Home Forums Reloading Big Game Rifles High Pressure in 270WSM?

My Ruger M77 is in 270WSM. First I got pressure spikes with
factory ammo, Winchester 140gr with Accubond bullets. Over
the chronograph it read over 3400FPS and I had to beat the
bolt open. The other four I shot ran in the high 3100fps.
I also found out I have to load that rifle about 2 grains
below max to keep from a stiff bolt. I pulled all the bullets
in the 2 boxes of Winchester shells and reloaded with 1.5gr less. Have not shoot them since. Has Ruger had a problem
with this rifle? I don,t mind shooting it at 270 Winchester
speeds if I can find where to start.

Wsm ammo has been factory loaded to the max and beyond for many years. I've seen over 3100 FPS with 160 grain partitions in my buddies 7wsm Browning BAR...24" barrel w/ Federal ammo.
If you're going to reload for it my advice is to make sure you use a chronograph .....good reloading manuals..... and Buddy up with somebody with quick load to help make forecasts!

Geezus.....and people complain about the 7 Rem Mag....


Seen similar stuff with Federal Premium ammo for the 7mm WSM.

I very much doubt it's the rifle that's the problem.

WSM ammo of any brand seems to be loaded to full pressure, but there are normal tolerance variations that occur in production rifles that can cause high pressure as a result.

I've seen this situation on a number of occasions, with the 270 WSM being a frequent flyer.

So it would be helpful to know if the bullet is engaging the lands, a marker would tell that story. Every rifle is just a little different, so the factory loads may have too much powder for that particular rifle. Perhaps the bore or chamber is slightly tight.

I never run into this in my own rifles, because I don't shoot factory ammo and I work up loads that work well and I have control over the powder charge and OAL.

Who knows what powder the factories use, but the 270 WSM is a step above the 270 Win with a decent powder choice and a good bullet.

270 WSM is a very good round. It runs with the 270 Wby and is probably the best of the short mags. Other than the 270 Wby this is the first 270 mag to become commercially available.

I see on the SAAMI chamber drawing site that Nosler has an approved 27 Nosler chamber. Probably come out next year.

I only shot one box of factory stuff in mine when I first bought and before I had a chronograph, it and the bolt was very stiff after each shot. My handloads with H4831 and 130gr NAB or SST are ~3300 and don't have a stiff bolt. I don't know what the factory pressures are but I'm pretty certain mine are lower.

Yup. With the 7mm WSM I had the same signs plus ejector marks in two rifles, a Kimber Montana and a M70 FW. Ammo was 160 NPT and velocities were over 3250 as I recall.

I emailed Federal. They told me they load the WSM stuff was loaded to 65,000 psi. Maybe in some rifles.....

Mine was fine hand loaded but velocity was not as expected.

GunTruck50,

I have a Vanguard action .270 WSM, that I tried shooting with Federal Vital Shok 140 gr. Accubond ammo (no longer loaded with this bullet, I believe). Velocities were near 3400 fps, with hard bolt lift, extractor marks, etc. Finally, I shot a lot of this ammo which resulted in blown primers.
I promptly gave up on this ammo, pulled all the bullets from my remaining stock, and reloaded them with RL22 and Nosler 130 gr. E-Tip bullets.

With these bullets, I get MV's of 3300 fps, and great accuracy, but none of the high-pressure problems I encountered with the Federal ammo.

More like it.I stopped at 3250 with 130 NPT's and RL25 in my 270 WSM.

I found my Chronograph record today. It was for 6 shots
Winchester WSM factory 140gr. Accubonds.

3112,3087,3144,3091,3130, and 3403fps.

I should mention this was in 2012, right before Elk season.
the rifle had only about 100 rounds thru it, at the time. Still haven,t shoot it much as I bought a Vanguard S2 in 270 Winchester about the same time. I bought my second chronograph about 2 weeks ago, the new MagnetoSpeed Chronographs. I,m working on my Elk loads for the fall trip
to Wyoming. 150gr Nosler Partitions in 270 Win with Norma
MRP, about 58.5gr. and WLR primers are the most accurate load so far. RL26 is faster but I can,t get the accuracy.

I don't shoot a 270 WSM but I thought I'd share this story. Last year my brother and I were finishing up our annual stone sheep hunt. We'd just hiked out of the mountains back to the lake we were dropped off at 2 weeks earlier so we could be picked up the next day. On the ground near our tent I found a once fired federal 270 WSM case with some very high pressure signs. No primer and big extrusion. When I got home a new primer drops in and out with no resistance and the extrusion measures roughly .005" with my verniers.

Hope tne guy who shot that didn't need to make a fast follow up shot!

Ya I'm pretty sure it took some pounding to get that action open, one side of the extrusion is wiped pretty hard. Possibly there was something in the barrel when he pulled the trigger, it seems kind of extreme for a factory load tight chamber situation. I'm assuming its a 1x fired factory round, the brass is other wise pristine.

That's the kind of crap that happens when ammo is redlined and one little factor changes.....kapow.

Chasing that last 100 fps sacrifices reliability, in factory or hand loads.

Factory stuff that I just looked at is rated at 3300 fps and 3143 ft. lbs.

One of my favorite loads is 130gr Barnes with 58grs of IMR4350 behind it. That is one full grain north of the starting load from Hodgdon's. I'm getting speeds just shy of 3000fps.

My other is 130gr HotCor with 57.5grns of IMR4350. That is 0.5grns below the starting load. Why go below? I live and shoot in hot temps and I'm still just shy of 3000fps and 2500fp of energy.

What is important to me is...
Is the round safe?
Is it accurate?
Will it put down the animal I'm hunting humanely?

Yes they are safe; yes they are extremely accurate (between 1,5 and 2"out to 300); and yes if I do my part it will drop a Rocky Mountain Elk or Mule Deer.

HaYen