Forster 308 bump die

[jo191145]

Frank
Not quite what I said... or at least meant to say ;D
A die, shoulder or FL, will only bump the shoulders as much as you let it Proper set up is key.
Forget the generic instructions that come with it. They both/all need to be set to your chamber.
No two chambers,dies,shellholders are alike.

What I meant to say is "some" necksizing fans let thier brass get overally long in the headspace department before resorting to the dreaded FL die. This now requires a larger bump to get back to chamber dimensions.

My personal parameters are simple. If I can feel my brass while chambering its to big. If my comparator says I'm bumping more than .002" on "slight resistance" brass I'm sizing too much (or) theres a bad mismatch between chamber and die.


I should concur with mikie.
A shoulder bump die should be just the ticket for most sane loads and brass thats never been horribly abused with pressure testing. ;D

Given those two parameters FL sizing should'nt be required for a very very long time. If ever.

[Nor Cal Mikie]

And, when you use a full length sizer die, you're working the body. That's what you avoid with a bushing bump die. All you're doing is sizing the neck and pushing the shoulder back a bit. Doesn't do anything with the body. .001 to .0015 should be enough for a bump.
By "not" using a full length sizer die, and just a bushing and shoulder bump, you let the body expand to the size of the chamber.
Every time that brass gets fired after it was full length resized, it expands back to the chamber size. That's where you're working the brass more than needed.
With a shoulder bump only, somewhere down the road you'll have to squeeze the body back down but not till it's needed. Keeps everything snug in the chamber. And you "can" bump the shoulder with a full length die but you're also working the body.

[frank1947]

Well I use all of them depending what I want to do, I have Forster Neck bump bushing , and redding S type bushing and redding FLS, example today after reloading winchester brass in 308 about 6 times I decided to check headspace with hornady headspace gauge, I couldnt remember what headspace was I went to saami.org and found it was min of 1.630 and max 1.640 my brass was .002 to .004 short so got the FLS out and sized to 1.633, this brass was done 6 times with the Forster bump neck bushing die good milage om that brass. YMMV, I had to do that

[GaCop]

Theoretically, you could properly set a full length sizing die with a go gauge then?

[Nor Cal Mikie]

I don't see why not but, the Go gauge is set at SAMMI specs and not all gauges are the same. At least that's what some of the guys have mentioned.
The advantage of the Savage barrel nut it you can set the head space on the "tighter side" so your brass doesn't grow as much with a looser chamber?
All mine are set on the snug side so my brass can't grow any more than I want them to. That's the advantage of being snug. Makes your brass last a lot longer. Bump "just enough" to close the bolt. And, if your die is set in the press to cam mover when it rests on the shell holder, you always go back to "that" setting and work from there. You never have to think about it. It's your starting point all the time. I don't bother to set to gauges anymore. I've got them but don't use them.
Full length resized case, set headspace to that and adjust from there. IMHO, snug it better. 15 to 20+ times fired, shoulder bumped and bushing neck sized. All cases still going strong. What ever works best for you is what you need to do. ;D

[jo191145]

Theoretically, you could properly set a full length sizing die with a go gauge then?

Good Lord thats a scary thought.
Inserting a solid steel guage into a die designed to constrict brass down to minimum specs does'nt sound wise ;D
While its possible the guage is of lesser body diameter specs than the FL die you won't know that until you try. The result would be either a jammed guage or faulty readings.

I'm in mikes camp. I adjust my Savs headspace to crush fit on virgin brass (if possible). I really have no use for Sammi specs.
Of course this means I usually need to adjust my shellholders to allow a shoulder bump/FL die to work.
I have one go guage....somewhere :D


Only way I know to set up a FL or shoulder bump correctly is by comparing headspace of fired brass to headspace of sized brass.
Optimally start with several pieces of fired brass thats beginning to show slight resistance to chambering. Slight resistance usually requires .002'' setback.
.001" to remove the resistance. .001" as a safety net for future variations in brass springback.
I do this by screwing in the FL die in very small increments once I'm in the ballpark.
Testing every adjustment in the rifle for "feel" and taking measurments.
Using small adjustments you'll feel that FL die begin to contact the shoulders.

With a FL die and a normal sloppy factory chamber using small adjustments you can notice the headspace measurements begin to grow as you adjust the die further down. This is because the FL die is constricting the body of the brass and pushing the shoulder forward.
This fact alone bodes well for the use of a bump only die in factory chambers

[Nor Cal Mikie]

And I might add, most of these remarks about adjusting headspace "tighter" than SAMMI specs are from trial and error. SAMMI specs are for factory chambers. Don't expect to be able to shoot factory loaded ammo. You may, but don't count on it.
What most of us are doing is trying to shorten the learning curve for other folks.
It's all a game that we're playing. Been there, tried that and it didn't work so we'll try something else till we find what we're looking for and what works best for "us". And as usual, YMMV. We're all in this to learn something. If you don't know, don't be afraid to ask. :)

[jo191145]

Well said mike

Its not something done lightly without prior thought and a full understanding of all the parameters that must be followed.

I'll throw out a few thoughts/warnings ;D

Never adjust a chamber greater than Sammi specs. Thats a given

If you want to use virgin brass for a go quage its much better to use quality brass. Lapua for instance has the specs set fairly tight to Sammi minimum.
I've seen some Remchester virgin headspace measurements .011" shorter than an already under Sammi spec chamber on one of my guns.
It was simply impossible to set headspace with that brass. Bottomed out the barrel stub on the bolthead long before.

Maintain at least .005" clearence between bolthead and barrel. You want that floating bolt head to do its job.

Obviously not everyones cup of tea. Some consider any deviation from Sammi specs blasphemy. Others are happy just following the established rules. Thats all fine.
What Mike and I are doing is minimizing or totally negating that first initial forming stretch of brass to fill the chamber.
Would I do it to a Stevens that fires a few shots at deer every year? I might but would'nt recommend it to most

[GaCop]

Good info and food for thought. To date I've always used the PT&G GO gauge and set the HS tight on the gauge to where one thickness of scotch tape (.002") wouldn't allow the bolt to close.

[Lee C.]

I should of said alot more than, that i have a forster bump die for every gun i have and they work for me. But i couldn't of said it any better than Mikie or jo191145 did. I've been doing it the same way as Mikie for some time now and it's been working out really good for me also.

[Nor Cal Mikie]

More to add. If you ever plan on selling one of you rifles set up on the "snug side", the guy that buys it had better know what he's getting into.
Like I mentioned before, don't expect it to chamber "factory loaded ammo". Just ain't gunna happen.
And all this info doesn't come over night. Got to "been there done that" to understand what's going on and how far you can go without running into problems. Just another part of the "learning curve". No short cuts involved.
And when you get to the point that you think you know "everything", it's time to take up basket weaving. ;D
I've pounded open a few bolts and popped a few primers and I don't want to go back there.

[mytwo60]

Very good info you guys. So here is my question.

Which is more accurate?

1/ Bump with no body size or FL bump with sizing the body?

[Nor Cal Mikie]

My guess is shoulder bump and bushing neck size. By not full length sizing the body, it can expand to the inside of the chamber.
By full length sizing, the case has to expand back to the chamber size after it has been squeezed down by full length resizing. To me, that's working the brass more than needed.
On a "custom" chamber, it might be a different story. Again, whatever you feel comfortable with and what works best for you is what you need to go with.
We all have different opinions and ideas.
Some of the BR Comp shooters will full length resize every time but I'am betting they're working with custom sized chambers while others will bump and squeeze.
Depends on who you ask. We all get stuck in out own little groove and are sometimes hard to change till someone else shows us the "error of our ways". ;D
If the fired brass will go back in the chamber with out forcing the bolt closed, size the neck and reload the case. When it starts getting snug on bolt closing, bump the shoulder.(no more than needed ) If it's still snug, size the body with a body "only" die or full length if that's all you have. Again, what works for me may not work for you. Remember, it's all a game so play till you come out winners. ;D

[jo191145]

Mytwo60
What Mike said +1
As in most things accuracy related theres to many variables to give a definitive answer.
I shoulder bumped since 2004 with very good results with a home made Redding "neckbumper" as I refer to it in a Sav VLP 204 Ruger.
I thought it worked so well I made others for 308W and 6BR cartridges I was using at the time.

Personally I have seen an improvement in accuracy and consistency since just going FL. That means absolutely nothing to anyone else and they're guns What works for me........
Actually I've found it to be what works for everyone else never ever works for me ;D
The Redding S series is all I use. Any standard(non bushing) die works the neck too much for my liking. I try to keep my annealing to a minimum if possible. I also personally abhor expander balls and lube in my necks. Quite sure I've been beat at the bench by someone who does'nt tho ;D
I'm sure a custom FL would be better but that stuff just ain't in the budget right now.

I don't think working the body of the brass is that damaging. At least not for me. Headspace is where the real problems arise.
Once that firing pin falls it pushes the case forward to the shoulders. Powder ignites, pressure forces the brass to expand and grip the chamber.
If headspace is excessive the only part of the case that can stretch is near the web. A very small area of brass takes all the stretching in comparison to diametrical (if thats a word)stretch. Thinning and case head seperation are the result.

I could list pros and cons to each method. Theories and assumptions mostly.
Mike said it better, whatever you feel comfortable with and works better for you.

[Nor Cal Mikie]

Funny thing about headspace is it can lead you in the wrong direction. Case in point: Case too short, gets pushed forward in the chamber to the shoulder area, primer won't ignite so you blame it on the primer. Throw out a batch of "good" primers that you think are junk and try another brand that's "better"? (just had one happen yesterday) All the other 40 rounds fired OK. Or, you find that the primer wasn't seated all the way down like the rest of the batch. :-[
You still condemned that brand of primers. Same with powder. Work it till you can't get anymore out of it. So and so says this is a better powder so I'll go with that. You never found out the true potential of the first brand. Too busy jumping around. ::)
Same with resizing your brass. If it feels good to you, do it.
If someone else does it a different way and you like the results, go for it and see how it works for you. Never stop learning. If you stop learning, you're not doing anything. ;D