Home Forums Hunting & Shooting Ask The Gunwriters Higher pressure than normal factory ammo

Hi, I purchased 5 boxes of Rem CoreLokt 175g 7mm Rem Magnum ammunition new for $35 box. I bought them to check out a new to me BDL in 7mm Mag and for the cases. I'm shooting 3/4" groups or a little better with it at 100 yards. All good so far. It chronographed at just over 3000 fps (factory ammo is usually in my experience slower the advertised) and occassionally the bolt is hard to open. If these were my handloads I would drop the powder charge by 2 grains. Rifle's sighted in, accuracy is great. My plan is to handload some 175g A-Frames for it. Should i pull the bullets on the rest and keep the cases? I only have about 30 rounds left.

Thanks

That is very fast! Especially for that load, I have never seen them break much over 2850 in about any rifle I tried them in. If It were me, I'd pull em down since you wanna make some handloads anyhow. Worst case, you know they shoot fine, so maybe keep one box in reserve in case you run short of time doing load work.

Thanks!

Might notify Remington. They’d probably want them for pressure testing. Also be sure your chronograph hasn’t gone wonky.

Weigh the powder..................................
If possible post a pic.
Good chance its alliant, as they are owned by the same corp

I'd be contacting Remington. I wouldn't hunt with ammunition if it was hard to open the bolt after firing, even if that only happened occasionally, no matter how accurate. That is a recipe for problems.

so you shot 70 rounds of the ammo ?

Yup over two days and it was 60 degrees yesterday so it wasn't hot out I'll probably pull the remaining bullets and just use the cases. I just couldn't believe factory ammo would have pressures that high. I'll order some 175g A-Frames and start working up a load.

Are those boxes of ammo recent production?
I've been shooting 7mm rem mags since about '64.
A couple of years ago I came across a partial box of 175gr. Remington factory loads from about 1965 and decided to chrono a few to see what the older ammo would do
I got an average of 3021 fps in my rifle (Iirc) for 5 shots. Bolt lift was normal and no signs of excess pressure.
Newer ammo has never chrono'd more than about 2830 ish from that rifle.

Have written about this before, but here goes:

The 7mm Remington Magnum was introduced in 1962. The original advertised muzzle velocity for the 175-grain factory load was 3020 fps.

During the next decade or so, the Sporting Arms and Ammunition Manufacturers Institute (SAAMI) moved away from the copper-crusher pressure-testing equipment that had been standard to piezo-electronic testing--which was more sensitive. It was discovered that the 7mm Remington Magnum often exhibited wider variations in pressure, both high and low, than many other cartridges, and since SAAMI was concerned with the higher-pressure variations, they reduced the Maximum Average Pressure (MAP) somewhat.

This resulted in the standard listed muzzle velocity of 175-grain ammo being reduced to 2860 fps. At that time SAAMI used 26" barrels for most rifle testing, but since most factory 7mm Remington Magnums have 24" barrels velocity was somewhat less.

(Every time this general subject comes up, several people comment that they've never "noticed" wider variations in pressure in 7mm Remington Magnums. But every pressure-lab I've ever visited, whether in a bullet/powder company or an ammo factory, has documented it, especially with certain bullet powder combinations.)

Hi Mule Deer, I remember in the early 70s Remington 175g ammo being advertised at 3000 fps. I checked this ammo, it says 2860 fps, so it's not really old ammo.

The only pressure issue I've had with factory ammo was over 20 years go, in AZ. Also Remington core-lokt, but in 308. I felt gas on my face and had to pound the bolt open with a block of wood. It was 104 degrees out, which probably had something to do with it...

In the late 70’s, after SAAMI reduced the pressure data MD mentioned, the Remington literature reduced their advertised muzzle velocities for the 7RM, then reduced advertised velocities again in the early 80’s.

3000fps with 175g is way fast and almost certainly over pressure.

Yeah I'm gonna pull the bullets on the remaining 30 rounds. I aspire to reach 3000 fps with 175g A-Frames, but I will work up slowly as always and won't get anywhere near the pressure of these factory rounds. I'm pretty surprised.

3,000 fps with 175 gr bullets is way fast with a 24" barrel. Why go that high?

About 20 years ago my wife and I were at the range and she was shooting her 7mm08 with Remington 140 grain Core-Lokt PSP ammo. One of the rounds was significantly over pressure and it locked up the bolt. The bolt had to be pounded open, but luckily no one was hurt, and the over pressure round didn't appear to do any permanent damage to the rifle.

Another example of Remington factory ammo that somehow got loaded too hot.

You're probably right, I'll work my way up and see where I get the best accuracy between 2800 fps and 3000 fps.

7mm Remington Magnums are known for unexpected pressure spikes.

Casey,

I just checked my collection of Gun Digest annuals, which is complete to at least 2000. In the 1980 edition's list of factory ammo the 175-grain Remington load was still listed at 3070 fps, but in the 1985 edition it's 2860, so apparently the big change happened somewhere in there.

John

70 of them in a row apparently for this one.

John,
You are correct. I was thinking of the 150g Corelokt. I have the Remington brochures in that period, and it was the 150g that was reduced in the late 70’s and again in the early 80’s.

One load tested in one rifle. Both of uncertain history. No question about the rifle?

I'd look forward to seeing results with new handloads. How do velocities stack up with book charge values?

You might consider shelving your 30 remaining cartridges for later study.
Ken

Maybe some of that pesky chemical bonding is involved? Pull ‘em, for certain.

I once bought 100 rounds of Wolf “Match” .308. Only fired a couple as I ran into hard lift as you described with a Kimber Longmaster. They reimbursed me fully without question, so they either knew they had an issue, or were just being very cautious.

Good point I will go buy one box of Federal 7mm ammo and try that. I usually only shoot my own reloads but typically buy a box of factory with a new or "new to me" rifle. I'll also measure the OAL, i wonder if the bullet is jammed against the lands in the factory ammo. I don't think it's the rifle because of the velocities I'm getting and it's shooting close to .5 MOA. Too bad about the pressure, 3000 fps with a 175g bullet and sub MOA could've talked me out of reloading for this rifle!

I have had pressure signs with more than a few boxes of Weatherby ammo.

Hey, colorado Reloader 23 is your friend if you can find any. Other than that stock up on Ramshot Magnum.

41

The SAAMI spec throat for the 7mm Rem Mag is very poorly done.

Remington (old) did not cut SAAMI spec throats in either the 7mm Rem Mag or another SAAMI problem child the .243 Win. I assume Mike Walker was the guy who fixed the factory Remington chambers for those cartridges.

SAMMI spec chambers (short freebore with abrupt leades) used for pressure testing are going to show the issues of such poor throat design.

The OP's ammo is hot because even in a decent freebore/leade throat 3000fps with a 175gr bullets is pushing on the yield strenght of brass. Probably safe enough to shoot but Remington brass is not the hardest of brass.


Good to see you post, Ken.

John,

Yep, have encountered all that in many factory rifles in both 7mm PM and .243 Winchester. In fact was told by the head of the ballistic-testing department at one of the MAJOR ammuntion companies during a 2-day visit of their facilities that the .243 has also long been a major problem-child....

John

I bought 10 boxes of Norma 340 Wby ammo. Loaded with 250 grain Woodleigh roundnose bullets. 3210 fos avg from my 340. Bolt opens with 2 fingers. Rifle is a Sako Finnbear with Bofors barrel; 12 groove.
Crazy stuff happens

Thanks for all of the advice. I'm coming to the conclusion that the bullets are seated out too far for my rifle and are jammed against the lands. I will put this to the test at the range. I plan to blacken with soot one of the bullets and chamber it to see if that's the case. I also plan to seat the bullets in about 10 rounds 1/10" deeper.

Just use a felt tip marker. I would be a little leery of smoking a loaded round. 🔥

Good idea lol.

I'll make it to the range this week. I'm pretty sure the factory ammo is seated out too far and is jammed againt the lands. If that's the case, I'll seat them all 1/10" deeper.