300BlkTalk

dellet wrote: ↑Mon Aug 15, 2022 5:43 pm

Demphna2 wrote: ↑Mon Aug 15, 2022 5:00 pm

dellet wrote: ↑Mon Aug 15, 2022 12:48 pm

That’s why I keep a standard spring, and both a carbine. 2.7 oz and an H2 buffer around. Trouble shoot with the parts it was designed to work with. Then modify.

The brace I'm using uses smaller components than normal. The JP SCS XS is another option they offer. I could go with their version of buffers and springs. I think the JP SCS XS standard weight buffer is 2.2 oz. If I drop the buffer weight to 2 steel weights, that gives a buffer weight of 1.4 oz.

My thought is to try a lighter spring first though. Kind of concerned none of this is going to get it to work, but there's only one way to find out

Sorry, but can’t really help. I know the system and load data quite well for the system as designed. Go help, I really would need to know how you designed your system to operate. In essence you have redesigned the AR15 into something it was never purposed to do.

You also want to use load data that was never really developed to work commercially because it has a narrow window of operating pressures.

Combining to experimental systems is problematic. Make sure one works properly. Then the other. Then combine. There’s no easy way about it.

Just to clarify, my system is equipped to run subs and supers. I've dedicated it to run subs only. CFE BLK (dirty and loud), H4198, and N110 and 190 gr Sub-X have all run without a hiccup with a standard JP SCS XS (maxim brace), a regular mass BCG, and an Ultra 9 suppressor.

The problem I have with N105 is N105. I have ran out of load length to play with, so I am basically tinkering and tweaking the gun to run the load. Mainly because it's challenging and I enjoy eliminating the variables. So Dellet, I don't fault you for not being able to help in this particular situation. In the end, it may not run the way I want it to. As long as I have tried everything besides drilling the gas port larger.

Update:

Loaded up 7.8 gr, 7.9 gr, and 8 gr. Installed Lightest spring

8 gr - 1042, 1057, 1045.
Only loaded one round first to check BHO. Achieved it, but subsequent shots did not lock back.

7.8 gr - 1040, 1025, 1028. All cycled, no BHO.

Tried 7.9 and replaced the one tungsten weight with another steel weight. Close, but no cigar. Did not chronograph these rounds.



Damn, it's close.

If you have the room, move the bullet out on the 8.0 load .020”

dellet wrote: ↑Mon Aug 22, 2022 11:01 am If you have the room, move the bullet out on the 8.0 load .020”

I am currently at .008" off the lands. Still have some things to try, but in the grand scheme of things, I'm reduced to wondering how important is BHO?

If you’re maxed out for overall length, I would minimize headspace. Make sure the cases are fully fire formed and only set the shoulder back .003”.

Depending on your chamber, that will be around 1.075-1.080. Maybe even longer, measuring with a .350” diameter insert which is most common.

dellet wrote: ↑Tue Aug 23, 2022 5:10 pm If you’re maxed out for overall length, I would minimize headspace. Make sure the cases are fully fire formed and only set the shoulder back .003”.

Depending on your chamber, that will be around 1.075-1.080. Maybe even longer, measuring with a .350” diameter insert which is most common.

Just checked my notes and measured a few cases just to be sure. I'm setting the shoulder back .0045".

Updates:



9 rounds at 60 yards.

N105 7.9 gr.
2.15 col BTO 1.664
ES 21 SD 7 Average velocity 1053 fps

Now about function. Some weird shit going on. I used JP SCS XS standard first, then switched to 2 steel weights, then one steel weight and a Delrin weight. All used with the lightest spring JP offers(85).

If I loaded one round through the ejection port on top of the mag, it held back on empty. If I loaded 2 rounds into the mag, it didn't hold back on empty. This was with the standard (one tungsten, one steel) and with 2 steel weights.

The bolt held back on empty with the Delrin and steel weight combo. I did not have enough rounds loaded to try 2 more into the mag with this buffer weight.

Next step is trying more rounds with Delrin and steel weight. After that, I may need to clip a coil or 2.

https://photos.app.goo.gl/DFH4qJudnDYsjqd77


Got it working. It took one steel weight and a Delrin weight with the lightest JP spring.

Most likely getting set back or set forward with the cycling of the action. Very common from what I've seen. Most of the time people using expanders or madrel dies without enough neck tension.