First Rounds from New Build

[kpswihart]

I put together a new build over the past several weeks and was able to spend a little time at the range today. Pretty common parts, Anderson lower, Aero Precision enhanced upper and an Odin 18" tube. Pretty happy with the way it turned out.

IMG_2780.JPG

Caught a break in the SE Alaska weather today and headed to the range to check function. Threw a Leupold 1.25-4x from a friend on it for initial testing. Shot both factory A Max and SST at 100 yds. Because I only had a little time and was primarily checking function, I used a couple of range blocks and a soft case as a rest. The SST shot a little better than the A Max. I think with a better rest and a little more magnification that it will shoot.

IMG_2785.JPG

Fired 32 rounds with no malfunctions. I did have 4 primers from the 12 SST's that were pierced or pretty close to it. Have to do some research to determine what may be going on.

IMG_2786.JPG

Overall pretty happy with it. Can't wait to get out again. I really appreciate all the information folks have taken the time to post here, it has been a great help.

[Drillboss]

Nice rifle, nice shooting.

[jim_bob]

Pierced primers on factory SST's would be a concern for me, 12 is not a decent sample size, but 33% is a huge percentage. Did you notice any other indicators?

Nice looking blaster!

[kpswihart]

Thanks Drillboss, much appreciated.

I also appreciate your response jim_bob. No other indications on the spent brass. No complete perforations either that I could see. I did notice a couple of things on my BCG.

When unlocking it manually, with or without a loaded round, the unlocking took a little more effort than what I expected. I'm wondering if new components aren't as smooth as they should be and that's causing a hangup in unlocking. Is there anyway that slight hangup could cause the primer to be pushed back into the firing pin during the process.

The barrel, BCG, tube and block are Odin and were purchased from the same vendor at the same time. I compared the firing pin to a milspec Colt firing pin. The Colt was noticeably "sharper" and thinner. However, the shoulder (if that is the correct term) on the Odin was noticeably thinner. The Odin shoulder appeared to be the same distance from the tip as the Colt. I did not have a micrometer to measure though.

I'm going to try to locate some headspace gauges for verification, but any additional thoughts would be appreciated.

[Drillboss]

Take the upper off and drop a round into your barrel and then turn it upside down. If the round doesn't drop free, then the bullet may be engaging the lands resulting in higher pressures. If it drops free, then you're good on that point.

I've had one barrel/bolt combo result in sticky extraction on unfired rounds. Turned out the headspace was a little tight, but I wouldn't think tight headspace would result in higher pressures causing your close to pierced primers (someone correct me if I'm wrong). Every factory round I've fired through 3 different Grendel barrels shows some slight cratering around the firing pin impact.

I like using the Hornady headspace comparators on a caliper to actually measure my fired cases and compare that to SAAMI specs.

[Nicaburns]

Are you, by chance, using an enhanced firing pin?
(I ask to my shame since I once mixed up my 7.62x39 pin and got a couple of pierced primers on the Hornady 123 amax)

[ricsmall]

Do as drillboss suggests, insert a round then try to drop out. It should easily fall out. I've had acouple friends with barrels that were saami spec, but minimum saami spec and I had to lightly hit them with my saami reamer to alleviate these same primer problems as well as loaded rounds sticking in chamber.

Richard

[Bwild97]

The Odin barrel I used in my latest build also had a tight chamber, compared to my other 3 grendels. Some of my mag length ammo would not chamber in that Odin barrel, the steel cased wolf ammo functions flawlessly!!

[kpswihart]

Rounds drop in and out of the chamber easily. I'm not using an enhanced firing pin. Barrel, BCG, tube and block were ordered together and things look correct. I have noticed a little stiffness locking and unlocking, even with an empty chamber. I chalked this up to new parts, but it takes more effort to unlock than it does to lock. The Aero enhanced upper puts the tube pretty much where it goes and doesn't require timing a barrel nut. I haven't noticed any contact with the BCG. I didn't notice any firing pin damage.

I did a little research last night. Seems like this happens on occasion with Hornady ammo, and I ran across a thread or two regarding short bolts. I'll measure the bolt this evening and order some head space gauges to verify. I'm still thinking there is an issue with the bolt mating to the extension. My only other thought is that bolt movement in the carrier is stiff so maybe the bolt is not moving freely enough in the carrier to allow smooth operation.

I appreciate all the thoughts. I think this one will shoot, just need to make sure it shoots safely. Keep the ideas coming please.

[Commander184]

I had the wrong bolt and that made an unfired round very sticky. My bolt measured .130" and I was having to knock back my shoulder .005. I ordered a. Only directly from lilja that they say measured .136". Seemed like my problem was right there. Bolt should be in this week

[LRRPF52]

I've been shooting the Hornady ammunition since it hit the market, and have never seen anything close to pierced primers.

Pierced primers is often caused by bolts that are too short. When using the .136" bolt face depth, you need to add at least .010" onto the tail of the bolt in order to prevent pierced primers.

If you allow flame-cutting of the bolt face regularly, you have a very bad situation brewing.

Measure the overall length of your bolt with calipers and let us know what that measurement is.

[Commander184]

I've been shooting the Hornady ammunition since it hit the market, and have never seen anything close to pierced primers.

Pierced primers is often caused by bolts that are too short. When using the .136" bolt face depth, you need to add at least .010" onto the tail of the bolt in order to prevent pierced

If you allow flame-cutting of the bolt face regularly, you have a very bad situation brewing.

Measure the overall length of your bolt with calipers and let us know what that measurement is.

How would you add the .010?

[kpswihart]

I've been shooting the Hornady ammunition since it hit the market, and have never seen anything close to pierced primers.

Pierced primers is often caused by bolts that are too short. When using the .136" bolt face depth, you need to add at least .010" onto the tail of the bolt in order to prevent pierced primers.

If you allow flame-cutting of the bolt face regularly, you have a very bad situation brewing.

Measure the overall length of your bolt with calipers and let us know what that measurement is.

I took a few measurements this evening.
2.78 Bolt length (maybe a little short)
.136 Face depth
3.26 FP length
.528 Bolt width at belt
.277 avg lug length

Manipulating the bolt inside the BGG seemed fairly stiff as well. I put the bolt in another carrier and it rotated much smoother. I also noticed, under magnification, a small crater type defect on the pin. Not sure if the defect was there before firing initially or not.

Thanks again for taking the time to read and offer guidance.

[LRRPF52]

How would you add the .010?

The Grendel bolt has to be dimensionally correct from the start when made. It is not a hogged-out 5.56 bolt like people think (I used to think this because I read it on the internet over and over.)

Grendel bolts have several critical dimensions that are different than any other bolts, and provide the optimum balance of longevity, a workable extractor with thick enough lip for the cartridge, and compatibility with standard AR15 firing pins.

[LRRPF52]

I took a few measurements this evening.
2.78 Bolt length (maybe a little short)
.136 Face depth
3.26 FP length
.528 Bolt width at belt
.277 avg lug length

Manipulating the bolt inside the BGG seemed fairly stiff as well. I put the bolt in another carrier and it rotated much smoother. I also noticed, under magnification, a small crater type defect on the pin. Not sure if the defect was there before firing initially or not.

Thanks again for taking the time to read and offer guidance.

This is why you are having pierced primers.

I asked another owner of that barrel/bolt combo to measure his bolt length and bolt face depth. His is .136" and 2.8", which is the incorrect combination as well.

Get an AA bolt, a PF, or JP enhanced bolt to go with your barrel. I would put the AA Hard Use bolt at the top of the list.