Can't get it to shoot.

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Re: Can't get it to shoot.

Postby Hoot » Tue Sep 05, 2017 4:59 am

jgilesg wrote:Hoot
Have you gotten away from the stab crimp or is the info for those that don't have one, or are you only using it in certain applications, or lastly, is it because it shortens brass life?
Thanks
JG


Not entirely but its not my go-to crimp. With what brass costs, I don't like scarring it up. Its not a cosmetic objection. Many of the scars do not iron out on the inside.

Image

Unless I carefully sort and bin my stab crimped brass for the next use, I wind up with differing degrees of drag on the next bullets I seat. Its hard enough getting consistent neck tension without adding another variable. For blammo ammo not loaded to the max, it is of no consequence, but that's not how I roll.

I do use a stab crimp on my 200gr XPB deer hunting rounds. They get loaded from virgin brass and stored from one season to the next. It took some testing to find the right amount of stab crimp that I don't have to worry about the bullet pulling, yet has the least amount of impact upon MOA groups. My experience has been that I get better accuracy from an effective taper crimp than with a stab crimp. If I were simply chasing the fastest velocity for the least charge, the stab crimp would get the call. I really don't like it at all on smooth sided bullets as it distorts them more than I would like. Case in point are the 230 FMJ's.

Image

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Re: Can't get it to shoot.

Postby Hoot » Tue Sep 05, 2017 5:06 am

powerhead357mag wrote:The barrel has just over 1k rounds through it. And before I crimp I'm already at .475 on the barnes rounds so I just barely bump the case to .474. that sound about right? I'd hate to think the tromix barrel is shot out at 1k rounds


I would mic a few of those Barnes bullets. That doesn't sound right. The other possibility could simply be thin walled brass. Were they by any chance Starline? The Starlines hold more water than the Hornady, leading me to believe they have slight thinner walls. That's not necessarily a bad thing as long as they are not thin where it counts. IE down by the web, where most case head separations occur.

Image
Courtesy Varmint Al

Thinner walls at the mouth necessitate recalibrating our approach for taper crimping measurements.

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Re: Can't get it to shoot.

Postby powerhead357mag » Tue Sep 05, 2017 8:49 am

Hoot wrote:
powerhead357mag wrote:The barrel has just over 1k rounds through it. And before I crimp I'm already at .475 on the barnes rounds so I just barely bump the case to .474. that sound about right? I'd hate to think the tromix barrel is shot out at 1k rounds


I would mic a few of those Barnes bullets. That doesn't sound right. The other possibility could simply be thin walled brass. Were they by any chance Starline? The Starlines hold more water than the Hornady, leading me to believe they have slight thinner walls. That's not necessarily a bad thing as long as they are not thin where it counts. IE down by the web, where most case head separations occur.

Image
Courtesy Varmint Al

Thinner walls at the mouth necessitate recalibrating our approach for taper crimping measurements.

Hoot


All the brass I've been using for precision work is once fired Hornady from my gun. I've tried the taper crimp and the Lee fcd
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Re: Can't get it to shoot.

Postby plant_one » Tue Sep 05, 2017 9:51 am

powerhead357mag wrote:The barrel has just over 1k rounds through it. And before I crimp I'm already at .475 on the barnes rounds so I just barely bump the case to .474. that sound about right? I'd hate to think the tromix barrel is shot out at 1k rounds


i almost wonder if you've got your seating die set to crimp - which you dont want to do with this caliber! if you're gonna crimp - do it separately with the taper crimp die thats part of the hornady die set

try resetting your die by the no-crimp adjustment method and see if that changes

Image




at 1k rounds a 450 bushmaster barrel - no matter the maker - should be just a small portion into its usable life. we're generally not pushing rounds super hard with these so we're not into barrel burner speeds, and while lil gun does burn a little on the hot side, unless you've been doing mag dumps with yours on a regular basis - i doubt the throat is showing much (if any) erosion yet.




what kind of solvents have you used when you cleaned the barrel so far?

you said the barrel used to be awesome for factory ammo (big ragged hole) and now shooting 5" groups. this along with your weird pressure signs and the round count is making me wonder - like al - if you've got some kind of buildup going on - either a weird carbon thing in the chamber, or copper deposited in the bore. in my expierence when a barrel suddenly changes how it acts - its usually some kind of buildup, and often copper. again i know you said you cleaned it, but to what degree and with what solvents.
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Re: Can't get it to shoot.

Postby Hoot » Tue Sep 05, 2017 10:26 am

plant_one wrote:
powerhead357mag wrote:The barrel has just over 1k rounds through it. And before I crimp I'm already at .475 on the barnes rounds so I just barely bump the case to .474. that sound about right? I'd hate to think the tromix barrel is shot out at 1k rounds


i almost wonder if you've got your seating die set to crimp...snip...


Good Catch! I didn't think of that one. :oops: Still recommend mic'ing a few of those Barnes.

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Re: Can't get it to shoot.

Postby plant_one » Tue Sep 05, 2017 11:20 am

thats the beautiful part about these forums - we dont all have to think about everything... its a team effort :)


2 heads are better than one and all that... and the more angles you can approach a problem from the better the result is.



i'm sure this is something relatively simple, we just gotta explore the box all the way to the corners
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Re: Can't get it to shoot.

Postby powerhead357mag » Tue Sep 05, 2017 11:47 am

plant_one wrote:
powerhead357mag wrote:The barrel has just over 1k rounds through it. And before I crimp I'm already at .475 on the barnes rounds so I just barely bump the case to .474. that sound about right? I'd hate to think the tromix barrel is shot out at 1k rounds


i almost wonder if you've got your seating die set to crimp - which you dont want to do with this caliber! if you're gonna crimp - do it separately with the taper crimp die thats part of the hornady die set

try resetting your die by the no-crimp adjustment method and see if that changes

Image




at 1k rounds a 450 bushmaster barrel - no matter the maker - should be just a small portion into its usable life. we're generally not pushing rounds super hard with these so we're not into barrel burner speeds, and while lil gun does burn a little on the hot side, unless you've been doing mag dumps with yours on a regular basis - i doubt the throat is showing much (if any) erosion yet.




what kind of solvents have you used when you cleaned the barrel so far?

you said the barrel used to be awesome for factory ammo (big ragged hole) and now shooting 5" groups. this along with your weird pressure signs and the round count is making me wonder - like al - if you've got some kind of buildup going on - either a weird carbon thing in the chamber, or copper deposited in the bore. in my expierence when a barrel suddenly changes how it acts - its usually some kind of buildup, and often copper. again i know you said you cleaned it, but to what degree and with what solvents.


Definitely not crimping with the seating die. Lol no mag dumps and I use sweets 7.62 solvent as with at my other firearms about every 100 or so rounds. Or after seeing significant copper fouling on my bore scope. Then a light coat of lubrasilk gun oil. Called tromix, they want the barrel and bolt face back to look at it so we will see what they determine.
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