Form 1 can doing strange things.....180 Rain Wedge CFEBLK

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MountainmanID
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Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by MountainmanID » Mon Sep 03, 2018 2:28 am

First post, Hello everyone.

The same Form 1 can (6 conical flat faced baffles +1.5" expansion chamber before first baffle/clipped bore holes; 2x8" total size; bore dia. : .376 (3/8")) is causing a decent increase in accuracy in my RARR bolt gun and a HUUUUGGGGGEEEEE loss in accuracy in my 10.5" AR,pistol gas.

Load is 180 gr rainier wedge round point bullet, seated in mixed mostly LC convert brass at 1.955-19.965 OAL. 10.0 gr even of CFE BLK with my hornady progressive priming, expanding mouths with a Lyman M die, charging the 10.0 gr which is very consistent using the pistol drum on the hornady powder measure, seating to OAL, then it goes through a Lee factory crimp Die to barely remove the bell in the case/may crimp it a tiny bit. These lock the bolt open on last round in my AR, with or without the can. They also stay subsonic out of the RARR bolt gun.

What would cause a Can to both increase and decrease accuracy in the same load?


Pics attached are groups shot at 30 yards.

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smustian
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Re: Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by smustian » Mon Sep 03, 2018 10:14 am

Have you checked bore concentrisity with an alignment rod? Check to see if there are any baffle strikes? What style clips? Are the clips aligned? Thickness of endcap tunnel?

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Re: Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by golfindia » Mon Sep 03, 2018 11:37 am

Is the first baffle clipped?

How is the can mounted? I made a direct thread can with a threaded mount that wasnt perfectly flat. It did crazy things until I re faced the mount to make it sit flat on the barrel shoulder.

I could easily see this issue looking down the bore.

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dellet
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Re: Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by dellet » Mon Sep 03, 2018 1:06 pm

Two different rifles, two different results. No surprise there.

As the others have suggested make sure the bore of the can is aligned with the bore of the barrel, it may be fine on the Ruger and not on the AR. That would make the most sense from the photo.

Hard to say from the photo and the target backing, but looks like some stability issues with the bullet. Lower velocity in the shorter barrel might have compounded that and had them bouncing around inside it.

Where did you get your load data, and what was the actual velocity?

I don’t know is a dangerous answer.
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John A.
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Re: Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by John A. » Mon Sep 03, 2018 3:58 pm

Curious to make sure the twist rate is right too.

Aside from that, I suspect that the 10.5" ar bullets are kissing the baffles or endcap and is playing pinball inside with the baffles.

I am going to echo everyone that has said to get an alignment rod and check it before you shoot it on the AR again. It's just a matter of time before the bullet exits the side of the can rather than through the front endcap hole.
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Re: Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by MountainmanID » Mon Sep 03, 2018 6:13 pm

dellet wrote:Two different rifles, two different results. No surprise there.

As the others have suggested make sure the bore of the can is aligned with the bore of the barrel, it may be fine on the Ruger and not on the AR. That would make the most sense from the photo.

Hard to say from the photo and the target backing, but looks like some stability issues with the bullet. Lower velocity in the shorter barrel might have compounded that and had them bouncing around inside it.

Where did you get your load data, and what was the actual velocity?

I don’t know is a dangerous answer.
I'm not sure how to do a multi-quote reply on this site, so I'll try to answer all the questions asked.

Load data was based on a thread on this site that said around 11.0 gr of CFE BLK with the 180 wedge bullet made a functional round for an AR and also stayed subsonic in a bolt gun. I started with 11.5 and worked down to 10.0. The AR is still locking back on the empty mag, so the charge could probably be reduced further. I haven't had a chance to run these over the chrony yet, but I'm guessing 800-850 in the AR and 900-950 in the RARR.

The can is based on this cleaning kit: https://www.form1builder.com/product/2- ... -trap-kit/

I'm very happy with the performance sound-wise, and concentricity. Those guys make a great product and the only thing I might've done different was had them bore the barrel side end cap and thread with 3/4" size and use different stainless thread adapters for whatever gun its getting mounted on. I have a 5/8-24 to 1/2-28 adapter made by them that makes the can a lot of fun on 5.56 and 22 LRs. I also wish they would've made the end caps have some type of outer diameter shape so a wrench could be used to remove and tighten them. So far I haven't had any serious issues taking it apart to clean, but I clean every 250 rds or so.

I've never used an alignment rod but looking down through the can into the barrel, it looks perfect. Going to .375" was a decision made based on using home cast Lee 300BLK bullets with shake and bake powdercoat. I still haven't found a great way to use those bullets without tumbling issues, but it was apparent from the random baffle "kiss" locations that the bullet was just starting to tumble near the end of the can.

I had originally played with a .320" baffle bore diameter, but changed it to .375" after I noticed some powder coat barely shaving off on the end cap and last baffle. The approved Form 1 was submitted with ".30 cal." as the caliber but if I'm correct the supp. can be basically any internal dia., as long as the intended caliber can fit through it. I had a 07FFL/SOT on the east coast for 5 years and remember tranferring YHM phantoms that were labeled .30 caliber on the Form 4 but actually measured around .370" or so at the end of the can.

The clip job was a 1/8" hole cut right on the edge of the face of the cone baffle when it was .320", when bored out to .375" the clip just makes the baffle bore look a little like a keyhole. The can has 6 baffles, with the clip holes oriented every 2 hours around the clock from the barrel end to the supp end when re-assembled.

Twist rate on both is 1-7", with the AR being measured a little closer to 1-7.25".

The endcap hole is the same .375" bore and measures .240" thick


EDIT: While were on the baffle bore size discussion, how much bang stop am I gonna lose on the .30 cal if I bore to .400" or so to allow 9mm carbines to spit through it? The 2" dimension is outer diameter so while the can has a decent amount of volume, its not as big as the Coastal MIMS can we used to run on 9mm ARs with great suppression.

That was a .45 cal can but IIRC it was 2.25" diameter or so and atleast 12" long. We ran it on a 16" H&R .44 mag with big heavy 300 grain bullets being pushed by trailboss and literally you heard the hammer drop and the bullet impact. I always thought that was most fun setup we had out of the 40-60 cans that came and went through that shop.

I'm gonna get my Dad to grab the chrony for me when I meet the family in town for dinner later. Chrony results in 2-3 days.....

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John A.
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Re: Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by John A. » Mon Sep 03, 2018 7:13 pm

Here's some things that may cause this. They all point back to the bullets contacting either baffle(s) or the endcap.

1. Thread and bore on one of those barrels may not be perfectly straight. It's not uncommon for bores to not be straight through the barrel from end to end. For that matter, they often wander like a snake or a winding river. This is especially more common with longer barrels

2. The shoulder of the barrel may not be perfectly straight on the barrel that is having problems.

* Don't use crush washers

3. Thread adapters can also cause the suppressor to be canted. It's called STACKING TOLERANCES. If one part is on one end of spec and the adapter on the other end of spec, they both could be within spec individually, but when used together, well....

4. Install the can and put an alignment rod down the barrel. Look to see if the rod is canted in relation to the suppressor bore. If it is, I bet if you take the endcap off and look at it with the baffles installed, you'll find it pretty quick.

5. Clipping.

This can cause bullets to move around no different than a big gust of wind. That may be what's causing the bullets to contact something.

But if the suppressor shots well with one combination and it doesn't the other, what does that tell you? Something about that combination ain't right. Which is why I am concentrating more on misalignment than anything else.
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dellet
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Re: Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by dellet » Mon Sep 03, 2018 11:15 pm

Add to the list from John A, extrememly low velocity and a powder that does funny things with low density loads. Not uncommon for that powder to have velocity swings of 100 fps. Your estimate of low 800, high 700 is correct in the 10”barrel. No good reason to be that slow and plenty reason not to. Sticking a bullet in the barrel is no fun. Start high and work down to a speed you want.

For what it’s worth, 12.5 grains CFE in an 18” barrel is right at 1100 fps. with that bullet.

The bullet holes for the AR unsuppressed, look like the bullet has a wobble.if you have any kind of muzzle device, pull it down the list the barrel. It is just as likely that it was the angle they hit the backing, but it’s somethig I would consider.
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Re: Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by MountainmanID » Tue Sep 04, 2018 10:12 pm

dellet wrote:Add to the list from John A, extrememly low velocity and a powder that does funny things with low density loads. Not uncommon for that powder to have velocity swings of 100 fps. Your estimate of low 800, high 700 is correct in the 10”barrel. No good reason to be that slow and plenty reason not to. Sticking a bullet in the barrel is no fun. Start high and work down to a speed you want.

For what it’s worth, 12.5 grains CFE in an 18” barrel is right at 1100 fps. with that bullet.

The bullet holes for the AR unsuppressed, look like the bullet has a wobble.if you have any kind of muzzle device, pull it down the list the barrel. It is just as likely that it was the angle they hit the backing, but it’s somethig I would consider.

Velocity swings were very apparent today shooting the load through the RARR @125yds. I'd get a 3 shot 1.5" group, then a 6" 5 shot group with 1 or 2 low flyers.

I might try "unclipping" the 6061 baffles with JB weld. I put the can back together with the least aggressive clip closest to the muzzle and the most aggressive clipped one at the end of the can. Seemed to improve some accuracy. I'm thinking a 3/8" dowel wrapped in wax paper through the baffle and then build up a tiny shoulder from the face of the cone where the bullet enters. This will make all the baffles have the same-ish profile where the bullet enters regardless of where the baffle is clocked and should reduce internal turbulence (which I thought was a good thing to slow down gas).

EDIT: Shot it today for the first time wet, wow what a difference on the first 3-5 shots. First shot pop was nearly non-existent. Definitely the way I'll carry it hunting, if it's early season and above freezing anyway. Not sure what frozen water would do inside a can.....

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Re: Form 1 can doing strange things.....180 Rain Wedge CFEBLK

Post by dellet » Tue Sep 04, 2018 11:45 pm

I’m not known for sugar coating things, so here goes.

In all honesty, you have set yourself up for failure, and chasing your tail in a never ending circle.

You have a suppressor of questionable manufacture. Give it a chance before you start modifying it.

You have a bullet that any one who has tried it, needed a fair amount of load development to get reasonable results. It will work well enough in the bolt action, but might be tougher in the AR. It’s not an easy bullet to work with if you want MOA groups.

You chose a powder that in all honesty is crap for reduced loads. There is just no other way to put it, it’s your weakest link.

Get a decent bullet and powder combination to make sure your suppressor is working like it should.

Then if you want to play with the Rainier bullet, get a different powder.

Then if you want to work with CFE, get a bullet that you can get some compression on the powder.

Some of the best learning comes from working problems out on your own, but the most reliable thing in your list of possible issues, is your suppressor. The mounts may be an issue, your groups tightening up with the Ruger, indicate the suppressor itself is probably ok.

Get an MOA load with you bolt action without the suppressor, then mount the can and see what happens. Until then you’re just asking for frustration.
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