Bump sizing the 6.5 Grendel brass

[mdewitt71]

I read about bump sizing the 6.5 Grendel brass.....
I full length size all my loads currently but, was wondering since I am new to 6.5G... I am reading some are getting alot more reloads out of the brass.

If I was to purchase this basic Hornady die set will it work fine for both full length and bump sizing?

https://www.midsouthshooterssupply.com/item/00005546291/6half-grendel-(point264)-full-length-series-i-2-die-set-with-zip-spindle

[LRRPF52]

We are full-length sizing.

You commonly see the phrase "bump the shoulder back enough" when full-length sizing.

It's a common problem that new hand loaders usually experience when loading for a gas-operated firearm because of case stretch.

Your shoulder location ends up more forward because the brass was extracted from the chamber when it was still hot, and not fully rebounded yet.

This needs to be addressed with your re-sizing operation and you need to know how much you need to "bump" your shoulder back in order to get reliable feeding.

If you don't move the shoulder back enough, you will get Failure To Feed malfunctions.

My go-to tool for this is a Hornady Headspace comparator gauge using the .350" bushing.




Unfired new brass:


Fired shoulder location:


Sized This is excessive, but I need .006" of setback to chamber in my ARs. Most will tell you .003".

[ClutchAutomatic]

Thanks for the info!

[bj139]

LRR:
Nice explanation and photos.

md:
Those dies will work but without the tool LRR shows you will not know where you are.
I partially resize by unscrewing the die 1/2 turn from full down and have gotten better groups.
I have not had a failure to chamber yet but I really don't know exactly where my reloads stand.
I may have to resize the brass more fully at a future date.

[mdewitt71]

thanks gents......
I have always fully sized my 223, 308, 30-30, and 3006 loads and never bothered about bumping or even checking it.
They all seemed to chamber if my full length die was set.

[Sticks]

Wow LRRPF52. I thought the typical shoulder bump for AR was .003. You appear to be going back .008.

PUBLIC NOTE - Factory cases from base to shoulder is 1.109 +/-. Typical AR fired cases will run 1.217 to 1.225 depending on dwell time for the bolt. If you have multiple guns and are reloading, you need to either reload for your smallest fired case/chamber, or keep your brass separate to not overwork the brass. I have 4 Howa bolt actions that the longest fired case 1.114" and 2 ARs that are .008 different. I keep 3 different sortings now, and then broken down by number of firings and case weight range.

If you are going for minimal shoulder bump, you should be able to both drop it in the chamber and free fall out, and chamber with the bolt, and extract easy. If you have to pull hard on the charging handle or borderline mortar the charging handle, you did not bump the shoulder enough.

[bj139]

If you are going for minimal shoulder bump, you should be able to both drop it in the chamber and free fall out, and chamber with the bolt, and extract easy. If you have to pull hard on the charging handle or borderline mortar the charging handle, you did not bump the shoulder enough.

Isn't the round getting stuck in the chamber because it is too wide at the shoulder and not because it is too long from base to shoulder?

Think a peg driven into a hole. It gets stuck because of the side force of peg against hole.

Partial sizing would result in less bumpback and also in less shoulder squeeze. Body dies do both at once.

[LRRPF52]

Wow LRRPF52. I thought the typical shoulder bump for AR was .003. You appear to be going back .008.

PUBLIC NOTE - Factory cases from base to shoulder is 1.109 +/-. Typical AR fired cases will run 1.217 to 1.225 depending on dwell time for the bolt. If you have multiple guns and are reloading, you need to either reload for your smallest fired case/chamber, or keep your brass separate to not overwork the brass. I have 4 Howa bolt actions that the longest fired case 1.114" and 2 ARs that are .008 different. I keep 3 different sortings now, and then broken down by number of firings and case weight range.

If you are going for minimal shoulder bump, you should be able to both drop it in the chamber and free fall out, and chamber with the bolt, and extract easy. If you have to pull hard on the charging handle or borderline mortar the charging handle, you did not bump the shoulder enough.

That picture of the sized case is excessive, but I still found that I need .006" of shoulder setback, otherwise I will not get reliable chambering in all of the AR15 SAAMI Grendel chambers I checked in my armory.

It was surprisingly very consistent from barrel to barrel. My Howa Mini chamber is also dead-on as far as shoulder location with the AR barrels I measures, including my Lilja 318, Lilja 22" bull, and AA 18" fluted x 2.

I can't recall if I checked my LaRue chamber yet for shoulder location on fired brass.

In the reloading handbooks, I recommended .003-.005" per Sierra's discussion of loading for the AR15, but I simply can't get reliable chambering if I even go "down" to .005" setback of the shoulder.

I'm using a stripped bolt without ejector or extractor with the same face depth and lug length when setting up my dies and testing loads for chamber compatibility.

The bolt will not rotate into lock when cases are sized down to .005".

I'm going to try this on my Forster Co-Ax when I get it installed to see if that changes, but the brass measurements are what they are.

The biggest concern here for those that aren't tracking is over-working the brass, which can cause case head separation after a number of loads on the brass.

[ClutchAutomatic]

going to order a 350 bushing today to make sure my dies are over working for my next batch, can I just compare new factory ammo and a previous sized and fired case? I don't have any new unfired cases.

[Clarence]

If you're only shooting one rifle, you can measure a fired case and resize your cases 0.003"-0.004" shorter than that. I've not run across the situation where more "crush" is required, but LRR has a lot more experience. As he said, try a few of those to make sure they chamber correctly before you load a bunch. It's no fun to have a cartridge fail to chamber and have to either get very physical with the rifle or remove the upper and use a tool to pop the bolt carrier back to remove a long cartridge from the chamber.

Clarence

[LRRPF52]

If you look at my pics, you'll see that factory ammo brass or new brass is much smaller than it will ever be again unless you really find a way to crush it (not good).

Work the brass minimally, but with enough sizing of the body and shoulder to get reliable feeding.

I like the comparator tool for this reason.

[ClutchAutomatic]

Will report back when it comes in, just loaded 50 more today with the die set at where it was giving me good results last time.

[ClutchAutomatic]

Tool came in today, I measured the factory ammo hornady black at 1.210 and averaged the fired brass at 1.220. Should I be looking for a 1.215-1.217 set back?

Edit: without touching my dies looks like I set it up spot on. Was getting a .004 setback. Next question, how many fires do you go before trimming?

[Wafavre2]

Trim to 1.520, when you measure longer..I trim to 1.516 and don’t load hot. I get 3-4 reloads without having to trim. I debur and champher after resizing every time.

[Drillboss]

Tool came in today, I measured the factory ammo hornady black at 1.210 and averaged the fired brass at 1.220. Should I be looking for a 1.215-1.217 set back?

Edit: without touching my dies looks like I set it up spot on. Was getting a .004 setback. Next question, how many fires do you go before trimming?

Even though one can get by without it, I love that tool.

0.004" setback should be good. Drop a case into your chamber and see if the bolt locks up on it and if it extracts easily.

My experience has been that after I first resize brass from factory ammo, the case length is at or near max. I usually end up trimming that once fired brass and then don't have to worry about it for several reloads. Actually, I'm not sure that I've ever had to re-trim a case. I should keep better notes.