FL sizing belted magnum cases

[Ahsan Ahmed]

I would much appreciate some insight/directions regarding an issue - probably due to my lack of adequate experience .....

For the first time, tried to resize a few 300WM Hornady 1F cases fired in the same rifle (Sako S20). Prior to resizing, measure via RCBS mic indicated three thou over zero. Admittedly, I never took any initial reading of those factory rounds.

Anyway, I attempted to bump the shoulders back two thou. The die was screwed into the press barely touching the shell holder and yet the reading was a negative increase of 9 thou. So I backed out the die roughly about a quarter and still the readings were in the .006-.007 range.

Moreover, I cross-checked my measurements using Hornady headspace comparator before/after resizing - got similar results.

Haven't yet determined if the brass would chamber seamlessly in the concerned rifle. The brass does sit flush in a headspace gauge. Nonetheless, the headspace is certainly too excessive in those resized brass samples.

Hornady custom grade FL die was paired with Hornady #5 shell holder.

I reload for five other (standard) cartridges and haven't experienced such issue. Have I overlooked and/or missing something in the process?

Edited to add: I just realized that I forgot to switch out the Hornady headspace comparator bushing and use the correct one (for 300WM). Had been using the one installed for 3006 all this time. But still doesn't explain the reading on that RCBS mic? The mic is the correct one though for 300WM.

Some relevant images .....

 

[Potashminer]

I might be too "old school" to be of any assistance - I do not own many of the things that you are using. Your objective is to have the brass re-sized to chamber in your rifle - not sure I understand why it is important to chamber into a gizmo, or what something else reads about it. Your brass chambers into your rifle or it does not - does not matter what the other tooling says about it. A "normal" die has 7/8" x 14 tpi threads - 14 tpi means one full turn is 1/14 of an inch - .0714". If it is important to you to have 0.002" "bump" then that is about 1/36 of a turn of the die. Can't say it is not possible - you are going to do that if you want to claim a certain "bump" with those dies. So, I would run a brass all the way up in the press - screw down your die until you feel contact - back off on the press handle and turn in the die about 1/36 of a turn - try sizing a case and see if it will chamber in your rifle. Load up a bunch and shoot several 5 shot groups - see if your average group size improved, stayed the same or got worse.

By working with a 300 WM, you added in the belt and belt recess - so headspace on a belted magnum is measured from closed bolt face to where the front edge of belt rim contacts the seat in the chamber - is not about clearance or contact with the case shoulder - although you are describing as if you want to size the 300 WM to headspace on the shoulder, not on the belt - and that can be done - just like for most other rimmed or belted cases that have an adequate shoulder to stop the firing pin push. You're not likely to do so with a 300 H&H, but I think it should work fine on a 300 Win Mag, or even a 300 Weatherby Mag.

 

[Ahsan Ahmed]

I might be too "old school" to be of any assistance - I do not own many of the things that you are using. Your objective is to have the brass re-sized to chamber in your rifle - not sure I understand why it is important to chamber into a gizmo, or what something else reads about it. Your brass chambers into your rifle or it does not - does not matter what the other tooling says about it. A "normal" die has 7/8" x 14 tpi threads - 14 tpi means one full turn is 1/14 of an inch - .0714". If it is important to you to have 0.002" "bump" then that is about 1/36 of a turn of the die. Can't say it is not possible - you are going to do that if you want to claim a certain "bump" with those dies. So, I would run a brass all the way up in the press - screw down your die until you feel contact - back off on the press handle and turn in the die about 1/36 of a turn - try sizing a case and see if it will chamber in your rifle. Load up a bunch and shoot several 5 shot groups - see if your average group size improved, stayed the same or got worse.

By working with a 300 WM, you added in the belt and belt recess - so headspace on a belted magnum is measured from closed bolt face to where the front edge of belt rim contacts the seat in the chamber - is not about clearance or contact with the case shoulder - although you are describing as if you want to size the 300 WM to headspace on the shoulder, not on the belt - and that can be done - just like for most other rimmed or belted cases that have an adequate shoulder to stop the firing pin push. You're not likely to do so with a 300 H&H, but I think it should work fine on a 300 Win Mag, or even a 300 Weatherby Mag.

Thanks for the input.

I'm trying to headspace on the shoulder. Will try your suggestion as well and see what reading I get. The Hornady headspace gauge tells me the bolt will very likely close smoothly on that brass (don't have the rifle with me right now for immediate validation). Still, I would like to determine correct headspace for that rifle.

 

[Potashminer]

It is possible / probable that we are getting words mixed-up - I think "head space" is a technical term used by SAAMI and others - maybe "end play" or something is what you and I mean. Various head space gauges made by Clymer, Manson, etc. will be using SAAMI dimensions from bolt face to front edge of belt - and make no reference to case shoulder at all - although SAAMI drawings show what they are supposed to be. My JGS brand GO gauge for belted magnums says .2200" - which is SAAMI minimum dimension for "headspace" when cutting a new chamber. The JGS brand NOGO gauge reads .2240" - so a rifle maker will have about 0.0040" to hit to be "as new" - is typical that SAAMI defines Maximum headspace at circa 0.0100" longer than Minimum - so 10 thousands longer than a GO gauge - and is not the same across all cartridges that they set standards for. I have not been able to find where SAAMI defines a NOGO gauge - it may not be in their standards? You are trying to be within 0.002" for your shoulder - that I know of, that is a much tighter standard than SAAMI asks for. I have no idea what standards those tools that you have are made to.

The various gauging and SAAMI specs are only important if you are making a rifle to use factory ammo, or using factory ammo, or re-loading for someone else. Is a particular 9.3x57 here - that rifle was put together by me - I do not recall ever seeing 9.3x57 ammo for sale, so whatever it sees will be loaded by me. I do not really care if it is to SAAMI spec or not - my hand loads will not be used by anyone else. If I turn the die out a barely discernible amount, the bolt will not close on those rounds - when the die is set, the bolt does close - those brass fit that chamber. Is yet to be played with to see if more sizing will make better groups or not - I do not think it likely, since the 285 grain bullets will be half a bullet diameter out of the case mouth before they hit the rifling - a lot more going on with that one, than just the brass sizing.

 

[Hitzy]

Neck size, it will headspace off the shoulder then.

 

[stubblejumper]

I adjust my FL die, so that the cases just chamber without resistance. I don't get too hung up on the numbers.

 

[Snider shooter]

I adjust my FL die, so that the cases just chamber without resistance. I don't get too hung up on the numbers.

What I do. I don’t have or use gadgets. Rifle chamber is your gauge.

 

[boxhitch]

Thats fine until the brass develops a bulge just above the belt, then a FL resizer is working the entire brass to the max to get the bulge out, IF the regular die can even address it.
Redding collet 'magnum' body die takes care of the bulge, works good in conjunction with a shoulder bump and neck re-size

 

[Big bore dinosaur]

^^^^this.
Squashes the belt back into the brass.
Careful not to slag the slip collet on the die, it will go over the belt and jam up into the side body. . .
I have the same issue on the bigger belted magnum, 378

Took 2 thoa. Off the top of the shell holder , inorder to get the case further into the F.L. die body of my rcbs dies. Pushing the belt back. Since they dont make a collet belt die. YET

 

[Ahsan Ahmed]

Thanks everyone for the kind advise.

This morning, I revisited the issue with a clear mind and a "new" batch of 1F brass. Switched out the Hornady shell holder with one from RCBS and readjusted the sizing die from scratch. I would still like to think that it wasn't the equipment but just me not being diligent last evening.

Got it down to about 0.002" what I had intended - the brass chambered smoothly.

Thats fine until the brass develops a bulge just above the belt, then a FL resizer is working the entire brass to the max to get the bulge out, IF the regular die can even address it.
Redding collet 'magnum' body die takes care of the bulge, works good in conjunction with a shoulder bump and neck re-size

I have a belted magnum resizing collet die (Reloading Technologies). Hopefully, there won't be a need for that till perhaps 3F.

Few images from the morning session ....

 

[Potashminer]

Belted magnum resizing collet die - if we are talking about a "lump" or "bulge" in front of the case belt - most "normal" Full Length resizing dies will not re-size that - I have a Larry Willis one. I shot and reloaded many hundreds times with my 338 Win Mag - factory shells and new brass - I am sure some was brass reloaded 5 or 6 times - I never needed it, but all was fired in the same rifle. But then I bought some previously fired 300 Weatherby brass - after Full Length sizing, not one would chamber into my rifle. Jiffy marker showed "hang-up" was on case body right in front of the belt - perhaps one or two millimeters of contact (less than 1/8"). I bought that Larry Willis sizing collet die - all those brass fit now - I conclude that arises about most when brass fired in one chamber, then resized to use in another chamber - I doubt that "bulge" will develop in your brass, if you keep firing that brass in your rifle. As far as I can tell, that collet die only does work on that smidgeon area ahead of the belt - does NOT resize or make contact anywhere else on the case.

I could not help but notice that you are using a Frankford Arsenal calliper to measure - maybe read up on what that is accurate to - most will be plus or minus 0.001" - in other words, maker says it is "accurate within one thousandth of an inch" - and you are trying to measure 0.002" - so you could be at 0.003" or 0.001" and the thing would still read to you that you are okay. Do not confuse the level of the accuracy of the tool, with the read-out ability that it might display - they are not the same. That has to do with what measurement and accuracy is about. A "call out" for 0.002" is not the same as for 0.0020" or for 0.00200".

 

[Dmay]

could not help but notice that you are using a Frankford Arsenal calliper to measure - maybe read up on what that is accurate to - most will be plus or minus 0.001" - in other words, maker says it is "accurate within one thousandth of an inch" - and you are trying to measure 0.002" - so you could be at 0.003" or 0.001" and the thing would still read to you that you are okay. Do not confuse the level of the accuracy of the tool, with the read-out ability that it might display - they are not the same. That has to do with what measurement and accuracy is about. A "call out" for 0.002" is not the same as for 0.0020" or for 0.00200".

Very good point I think....something easily overlooked....something that should be considered for sure.......

 

[Ahsan Ahmed]

I could not help but notice that you are using a Frankford Arsenal calliper to measure - maybe read up on what that is accurate to - most will be plus or minus 0.001" - in other words, maker says it is "accurate within one thousandth of an inch" - and you are trying to measure 0.002" - so you could be at 0.003" or 0.001" and the thing would still read to you that you are okay. Do not confuse the level of the accuracy of the tool, with the read-out ability that it might display - they are not the same. That has to do with what measurement and accuracy is about. A "call out" for 0.002" is not the same as for 0.0020" or for 0.00200".

True. The calipers and gauges (comparators) that I use are at best perhaps near-accurate. Not absolutely precise.

 

[dan belisle]

Neck size, it will headspace off the shoulder then.

Correct. Eventually you will have to bump the shoulders back, but in the meantime, it works. - dan

 

[cody182005]

TBH i shot and reloaded a lot of 300wm and 7rm and never used any special dies. Every now and then and i mean like maybe a half dozen times in over 1000 rounds you will get one that doesn’t chamber and honestly im not sure if thats just from picking up brass thats been fired in another rifle.

My take. bump your .002 and rock on. hunting ammo that i need to rely on ill test the sized brass in my chamber before i load. but it really doesn’t come up often for me anyways. factory brass the primer pockets usually loosen up after 1/2 dozen firings.