7ss +p not producing

[slim23]

had a 7 sherman short that wasn't producing the velocities i had hoped. 22" 180 berger 2800 with rl26. 2780 h1000 and 7828. i sent it to unknown munitions for a +p throat hoping to get to 2900. Took it out yesterday with same load of rl26. same speed and being 30deg warmer slight pressure signs. Thinking of trying v565. Anyone else have experience with +p?
Ran borescope down it before and after machining and no burrs or anything that looks suspect to add pressure. Barrel is clean.

 

[wind gypsy]

What barrel is it and how many rounds are on it?

 

[slim23]

Proof with 220rds

 

[wind gypsy]

I've no experience with 7SS but I have had a couple long throated 22" 7 SAUMs that i feel comfortable pushing 30-50 FPS faster than the #'s you posted with those powders. That said, the SAUM has slightly more case capacity than the SS and I wouldn't be surprised if mine have more freebore too (right around 0.200" IIRC). A little more capacity + a little more freebore = more velocity at the same pressures. Maybe not 30-50 but could easily see half or more of that and the barrel could be the other variance.

No clue on the +P portion of this, never been around them.

What are seeing for pressure signs that tells you those speeds are max? I know there was some issues with Reamer/brass/die conflicts with some sherman cartridges.

 

[WeiserBucks]

Welcome to the wide, wide world of Sherman wildcats! As usual they won't send a given bullet at magic velocity as described.

If you can shoot a 180 at 2800 safety out of a 22" with good accuracy I'd be satisfied and enjoy the rifle.

 

[slim23]

Flat slightly flowing primers on a custom action and very slight ejector mark on some. I have multiple friends getting 2900 out of saums and 2800 was on slow side for this. Done the +p to try to gain what I hoped for from a slow barrel. For all unknown munitions praise I’m not seeing it yet.
The rifle shoots very well consistently. Just not as fast as I’d hoped.
I’ve worn out many barrels on 6 and few on 6.5 stuff but this one is fighting me

 

[wind gypsy]

Primer flow has been more action/primer specific than pressure specific for me but it seems like you're confident that the bolt/firing pin fitment isn't the cause here? I'm guessing these guys that push the shermans hard and say they "hold pressure better" than whatever the parent cartridge is don't let a little primer flow slow them down. Mild ejector marks aren't uncommon on ADG SAUM brass to get the velocities I mentioned.

 

[slim23]

I guess my biggest complaint is the +P throat that unknown munitions is promoting so hard did not give even close to the results i was hoping. Literally no change.
From the tens of thousands of rounds I've done in custom actions that have tight firing pin holes, when they are flowing back hard and corners are flat its hot! lapua will hide a lot of pressure! but this adg is clearly not that hard. I have lived by the mantra of if lapua doesn't make brass for it don't shoot it!
Only reason i went sherman was brass avability. But there only one making decent saum brass too...

Shooting in cool conditions most of the time and running them on the edge of hot with a little flow and slight ejector marks i know its as hot as it needs to be. Granted i run 300 norma spicy but it shoots amazing there and lapua hides it well.

My chamber is deffinetly on the large side. I was getting a lip on top of shoulder after sizing in hornady dies. Still not sure if that's a reamer design problem or gunsmith problem? Sent 3 pcs of brass to whidden to have custom dies made that are actually on there way back now. I love wildcats but this thing has been a bear. especially for a "standardized" wildcat.
Figure ill run this thing out and go to a 7prc next year after brass becomes available. Always need another new gun!

 

[Muledeerfanatic]

I had a 6.5 ss
It wasn't that exciting either

 

[PathFinder]

My first +P chamber just shipped today so I can't claim experience, but my understanding is that equal loads will produce lower velocity. You'll have to call it based on pressure signs but the general rule is it will take a couple grains more to hit pressure again and find the velocity gains with the +P chamber.

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[slim23]

That was my understanding also. But I’m seeing equal pressure with the same load and same speed as before. Going to try v565 being slightly slower to see if that helps

 

[Ryan Avery]

I guess my biggest complaint is the +P throat that unknown munitions is promoting so hard did not give even close to the results i was hoping. Literally no change.
From the tens of thousands of rounds I've done in custom actions that have tight firing pin holes, when they are flowing back hard and corners are flat its hot! lapua will hide a lot of pressure! but this adg is clearly not that hard. I have lived by the mantra of if lapua doesn't make brass for it don't shoot it!
Only reason i went sherman was brass avability. But there only one making decent saum brass too...

Shooting in cool conditions most of the time and running them on the edge of hot with a little flow and slight ejector marks i know its as hot as it needs to be. Granted i run 300 norma spicy but it shoots amazing there and lapua hides it well.

My chamber is deffinetly on the large side. I was getting a lip on top of shoulder after sizing in hornady dies. Still not sure if that's a reamer design problem or gunsmith problem? Sent 3 pcs of brass to whidden to have custom dies made that are actually on there way back now. I love wildcats but this thing has been a bear. especially for a "standardized" wildcat.
Figure ill run this thing out and go to a 7prc next year after brass becomes available. Always need another new gun!

I’ve owned or help load for around 30ish +Ped rifles. All of them dropped pressure and shot slower after with their standard load. All took 3-5 grains more powder to see pressure. The lowest velocity gain I have seen from a +P treatment is 80 FPS and that was also on a Sherman. It’s very weird that you see pressure with the old load. Maybe the Sherman’s already have some kind of throat treatment??


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[Nbowlin]

Just a thought.........Have you tried a powder in the rl23, 560 or 555 range? Or even RL17or H4350? All The throats improved in that fashion I have dealt with have produced as they should.

 

[archer8524]

I have a 300 prc +p that Shawn carlock did for me the first load I tried was 210 Bergers and RL 26. I hit pressure way before “book” max powder charges. It shot great and was getting 3100fps but with way less powder. I then switched to a different bullet and retumbo and it shot slower then book max charges. I’ve heard that RL 26 can do some weird things so I would definitely try some different powders before calling it a loss.


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[slim23]

Shot it with h1000 and n565. Gained 100fps with h1000 over where I was with original load work up. If I remember correctly it was 4 more gr. Overall I ended up at 2898. 70fps faster than I was with rl26.
I hadn’t tried 565 originally but a friend had a partial pound and ended up at 2820 before primers were flat. I expected to run out of capacity before it pressured out. But that was a full case load as it was.
I’ll stick with h1000 and run this barrel out and hope for lapua 7prc brass next year.

 

[Idmtgoat]

I’m having a 7prc+p done by Shawn right now. Hopefully it works good

 

[B23]

I’m having a 7prc+p done by Shawn right now. Hopefully it works good

How long is the barrel on your 7 PRC and what bullet powder combo do you plan to use?

Shawn built me a 7mm Blaser mag a few years ago and it is a near twin to the 7 PRC. Mine wears a 26in Hart barrel and Shawn +P'd the throat. With 68.5gr RL26, 215M, and 180 Berger Hunting VLD it runs those 180's 3088-3100. It'll push them over 3100 fairly easily but that 68.5gr load shoots extremely well for me.

I don't know what bullet/powder combo you're going to shoot but with 180's, RL26 and a 26in pipe you should be somewhere in that 3050-3100 ball park with a +P'd 7PRC.

 

[Idmtgoat]

My plan is to use 180 bergers for sure. I love to try 26 but I have a short supply and another fun addicted to it.. I actually got 8lbs of staball hd in hopes it’s going to get me in the 3000ish range. It’s a 22” hells canyon armory barrel.