Load development with suppressor

crapshoot

crapshoot

Well-known member
I have been doing some load development with a 20" 300wm and my .338 can.
What I am noticing is a first round POI shift along with increased velocity.
Anyone else notice this and is there a cure?
Pictured are 2 groups, same load. The only differences are seating depths.
The flyer is always the first round. Black aiming point is about 3/4-1 inch.

No I haven't tried it with the can off as I never intend to shoot it that way.







 
None of mine have done that, and the only way you're going to know is to take it off and shoot a group or two.
 
This may or may not help but before a hunting session or range trip I pull a completely dry/virgin (never had solvent or oil on it) bore snake through the barrel about 3 times. I found that some of my bores, upon sitting for several weeks or months, would develop a small amount of copper verdigris dust on the lands and the clean, dry bore snake treatment removed it. Prior to using the dry snake I would get a first round flier. If your guns are only sitting around a few days between shooting sessions it will likely not make any difference.
 
This gun had been shot a couple of times prior to this range trip. The loads were shot consecutively while still allowing time for barrel and can to cool between groups.

I was wondering if having an empty(void of hot gas) can could be causing the poi shift on the first round of a cold can string? Kind of the same principle as first round pop.
 
It's an encore barrel and having it cut down that short it's rather stout. It measures .815 behind the threads and the can is a Ti can.
Don't know how that would make a difference on a first round poi shift.
 
Originally Posted By: Terry LightleMy 223 sporter barrel had impact move quite a bit ,just dialed scope back in and went hunting.First trip watched one fall in the scope

Im not talking about poi differences between can on and can off.

I shoot with the can ALWAYS ON.
The first round in a string is always off from the rest of the group and it's always the first round fired when the can is cold.

I shot 4 rounds in the first string. The can was cold. First round went high while the other 3 grouped.

I let the barrel and can cool.

I fired a 5 round string and the first round impacted right and the rest grouped.

The only difference between strings was seating depth.

I noticed the same thing the last time I was at the range .
 
I get everything worked out before adding the suppressor. Powder charge, seating depth, stock,scope/mounts and what bags/bipod/rest works best. Than the suppressor almost always shoots better looking groups. You have to tune the load for minimum vertical dispersion.
 
Originally Posted By: crapshootI was wondering if having an empty(void of hot gas) can could be causing the poi shift on the first round of a cold can string? Kind of the same principle as first round pop.

This is correct. You have hit the nail right on the head. The first shot from a can is always slightly different. Maybe try shooting your can "wet"?

Hickok45 does an demonstration of this:

Notice how his first shot out of the can has a different sound that then 2 follow up shots.

Now how to address this issue I think goes to the Suppressor Manufacturer. I can ask a friend of mine, who owns a suppressor company, but he will likely say that the problem is from the suppressor design.

Good luck.
 
Originally Posted By: NevadaZielmeisterOriginally Posted By: crapshootI was wondering if having an empty(void of hot gas) can could be causing the poi shift on the first round of a cold can string? Kind of the same principle as first round pop.

This is correct. You have hit the nail right on the head. The first shot from a can is always slightly different. Maybe try shooting your can "wet"?

Hickok45 does an demonstration of this:

Notice how his first shot out of the can has a different sound that then 2 follow up shots.

Now how to address this issue I think goes to the Suppressor Manufacturer. I can ask a friend of mine, who owns a suppressor company, but he will likely say that the problem is from the suppressor design.

Good luck.

Is your friends company in Carson City?
 
Crapshoot, what your referring to is called cold bore shift, some rifles exhibit it, some don't. Some can be cured by bedding and or proper torqued action screws.

I'm good friends with the manufacturer in Carson City and have most all the models made, PM me if you need some help.
 
Originally Posted By: crapshootOriginally Posted By: NevadaZielmeisterOriginally Posted By: crapshootI was wondering if having an empty(void of hot gas) can could be causing the poi shift on the first round of a cold can string? Kind of the same principle as first round pop.

This is correct. You have hit the nail right on the head. The first shot from a can is always slightly different. Maybe try shooting your can "wet"?

Hickok45 does an demonstration of this:

Notice how his first shot out of the can has a different sound that then 2 follow up shots.

Now how to address this issue I think goes to the Suppressor Manufacturer. I can ask a friend of mine, who owns a suppressor company, but he will likely say that the problem is from the suppressor design.

Good luck.

Is your friends company in Carson City?


He was, but just moved closer to his home here in Reno. He hasn't updated his website I see. I will tell him.

The best way to deal with this is with a log book to note that first round cold bore/suppressor shot. Keep that in your mind when you take the first shot. Not easy, I know, especially with multiple tangos.
 


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