Throat length, Pressure,& MV

[budlight]

wingman - I went through this years ago and ended up using a .300 inch throated barrel. Pressure signs went down chrono speeds stayed the same. My .277 win AI case uses a very compressed load. It takes a tall drop tube to get all the powder in the case nearly level to the top before seating the bullet.

I also went slower powder than R-22 to IMR 7828 and CCI250 primers.

A few years back I started moly coating all my bullets and they were just about across the board a 50 fps drop in speed and even less pressure.

[BountyHunter]

wingmagman

1. RL 22 has a well documented history for lot to lot variations. you could have very fast lot. there were several pulled from the market two years ago.

2. Bullets will vary on base to ogive. For example sierra 142s are .080 longer than JLK 140s in this area.

3. Same bullets will vary as much as .20 from lot to lot with the same mftr. Always measure.

3. You never mentioned what MV you are getting with that load. If it is 2950 or up, you are probably at the limit anyway depending on barrel length.

4. Read up on the ladder method of load tuning (here on the board) and find the best load for your barrel, bullet and powder combo.

BH

[LDHunter]

FiftyDriver,

"Stick powders tend to erode throats faster then ball powders on average because they are more physically abrasive and they tend to burn a little hotter then ball powders."

You sure on this? Both Hodgdon and Accurate Arms techs have told me the reverse. According to them ball burns hotter and subjects throats to more erosion.

I don't claim to know from first hand experience. The throats I've burned were all subjected to "stick" powders only.

$bob$

[lynn]

Winmagman
You need the boattail to bearing surface length 0.050 in front of the neck shoulder junction in your cases to reach both peak accuracy and muzzle velocity.Seat a bullet to this setting and measure your overall length then chamber the round and measure your overall length on the same bullet.This will tell you how much longer your throat needs to be cut.By chasing the throat you'll never get good accuracy or velocity out of your existing barrel.
Lynn

[winmagman]

Thanks for the input.
I've been working with this rifle for a little while now and it shoots the 140 gr SMKs into the .2 to .4 range with a MV of 2980 (avg) and an ES of 16 (10 shots).

I also tried the 140 gr SST in hopes of finding a high BC hunting bullet. Unfortunatly the rifle didn't seem to like them. I tried Imr 4831, H 1000, and Re 22 with MVs between 2800-3000 rarely did I get a group under .75 inches.

So when deer season opens this Thur. I'll be shooting the MKs. Mainly cause I'm fond of hitting what I aim at.
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