Playing with .22 tcm

[Oso]

Snert is right. Perhaps time to take a step back and shore up the fundamentals on forming your case before ramping up ammo production and potential risk.

All of the challenges with any new rifle, especially a wildcat or one-off is determining the chamber of your rifle. There are various tools/gages to assist in this process, and then there is some trial and error. Best practice is try to accurately measure these dimension in a controlled environment (i.e. no combustion). All of this is more complicated if the rifle is a AR.

Step 1 - Determine the chamber length. The common methods are to use are: (1) chamber length gage (see link); (2) start with long case and continue to trim it until the bolt can just barely close; or (3) last ditch effort is creating a chamber mold using cero safe.

https://www.brownells.com/reloading...s/sinclair-chamber-length-gage/?sku=749000811
This tool is easy to use and gives fairly reliable measurements. This will now give you your maximum case length. Keep in mind that during the initial fire-forming of your cases that the case length will shorten as the case expands and shoulders bump/fill out.

Next steps to determine Location of Shoulder and Neck Diameter. These will allow you to properly set up sizing die for shoulder bump and also determine what Neck Thickness is needed to provide adequate clearance.

 

[ebb]

Nice job, keep it up. A modern hornet, and a good thing to do with range pick up brass. I have wanted to build one but have finally figured out I have way too many rifles already.

 

[Wolfdog91]

Snert is right. Perhaps time to take a step back and shore up the fundamentals on forming your case before ramping up ammo production and potential risk.

All of the challenges with any new rifle, especially a wildcat or one-off is determining the chamber of your rifle. There are various tools/gages to assist in this process, and then there is some trial and error. Best practice is try to accurately measure these dimension in a controlled environment (i.e. no combustion). All of this is more complicated if the rifle is a AR.

Step 1 - Determine the chamber length. The common methods are to use are: (1) chamber length gage (see link); (2) start with long case and continue to trim it until the bolt can just barely close; or (3) last ditch effort is creating a chamber mold using cero safe.

https://www.brownells.com/reloading...s/sinclair-chamber-length-gage/?sku=749000811
This tool is easy to use and gives fairly reliable measurements. This will now give you your maximum case length. Keep in mind that during the initial fire-forming of your cases that the case length will shorten as the case expands and shoulders bump/fill out.

Next steps to determine Location of Shoulder and Neck Diameter. These will allow you to properly set up sizing die for shoulder bump and also determine what Neck Thickness is needed to provide adequate clearance.

O so I did actually make a chamber cast, do thom to most of my new gun, easy deal actually


But by the time I made that I had already did the whole shoulder find thing the way I usually do. Which with AR's is pretty simple. Measure a fire formed case set my die to knock the other case to the measure ment then just dropping it back it it chambers with no real resistance. Usually it's anywhere from. .003 to .005 depending, I've tried to do just .001 buuuut that tend to give me more problems then I'd like with my semi autos.

That being said I did't take any measurements of for the chamber cast after I figured out the whole brass thickness issue

One of the main problems I'm having is there no information out there for doing this type of stuff for a bottle neck cartridge... In a blow back rifle. No one does it . Much less even mess with one.

Now when I talk to people who do shoot blow backs, apparently what I'm getting as far as my shoulders is actually normal apparently it's just kinda a quirk of the system, idk

 

[Wolfdog91]

there is not enough gas for a DI to work. Get a hold of Macon Armory to talk about a DI gun. He has done them in 45acp and I think 9mm. He would be the guy you need to talk to. Even about your situation you have now. He might have already done it.

Apparently there one or two guys who made one work pretty well the AR guy being one

 

[Wolfdog91]

1) You cant measure brass neck thickness like you showed in the photo. The caliper will bridge and the measurment will be all over the place. You have to use a ball mic. So your measurements of your brass thickness are useless. They are not real.
2) Since your brass shows clearly that your cases are NOT forming consistently, and your primers are backing out, it is evident that the cases are backing out of the chamber (in a sense your "die") as they are forming. This is because every one seems to be moving differently as the bolt backs up under recoil. You will never get good brass using this technique.
3) Your primers are backing out because your headspace is all over the place. Your initial fireform relies on the bolt moving at the same rate and timing on every case, but your handmade cases are too thick in the neck for a proper bullet release. So the whole process is irregular, hence irregular brass.

No offense, but you are playing with a bomb in front of your face.

Just cause you haven't eaten gas yet doesn't mean you won't. I am not being a jerk. I am just warning you that you are on really shakey ground.

If you insist on forming brass from a blow back, you have to:
1) get a good chamber cast and get real measurements
2) learn to use a ball mic and neck turning equipment
3) understand that your case(before fireforming) has to have a loaded round clearance inside your chamber neck area of .003 at least of you are sticking bullets in the case until the case starts to back out.
4) Understand that all the powder, spring, buffer changes will not fix these basic issues of case forming.

Honestly, I admire your gusto, but you are into areas that are going to end up with broken guns, fingers and eyes. Spend more time researching fireforming, neck sizing, wildcatting and less making ammo before you hurt yourself.

So actually now I'm not having the primer issue now that I moved to the other brass. Again most of these problems just stemmed from me trying to get this too think homemade brass to function, and now that I've moved to factory I'm just not having those problems

 

[Oso]

It can be interesting, frustrating, and rewarding being one of the few to tackle a uncommon or new cartridge. Yes, a lot of people won't appreciate the effort and there will be a lot of people shaking their heads while you stumble through figuring it out. Without prior experience, good mentor, or YouTube video, doing any case conversion / case forming for even a well-established cartridge can be difficult. Yes, there are threads, but most use big brush stroke that don't capture the finer details that a less experienced reloader may need to feel confident with the process. I have been in both places. My posts tend to be longer because I remember blankly staring at some post trying to figure it out...

Sometimes there is a timing difference to where you are in your process and the timing of our input. I think you are doing well with asking for advise and receiving feedback. Keep up the good work.

 

[JSH]

I will admit to being plain ignorant for the most part on AR’s. 99.9% of the issues I see with AR’s are when they are using a cartridge it was not designed for. Buddy built an AR in 6.5 Grendel, problems problems. My suggestion was an adjustable gas block and tune it to the cartridge and the load. Worked fine until he changed loads. Retuned and went on.

 

[Wolfdog91]

I will admit to being plain ignorant for the most part on AR’s. 99.9% of the issues I see with AR’s are when they are using a cartridge it was not designed for. Buddy built an AR in 6.5 Grendel, problems problems. My suggestion was an adjustable gas block and tune it to the cartridge and the load. Worked fine until he changed loads. Retuned and went on.

Problems like what ? Built my last Grendel from dog crap parts and works just fine. I mean maybe a bit over gassed but
Also Grendel was legitimately designed for the AR

Now this deal... I'm used to a stand DI gas. This is a blow back so different world

 

[Knotwild]

You piqued my curiosity. The website below offers some good information.

The AR Guy

 

[Sniperhandle]

A page back or so I could tell one of your problems was the cases were too long, The necks were crimped in from bottoming out on the end of the chamber. So either your chamber is too short, Or your cases are too long.

That is all I can help you with, Looks like a fun project, I like doing weird stuff with bolt guns like you are doing here. But as others have said, It is dangerous, I wouldn't discourage from experimenting but wear good safety equipment and rig your gun into a rest or something until it's proven.

Edit to add pic:

This your pic, I have seen this before with a short chamber. At least that is what it looks like to me, Do your home made cases measure the same length?

 

[Tommie]

The problem is a bottleneck cartridge in a blowback gun (as others have already pointed out). The same issue happened when gun manufacturers jumped on the 17 HMR bandwagon. Remington ultimately recalled the 597 in HMR. Ultimately the problem was solved with a delayed blowback design.

You’re trying a cool project and I wish you luck. But be careful.

 

[livelyxp100]

RMW extreme built me one in di and works great with the mean arms mag inserts