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Old June 16, 2015, 01:35 PM   #1
308Loader
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Case trim .308 Win

So I have got into the habit of trimming my .308 brass to 2.005 after each sizing. My question is, should I let them grow to max before trimming? What affect would it have on the accuracy. Would longer brass support the bullet better if I'm loading closer to the lands?
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Old June 16, 2015, 01:39 PM   #2
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What are you shooting it out of? If you are not an elite benchrester, you're not going to be able to see a difference.
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Old June 16, 2015, 01:44 PM   #3
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I am shooting rem 700P, 26 in bbl, mostly off bench or prone. This one is my range toy, accuracy is the goal.
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Old June 16, 2015, 05:31 PM   #4
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Nice, 700P is an accurate rifle for sure but it is not a bench rifle. BartB once posted that you may see 1/20th of an inch improvement if you keep all your brass at the exact same OAL.

I shoot a Savage Precision Carbine, my son a R700 MilSpec and we can't tell any difference regardless of if I'm using brass I trimmed or brass that all were under spec.
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Old June 16, 2015, 06:36 PM   #5
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My question is more to, 2.005" as trim. Is 2.006" to 2.014" (+1 trim -1 max) acceptable? Given that all cases are the same trim length. Any pro - con to length?
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Old June 17, 2015, 08:37 AM   #6
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I think so, that is how I do my lots now. I lock the calipers in at 2.015" and measure the batch, if any of them are long the entire batch gets trimmed down to 2.005".
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Old June 17, 2015, 09:15 AM   #7
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Any pro - con to length?
Only with the methods and techniques. I understand the resistance to change shared by reloaders. measuring the length of the case can/could be faster and trimming a case to length for a chamber a reloader does not have could result in longer cases.

I have a chamber that allows for cases that are longer from the mouth of the case to the case head by .016", I could trim to match 'trim to' case length but that would result in a case that does not cover my chamber. And, that is what I want, I want a case to cover all of the chamber.

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Old June 17, 2015, 08:05 PM   #8
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From what I've ben reading on this forum I seem to see a pattern in your answers guffey. It seems to be mostly about measuring ones particular chamber from bolt face to lands and everything in between. Would a chamber casting be a good way to measure all of it? Not to be sarcastic, but my calipers don't fit in my chamber. I Have a lot to learn yet, and I appreciate all the info this forum provides to new loaders like myself.
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Old June 17, 2015, 09:19 PM   #9
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I trim every loading. Everything the same length, everything consistant, everything same as last time I loaded. Get the same results each time to the range. anneal every 4th load. You want to be consistant every load. Same shoulder bump,same neck tension, same seating depth.You find a load that shoots great in your rifle-Keep loading that load exact every time. Just makes sense.

Now if Bart chimes in ( smart guy). he will talk about throat erosion, which I have no doubt is real. I have well over 3000 rounds down my match 308 rifle and to this day, still seat every load the same as I did 2 years ago and still get same results on target. If the day comes that my groups start to get out of control , a new barrel will be ordered. And then the game starts all over to find the perfect load.
I have 9 rifles now and I have one load for each of them. I do not mess with 2 or 3 different loads for each rifle. One load per rifle. Same bullet, trim length,primer,powder and seating depth.
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Old June 17, 2015, 10:27 PM   #10
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Quote:
It seems to be mostly about measuring ones particular chamber from bolt face to lands and everything in between. Would a chamber casting be a good way to measure all of it? Not to be sarcastic, but my calipers don't fit in my chamber
Thank you,

Quote:
my calipers don't fit in my chamber
I use the same type dial calipers as you, when determining the length of a 308 W chamber from the shoulder to the bolt face or the beginning of the chamber throat to the bolt face I form transfers, the transfers allow me to move the dimensions of the chamber to a comparator or gage.

Chamber casting? I do not find it necessary to case a chamber, again, I form cases, the 308 W chamber is shorter than the 30/06 chamber from the shoulder to the bolt face by .388". With .388" I can not miss.

I make chamber castings, there is a lot of work involved and different.

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Old June 18, 2015, 09:16 AM   #11
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Then there is changing the attitude of reloaders, there are modifications that can be made to adept tools for other purposes. That is not easy to talk about on a reloading forum, I am of the opinion reloaders are investors in companies that are manufacturers of reloading equipment.

There are at least three ways to determine the length of a chamber without a head space gage.

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Old June 18, 2015, 09:43 AM   #12
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0.01" of case neck isn't going to make any practical difference supporting the bullet.

The reason for trimming cases is to keep them from extending into the part of the bore where there is no clearance for the case to expand and release the bullet (which creates high, possibly dangerous pressure).

The only other reason to trim brass is for uniformity. And that only matters really matters when crimping.

If you are trimming after every firing, I think you are overdoing it.
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Old June 19, 2015, 12:21 AM   #13
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This is kind of a long winded story to get to a point...

I once saw a youtube video of a guy sporting custom thousand dollar rifles, checking the bores with an 800 dollar bore scope with video attachment, showing his Dillon reloading presses.

I was impressed until he took his handloads to the range, ran them through his thousand dollar rifles, and came back with 5 moa groups.... He was convinced he was a great hand loader and shooter, but I remain skeptical.

So if you are trimming every reload, and it's working for you, by all means stick with it. If you stop trimming every time I expect you won't see a difference with a 700P, but sometimes having a ritual for reloading does more for the trigger nut than anything else.

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Old June 19, 2015, 05:19 AM   #14
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Trimming everytime is probebly not a requierment, but it does keep everything the same from shot to shot. 44AMp- It has nothing to do with bullet hold or support. It has to do with each bullet being the same as the last. Does it make a difference- According to you-no, but then thats according to you. Each to there own I guess. I like to know when I dont hit the bullseye- It was operator error that caused it.

The top Bench shooters I talk to do it, they also anneal every round. They do this for a reason. They have found out IT does make a difference. I do not aspire to be a good shooter I want to be a great shooter, and that is why I do it.
I shoot about 300 to 500 rounds a week and continue to get better and better. I put my faith in what the top shooters do over what You and I and a few others think.
I became a member of this forum for 1 reason that has turned into 2 reasons. First was to learn from all the great members in here and second to help others with what I can. Through the years now my posts have changed from what I thought I knew to what I know now. I have now Had Bart on an occasion have people private e mail me for info and advice also. I take that as a very large compliment. In the end- I am here for the same reason you are-To learn and teach. I tell things that have taken me from a MOA shooter to a sub MOA shooter. While 70% of my shooting is 300 yards I still get out once a month and stretch it to 1000 to 1400 yards.
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Old June 19, 2015, 07:39 AM   #15
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Now if Bart chimes in ( smart guy). he will talk about throat erosion, which I have no doubt is real
Quote:
I have now Had Bart on an occasion have people private e mail me for info and advice also.
If you would get off of the "repeat after me" and refrain from 'siding' you could determine throat erosion with tools that were designed for other purposes. I have a tapper/inline/butt grinder. It is not a matter of making gages, it is about determining the distance to the lands, a reloader that has no clue what the distance was when the rifle was chambered is left with using a bore scope and or making a chamber cast.

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Last edited by F. Guffey; June 19, 2015 at 09:10 AM. Reason: change case to cast
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Old June 19, 2015, 12:08 PM   #16
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Guffy- I also said I have NO DOUBT it's true- However so far in 3000 plus rounds it has not made a difference on my accuracy that i get from the rifle.
I still seat to the same depth as I did when the rifle was new. I also do not worry nor care about throat erosion, as when the groups open up-I buy a new barrel. I buy one a year for my 6BR. I find one load that shoots great and that is what I shoot always. Barrels are a expendable item. I have never found a need for all the gauges you have. I have the Hornady gauge to measure my seating depth to the lands and that is all I need. I do not need to measure throat erosion- I buy a new barrel. Don't need 90% of the tools you have Guffy.
I load , I shoot, I load , I shoot, when things go South-I buy a new Barrel and go back to loading and shooting. You seem to have tool for everything- What has it gained you?. Answer-Nothing other than Money and the ability to measure a shot barrel. Heck I do that for free just by watching my groups.

Got well over 15,000 rounds down my 223-Still shooting the same bullet,same powder, same AOL I started with 5 years ago. Still pulling the same accuracy. Do I have throat erosion-Yes. Has it made a difference-NO.
With all your tools and stuff you do Guffy- Do you even have time to shoot any more?.
I bet you have a tool to measure everything.
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Old June 19, 2015, 12:28 PM   #17
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I'm sure Mr. Guffy has a lot of experience and much to offer, but I usually can only understand 25% of his posts (not total posts, but 25% of each post )...
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Old June 19, 2015, 12:39 PM   #18
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With all your tools and stuff you do Guffy- Do you even have time to shoot any more?.
I bet you have a tool to measure everything.
Back to the beginning, it has something to do with trimming case length. I am the only reloader that makes gages for determining the length of a chamber from the throat to the bolt face. It seems everyone else uses a reloading manual, again 'seems' they have 'trim to length' or maximum case length according to SAAMI.

Then there are design functions of tools used by reloaders. Most reloaders measure the length of a case from the end of the neck to the case head.

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Old June 19, 2015, 12:53 PM   #19
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I simply run my .308's through an RCBS trim die every time after sizing and I know they are consistent. One simple step for me and it seems to have the desired effect.
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Old June 19, 2015, 01:18 PM   #20
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Guffy- Case length is a given. Shoulder bump is what is important. Which again-You do not need a tool to determine
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Old June 19, 2015, 03:04 PM   #21
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Started out with a Rem. 700 LTR 308 20" HB, It's a smaller version of the 700P. I trim every reload to 2.010 keep the head space to .001 Shooting 168 gr.HPBT Sierra bullet over 40.5 gr. of IMR 4064 in a F/C or ADI Case both are thicker the most brass. Win & Rem. brass I would be 1. grain higher on my loads. I agree with 4runnerman on his case prep.
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Old June 19, 2015, 03:14 PM   #22
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Old Stoney, the trim die is the most accurate way to trim cases. Again, the 308 W form/trim die is my favorite forming die, next is the 243 W forming die.

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Old June 19, 2015, 03:31 PM   #23
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Quote:
So I have got into the habit of trimming my .308 brass to 2.005 after each sizing. My question is, should I let them grow to max before trimming?
I trim each time I size the brass. You either must measure each case and sort them out that way, or you just trim. I have a Gracey trimmer for 223, a Giraud trimmer http://www.giraudtool.com/prod02.htm for 30 caliber, and an RCBS Trim Pro for everything else. I can trim cases so quickly with the Gracey and Giraud, basically it is like sticking a pencil in a pencil sharpener, that measuring the stuff would be stupid.

If you are going to be selective about trimming, that is only trim once in a while, you must measure all cases and make no assumptions that just because all the cases you measured are under max, the rest of the cases will also be under max. This is not so in my experience. The odd ball long case pops up.


Quote:
What affect would it have on the accuracy.
Humans see patterns were none exist. Just search for threads about how Lee Crimp Dies supposedly improve accuracy. They don’t, shooters see improvements where none exist. I have shot mixed trim length brass and my regular trim all brass, some of which is not necessarily trimmed because it was a little short, and I can’t see a difference on paper.

Quote:
Would longer brass support the bullet better if I'm loading closer to the lands?
What over length case necks will do is cause overpressure conditions. The case neck will be pinched in the throat and you will blow primers. Happened to me decades ago. I just assumed once fired brass did not need trimming. I was wrong, once fired brass lengthens the most of any firing. My recommendation is to trim to minimum and keep that case mouth away from the rifling.
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Old June 19, 2015, 07:16 PM   #24
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My recommendation is to trim to minimum and keep that case mouth away from the rifling.
I choose to keep the neck of the case out of the throat and the bullet out of the rifling.

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Old June 20, 2015, 11:18 AM   #25
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F. Guffey, I'm with You
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