REM 7 1/2 for Lapua 6.5CM?

[SlowMiss6.5]

Hey All,

First post but long time reader. Getting into PRS after trying a match with my hunting rifle. Long story short I found a crazy deal on a new Seekins HIT rifle so went that route because I can sell it for more if I end up wanting to upgrade in the future

To keep my hunting rifle brass and comp brass separate I got some Lapua 6.5 SRP (hunting uses LRP). Also went that route because there a lot of SRPs locally. Well come to find out I need mag srp to avoid cratering. Locally they have CCI 400, WSR, REM 6 1/2 and REM 7 1/2

Shooting conditions will be between 30-95 degrees ambient throughout the comp year. Load will likely be around 41.5 H4350 with a 140 or 147 grain eldm (if 147 then load will be down about a grain likely)

Long story short: Do you think the REM 7 1/2s will work well? Would it be wise to buy up a 1000 or so of these rem 7 1/2s or maybe not so many because I could see some issues?

 

[SlowMiss6.5]

Meant to also include, didn’t plan on having anything done to the Seekins fire pin which I’m assuming is setup for LRPs

 

[SlowMiss6.5]

Can anybody confirm the rem 7 1/2s will be a good setup for the SRP Lapua brass?

 

[spife7980]

The rem7.5srp (or cci 450/br4) is the better choice over the rem6.5srp or cci400s but puncturing small rifle primers is going to primarily be a function of your firing pin diameter and hole fitment.

Ive got no idea what the seekins hit firing pin diameter is but if you get your calipers out it should hopefully be below ~.070 in diameter, if its more then you are much more prone to poking holes in the thin cup material at high pressures because the span it has to hold up over is further than the material can support.

Watch the first minute and a half for a demonstration

 

[Xcount]

Can anybody confirm the rem 7 1/2s will be a good setup for the SRP Lapua brass?

Yes, the R7.5 will be good. It's a magnum primer cup.

 

[SlowMiss6.5]

The rem7.5srp (or cci 450/br4) is the better choice over the rem6.5srp or cci400s but puncturing small rifle primers is going to primarily be a function of your firing pin diameter and hole fitment.

Ive got no idea what the seekins hit firing pin diameter is but if you get your calipers out it should hopefully be below ~.070 in diameter, if its more then you are much more prone to poking holes in the thin cup material at high pressures because the span it has to hold up over is further than the material can support.

Watch the first minute and a half for a demonstration

Appreciate the info and the video. Called Seekins and they measured one they had in had to be .067”. I will measure mine once I get it but the customer rep said the firing pin is the same for all their HIT rifles.

Sounds like I may be good to go by hopefully running the rem 7 1/2s. I will pick up a brick which should keep me busy all through this year (I’m expecting component “shortage” later this year)

 

[DHDeal]

Yes on the Rem 7 1/2.

You'll know right quick about the firing pin hole. My Surgeon action showed me a real nice tit on the first 6×47L round fired. Off to Gre-Tan it went. Other than a possible wait time and $$ there is no downside. The measurement Seekins gave you may be fine though.

 

[SlowMiss6.5]

Yes on the Rem 7 1/2.

You'll know right quick about the firing pin hole. My Surgeon action showed me a real nice tit on the first 6×47L round fired. Off to Gre-Tan it went. Other than a possible wait time and $$ there is no downside. The measurement Seekins gave you may be fine though.

Just a little lost, nice tit meaning it pierced the primer? Just trying to understand what I should be watching for

 

[M_R_Woodard]

Remington 7.5 primer in a 700 6.5x47. The one on the left was before getting my bolt bushed.

 

[SLAYIN'SWEDE]

I've ran 7 1/2's exclusively in my 6.5 Lapua SRP brass and they've been great.

 

[SlowMiss6.5]

I've ran 7 1/2's exclusively in my 6.5 Lapua SRP brass and they've been great.

Is your firing pin modified at all?

 

[SlowMiss6.5]

Remington 7.5 primer in a 700 6.5x47. The one on the left was before getting my bolt bushed.
View attachment 8367763

Thanks for the info. So essentially if I’m seeing primer cratering at a below max load, that’s a good indicator that I need to get the bolt bushed?

 

[SLAYIN'SWEDE]

Is your firing pin modified at all?

No it isn't, but cratering is very minimal with hot loads

 

[M_R_Woodard]

Thanks for the info. So essentially if I’m seeing primer cratering at a below max load, that’s a good indicator that I need to get the bolt bushed?

Yes, but I don't think you will have an issue. My problem was the sloppy fit of a factory Remington firing pin. I shot 3000 rounds that looked just like the left round before I sent my bolt off. The 7.5 primers are tough.

 

[45-90]

Yep Rem 7.5 should be great, I run them in hot 6 Dasher loads, and 65,000 psi 454 Casull loads, 308, and 6.5 CM.
Rem 7.5, CCI 450, CCI BR 4, & mil spec CCI 41, ...have thicker .025" cups. The others are thinner cups don't use them.

My 6.5 CM firing pin is .080" and it works just fine with any of the above heavy cup SR primers. I'm running 150SMK at 2832 fps with BR 4s in current load, but Rem 7.5 works just as well.

 

[DHDeal]

Just a little lost, nice tit meaning it pierced the primer? Just trying to understand what I should be watching for

The primer flowed back into the firing pin hole. Looked like what I described it as. I had already used Gre-Tan for at least one other bolt for the same reason (Remington Model 7 with a 6.5×47L barrel) and honestly I figured I would need to bush the Surgeon bolt from the start. I seem to remember I sent in 3 other bolts to be bushed with the Surgeon. No downside besides the time and money.

The ×47L brass seems to want a small firing pin and I suspect any SRP .473" casehead brass will benefit. I reformed some Palma brass to 6.5 Creedmoor (before Lapua made SRP Creedmoor brass) but never had an issue as that particular bolt had already been bushed.

If you have a .067" diameter firing pin I would try it first. I doubt you'll have any issues there.