What would make a rifle "slow"?

[hidesert]

I bought my Ruger Model 77 .284 Win new in 1970 and it remains one of my favorite rifles. It probably has around 500 rounds shot through it. Two things about it stand out: it is immensely strong; maximum loads up to the point of flattened primers don't give a heavy bolt lift or any other indication, and it typically produces bullet speeds of 100 fps less than published loads, accounting for differences in barrel length. This has been tested with different chronographs and has been consistent whether using factory load manuals or individuals' published loads. I've held powder, bullet, primer and case constant.

What factors can account for this rifle being slow?

 

[Mikecr]

I'm guessing powder lot.
Flattening primers is not a good indicator of excess pressure, and it sounds to me like you're actually below expected pressure.

 

[hidesert]

Powder lot and or age occurred to me also.

As an example I used Richard Frailey's most accurate load from his comprehensive work "Loading the 284 Winchester for Accuracy" which is 48.0 grains of VihtaVuori N150, WLR primer on a Nosler 140 grain Accubond bullet. He got 2875 fps in an Ultra Light Arms Model 20 with a 22 inch barrel. I got 2756 fps in my Ruger M77 with a 22 inch barrel. I used powder from two lots, one purchased in 2008 and one in 2016. No practical difference. My loads were very accurate and had low ES and SD's.

 

[tbrice23]

I bought my Ruger Model 77 .284 Win new in 1970 and it remains one of my favorite rifles. It probably has around 500 rounds shot through it. Two things about it stand out: it is immensely strong; maximum loads up to the point of flattened primers don't give a heavy bolt lift or any other indication, and it typically produces bullet speeds of 100 fps less than published loads, accounting for differences in barrel length. This has been tested with different chronographs and has been consistent whether using factory load manuals or individuals' published loads. I've held powder, bullet, primer and case constant.

What factors can account for this rifle being slow?

I'll bet $100 your bore is on the loose side (not tight)
#1. Your max load isn't showing hard bolt lift.
#2. Slow velocity compared to listed velocity , list velocities have usually always been slower than my actual velocities.

Loose bore , the bullet encounters less resistance = less pressure, less velocity.

 

[FearNoWind]

First off a safety note. Flattened primers are no absolute indication of high pressure; por the absence of it. When your rifle begins to reveal signs of high pressure you've already passed the safe pressure point long before those signs appear. You can have dangerously high pressure without flattened primers, and flattened primers without dangerously high pressure. Neither does heavy bolt life necessarily indicate high pressure. The age and condition of the brass and other factors come into play when analyzing the source of heavy or stiff bolt lift.
In order to compare your results with published information you need to have exactly the same conditions including rifle specs., ammo specs., environmental specs. and technical equipment. In my experience, using only powder charges as a guide, 50fps increases require about a 1gr increase powder charge. That's a lot of powder. But, also in my experience, the greatest single factor affecting MV is barrel condition and barrel length.
Here's an article worth reading:

http://honors.usf.edu/documents/thesis/u82488180.pdf

 

[gohring3006]

I'm not going to question your ability to read pressure. Sounds like you have been around rifles for a while..
500 rounds?
I have seen barrels speed up around 800ish rounds.

That's amazing 1970 and only 500 rounds.

 

[hidesert]

Yes, 500 rds ain't much but it's mainly a hunting rifle. I shoot my rimfires and revolvers for fun. Lately, though, I've gotten curious about long range shooting.

 

[gohring3006]

How often do you clean it?

 

[hidesert]

Most years I'd take it to the range annually, sight it in with perhaps 20 rounds, clean it and go hunting. My cleaning wasn't very thorough and about 15 years ago I noticed quite a build up of copper. I then used a "Foul Out", the electric rod, which got out the copper. Given the low number of rounds I figured my bore was rough so I used the "FinalFinish" system of firelapping but only using five rounds of each grit instead of ten.

Lately I've been cleaning it after every trip to the range using the practices Ryan Cleckner teaches. My bore cleaner is Shooter's Choice and once in a while some Sweet's.

 

[gohring3006]

Most years I'd take it to the range annually, sight it in with perhaps 20 rounds, clean it and go hunting. My cleaning wasn't very thorough and about 15 years ago I noticed quite a build up of copper. I then used a "Foul Out", the electric rod, which got out the copper. Given the low number of rounds I figured my bore was rough so I used the "FinalFinish" system of firelapping but only using five rounds of each grit instead of ten.

Lately I've been cleaning it after every trip to the range using the practices Ryan Cleckner teaches. My bore cleaner is Shooter's Choice and once in a while some Sweet's.

I'm going to go with tbrice, your bore may be oversized. I personally wouldn't clean it for a 100 rounds or so, as far as removing the copper. Let it foul up
Some and tighten the bore up a little.
Or I would get some Reloader 17 and try it.