Even Factory ammo can be over pressure!

[Littlehud]

Years ago I bought a brand new Rem. 700 in 22-250. I took it out to shoot it with factory ammo and nearly blew it up. There was definite signs of over pressure with FLAT primers, and head stamp starting to flatten. I sent the gun back to Remington where they determined the chamber was cut too short, and fixed it. Even after that I could never load higher than slightly over mid range for any given load or I started to flatten primers. Factory loads were out of the question as far as I was concerned. It turned out to be extremely picky for accuracy unless you had the precise recipe for the load, and then it would shoot 1/4" or less. Vary the bullet seating depth by .005" and it went to 6" groups. I finally decided it was too picky and sold it. Yes, I did explain all this to the buyer and he didn't care.

 

[Shortmagman]

The only factory load that I have shot that was too hot was the Winchester 150 gr Silvertips out of my model 70 Winchester Coyote 300 WSM. My chronograph showed over 3300 ft/sec. with that load.
I have just loaded some handloads that were too hot out of my Model 70 Winchester Featherweight in 270 WSM. I loaded some 140 Nosler Accubonds and RL-26 using Alliant data. They list 69+ grains as a max with this bullet. I started 5% below this with my first load of 66 grains and this load was very hot 3250+ ft/sec. I did not shoot my next loads of 67.0 or 68,0. I found a good load with 65.5 grains at 3200 ft/sec.. I think my Norma case have less volume that the Federals in Alliant data and my Bartlein barrel is chambered very tight.

 

[WYO300RUM]

I'll chime in. HSM 140 Berger's in a Cooper Mod. 52 in 6.5x284. flattened primers , ejector mark and heavy bolt lift. I noted they were right up to the lands. I seated some at .020 deeper. Same thing.

 

[jbs2014]

Sorry for a long post, but:
I reload for my brother's custom 338 win. This rifle is built on a model 1917, and has been rebored from the original 30-06 to .338, chambered to 338 win mag and cut rifled in 8 groove. The bolt face is appropriately opened and feed rails modified. This gun was purchased at a local pawn shop so we don't know who did the work. In the process of load development I chronographed Federal 225 gr fusion factory loads. I averaged 2996 for five shots, (including 1 at 3016) and 4 of the five showed primer cratering. Rather than decide that these were really awesome factory load speeds, I came to the conclusion that in this rifle, they were way over pressure. The handload I eventually developed shoots a 225 gr A-Frame at 2750 fps with 64.7 grains of 4955. My thought is just because it's a factory load does not mean that the load is safe in your rifle. Has anyone else experienced unusually high velocities and pressure signs in factory loads, especially in custom barrels?

Yes but not with just a custom barrel.

I ran some Desert Tech Factory .375 Cheytac ammo through the stock HTI barrel and had heavy bolt lift, primer cratering, and ejector swipe in subzero weather.

I also ran some federal .50 BMG ammo through my custom .50 BMG barrel. 1st round had extremely heavy bolt lift. Did not run the rest of the ammo.

With the .50 BMG barrel I think it is a matter of having a short chamber. I now have a Warner Tool custom die that can set back new brass up to .005 less than my fired cases. Have to see if that works. is it possible that your custom barrel may be a bit short?

unfortunately I was not able to chronological either of those loads.

 

[freddiej]

Sorry for a long post, but:
I reload for my brother's custom 338 win. This rifle is built on a model 1917, and has been rebored from the original 30-06 to .338, chambered to 338 win mag and cut rifled in 8 groove. The bolt face is appropriately opened and feed rails modified. This gun was purchased at a local pawn shop so we don't know who did the work. In the process of load development I chronographed Federal 225 gr fusion factory loads. I averaged 2996 for five shots, (including 1 at 3016) and 4 of the five showed primer cratering. Rather than decide that these were really awesome factory load speeds, I came to the conclusion that in this rifle, they were way over pressure. The handload I eventually developed shoots a 225 gr A-Frame at 2750 fps with 64.7 grains of 4955. My thought is just because it's a factory load does not mean that the load is safe in your rifle. Has anyone else experienced unusually high velocities and pressure signs in factory loads, especially in custom barrels?

I have seen factory loads be over pressured in a factory Remington 700 308 Win long range hunter. factory loads would blow primers. nearly impossible bolt lift, (primary extraction cam was working) and starting loads from my new book from Nosler were producing over maximum speeds over the sky screens. the starting loads were also getting flow back from the primers, cutting nice small holes in the primers. I immediately called Remington and let them know. We cast the chamber and found not much except that SAAMI minimum spec was being observed. AKA very tight chamber. eventually the gun was shipped to Remington Arms and it came back with a slightly larger chamber.
Side note. If we down loaded the 308's 1.2 grains under minimum loads we had a one hole gun at 300 yards. this was an extrememly tempermental and very accurate rifle. the only thing wrong is the customer did not want to reload his own. He only bought factory Federal Gold Match ammo.

 

[jbs2014]

I have seen factory loads be over pressured in a factory Remington 700 308 Win long range hunter. factory loads would blow primers. nearly impossible bolt lift, (primary extraction cam was working) and starting loads from my new book from Nosler were producing over maximum speeds over the sky screens. the starting loads were also getting flow back from the primers, cutting nice small holes in the primers. I immediately called Remington and let them know. We cast the chamber and found not much except that SAAMI minimum spec was being observed. AKA very tight chamber. eventually the gun was shipped to Remington Arms and it came back with a slightly larger chamber.
Side note. If we down loaded the 308's 1.2 grains under minimum loads we had a one hole gun at 300 yards. this was an extrememly tempermental and very accurate rifle. the only thing wrong is the customer did not want to reload his own. He only bought factory Federal Gold Match ammo.

Where was the chamber tight at?

 

[ae7v]

Sorry for a long post, but:
I reload for my brother's custom 338 win. This rifle is built on a model 1917, and has been rebored from the original 30-06 to .338, chambered to 338 win mag and cut rifled in 8 groove. The bolt face is appropriately opened and feed rails modified. This gun was purchased at a local pawn shop so we don't know who did the work. In the process of load development I chronographed Federal 225 gr fusion factory loads. I averaged 2996 for five shots, (including 1 at 3016) and 4 of the five showed primer cratering. Rather than decide that these were really awesome factory load speeds, I came to the conclusion that in this rifle, they were way over pressure. The handload I eventually developed shoots a 225 gr A-Frame at 2750 fps with 64.7 grains of 4955. My thought is just because it's a factory load does not mean that the load is safe in your rifle. Has anyone else experienced unusually high velocities and pressure signs in factory loads, especially in custom barrels?

Because of the work done on this rifle the ogive of the fusion bullet is different from the A-frame. So I suspect your throat is very tight hence the pressure problems.

 

[comen]

Because of the work done on this rifle the ogive of the fusion bullet is different from the A-frame. So I suspect your throat is very tight hence the pressure problems.

I agree on the throat! I probably could use fusions if I reseated the factory loads a little deeper. I went to my load book, and I'm actually getting 2770 with the A-Frames. Not a long range setup but a great Elk load within its range. Shoots at 3/4 MOA consistently, with some groups quite a bit smaller