The 300 BLK Bolt Action Project

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Netpackrat
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The 300 BLK Bolt Action Project

Post by Netpackrat »

Been posting about this over in Does Not Follow, but since it is looking more and more like it is going to be a saga rather than the simple assembly process I had envisioned, I thought I would make a new thread.
Netpackrat wrote:Factory synthetic stock arrived today. PTG bottom metal doesn't fit... The mag well is roughly 1/8" too long for the opening in the stock. Because of the way the stock is made, I'm not sure it can be made to fit without weakening it too much, at least without glass bedding to fill all the molded in voids. I'm probably going to send the mag well back.

The good news is AAC obviously made their barrel to the factory contour, so the barreled action is a decent fit. The barrel doesn't free float but I was planning on a bedding job anyway. Looks like the pillars I ordered are going to be too big in diameter, so I will end up using stainless tubing instead similar to what I did with my other Seven.
Wednesday came and went, as did Thursday, and I did not call PTG. After having let it stew for a couple days, I finally decided nothing ventured, nothing gained....

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The infamous Dremel... But like any other tool, it can be used for both good and evil. Besides which, it's not as though this is much of a stock; it's probably the cheapest part of the project, so far. If I screw it up and have to start over, so be it. I used a small sanding drum to do the bulk of the material removal, and finished with files.

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Here is the mag well bottomed out against the molded in cutouts. There is still a bit of a gap between the stock and where the mag well steps out to overlap it, which turned out to be significant when I tried to put it all together. It's a bit of a tight fit in the stock, because as you will see in the next photo, I didn't want to remove any more material than absolutely necessary.

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Yeah, I am going to need a bit of bedding compound in there. I was glad to be able to get it to fit without breaking into that void in front of the magwell.

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Trial fit. I don't have my action screws yet, and the main one from my other Model 7 is too short (so the one I ordered probably will be too). Found that the mag well is too low (remember that gap?). If I push up on the bottom of the mag, it will amost feed. Looks like I am going to have to cut the inlets a little deeper, which is going to suck. Good thing I was going to pillar bed it anyway. I may need to polish the feed ramp some, also. The detachable AICS magwell may not even work out at all, in which case I'll end up going with the standard floorplate arrangement, and probably buying another stock to go with it.

I also ordered a different set of bases plus the stuff to counterbore them to take the stupid oversize 8-40 screws that the receiver is drilled and tapped for. If that doesn't work out it looks like I will have to spend way more money on a custom base.
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HTRN
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Re: The 300 BLK Bolt Action Project

Post by HTRN »

Very few of the aics magwells are "drop in" fits for bdl bottom metal. CDI even has a inletting service to deal with it for their bottom metal.
HTRN, I would tell you that you are an evil fucker, but you probably get that a lot ~ Netpackrat

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Netpackrat
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Re: The 300 BLK Bolt Action Project

Post by Netpackrat »

HTRN wrote:Very few of the aics magwells are "drop in" fits for bdl bottom metal. CDI even has a inletting service to deal with it for their bottom metal.
Not a word about any inletting required on PTG's product page for the magwell I bought. It's pretty clear once you have the parts in hand that no matter what a lot of inletting will be required since the magazine will barely fit into the magwell cut in the stock, even without the well.

And given what I have seen so far, I have serious doubts that I will ever get this setup to feed properly, so I have most likely wasted my money on the stock, magwell, and magazine. If and when I give up I will have to buy another stock and all the factory bottom metal and magazine stuff, which total up to about the same cost as the mag and bottom metal I already have. Thought briefly about getting one of the chassis systems but they are expensive and ugly as sin.
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slowpoke
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Re: The 300 BLK Bolt Action Project

Post by slowpoke »

Does anyone make drop in 300 blackout barrels for the mossberg 556 bolt guns? Those guns use a barrel bolt like the Savage rifles so should be easy to change out. Been thinking of getting a ruger american in 300blk, but using AR mags would be better.
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Netpackrat
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Re: The 300 BLK Bolt Action Project

Post by Netpackrat »

If you peruse 300blktalk.com you will see that lots of people have had problems with their Ruger rifles in 300 Blackout. Mainly problems with light primer strikes due to things like out of spec chambers. The small shoulder on the blackout case does not seem to be very tolerant of Ruger's shoddy machining processes.
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Netpackrat
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Re: The 300 BLK Bolt Action Project

Post by Netpackrat »

My most recent order from Brownell's came this morning, and I was at least able to get some scope bases on it. I was able to modify a set of Leupold's Redfield type bases to work with the 8-40 screws... The counterbore that Brownell's sells for this was only partially useful; the pilot was too short and too small diameter for the existing holes, but I was able to start the counterbore with a 1/4" chucking reamer, and finish with the counterbore. The last hole in the rear base I wasn't able to use either of those tools because the top wasn't square, so I had to put a small diameter stone in the dremel and slightly enlarge the counterbore until the head of the 8-40 allen screw would enter. Then I had to shorten one of the screws for the front base because it was long enough to bottom against the barrel threads in the receiver.

Also the Gemtech shim kit I ordered from Amazon arrived. I installed the 2mm shim under the 51T flash hider and got it bottoming on the shoulder instead of the muzzle face, and then reinstalled the FH with Rocksett and torqued. Alignment with the can on checked out OK although it's still not exactly tight on the mount. While I had the FH off I measured the barrel length with a cleaning rod down the bore, and the AACholes only gave me 1/16" over 16 inches, so machining the muzzle face back and re-crowning was never really an option.
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HTRN
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Re: The 300 BLK Bolt Action Project

Post by HTRN »

Are you sure you got the right bottom metal? I would check part numbers to be sure. The AR bottom metal mentions inletting, and even has a pdf download. You might want to take a look at it.

I'm not surprised you had a problem with the factory stock, considering its mostly hollow, injection molded, like 99% of factory stocks. Frankly, I would have done the inletting for the bottom metal last, as the epoxy bedding filling all the voids would have made it easier to remove material from the bottom without the stock wanting to collapse.
HTRN, I would tell you that you are an evil fucker, but you probably get that a lot ~ Netpackrat

Describing what HTRN does as "antics" is like describing the wreck of the Titanic as "a minor boating incident" ~ First Shirt
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Netpackrat
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Re: The 300 BLK Bolt Action Project

Post by Netpackrat »

It's definitely not an AR mag, and the holes seem to line up.

Edit to add; there are no markings anywhere on the mag well, but it's obviously what I ordered.
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Netpackrat
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Re: The 300 BLK Bolt Action Project

Post by Netpackrat »

Futzed with it some more, and I'm going to have to give up on getting the AICS type magazine to work. I used the front bedding pillar and the action screws I ordered from Brownells to mock up the action and bottom metal without the stock, and by progressively shortening the pillar I was able to raise the magwell and mag relative to the action, to the point where it almost works, and it does actually work as a single shot, but about 50% of the time when feeding the top round into the chamber, the next round will take a nosedive in the mag. Then it is out of position to feed when the bolt is cycled again. No matter how much I raised the mag well and mag, it always did this.

Turned out I had ordered both regular and extra long action screws, and by the time I gave up, not only was I using the standard length screw, I'd actually shortened the pillar far enough that the screw was protruding into the action sufficiently to keep the bolt from closing, the mag was as high up as it would go, and the rounds were still nose diving, so I don't know what else to do with it. Too bad I borked that stock fitting the bottom metal, but I didn't have any reason at the time to think that the detachable mag system wasn't going to work, and at least it wasn't an expensive stock.

I think the mag well would likely still work with a .308 length cartridge, but I have no interest in screwing with my 7mm-08 in an attempt to find out, or particularly in buying a .308 length AICS magazine to do so with. I think it's also likely that the .223 AICS magazine would work with .223, but for me at least it did not work with .300 Blackout at all. The rounds I used to test feeding were 220 grain UMC. Thought about trying it with supers to see if the bullet weight was a factor, but I think if it won't feed subs then there isn't much point in it to begin with, so that would be a useless test.

Moving forward I am going to buy a better stock and the Remington magazine parts, but possibly not right away... I'm kind of tired of spending money on it for now. Since I screwed with the mag well and mag, trying to return them is out, and I expect I will just try to sell them at some point.
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"People come and go in our lives, especially the online ones. Some leave a fond memory, and some a bad taste." -Aesop
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slowpoke
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Re: The 300 BLK Bolt Action Project

Post by slowpoke »

It appears in 2014 Mossberg announced a 330blk mvp, and then promptly put it down the memory hole. Tromix made a 300blk barrel for it but dont anymore. Likely due to the FUD from Mossberg.
The Ruger American light strikes tend to be due to out of spec (.003 or more short of min at the shoulder) And are easily fixed by tightening head space. At least according to the 300blk message board above.
If I get one and its trouble I'll let you know so you can tell me you told me so.
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