DPMS 260 pierced primer - bolt bushing?

[lte82]

I found a really nice node for my DPMS 260, which is in the 2980-3000 fps range with the 123 smk, but I'm getting cratered primers. I was using Rem 9 1/2s which are probably not as hard as the BR2's or magnum primers, but the more I read about it last night, it seems like the firing pin hole is a little too large.

Has anyone successfully resized their semi-auto firing pin hole to .062-.068? Is armalite STILL the only one that makes a bolt with the small hole?

 

[Kiba]

What barrel length? Even with a 24" barrel that load sounds on the hot side for a semi auto, 2900-2925 fps would probably be much easier on primers especially with the large .080 firing pin.

I'm not sure who out there can do firing pin bushing for an AR bolt, but I'd love to see someone like JP make a DPMS pattern bolt with a .068" firing pin hole and a matching .068" firing pin...

 

[ORD]

There are "fixes" in the works for the larger, 0.080" DPMS LR-308 firing pin that would essentially resolve a large part of the cratering/piercing problems, but it is likely still a ways out. You might check in with Hide member LRRPF52 and see if he can offer any assistance/info in the meantime: http://www.snipershide.com/shooting/members/lrrpf52.html

I have not seen anyone offering firing pin hole bushings for the DPMS bolts yet, but it is certainly possible with the right tools/equipment/time/money.

 

[lte82]

What barrel length? Even with a 24" barrel that load sounds on the hot side for a semi auto, 2900-2925 fps would probably be much easier on primers especially with the large .080 firing pin.

I'm not sure who out there can do firing pin bushing for an AR bolt, but I'd love to see someone like JP make a DPMS pattern bolt with a .068" firing pin hole and a matching .068" firing pin...

24". I've got a .5-.6 MOA node in the 2750-2780 range, and it looks like a sub .5 moa node in the 2980-3000 fps range. Out of those nodes, I'm seeing fliers and groups pushing 1+ moa. I'd rather not back off this load if possible.

 

[lte82]

There are "fixes" in the works for the larger, 0.080" DPMS LR-308 firing pin that would essentially resolve a large part of the cratering/piercing problems, but it is likely still a ways out. You might check in with Hide member LRRPF52 and see if he can offer any assistance/info in the meantime: http://www.snipershide.com/shooting/members/lrrpf52.html

I have not seen anyone offering firing pin hole bushings for the DPMS bolts yet, but it is certainly possible with the right tools/equipment/time/money.

Thanks for the info. I sent him a PM.

 

[Kiba]

24". I've got a .5-.6 MOA node in the 2750-2780 range, and it looks like a sub .5 moa node in the 2980-3000 fps range. Out of those nodes, I'm seeing fliers and groups pushing 1+ moa. I'd rather not back off this load if possible.

Understandable, I wouldn't want to back down to 2750-2780 either. Even with a 24" barrel 2980-3000 with 123s is a pretty stout load in a semi auto but at least you wouldn't be having cratering & piercing issues with a .068" firing pin. Brass life might not be the greatest though.

It's been suggested to me to try Wolf LRM or Wolf 7.62 NATO primers to help with the .080" DPMS firing pin in non-308 rifles but I haven't been able to find either of those primers in almost a year.

 

[LRRPF52]

I have been sent a very promising drop-in fix for this issue for those of us with .080" firing pin holes, and it has already showed noticeable improvement (used to pierce and crater, now primers look great) in a 6.5x47 Lapua LR with DPMS BCG, and that cartridge is SAAMI rated higher pressure than the .260 Rem (60,000psi Maximum Average Pressure).

I'll post updates once I'm able to start testing it, hopefully soon. My Grendel gets a lot more trigger time because I haven't been able to find any H4350, H4831SC, or RL17, which are favorites in the .260 Rem. I still have a lot of H4350, and some RL17, but I'm not so excited about burning it up, whereas I have been able to find 8lb jugs of CFE for the Grendel, and my buddy scored me 14lbs of N530 for the G as well.

Anyway, I will take the .260 Rem out soon and load some of the H4350 and RL17 loads that are good on book values, are stable on the chrono, but showed signs where I think the pin hole is more of the culprit than the actual load. I use Rem 9 1/2's mostly.

I have had great external ballistics with:

* 130gr VLD (my top pick)
* 139gr Scenar (shot .6" with my 1st load in development, 5rds, then got smaller and smaller)
* 142gr SMK
* 140gr Match Burner
* 123gr Scenar
* 130gr Norma GT

Chamber was cut and all barrel work, assembly, test-firing etc. done by GA Precision, specifically throated for VLD's run from mag length.

 

[waveslayer]

I have been sent a very promising drop-in fix for this issue for those of us with .080" firing pin holes, and it has already showed noticeable improvement (used to pierce and crater, now primers look great) in a 6.5x47 Lapua LR with DPMS BCG, and that cartridge is SAAMI rated higher pressure than the .260 Rem (60,000psi Maximum Average Pressure).

I'll post updates once I'm able to start testing it, hopefully soon. My Grendel gets a lot more trigger time because I haven't been able to find any H4350, H4831SC, or RL17, which are favorites in the .260 Rem. I still have a lot of H4350, and some RL17, but I'm not so excited about burning it up, whereas I have been able to find 8lb jugs of CFE for the Grendel, and my buddy scored me 14lbs of N530 for the G as well.

Anyway, I will take the .260 Rem out soon and load some of the H4350 and RL17 loads that are good on book values, are stable on the chrono, but showed signs where I think the pin hole is more of the culprit than the actual load. I use Rem 9 1/2's mostly.

I have had great external ballistics with:

* 130gr VLD (my top pick)
* 139gr Scenar (shot .6" with my 1st load in development, 5rds, then got smaller and smaller)
* 142gr SMK
* 140gr Match Burner
* 123gr Scenar
* 130gr Norma GT

Chamber was cut and all barrel work, assembly, test-firing etc. done by GA Precision, specifically throated for VLD's run from mag length.

PM me. I found a bunch of 4831 powder.

 

[black max]

I have been sent a very promising drop-in fix for this issue for those of us with .080" firing pin holes, and it has already showed noticeable improvement (used to pierce and crater, now primers look great) in a 6.5x47 Lapua LR with DPMS BCG, and that cartridge is SAAMI rated higher pressure than the .260 Rem (60,000psi Maximum Average Pressure).

I'll post updates once I'm able to start testing it, hopefully soon. My Grendel gets a lot more trigger time because I haven't been able to find any H4350, H4831SC, or RL17, which are favorites in the .260 Rem. I still have a lot of H4350, and some RL17, but I'm not so excited about burning it up, whereas I have been able to find 8lb jugs of CFE for the Grendel, and my buddy scored me 14lbs of N530 for the G as well.

Anyway, I will take the .260 Rem out soon and load some of the H4350 and RL17 loads that are good on book values, are stable on the chrono, but showed signs where I think the pin hole is more of the culprit than the actual load. I use Rem 9 1/2's mostly.

I have had great external ballistics with:

* 130gr VLD (my top pick)
* 139gr Scenar (shot .6" with my 1st load in development, 5rds, then got smaller and smaller)
* 142gr SMK
* 140gr Match Burner
* 123gr Scenar
* 130gr Norma GT

Chamber was cut and all barrel work, assembly, test-firing etc. done by GA Precision, specifically throated for VLD's run from mag length.

Care to share the "drop in fix" you received? I'm having the same issues in my custom 6.5cm ar...

 

[Casey Simpson]

My "drop-in" fix is an Armalite bolt, carrier, pin and

DPMS barrel extension. Works. And works flawlessly. Head spaces correctly, shoots accurately, reliable. Runs like a sewing machine.

ORD is right to feel we shouldn't do it.

I do shit all the time I'm not supposed to do. Its how I find solutions.

Scott Madesha bushed a DPMS bolt for me, but the pin tip kept breaking. It'll work if you can profile the pin tip to hold up. Like the Armalite pin maybe??

Another solution might be to load ammo with CCI #41 primer designed for AR's. CCI Ammunition - Primer Details

 

[BCP]

Cratered primers are not a problem per se it's just cosmetic. Tons of factory rifles do it. Now a pierced primer, or primers blowing out, is a whole other topic.

 

[Casey Simpson]

Cratering in auto-loaders will affect ejection. Think. Part of the primer is sticking into the firing pin hole in the bolt face. that adversely affects smooth cycling.

Cratering in autos is a no go.