At what point ditch your belted cases?

[gilream]

I've been loading for 7MM Remington Magnum for years and it's the focus of my attention right now. It seems, and I can't say this with any rock-ribbed certainty, that accuracy starts to suffer after 3 or 4 loadings. Do you more experienced shooters with magnum rounds find this to be true? I don't exceed book loads, I monitor case length closely and trim when needed, I uniform primer pockets after each firing if needed. I realize that the case necks get work hardened and sometimes I while ejecting a case the last little arc of the bolt lift while ejecting takes a bit of a harder turn and results in a noticeable "click" before the case can be removed. Are any of these items a detriment to accuracy?

Is it neck tension because of the work hardening of the case neck? Does the internal case capacity change with repeated firings enough to make a difference?

I have always thought that accuracy was best with the first firing after the cases were fireformed.

Thanks for your ideas on this subject.

 

[BoydAllen]

A couple of questions...
Are you FL sizing? If so, what die are you using, and how much are you bumping your case shoulders? After a few firings, does the effort to seat a bullet change from what it was, or become less consistent? In my experience, if the feel of closing your bolt on a loaded round is inconsistent within a group (one noticeably tighter or looser than another , that alone will open groups.

 

[gilream]

I use Redding bushing neck dies, and I bump the shoulder using a Redding body die only when I start to feel a bit of resistance while closing the bolt. I bump the shoulder .002 short of the chamber dimension. I have right at two thousandths neck tension. That said, I have noticed that it takes more effort to seat the bullets at times.

I've often wondered whether to neck size first and then FL size the body or vice-versa.

 

[BoydAllen]

I think that you would get better results if you used the body die every time. Also, when you do, check the bump on all of your cases. It has been my experience that variance in brass hardness, even once fired, results in more than .002 variance in bump. I learned this recently when helping a friend with loading for a 7mmWSM and a .338 Laoua. He ended up buying one of those annealing machines that uses two torches, and pauses the case in by an adjustable amount while it is heated. That solved the problem, without making the necks too soft. The problem with your bump routine is that not all of the cases will get tight at the same rate, and you will end up with the tighter/looser situation that I referred to in my previous post.

 

[cmillard]

i am ditching belted mags all together. am going to the .300 wsm. the belt is just one more thing to worry about

 

[BoydAllen]

Let us know it that solves the problem.

 

[wapiti25]

+1 on annealing the brass. I would anneal every other reload, some competion shooters anneal every reload. A neck turn would not hurt if you do about a 80 percent clean-up even in standard neck dia chambers.

 

[bheadboy]

my experience with 300wm leads me to believe as stated above,two things, first you need to set the die to give 3-5/1000 set back, as the case headspaces on the belt. this is a nominal setback.

2nd the brass on cases of this powder capacity need heattreating after 3-4 rounds in my opinion to keep the brass soft enough to size consistantly

hold up you calipers and look at a .002 gap, it is nothing that a slight inconsistance in brass "bounce back" can not exceed when the brass hardens

also, howmuch are you working the neck, from fired to sized to seated, this also increase the work hardening of the brass in the neck if it is excessive.

Bob

 

[gilream]

The Winchester brass gets worked quite a bit. (It has much thinner necks than Norma brass) First time fired cases measure .3170 at the neck; I size them in a single pass using a .307 bushing for .3065"; the loaded round is .3086 for a neck tension of approximately .002".

I do not have an anealing machine and am reluctant to buy one (budget). Is it possible to anneal correctly with a single torch by twirling the case and using the welder's gel stuff that i've read about here?

 

[bheadboy]

The sized to loaded dimension change is not a problem the .010 fired to sized, is.

The only way toalter this is a chamber with a tighter neck, - espensive.

The alternate was tocare for the brass is to heat treat every firing, use battery driven elect drill tochuck the case, use one torch at neck/shoulder of case, as color turns stop.

the gel stuff works,

Bob

 

[bozo699]

gilream,
Changing to a beltless case won't fix your problems, as a matter of a fact they will follow you with the wsm, it is the loading technique your using. With larger cases and full house loads you have to bump the shoulder each time you reload, after the first firing with the new brass you will be head spacing off the shoulder and not the belt, there is way to much sizing to be done to headspace off the belt, probably three loadings and you will have to discard brass. there has been many records held in the past with belted magnums, unless the barrel is wore out I wouldn't change it until it is. The shoulder bump you have been doing is fine, .002 just needs done every time and as sloppy as your chamber is the brass is being worked so like Boyd said anneal your brass, there are some very good articals on here about annealing and if memory serves me Boyd Allen may have some good links on that very subject he probably would share with you. Also if you can find some RWS 7mm mag brass, besides from being the best it is much thicker so you won't work it so much ( With RWS the case fill is less so reduce loads and work bacK up ) There is a forum member on here that may be able to help you locate this brass, a very nice guy and easy to work with,...JayCutright. Don't despair the 7mmRM has been a wonderful round for many years and it's no where near through yet
Wayne.

 

[jonbearman]

What about the collett die the gun shop in florida sells in order to size all the way to the belt rather than falling short with a standard die.

 

[jonbearman]

The company to check out is :Innovative technologies in florida,he makes a collett die to get rid of the buldge at the edge of the belt into the body.His phone number:1-407-695-2685 Larry Willis

 

[bozo699]

Yes what Jon said, I have custom chambers and don't have a issue with sizing as a matter of a fact I have had to trim some off the shell holder just to get the shoulder to bump but in your case Larry's collet die for magnum cases may be the ticket and he is very easy to talk to, seems to be a real nice guy, I bought his digital head space gauge and really like it.
Wayne.

 

[hogan]

For best precision, a belted magnum ought be setup/chambered with minimum oal headspace, like any other rifle you expect premium accuracy from. The belted magnum needs to headspace on the case shoulder and to do so with only .001-.0005" to spare. Problem is the belt and go-gauge etc which otherwise would be reliable only functions from belt dimension. Set your headspace using an unfired factory case.t

Own an RCBS Precision Mic or Wilson Case Gauge? Have you compared virgin case dimension to fired case dimension? The Precision Mic uses oal to shoulder as its reference. I have seen .300win cases index far under the -0- mark on my PM and also owned a 7mm Rem mag PM. Only difference was the case body length, both use the #5 PM thimble.

If your chamber has substantial difference from unfired to 1x/2x fired dimension then that is your problem. If you have a factory barrel, probably not worth expense to set forward and rechamber or improve. Consult on the matter with Dave Kiff or a 1000yd benchrest gunsmith and consider their recommendations.

The standard magnums with .532 belt and .510 body have a lot to offer. If setup with shoulder headspacing, the extra material in case base actually offers more to the handloader in terms of safety and primer-pocket life than the belt-less magnums; or such is my theory. My experience with improving .338win mag chambers to .338/300, all headspaced to .0005" over minimum virgin brass dimension, has shown great accuracy/precision potential; at least with the hunting rifles I have improved.

 

[LongRanger]

Have not read in these comments about taking full advantage of the belted case and headspacing to .000/ zero. Then you have the belt aligning the case in the chamber at one end and the shoulder aligning the case at the other. Setting up the dies to more than zero headspace and ending up with some cases giving more resistanace to bolt drop than others is fussy work. Make them to what you determine is about .001 snug, or definitely making light contact, so they all are more apt to act the same when fired.

Frank B.

 

[gilream]

Some of these great comments have me thinking about headspace. Last year I re-barreled my 7 MM Remington Magnum. The work was done by a very reputable gunsmith here in Western NC that does work for several top competitive shooters in this area most notably Samuel Hall. Let me give you some measurements that I have taken and see if you guys think that there is something sloppy about my chamber. I have a headspace gauge from Stoney Point that attaches to my Mitutoyo electronic caliper and uses separate bushings to measure headspace for various calibers.

Cases that I have fired several times and even to the warm side measure 2.118
Virgin brass from Norma measures 2.1020
Virgin Brass from Winchester measures averages 2.099 (they tend to vary)

Is this 16 thousandths shoulder headspace difference inordinately large between the 2x fired case and the virgin case? Do I have a problem with headspace? Is that why my groups seem to open up after a couple of firings?

Please keep in mind that I do not anneal and the case necks get worked quite a bit using Winchester brass (loaded round at the neck is .3086). Norma brass is much better with the loaded round at the neck being .3129. The chamber's neck dimension is .3175

I am hoping that the issue is with my loading technique in that I have not been FL sizing each time and that I do not anneal my cases.

Thanks for your help.