HIGH PRESSURE SIGNS LOW VELOCITY

[STW]

I am loading for a friends 300 RUM. I am consisitently experiencing stiff bolt lift, ejector marks and low velocity readings. Using Retumbo and RL25 with various Nosler, Hornady and Barnes bullets. The loads are at the bottom of the Nosler manual for the various weights. The 2 other 300 ultra mags I load for can reach top velocites with a few grains less powder than what the manuals call for. This rifle shoots OK but velocities are almost 200 fps shy of the other rifles and loading manuals. Just wondering if anyone has seen these type of symptoms before.?

 

[kraky]

Actual loads and velocity readings would be extremely helpful here!
How much freebore in the offending gun vrs's the others?

 

[Ridge_Runner]

check case capacity of H20 in that rifle compared to the others, would it be possible your under pressure? loaded on the lands will do it also but not likely in a RUM.
cut or buttoned barrel? standard or fast twist? just some of the things that have affected vel. and pressure for me.
RR

 

[STW]

Here are a couple of the loads Remington once fired case resized and trimmed,
Federal 215M primer
91.5 grains RL25
180 gr Nosler AccuBond
COAL 3.60''
velocity 3075 avreage

Hornady 180 grain SST
95 grains Retumbo
COAL 3.60''
3088 fps average

Chronograph has been checked against another and with several rifles.
I am unsure how far off the lands we are. All 3 RUMS are of the same manufacture. Same twist.

 

[kraky]

A quick look at quickload seems to be very close to those velocities and seems to think they might be running in the 58-64k pressure range. It seems weird that you are getting that much high pressure feedback.
I might tend to look at how much freebore the chamber has and possibly how fouled the barrel might be.
Couple years ago I loaded some 300 wby for a guy who had a custom barrel w/o normal wby freebore.
I started 3 grains under what I've used in many factory wby's and promptly proceeded to blow primers.
Likewise I've gone to the range w/my 30378 w retumbo loads that started just fine. As the barrel fouled I saw velocity jump quite a bit. Retumbo can be pretty spike as you near Max.

 

[Ridgerunner665]

Is the rifle in question a Remington?

I've had this same issue (different round)....It was the barrel....rough as a corn cob.

 

[Guy Miner]

Makes a fellow wonder if hand lapping or fire lapping the bore would be worthwhile.

Before I started in on that though, I'd measure the freebore, and look at the barrel with a bore-scope. Most Remington rifles I've worked with have a LOT of "free bore" built into them.

That 180 gr load appears rather mild for a .300 RUM, and shouldn't be giving you any problems at all.

Guy

 

[kraky]

When quickload looks at things it doesnt take freebore into account......so....if there is freebore those loads should be quite mild. I believe the secret to the problem is lurking "within"!

 

[STW]

I checked the freebore and there is plenty.

 

[STW]

No the rifle is not a Remington.

 

[kraky]

Anyone in your area have a borescope?

 

[OU812]

Here are a couple of the loads Remington once fired case resized and trimmed,
Federal 215M primer
91.5 grains RL25
180 gr Nosler AccuBond
COAL 3.60''
velocity 3075 avreage

Hornady 180 grain SST
95 grains Retumbo
COAL 3.60''
3088 fps average

Chronograph has been checked against another and with several rifles.
I am unsure how far off the lands we are. All 3 RUMS are of the same manufacture. Same twist.

According to the Nosler 6 book you are at min charge weights for both powders and 180 gr bullets. The new online manual has the charge weights you are running as max loads, I'm guessing it's a misprint for the on line as I am running 94 gr Retumbo with a 200 AccuBond at 3200 fps.

Here is something I encountered with Remington brass and an 8mm mag that mirrors what you are seeing. I worked up a load for my 8mm using RL-22, 220 hornady bullets new Remington brass check for min length, fed 215 primers all of the components were of their respective same lot numbers that shot amazing with great velocity.

I ran out of the new brass of that bag and lot number and got into my next bag, different lot number but all other components were the exact same as before. Headed to the range to shoot and the first round shot as normal, extracted as normal, primer look as normal. 2nd round did the same. The 3rd round however would not extract, had to use a squib rod to knock the brass out of the chamber, primer was very flat. This made no sense to me. Loaded a 4th round and it shot as normal and extracted as normal. 2 rounds later it did it again and I had to knock the brass out of the chamber.

I quit for the day and went back home to pondered what seemingly random event was taking place. I ended up weighing the brass that I had just fired ( I kept them in order in which they were fired) and found that the cases I had issues with were considerably lighter in weight than the brass I has no issues with.

I then weighed all my new brass and found a hand full more of the lighter weight brass. I loaded 3 of the lighter weight pieces and 3 heavier pieces of brass (majority of the brass was heavier in weight and all close to the same weight) and went back to the range. Sure enough the heavier weight brass shot, extracted and looked as normal and like before the lighter weight brass (only shot 1 of the 3 rounds) hung up and had to be knocked out of the chamber.

You might try weighing your brass and posting the weights on here. I can weigh some of my brass which is working flawless and compare weights. Maybe you got a bad batch of lighter weight brass. Remington won't give you the weight specs of their brass, I tried because of the issue I had.

 

[STW]

Interesting I put brass which came from the batch giving issues on my scale and weighed in at 268 grains.
More Remington brass from a different batch came in at 278 grains.These were not shot in the rifle which is the cause of this post.
I thought I might as weigh some Nosler brass just to compare and they came in at 284 grains.

 

[STW]

Kraky, I am probably several hours away from a bore scope.

 

[OU812]

Interesting I put brass which came from the batch giving issues on my scale and weighed in at 268 grains.
More Remington brass from a different batch came in at 278 grains.These were not shot in the rifle which is the cause of this post.
I thought I might as weigh some Nosler brass just to compare and they came in at 284 grains.

I'll weigh some of my 300 rum brass tomorrow and post results. If it were me I would try some of the heavier brass with the same load and see what they act. That just might fix your issue. If it does then you can weigh all your brass and find the lightest stuff and heaviest and some where in between you will find the cut off point of working Ok and not. Keep us posted.

 

[OU812]

My brass weighs between 268-270ish so maybe that is not the cause of your issue but it sure caused me headaches at one time.

 

[STW]

I picked up a box of factory Remington power level III ammo of 180 grain Scirroco.
Went out at 6am this morning to the range and shot.
Velocities were 3302-3356-3360. No stiff bolt lift, no pressure signs on the case at all. Now I am going to try and find some new brass of any manufacture and start over with load development.
Could it be that one could have a crappy batch of brass?

 

[DrMike]

Could it be that one could have a crappy batch of brass?

That is always a possibility; it has happened before. Any component can potentially be out of spec.

 

[kraky]

It would sure appear you've gotten a solid conclusion. That was smart and a good reminder to get some factory ammo and use it as a "thermometer".

 

[OU812]

I picked up a box of factory Remington power level III ammo of 180 grain Scirroco.
Went out at 6am this morning to the range and shot.
Velocities were 3302-3356-3360. No stiff bolt lift, no pressure signs on the case at all. Now I am going to try and find some new brass of any manufacture and start over with load development.
Could it be that one could have a crappy batch of brass?

It happened to me once, knock on wood. Until you find some brass you could load up some tests with the brass you just fired since it worked fine and see what your results are. Wouldn't take many to either duplicate the issue or have it eliminated.

One other thing to keep in mind is that BOTH of the loads you listed are according to Nosler # 6 starting loads.