Too much bump?

[gunsandgunsmithing]

It might be interesting to make three bump gauges with different dimeter holes just because no-one’s ever done it. . Measure bump at the bottom, middle and top of the shoulder. Would you get different numbers? Are the bump gauges arbitrarily made to reference at mid- length of the shoulder? I really don’t care about any of this, I just have an interest in details. I adjusted my die by measuring and averaging 10 fired cases and that’s what I go with (0.002” bump). Bolt closure method sounds very good, but I don’t want to take my bolt apart to do it.

Lots of folks have what many call a "bbl gizzy", made from the bbl cutoff, with the same reamer that cut the chamber. The reamer is just run in deep enough to form most of the shoulder. It can then be used like a comparator but is specific to your chamber. IMO, it doesn't get much better than that. It can also be used to verify neck clearance and seating depth. Simple and easy to use tool that is quite handy and accurate. As you can imagine, it does away with datum issues etc. Lots of smiths used to provide them to customers, often as part of the chamber job.

 

[BoydAllen]

Lots of folks have what many call a "bbl gizzy", made from the bbl cutoff, with the same reamer that cut the chamber. The reamer is just run in deep enough to form most of the shoulder. It can then be used like a comparator but is specific to your chamber. IMO, it doesn't get much better than that. It can also be used to verify neck clearance and seating depth. Simple and easy to use tool that is quite handy and accurate. As you can imagine, it does away with datum issues etc. Lots of smiths used to provide them to customers, often as part of the chamber job.

With any barrel job, I always ask for a "gizzy". IMO they are the best tool for several jobs, not just measuring bump.

 

[L.Sherm]

With any barrel job, I always ask for a "gizzy". IMO they are the best tool for several jobs, not just measuring bump.

There easy to find the lands on a brand new unfired barrel also.

 

[Rocketvapor]

Takes a little more time but as fired has a little extra bolt lift.
(Savage 22N) so I size feeling for a tiny bit of bump with a body only die and fit check a few in the actual chamber.
For a match all sized are fit check.

 

[kd4avp]

Lots of folks have what many call a "bbl gizzy", made from the bbl cutoff, with the same reamer that cut the chamber. The reamer is just run in deep enough to form most of the shoulder. It can then be used like a comparator but is specific to your chamber. IMO, it doesn't get much better than that. It can also be used to verify neck clearance and seating depth. Simple and easy to use tool that is quite handy and accurate. As you can imagine, it does away with datum issues etc. Lots of smiths used to provide them to customers, often as part of the chamber job.

Got my first "gizzy" on a recent 22BR build. My smithy used a cut off portion of the barrel to make it. VERY handy tool to have on hand. Sure makes setting the die up easier. Getting very consistent sizing numbers using this method. Keep it in the same box as the Wilson bullet seater so I always know where it is.

 

[JFrank]

There easy to find the lands on a brand new unfired barrel also.

Barrel off touch point is pretty simple way of documenting the case or bullet stick point or touch point.
Speedy has a video if anyone is interested .

 

[JFrank]

You could just use different bushings in the Hornady kit if you wanted.

I use a 30 cal comparator bushing for 6 bra case sizing without any issues.

 

[Rocketvapor]

For 22 Nosler I took an extra 30 cal comparator bushing and reamed it
until I got an acceptable reading (1.448" ) with the Go Gage (1.450").
I get the same with a 7.62x39 steel case belled.

Aluminum Black for Identification.


I shoot a 22N ar-15 with a little more bump than the wife's 22N Savage.
Set the Savage headspace to TIGHT (by about 0.001-0.002") with the Go-Gage. Nosler 22N brass and factory ammo is SHORT.
I can size for both with the same setting.

 

[JMayo]

Not to high jack the thread, but tangentially related... I've been measuring my fired Lapua brass for my 260 Rem I've been working with and they seem to vary by 2 or 3 thou. If one were to bump 2 thou during resizing, do you set the die to bump 2 though based on the longest fired case or shortest fired case?

FWIW I set it based on the shortest case this last time. It's also a hunting rig so I might be splitting hairs for the intended purpose but enjoy trying to make it shoot the smallest groups possible.

I try to cover all the ranges of my brass. Yep some are bumped half a thou + too much.

 

[6MMsteve]

To clarify:
I gave it .002 headspace when I installed the barrel.
Shoulder measurement is post firing vs sized.

don't never try to gain by head spacing long.... you will have serious issues...always try to headspace as the gauge allows... it will be lots better and brass will last much longer...I would re headspace and start over

 

[Texas Solo]

Texas solo you had this question before. You should figure out how to measure shoulder bump. The way .007 will cause brass head separation in a short number

How much bump is safe?

My bolt closure is tight, even with factory Fed GMM 168. I sized and trimmed new Hornady brass and set the seating depth at -.005" off the lands. It's also tight. Next I bumped the shoulder .002" and it's only slightly better, so I think I found the issue. Question is how much bump is...

forum.accurateshooter.com

That issue was with 308, not 6 Dasher

 

[L.Sherm]

Barrel off touch point is pretty simple way of documenting the case or bullet stick point or touch point.
Speedy has a video if anyone is interested .

Alex's method is the way I do bump and find touch, I have used a gizzy to I have some for some of my guns.

 

[Rob01]

What is a “gizzy”?

 

[memilanuk]

What is a “gizzy”?

It's where a gunsmith takes the cut-off stub from a barrel blank, runs the chamber reamer into it, and sends it back to the customer with the gun/barrel. It should (in theory) give an exact replica of the actual chamber to test case sizing and/or bullet seating on... at least up until the point that the throat starts to move in the real barrel.

 

[Rob01]

Interesting but after some rounds pretty useless too. First I heard of that in over 30 years in precision rifles.

 

[memilanuk]

Interesting but after some rounds pretty useless too. First I heard of that in over 30 years in precision rifles.

That was always my take on them as well. But that'll get you roasted by the BR folks

I'm becoming more of a fan of the L.E. Wilson case gauge micrometer... I've kind of toyed with the idea of finding someone to make me a full-on case gauge from my chamber reamer, so it'd be an 'exact' fit. Not entirely sure that I'd actually gain anything from it over using the stock case gauge for common calibers. I guess if someone has an extra special super secret custom-dimensioned chamber reamer maybe they'd see a benefit... maybe.

 

[JFrank]

With any barrel job, I always ask for a "gizzy". IMO they are the best tool for several jobs, not just measuring bump.

I assume this is an additional charge by the guy chambering the barrel ?

 

[Kracken McGraw]

I assume this is an additional charge by the guy chambering the barrel ?

Not if they like you.
I really guess it depends if they even consider doing it for their customers. The last smith I used didn’t do it.

 

[JFrank]

Not if they like you.
I really guess it depends if they even consider doing it for their customers. The last smith I used didn’t do it.

How many times have you had one made free ?

 

[Kracken McGraw]

How many times have you had one made free ?

Mike Bryant in Texas has done 2 for me in the past.