30cal Integral Bolt Rifle Build UPDATE 5/24/2019

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T-Rex
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30cal Integral Bolt Rifle Build UPDATE 5/24/2019

Post by T-Rex » Fri Apr 05, 2019 7:20 pm

Here we go again. Another long and drawn out build :lol:

This one here has been on the project table for about 10 years. I always knew what I wanted, but it's taken a while to get there. Other projects took precedence and I was never really in a rush, anyway. The rifle has never been a pile of parts so it's always been shootable.

This started out as a Plain Jane, Savage 308; even though, I knew I needed a 223 bolt face. I got it in a trade, at a great price, so I wasn't in a position to be picky. Thanks to the miracle of the internet and the Castboolits forum, there was a guy living 3 miles away who wanted to do a bolt and barrel swap. That was easy.

I got a 1:8 30cal barrel blank, which I measured at 8.5:1 (is that odd?), chambered it for 7.26x39 and threaded the muzzle and tennon. I, also, opened the bolt face for the new cartridge and installed a modified extractor.

Rifle in factory stock.
Image

The next step was a new stock and a drop magazine. After quite a bit of research, I settled on a Choate Tactical with PT&G bottom metal and MTD molded magazines. The Choate stock seems nicely made, albeit the grip is quite large. I will have to do some sanding on the right side . The LOP is about 13", where the Savage is at 14". This will be remedied when I get into modifying the stock.

So, the first sorts was to see if we needed any inletting, for the bottom metal. The good news is that the PT&G bottom metal will fit the Choate cutout. However, the bottom metal's uppermost portion has too much metal. It will not rest far enough into the stock's magazine inlet. This is due to Choate's aluminum "core" embeded in the stock. If one was so inclined, they could do some milling to the stocks magwell area. Im just not sure how much of the aluminum is there and wouldn't want to weaken the stock.

Here is the PT&G bottom metal, before being molested.
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This is how much material I had to remove.
Image

No big deal, just some aluminum

The bottom metal drops right in and lines up nicely. Unfortunately, the front action screw is about 8 threads into the lug area. I have a choice: cut 8 threads off the screw (about.3") or make a spacer for the bottom metal's screw cavity. I make a spacer. Its .375"OD x .32"L with a .25" clearance hole.

Everything bolts up nicely now. Mag slides in and comes out with little effort, not drop free (although time and use may change this).
Image
Image

Yes, the mag reads .223. I did some filing on the lips and the .308x39 works like a charm.

The only issue I see is that the barrel is not centered in the stock's channel. It is favoring the right side by .125". I loosened everything up, but it all fits perfectly, misaligned. I planning to remove about 5" of the stock's forend and fit an integral silencer so, for me, this will not be an issue.

It looks like I'll be able to get a 1.375", over barrel, tube to fit inside the barrel channel. This should work nicely.

As you can see in the below picture, my plan was to shorten the forend of the stock (approx 5") and create an adjustable butt. The blue parts, on the buttstock, are the prototype pieces as I have made some revisions that will be reflected in the next print.

Image

Fully extended, the LOP will be about 14", about 1/2" more than the Savage factory.
Retracting the stock will decrease OAL by about 3.75", for the prototype. The next build will be more like 3.5".
The bipod shown is 9"H, the final build will have a 6" version.

Final build pieces for buttstock fitted. Spare scope thrown on for some pics.

Extended
Image

Collapsed
Image

I'm contemplating rebuilding the adjustable assembly out of Aluminum. For now, though, the 3D printed parts perform almost flawlessly.


So, this gets us to where we currently lie. The form has been approved, for some time now, and I've gone through several revisions. At First, the plan was to use a K baffle similar to the ones in my 45 Mauser. Then, I revised to mimic the stepped style in my AR22 build. Finally, I settled on a 60* cone with some extra features and a radius clip.

This was the first design
Image

With these baffles
Image

Then, these baffles
Image

I settled on this design
Image

With these baffles
Image

The plans I was using, when I first started cutting everything, had 10 baffles with a spacing of 9/16". I made an 11th hour decision, actually 2, to change the baffle configuration and add indexing/alignment tabs. This last revision brought the baffle count to 14. The blast baffle and the next 3 will be spaced at 9/16". The next 4 will be @ 1/2". The final 6 will have a spacing of 3/8".

I lied. I made 3 final revisions. The last baffle was to have no skirt. I changed this to have a skirt, that slipped into the end cap, and turned into the wedge for a wipe, if ever I wanted one. So, 14 baffles and a wipe :)

Yes, this will be a true integral. The barrel will be ported, just after the throat. Being that the outer tube is .058, 6061, I've allotted for an internal blast shield, made from 310SS, around the ported area.

My original subsonic loads, from the 17" barrel, only filled the case approx 70%. I would use some polyfill to make up the rest. I plan to change to a different powder, one which will fill the case to ~96% and yield ~1350fps. I'll be shooting a baseline of 5 rounds, then, cutting the first 3 ports. I'll repeat this until I hit around 1000fps. We'll see how it goes.

Barrel nut: Sorry for the craptastic photography. Which, is a shame because it came out beautiful.
Image

Baffles, patiently waiting for the mill
Image

Muzzle brake portion, pre-welding.
Image
The brake is cut for a 5/8" hex so a socket can be slipped into the tube for removal. If you're wondering why I Didn't make the blast spacer in 1pc, it's because I had some tiny drops and I'm not one to waste material. My welder is great at making short things longer :)

I will continue to update the OP as I progress. Just don't expect to see it with finish or get a video, as I rarely come through with either :lol:

-------------------------------------------------------------------UPDATE 4/6/2019---------------------------------------------------------------------
Face milling is complete
Image

I haven't, yet, purchased a rotary table, but I'm making do with the Luan dividing plates :)
Those are brass stops, for holding place on a framing square. Simply index the angles, set the stops, and you can easily cut arced slots.
Image

This is the mandrel I made, to hold the baffles.
Image

-------------------------------------------------------------------UPDATE 4/7/2019---------------------------------------------------------------------
Out of this batch, just need to cut the index tabs for the blast baffle spacer. I'll do this after the barrel headspace is set. Made another change. Was planning to leave the blast baffle alone, but gave it a symmetrical, radius clip. This will be indexed 90* from the rest of the baffles.

Image

Should be cutting the endcap and, possibly, the outer tube, tonight.

-------------------------------------------------------------------UPDATE 4/13/2019---------------------------------------------------------------------
OK. The suppressor parts are complete.

Image
Image

Tonight, I'm going to start on the Barrel Nut wrench and see about putting 2 pins in the handle for an End Cap spanner.


-------------------------------------------------------------------UPDATE 4/25/2019---------------------------------------------------------------------

Alright. I'm, now, just waiting on some time to shoot and chrono. I think I may have a powder to where I won't need to port the barrel for a velocity drop. In which case, I'll port near the muzzle and make use of the over barrel chamber.

While I'm waiting, I made an insertion/extraction tool for the baffles. It has a hook/lip, a spring, and lines up w/ the baffle's index tabs.

Image
Image
Image

Put the baffle on the disc. Push the extractor through the clip. Rotate. Insert baffle into tube. Align index tabs. Push tool and rotate extractor to align with clip. Remove tool. Yes, the tube is clean, for now, but it works great. We'll see how things go once I'm done w/ a shooting session.

-------------------------------------------------------------------UPDATE 5/5/2019---------------------------------------------------------------------

Got out to shoot today, as planned. I started with Quikload's 100% case fill.

Win 7.62x39 case
CCI 200 LR primer
7.7gn Trailboss powder
190gn HPBT projectiles
COAL 2.265"

I tried these with both an old batch of primers and a new box. Also, I did 3 separate strings w/ no crimp, a light crimp, a mild crimp. There was little difference between the 2 primer boxes even though date of Mfr is 30+yrs apart. The no crimp rounds gave the most velocity and a consistent SD.

I need to get out and do larger strings, but here's some unsuppressed firings. These are from a very steady rest. All flyers were marked with outside the norm velocities.

55*F, 800' ASL, 0 wind, Light Rain, 52m Target Distance

Image


At this point, I was quite happy and decided to put the suppressor on. Now, I wasn't happy with where the initial headspace was and redid it after the first 2 rounds (from the start of the day, unsuppressed). This rotated the baffle clip from how I originally wanted it. The common baffles should have been North or South orientation. They're, now, at the East/West. Suppressed groups were shot with all common baffle clips at the shooter's 3 o'clock. You can see what a dramatic POI shift there was, once the suppressor was added (the 7.7gn group). This shouldn't matter as the group size didn't seem to be too affected and this will be shot 100% suppressed. For the 7.8gn, suppressed, group, I dialed the scope to a new zero.

Image

I plan to trim the muzzle brake a bit as to reorientate the clips to the intended North/South index. Also, I think I might deepen the common baffle's clip cut. Same cutter dia, just a bit deeper. Suppression seemed pretty good. I was shooting from inside and towards a wall of windows. I should have stepped outside, for a shot or 2, but time ran short and I had to clean-up.

Now, for a vote. As there's no need to port near the barrel's chamber, should I port near the muzzle (before the threads)? I have a large over-barrel, reflex volume that isn't being used. I also have the option of cutting slits into the rear portion of the blast chamber. Thus, allowing the initial blast into the reflex portion, instead of porting the barrel. I'm leaning towards porting the barrel.

-------------------------------------------------------------------UPDATE 5/11/2019---------------------------------------------------------------------

Finally made a video. I have a Ruger MKII w/ an AAC Pilot in there for a comparison. Also, I put my dedicated AR22 SBR in there.

Here you go, John :lol:

I pushed the loading up to 8grn of Trailboss and think this would be about max case fill. Still subs.

I still plan on reindexing the mount, to orientate the clips back to North/South. I'll shoot again, for a POI baseline, and, then, plan to port near the muzzle.


-------------------------------------------------------------------UPDATE 5/18/2019---------------------------------------------------------------------

Well, that POI shift was non-existent. Turns out, the suppressor tube was rubbing against the stock's barrel channel. Once rectified, I fired 3-2rnd groups, in the following config:
No tube or internals
Tube installed
Tube & internals

Here's all 6 rounds, with the same POA

Image

I'm not 100% certain on the order fired, but this is pretty much a zero POI situation.

Next step is porting near the muzzle.

-------------------------------------------------------------------UPDATE 5/24/2019---------------------------------------------------------------------

I completed the muzzle porting. (6) 3/32 holes arrayed around, (5) arrays spaced 0.20, starting 1.00 from muzzle.

Image

I only popped off 5 shots, but there's an extreme difference in sound reduction. I'll have to get a new video up.
Last edited by T-Rex on Fri May 24, 2019 5:48 pm, edited 13 times in total.
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John A.
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Re: 30cal Integral Bolt Rifle Build

Post by John A. » Fri Apr 05, 2019 7:46 pm

I'm subscribing because that's nice work.

Video is required though. Sorry that you thought it was optional.

It's not.
I don't care what your chart says

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Re: 30cal Integral Bolt Rifle Build

Post by fishman » Fri Apr 05, 2019 8:32 pm

Exciting
300 blackout form 1: http://www.silencertalk.com/forum/viewtopic.php?f=10&t=137293

5.56 form 1:
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=141800&p=955647#p955647

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Re: 30cal Integral Bolt Rifle Build

Post by ECCO Machine » Sat Apr 06, 2019 10:38 am

I like it!

I think the switch to cones was a good plan.

I am curious, though; since you'll be hand loading anyway, why 7.62x39 instead of 300 blk?
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Re: 30cal Integral Bolt Rifle Build

Post by liquidrush » Sat Apr 06, 2019 10:58 am

You might have chambering, extraction and ejection problems opening up a 223 bolt face, the extractor and ejector pin will be in the wrong place. Being a push feed the lip of the extractor goes over the case upon chambering and it's likely too far in towards the center of the bolt face. I've got a savage I run with a bunch of calibers including 762x39 and use the PPC bolt head from PTG for that caliber, they are not that expensive. The only successful bolt face open up I did with all of my calibers was a 223 to 5.45 russian and I still had to shorten the extractor slightly to get it to chamber and extract and it works great. 5.45 is a total sleeper for suppressing, they sound great.

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Re: 30cal Integral Bolt Rifle Build

Post by T-Rex » Sat Apr 06, 2019 11:51 am

Update in OP
John A. wrote:Video is required though. Sorry that you thought it was optional. It's not.
We'll see, John, we'll see :wink:
ECCO Machine wrote: I think the switch to cones was a good plan.
I think so, too. Soon to find out.
I am curious, though; since you'll be hand loading anyway, why 7.62x39 instead of 300 blk?
2 main reasons.
1. I started to develop this project about 4yrs before 300blk was adopted.
2. 300blk has been done to death. I've built almost a dozen AR's and 3 bolt rifles off of it. The donor rifle I'm using to test the porting is a 300BLK, Savage, SBR. I did that for another trust, almost 2yrs ago.
liquidrush wrote:You might have chambering, extraction and ejection problems opening up a 223 bolt face
Worry not. I've been using this rifle for about a decade. The modified extractor is the PPC one from SSS. Other than a few squibs, I can't recall this rifle ever having a single malfunction. Let's keep that going.
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Re: 30cal Integral Bolt Rifle Build

Post by ECCO Machine » Sat Apr 06, 2019 2:15 pm

T-Rex wrote: 2 main reasons.
1. I started to develop this project about 4yrs before 300blk was adopted.
2. 300blk has been done to death. I've built almost a dozen AR's and 3 bolt rifles off of it. The donor rifle I'm using to test the porting is a 300BLK, Savage, SBR. I did that for another trust, almost 2yrs ago.
Makes sense.

Too bad it's already stamped as a .30; .338-.223 straight would be a nifty integral build!
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Re: 30cal Integral Bolt Rifle Build

Post by T-Rex » Mon Apr 08, 2019 12:39 pm

ECCO Machine wrote:Too bad it's already stamped as a .30; .338-.223 straight would be a nifty integral build!
When I was planning the project, initially, I believe I was looking at the 338 Spectre. However, I was already forming cases for a couple other firearms and really didn't want another. The x39 brought the case capacity down, from x51, and that's where I decided. Also, 30cal projectiles are plentiful and cheap. I'm thinking about doing a 458 Socom, with integral suppressor, for an AR lower I have laying around, that happens to already be SBR'd. We'll see. I have 2 or 3 more projects to start, after his one, and a couple still to finish.
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/7/2019

Post by #40Fan » Mon Apr 08, 2019 4:04 pm

Looking good.

One question. Is the brake going to "unload" into the first section of the tube or in the same tube as the cones?

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Re: 30cal Integral Bolt Rifle Build UPDATE 4/7/2019

Post by T-Rex » Mon Apr 08, 2019 5:41 pm

#40Fan wrote:One question. Is the brake going to "unload" into the first section of the tube or in the same tube as the cones?
The brake and blast chamber are solely for the muzzle forward portion.
The coaxial volume, in the over barrel section, is for gasses released by the barrel porting.
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/7/2019

Post by T-Rex » Thu Apr 11, 2019 6:27 pm

I'll get some more pics up, either tonight or tomorrow. All the parts will be complete. I just need to test fit to the rifle, face off the final length for the tube (once headspaced and assembled), and clean everything.

A couple items I could use some input on.

I've used a lot of different projectiles, for subsonic 30cal. I really like the heavy, HPBT SMK's, but they can get pricey and I'm just plinking. For 300blk, I've settled on the Leatherhead 220's. I've yet to try the Berry's 300 220gr Blackout Spire Point. Does anyone have experience with these?


Another item is barrel porting. I've only ever ported 3 barrels and only 1 of those was to drop velocity. For this one, I just copied the Mist barrel. The others' porting was closer to the muzzle, to use the over barrel section, and cut-down on muzzle brake length. Here's my current plan.

Image

I'm going to shoot a baseline (no holes), then do the first row of 6 holes, 60* apart, in the grooves.
Shoot a chrono test and repeat w/ row 2.

So, a couple things about the porting:
1. How's the layout look?
2. My groove measures ~.100in. I have drill bits all over this size range and a 3/32 and 2mm end mill. Unfortunately, I have no reamers near these sizes. I could lap the barrel, but this will take a good deal of time, especially with a ll the potential rows and tests I could be in for.
3. For the 3 barrels I did port, I only used a reamer on the 22lr and that's just because I had one in that size. However, I put a brass or wood dowel in the bore. I think I did 2 w/ wood and 1 w/ brass. I can't honestly remember which was which or the immediate results, but I've not seen accuracy issues from any of the barrels.


I have to make some parts so I can move the dividing plate, from the spindle nose to the outboard side (left). This will allow me to index and center off the barrel's groove, at the muzzle, and, hopefully, keep the porting w/in the grooves. I should only have to turn 2 parts, but I'll need to fab a new arm, for locking the plate in place. Also, I have to make a combo, barrel nut and end cap wrench. I believe the scope rail is a bit long. I'll be looking at putting that in the mill, too.
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/7/2019

Post by fishman » Thu Apr 11, 2019 7:35 pm

any burrs you create during drilling will quickly be removed after a mag dump.

People seem to feel the need to put the ports in the grooves. I don't know if there's any data to support this practice.
No problems here:
https://i.imgur.com/BU9mrZq.jpg
300 blackout form 1: http://www.silencertalk.com/forum/viewtopic.php?f=10&t=137293

5.56 form 1:
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=141800&p=955647#p955647

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Re: 30cal Integral Bolt Rifle Build UPDATE 4/7/2019

Post by Capt. Link. » Fri Apr 12, 2019 12:43 pm

T-Rex wrote:
A couple items I could use some input on.

I've used a lot of different projectiles, for subsonic 30cal. I really like the heavy, HPBT SMK's, but they can get pricey and I'm just plinking. For 300blk, I've settled on the Leatherhead 220's. I've yet to try the Berry's 300 220gr Blackout Spire Point. Does anyone have experience with these?


Another item is barrel porting.

Image

The 240 SMK is tops in the 300 Whisper class but others may work well.
If you change your porting position to the throat area you don't need to figure the land and groove plus the number of ports is reduced as is their size.The reamer will remove the port burr but it must be done with great care as a chip lodged in a hole will jam your tool.The gases re very hot and high pressure so even lead reloads don't clog the ports.

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Re: 30cal Integral Bolt Rifle Build UPDATE 4/7/2019

Post by fishman » Sat Apr 13, 2019 5:13 pm

I've yet to try the Berry's 300 220gr Blackout Spire Point. Does anyone have experience with these?
Yes. Thats my standard bullet over 7.7 grains of lil gun
300 blackout form 1: http://www.silencertalk.com/forum/viewtopic.php?f=10&t=137293

5.56 form 1:
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=141800&p=955647#p955647

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Re: 30cal Integral Bolt Rifle Build UPDATE 4/7/2019

Post by T-Rex » Sat Apr 13, 2019 6:01 pm

Update in OP

Running a bit behind schedule, but that's not abnormal. The tachometer in my mill stopped working. The Mfr sent out a new one and I've got it installed. A managed to get the outboard spindle dividing plate mount made. I was able to just spin the current locking arm 90* and viola.

Image
Image

The first piece goes over the end of the spindle and locks w/ set screws. The dividing plate slides onto this and the second piece follows. Sandwich the plate between the 2 parts and fix the set screws of part 2. Index the plate to zero (corresponding w/ the correct index line on the part). Put the locking pi in the plate's zero hole (or necessary index point) and fix the (2) SHC screws on the outside on part 2. The collet draw bar fits in the ID and can be used in conjunction w/ the plate setup.



fishman wrote:Yes. Thats my standard bullet over 7.7 grains of lil gun
I think I'll order some and give 'em a try, next to the Leatherheads, during the porting testing.


Thanks for all the IM's. The knowledge and experience being shared is greatly appreciated.
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/13/2019

Post by cdhknives » Wed Apr 17, 2019 4:01 pm

I've used a lot of different projectiles, for subsonic 30cal. I really like the heavy, HPBT SMK's, but they can get pricey and I'm just plinking. For 300blk, I've settled on the Leatherhead 220's. I've yet to try the Berry's 300 220gr Blackout Spire Point. Does anyone have experience with these?
I was disappointed in the accuracy of the 220 Berry's bullet. It was running about 1.5 MOA where Nosler or Sierra match bullets would run about .75MOA. Not bad and a great alternative to cast for a cheap bullet, but not as accurate by a noticeable margin. I run Blue Dot in my 10.5" 300bo loads. No issues with the plating or such as some have reported 'on the internet'. :lol:
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/25/2019

Post by T-Rex » Thu Apr 25, 2019 7:39 am

Minor update in OP :D
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/25/2019

Post by John A. » Thu Apr 25, 2019 8:26 am

You've done a really good job on this. I see the amount of work and thought you have put into it. It shows. Well done for sure.

I have a few recipes for the 223 gr leatherhead cast bullets in the BLKout. They're OK for plinking and target shooting and playing around. That's about it though. I have managed to wrinkle the tip on a few of them from recovering them from the berm. They don't expand at all but like I said, they're OK for a cheap plinking bullet without killing your wallet.

If you'd like some of my load data, let me know and I'll PM them to you.

Have you considered porting the barrel and tapping the holes so you can add/remove ports and allow you more ability to tune the gun and the load you're shooting? I did that on my AR blackout integral project. It's just a shame to have all that space over the barrel going unused.

For the ports in my barrel, I used positive stop 6-48 stainless steel screws from brownells so I could ensure that they would never vibrate loose and work their way into the bore. And I also didn't thread the entire depth of the ports to further ensure that the screws couldn't enter the bore.

Probably over-kill, but I prefer to err on the side of caution.

Image

Here is a link to the screws. For the amount of time you've put into the project, this will only take a few minutes.

https://www.brownells.com/gunsmith-tool ... od792.aspx
Last edited by John A. on Sat Apr 27, 2019 10:35 am, edited 1 time in total.
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/25/2019

Post by T-Rex » Thu Apr 25, 2019 12:50 pm

Hey, John. Thank you for the compliment. I truly hope anyone reading, novice or expert, gets some satisfaction.

The real reason for the over barrel portion was to drop velocity due to having a limitation on powder selection. I wanted to fill the case and be closest to subsonic. If I don't need to drop velocity, then the only thing to do, to use the over barrel volume, is to port near the muzzle. You're idea won't really work, in this situation, as this is a one stamp gun. The tube is going to be affixed to the barrel nut, which is affixed to the barrel. Also, I'm welding a thin piece of tube to the barrel nut, that slides into the rear of the tube, to protect the Aluminum wall from the direct blast of the gas. Both of these scenarios would cover the vents and not let me readily access them. I'm sure I could epoxy or red loctite a tight fitting blast tube to the barrel nut, but, being that the tube is fixed to the nut, I won't be able to get back in there if it separates.

I had thought about making a type of gas block, that covered the barrel porting (near chamber) and allowed me to adjust the venting gas, from the exterior of the tube. I'll only have to look at this option if I feel like messing with powders and projectiles.
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/25/2019

Post by John A. » Thu Apr 25, 2019 1:10 pm

Well, I see the dilemma in why you don't port the barrel now if you're having to perm. attach the can.

But it would work great if you weren't.

It gives you the ability to tune the gun and the hand loads.
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/25/2019

Post by garredondojr » Thu Apr 25, 2019 9:51 pm

Being a bolt gun and a suppressed one to boot wouldn't you want the fastest and least amount of powder to maximize or better yet minimize the amount of gasses needed to be cooled?

Trail boss would fit the bill nicely and also fills up the case pretty well.

Red dot is fairly bulky and would also work well but won't fill the case all the way.

So for example using VV N320 (which is rumored to be a special powder made specifically to burn cool for suppressors in 9mm) 6.1gr (estimating a 10" barrel? and a 220gr SMK as a baseline) will yeild 1000 ft/sec with a muzzle pressure of 2763 psi

Going to lil gun like someone mentioned does this powder charge jumps to 9.5gr and muzzle pressure goes to 4664 psi

another notable mention is the lil gun load runs at 16.5k psi (great for case life but not so good for es/sd/consistency) and the VV N320 was 35.4k psi. some powders need pressure to burn correctly and cleanly.

one more. Red Dot 5.9gr, 2890 psi @ muzzle, 36.4k psi chamber pressure

Just something else to ponder :D

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Re: 30cal Integral Bolt Rifle Build UPDATE 4/25/2019

Post by T-Rex » Thu Apr 25, 2019 11:29 pm

garredondojr wrote:Being a bolt gun and a suppressed one to boot wouldn't you want the fastest and least amount of powder to maximize or better yet minimize the amount of gasses needed to be cooled?
You want the fullest case (best chance for even velocities)
A solid subsonic velocity (factoring bullet weight, temp extremes, etc)
As close to 100% powder burn (keep everything as clean as possible)
A good chamber pressure (powders work best with pressure and it keeps brass and chamber cleaner)

Trailboss is well below the velocity I'd like to be at, with a full case. I would have to drop bullet weight to the 168 area. This is a reason I thought of incorporating an adjustable gas block.
Red Dot only gets me near 60% case capacity.
VV N320 is less than 60% case capacity.
Lil'Gun is about 50% case capacity and the chamber pressure is very low.

I'm leaning towards H4198 and . I'll be a bit over fps, but get a decent powder burn and pressures will be between 20-35% below Pmax.

I've been doing the subsonic 30cal for quite a while now and have been through a lot of powders. I started w/ 308 and, while it's decent, it just wasn't meant for subsonic. This was my next project and I'm seeing it through. 300blk has come and been beaten to death. It's so easy now that its just another 5.56 round :lol: .
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/25/2019

Post by fishman » Fri Apr 26, 2019 3:14 pm

Lil gun needs a high chamber pressure to get reliable consistent ignition
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/25/2019

Post by cdhknives » Fri Apr 26, 2019 6:44 pm

garredondojr wrote:Being a bolt gun and a suppressed one to boot wouldn't you want the fastest and least amount of powder to maximize or better yet minimize the amount of gasses needed to be cooled?
Fastest powder (insures good chamber pressures) that gets the heaviest bullet to about 1050 fps (and stays under max pressure for this cartridge) will generally generate the least gas and should be the quietest. In my experimentation that was Blue Dot for my 10-11" barrels, and I tried over a dozen powders.

I am less enamored with the 'fill the case' rule many use. So long as I get consistent velocities and good accuracy I don't care what the case fill is, and this cartridge is going to be well over 50% for just about anything that meets my above criteria. When loading for subsonic, treat this like a pistol cartridge for the most part IMO...rifle primers but pistol loading rules and powders.
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Re: 30cal Integral Bolt Rifle Build UPDATE 4/25/2019

Post by John A. » Fri Apr 26, 2019 6:49 pm

Have you tried #9 and Enforcer powders? They're pretty fast burning and quiet too.

I don't know what the chamber pressure is (it's pretty high and up near standard 556 territory if memory serves correctly), but 8.6 gr of either is quiet.

The Enforcer is a little more quiet and still reliable (in semiauto) down into the low 800 fps territory. But my HD and hunting loads are 8.5 gr of #9 because the velocity is up around 1030'ish with everything from 190 up to 220 gr pills.

I would love to hear what your blue dot recipe is. Are you shooting it in bolt/single shot or semi?
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