30 BR Bump

[Link]

Hi

Looks like I'm bumping my shoulder .003 after each firing to get a nice bolt closure. Is that normal? I'm using fed 205Ms and they look fine. However I am getting a little hard bolt lift after firing. Should I bump a little more?

Is there any reason to size the neck anymore that what the shank of the bullet seats in the neck? Depth wise.


thanks Link

 

[gunsandgunsmithing]

Hard bolt lift is not likely from lack of shoulder bump. It's more likely poor die to chamber relationship. In other words, the die isn't sizing the web enough. Bumping the shoulder more to achieve more web sizing is not the best way to do it. The br cases have about .010" per inch of case taper. The body of the case that can be sized is roughly 1" long, so to get .001" more sizing at the web, you'd need to push the shoulder back about .100" further. Obviously, this is not ideal...or even safe. It's more likely to be a tight chamber and a die that simply can't size it enough at the web area. Hot loads and tired brass can cause it too, but with h4198 and light bullets in a 30BR, you have to try pretty hard to get to that point of being too hot. If the brass has been fired in another chamber, you may see the same thing. Start with fresh brass and moderate loads and set the sizer to give about .002" bump. JMHO--Mike

 

[GSPV]

Adding to what Brother Mike said, if you are getting bolt click and such, it is most likely that the base of your case isn't being sized enough.

It's pretty common.

If you still have it after doing as Mike suggests, you might look into having the rear of your chamber polished out a tad. That makes the die smaller than the chamber which is what's required.

The flip side is to get a custom die that is smaller than current chamber. That'd probably be more expensive and not worthwhile unless you have your own reamer and will be doing multiple barrels with it.

 

[Link]

Maybe I should have added that I'm using a Redding Comp Body dye and just got some comp shell holders and I am using, the -.008 holder. I am also caming over per Redding instructions. 35 gr H 4198 115s a lil jam.

But like GSPV implied who knows what the chamber is?

I guess I will see how it all works after the next firing.

It seems like it is always something.!

thanks Guys

 

[treeman]

I would go along with gunsandgunsmithing that the die / chamber relationship is not optimal. polish the rear 1/3 of the chamber walls with 320 grit wet-o-dry maybe 20 or 30 revolutions with short in and out motion. this has solved that problem for me more than once. I aso think bumping the shoulder back .002" is plenty.

 

[Eddie Harren]

Send a case, that has been fired at least 3X in your chamber to Harrell's Precision and ask them to make you a die.
http://harrellsprec.com/index.php?action=show_detail&crn=207&rn=384

 

[chris30br]

Best thing i would is send 2 fired cases to Harrells and let them match up up a FL die. Problem fixed!

 

[chris30br]

Send a case, that has been fired at least 3X in your chamber to Harrell's Precision and ask them to make you a die.

Lol! We was typing the same thing at the same time!

 

[Link]

When you re chamber or re barrel is it time for a new Harrell's die?

Link

 

[Eddie Harren]

If you use a different reamer or gunsmith, yes.

 

[gunsandgunsmithing]

In my experience, there are lots of br based chambering reamers that are a tad on the small side. This is where the problem comes from. There are two ways of addressing it, either make the chamber bigger or the die smaller. Both work, but polishing the chamber doesn't cost much and the wait time is usually next to nothing. I started spec'ing reamers around off the shelf type s dies a few years ago and have never regretted it yet. You can go too big, but I also think we have gone a little crazy in making chambers as tight as possible...hence the problem you are having. FWIW--Mike

 

[GSPV]

If you use a different reamer or gunsmith, yes.

+1
That's how I make that decision. Is it my reamer and am going to cut multiple barrels with it? Yes=Custom Die. No=Polish Chamber.

No matter what, it's a plus to have the chamber polishing trick up your sleeve. Just MHO.

 

[butchlambert]

Another way to handle it is to take a full length die and cut about .050" off the bottom of it. Now put it into your lathe and open the other end where the shoulder starts a few thousandths. Now you have a tight based die that doesn't affect your shoulder bump. Learned this from Charles Huckaba(BR HALL of FAME). I have a reamer now that I had Dave Kiff make that is .003 smaller at the base and .002 at the body shoulder juncture. I make my own dies. Reamers do not always cut the same at the base. It can vary depending on your chambering setup.

 

[Jet]

Link

I had the exact same problem with my 30BR as you are having. I ordered a 3.5 small base die from Harrel's and the problem has been solved. Give them a call and they will help you out.

Jet

 

[gunsandgunsmithing]

I posted this on the brc board, thought some may find it interesting here. Here's a gauge that I make for this purpose. It's fast, accurate and easy. Notice the indicator stem is offset to not be affected by the primer. Just drop the case in, mouth first and set the indicator top on the base. The base simulates the chamber, and measures from the shoulder to base. It's basically a long barrel widget machined for the indicator top. I use dial type indicators but digital indicators are an option and make reading and zeroing more convenient. It works with either equally well.

 

[WyoWindage]

what do your sized case web measure?

 

[Link]

what do your sized case web measure?

.469 if I measured in the right place? Just above the grove.

I can't get it through my thick head how it can chamber nice and smooth but when I eject, the bolt lifts harder than I like.

The bolt doesn't click [ or maybe I don't know what the term click is ] it just lifts hard enough to really upset the rifle in battery.

Gentlemen - thanks for all the info.

 

[GSPV]

Is it hard all the way through the lift, or just at the top?

 

[WyoWindage]

I recently got a Redding body die for my 6br. I goes to about 0.470", not enough for your chamber probably. My M12 Savage also has a hard bolt lift, but I can also make it much better by setting the shoulder back a little more. I have been leaving it a crush fit for now, as the bolt lift isn't critical for what I do. Ron.

 

[Link]

Is it hard all the way through the lift, or just at the top?

Pretty much all the way or the last 3/4 as I remember it. I have resized all my brass so I don't have any to check.

Thanks