Trim To, throat erosion, or book spec?

[ZenOhSix]

Howdy.

I have all my reloading equipment purchased and I am getting ready to start my first set of precision based case prep. I wanted some quick feedback on the best way for case size trimming. I have already decapped all my once-shot FGMM ammo that I was going to reload with.

The books publish Min/Max case sizes, as well as TRIM TO values. For example, Lyman 49th says 2.005. SAAMI says 1.995" to 2.015".

I have purchased a chamber gauge from Sinclair. It is the insert piece, whereas I trim down a .308 case and put this doohicky in a case and measure. I figure I could do that 5 or 10 times, and make sure I have the correct depth. Once this is known, I then can trim based off my actual chamber length - rather than book or SAAMI values. Yet, I haven't seen a concrete number to back off of. I have read anything from .010 to .020 (with many forum posts listing everything in-between the two reference points).

I figured I would ask here, but I was going to go ahead and measure my chamber and then subtract .010 - and cut every case to that value.

Last question - should I trim new brass or first load/fire then trim to spec? Same goes with load/fire vs. FL size then load fire? Again, my plan was to take all brass (new or fire formed) and put it through the entire process (FL size, trim .010 off of chamber length, uniform primers, clean/chamfer the primer holes, etc.)

Finally - after I do all the cutting/trimming - I was going to throw it in a wet tumbler for cleaning. After that, I was going to sort the brass by weight into bins (bin quantity of 80 for a match)

Any final words of wisdom here?

Thanks.
Mike

 

[Sniper338]

Id decap and clean brass first... dont want dirty brass in good dies..

you sound on the right track... you csn trim new brass or wait and do it after fired... i check mine every firing... just be consistsnt..

 

[ZenOhSix]

Id decap and clean brass first... dont want dirty brass in good dies..

you sound on the right track... you csn trim new brass or wait and do it after fired... i check mine every firing... just be consistsnt..

Right. I have a specific decapping die to separate from my dies. Since all my brass is decapped now, I was going to:

1) Uniform primer pockets (K&M Tool)
2) Chamfer/Deburr primer hole (K&M Tool)
3) Cut one case down so I can use the Sinclair Chamber Gauge
4) Wet tumble with SS media for 2/3 hours with pretty cleaning solution
5) Use my non-bushing Forster Bench Rest Full Length Sizer Die on all brass (FGMM & new Lapua)
6) Measure the chamber 10 times with the case/gauge; document. Subtract .010, Document; set Wilson trimmer to that case trim to length.
7) Trim all brass to that specific length; chamfer/debur necks as well
8) re-measure all brass; set aside any that is under the documented length in step #6/7 (i.e. stuff that was already too short and didn't get trimmed, if any)
9) Measure/Document Brass wall thickness by MFG; find average; subtract .002/3 or pick a specific wall thickness (i.e. .0125)
10) Use the K&M expander and expand the necks of each case.
11) Neck turn each piece to the documented value in step #9
12) Sort the brass by Manufacturer (Lapua vs. Federal from FGMM)
13) Sort the brass by weight; maybe .2 grain lots? Use bins, counting in amounts of 80, to be used for accuracy vs. fowling/steel target plinking.
14) Sort the accuracy lots (i.e. the normal average weighted lots) by concentricity for neck/shoulder. Create an additional sub-lot (a vs. b) for anything outside .001 to .003 at the shoulder and .010 to .015 on the neck; lot B will be shot for testing purposes to see if out of concentricity rounds cause for inaccuracy. If so - they will be used as fowlers or pulled.
15) Select appropriate neck bushing (based on final case wall thickness value) - and put each case back through the Redding Type S (with the neck bushing). Decap/Expander has been removed from the die.

At this point, all of my case prep has been completed. I will then move to bullet prep. I will do similar activities, sorting bullets by lots via the Bob Green Comparitor tool, MePlat trimmer, Whidden Bullet Pointer, etc.

After that is done, I will then move onwards to create OCW system loads, to find my accuracy nodes.

Ha! I think I have this down right.. Everything is just about setup -- I just need one or two people to review this and say.. "GO"

Thanks,
Mike

 

[CatShooter]

Howdy.

I have all my reloading equipment purchased and I am getting ready to start my first set of precision based case prep. I wanted some quick feedback on the best way for case size trimming. I have already decapped all my once-shot FGMM ammo that I was going to reload with.

The books publish Min/Max case sizes, as well as TRIM TO values. For example, Lyman 49th says 2.005. SAAMI says 1.995" to 2.015".

I have purchased a chamber gauge from Sinclair. It is the insert piece, whereas I trim down a .308 case and put this doohicky in a case and measure. I figure I could do that 5 or 10 times, and make sure I have the correct depth. Once this is known, I then can trim based off my actual chamber length - rather than book or SAAMI values. Yet, I haven't seen a concrete number to back off of. I have read anything from .010 to .020 (with many forum posts listing everything in-between the two reference points).

I figured I would ask here, but I was going to go ahead and measure my chamber and then subtract .010 - and cut every case to that value.

Last question - should I trim new brass or first load/fire then trim to spec? Same goes with load/fire vs. FL size then load fire? Again, my plan was to take all brass (new or fire formed) and put it through the entire process (FL size, trim .010 off of chamber length, uniform primers, clean/chamfer the primer holes, etc.)

Finally - after I do all the cutting/trimming - I was going to throw it in a wet tumbler for cleaning. After that, I was going to sort the brass by weight into bins (bin quantity of 80 for a match)

Any final words of wisdom here?

I have a specific decapping die to separate from my dies. Since all my brass is decapped now, I was going to:

1) Uniform primer pockets (K&M Tool)
2) Chamfer/Deburr primer hole (K&M Tool)
3) Cut one case down so I can use the Sinclair Chamber Gauge
4) Wet tumble with SS media for 2/3 hours with pretty cleaning solution
5) Use my non-bushing Forster Bench Rest Full Length Sizer Die on all brass (FGMM & new Lapua)
6) Measure the chamber 10 times with the case/gauge; document. Subtract .010, Document; set Wilson trimmer to that case trim to length.
7) Trim all brass to that specific length; chamfer/debur necks as well
8) re-measure all brass; set aside any that is under the documented length in step #6/7 (i.e. stuff that was already too short and didn't get trimmed, if any)
9) Measure/Document Brass wall thickness by MFG; find average; subtract .002/3 or pick a specific wall thickness (i.e. .0125)
10) Use the K&M expander and expand the necks of each case.
11) Neck turn each piece to the documented value in step #9
12) Sort the brass by Manufacturer (Lapua vs. Federal from FGMM)
13) Sort the brass by weight; maybe .2 grain lots? Use bins, counting in amounts of 80, to be used for accuracy vs. fowling/steel target plinking.
14) Sort the accuracy lots (i.e. the normal average weighted lots) by concentricity for neck/shoulder. Create an additional sub-lot (a vs. b) for anything outside .001 to .003 at the shoulder and .010 to .015 on the neck; lot B will be shot for testing purposes to see if out of concentricity rounds cause for inaccuracy. If so - they will be used as fowlers or pulled.
15) Select appropriate neck bushing (based on final case wall thickness value) - and put each case back through the Redding Type S (with the neck bushing). Decap/Expander has been removed from the die.

At this point, all of my case prep has been completed. I will then move to bullet prep. I will do similar activities, sorting bullets by lots via the Bob Green Comparitor tool, MePlat trimmer, Whidden Bullet Pointer, etc.

After that is done, I will then move onwards to create OCW system loads, to find my accuracy nodes.

Ha! I think I have this down right.. Everything is just about setup -- I just need one or two people to review this and say.. "GO"

Thanks,
Mike

Don't "GO".

God, my brain hurts from reading this. Chill out!!

First, it would help if you mentioned what rifle you are loading for.

Second, since you have the Sinclair "doohicky", why didn't you mention the chamber length when you asked the question.

Unless you have a custom chamber, cut with a "designer" reamer, you can't get that close to the end of the chamber with your cases. Find the shortests and trim the rest to the same length.

Always leave 0.020" or more chamber clearance, or you will never stop cleaning your rifle because the ash build up in the front of the chamber neck will be nearly impossible to remove, and you will spend much of your time fighting it (I have that tee-shirt)

And relax, you are starting this journey with too much trepedation (and OCD).

 

[ZenOhSix]

Don't "GO".

God, my brain hurts from reading this. Chill out!!

First, it would help if you mentioned what rifle you are loading for.

Second, since you have the Sinclair "doohicky", why didn't you mention the chamber length when you asked the question.

Unless you have a custom chamber, cut with a "designer" reamer, you can't get that close to the end of the chamber with your cases. Find the shortests and trim the rest to the same length.

Always leave 0.020" or more chamber clearance, or you will never stop cleaning your rifle because the ash build up in the front of the chamber neck will be nearly impossible to remove, and you will spend much of your time fighting it (I have that tee-shirt)

And relax, you are starting this journey with too much trepedation (and OCD).

Thanks for your feedback.

Last night was a difficult night when I wrote this, as I was attempting to divert my attention from my ailments and being sick (I am very ill, terminal, and had a negative reaction to a new tertiary based pain medicine; the medicine put me into Diabetic Ketoacidosis), and my excitement and energy came across a tad rough around the edges.

Unfortunately, I don't have the luxury to spend a lot of time learning by trial and error, or going through a journey as you had put it. I shotgunned into reloading very quickly, purchasing some advanced items, that otherwise I would have acquired later in my learning process. This, combined with trying to apply everything on the onset, created the sloppy post last night; my apologies.

[quote author=CatShooter]
First, it would help if you mentioned what rifle you are loading for.

Second, since you have the Sinclair "doohicky", why didn't you mention the chamber length when you asked the question.
[/quote]

I am new to precision shooting, and have found that mostly military snipers and law enforcement swat snipers are only familiar with my rifle, so I have stopped mentioning it on the forums. It is something special though! It is a TacOps X-Ray 51 chambered in the .308. Here is a review by the online magazine, Sniper Central of the rifle: Hands on Review: Tactical Operations X-Ray 51

It shoots extremely well, in which I have been able to shoot multiple .16X sized groups with commercial match Federal Gold Metal Match 168gr ammo; I am shooting via Prone position with a Harris BiPod and a small tactical sandbag or rear monopod.

Thank you for asking about it though, as I am quite excited for the rifle. With that being said, to get the guaranteed 1/4 MOA build accuracy, I have read that Mike Rescigno uses a custom reamer. That is all I know about it though, unfortunately. Since I picked this weapon up from an LAPD swat sniper 2nd hand, I don't have all the build details. Rather, I just have the shot logbook showing 296 rounds fired through the rifle.

Regarding why I didn't mention the "doohicky" in my original post, I actually did. I am sure it was just missed due to the spastic writing style. By the time I wrote my second post, I was vomiting and couldn't get my brain to think clearly to say "Sinclair Chamber Gauge"; so I called it the "doohicky". For clarification, as there could be other items that one may have thought of with my inappropriate naming of the equipment, I was speaking about the Sinclair Chamber Gauge insert that goes into a trimmed down case. Here was my original mention of it:

I have purchased a chamber gauge from Sinclair. It is the insert piece, whereas I trim down a .308 case and put this doohicky in a case and measure. I figure I could do that 5 or 10 times, and make sure I have the correct depth. Once this is known, I then can trim based off my actual chamber length - rather than book or SAAMI values. Yet, I haven't seen a concrete number to back off of. I have read anything from .010 to .020 (with many forum posts listing everything in-between the two reference points).

Thank you for the insight for the chamber ash and minimum additional length. I had not read that information before! To your point, I can take my fire-formed brass and find the shortest case and compare that to the measurement of the chamber with the Sinclair Chamber Gauge (assuming I could get a proper measurement), minus .020".

Once again, I apologize for throwing out incoherent questions and posts. I wasn't in the best state of mind, but was trying to maximize my down time into something positive (if you don't, life gets old very quickly as you are always in some dire state). I will take this into consideration in the future, and try to be more clear.

I also sincerely appreciate your wisdom regarding the trepidation of reloading. Many people (family and shooting friends) asked why I would even bother spending thousands of dollars to reload a non-bench rest rifle that shoots less than 1/4 MOA with commercial ammo. The answer is quite simple really; I spend a large majority of time sitting on the couch at home doing absolutely nothing. I figured this would give me something to do that was firearm related, while also helping improve my overall accuracy once I get to the range (trying for once a week). Something to do with a saying my father told me, "A body and mind in motion stays in motion, a body and mind in rest stays at rest".

Finally - here is a link to everything I had purchased for my reloading venture: My reloading shopping list. I know there are some redundancies in there, but any other wisdom you woudn't mind passing would be much appreciated!

Thank you again,
Mike Haun

 

['Freak]

Once you have your chamber’s actual length dimension from the Sinclair tool, go by it and fergits any book maximum and trim to lengths. New unfired brass might already be shorter than book specified trim to length and more than .020” shorter than your chamber’s actual length.

Unless turning necks and using a neck turning tool that ceases the cut once the case mouth contacts the mandrel, don’t trim to length until after the first firing. If new unfired case lengths are already more than .020” less than your chamber’s length and turning the necks requires that they all be the same length, then trim all to the length of the shortest piece.

‘Erosion’ is the lands being torched away in the leade area and gots nutin to do with trim length.