About at my wits end with my 270

[Thebear_78]

I had a fast twist 270 build that was finished this summer. I originally shot it with some nosler BT ammo. It was fairly accurate, showed promise but nothing special.

One weird thing was there was a pronounced ring around the base of the cartridge. The ring looked almost like it was cut into the cartridge, but was only on the inside of the cartridge. I was also getting ejector marks and swipes on the case head. Classic over pressure signs.

I took it back to my smith and checked headspace, even pulled the barrel to look for what might be leaving the ring on the brass. Everything checked out. He suggested shooting a couple boxes of cheap factory annoying, that it might break in.

I picked up two boxes of PPU factory 150 SP loads. The PPU brass looked fine, no rings, accuracy wasn't great, almost poor.

I loaded up some loads with the 150 LRAB and 165 matrix VLD. Using virgin nosler brass. I started with mid loads working up by 1/2gr increments. Right off the bat I was getting pressure signs, and the ring was back.

I thought it might have something to do with nosler brass so I picked up 100 virgin Winchester brass. I also went to re22 since the 7977 wasn't in the nosler book. Started out with 54.5gr using 3.34" COL.
I didn't get any pressure signs but instead of the 2800fps I was expecting it was clocking in at 3050-3070fps. Considering this was well above expected I stopped. Going to have to lower my charge weight I guess.

I'm not sure what to think about this thing! I'm going to give it one more try starting at minimum and try again.


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[69gto]

I have loaded at least 6 270's with rl 22 over the years and have never been able to get any pressure signs like that. Up to 64g with 130's and 59g with 150 partitions, this was with Winchester brass which has a higher capacity than other brands. It almost looks like that ring is a crack. If you are getting 3050fps with only 54.5g of rl22 you must have a really tight chamber. My 24inch barrel 270 gets 2950 with 58g. Maybe someone who builds custom rifles will chime in and have a solution.

 

[preacher]

Just guessing...if your chamber was cut with an older, more worn reamer, the base could be very tight and yet your "headspace" would still check out with go/No go tools. then, if you have to size them down with your FL die to get "easy chambering" ( like a hunting rifle should have) you are most likely shoving that shoulder back pretty far. "To me", Uncle Bear", that 'ring" looks like insipient head separation.? The next thing I would try is to use a SB sizing die. Good luck to you Pard!

 

[IdahoCTD]

It looks like case head separation to me also but I would guess because the headspace is off. It looks like the brass is being sized too far and having to spring back out again. What I would do is neck a new case up to 30 caliber and then back down to .270 but only enough to where it will go in the chamber. Fire the case and then measure and compare it to one that you sized after shooting and a brand new unfired case. Another possible cause is the back of the chamber is too large and the brass is having to blow out too far. How hard is it to size the brass after the first firing? If you look at the picture of the Winchester case you can see a noticeable bulge where the case gets thin. That would indicate a difference between the chamber and virgin brass or a difference between the sizing die and the chamber. The more pressure the more pronounced it becomes because the brass springs back less the more stress that is applied to it.

Honestly my 300wsm does that to a degree also but it's because the reamer spec compared to the sizing dies is too far apart IMO. The base of the reamer is cut about .008" over virgin brass and the sizing dies sizes the cases .004" under chamber diameter. The brass hasn't failed yet but it's not good for the brass to have to move that much and it takes a lot of effort to size the brass that much. I'll either send the reamer back and have the base reduced about .002" or have a custom sizing die made so it doesn't work the brass so hard.

 

[elkeater2]

I think the other guys are steering you right. Even so, it reminds me of an episode I had with an Ohaus scale that between some lint and operator error started throwing heavy charges by a couple grains. My bad for sure but it had me fooled for a while. The velocity you got with the Win brass and 54.5 gr RL22 makes me wonder about the charge weight. Please tell us what you find out.
EE2

 

[Thebear_78]

I'll pull one and verify using my balance scale


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[Thebear_78]

I'll pull one and verify using my balance scale


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[Anonymous]

I have to wonder about your charge weights... 3050 with a 150 grain bullet is getting up there considering a .270WBY is only rated 3150...

That just seems hot and the brass shows it to be the case.

My .270 shoots 150s about 2800 with some change.

 

[HAWKEYESATX]

I have to agree with the above.
Your cases are Showing excessive pressure, and are about to split at the area just right before the case gets thicker.
I would check your data to ensure It's correct.
Re-check the powder, make sure it's the right powder, and if it is, back off on the charge weight.
It also looks like the case isn't completely enclosed in the chamber. Is the head of the cartridge being fully supported? Or enclosed with the bolt head against the barrel?
Whatever the problem, it's a good thing it hasn't detonated at this point.

HawkeyeSATX a.k.a. Bryce

 

[HAWKEYESATX]

Also, this may sound silly, but are you sure your barrel is the nominal .277 caliber for that barrel?
I had an inexperienced buddy once that bought a Remington 700 BDL in .270 Winchester back in the early 90's, and he wasn't familiar with which ammo to use. He inadvertently bought .280 Remington ammo, loaded it in his magazine, chambered it, I don't know how, with no problems, and proceeded to shoot 4 rounds of .280 out of his .270!
How it didn't blow up is still a miracle to me!
On the last shot, he had a hard time lifting the bolt. I saw the cases, and just about feinted!
Your cases look exactly like his did.
Just an observation.
But I would check everything out.
You never know if someone mislabeled a .264 cal barrel for .277.

HawkeyeSATX a.k.a. Bryce

 

[69gto]

That is an interesting observation Bryce, it would explain why he is getting that speed with such a light load of RL22., and excessive pressure.

 

[gerry]

I was wondering the other day how your 270 was doing, sad to hear it is being a problem for you. It does sound like there is something seriously wrong with either the chamber or bore or both, hope you get it figured out since a fast twist 270 would be a very useful gun to have.

 

[Thebear_78]

I'm thinking about sending it to another smith. Just having them pull the barrel and rechamber it. The only downside is it has been nitrided and any metal work will break the seal and leave an avenue for moisture to get at the metal.


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[HAWKEYESATX]

That is an interesting observation Bryce, it would explain why he is getting that speed with such a light load of RL22., and excessive pressure.

I'm just wondering if the bore isn't a .264 cal.
That would explain a lot.
Maybe it's a little bigger than .264, but still smaller than .277.
I think that's what the problem is.
Or the rate of twist way too fast for that .277 bullet.

HawkeyeSATX a.k.a. Bryce

 

[gerry]

That is an interesting observation Bryce, it would explain why he is getting that speed with such a light load of RL22., and excessive pressure.

I'm just wondering if the bore isn't a .264 cal.
That would explain a lot.
Maybe it's a little bigger than .264, but still smaller than .277.
I think that's what the problem is.
Or the rate of twist way too fast for that .277 bullet.

HawkeyeSATX a.k.a. Bryce

I have a 1 in 9 twist 270 Win and haven't noticed any problems, can't imagine a 1 in 8 being much different when it comes to pressure. Some of the 7mm's have pretty tight twists and it hasn't been an issue, the 223 is a prime example with lots of 1 in 12's out there and now 1 in 8 twists without any real issues it would appear. Must be something else,

 

[HAWKEYESATX]

Then it has to be too tight of a bore. It would explain excessive pressure and higher than normal velocity for your charge.

HawkeyeSATX a.k.a. Bryce

 

[Thebear_78]

Measured it with calipers, you really need pins to get an accurate measurement but it was .270". Which is about right for lands.


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[HAWKEYESATX]

What throat length is it? Maybe its way too short?

HawkeyeSATX a.k.a. Bryce

 

[BF375]

Is this a button rifled barrel?

The OP checked headspace but what about throat length?

I doubt the twist has anything to do with it.

 

[Thebear_78]

I think I'm just gonna cut my losses on this rifle. I'm starting to have real negative feelings about it anyway. I don't feel like getting in a pissing match with my smith about it and don't want to send it to another smith and paying another 350 dollars to have it rechambered. I'm just gonna pull the barrel and sell it as components.

It's too bad it should have been a sweet rifle.


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