sgt_murf Wrote:Bob,
If my explanation is misleading I never meant it to be even though I did not explain in detail headspace vs neck length as well as you did. The point I was attempting is that another manufacturer/gunsmith could shorten or lengthen the neck length. Thus creating the bullet crimping that you and I have attempted to explain, like you put it this doesn't affect Headspacing rather defines the trim length to control the neck length. Headspace is a completely different issue as it deals with a datum Dia in the shoulder to a back of case. Because, I have the AA Chamber I would go by what AA defines. My observation sthus far is that none of my brass has made it to the recommended max length (headspace of my brass is defined by my dies, not a trim length)
I understood your post, and it is clear, I was referring to earlier posts in which some were thinking as long as the bolt would close the case length would be in spec.
Bob
08-06-2015, 05:22 PM (This post was last modified: 08-06-2015, 06:30 PM by billy.)
I realize this is an ancient thread, but I have stumbled across something interesting. I purchased 200 rounds of 123gr scenar directly from AA, and a box of 123gr A-max from a local gun shop. The AA ammo uses Hornady brass (as does the A-max of course). After once-firing on both (did not measure before), the AA is between 1.526-1.531, yet the A-max is 1.516-1.520. Is it possible this is due to higher pressure in the AA loads, or could it be that Hornady trims more on their factory fodder?
[UPDATE] The Lee hand trimmer is set up for 1.516. I am hoping that the .006 tolerance Bill A. mentioned is still valid for their current (4th edition) minimum of 1.520.
[UPDATE 2] A a minor side note, the longer AA brass makes using the Lee hand trimmer wear out your hand after about 40 rounds (for me anyway).
Grendel SAAMI chamber length to the neck mouth is 1.530". What barrel do you have, and what chamber is in it? 1.531" is pretty long for a first time firing. Can't say I've ever seen that really.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
And to add to the confusion, Hornady reloader manual version 8 has max case length of 1.516 with a trim length of 1.506. Their version 10 states max case length of 1.520 with a trim length of 1.510. What changed?
This bugged me a little when I started reloading the Grendel, so here's my interpretation, with no data to back it up.
I suspect Alexander Arms first published their trim lengths to be few thousandths below the chamber neck length of 1.53", which should be a safe recommendation.
I'm guessing Hornady published their initial data after SAAMI specification, when they recommended a length a little below the SAAMI max cartridge case length of 1.52". In the tenth edition, they are showing max case length of 1.52", same as SAAMI. They also recommend a trim to length of 1.51", which is well above SAAMI minimum of 1.50".
How cautious do you want to be? I'd think you're fine keeping the case length a few thousands short of 1.53", thus keeping your neck length as long as is reasonable.
06-20-2017, 04:03 AM (This post was last modified: 06-20-2017, 04:07 AM by diddlyv.)
The amount any given case will grow is a function of how far the shoulder is set back during resizing. Move it back a lot and a lot of brass will be pushed into the neck. Move it back just a bit and just a bit of brass will be forced into the neck. Back in my high power M1A days pretty much had to trim every time I resized my 7.62 brass. I essentially sized my cases to the length of the Die as the die always made contact with the shell holder. One certainly did not want any issues chambering rounds during a match. Cases were only good for about 5 firing before one started seeing the tell tale ring indicating a high probability of a case head separation on the next firing so the brass was pitched.
I have evolved somewhat over the last 20 some odd years and now use comparators. My goal on the Grendel is to only set the shoulder back about .003 - 4. Pretty sure that will keep the case from growing very much.
When I do trim I generally like to trim to the specified length +.002 - .000 as I don't want the necks too short and don't want to waste time trying to hold +- .000 given the generous difference between max case length and trim to length.
Grendel working pressure is much lower than .308, .260 Rem, or .223, so I find that I never need to trim necks for length.
I also like as much neck tension as I can get, and since 6.5 Grendel is less than a caliber in neck length, I avoid unnecessary trimming if I can.
The only brass I've seen exceed 1.530" length is PPU, which is recalled.
I found with the Hornady comparator tool that I need to set back my shoulders .006" or I won't get bolt closure. I use the .350" bushing in the comparator set, and zero out on that once I install it on one side of the calipers.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
I realize this is a very old post but still very pertinent today. I can't speak for every rifle but for my BCA 16" Grendel barrel the Alexander Arms data would be the most appropriate. If you want to check your own barrel's Chamber depth get you a Sinclair Chamber depth gauge. I checked my 16" BCA barrel and the chamber depth using the gauge was 1.543". So technically I could trim my cases to 1.528 and still be at a very safe .015 from the chamber. Best way for you to know is to check for yourself. The gauge is very inexpensive. All it requires you do do is resize and trim down an old Grendel case to a length of about 1.4". Start the gauge in the case neck and slam the bolt down a few times on the case. Then measure the length of the case to the top of the Gauge.
02-02-2022, 11:38 PM (This post was last modified: 02-03-2022, 12:47 AM by Velocity.)
I bought a Sinclair chamber length gauge a couple days ago and the dang gauge would have fell in the case if it wasn't for large rim.
The gauge diameter measures .262 and the once fire case I.D. is .2665
LRRPF52
Can you tell me how a new Starline case that measures 1.5075 and I loaded it and shot it, now the case measures 1.502?
New barrel, this was the 3rd shot through it.
Velocity Wrote:I bought a Sinclair chamber length gauge a couple days ago and the dang gauge would have fell in the case if it wasn't for large rim.
The gauge diameter measures .262 and the once fire case I.D. is .2665
LRRPF52
Can you tell me how a new Starline case that measures 1.5075 and I loaded it and shot it, now the case measures 1.502?
New barrel, this was the 3rd shot through it.
Yea they also have this in bright red on their website... "Should not be used in handguns, semi automatic rifles, lever actions rifles and pump action rifles."
Regarding your case length measurement, I'm gonna go with user error on the measurement side of things. I use the hornady bullet comparator and anvil base set when I'm checking case length as it provides a flat base to ensure the case isn't tilted. Then I use the flat spot next to the bullet opening against the case mouth.
02-03-2022, 01:25 PM (This post was last modified: 02-03-2022, 06:00 PM by Happy2Shoot.)
Velocity Wrote:I bought a Sinclair chamber length gauge a couple days ago and the dang gauge would have fell in the case if it wasn't for large rim.
The gauge diameter measures .262 and the once fire case I.D. is .2665
LRRPF52
Can you tell me how a new Starline case that measures 1.5075 and I loaded it and shot it, now the case measures 1.502?
New barrel, this was the 3rd shot through it.
[ATTACH=CONFIG]18628[/ATTACH]
Case overall length can get shorter because a die is thinner than your fat chamber. When you fire your brass, it goes from thin and tall to short and fat. Resize it and see if it gets longer again.
Velocity Wrote:I bought a Sinclair chamber length gauge a couple days ago and the dang gauge would have fell in the case if it wasn't for large rim.
The gauge diameter measures .262 and the once fire case I.D. is .2665
I looked at my instructions that came with my Sinclair chamber length gauge and it states to full length resize the case before using the gauge.
The instructions on the Sinclair webpage does state to use a fired case without resizing it first. You could use it that way if you used a neck only sizing die or Lee collet die.
I have the Hornady bullet comparator and anvil base set, but wasn't able to find the modified case anywhere, then came across the Sinclair Chamber Length Gage for $5.99.
Talked to Scott at Brownells today and he confirmed the Sinclair Chamber Length Gage is for BOLT RIFLES only.
