Futher 338 AM testing

[Shawn Carlock]

Shot Jr's 338 AM today to do some more testing and get good chronograph readings. Shot fire formed loads with 145.0 grains of H50BMG, 300 gr. SMK's, CCI 250's, OAL 4.140" OAL. Chronographed 9 rounds, had 1 odd reading the other 8 rounds had an ES of 11 fps!!! Average speed was 3335 fps. @ 18'. Temp 24 degrees, humidity 32%, BAR 26.8, elevation 2208'.
Shot groups @ 400 yards and didn't seem to do any better than 1.5" most ran 2.0" or so. I believe the round and rifle are capable of much more based on 100 yard performances and the tight ES. I would be disappointed if we don't see 1"@ 400 yds sometime soon. I expect to see some great things from this round. Hope to shoot some post worthy groups soon.

 

[steelhead]

Sounds promising Shawn. Thanks for keeping up informed!

 

[davewilson]

have any of you put more than 300 rounds out of your 338AM's? reason i ask is the firecracking should be present by then and was wondering if the 300SMK's will take the speeds you're getting with them.i've heard from a reliable source that they will dust at 3275 if a barrel is rough.when it's new you can shoot them faster.

 

[Fiftydriver]

Dave,

I was told many times that the 1-10 would dust the 300 gr SMK right from the start if I pushed velocity much over 3400 fps, even out of a new barrel and this was from someone that was using the 338 on the big 408 case and had been for some time. Made me a little nervous at first but I have never seen that to be the case with the Lilja. It may well be with other barrel makes, I can not say to that point as I have only used Liljas so far.

I probably have just shy of 300 rounds down Black Sunshine including some fireforming, some 350 gr ULD RBBT loads and mostly 300 gr SMKs. About half of these 300 gr SMK loads were well over 3400 fps and some were pushing 3500 fps for the sake of experimenting to see what the big girl would do at top end pressures.

In the end I have settled back to a load that produces 3380 fps in warm temps. In cooler weather, this is such a reduced load that I get hangfires frequently. This was however with US869 and because of this I am thinking about switching back to H-50BMG for an all around powder for the 338 AM.

One of these days I will have to get the bore scope out and check out my throat, I am sure there will be some heat cracking starting up but we are burning around 145 gr of powder per shot.

Please keep in mind, I was testing the hell out of my new round which is why the round count is up there and also we were pounding chucks for a good part of the summer. This not the recommended use of the round at least not for high volume. It was not hard to drop 40 rounds down the barrel in each outing just shooting out to 3000 yards busting rocks.

Normal use for a 338 AM would generally not be this much, certainly not with a lighterweight 338 AM and as such it would more then likely take several years to get 300 rounds down the barrel.

Simple answer to your question, we will have to see. So far, every bullet is hitting the mark as expected but time will tell.

One high note, I hear from a good source that the Wildcat 338 Bullets are coming back on line slowly and those jackets are much thicker then the Sierras in the bullet body area so this should help prevent any bullet failure we may see.

If the start coming apart, we will chalk it up to experience and order in a 1-11 twist or similiar but until then I have no reason to go away from my preferred Lilja barrels even I hope to order in a Lawton barrel for testing here as well.

There are some new bullets coming soon for testing, 325 gr ULD RBBT and 375 gr ULD RBBT so we will see what happens.

Kirby Allen(50)

 

[Black Diamond 408]

Dave,
My personal 338 snipe-tac rifle has more than 300 rounds down the bbl. Groups at 100yds are still under .200 1000 yd groups are .6 MOA I have seen no evidence of bullet failure. I shoot my rifle at a average speed of 3350.
It doesn't seem to make much difference on twist rates, 9.4 up to 11.5 just depends on how heavy of bullet your going to shoot. 11" - 11.5" twist all bullets up to and including 300grn. 250grn and heavier 10" down to 9.4" This is from actual testing on various barrels.

Dave

 

[new shooter]

Kirby and Dave, so what do you think the barrel life would be on the 338-408? and also what would the barrel life on the 338 edge be? I know you don't have a cystal ball but from your own experience what is your reasonable guess when the accuracy would start to fall off? Thanks alot.

 

[Black Diamond 408]

New shooter,

With out the crystal ball, i estimate 1000 rounds plus. Most of the hotrod 338's start to show some decline around the 1000-1200 round. This ofcourse is only a small decline in accuracy, for target purposes you would see the barrel being replaced sooner, for hunting purposes the barrel would last much longer. You have to ask yourself at what point are you not comfortable with certain group sizes, MOA at 1000yds per say. In my mind once the barrel is producing groups over 1.5 MOA @ 1000yds it may be time for replacement. Another factor is having the barrel set back and re-chambered to freshen up the throat.

This is not a high volume rifle, it is a special purpose long range round and intended for such. My personal rifle is 4 years old and has a bit over 300 rounds through it. The barrel has been on three different test actions along the way.

I believe the 338 Lapua has about a 1500 round life expectantcy. I assume the 338 RUM and others would fall close. There are other factors that need to be discussed, barrel quality, shooting habits and cleaning. The carbon wrapped barrels (ABS) are suposed to have double the barrel life over a standard barrel due to the rapid cooling effects.

It would be up to interpertation as to how many rounds, each individual will have different ideas as to when accuracy is not desirable.

If you push the round to the fullest i assume the life will be shorter. I start my customers off at 140grns of H-BMG50 with the 300MK bullet, this produces around 3250fps. I personally use WC 872 in my rifle, 145grns gets me 3350 ave.

Its a big gun designed for heavy duty work, long range with retained energy.

Dave

 

[Fiftydriver]

New Shooter,

IF you take care of your barrel and be careful not to overheat it I would predict a useful long range big game hunting life in the 1000-1200 round range with the 338 AM.

It you run her to 70,000 PSI you will obviously get more throat erosion quicker but if you load to lower pressures and still let the barrel overheat with quick shooting you will do the same damage so no matter what you do you have to take care of the bore.

If I could get some bugs worked out with the forward ignition design I have been working on, I would suspect barrel life would be more like 1500-1800 rounds but I have to get it working properly before I can say.

In testing done before forward ignition has DRAMATICALLY increased bore life. That is down the road a bit though.

Kirby Allen(50)

 

[davewilson]

i was just talking about the barrel getting rougher due to the heat cracking and it's affects on bullets. not the twist.