AR-Stoner 6.5 Grendel barrel short chambered.

[LongRanger]

I have solved my AR-Stoner barrel short chamber problem on one of the two 18" barrels that I have and expect this solution to correct the second one also. My original OAL with Hornady 6.5 mm 123 grain A-Max bullets with this barrel was measuring out at 2.245 to 2.246" with a Hornady overall length gauge. Factory A-Max measured 2.252" with my caliper so I felt it was unsafe to shoot that load. I loaded up 50 Tubb's final finish bullets at 2.20" OAL and at minimum powder loading as directed. I fired 5 rounds and then cleaned the barrel. I ran through the five grades of finishing compound totaling 50 shots cleaning after each five rounds fired. After the Tubb's final finish, the measured OAL for that chamber had increased to 2.300". Must have had several rough spots in the throat that got polished out. I also picked up an increase of 23 fps to 2443 average with the Wolf MPT 123 grain ammo (2.23" OAL) that I tested before and after the above treatment. ES and SD before was 22 & 11 and went to 9 & 4 after the Tubb's final finish. The overall length of this chamber is now identical to my original 6.5 grendel 24" SAOD barrel which is also 2.300". I will be ordering another Tubb's 6.5 mm final finish kit to shoot through the other 18" AR-Stoner barrel when I get back from working offshore for the next two weeks. It cost me around $50 total to fix this problem which should not have been at my expense to begin with. Tubb's FF is around $38 at MidwayUSA and you must be a reloader to take advantage of those bullets.

[MikeGideon]

I have used FF on a couple of barrels. It will polish off the burrs. I wouldn't use it on a match grade barrel.

[LongRanger]

I have used FF on a couple of barrels. It will polish off the burrs. I wouldn't use it on a match grade barrel.

Match grade barrels would most likely have been hand lapped. I will not be using Tubb's final finish kits on my two 6.5 Grendel Lilja barrels when they arrive as they will have been hand lapped and should not need any further polishing of the barrel or the chamber.

[MikeGideon]

Match grade barrels would most likely have been hand lapped. I will not be using Tubb's final finish kits on my two 6.5 Grendel Lilja barrels when they arrive as they will have been hand lapped and should not need any further polishing of the barrel or the chamber.

Yep. Both of my Grendel barrels are hand lapped. One JP, and one Shilen.

[45r]

I have solved my AR-Stoner barrel short chamber problem on one of the two 18" barrels that I have and expect this solution to correct the second one also. My original OAL with Hornady 6.5 mm 123 grain bullets with this barrel was measuring out at .2445 to 2.446". Factory A-Max measured 2.252" with my caliper so I felt it was unsafe to shoot that load. I loaded up 50 Tubb's final finish bullets at 2.20" and at minimum loading as directed. I fired 5 rounds at a time and then cleaned the barrel. I ran through the five grades of finishing compound totaling 50 shots. After the Tubb's final finish, the measured OAL for that chamber had increased to 2.300". Must have had several rough spots in the throat that got polished out. I also picked up an increase of 23 fps to 2443 average with the Wolf MPT 123 grain ammo (2.23" OAL) that I tested before and after the above treatment. ES and SD before was 22 & 11 and went to 9 & 4 after the Tubb's final finish. The overall length of this chamber is now identical to my original 6.5 grendel 24" barrel. I will be ordering another Tubb's 6.5 mm final finish kit to shoot through the other 18" AR-Stoner barrel when I get back from working offshore for the next two weeks. It cost me around $50 total to fix this problem which should not have been at my expense to begin with. Tubb's FF is around $38 at MidwayUSA and you must be a reloader to take advantage of those bullets.

Thanx for your post.
It would be nice if Saturn would get some at a volume discount and send to those with any barrels that are problematic.
The Tubb's FF is a good remedy for these barrels.
If it's just a rough throat and not being able to reload I think shooting a few bullets(hornady 123SST's) and cleaning with JB's or flits every 3 shots might smooth things out after a box of ammo.

[MikeGideon]

Thanx for your post.
It would be nice if Saturn would get some at a volume discount and send to those with any barrels that are problematic.
The Tubb's FF is a good remedy for these barrels.
If it's just a rough throat and not being able to reload I think shooting a few bullets(hornady 123SST's) and cleaning with JB's or flits every 3 shots might smooth things out after a box of ammo.

You may be able to just shoot the problem away. But, if it's too rough to even chamber factory ammo, I would make the manufacturer deal with it. Frankly, I think they owe that to their customers.

[rickOshay]

Satern's Response

XcountryRider received the following email from Steve Satern in response to the issues raised in this thread. XCR is at work right now and asked me to post it for him in the interest of time:



“We use JGS, PTG, and Manson for our go/no-go gauges. We buy the reamers from PTG and JGS, and they have the print from SAAMI and that's what we follow. Bullet manufacturers and ammo manufacturers do not consult with us. They are making ammo and we are not privy to their specs or tolerancing. SST's have been working fine. So what does that tell us? That it is an adjustment on the ammo manufacturers end. A reamer and a barrel when it's chambered are snap shots in time. They don't change unless they have been extensively fired. What does change over time are the dies that the bullets are made on or the dimensions to which the manufacturers load their ammo. The dies that the bullets are made in are constantly going through polishing and lapping to be in service longer. They do change minutely from run to run, as form dies are worn or replaced. The makers try to keep them as uniform as possible, but there will always be some variance. And the copper and lead core make a difference to the degree of being harder or softer as they go from one lot to another.

The Grendel and the specs written around it for the bullet were written for 87-107 grain, using Sierra's at that time. I've used 123's at Camp Perry but had to seat the bullets according to the lot of bullets used at that time to fit in the chamber. As a barrel manufacturer, our primary concern is checking the chamber with go/no-go gauges. No-go is the middle of the specification, it just has the connotation of a bad reference. Not passing the field gauge is cause for rejection.

There is no Saami spec or requirement for throats. It's up to the reamer manufacturer to grind it to the print. JGS, PTG, and Manson are very reputable reamer makers. If we go to one of the reamer manufacturers and tell them to lengthen the throat and open the free bore, we would be outside SAAMI tolerance. Bottom line, if we re-reference that SST’s work, then that means somewhere along the line is a disconnect from the ammo manufacturer to the ogive requirements in the throat of the chamber. I'm sorry but I can't police everyone's hand loading practices.

This chamber was designed around the Sierra bullet at that time. Hornady runs a different ogive than Sierra. There are 6 bullet manufacturers that come to mind: all of them have a different ogive than all the others, touting superior ballistics, or even in a VLD form. Some are secant, others are tangent, and more recently, some are now hybrids of the two. It varies by manufacturer. If you take the number of bullets in 6.5 in a bullet company’s advertised list, times the number of manufacturers, how many variables are there now in ammo? These ammo manufacturers don’t call us up asking our opinion. We go off of the SAAMI prints provided by the 3 reamer makers. Unless we can get SAAMI to move the throat forward, there is not much we can do.

In the benchrest world, they advocate shorter throats. In the semi auto rifle world, you need clearance and tolerances. That's why the 6.5 has a .300 diameter neck. As far as the throat goes, we will talk to PTG and JGS to see if there has been a change that we have not been made aware of. Currently, we don't believe there has been one. The overall length of bullets varies tremendously even inside of one box of ammo. Benchrest shooters and high power shooters go by the ogive and not the tip of the bullet. It would be ultra great if RCBS would make one of their MIC gauge combos for the 6.5 Grendel. This would help eliminate a lot of the difficulty of sizing the brass in reloading and the bullet seating depth at the ogive.

We're sending a picture of a cartridge and ammo that one of our guys has had for a couple of years and it went into the chamber just fine and had no marks on the bullet, and its factory Hornady ammo. We checked the headspace, and the bolt spun free with a loaded round in the chamber. WE DON’T RECOMMEND DOING THIS THOUGH!

It's just a thought, but there has been a shortage of bolts and barrels in the last 18 months to 2 years. So the ammo that has been made could have been seated longer, due to the barrels having wear because of excessive use, and it wouldn’t have been detected until now. How do we move the throat with each ammo run? We are not privy to this information from the ammo manufacturers; we simply make our barrels to SAAMI specs. Please pass this on to your friends, and I hope it helps.”

- Steve

[MikeGideon]

Wow.

[PigOPs]

So dies wear out but reamers don't? Can I just say that I love the Grendel, but wonder sometimes if it will live through these "growing pains".

[Tedward]

You may be able to just shoot the problem away. But, if it's too rough to even chamber factory ammo, I would make the manufacturer deal with it. Frankly, I think they owe that to their customers.

Like I said on my prior post, these barrels are not hand lapped. Its like a new pair of shoes, wear them and then will break in.
Shoot them with factory ammo, they break it in. Then go to your measuring and hand-loads.
Glad the was a quick resolution for you so maybe that is the problem, a new NOT hand lapped barrel.

[Tedward]

So dies wear out but reamers don't? Can I just say that I love the Grendel, but wonder sometimes if it will live through these "growing pains".

I think Steve can check and QC his equipment and replace it as needed but he doesn't know what QC processes of the ammo manufacture or how they often they replace there tools.

Are there ammo tolerances and shapes then need to follow per caliber or just OD's like .264? Is there an Ammo Spec that must be followed? Let us know. Now you have me wondering. SAMMO?

[XcountryRider]

When I get home I'm going to check my seating again and ensure the depth are with loading manual recommendations.

[JASmith]

...Are there ammo tolerances and shapes then need to follow per caliber or just OD's like .264? Is there an Ammo Spec that must be followed? Let us know. Now you have me wondering. SAMMO?

The SAAMI drawing specifies the cartridge as well. It does not, however, specify the maximum allowable ogive for the bullet.

You can bet, however, that no reputable ammunition manufacturer will ship ammunition that will bind or otherwise have trouble in a SAAMI-spec chamber and throat. They won't do it more than once because the cost of replacing the bad stuff, their reputation, and future sales is just too much to bear. They need to sell reliable product or their cash flow disappears.

Further, if the ammunition has somehow crept out of tolerances, the complaints we are discussing would cover a lot more than one manufacturer's barrel and the reamers that made the chamber.

That is why folks suggest checking with more than one factory load, but if the cartridges don't fit, the chamber has one or more problems the barrel maker needs to correct.

[Tedward]

The SAAMI drawing specifies the cartridge as well. It does not, however, specify the maximum allowable ogive for the bullet.

You can bet, however, that no reputable ammunition manufacturer will ship ammunition that will bind or otherwise have trouble in a SAAMI-spec chamber and throat. They won't do it more than once because the cost of replacing the bad stuff, their reputation, and future sales is just too much to bear. They need to sell reliable product or their cash flow disappears.

Further, if the ammunition has somehow crept out of tolerances, the complaints we are discussing would cover a lot more than one manufacturer's barrel and the reamers that made the chamber.

That is why folks suggest checking with more than one factory load, but if the cartridges don't fit, the chamber has one or more problems the barrel maker needs to correct.

That sound like an accurate and reasonable statement. Since your into the Grendel Reload Book deep, you probably know concerning the Grendel. So do you think with the result that LongRanger had with the polishing bullets might mean it just needs broke in since they barrels are not hand lapped? I wonder if they are wire brushed or what method of cleaning is done. Is that up to the buyer?

[customcutter]

[QUOTE=PigOPs;83859]So dies wear out but reamers don't? /QUOTE]

Two completely different types of "wear". The dies will wear because of dirt, grit, dust, any contaminant that is on the jacket. I don't know if he is refering to the bullet forming dies, or the loading dies. Possibly the loading dies are out of adjustment?

The reamer will wear the cutting edges and will begin to chatter. It would be evident through out the chamber, not just in the throat.

I think this issue is maybe a combination of non-lapped barrels and extremely high BC bullets with modified ogives. I know my chamber closes and extracts the 123 SST's. I know I won't be fire lapping my barrel.