the magazine the whole deal only weighs 7.5 pounds? It feels heavier than that, but balances at the front of the delta ring so it's very nimble.

An M-1008 truck makes a fine backdrop for the pictures.



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Ian

Notorious member
"Lipstick for a Pig" is what my boss called my ammo:

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Yes, there's a muzzle brake down in there, and I left some metal on the shroud on the sides to deflect the blast away from the sides when shooting unsuppressed. Interesting thing about how much this thing recoils with the 500-grain Lee bullets: The front end of the dust cover pin mushroomed so badly from peening against the barrel nut that it had to be filed down for removal to do the finish work. I need to put a small bit of heat shrink tubing on it for cushion so it doesn't happen again and ruin the finish.

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Ian

Notorious member
Finally got some pictures of the targets from my first outing.

Upper left is the very first one put on paper, at 25 yards. This is with the too-soft, just cast bullets which showed a lot of gas cutting on the bottom three drive bands when recovered. How about those key-holes???!!! Undersized bullets will do it every time.

The other three targets were fired after I honed the neck of the sizing die and made a larger expander spud, and recovered bullets showed only a little gas cutting on the base band. Herco test load on upper right (didn't lock back the bolt but would cycle) to see if the bullets would group. Lower left target was re-shot (group on lower right was re-shoot with same load of Longshot) after I noticed the front sight on the block had shot loose. This thing will rattle yer teeth.

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freebullet

Guest
That's awesome, Ian. Quite a journey. Looks like she came together pretty quick.
 
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