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

[cdhknives]

I tried WC820, which is a 30 carbine surplus powder roughly equal to AA#9. It was just okay. If you want a spreadsheet with the 1050 fps QL run let me know and I'll send it. I can't seem to find the max pressure sheet.

The exact qty of Blue Dot is largely irrelevant if you load for subsonic velocities. According to QL 6.99 Grains of BD was 1050 fps, my load was slightly higher to hit that velocity, but the QL pressure was only 25kpsi at that load. I had Quickload run both a max pressure with 220 grain match bullets and a 1050 fps load, and worked up until I hit about 1050 fps or the QL max charge or overly flattened primers. I did this for every powder in my cabinet from Universal to H110. The most accurate was H110 but Blue Dot was close and was significantly quieter through the can. Cleaner too. 25kpsi is okay for BD but H110 calc'd about 21kpsi and that is the dirty burn region for that powder. Sooty cases confirmed that prediction.

I am shooting it in a straight pull/side charging 10.5" SBR AR with no gas system and a blocked barrel port, through a YHM Phantom suppressor. It is not the greatest suppressor for subsonic work for sure, but it does work.

[T-Rex]

What are these loads for, that you guys are referencing? 300blk, 9mm?
My 308x39 has twice the usable case capacity as 300blk and about 3x as much as 9mm.
The same loads are going to be totally different.

cdhknives, my experience w/ case capacity and velocity is quite the opposite. Even with fill percentages as high as 75%, I would see inconsistencies w/o adding some other variable. I'd need to point the muzzle into the air and slowly rest to the bench, before firing. Drilling the flash hole and using mag primers. In myy most recent load, for this rifle, I use .9grn of polyfill. My velocities are very consistent, but pressure is low and the results are dirty. The suppressor is dirty from <100% burn and polyfill, and the chamber and brass are dirty from low pressure.

BlueDot only gets me 45% case fill, with 100% burn, with a good velocity, but terribly low pressures. I could go to 70% case fill, with keeping a safe pressure, but now the velocity is up near something w/ better case fill and an acceptable pressure curve.

An M1 Carbine isn't a very good example because you're pushing a bullet, that's roughly half the weight, twice as fast.

John, the #9 and Enforcer aren't ideal. Enforcer is 40% case fill (@ 100% burn), with very low pressure. #9 is almost identical.

I'm going to push forward with expecting to port the barrel. However, I'm also going to think about and start a deign for an adjustable gas block. I don't necessarily have to employ it, but it would be a nice feature to look at. I found a decent supply for blem 168gr SMK's and these showed promise w/ not having to port the barrel and get a decent load data for. At least I have some options.

Thanks all for keeping the ideas flowing.

[John A.]

I've been using enforcer for plinking and #9 for hunting HD loads in my 300 blk.

While I have tuned my sbr ar to run these loads (lightweight buffer and spring and tunable barrel porting) they work just fine from 190 to 240 gr pills I have used.

Here's a 50 yard group from a rest. Most all of my hunting & shooting is well within 100 yds

[T-Rex]

I've been using enforcer for plinking and #9 for hunting HD loads.

But what cartridge are you loading these for?
As I said, 300blk's case capacity is half that of my current project. Comparing the two isn't apples to apples.
I have 4 different, reliable, 300blk loads and non of them are even close to adequate for 308x39.

[John A.]

I was referring to 300 BLK.

I'll go back to my posts and specify so no one looks at it and gets confused.

[T-Rex]

I was referring to 300 BLK.

What 190's are you using?

[John A.]

The groups were shot with cheap(er) nosler HPBT.

Though I also shoot the 194 gr Lehighs too. Just a different seating depth. Everything else being the same between the two.

[T-Rex]

The groups were shot with cheap(er) nosler HPBT.

The Custom Comp bullets? I was looking at these. Someone was selling blems for like .22/ea.

[John A.]

Midway has a lot of 308 Hornady blems at the moment.

I currently still have a bunch of the match kings. Looks like they've raised their prices since the last time that I ordered from them.



https://www.midsouthshooterssupply.com/ ... -100-count


sample pack
https://www.midsouthshooterssupply.com/ ... e-20-count

I actually would like to try their competition pills. $27/100 ct isnt' too bad.

https://www.midsouthshooterssupply.com/ ... s-50-count

[T-Rex]

That sample pack is nice, not sure if it's enough though. 50 would probably be min I'd buy. Can always shoot them through 308, if the subsonic isn't great.

I was looking at these190 blems. They have the 168's as well.

[John A.]

That's a good price. Shipping isn't all that great though once that's figured in.

I have wondered about the speer hot cor bullets. They seem like a viable plinking round.

https://www.speer-ammo.com/products/bul ... ullet/2211

[garredondojr]

hmm. how about spinning up a new tube in 7.62x25 tokarev both different and more efficient for your purposes.

I buy most of my bullets from here. shipping sucks unless you make a worthy order which is what I do a few times a year. http://www.shootersproshop.com/nosler-p ... 100ct.html

[T-Rex]

I ordered this mixed bag. There's a 25% off coupon (25rifle) and free shipping so the total was $47.25 for 250 bullets or about $.19/ea. This gives me plenty to tinker with while developing loads. I can always use them for .308Win and 300Blk.

[cdhknives]

cdhknives, my experience w/ case capacity and velocity is quite the opposite. Even with fill percentages as high as 75%, I would see inconsistencies w/o adding some other variable. I'd need to point the muzzle into the air and slowly rest to the bench, before firing. Drilling the flash hole and using mag primers. In myy most recent load, for this rifle, I use .9grn of polyfill. My velocities are very consistent, but pressure is low and the results are dirty. The suppressor is dirty from <100% burn and polyfill, and the chamber and brass are dirty from low pressure.

BlueDot only gets me 45% case fill, with 100% burn, with a good velocity, but terribly low pressures. I could go to 70% case fill, with keeping a safe pressure, but now the velocity is up near something w/ better case fill and an acceptable pressure curve.

With traditional bottleneck cartridges I see the same as you do with regards to case fill and reduced velocity deviation. My hypothesis on heavy subs in 300bo subs is twofold: (1) that 300bo has much of the usable case volume in the narrow gap down the sides of that long 220 grain bullet and that doesn't ignite well, and (2) it burns powder like a pistol, not a rifle. Consider most pistol rounds. Especially older loads like 45ACP or 38 spl are notorious for low fill % but shoot very well. In my experience when I think of heavy subs in 300bo like a pistol cartridge I have better luck developing loads. So I load something fast, that builds pressure quickly to get the powder 'hiding' around the sides of the bullet ignited, and use powders designed for the pistol pressure ranges, not rifle or even mag pistol pressures...even if the end result of that logic is a low case fill.

But we all know if we reload long that every rifle is a study unto itself and what works in my 2 barrels may easily be unique to my set up...and me not caring about cycling an action simplifies the process a LOT.

[T-Rex]

The mix bag from AmericanReloading worked out very well. The advertised 250 was shipped as 269 projectiles. Out of these, 241 were 190 HPBT's. I checked seating in the chamber, to the lands, and it looks like 7.7gr of Trailboss might be the strarting ticket. 100% case fill, 100% powder burn, projected velocity of 1028fps, and Pmax of 30Kpsi. I was hoping the pressure would be a bit higher. Going to give them a small taper crimp (Lee FCD) and test these as well. I should be able to get outside Sunday to do the testing. They're calling for 40% chance of rain so let's keep our fingers crossed.

[garredondojr]

sounds like a winner

[T-Rex]

Update in OP

[daviscustom]

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.

Looks like a nice rifle T-Rex!

If it were mine I would just make the blast chamber liner so it fits over that little shoulder on the front of the brake so that the big port is in the rear expansion chamber (it is hard to tell in the assembly drawing). If you dump that big port into the rear chamber instead of the blast chamber that should do as much or more than porting behind the break (may want some perforated spacers back there to divide up the volume some....maybe some chore boy) . If you think it would be better to port too I would just bore back far enough to have a recessed crown that would allow for porting behind the brake. Either way I think it would be silly not to use that space. I can't see any possible way it would make the rifle louder and it won't be that difficult to do.

[fishman]

I vote you port the barrel near the muzzle

[T-Rex]

Update in OP

[fishman]

Update in OP

Sounds like your microphone is clipping the peaks off of the sound by quite a bit.

[T-Rex]

Update in OP

Sounds like your microphone is clipping the peaks off of the sound by quite a bit.

Hmm, I'm not getting that. If anything, I'd say the sounds are depicted louder than actual. FRP is easily distinguished across all platforms. But, It's a 15yr old Kodak digital, that wasn't made to be a hi-res video recorder so I don't doubt any inconsistencies. Best I have, though.

[daviscustom]

I'm not really noticing clipping. I would think they would all sound about the same volume if hey were clipping, and there seemed to be variation.

They seemed to be shot in order of quietest to loudest, but none of them sounded loud.....just different. Is that similar to the "in person" perception?

[T-Rex]

They seemed to be shot in order of quietest to loudest, but none of them sounded loud.....just different. Is that similar to the "in person" perception?

In terms of overall sound, yes, I'd say that's correct. However, the silencer on the dedicated AR is quieter than the Pilot. It's just that the action noise is so much louder. I have the Delrin stops installed. As well as the o-ring mod and the detent ball, to slow the action's unlocking. The bolt gun is a nice deep thud. The bullet hitting the 3/4" plywood, at 100yds, is pretty close to the noise the firearm is making. Also, just cycling the action is about on the same plane. In one of the shots, you can hear when I hit the metal pipe holding the target stand. I'm going to tinker with baffle arraignment and the barrel porting. I'll do it in stages, to get the most info out of the various conditions.

[T-Rex]

Update in OP