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Discussion Starter · #1 ·
Hi all, looking for some help from the reloading gurus here on a MAX COL issue (I think) that is new territory for me. Feel free to jump over the "backstory" if you want to get straight to my problem and help needed

Backstory:
A few years ago I picked up a Black Hole 22" .260 Remington barrel for large frame AR at a killer price from True Sporting Arms, the online outlet for Columbia River Arms.

I probably put ~100 rounds through it before I swapped it out for an 18" 7mm-08 barrel from Wilson as I really wanted a more compact platform for the field (this was built on a 2A Xanthos lightweight frame).

Well, you can't just have a spare barrel lying in the safe, now, can you? So I put the .260 barrel back on an Aero M5 upper and finally decided to give it another try.

Rifle:
Aero M5 Upper/lower, BWH .260 Remington SS barrel w/ only ~100 rds, JP Enhanced Bolt and LMOS Carrier

Issue:
I loaded one round using 1F SSA brass and Nosler 130gr RDF with a COL of 2.79. I decided to check the round in the chamber. Bolt closed, but I had to mortar the rifle to extract. Set back to 2.79. Same. 2.775 - seems to be ok, but next round at 2.777 required mortaring to extract. Nosler manual says load to 2.80. Seems like I shouldn't have to drop COP to 2.76 to safely stay off the lands.

I'm pretty sure, but not positive that the rounds are jamming the lands. I don't have a great way to measure distance to lands. I tried the technique of marking a cleaning rod but came up with something ridiculous like 2.65 max COL so I don't trust that.

I suspect I have an out of spec chamber, but any other ideas? Tight / dirty chamber? Headspace issue? Brass sizing issue? Just need to break it in? Common issue with RDF bullet? I've ordered some additional bullets to try but that's the only 6.5 pill I currently have on hand.

I'll play around more with other brass and techniques trying to measure the distance to lands / max COL this evening, but thought I'd post this for other ideas I may be missing. I had this issue with loading 77gr bullets long in a .223 but I only had to back off COL by 10 thou to reliably fix it. Dropping 30 or 40 thou off spec seems wrong.

Any recommendations?
 

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Could be tight headspace, but first thing I'd try is take a Sharpie and color the bullet and neck of a cartridge and try cambering it. That will tell you where your interference is.
 

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Could be tight headspace, but first thing I'd try is take a Sharpie and color the bullet and neck of a cartridge and try cambering it. That will tell you where your interference is.
This is a good place to start.
Also, you may consider the Hornady OAL tool with a 260 Rem case. I have one 260 Rem barrel that WILL NOT let me load Nosler bullets to what Nosler lists as OAL.
 

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+one on the sharpie. Just try slowly dropping it in to see the resistance. Black will come off where it is touching.
 

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If you done have a Hornady coal measuring tool, easily enough if you don’t, metaled fired case size it the just load bullets snd pill the 10 or 15 times this will streak the neck to the point where the bullet will slide in and out minimum resistance l. Put you bullet in seat the round in the chamber. The retrieved round will give you an accurate measurement. Let us know what you find out.


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Sort of first not make sense though as high BC bullets should load long as the ogive is close too the neck


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Discussion Starter · #7 ·
Thank you all for your help and suggestions. I think I figured it out and, of course, the problem is me. Looks like I didn't set up my FLS die properly and I had little to no shoulder bump so it appears it was the brass that was getting stuck in a tight chamber forcing me to have to mortar the round, not bullet jam. As suggested here, I used a piece of once fired (in this chamber) Lapua brass that had enough neck tension to hold the bullet but let it slide, used a sharpie to color up, and removed my extractor. Much to my surprise, it came out the same length it went in at over 2.905 with no indications it even touched the lands. Confused, I then used the Hornady headspace comparator to figure out that my FLS brass measured the same as my fireformed brass. I gave my FLS another quarter turn and that bumped the shoulder back a bit and now the rifle chambers 2.80 COL load with no problem. Made me realize I had never actually shot any of my own sized brass as all my handloads had been with virgin brass.

What do you guys think is appropriate shoulder bump for a .260? Based off this experience, I'm guessing it depends on the rifle's specific chamber. I've never really paid that much attention to it before and just relied on the case gauge. If I'm doing it right, I've got a shoulder bump around .005. The difference between factory new and fire formed Lapua brass is 8 thou but I don't think I need to go that far. I know there are several post around here on shoulder bumping so I'll go peruse those.
 

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I always target .004 as setback on the shoulder. If you're already at .005 on set back, just go with it.
 
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