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260 pressure issues

R

Remnar

Private
Full Member
Minuteman
Jul 25, 2011
87
12
US
Hello,

This is probably a screw up on my part but I wanted to get some advice on a pressure problem.

I have been loading 41.5 grains of H4350 into Remington brass using CCI primers and 142 SMK bullets. The overall length is 2.847. This was .004 jumped in my chamber. I have shot about 600ish rounds of this load through my Savage with no issues.

I just received my stamp and my suppressor and went out and re-zeroed with the can on. This past weekend I had a 3 day training event and started seeing pressure signs on the empties. I blew out a couple primers and ended up trashing the spring on the ejector. I then was getting ejector marks. I removed the can to see if the added back pressure might be causing the increase. The gun continued to show signs so I rejected the recent batch of 300 reloads. I did have 100 or so left from an earlier loading sesion and they were not showing signs???

What is it that I may have done to cause this batch to have pressure issues when the previous ones had none? I have not pulled any bullets yet to verify the powder drop but I normally check the charge every 20th load?

Any ideas on what I did wrong??

Thanks,
 
Re: 260 pressure issues

First,check your scale.

Second, know that Hodgdon's entire "Extreme" lineup is hotter/faster lately than it used to be.

Still though, 41.5gr is not a stiff charge of H4350 in a 260.
 
Re: 260 pressure issues

I run 43.5gr of H4350 and my father runs 43.8 of H4350. 41.5 seems like a mild load. I am no ballistic genius. You could have somehow loaded them different than the rest? Maybe a little longer of hotter? I am sure someone will chime in here with an answer.
 
Re: 260 pressure issues

Was the brass FL resized ? Also, the 0.004 jump, presume that is from the ogive not the tip of the bullet (just the oal comment)
 
Re: 260 pressure issues

Some general thoughts.
Seating depth, charge changed, POWDER LOT CHANGED, wrong powder.
RTH
 
Re: 260 pressure issues

One thing that may be an issue is heat. Suppressors tend to cause the barrel/chamber to retain more heat. I don't know why exactly but on my rifles it is a fact. My guess is that the hot air inside the suppressor tends to block the flow of the heated air from the chamber while your bolt is open and your cooling. This is just a theory but my barrel cool down times are much greater running a can than when running a brake and the barrel heats up faster. Just cut your loading back slightly and you should be back in business.
 
Re: 260 pressure issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rth1800</div><div class="ubbcode-body">Some general thoughts.
Seating depth, charge changed, POWDER LOT CHANGED, wrong powder.
RTH </div></div>

I did a check on the powder and it was correct

Seating depth is variable I guess as I measure the OAL when checking seating. Edit..adding here that I didn't trim the brass so if it is long it could be causing the bullet to be seated deeper in order to maintain the OAL. (hmmm..is this my issue? case too long?)

I don't think the charge changed as I check every 20 to 25 rounds. I will be pulling bullets and will verify.

Powder lot may well have changed as I usually buy it by the pound so it is more than likely different.

 
Re: 260 pressure issues

I'm having to deal with my latest purchase of Varget powder. It is DEFINITELY hotter than the previous lot I had.
 
Re: 260 pressure issues

Couple suggestions
1 buy H4350 in 8lb jugs, reason is the lot to lot consistency is simply not there.
2 stop throwing your charges, weigh each one, at 100-300 yards thrown charges are fine, at 1000 your SD/ES will be high, even if your doing everything right the spread between shots will create a lot of misses, and your confidence will suffer.
3 Rem brass is fine for 5-6 loads, but because its soft the pockets open up and blown primers happen, the increased back pressure from the can may excellerate that.
 
Re: 260 pressure issues

I run the exact same components, similar OAL and jump but a charge of 43.5 gr. Have almost 4k rounds through the gun and I don't get any pressure until I get to about 44.5gr. That load combo should be mild, start at the beginning and make sure that charge is what you think it is, a fluctuation in the powder lot could be some of it but in my experience usually 50fps is the maximum change. Let us know what you find out.
 
Re: 260 pressure issues

If you are checking your load col by measuring the metplat(tip) of the bullet they can be .004 different. This would put some touching the lands and some not. This will cause pressure signs as well as a can making the load slightly hotter.
 
Re: 260 pressure issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fred Seaman</div><div class="ubbcode-body">Have you checked your case length. </div></div>

This. Are they a bit more difficult to chamber? If the neck is too long, when you chamber it, the bullet can basically be "crimped" in the case. Also, throw a few loads and weight them on a good scale.
 
Re: 260 pressure issues

Remnar

I don't have an answer or help for you but I can relate since I recently experienced a similar problem. I had almost the same issue 2 weeks ago at a match. I shoot the same rifle/caliber (minus the can) as you and have used the below load for a few hundred rounds with no issues.

Lap brass
H4350 44.2 gr
BR2 primer
142 SMF
2.845 OAL .020 jum to lands

1st relay started at 0900. I set up on the bench and shot two 10 shot strings with no issue. I shot the second relay with the same gun/ammo. Time was about 1000 and the sun was out. Near the end of the 1st string I started to get stiff bolt lift but the brass looked okay. Shot the second string and the 4th and 5th shot blew the primers. 5th shot broke my ejector and I stopped shooting. Should have stopped sooner.

When I load my ammo I weigh each charge twice before I dump it in the case and all were spot on. When I got home I pulled the bullets and weighed the powder and they were all good to go.

In the past I classified myself as a "picker" when I shoot. Using all the time alloted during the relay and to try to pick the right wind condition to shoot in. During this match I changed my strategy since the wind kicked my butt during the previous months match (all 600 yds). I shot each string fast as I wanted to get rounds off before the wing changed. I live and shoot in Western Wshington. The temps when I started shooting were in the mid 50s. When the primers blew the temps were in the mid 60s. The only real change for me this time was my gun heating up more with the rounds being fired faster.

I called Savage and they sent me a new ejector, ejector spring and retaining pin. When I broke down the bolt, the ejector was broken and the spring was collapsed.

The 44.2 gr load shot .3 for me when the conditions were right and I did my part. That load moved along at 2900 fps and I was very happy with it. 41.9 gr is another accuracy load for me but I only get 2660 FPS out of it. I will shot this lighter load at the next 600 yd match and see how well it fairs in the wind.

I know this didn't help your cause but it let's you know you aren't alone on this.

Jet
 
Re: 260 pressure issues

I have the same rifle. I noticed severe pressure signs with 41gr of h4350 after I resized my brass. I discovered I was oversizing it. I bought a gauge to allow me to measure shoulder bump and haven't had a problem since. Just a thought
 
Re: 260 pressure issues

Pressure is pressure. I too have blown primers with the .260.

It was not from any single cause. I was running a marginally over max load, and the temp was up at least 20 degrees F above where that load was developed.

We tried keeping the ammo in a cooler, but that blew the primers even more frequently.

The cooler was chilling the ammo, which then picked up condensation before it could be chambered and fired. The moisture/water in the chamber appeared to have compounded the pressure peaks. Once we realized that, we wiped down each cartridge before chambering it, and the issue disappeared.

My point here is not about either temperature or condensation, but about how things creep in out of left field to plague us.

Underlying all of this is the simple fact that loading in the max/fast lane leaves you wide open to unanticipated issues. Stay out of that lane, and things like this should never occur.

I keep telling folks there is no great advantage to running hot loads. This is one of the many reasons why such is so.

Greg
 
Re: 260 pressure issues

I run H4350 in my 6.5Creedmoor at 41.0gr with a 139gr Lapua Scenar. Last year when developing loads I ran out of powder and kind of had to start over. I had previously went as high as 42.0gr with my prior lot of H4350. My very first shot with the new powder at 42gr recoiled harder and completely stretched the primer pocket to the point that I can just drop a primer into the case and it is loose. I normally buy 8lb jugs but ran out and could only buy a 1 pound jug locally. That pound of powder was way hotter than my previous lot of H4350. Lot number was <span style="font-weight: bold">10627114939</span>. Check that against yours.
 
Re: 260 pressure issues

I thought H4350 was one of Hodgdon's Extreme line of powders that aren't as sensitive to temperature. From the sounds of these experiences, temperature is a factor.
 
Re: 260 pressure issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">Pressure is pressure. Underlying all of this is the simple fact that loading in the max/fast lane leaves you wide open to unanticipated issues. Stay out of that lane, and things like this should never occur.

I keep telling folks there is no great advantage to running hot loads. This is one of the many reasons why such is so.

Greg </div></div>



The load data I had showed that 41 was the low and 45 was the high. I didn't think I would have an issue with pressure at the low end.

I managed to get some time tonight to hit the loading bench. I pulled several bullets and measured case length, powder weight, and COAL.

The case length averaged 2.032 and my refference shows the max case to be 2.035. I measured some "one shot" brass and it was 2.023. Based on this I don't think case trimming is the complete answer. However it may well be a part of the problem. What length do you all normally trim to?

COAL measurements were all very close with none measuring long enough to actually jam the bullet.

Powder does show a bit of the problem. I measured about 25 random loads and found that i was running about 41.8 on average. I did find a couple at 42. I am going to need to be a little more carefull when changing powder lots. I'm also going to increase my test weights during loading.

The data from the bullet pulling has me a bit freaked out. I was hoping I had made a complete boneheaded mistake that caused the problem. Now that there doesn't appear to be a clear issue I am a little scared to run the next batch. I am at a loss as to what to try as far as charge and trim length.

I will be checking to make sure I have the chamber neck cleaned. I have been giving it some brushing but I am going to up the amount of time spent on it.

Going to start buying larger powder qty to avoid changing lots as much as possible.

Thanks to everyone for all the help and advise so far.

Remnar
 
Re: 260 pressure issues

I had similar issues with 4350. I chased my tail for a month and finally decided it was temperature related. Loads that showed no signs of pressure at 40 - 50°F were way too hot at 90°F.

It also appeared that the powder might heat up enough to change properties just by sitting in a hot chamber for a minute or so. I wasn't able to confirm that, but that's how it appeared.
 
Re: 260 pressure issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Remnar</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rth1800</div><div class="ubbcode-body">Some general thoughts.
Seating depth, charge changed, POWDER LOT CHANGED, wrong powder.
RTH </div></div>

I did a check on the powder and it was correct

Seating depth is variable I guess as I measure the OAL when checking seating. Edit..adding here that I didn't trim the brass so if it is long it could be causing the bullet to be seated deeper in order to maintain the OAL. (hmmm..is this my issue? case too long?)

I don't think the charge changed as I check every 20 to 25 rounds. I will be pulling bullets and will verify.

Powder lot may well have changed as I usually buy it by the pound so it is more than likely different.

</div></div>
Me and a buddy both run a good bit more then that and both of us just bought powder recently. I load 43gr of H4350 in my .260 and my buddy runs 43.7gr so I dont see it being the powder if your only running 41 gr. I cant see it being that much hotter. If your convinced it is the powder you should pick up another 1 lb of it somewhere and try that batch i guess.
 
Re: 260 pressure issues

I don't think temperature was the issue as I have been shooting the load all summer with no issues. The weekend I had problems we were in the 50's with rain and hail.

Going to chamber some of the empties after marking them up with a sharpie to see if I am hitting the chamber.

I also see that the suggested trim measurement for the 260 is 2.025. My average was higher than that at about 2.032. Going to trim back to that. Change my loading to 41 grains and check each with the scale. Verify that I am not having a case length problem by chambering the marked up empties.

Hopefully that will get me back to a workable load.
 
Re: 260 pressure issues

I run 43.4 of h4350 with Nosler 140gr. Very slight pressure signs, but all within reason.
 
Re: 260 pressure issues

I run 43.8 grains of H4350 in a 27 inch Obermeyer 5R barrel. Winchester 7mm-08 cases necked down, CCI BR2 primers, 140 grain Sierra MK seated 2.3 inches to the ogive. Velocity is 2888 FPS, and absoutely no pressure signs. Bolt life is smooth, primers still have a rounded corner on them, no extractor/ejector swipe marks, and primer pockets are tight after 4-5 loadings.

I would check the following:

1. make sure it is the correct powder, that you didn't grab the wrong can
2. powder measure, and powder scale
3. throat of your rifle to insure you aren't jamming the bullet into the lands
4. check the velocity over a chrono
5. check headspace of the rifle
6. check how far you are setting the shoulder back when you resize

If you set the shoulder back too far, it has the same effect as having a rifle with too long of headspace. This can make the primers flatten, and dramatically shorten case life.
 
Re: 260 pressure issues

I have been doing more reading and I am wondering if my issue may be that i am only neck sizing my reloads. I have seen some reports from people having pressure issues due to this.

I coated some empties with sharpie ink and chambered them to see if I was hitting the chamber. I am getting a scratch where the shoulder meets the body of the brass. I am thinking I might need to FL resize to push back the shoulder. Anyone have another suggestion?

Thanks,
 
Re: 260 pressure issues

You're going to have to bump that shoulder back every few loadings. Neck sizing every time doesn't work. Get a tool to measure headspace. Full-length size and fire, measure headspace. Then neck size for the next few loadings, measure headspace every time, and when you get above your first measurement, it's time to bump that shoulder back .001 or .002".
 
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