The Build
Bushmaster lower
Aero Precision Upper
Lilja 24” 260 Rem Barrel (Original ordered a Shilen)
Magppul PRS Stock
Vortex Viper HS 6x24 first focal plane scope with Vortex 20moa Scope base
JP Enterprise Competition 3lb trigger
JP Enterprise 17.5” free float hand guard
Superlative Arms adjustable gas block
Harris Bipod


I’ve been building AR pattern rifles since I joined in 2001.   I’ve built well over a dozen in various calibers and configurations and with the exception of a silenced SBR in 9mm have functioned flawlessly. (The 9mm eventually was fine tuned to become a great performer.)

Well this build started in August of this year with a $$$$ order from Midway USA for the Scope, Trigger, Shilen 260 barrel etc.  I already had a Bushmaster LR-308 that I scavenged the lower, bolt and charging handle from and sold the barreled upper on the EE and used the funds to complete the build.

Decided to go the 260 Rem route instead of the 6.5 Creedmoor since the ballistics were so similar and I have an investment in 308 reloading.
Purchased the Aero Upper and JP hand guard from other members and scoured my parts bin for the remaining items.

I watched and thoroughly enjoyed Fitty’s (tfblkhwkguy) video on his 6.5 Creed build http://www.ar15.com/forums/t_16_4/3893_My_6_5_Creedmoor_Build.html
Following his advice, I had the receiver lapped, used the Indian head gasket cement and tourqed the barrel to spec trying to get the best accuracy possible from this build.   Replaced the stock trigger with the JP Enterprises competition trigger and tuned it for a glass break 2.5 lbs.  Added the Vortex scope with the 20 MOA mount and level aligned and bore sighted.

S H I T.   Dumb Ass me never bothered to check the Shilen barrel by chambering a round until the build was complete and the Indian head gasket cement had set.  Should have, could have, but didn’t check the chamber or use a go no go gauge and found out the hard way that the chamber was never finish cut. Since the Shilen barrel came with a matching bolt that was supposedly head spaced and matched to the barrel it never occurred to me not to be a dumb ass and check it anyway.

Midway USA as always was great and accepted the returned barrel but I still had to go through the pain of removing the barrel and removing all the head cement.

God Bless the folks at Lilja. They had a drop in 24” stainless 260 barrel in stock and their very cool HeartBreaker flash hider (more on that later).  A few weeks later the Lilja barrel was installed, the flash hider timed and red locktited in place and the rifle ready for its first range report.

Needing Ammo, I annealed, sized, and trimmed 100 rounds of 308 LC brass. Then resized it to 260 and then loaded 140 gr JHPBT Barnes Match Burners over 42.8gr of IMR 4350 with Federal gold match primers and off to the range I went.

Started out at 25 yards to get the scope zeroed and damn,  for a high end barrel this thing wasn’t even showing any love at 25 yds.  Well I followed the break in instructions and fired and cleaned between rounds and still shot like shit.  After about 20 rounds, I had trouble after a mag change in pulling the charging handle and found out that the charging handle catch pin had worked its sorry ass loose and would not allow the handle to latch.   End of Range trip 1.  Very disappointed.

New latch catch pin installed, barrel cleaned and load changed to 42.5 grains due to flattened primers.

Range trip two begins with high hopes.
Starting to group ok at 25 and move out to 100 yards and oh shit, oh dear,   need to adjust the scope to the right stop to get it on paper.  Check the scope rings,  check the barrel torque when I got home, and all looks good.  Bad scope? Bad mount? Bad distorted upper?  Not sure.  Called vortex and they suggested the 20moa base may be the problem so they sent me a replacement.  With the new base installed, I was back on the paper with 30 click to spare but was seeing key holing and 6” groups.

FUCK FUCK FUCK.  Is there no God of simple builds?

Range trip 3.
Talking to Carson Lilja (a great guy)  over a few weeks, suggested I remove their beautiful heartbreaker flash hider to see if grouping improved and damn if that wasn’t the problem.  I sent it back to Lilja, and waited yet again, and they overboard it to .270 and after reinstalling it I finally had a rifle that showed potential but broke the damn extractor after 3 shots.

Brass was really flying and coupled with the broken extractor.  Decided to change out the fixed gas block with an adjustable and after waiting again for parts the build is really complete.

Range Trip 4 delayed due to the Thanksgiving holiday.
Beautiful day in the hi 60s,  a bit breezy but nothing over 15mph


Settled in to decent groups but after 30 rounds, opened up terribly



But closed up again after cleaning.



I’m sure it is much more accurate then I am but withholding final judgment until I get a few hundred rounds down the pipe. Need to work up a load it likes and adjust the OAL until it’s a one holer.

Comments and suggestions will be greatly appreciated.

Looks nice OP.  I haven't built anything in a while and am fighting the temptation to build a precision 6.5 Grendel upper.

Dang!  Everything that could have gone wrong, just about did.

Are you turning your necks on .308 cases after sizing down to .260 Rem?

What are you doing to address neck tension and consistency with re-sized .308 brass?

I can't even chamber sized .308 brass once a bullet is seated without turning, which is why I never messed with .308 brass other than one piece.

It was too easy to size-down Winchester 7mm-08 brass back then.

Now there is Lapua brass, so no reason to jack around with sizing down unless you have a lot of time on your hands.

I personally just sent all my parts to GA Precision, told them to spin up a Bartlein and do all the chambering, profiling, gas port work, bedding, gas block unitizing, etc. and send me the bill.

Yes the one thing I do have is too much time on hand .  Recently retired.

Yes I am neck turning the 308 brass after anealing, trimming, and resizing to 260.  Not really sure about neck tensioning but I do a a very light crimp with a Lee factory die.

No problem with chambering and with the adjustable gas block the rifle is much better behaved.

Next go around is to load from min to max at .5 grain intervals to see what it shoots best.

Very nice looking groups you have

You and Murphy must be good friends! 

Nice lookin shooter though, hopefully it all comes together and just runs. Stories like yours are always lingering in the back of my head whenever I'm doing another build......

How does your fire-formed brass spec out for headspace compared to unfired?  How much does the shoulder move is what I want to know.

You can try playing with seating depth too.

One bullet that really shoots well for most people I know is the 139gr Scenar on top of Hodgdon's extruded powders like H4350 and H4831SC.

Are you seating with a turn midway to mitigate runout?  I seat part way, then rotate the cartridge, then seat fully so the bullet is as aligned with center as possible.

LRRP is right.  I run the 139gr Scenar in both of my .260 comp rifles (one gas, one bolt).  In the gas, I tuned the load down, helped to ensure proper rifle function, as well as maintained my brass (no dents, scrapes, etc...) I settled on 41.7 of H4350, seated to PMag length.

You may want to try not using the neck crimping die also.  I used to think the neck tension issue was bullshit, until I did it! HAHA!!!  I believe that if you are going through the trouble of turning your necks, you should definitely invest in a good quality FL bushing die, such as the Redding die.  I'm sure the crimp is okay, but the bushing allows for a more precise amount of control on the measurement.  Afterall, we are trying to make these rigs "precision" rifles, right?  Consistency is everything.

I do run .002" neck tension, but most recommend at least .003-.005 on a gas gun.  I believe .005 is way too much in damn near gun; I am just lucky that I can get away with .002 in my LRP.  There is much support indicating the least amount of neck tension will provide the more accurate results.  I actually read an article where some of the F Class guys basically took to indenting the necks of their cases at the same location on all of the cases.  This provided somewhat of a "step" for the bullet to rest on as they simply slide the bullet into the neck with their fingers, ergo, they used 0 neck tension.

I hope your build works out for you.  Looking very promising.  I've shot PR rifles comps for the last 7 years now, and I've seen calibers come and go (I'm sure we all have), kind of that, "hey, here I am, here's my super duper whizz-bang 6.5 Creedmoorex47 Lapua SLR!"  No matter what has come along, I have always remained faithful to my beloved .260.  It is simple.  The loads are very forgiving and I can get brass from a few different cases.  I'm hoping that at some point, that Prime and Hornady .260 ammo actually get priced to a point where they can be reasonably purchased.  

Keep us posted.

LRRPF52 & FALex,

Thank you both for your advice.  I've been reloading for years and really didn't give much thought to neck tension until you've brought up the subject.

My neck thickness after turning is .015 and final diameter of a loaded round is .294 which is .264 for the bullet and two neck walls .015 x 2 =.30 which is right at .294.

I'm ordering a FL bushing die with .291 bushing which should give me .003 for uniform neck tension.

Do you aneal your brass after each firing or any other tricks of the trade you care to share?

I'll post a followup after I work up some new rounds and hit the range.

Thanks!

Glock9

The saga continues.  

I received my Redding S die and using a .291 bushing loaded up 40 rounds with 42gr H4350 loaded to mag length 2.820 oal and hit the range today.

Wow what a difference the neck tension made.   When I did my part, I was able to make clean cloverleaf holes and finally saw the potential I had hoped for in this build.

Then fate interviewed AGAIN.  I had 6 rounds left from a previous load that were on the hot side at 42.7gr that I noticed caused some pressure signs of flattened primers last outting.

Fired 3 round and the fourth went click.  Looked like a light strike so tried again and another click.   Here we go again.  Pulled the bolt and the firing pin would not pass through the hole in the bolt.  Policed my brass and headed home disappointed again.

Disassembled the bolt and the firing pin tip is deformed and looks like metal deposited in the hole. WTF???  Cleaned the bolt and removed the deposits and the firing pin moved freely

Sorting through the brass I found one casing with a pierced primer which would explain the damage to the firing pin.

New firing pin on order.  

Thanks to all for their advice

Most likely it was a blanked primer and not pierced. Make sure you are using a small firing pin and hole face around .060 to help prevent it. I didn't see where you specified a Bolt in the build.


Ryan

Ryan,

I'm using a Bushmaster bolt and carrier with the large firing pin.

Here is a picture of the primer and I agree that it looks more like it was blanked

I've found 6.5 creed bolt with the small firing pins but not a 308 - 260 rem with it.  any suggestions on where to find one?

Thanks!

A 6.5 Creed bolt should work just fine for the .260, as well as the .308

You could also have your factory bolt bushed, and pin turned down, but that might be an expensive solution.


Ryan

JP high pressure bolt, but they are not cheap.  Rubber City armory makes one too, IIRC

OP - I wouldn't hesitate to get the JP HP bolt.

Also, wanted to comment on your powder situation...

You're running IMR 4350 which has a faster burn rate than H4350.  I shoot H4350.  I was finding that anything over 42.5 was getting to be too hot, IMHO.  Then again, I am not one to hot rod my loads, but it was hot for my barrel.  If you're running a faster burning powder and you're running at 42.5+, you may want to consider tuning it down some.

I settled in on 41.7, but 41.5 also shot very well, just had a bit tighter groups with the extra .2.  

In this game, velocity is not everything.  Accuracy trumps it 8 days a week.  

Just another suggestion.  Sorry about your frustrations.  It appears you do have some light coming from the end of the tunnel.  Stick with it.  I'm sure you'll have a hammer once you get these last couple issues addressed.

You make me want to get working on my LR260 again. I have a DPMS hunter with an 18.5" barrel, muzzle velocities suck.

Glad your getting it sorted out.

Ok, I know it's been a year but my long and painful build is finally a shooter.

If you've read through the thread you've seen that Mr Murphy has been my co pilot and has fucked with me at every step of the build.

After replacing the bolt with the enhanced small firing pin bolt assembly, settling on a 41.5 gr IMR H4350 load with Barnes Match Burner 140gr bullets the, rifle was finally reliability but not repeatably accurate.

While cleaning, I notice a very slight cleaning fluid movement between the barrel extension and the upper indicating the barrel was not properly bedded and there was play.

When I built it, I used Indian Head Gasket cement per Fitty's instructions and thought I did an OK job of lapping the barrel using an aluminum flat stock and lapping compound but apparently the head gasket cement did not provide a solid enough bedding to secure the barrel to the upper even with 60lbs of torque on the barrel nut.

So with Mr Murphy's help again, out with the heat gun and off with the barrel.

This time I ordered a proper AR10 lapping tool from Pacific Tool

Also ordered lapping compound, Locktite 620 (green) and some .001 stainless shim material.



Thoroughly cleaned the upper after lapping the receiver,  also make sure the alignment slot is deep enough after lapping so you get a flush fit.

After measuring the barrel and the upper I needed to build up the barrel extension .003".  Using the one wrap or .001 stainless shim, that added .002 to the diameter and the last thousand was filled by the green locktite which added just enough lubrication to tightly fit the shimmed barrel into the extension.  Torqued it to 40lb and headed to the range.

Dropped of Mr Murphy as his fucking with me was no longer required.



Final results.  1st cold bore shot is slightly low and the reaming 4 are a cloverleaf.

Congrats!

That's awesome!

Very nice!

i did the same thing except i sent compass lake my armalite ar10t and had them rebarrel to a krieger in 260. on something that expensive it’s nice to let the professionals put it all together.