Where to go from here?

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Augenblick
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Where to go from here?

Post by Augenblick »

The love/hate relationship with reloading 300 blackout and my Sig rattler continues.

For reference the rattler has a 5.5" barrel with a 1:5 twist. Short stroke piston and a two position gas block, normal and adverse. It is suppressed with a SilencerCo Omega 36m.

300 blackout was my first foray into reloading and I didn't realise it was the deep end of the pool

I started out with CFE BLK then got 1680 and most recently H110 at which point I understood why people are so critical of the first two powders. They are so loud and dirty. Currently using cci400 primers.

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I'm pretty sure that is all unburnt powder. It is all inside my suppressor and the action and fire control group.

On the positive side the rattler has stabilized everything I have put through it, no keyholes. The action fully functions with all three powders on the normal gas setting. And I have achieved the 1050 fps goal with all three of those powders. The CFEBLK and 1680 stuffed to the gills of course.

So here is what I'm trying develop as a range round. It is a cast 220 grain HiTek bullet from Steel Valley Casting $187/1000.

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The drive band is sized .309" but seems to be .310" to me.

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1.3" in length.

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The bore rider measures about .303".

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It has a little bit of a boat tail.

Overall I like these. Groups 2" to 4+" at 50 yards depending on powder, charge and seating depth. I haven't been seating some of these as long as recommended because they won't fit in my Sheridan gauge but I'll try that to work on accuracy.

What I want to do next is find a faster powder that will hopefully be quieter and less messy/dirty. From all the reading I had done in these forums I was really liking the sound of N105 but it is discontinued.

So 300blktalk community where would you go from here?

What powder do you think would work? I still have room with the gas block.

Is that SVC 220 grain bullet just not suited for 300 BLK subs and/or the rattlers tiny barrel and fast twist?

I'm looking forward to hearing your thoughts.

As a bonus question what suppressor would you put on the rattler to do both subs and supers? I ask because I didn't read the fine print. For the Omega 36m it is rated for supersonics in 300 BLK down to a 7" barrel. Would going to the adverse gas setting buy me that missing 1.5" of barrel length in terms of drop in muzzle pressure?
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dellet
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Re: Where to go from here?

Post by dellet »

Certainly unburned/partially burned powder. The faster the powder, the less of that you will have.

I flip flopped between Accurate #9 and N105. Not much difference between the two, N105 is a bit bulkier, but you will probably use about 1/2 grain less than #9.

Another good candidate is Accurate 11FS.

With those bullets be aware of you neck thickness. About .011” max or a loaded diameter
of .332-3”. You will get a cleaner release of the bullet from the neck.

The Sheridan gauge is a problem with coated bullets. It’s just too tight. Check then in your bore. Could be better, could be worse. Honestly a long, bore riding nose in an AR is a mistake. No matter what you do, I’d feeds into the bore at an angle. Next time out shoot a round then eject the one that just chambered. Heck and see if the bullet is still straight, and not all marred up.

They can work ok, but frustrating to get MOA groups. Then add in the fast twist and any imbalance from the coating or gouge from chambering and it’s a disaster. Load them with the .310” portion barely out of the neck. The throat in the chamber is not much over .309” so not much room.

The 265 acme bullet is the same way, want really designed to be shot from an AR, but I was getting sub 4” groups at 200 yards with it. Others got better.

Maybe ask omega if they have a pressure rating instead of a barrel length?

See if you can get a “standard”, basically it is a precision ground steel rod that will be a certified length. Then check your caliper readings. In short words, calipers suck for accuracy and repeatability. If you really need to trust the measurement, A micrometer is a much better tool.

Side note, the reason I don’t have a barrel shorter than 7” is because it also makes a huge difference in noise and flash. Pretty much settled on 7.5-8”.
300 Blackout, not just for sub-sonics.
Augenblick
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Re: Where to go from here?

Post by Augenblick »

I knew someone was going to mention that I need a longer barrel. I agree. I will get an 8-10" barrel at some point so I can really make best use of this cartridge. For now I'm committed to gettiing the most out of the rattler that I can. One thing reloading this cartridge has given me is a good understanding of how much I didn't know going into this. I really do enjoy the rattler but I would do it over differently.

Thanks for your thoughtful response Dellet. It is a lot to unpack. I'll pick up some Accurate #9 soon. Wish N105 was still available. Looking forward to cleaner and quieter.

Interesting about the neck thickness I'll take a closer look at that as I was just relying on the sheridan gauge. I think I'm coming in at .333-4" right now. I'll try that seating suggestion relative to the neck as well. I made some dummies to cycle through and was pretty happy with them.

I thought about the pressure angle with th omega 36m. One good thing about cfeblk is it has some really low pressure supersonic data. Maybe that could work.

Thanks again for your 8nsight. I really appreciate your time.
Roadrunner1969
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Re: Where to go from here?

Post by Roadrunner1969 »

Augenblick wrote: Mon Apr 17, 2023 5:30 pm

300 blackout was my first foray into reloading and I didn't realise it was the deep end of the pool

That is an understatement!
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dellet
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Re: Where to go from here?

Post by dellet »

No need for a longer barrel, I just prefer the noise reduction. It is significant.

Side note is that 1/5 barrels over 8” are a problem waiting to happen if you shoot supers. If the barrel is long enough to get over 2200 fps, a lot of jacketed and some specially expanding bullets start failing. 300,000 rpm is tough on bullets.

I have a 24” 1/6, max velocity based on bullet rpm of 325,000 is over 2700 fps. Never had a bullet come apart. I have to back off my favorite 110 grain load in an 8” 1/5 if I want to shoot a hot barrel. Bullets come apart as they leave the muzzle.

Yes, the Sheridan is unforgiving. Absolute minimum chamber. Great tool, but if you can’t seat a bullet straight, it’s likely to fail the gauge. Or if you don’t get the burr off the neck after trimming. Picks up a lot of errors. It will also show you the 300” point on your bullet. That’s where the coated bore riders have a problem if the mold doesn’t account for the thickness of the coating.

Lots Of little things to jam you up.

Consider that the cartridge loads bullets from 85-265 grains, 900-3000 fps. Barrels are common 5-20”. Gas guns, bolt actions and single shot. Won’t bring up the clown that did a lever gun.

If you like to tinker with loads, it will keep you busy.
300 Blackout, not just for sub-sonics.
Augenblick
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Re: Where to go from here?

Post by Augenblick »

I have about 750 of the SVC 220 grain bullets left so I'll continue to tinker with them. My fired brass of course won't fit in the Sheridan gauge but it also isn't open enough to easily insert a new bullet in the neck. I don't know if that gives any insight as to how the neck tension is on these rounds. You mentioned seating the .310" portion of the bullet just out of the neck.

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Something like this? This is 2.15" OAL.

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This is where the bullet stops in the gauge.

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And this is the bullet in the case in the gauge.

I full length resize with a Mighty Armory die and I have to say I really love it. It does a great job, super quality and super smooth. I expand with a Lyman M30 die just enough to let the bullet seat and not scrape the coating. I set with a Forster micrometer die and finally finish with a Lee factory crimp die.

To see what was happening to the bullet I used the dummy and cycled it through five times. The first pass I didn't really see anything but each subsequent cycle added it's own marks. I can definitely see those causing accuracy problems.

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I had to remove some pictures of the bullet damage because of "too many URL's."

It still fit nicely in the Sheridan gauge so I think the bullet remained straight.

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I was looking for a good cast bullet to play with at the range. The other one I tried was the Missouri 217grain but I had problems with keyholing with those in the rattler. Aside from accuracy issues.

I have used Hornady 220 grain round nose at 2.1" OAL and Their 195 grain sub-x which both shot much tighter groups than cast bullets.

Do you think Magnum primers would help with unburnt powder issues?
Augenblick
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Re: Where to go from here?

Post by Augenblick »

Dellet I meant to ask you about the 300" point you mentioned talking about the Sheridan gauge. I couldn't find it anywhere.
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dellet
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Re: Where to go from here?

Post by dellet »

Take a look at the chamber drawing below. Your gauge is cut to minimum chamber numbers.

Neck is .335”. For a good clean release of the bullet, you really want about .003” clearance. Might be why the neck is still tight on the bullet after firing. To know for sure you might want to fire some supers. The higher pressure may open up the neck more and give a better example of fully fire formed brass.

Ahead of the neck is a .309” diameter section. If your bearing surface is .310”, you want to seat the bullet short enough not to jam there. That’s why I brought it up.

The .309” section tapers to 300” at 1.7368”. You’re gauge does not have any grooves that would be cut to .308”, only the bore or lands at 300”. The 300” point on the ogive is basically max loaded length when it hits the lands.

This is why I brought up the problem with calipers. Your nose diameter measured .303”. If it’s truly .303” you probably won’t be able to insert the nose of the bullet all the way down to the bearing surface that is .310”. Try pushing the bullet nose intonthe wrong end of the gauge and see.

Use the back half of your calipers and measure the inside diameter of the gauge at that end. Do the measurements make sense?

If the gauge measures 300” and the bullet .303”, why does the bullet fit the bore? If it actually does.

Note the diameter of the bullet where the marks are. Maybe they are from the bullet hitting the lands as it’s chambered.

Try loading some by hand, pushing them into the chamber with your finger and slowly closing the action using the forward assist to close it. If accuracy improves greatly, you’re on the right track.

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300 Blackout, not just for sub-sonics.
Augenblick
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Re: Where to go from here?

Post by Augenblick »

I measured the bore rider section of the bullet this time using the "blade" part of the calipers instead of the flat. I measured .298" -300". The end of the Sheridan gauge measured 300". The bearing surface measured .3085" - .310" at various points. Highest at mold seams.

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Here is the 300" point marked on the gauge and this round passes the gauge at OAL of 2.21". So I think I have a better understanding of that. Of the hundreds of bullets I've sorted with a bullet comparator in getting BTO .845" - .870" so about .025" variation. Not sure how that compares to cat bullets on average.

I picked up some Accurate #9 so I'm trying to find load data for it. The only thing I have is Hornady 11th for 195, 208 and 225 grain bullets. This search has me asking why is it so hard to find bullet lengths!

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Here is a SVC 220 grain next to hornady 190 grain sub-x. They are all loaded at 2.25". I loaded a bullet onto an empty and seated it to 2.25" it failed the Sheridan gauge as I expected. I loaded it directly into the chamber of the rattler but I had to release the bolt with some force to close it as the rattler doesn't have a forward assist. I ejected it and repeated it several times and it only left a small ring in the HiTek coating.

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I did not get all the damage I saw from chambering from the magazine so I assume that goes back to what you were mentioning earlier about issues with a long bore rider chambering in an AR platform.

As I mentioned the OAL of 2.25" failed the Sheridan gauge. I forced it a bit to see where it was failing and it was at the transition edge from bore rider to bearing surface again to your point of not loading that part past the neck very much.

For the 208gr 8 gr of Accurate #9 is 1100 fps.
For the 225gr 8.3 gr of Accurate #9 is 1100 fps.
The SVC is 1.3" long and I found a source that had the 225gr bthp at 1.558" with plastic tip at .175". However I couldn't see a plastic tip. So I have a slightly lighter, shorter bullet but I need to seat it shorter than 2.25" to pass the gauge. However it did chamber in the rattler.

Is 8.3 grains a reasonable starting place?
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dellet
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Re: Where to go from here?

Post by dellet »

Hopefully all those numbers make more sense, and why getting accurate measurements is critical.

As far as load data, 8.3 will be real close, maybe on the slow side. Hornady probably still lists a 190 grain super load, 1200 fps in a 16” barrel. Since you’re missing 10” of barrel, that may not be as high as it seems. Hornady 9th, 8.9 grains.

My load is 8.2 grains in an 8” barrel.

Just be.careful of a double charge. Maybe drop one in a case to see what it looks like. A double charge will ruin your day.

Many Lengths found here, base to ogive would be real helpful. Also has stability ballistic, BC calculators and other good stuff.

https://www.jbmballistics.com/ballistic ... gths.shtml
300 Blackout, not just for sub-sonics.
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