Case trimming tolerances for 308...

[Big Caliber]

When trying to squeeze out more accuracy out of your 308 reloads, how much may the case "trim to" length vary before one sees a difference downrange, say at about 200yds.? I realize that all cases should be trimmed to the exact, same, length. But I'm not a machine and occasionally I crank out cases that are 2.010", plus or minus 0.001" to 0.002", thus producing a "spread" of 0.005". The cases are Lapua and bullets come from either Berger or Sierra, 175 grains. The powder is Varget or IMR4064 and primers are Fed210 match. I bought a Redding case trimmer w/ mic to replace my good ol' RCBS trimmer. I found in the past that lateral pressure on the crank while turning needs to be constant. But again, I'm no machine. So, is 1 or 2 thousandths either way acceptable.? Or should I continue to endeavor to persevere?

[68injunhed]

Get a Lee trim rig, mechanically blocked to trim to a certain length if it bothers you. I usually get less than .001 variance with mine. It sounds like a non-issue to me, that's plenty close enough for any but the most anal.

The single biggest key to accuracy, assuming the right charge of the right powder and consistent charging of said powder, is getting the bullet seated straight.

[btm_54]

Check out this tool. It works well and the results are repeatable.
http://www.sinclairintl.com/.aspx/pid=32925/Product/Sinclair_Chamber_Length_Gage

[MikeinGBWI]

Greetings.
This applies to my .308 loading as well as others.
I have a high dollar trimmer. On a whim, I decided to buy the Lee case trimmer setup since it was only a total of $11.00 for the two required assemblies. After I tried it for the first time, I was so impressed with the ease of use that I put the "better" trimmer into storage. I get trim lengths at +/- 0.0005 if done by hand and +/-0.001 if I use the cordless drill. The Lee system has proven to be a set and forget tool, although I do still spot check to make sure things are consistent. At $11.00 a setup, I have one for each caliber I load. There is adjust-ability build in if you desire a specific longer length then the tool is gaged for. The tool steel that the trimmer is made of will probably require replacement more often (for me, anyway), but it is a very economical way to trim. I recommend it if you are not necessarily in a hurry to do things and/or have budget constraints.

Shoot safe,
Mike - in GBWI

[jonbearman]

I dont think you have a problem other than your powder choice.H335 and blc-2 give supreme accuracy in the .308.Check your sierra loading manual.

[68injunhed]

Hey Mike, it's amazing how a tool as simple as that Lee trimmer works so well, isn't it?

[MikeinGBWI]

Hey Mike, it's amazing how a tool as simple as that Lee trimmer works so well, isn't it?


It sure is. I plan on keeping the expensive hulk of a trimmer as a backup. I only hope I can help prevent others from doing this backwards like I did. Don't get me wrong, the "traditional" trimmers are fine. I *used* to use one, but found the Lee to do everything I need, on the cheap, and with less setup time. Cheap enough that I have one Lee set up for each caliber I reload (currently 5) and I still am way under the cost of my Redding trimmer (sounds like I have the exact same one as Q.T. Hush).

As to the powder recommendations, I concur with jonbearman. I have been doing some testing with BLC-2 in my model 10 FCP-K and right at 44 grains I have seen groups in the sub .500 range (100 yards). The only thing I need to experiment further with is temperature based changes - to see if there is a difference from 50* days to 90* days. Now that old man winter has finally decided to leave me alone, the temp is starting to climb. We shall see if there is a need for a powder like Varget, or if the temp stability of BLC-2 is not as bad as some have stated. I do like that Varget fills the case a bit more, but I can't complain with the results I'm getting from BLC-2.

Shoot safe,
Mike -in GBWI

[Big Caliber]

Well, thank you all. I will look into the Lee setup. As for the powder, from what I've just read, I have no reason to change powders. For now, the 4064 gives me 3/4" groups at 200yds. 8)

[earl39]

As to the powder recommendations, I concur with jonbearman. I have been doing some testing with BLC-2 in my model 10 FCP-K and right at 44 grains I have seen groups in the sub .500 range (100 yards). The only thing I need to experiment further with is temperature based changes - to see if there is a difference from 50* days to 90* days. Now that old man winter has finally decided to leave me alone, the temp is starting to climb. We shall see if there is a need for a powder like Varget, or if the temp stability of BLC-2 is not as bad as some have stated. I do like that Varget fills the case a bit more, but I can't complain with the results I'm getting from BLC-2.

Shoot safe,
Mike -in GBWI
[/quote]

Mike i think you will find you will need to reduce your load just a hair when it gets hot. I am running blc-2 on the ragged edge in my F-tr rifle and have found that just 2-3 tenths reduction will keep everything running smooth when it gets hot outside. That load is worked up in 50-60 degrees and hot runs around 100 degrees after that i tend to wait till it cools off a bit. If you are not pushing your load hard you should have no problems with it.

Gary

[MikeinGBWI]

Mike i think you will find you will need to reduce your load just a hair when it gets hot. I am running blc-2 on the ragged edge in my F-tr rifle and have found that just 2-3 tenths reduction will keep everything running smooth when it gets hot outside. That load is worked up in 50-60 degrees and hot runs around 100 degrees after that i tend to wait till it cools off a bit. If you are not pushing your load hard you should have no problems with it.

Gary


Gary,
Thanks for the info. This is what I kind of figured would happen, if the are any measurable changes. But, at 44.0 grains I hope that things stay consistent. The chrono and POI will tell any new stories.
On a side note, have you noticed any major variations from one batch of BLC-2 to the next?

To the OP,
Sorry for the hi-jack. I'll end it here.

Shoot safe,
Mike -in GBWI

[earl39]

Q.T. I think you will find the Lee trimmer using a drill or cordless screwdriver will give you a very consistant trim length. I have shelved my green trimmer and gone to Lee trimmers on everything i shoot


Mike check your messages

[helotaxi]

The best description that I've heard of BL-C2 with regard to temp sensitivity is "scary." Like fine in the morning chill to sticking bolts by mid-morning scary.

[Big Caliber]

While I really do appreciate the insight offered on Lee trimmers and BLC-2 powder, I'm still looking for thoughts on whether or not + or - 0.001" or 0.002" is going to make a difference on my trim length. I have no real reason to start all over with a new powder. But thanks anyway. :)

[helotaxi]

It won't make a bit of difference.

[Big Caliber]

Thanks Helotaxi, I didn't think it would but I had to ask. Thanks again to all. :)